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Sample records for chromium removable partial

  1. Additive Manufacturing: A Novel Method for Fabricating Cobalt-Chromium Removable Partial Denture Frameworks.

    Science.gov (United States)

    Alifui-Segbaya, Frank; Williams, Robert John; George, Roy

    2017-06-01

    Additive manufacturing (AM) often referred to as 3D printing (3DP) has shown promise of being significantly viable in the construction of cobalt-chromium removable partial denture (RPD) frameworks. The current paper seeks to discuss AM technologies (photopolymerization processes and selective laser melting) and review their scope. The review also discusses the clinical relevance of cobalt-chromium RPD frameworks. All relevant publications in English over the last 10 years, when the first 3D-printed RPD framework was reported, are examined. The review notes that AM offers significant benefits in terms of speed of the manufacturing processes however cost and other aspects of current technologies remain a hindrance. Copyright© 2017 Dennis Barber Ltd.

  2. Effect of storage time and framework design on the accuracy of maxillary cobalt-chromium cast removable partial dentures

    Science.gov (United States)

    Viswambaran, M.; Sundaram, R. K.

    2015-01-01

    Statement of Problem: Inaccuracies in the fit of palatal major connectors may be related to distortion of the wax pattern due to prolonged storage time and faulty major connector design. Purpose: This in vitro study was carried out to find out the effect of storage time and major connector design on the accuracy of cobalt-chromium cast removable partial dentures (RPDs). Materials and Methods: A brass metal die with a Kennedy Class III, modification 1, the partially edentulous arch was used as a master die. Thirty-six refractory casts were fabricated from the master die. The refractory casts were divided into three groups (Group I: Anterior-posterior palatal bar, Group II: Palatal strap and Group III: Palatal plate) based on the design of maxillary major connector and subdivided into four groups (sub Group A: 01 h, sub Group B: 03 h, Sub Group C: 06 h, and sub Group D: 24 h) based on the storage time. For each group, 12 frameworks were fabricated. The influence of wax pattern storage time and the accuracy of the fit palatal major connector designs on the master die were compared. Casting defects (nodules/incompleteness) of the frameworks were also evaluated before finishing and polishing. Repeated measures analysis of variance was used to analyze the data. Results: The gap discrepancy was least in sub Group A (01 h) followed by sub Group B (03 h) and C (06 h) and most in sub Group D (24 h). Statistically significant differences (P < 0.05 in all locations L1–L5) in the fit of the framework were related to the design of the major connector. The gap discrepancy was least in Group I (anterior-posterior palatal bar) followed by Group II (palatal strap) and most in Group II (palatal plate). Conclusions: It is recommended that the wax patterns for RPD to be invested immediately on completion of the wax procedure. The selection of a major connector design is crucial for an accurate fit of RPD. PMID:26681850

  3. Effect of storage time and framework design on the accuracy of maxillary cobalt-chromium cast removable partial dentures

    Directory of Open Access Journals (Sweden)

    M Viswambaran

    2015-01-01

    Full Text Available Statement of Problem: Inaccuracies in the fit of palatal major connectors may be related to distortion of the wax pattern due to prolonged storage time and faulty major connector design. Purpose: This in vitro study was carried out to find out the effect of storage time and major connector design on the accuracy of cobalt-chromium cast removable partial dentures (RPDs. Materials and Methods: A brass metal die with a Kennedy Class III, modification 1, the partially edentulous arch was used as a master die. Thirty-six refractory casts were fabricated from the master die. The refractory casts were divided into three groups (Group I: Anterior-posterior palatal bar, Group II: Palatal strap and Group III: Palatal plate based on the design of maxillary major connector and subdivided into four groups (sub Group A: 01 h, sub Group B: 03 h, Sub Group C: 06 h, and sub Group D: 24 h based on the storage time. For each group, 12 frameworks were fabricated. The influence of wax pattern storage time and the accuracy of the fit palatal major connector designs on the master die were compared. Casting defects (nodules/incompleteness of the frameworks were also evaluated before finishing and polishing. Repeated measures analysis of variance was used to analyze the data. Results: The gap discrepancy was least in sub Group A (01 h followed by sub Group B (03 h and C (06 h and most in sub Group D (24 h. Statistically significant differences (P < 0.05 in all locations L1–L5 in the fit of the framework were related to the design of the major connector. The gap discrepancy was least in Group I (anterior-posterior palatal bar followed by Group II (palatal strap and most in Group II (palatal plate. Conclusions: It is recommended that the wax patterns for RPD to be invested immediately on completion of the wax procedure. The selection of a major connector design is crucial for an accurate fit of RPD.

  4. Quality of communication and master impressions for the fabrication of cobalt chromium removable partial dentures in general dental practice in England, Ireland and Wales in 2009.

    Science.gov (United States)

    Kilfeather, G P; Lynch, C D; Sloan, A J; Youngson, C C

    2010-04-01

    The aim of this study was to investigate the quality of communication and master impressions for the fabrication of cobalt chromium removable partial dentures (RPDs) in general dental practice in England, Ireland and Wales in 2009. Two hundred and ten questionnaires were distributed to 21 laboratories throughout England, Ireland and Wales. Information was collected regarding the quality of written communication and selection of master impression techniques for cobalt chromium partial dentures in general dental practice. One hundred and forty-four questionnaires were returned (response rate = 68%). Alginate was the most popular impression material being used in 58% of cases (n = 84), while plastic stock trays were the most popular impression tray, being used in 31% of cases (n = 44). Twenty-four per cent (n = 35) of impressions were not adequately disinfected. Opposing casts were provided in 81% of cases (n = 116). Written instructions were described as being 'clear' in 31% of cases (n = 44). In 54% of cases (n = 76), the technician was asked to design the RPD. Based on the findings of this study, written communication for cobalt chromium RPDs by general dental practitioners is inadequate. This finding is in breach of relevant contemporary legal and ethical guidance. There are also concerns in relation to the fabrication process for this form of prosthesis, particularly, in relation to consideration of occlusal schemes.

  5. Successful removable partial dentures.

    Science.gov (United States)

    Lynch, Christopher D

    2012-03-01

    Removable partial dentures (RPDs) remain a mainstay of prosthodontic care for partially dentate patients. Appropriately designed, they can restore masticatory efficiency, improve aesthetics and speech, and help secure overall oral health. However, challenges remain in providing such treatments, including maintaining adequate plaque control, achieving adequate retention, and facilitating patient tolerance. The aim of this paper is to review the successful provision of RPDs. Removable partial dentures are a successful form of treatment for replacing missing teeth, and can be successfully provided with appropriate design and fabrication concepts in mind.

  6. REMOVAL OF HEXAVALENT CHROMIUM FROM DRINKING WATER

    Directory of Open Access Journals (Sweden)

    A. R. Asgari ، F. Vaezi ، S. Nasseri ، O. Dördelmann ، A. H. Mahvi ، E. Dehghani Fard

    2008-10-01

    Full Text Available Removal of chromium can be accomplished by various methods but none of them is cost-effective in meeting drinking water standards. For this study, granular ferric hydroxide was used as adsorbent for removal of hexavalent chromium. Besides, the effects of changing contact time, pH and concentrations of competitive anions were determined for different amounts of granular ferric hydroxide. It was found that granular ferric hydroxide has a high capacity for adsorption of hexavalent chromium from water at pH≤7 and in 90 min contact time. Maximum adsorption capacity was determined to be 0.788 mg Cr+6/g granular ferric hydroxide. Although relatively good adsorption of sulfate and chloride had been specified in this study, the interfering effects of these two anions had not been detected in concentrations of 200 and 400 mg/L. The absorbability of hexavalent chromium by granular ferric hydroxide could be expressed by Freundlich isotherm with R2>0.968. However, the disadvantage was that the iron concentration in water was increased by the granular ferric hydroxide. Nevertheless, granular ferric hydroxide is a promising adsorbent for chromium removal, even in the presence of other interfering compounds, because granular ferric hydroxide treatment can easily be accomplished and removal of excess iron is a simple practice for conventional water treatment plants. Thus, this method could be regarded as a safe and convenient solution to the problem of chromium-polluted water resources.

  7. REMOVAL OF HEXAVALENT CHROMIUM FROM AQUEOUS ...

    African Journals Online (AJOL)

    a

    In this study, removal of chromium(VI) from aqueous solutions by Palmyra palm fruit seed carbon. (PPFSC) and commercial ... have studied the feasibility of less expensive materials such as alginate beads [15], wheat straw. [16], carbon develop from ... Arecaceae) is a largely populated tree in south India. EXPERIMENTAL.

  8. Unilateral removable partial dentures.

    Science.gov (United States)

    Goodall, W A; Greer, A C; Martin, N

    2017-01-27

    Removable partial dentures (RPDs) are widely used to replace missing teeth in order to restore both function and aesthetics for the partially dentate patient. Conventional RPD design is frequently bilateral and consists of a major connector that bridges both sides of the arch. Some patients cannot and will not tolerate such an extensive appliance. For these patients, bridgework may not be a predictable option and it is not always possible to provide implant-retained restorations. This article presents unilateral RPDs as a potential treatment modality for such patients and explores indications and contraindications for their use, including factors relating to patient history, clinical presentation and patient wishes. Through case examples, design, material and fabrication considerations will be discussed. While their use is not widespread, there are a number of patients who benefit from the provision of unilateral RPDs. They are a useful treatment to have in the clinician's armamentarium, but a highly-skilled dental team and a specific patient presentation is required in order for them to be a reasonable and predictable prosthetic option.

  9. An Investigation into the Accuracy of Two Currently Available Dental Impression Materials in the Construction of Cobalt-Chromium Frameworks for Removable Partial Dentures.

    Science.gov (United States)

    Dubal, Rajesh Kumar; Friel, Tim; Taylor, Philip D

    2015-03-01

    This study investigated the suitability of irreversible hydrocolloid as an impression material for cobalt-chromium framework construction. Scans of casts derived from (1) alginate and (2) addition-cured polyvinylsiloxane impressions were superposed on to a control. The differences within and between groups were compared at fixed landmarks. The investigation revealed a high degree of scan coincidence within and between groups. However, certain features, such as undercuts, resulted in a lower degree of scan coincidence. Irreversible hydrocolloid appears to be a viable alternative to addition-cured polyvinyl-siloxane as an impression material for cobalt-chromium framework construction.

  10. [Acrylic resin removable partial dentures

    NARCIS (Netherlands)

    Baat, C. de; Witter, D.J.; Creugers, N.H.J.

    2011-01-01

    An acrylic resin removable partial denture is distinguished from other types of removable partial dentures by an all-acrylic resin base which is, in principle, solely supported by the edentulous regions of the tooth arch and in the maxilla also by the hard palate. When compared to the other types of

  11. Advances In Hexavalent Chromium Removal At Hanford

    International Nuclear Information System (INIS)

    Neshem, D.O.; Riddelle, J.

    2012-01-01

    At the Hanford Site, chromium was used as a corrosion inhibitor in the reactor cooling water and was introduced into the groundwater as a result of planned and unplanned discharges from reactors during plutonium production since 1944. Beginning in 1995, groundwater treatment methods were evaluated leading to the use of pump and treat facilities with ion exchange using Dowex 21 K, a regenerable strong base anion exchange resin. This required regeneration of the resin, which is currently performed offsite. Resin was installed in a 4 vessel train, with resin removal required from the lead vessel approximately once a month. In 2007, there were 8 trains (32 vessels) in operation. In 2008, DOE recognized that regulatory agreements would require significant expansion in the groundwater chromium treatment capacity. Previous experience from one of the DOE project managers led to identification of a possible alternative resin, and the contractor was requested to evaluate alternative resins for both cost and programmatic risk reductions. Testing was performed onsite in 2009 and 2010, using a variety of potential resins in two separate facilities with groundwater from specific remediation sites to demonstrate resin performance in the specific groundwater chemistry at each site. The testing demonstrated that a weak base anion single-use resin, ResinTech SIR-700, was effective at removing chromium, had a significantly higher capacity, could be disposed of efficiently on site, and would eliminate the complexities and programmatic risks from sampling, packaging, transportation and return of resin for regeneration. This resin was installed in Hanford's newest groundwater treatment facility, called 100-DX, which began operations in November, 2010, and used in a sister facility, 100-HX, which started up in September of 2011. This increased chromium treatment capacity to 25 trains (100 vessels). The resin is also being tested in existing facilities that utilize Dowex 21 K for

  12. Removal of hexavalent chromium from aqueous solution using ...

    African Journals Online (AJOL)

    Removal of hexavalent chromium from aqueous solution using activated carbon derived from palmyra palm fruit seed. A. Kannan, S. Thambidurai. Abstract. In this study, removal of chromium(VI) from aqueous solutions by Palmyra palm fruit seed carbon (PPFSC) and commercial activated carbon (CAC) was investigated.

  13. [Acrylic resin removable partial dentures].

    Science.gov (United States)

    de Baat, C; Witter, D J; Creugers, N H J

    2011-01-01

    An acrylic resin removable partial denture is distinguished from other types of removable partial dentures by an all-acrylic resin base which is, in principle, solely supported by the edentulous regions of the tooth arch and in the maxilla also by the hard palate. When compared to the other types of removable partial dentures, the acrylic resin removable partial denture has 3 favourable aspects: the economic aspect, its aesthetic quality and the ease with which it can be extended and adjusted. Disadvantages are an increased risk of caries developing, gingivitis, periodontal disease, denture stomatitis, alveolar bone reduction, tooth migration, triggering of the gag reflex and damage to the acrylic resin base. Present-day indications are ofa temporary or palliative nature or are motivated by economic factors. Special varieties of the acrylic resin removable partial denture are the spoon denture, the flexible denture fabricated of non-rigid acrylic resin, and the two-piece sectional denture. Furthermore, acrylic resin removable partial dentures can be supplied with clasps or reinforced by fibers or metal wires.

  14. Removal of chromium and lead from drill cuttings using activated ...

    African Journals Online (AJOL)

    Palm kernel shell and Palm kernel husk, two readily available agricultural waste products have been used as low-cost potential adsorbents to remove chromium and lead from drill cuttings. Batch adsorption studies were carried out as a function of parameters such as pH, contact time and carbon dosage. Chromium and ...

  15. Utilization of alum sludge as chromium removal

    Science.gov (United States)

    Zahari, Nazirul Mubin; Sidek, Lariyah Mohd; Zulkifli, Muhammad Azmeer Asyraf; Hua, Chua Kok; Jalil, Nurulhidayah Abdul

    2017-09-01

    The amount of alum sludge produced at water treatment plant has become a problem where it is highly costly in order to dispose them. Various research was conducted to find the most suitable and economic alternative to recycle and reused of alum sludge. In this study, alum sludge was retrieved from Waterworks where it was dewatered, dried, grounded and sieved to obtain smallest particle sizes of alum sludge. The synthetic water was prepared at the laboratory in as it was used to imitate the properties of real water contaminated with chromium. This study was conducted to determine the percentage reduction of chromium concentration in synthetic water by using alum sludge as absorbent. The percentage reduction of chromium was observed under the effect of initial concentration of chromium and the height of alum sludge. The result indicates that chromium concentration reduction was the highest at the lowest initial concentration and at the highest height of alum sludge and vice versa.

  16. Chromium removal from tannery wastewater by using of flying ash

    International Nuclear Information System (INIS)

    Gil P, E.; Saldarriaga M, C.

    1998-01-01

    A simple and economic method to chromium removal from tannery wastewater by means of flying ash is presented. The chromium removal operation is a discontinuous process that involve the mass of flying ash, time of contact and temperature or ph as variables, their which are optimized through Box-Wilson type experimental design. The results were successful: From an initial fluid whit chromium concentration of 1850m ppm, final concentrations of 0.008 ppm and 0.5 ppm of Cr+3 and Cr+6 respectively were achieved. These post-treatment concentrations are into the approved range definite by Government's Laws to this waste type

  17. Surfactant Enhanced Chromium Removal Using a Silica Gel Column

    Directory of Open Access Journals (Sweden)

    N. Rajesh

    2001-06-01

    Full Text Available A simple and rapid method is proposed for the removal of chromium based on its adsorption as an ion pair with Cetyl Trimethyl Ammonium Bromide (CTABr on a silica gel colurnn. The surfactant (CTABr is bonded to chromate by electrostatic force of attraction and the resulting ion-association complex is held on a silica gel column. The resulting solution from the column is analyzed for chromium by the standard diphenyl carbazide spectrophotometric procedure. The method has been applied successfully to study the recovery of chromium in various synthetic mixtures.

  18. Adsorption kinetics for the removal of chromium (VI) from aqueous ...

    African Journals Online (AJOL)

    Adsorption kinetics for the removal of chromium (VI) from aqueous solutions on the activated carbons prepared from agricultural wastes. ... The batch removal of Cr(VI) from aqueous solution using low-cost adsorbents such as cornelian cherry, apricot stone and almond shell under different experimental conditions was ...

  19. Removal of Chromium and Lead from Industrial Wastewater Using

    Directory of Open Access Journals (Sweden)

    Mohamed Hilal

    2013-04-01

    Full Text Available In this research an attempt is made on the ability of aerobic treatment of synthetic solutions containing lead and chromium using effective microorganisms within the reactor. To achieve the desired objectives of the research, synthetic aqueous solutions of lead and chromium was used in the concentration of chromium and lead ions of 5, 10,50 and 100 mg / l .The work was done at constant pH equal to 4.5 and temperature of 30 ± 1 º C. Effective microorganisms solutions was added to the reactor at Vol.% of 1/50 ,1/100 ,1/500 and 1/1000, with retention time was 24 hours to measure the heavy metals concentration the atomic absorption device was used. The experimental results showed that each 1mg / l of lead and chromium ions need 24 mg of effective microorganisms to achieve removal of 92.0% and 82.60% for lead and chromium respectively. Increasing the concentration of effective microorganisms increases the surface of adsorption and thus increasing the removal efficiency. It is found that the microorganisms activity occur in the first five hours of processing and about 94% of adsorption capacity of biomass will take place. It is also found the selectivity of microorganisms to lead ions is higher than for chromium ions.

  20. Removable partial dentures: clinical concepts.

    Science.gov (United States)

    Bohnenkamp, David M

    2014-01-01

    This article provides a review of the traditional clinical concepts for the design and fabrication of removable partial dentures (RPDs). Although classic theories and rules for RPD designs have been presented and should be followed, excellent clinical care for partially edentulous patients may also be achieved with computer-aided design/computer-aided manufacturing technology and unique blended designs. These nontraditional RPD designs and fabrication methods provide for improved fit, function, and esthetics by using computer-aided design software, composite resin for contours and morphology of abutment teeth, metal support structures for long edentulous spans and collapsed occlusal vertical dimensions, and flexible, nylon thermoplastic material for metal-supported clasp assemblies. Copyright © 2014 Elsevier Inc. All rights reserved.

  1. Citric-acid preacidification enhanced electrokinetic remediation for removal of chromium from chromium-residue-contaminated soil.

    Science.gov (United States)

    Meng, Fansheng; Xue, Hao; Wang, Yeyao; Zheng, Binghui; Wang, Juling

    2018-02-01

    Electrokinetic experiments were conducted on chromium-residue-contaminated soils collected from a chemical plant in China. Acidification-electrokinetic remediation technology was proposed in order to solve the problem of removing inefficient with ordinary electrokinetic. The results showed that electrokinetic remediation removal efficiency of chromium from chromium-contaminated soil was significantly enhanced with acidizing pretreatment. The total chromium [Cr(T)] and hexavalent chromium [Cr(VI)] removal rate of the group acidized by citric acid (0.9 mol/L) for 5 days was increased from 6.23% and 19.01% in the acid-free experiments to 26.97% and 77.66% in the acidification-treated experiments, respectively. In addition, part of chromium with the state of carbonate-combined will be converted into water-soluble state through acidification to improve the removal efficiency. Within the appropriate concentration range, the higher concentration of acid was, the more chromium was released. So the removal efficiency of chromium depended on the acid concentration. The citric acid is also a kind of complexing agent, which produced complexation with Cr that was released by the electrokinetic treatment and then enhanced the removal efficiency. The major speciation of chromium that was removed from soils by acidification-electrokinetics remediation was acid-soluble speciation, revivification speciation and oxidation speciation, which reduced biological availability of chromium.

  2. [Removable partial dentures. Oral functions and types

    NARCIS (Netherlands)

    Creugers, N.H.J.; Baat, C. de

    2009-01-01

    A removable partial denture enables the restoration or improvement of 4 oral functions: aesthetics, mandibular stability, mastication, and speech. However, wearing a removable partial denture should not cause oral comfort to deteriorate. There are 3 types of removable partial dentures: acrylic

  3. [Conventional retaining of removable partial dentures

    NARCIS (Netherlands)

    Keltjens, H.M.A.M.; Witter, D.J.; Creugers, N.H.J.

    2009-01-01

    Mechanical and biological criteria have to be met in retaining the metal frame of a removable partial denture. Additionally, a removable partial denture is part of the occlusal interface by the clasps and the denture teeth. With respect to mechanical aspects, all rigid parts of the removable partial

  4. Removal of Lead and Chromium from Aqueous Solution onto ...

    African Journals Online (AJOL)

    OLUWASOGO

    pH, initial concentration as well as adsorbent dosage on the removal efficiency of both metal ions was investigated via batch adsorption. ... lead and chromium in wastewater as indicated by the United. States Environmental Protection ... electro dialysis, membrane separations, reverse osmosis and solvent extraction in the ...

  5. Selective removal of chromium from sulphuric acid leach liquor of ...

    African Journals Online (AJOL)

    The selective removal of chromium, a trace impurity that degrades the whiteness of titanium(IV) oxide pigments, from sulphuric acid leach liquor of ilmenite, was investigated by solvent extraction with xylene solutions of trioctylamine. Important factors of commercial significance affecting the extraction operation have been ...

  6. Removal of Hexavalent Chromium from Aqueous Solutions using ...

    African Journals Online (AJOL)

    The hexavalent chromium exists in aquatic media as water soluble complex anions and persist. These are concentrated in industrial waste water especially from the tannery industries and release of effluents from industries adversely affects the environment. The removal of heavy metals from aqueous solutions is carried ...

  7. Purification Method of Industrial Waste Water with Hexavalent Chromium Removal

    Directory of Open Access Journals (Sweden)

    Sara Banafsheafshan

    2016-12-01

    Full Text Available Background and Objective: Common sources of chromium in wastewater are electroplating and leather industries. Thus, the aim of this study is synthesis activated carbon fiber/zinc oxide composite to remove of Cr (VI from polluted water.Materials and Methods: The immobilization of zinc oxide (ZNO on activated carbon fiber (ACF was accomplished by Sol-gel method and synthesized activated carbon fiber composite (ACF/ZNO,was used to reduction of chromium under ultraviolet light from aqueous solution. And characterized by BET, SEM, XRD. After the design of the reactor, hexavalent chromium stock solution, using a solution of potassium dichromate (K2Cr2O7 in distilled water, were prepared. The residual concentration of chromium was analyzed by the 1,5-diphenylcar-bazide method using a spectrophotometer at a wave length of 540 nm.Results: The XRD results showed that a typical hexagonal phase for ZnO. The SEM results showed that zinc oxide were distributed on the ACF surface. It showed that the BET surface area was related to adsorption capacity for composite. Parameters effect, including concentration of pollutants, composite dose and pH were studied.Conclusion: In optimal conditions, initial chromium concentration of 5 mg/l, composite dose 2.5 g/l and a pH of 3, after 120 minutes, system removal efficiency was 85%.

  8. [Removable partial dentures. Oral functions and types].

    Science.gov (United States)

    Creugers, N H J; de Baat, C

    2009-11-01

    A removable partial denture enables the restoration or improvement of 4 oral functions: aesthetics, mandibular stability, mastication, and speech. However, wearing a removable partial denture should not cause oral comfort to deteriorate. There are 3 types of removable partial dentures: acrylic tissue-supported dentures, dentures with cast metal frameworks en dentures with cast metal frameworks and (semi)precision attachments. Interrupted tooth arches,free-ending tooth arches, and a combination of interrupted as well as free-ending tooth arches can be restored using these dentures. Well-known disadvantages of removable partial dentures are problematic oral hygiene, negative influence on the remaining dentition and limited oral comfort. Due to the advanced possibilities of fixed tooth- or implant-supported partial dentures, whether or not free-ending, or tooth- as well as implant-supported partial dentures, the indication of removable partial dentures is restricted. Nevertheless, for the time being the demand for removable partial dentures is expected to continue.

  9. Chromium

    Science.gov (United States)

    ... Office of Dietary Supplements Health Professional Other Resources Chromium Dietary Supplement Fact Sheet Have a question? Ask ... of chromium Chromium and Healthful Diets References Disclaimer Chromium: What is it? Chromium is a mineral that ...

  10. Chromium removal from solution by five photosynthetic bacteria isolates.

    Science.gov (United States)

    Su, Yan-Qiu; Zhao, Yang-Juan; Wu, Nan; Chen, Yang-Er; Zhang, Wei-Jia; Qiao, Dai-Rong; Cao, Yi

    2018-02-01

    Biological method has been recognized as a low-cost and ecofriendly approach for removing heavy metals from aqueous wastes. In this study, the ability of five photosynthetic bacteria isolates (strains labeled SC01, HN02, SC05, JS01, and YN01) was examined for their ability to remove Cr from Cr-containing solutions. Furthermore, the possible removal mechanisms were elucidated by comparing chromium removal rates, antioxidant reaction, and accumulation of reactive oxygen species (ROS). Among the five bacteria, strains SC01 and SC05 presented the highest removal rates of chromium ions and the activity of cysteine desulfhydrase under Cr stress. They also showed lower levels of ROS and cell death than the other three bacteria strains under Cr stress. In addition, total bacteriochlorophyll content and activities of six antioxidant enzymes in SC01 were highest among these selected strains. On the contrary, strain HN02 presented the lowest level of Cr removal and the lowest activities of antioxidant enzymes. It also exhibited the highest level of ROS under Cr(VI) stress. Overall, these results show that the strains SC01 and SC05 have good Cr removal ability and could be used for removal of Cr in industrial effluents.

  11. Removal of Chromium from Industrial Wastewater Using Silicon Nanoparticle

    Directory of Open Access Journals (Sweden)

    Laleh Ranandeh Kalankesh

    2015-03-01

    Full Text Available Hexavalent chromium is a pollutant found in surface and underground waters that causes serious environmental hazards. Chromium enters water as a result of industrial activities such as electroplating, dyeing, leather tanning, and metal manufacturing. The objective of the present laboratory-experimental study was to remove chromate from industrial effluents using silicon nanoparticles. The experiments were performed with both simulated synthetic wastewater and true wastewater. Various parameters such as pH, contact time, and different concentrations of Cr(VI and SiO2 were examined. The data obtained were analyzed using the Excel and SPSS Ver. 16. It was found that Cr(VI removal increased with decreasing pH and increasing contact time. The highest Cr(VI removal was achieved at pH=3 and a contact time of 120 minutes. It was also observed that removal observed to obey the Langmuir isotherm and pseudo second-order kinetic models, respectively. The findings indicate that silicon nanoparticles are capable of removeing Cr(VI from industrial effluents. Given the Cr(VI removal efficiency of 93.6% achieved under optimum conditions and  the removal efficiency of 88.6% achieved in real samples, the method may be recommended as a highly efficient one for removing Cr(VI from industrial wastewaters.

  12. Chromium removal from aqueous media by superparamagnetic ...

    Indian Academy of Sciences (India)

    dead fungal biomass, cyanobacteria, green alga, etc.9–15. However, most of these adsorbents have low adsorption capacity for Cr(VI) removal. Consequently, there is a need for development of new environmentally friendly or green adsorbents having larger surface area and better durability. In this respect, magnetic iron ...

  13. [Removable partial dentures. Oral functions and types

    OpenAIRE

    Creugers, N.H.J.; Baat, C. de

    2009-01-01

    A removable partial denture enables the restoration or improvement of 4 oral functions: aesthetics, mandibular stability, mastication, and speech. However, wearing a removable partial denture should not cause oral comfort to deteriorate. There are 3 types of removable partial dentures: acrylic tissue-supported dentures, dentures with cast metal frameworks en dentures with cast metal frameworks and (semi)precision attachments. Interrupted tooth arches,free-ending tooth arches, and a combinatio...

  14. Removal and transformation of hexavalent chromium in sequencing ...

    African Journals Online (AJOL)

    The objectives of this study are to evaluate the efficiency of removal of hexavalent chromium (Cr(VI)) in a sequencing batch reactor (SBR) and to ascertain the fate of Cr(VI) in the treatment process. An SBR was operated with the FILL, REACT, SETTLE, DRAW and IDLE periods in the time ratio of 2:12:2:1.5:6.5 for a cycle ...

  15. Application of Genetic Engineering for Chromium Removal from Industrial Wastewater

    OpenAIRE

    N. K. Srivastava; M. K. Jha; I. D. Mall; Davinder Singh

    2010-01-01

    The treatment of the industrial wastewater can be particularly difficult in the presence of toxic compounds. Excessive concentration of Chromium in soluble form is toxic to a wide variety of living organisms. Biological removal of heavy metals using natural and genetically engineered microorganisms has aroused great interest because of its lower impact on the environment. Ralston metallidurans, formerly known as Alcaligenes eutrophus is a LProteobacterium colonizing indus...

  16. Lead and chromium removal from leachate using horsetail (Equisetum hyemale

    Directory of Open Access Journals (Sweden)

    E. Kurniati

    2014-01-01

    Full Text Available Phytoremediation has been widely used for wastewater treatment technology. Horsetail was investigated for its capacity to remediate lead and chromium in leachate. This plant seemed to be an effective choice for phytoremediation due to its survival in extreme to moderate conditions, the availability of annual or perennial varieties and a deep root system. Conducted in a greenhouse, this research used leachate from final disposal. The leachate was exposed to six treated plants with three multiplications using activated natural zeolite media for one month. The treatments were flow system i.e. batch and continue, and living plants weight that is 0, 153 and 306 g planted in 20 cm diameter and 30 cm deep pots. The leachate pH, temperature, lead, and chromium concentration were observed and also the surrounding temperature and humidity. Results showed that 82.2% of lead can be removed by 153 gram horsetail on batch system as well as 61.2% chromium removal by 153 gram horsetail on continue system. Horsetail seemed to have future to be applied in phytoremediation of artisanal and small scale mining waste.

  17. Chromium removal from electroplating wastewater by coir pith

    International Nuclear Information System (INIS)

    Suksabye, Parinda; Thiravetyan, Paitip; Nakbanpote, Woranan; Chayabutra, Supanee

    2007-01-01

    Coir pith is a by-product from padding used in mattress factories. It contains a high amount of lignin. Therefore, this study investigated the use of coir pith in the removal of hexavalent chromium from electroplating wastewater by varying the parameters, such as the system pH, contact time, adsorbent dosage, and temperature. The maximum removal (99.99%) was obtained at 2% (w/v) dosage, particle size -1 , system pH 2, and an equilibrium time of 18 h. The adsorption isotherm of coir pith fitted reasonably well with the Langmuir model. The maximum Cr(VI) adsorption capacity of coir pith at 15, 30, 45 and 60 deg. C was 138.04, 197.23, 262.89 and 317.65 mg Cr(VI) g -1 coir pith, respectively. Thermodynamic parameters indicated an endothermic process and the adsorption process was favored at high temperature. Desorption studies of Cr(VI) on coir pith and X-ray absorption near edge structure (XANES) suggested that most of the chromium bound on the coir pith was in Cr(III) form due to the fact that the toxic Cr(VI) adsorbed on the coir pith by electrostatic attraction was easily reduced to less toxic Cr(III). Fourier transform infrared (FT-IR) spectrometry analysis indicated that the carbonyl (C=O) groups and methoxy (O-CH 3 ) groups from the lignin structure in coir pith may be involved in the mechanism of chromium adsorption. The reduced Cr(III) on the coir pith surface may be bound with C=O groups and O-CH 3 groups through coordinate covalent bonding in which a lone pair of electrons in the oxygen atoms of the methoxy and carbonyl groups can be donated to form a shared bond with Cr(III)

  18. FERRATE TREATMENT FOR REMOVING CHROMIUM FROM HIGH-LEVEL RADIOACTIVE TANK WASTE

    International Nuclear Information System (INIS)

    Sylvester, Paul; Rutherford, Andy; Gonzalez-Martin, Anuncia; Kim, J.; Rapko, Brian M.; Lumetta, Gregg J.

    2000-01-01

    A method has been developed for removing chromium from alkaline high-level radioactive tank waste. Removing chromium from these wastes is critical in reducing the volume of waste requiring expensive immobilization and deep geologic disposition. The method developed is based on the oxidation of insoluble chromium(III) compounds to soluble chromate using ferrate. The tests conducted with a simulated Hanford tank sludge indicate that the chromium removal with ferrate is more efficient at 5 M NaOH than at 3 M NaOH. Chromium removal increases with increasing Fe(VI)/Cr(III) molar ratio, but the chromium removal tends to level out for Fe(VI)/Cr(III) greater than 10. Increasing temperature leads to better chromium removal, but higher temperatures also led to more rapid ferrate decomposition. Tests with radioactive Hanford tank waste generally confirmed the simulant results. In all cases examined, ferrate enhanced the chromium removal, with a typical removal of around 60-70% of the total chromium present in the washed sludge solids. The ferrate leachate solutions did not contain significant concentrations of transuranic elements, so these solutions could be handled as low-activity waste

  19. Hexavalent chromium removal by viable, granular anaerobic biomass.

    Science.gov (United States)

    Massara, Hafez; Mulligan, Catherine N; Hadjinicolaou, John

    2008-12-01

    Hexavalent chromium in industrial wastewater is a major concern due to its extreme toxicity. This study investigates the removal of Cr(VI) using viable anaerobic granular biomass as a biosorbent. The effect of Cr(VI) concentration on biogas content and COD removal using batch studies indicated that the phase II (methanogenic-rich) culture was more sensitive than the phase I (acidogenic-rich) culture. Toxicity indices for both cultures using COD removal were developed based on linear-log interpolation. The median inhibition Cr(VI) concentration (IC(50)), for phase II cultures was found to be 263mg/L, while that for phase I cultures was 309mg/L. A sorption study was conducted on viable and non-viable (dried) phase I-rich biomass: both followed the Langmuir model. In addition, the biosorption capacity for metabolically inhibited biomass was 25% less indicating some level of cellular uptake associated with Cr(VI) removal. This study demonstrated the potential for a two-phase anaerobic treatment system for a Cr(VI)-contaminated effluent.

  20. Removable partial dentures: use of rapid prototyping.

    Science.gov (United States)

    Lima, Julia Magalhaes Costa; Anami, Lilian Costa; Araujo, Rodrigo Maximo; Pavanelli, Carlos A

    2014-10-01

    The CAD/CAM technology associated with rapid prototyping (RP) is already widely used in the fabrication of all-ceramic fixed prostheses and in the biomedical area; however, the use of this technology for the manufacture of metal frames for removable dentures is new. This work reports the results of a literature review conducted on the use of CAD/CAM and RP in the manufacture of removable partial dentures. © 2014 by the American College of Prosthodontists.

  1. [Elderly people and removable partial dentures

    NARCIS (Netherlands)

    Baat, C. de

    2009-01-01

    The most frequently reported disadvantages of removable partial dentures are the more demanding daily oral hygiene self-care, especially for people who already experience difficulties in self-care, and the possible harmful influence on the remaining dentition. These disadvantages can be expressed in

  2. Dual Component Removable Partial Denture shows improved ...

    African Journals Online (AJOL)

    Dual Component Removable Partial Denture (DuCo RPD) is composed of a double base; lower and upper. The lower base, where the artificial teeth are attached, acts as a support and is in contact with the alveolar ridges and oral mucosa. Clasps are designed on the upper base, which acts towards the retention and ...

  3. [Designing metal frame removable partial dentures

    NARCIS (Netherlands)

    Witter, D.J.; Barel, J.C.; Keltjens, H.M.A.M.; Creugers, N.H.J.

    2011-01-01

    Oral health care providers have the full responsibility for designing metal frame removable partial dentures and making all of the necessary preparations. Important principles of design are that the denture should hamper natural cleaning and daily oral hygiene as little as possible and that it

  4. Dual Component Removable Partial Denture shows improved ...

    African Journals Online (AJOL)

    STORAGESEVER

    2009-02-18

    Feb 18, 2009 ... performed for three years to survey body weight, physical signs, facial symmetry, dental caries, alveolar bone density ... symmetry, dental caries, alveolar bone density and periodontal status were not statistically different between the ..... provisional to an existing removable partial denture. J. Prosthodont.

  5. Mechanism for partial oxidation of Cyclohexene by Chromium (VI ...

    African Journals Online (AJOL)

    The oxidation of cyclohexene by chromium (VI) oxide in aqueous and acetic media has been studied. The reaction products were analysed using classical method, IR and GC/MS analyses. The major products of the oxidation reaction in acetic acid medium are cyclohexanol, cyclohexanone, cyclohex-2-en-1-one, ...

  6. Regeneration of pilot-scale ion exchange columns for hexavalent chromium removal.

    Science.gov (United States)

    Korak, Julie A; Huggins, Richard; Arias-Paic, Miguel

    2017-07-01

    Due to stricter regulations, some drinking water utilities must implement additional treatment processes to meet potable water standards for hexavalent chromium (Cr(VI)), such as the California limit of 10 μg/L. Strong base anion exchange is effective for Cr(VI) removal, but efficient resin regeneration and waste minimization are important for operational, economic and environmental considerations. This study compared multiple regeneration methods on pilot-scale columns on the basis of regeneration efficiency, waste production and salt usage. A conventional 1-Stage regeneration using 2 N sodium chloride (NaCl) was compared to 1) a 2-Stage process with 0.2 N NaCl followed by 2 N NaCl and 2) a mixed regenerant solution with 2 N NaCl and 0.2 N sodium bicarbonate. All methods eluted similar cumulative amounts of chromium with 2 N NaCl. The 2-Stage process eluted an additional 20-30% of chromium in the 0.2 N fraction, but total resin capacity is unaffected if this fraction is recycled to the ion exchange headworks. The 2-Stage approach selectively eluted bicarbonate and sulfate with 0.2 N NaCl before regeneration using 2 N NaCl. Regeneration approach impacted the elution efficiency of both uranium and vanadium. Regeneration without co-eluting sulfate and bicarbonate led to incomplete uranium elution and potential formation of insoluble uranium hydroxides that could lead to long-term resin fouling, decreased capacity and render the resin a low-level radioactive solid waste. Partial vanadium elution occurred during regeneration due to co-eluting sulfate suppressing vanadium release. Waste production and salt usage were comparable for the 1- and 2-Stage regeneration processes with similar operational setpoints with respect to chromium or nitrate elution. Published by Elsevier Ltd.

  7. REMOVAL COPPER, CHROMIUM, ARSENIC FROM OUT-OF- SERVICE CCA-TREATED WOOD MATERIALS

    Directory of Open Access Journals (Sweden)

    Engin Derya Gezer

    2004-11-01

    Full Text Available Remediation can be defined as removing copper, chromium and arsenic from out-of-service CCA treated wood products. There are some various remediation methods that can be applied to remove copper, chromium and arsenic from out-of service CCA treated wood products in order to re-use that wooden materials and minimize adverse impacts of those out-of service CCA treated wood to environment, human health, animals and other living organisms. In this study, those applied various remediation methods to remove copper, chromium and arsenic were summarized.

  8. Flexible removable partial dentures: a basic overview.

    Science.gov (United States)

    Hill, Edward E; Rubel, Barry; Smith, John B

    2014-01-01

    For many years, flexible resin materials have been available for fabricating removable partial denture (RPD) prostheses. Using a nonrigid material for the major connector or other components of an RPD may be a consideration for certain patients. Except for the promotional literature that has been written for flexible resin dentures, there is very little information available in the dental literature concerning nonrigid RPDs. As a result, the decision to use this treatment option depends on the judgment and experience of the dentist and fabricating laboratory. This article summarizes clinically pertinent information about flexible, nonrigid partial dentures.

  9. The removal of chromium from wastewaters by activated bentonite

    International Nuclear Information System (INIS)

    Mellah, A.; Chegrouche, S.; Ait Ghezala, H.; Douar, L.

    1994-12-01

    The adsorption of chromium onto activated bentonite has been investigated. Adsorption isotherms were analysed to obtain the Langmuir and freundlich constants. The operating parameters (i.e pH, contact time, solid/liquid ratio, temperatureand initial chromium concentration) influenced the rate of adsorption have been studied

  10. Removal of hexavalent chromium from aqueous solution by barium ion cross-linked alginate beads

    Directory of Open Access Journals (Sweden)

    Uzaşçı Sesil

    2014-07-01

    Full Text Available Barium ion cross-linked alginate beads have shown great affinity to toxic hexavalent chromium ions in aqueous solution, contrary to the traditional calcium alginate beads. The adsorption experiments were carried out by the batch contact method. The optimal pH for removal was found to be pH 4. The equilibrium was established in 4 h and the removal efficiency of chromium (VI was found as 95%. The adsorption data fit well with Langmuir and Freundlich isotherms. The maximum chromium (VI adsorption capacity determined from Langmuir isotherm was 36.5 mg/g dry alginate beads. Our study suggests that barium alginate beads can be used as cost-effective and efficient adsorbents for the removal of chromium (VI from contaminated waters.

  11. A novel surface cleaning method for chemical removal of fouling lead layer from chromium surfaces

    Science.gov (United States)

    Gholivand, Kh.; Khosravi, M.; Hosseini, S. G.; Fathollahi, M.

    2010-10-01

    Most products especially metallic surfaces require cleaning treatment to remove surface contaminations that remain after processing or usage. Lead fouling is a general problem which arises from lead fouling on the chromium surfaces of bores and other interior parts of systems which have interaction with metallic lead in high temperatures and pressures. In this study, a novel chemical solution was introduced as a cleaner reagent for removing metallic lead pollution, as a fouling metal, from chromium surfaces. The cleaner aqueous solution contains hydrogen peroxide (H 2O 2) as oxidizing agent of lead layer on the chromium surface and acetic acid (CH 3COOH) as chelating agent of lead ions. The effect of some experimental parameters such as acetic acid concentration, hydrogen peroxide concentration and temperature of the cleaner solution during the operation on the efficiency of lead cleaning procedure was investigated. The results of scanning electron microscopy (SEM) showed that using this procedure, the lead pollution layer could be completely removed from real chromium surfaces without corrosion of the original surface. Finally, the optimum conditions for the complete and fast removing of lead pollution layer from chromium surfaces were proposed. The experimental results showed that at the optimum condition (acetic acid concentration 28% (V/V), hydrogen peroxide 8% (V/V) and temperature 35 °C), only 15-min time is needed for complete removal of 3 g fouling lead from a chromium surface.

  12. Evaluation of selected wetland plants for removal of chromium from ...

    African Journals Online (AJOL)

    Wastewater from leather processing industries is very complex and leads to water pollution if discharged untreated, especially due to its high organic loading and chromium content. In this study, the phytoremediation efficiency of selected wetland plant species in subsurface flow (SSF) constructed wetlands receiving ...

  13. REMOVAL OF CHROMIUM FROM AQUEOUS SOLUTION USING LOCALLY AVAILABLE INEXPENSIVE TARO AND WATER HYACINTH AS BIOSORBENT

    Directory of Open Access Journals (Sweden)

    Shahjalal Khandaker

    2016-04-01

    Full Text Available In this investigation, locally available and inexpensive Taro and Water Hyacinth were used as biosorbents to remove chromium from synthetic wastewater. The removal of this metal ion from water in the batch and column method have been studied and discussed. Adsorption kinetics and equilibrium isotherm studies were also carried out. The material exhibits good adsorption capacity and the data follow both Freundlich and Langmuir models. Scanning Electronic Microscopic image was also used to understand the surface characteristics of biosorbent before and after biosorption studies. Effects of various factors such as pH, adsorbent dose, adsorbate initial concentration, particle size etc. were analyzed. The initial concentrations of chromium were considered 5-30mgL-1 in batch method and only 4mgL-1 in column method. The maximum chromium adsorbed was 1.64 mgg-1 and 4.44 mgg-1 in Batch method and 1.15 mgg-1 and 0.75 mgg-1 in Column method. Batch and Column desorption and regeneration studies were conducted. Column desorption studies indicated that both of these biosorbents could be reused for removing heavy metals. Results of the laboratory experiments show that the performance of Taro and Water Hyacinth prove that they can effectively be used as low cost biosorbents for the removal of chromium from wastewater.KEYWORDS:   adsorption; chromium removal; Taro; water hyacinth; batch method; column studies

  14. Effect of pH on the Removal of Chromium (Cr (VI by Sugar Cane Bagasse

    Directory of Open Access Journals (Sweden)

    Nasim Ahmed Khan

    2001-12-01

    Full Text Available The industrial estates in India are dominated by small and medium scale industries, which are posing a serious threat to the environment by virtue of discharging effluents of a polluting nature. The problems become severe due to the presence of heavy metals in the effluents. Chromium is widely used in a number of industries such as electroplating, metal finishing, cooling towers, dyes, paints, anodising and leather tanning industries. The toxicity of chromium (VI is well known and is considered a hazard to the health of humans and animals. The presence of chromium (VI in aquatic environments at high concentrations is also lethal to marine species. The treatment of chromium bearing effluents have been reported through several methods, such as chemical reduction,  precipitation, ion exchange, electrochemical reduction, evaporation, reverse osmosis and adsorption. However among these, adsorption is found to be highly effective, inexpensive and an easy method to operate. India is an agricultural country and generates a considerable amount of agricultural wastes such as sugar cane bagassess, coconut jute, nut shell, rice straw, rice husk, waste tea leaves, ground nut husk, crop wastes, peanut hulls and fertilizer wastes. Successful studies on these materials could be beneficial to developing countries and could be easily applied as adsorbents for the removal of chromium from wastewater. Most of the previous work highlights the use of commercial activated carbon but these adsorbents are relatively expensive and less feasible to be used in developing countries. Keeping these in view batch experiments have been designed to study the feasibility of sugar cane bagasse to remove chromium (VI from the aqueous solutions. While evaluationg the impact of various parameters, such as adsorbent does, contact time, initial concentration and pH on chromium removal efficiency, the results indicate a prominent effect of pH on the chromium reduction by the adsorbent

  15. Removal of chromium and toxic ions present in mine drainage by Ectodermis of Opuntia

    Energy Technology Data Exchange (ETDEWEB)

    Barrera, Hector [Universidad Autonoma del Estado de Mexico, Facultad de Quimica, Paseo Colon interseccion Paseo Tollocan S/N, C.P. 50120, Toluca, Estado de Mexico (Mexico); Urena-Nunez, Fernando [Instituto Nacional de Investigaciones Nucleares, A.P.18-1027, Col. Escandon, Delegacion Miguel Hidalgo, C.P. 11801, Mexico, D.F. (Mexico); Bilyeu, Bryan [University of North Texas, Department of Materials Science and Engineering, P.O. Box 305310, Denton, TX 76203-5310 (United States); Barrera-Diaz, Carlos [Universidad Autonoma del Estado de Mexico, Facultad de Quimica, Paseo Colon interseccion Paseo Tollocan S/N, C.P. 50120, Toluca, Estado de Mexico (Mexico)]. E-mail: cbarrera@uaemex.mx

    2006-08-25

    This work presents conditions for hexavalent and trivalent chromium removal from aqueous solutions using natural, protonated and thermally treated Ectodermis of Opuntia. A removal of 77% of Cr(VI) and 99% of Cr(III) can be achieved. The sorbent material is characterized using scanning electron microscopy, energy dispersive X-ray spectroscopy, infrared spectroscopy, thermogravimetric analysis, before and after the contact with the chromium containing aqueous media. The results obtained from the characterization techniques indicate that the metal ion remains on the surface of the sorbent material. The percentage removal is found to depend on the initial chromium concentration and pH. The Cr(VI) and Cr(III) uptake process is maximum at pH 4, using 0.1 g of sorbent per liter of aqueous solution. The natural Ectodermis of Opuntia showed a chromium adsorption capacity that was adequately described by the Langmuir adsorption isotherm. Finally, an actual mine drainage sample that contained Cd, Cr, Cu, Fe Zn, Ni and Pb was tested under optimal conditions for chromium removal and Ectodermis of Opuntia was found to be a suitable sorbent material. The use of this waste material for the treatment of metal-containing aqueous solutions as well as mine drainage is effective and economical.

  16. REMOVAL OF LEAD AND CHROMIUM FROM AQUEOUS SOLUTION BY BACILLUS CIRCULANS BIOFILM

    Directory of Open Access Journals (Sweden)

    A. Khanafari, S. Eshghdoost, A. Mashinchian

    2008-07-01

    Full Text Available The different methods are used for the removal of heavy metals as important contaminants in water and wastewater. Biosorption is an alternative to traditional physicochemical in removing toxic metals from wastewaters and groundwater resources. In this study biosorption of lead and chromium ions from solution was studied using Bacillus circulans isolated from Anzali wetland in batch and biofilter modes and optimum conditions were determined. The experimental results showed 900-950 mg/L and 1050-1100 mg/L, for minimum bactericidal concentration and minimum inhibitory concenteration for lead and chromium, respectively. Results of metal concentration in solution containing 500 mg/L in batch culture showed a reduction about 65% and 48% in five and four days for lead and chromium, respectively. The highest value of lead and chromium uptake in solution with 500 mg/L was 78% and 40% in biofilter mode, respectively. The biosorption of lead and chromium were increased up to pH=5.5, 6, 5.5 and 7, respectively. In the other hand, maximum sorption occurred at neutral pH. There was a significant decreasing of biosorption levels by lowering pH fewer than 3. Accumulation of lead and chromium was determined by scanning electron microscopy analysis of the biofilm exposed to 500 mg/L metal concentration. Based on this analysis, the highest metal concentrations were observed in regions with including bacteria.

  17. Biosorption studies on shelled Moringa oleifera seeds for chromium removal using radiotracer

    International Nuclear Information System (INIS)

    Sharma, Parul; Srivastava, M.M.; Prakash, Satya; Srivastava, Shalini

    2007-01-01

    Shelled Moringa oleifera seeds (SMOS) have been explored as an indigenous, inexpensive and effective sorbent for chromium removal from water bodies. Sorption studies (batch) result into the standardization of optimum conditions for removal of 81.02% Cr (III) and 88.15% Cr (VI) pH 6.5 and 2.5 respectively. Percent sorption in each case was computed on the basis of chromium estimation using planar NaI (TI) detector, coupled to 4K MCA (Canberra Accuspec Card with PC AT 386). (author)

  18. Removal of chromium (vi) by using eucalyptus bark (biosorption)

    International Nuclear Information System (INIS)

    Khatoon, S.; Anwar, J.; Fatima, H.B.

    2009-01-01

    Adsorption of Chromium (VI) on the Eucalyptus bark has been studied with variation in parameters. Different parameters like particle size of adsorbent, concentration of adsorbate, amount of adsorbent, stirring speed, time, temperature and pH were studied. The adsorption has been carried out in batch process. The adsorption capacity increases with decreasing the particle size of adsorbent. The optimum conditions for the maximum adsorption are attained with 2.0 g of adsorbent, 40 ppm metal ion concentration, at room temperature (10 degree C), with 90 min contact time, with 300 rpm agitation speed and at pH 2. (author)

  19. Chemical activation of tea waste and use for the removal of chromium (Vi) from aqueous solution

    International Nuclear Information System (INIS)

    Qureshi, K.; Bhatti, I.; Ansari, A.K.

    2009-01-01

    Tea waste is the residue left after the preparation of tea. At present the tea waste is regarded as a waste product having no use. In this study, tea waste is converted into an adsorbent. Tea waste is chemically activated with phosphoric acid at low temperature 450 degree C. This activated carbon is then utilized as an adsorbent for the removal of Chromium (VI) from aqueous solution. The various sorption parameters i.e pH, sorbent dose sorbate concentration, shaking time and shaking speed are first optimized. 75% of chromium from aqueous solution is effectively removed at pH 2. The best optimum conditions were obtained when 1 gm of sorbent was agitated at 100 rpm with 60 mg/l of sorbate for 50 minutes. Better results were obtained when low concentrations of sorbates were used. Hence tea waste could also be successfully used for the sorption of Chromium (VI), from industrial waste water. (author)

  20. Removal of Chromium (III from Water by Using Modified and Nonmodified Carbon Nanotubes

    Directory of Open Access Journals (Sweden)

    Muataz Ali Atieh

    2010-01-01

    Full Text Available This study was carried out to evaluate the environmental application of modified and nonmodified carbon nanotubes through the experiment removal of chromium trivalent (III from water. The aim was to find the optimal condition of the chromium (III removal from water under different treatment conditions of pH, adsorbent dosage, contact time and agitation speed. Multi wall carbon nanotubes (MW-CNTs were characterized by field emission scanning electron microscopy (FE-SEM and transmission electron microscopy (TEM. The diameter of the carbon nanotubes produced varied from 20–40 nm with average diameter of 24 nm and 10 micrometer in length. Adsorption isotherms were used to model the adsorption behavior and to calculate the adsorption capacity of the absorbents. The results showed that, 18% of chromium (III removal was achieved using modified carbon nanotubes (M-CNTs at pH 7, 150 rpm, and 2 hours for a dosage of 150 mg of CNTs. The removal of Cr (III is mainly attributed to the affinity of chromium (III to the physical and chemical properties of the CNTs. The adsorption isotherms plots were well fitted with experimental data.

  1. Removal and Recovery of Chromium from Solutions Simulating Tannery Wastewater by Strong Acid Cation Exchanger

    Directory of Open Access Journals (Sweden)

    Gulten Cetin

    2013-01-01

    Full Text Available The process in this study was conducted on removal of chromium(III in a solution simulating a typical spent chrome tanning bath by the resin having matrix of styrene-divinylbenzene-based macroporous sulphonate, Amberjet 1200Na. The column experiments were carried out with the bed volumes of the resin as 751 mL and 1016 mL for different installation systems of the laboratory-scale pilot plant. The feeding solutions in the bed volumes of 200 and 190 were used for each installation system. The regeneration behaviour of the resin was determined by using reverse regeneration procedure with the solution of hydrogen peroxide in alkaline. The regeneration kinetics of the exhausted resin was examined with a range of the solutions having different concentration series of the alkaline hydrogen peroxide. The solutions of the basic chromium sulphate were recycled for each installation system following the regeneration cycles. The chromium ions in effluent were quantitatively eluted, and satisfactory removal of chromium(III and recovery of chromium(VI were achieved.

  2. Sectional removable partial denture design for the treatment of ...

    African Journals Online (AJOL)

    Sectional removable partial denture design for the treatment of partial mandibulectomy patient: a case report. ... mandibulectomy with no surgical reconstruction. The case was challenging and the prosthesis was well tolerated during a 6 months follow-up review. (Afr. J. Biomed. Res. 10: 197 - 201). Keywords: Removable ...

  3. Using microalgae scenedesmus obliquus in the removal of chromium present in plating wastewaters

    International Nuclear Information System (INIS)

    Pellon, A.; Benitez, F.; Frades, J.; Garcia, L.; Cerpa, A.; Alguacil, F.

    2003-01-01

    Dumping wastewaters from plating industry with a high content in chromium is a potential hazard for people and environment. It is known that some metals, including the heavy metals, at low concentrations participate in different metabolic routes, but at high concentration are toxic for many living organisms. Some microorganism taking the heavy metals from the environment are capable of concentrating and accumulating large quantities of them in different citiplasmatic structures with no-toxic effects. Microalgaehave affinity by the polyvalent metals making possible their use as depollutant agent in waters that contains dissolved metallic ions as alternative methods when others methods of recycle are unusable. In this report a chromium removal study from a plating wastewater, using scenedesmus obliquus culture was made. The removal efficiency of Cr (VI) was 12% and Cr (III) was 27% and for condition of algae's immobilization removal of Cr (III) was 95%. (Author) 19 refs

  4. Sorption Capacity Measurement of Chlorella Vulgaris and Scenedesmus Acutus to Remove Chromium from Tannery Waste Water

    Science.gov (United States)

    Ardila, Liliana; Godoy, Rubén; Montenegro, Luis

    2017-08-01

    Tanning process is a polluting activity due to the release of toxic agents into the environment. One of the most important of those toxic chemicals is chromium. Different alternatives have been proposed for the removal of this metal from tanning waste water which include the optimization of the productive processes, physicochemical and biochemical waste water treatment. In this study, the biological adsorption process of trivalent chromium was carried out in synthetic water and tannery waste water through two types of native green microalgae, called Chlorella vulgaris and Scenedesmus acutus in Free State and immobilized in PVA state. This, considering that cellular wall of microalgae has functional groups like amines and carboxyl that might bind with trivalent chromium. Statistical significance of variables as pH temperature, chromium and algae concentrations was evaluated just like bio sorption capacity of different types of water and kind of bioadsorbent was calculated to determine if this process is a competitive solution comparing to other heavy metal removal processes.

  5. OPTIMIZATION OF NICKEL (II) AND CHROMIUM (III) REMOVAL ...

    African Journals Online (AJOL)

    HOD

    ... O. "Removal of nickel from wastewater using an agricultural adsorbent", Water SA, Vol. 37,. Number 1, pp 41-46, 2011. [5] Duran, C., Ozdes, D., Gundogdu, A. and Senturk, H. B.. "Kinetics and Isotherm Analysis of Basic Dyes. Adsorption onto Almond Shell (Prunus dulcis) as a. Low Cost Adsorbent", Journal of Chemical &.

  6. Hexavalent chromium removal using aerobic activated sludge batch ...

    African Journals Online (AJOL)

    The following Cr(VI) removal systems were tested: activated sludge alone; activated sludge with an external electron donor (5 g/. of lactose); activated sludge with PAC addition (4 g/.); activated sludge with both PAC and lactose; and PAC alone. The results reported here showed that activated sludges are capable of ...

  7. Removal of chromium and nickel ions from aqueous solution by ...

    African Journals Online (AJOL)

    EJIRO

    HCl modified adsorbent gave the best result for removal of Cr(VI) from synthetic industrial effluents. Keywords: Heavy metals, low cost ... tion, reverse osmosis and cementation. These methods are expensive and have the ... effective adsorbents for treatment of metal contaminated wastewaters are necessary particularly in ...

  8. Removal and transformation of hexavalent chromium in sequencing ...

    African Journals Online (AJOL)

    2011-04-07

    Apr 7, 2011 ... 1 January 2012. ISSN 1816-7950 (On-line) = Water SA Vol. 38 No. 1 January 2012. 9 ... Determination of Cr in the suspended sludge showed that around 95% of the Cr species were Cr(III). Determination of Cr concentration ... Conventional methods of removing Cr(VI) include chemical reduction to Cr(III) ...

  9. HEXAVALENT CHROMIUM REMOVAL FROM AQUEOUS SOLUTIONS BY PLEUROTUS OSTREATUS SPENT BIOMASS.

    OpenAIRE

    D.CAROL; S.J.Kingsley; .S.Vincent

    2012-01-01

    The Pleurotus ostreatus spent biomass after the harvest, is a waste which was used as a potential sorbent after coating it with chitosan an deacetylated derivative from chitin the most abundant carbohydratesecond to cellulose .The study is an attempt to elaborate and justify the optional utility of Spent Pleurotus ostreatus biomass for hexavalent chromium removal from aqueous industrial effluents. The effect of experimental parameters such as pH, biosorbent dosage, biosorbent dosage, initial ...

  10. Hexavalent chromium removal from aqueous solutions by a novel powder prepared from Colocasia esculenta leaves.

    Science.gov (United States)

    Nakkeeran, E; Saranya, N; Giri Nandagopal, M S; Santhiagu, A; Selvaraju, N

    2016-08-02

    In this study, batch removal of hexavalent chromium from aqueous solutions by powdered Colocasia esculenta leaves was investigated. Batch experiments were conducted to study the effects of adsorption of Cr(VI) at different pH values, initial concentrations, agitation speeds, temperatures, and contact times. The biosorbent was characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, and Fourier transform infrared spectrometer analysis. The biosorptive capacity of the adsorbent was dependent on the pH of the chromium solution in which maximum removal was observed at pH 2. The adsorption equilibrium data were evaluated for various adsorption isotherm models, kinetic models, and thermodynamics. The equilibrium data fitted well with Freundlich and Halsey models. The adsorption capacity calculated was 47.62 mg/g at pH 2. The adsorption kinetic data were best described by pseudo-second-order kinetic model. Thus, Colocasia esculenta leaves can be considered as one of the efficient and cheap biosorbents for hexavalent chromium removal from aqueous solutions.

  11. Hexavalent chromium removal by chitosan modified-bioreduced nontronite

    Science.gov (United States)

    Singh, Rajesh; Dong, Hailiang; Zeng, Qiang; Zhang, Li; Rengasamy, Karthikeyan

    2017-08-01

    Recent efforts have focused on structural Fe(II) in chemically or biologically reduced clay minerals to immobilize Cr(VI) from aqueous solution, but the coulombic repulsion between the negatively charged clay surface and the polyanionic form of Cr(VI), e.g., dichromate, can hinder the effectiveness of this process. The purpose of this study was to investigate the efficiency and mechanism of Cr(VI) removal by a charge-reversed nontronite (NAu-2), an Fe-rich smectite. Chitosan, a linear polysaccharide derived from chitin found in soil and groundwater, was used to reverse the charge of NAu-2. Intercalation of chitosan into NAu-2 interlayer increased the basal d-spacing of NAu-2 from 1.23 nm to 1.83 nm and zeta potential from -27.17 to +34.13 mV, with the amount of increase depending on chitosan/NAu-2 ratio. Structural Fe(III) in chitosan-exchanged NAu-2 was then biologically reduced by an iron-reducing bacterium Shewanella putrefaciens CN32 in bicarbonate buffer with lactate as the sole electron donor, with and without electron shuttle, AQDS. Without AQDS, the extent of Fe(III) reduction increased from the lowest (∼9%) for the chitosan-free NAu-2 to the highest (∼12%) for the highest chitosan loaded NAu-2 (3:1 ratio). This enhancement of Fe(III) reduction was likely due to the attachment of negatively charged bacterial cells to charge-reversed (e.g., positively charged) NAu-2 surfaces, facilitating the electron transfer between cells and structural Fe(III). With AQDS, Fe(III) reduction extent doubled relative to those without AQDS, but the enhancement effect was similar across all chitosan loadings, suggesting that AQDS was more important than chitosan in enhancing Fe(III) bioreduction. Chitosan-exchanged, biologically reduced NAu-2 was then utilized for removing Cr(VI) in batch experiments with three consecutive spikes of 50 μM Cr. With the first Cr spike, the rate of Cr(VI) removal by charged-reversed NAu-2 that was bioreduced without and with AQDS was ∼1

  12. Investigation of the removal of chromium (VI by Nanocomposites Chitosan-tragacanth solution from aqueous solution

    Directory of Open Access Journals (Sweden)

    Adel Almasi Nahnaji

    2016-03-01

    Full Text Available Background: The aim of this study was to investigate the removal of chromium (VI by Nanocomposites Chitosan-tragacanth solution from aqueous solution. Methods: In this study, chitosan-tragacanth nanocomposites were synthesized and analyzed by electron microscopy (SEM, (TEM and Fourier transform spectroscopy (FT-IR for the size and shape of the surface. The nano-composite of chitosan-tragacanth, for the adsorption of chromium (VI in aqueous solution was used as adsorbent. Results: The optimum conditions with multiple experiments to enhance the absorption were evaluated. The highest absorption of Cr (VI was occurred in the adsorbent dosage of 0.2 g, 8 ppm concentration of chromium ions, the pH=6 and also retention time of 50 min; in 298 ˚K temperature. After determining optimal conditions of adsorption, isotherms equations and study and thermodynamic parameters were applied. Adsorption process of chromium (VI on nano-composite chitosan - Tragacanth was conformed with Temkin isotherm. Conclusion: The thermodynamic parameters such as standard Gibbs free energy changes, changes in enthalpy and entropy changes in the standard showed that the adsorption process of Cr (VI is spontaneous and heating, and kinetics studies of models Lagergren, Ho , Alovich and intraparticle is used, the results show that the adsorption kinetics follows the pseudo-second order.

  13. The Use of Implants to Improve Removable Partial Denture Function

    OpenAIRE

    Pimentel, Marcele Jardim; Arréllaga, Juan Pablo; Bacchi, Ataís; Del Bel Cury, Altair A.

    2013-01-01

    The oral rehabilitation with conventional removable partial dentures in Kennedy class I patients allows continuous bone resorption, dislodgment of the prosthesis during the mastication caused by the resilience of the mucosa, and rotation of the prosthesis. Thus, the associations of distal implants become an attractive modality of treatment for these patients. This case report presented an association of removable partial dentures, milled crowns and osseointegrated implants to rehabilitate a p...

  14. Trivalent chromium removal from aqueous solutions by a sol–gel synthesized silica adsorbent functionalized with sulphonic acid groups

    Energy Technology Data Exchange (ETDEWEB)

    Gomez-Gonzalez, Sergio Efrain [Departamento de Ingeniería Química, Universidad de Guadalajara, Blvd. Marcelino García Barragán # 1421, esq. Calzada Olímpica, C.P. 44430 Guadalajara, Jalisco (Mexico); Carbajal-Arizaga, Gregorio Guadalupe [Departamento de Química, CUCEI, Universidad de Guadalajara, Blvd. Marcelino García Barragán # 1421, esq. Calzada Olímpica, C.P. 44430 Guadalajara, Jalisco (Mexico); Manriquez-Gonzalez, Ricardo [Departamento de Madera, Celulosa y Papel, CUCEI, Universidad de Guadalajara, Km 15.5, carretera Guadalajara-Nogales, Las Agujas, C.P. 45020 Zapopan, Jalisco (Mexico); De la Cruz-Hernandez, Wencel [Centro de Nanociencias y Nanotecnología, Universidad Nacional Autónoma de México, Km 107 carretera Tijuana-Ensenada, C.P. 22830 Ensenada, Baja California (Mexico); Gomez-Salazar, Sergio, E-mail: sergio.gomez@cucei.udg.mx [Departamento de Ingeniería Química, Universidad de Guadalajara, Blvd. Marcelino García Barragán # 1421, esq. Calzada Olímpica, C.P. 44430 Guadalajara, Jalisco (Mexico)

    2014-11-15

    Highlights: • Corpuscular sulphonic acid-functionalized silica holds improved uptake of chromium. • Mesopores on adsorbent facilitate (CH{sub 3}COO){sub 2}Cr{sup +} ion uptake on sulphonate sites. • Formation of chromium acetate sulphonate complex proposed from XPS results. • Fixed bed chromium uptake results suggest potential industrial use. - Abstract: A high capacity hybrid silica adsorbent was synthesized via sol–gel processing with sulphonic acid groups as trivalent chromium complex ions chelators from aqueous solutions. The synthesis included co-condensation of tetraethoxysilane (TEOS) with 3-(mercaptopropyl)trimethoxysilane (MPS), and oxidation of thiol to sulphonic acid groups. Chromium uptake kinetic, batch and fixed-bed experiments were performed to assess the removal of this metal from aqueous solutions. {sup 13}C, {sup 29}Si CPMAS NMR, FTIR, XPS were used to characterize the adsorbent structure and the nature of chromium complexes on the adsorbent surface. Chromium maximum uptake was obtained at pH 3 (72.8 mg/g). Elemental analysis results showed ligand density of 1.48 mmol sulphonic groups/g. About 407 mL of Cr(III) solution (311 mg/L) were treated to breakthrough point reaching ≤0.06 mg/L at the effluent. These results comply with USEPA regulation for chromium concentration in drinking water (≤0.1 mg/L). The adsorbent shows potential to be used in chromium separations to the industrial level.

  15. Clinical evaluation of failures in removable partial dentures.

    Science.gov (United States)

    Jorge, Janaina H; Quishida, Cristiane C C; Vergani, Carlos E; Machado, Ana L; Pavarina, Ana C; Giampaolo, Eunice T

    2012-01-01

    The aim of this clinical study was to evaluate the effects of removable partial dentures on the support tissues and changes occurring in lower tooth-supported and bilateral distal-extension dentures, 5 years after placement. The study involved analysis of a total of 53 patients who received prosthetic treatment for removable partial dentures. The patients were divided into two groups. In group 1, the patients had a completely edentulous maxilla and an edentulous area with natural teeth remaining in both the anterior and posterior regions. In group 2, the patients had a completely edentulous maxilla and partially edentulous mandible with preserved anterior teeth. Tooth mobility, prevalence of caries, fracture of the abutment teeth, fracture and/or deformation of the removable partial denture components and stability of the denture base were evaluated. The use of a removable partial denture increased tooth mobility, reduced the prevalence of caries, and did not cause loss or fracture of the abutments or damage to their components, when compared with the baseline. It was concluded that there was no difference between the groups as evaluated in terms of tooth mobility, prevalence of caries, loss and fracture of the abutments or damage to the components of the removable partial denture.

  16. Comparative clinical evaluation of removable partial dentures made of two different materials in Kennedy Applegate class II partially edentulous situation.

    Science.gov (United States)

    Hundal, Maninder; Madan, Rajesh

    2015-12-01

    Cast Chromium Cobalt alloy has been the material of choice for fabricating Removable Partial Dentures (RPDs) but has certain drawbacks. Newer materials like the flexible Nylon based Super Polyamide have been introduced to overcome these drawbacks. The present study has compared the above two materials for nine clinical parameters. The study was carried out on 30 patients presenting with a Kennedy Applegate class II partially edentulous situation who were divided into two equal groups and clinically assessed. Statistically significant results were obtained in favor of flexible RPDs, in the parameters of 'aesthetics' and 'overall patient satisfaction'. Both groups showed more or less similar values for 'frequency of fracture of the prosthesis during usage' with the incidence being slightly higher for patients wearing the cast RPDs. The clinical parameters of 'oral soft tissue tolerance', 'gingival health', 'periodontal health' and 'adaptability in areas with undercut' were statistically at par for all the 30 patients thus suggesting the comparable biocompatibility of the two materials. The highlight of this study was the relative ease in fabrication of the flexible RPDs as compared to the cast RPDs. Based on the favorable clinical results of this study, it can be summarized that the flexible RPDs is a viable alternative to cast RPDs in Kennedy Applegate class II partially edentulous situation in the short term.

  17. Box-Behnken experimental design for chromium(VI) ions removal by bacterial cellulose-magnetite composites.

    Science.gov (United States)

    Stoica-Guzun, Anicuta; Stroescu, Marta; Jinga, Sorin Ion; Mihalache, Nicoleta; Botez, Adriana; Matei, Cristian; Berger, Daniela; Damian, Celina Maria; Ionita, Valentin

    2016-10-01

    In this study bacterial cellulose-magnetite composites were synthesised for the removal of chromium(VI) from aqueous solutions. Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), thermogravimetric analysis and X-ray Photoelectron Spectroscopy (XPS) were used to characterize the bacterial cellulose-magnetite composites and to reveal the uniform dispersion of nanomagnetite in the BC matrix. Magnetic properties were also measured to confirm the magnetite immobilization on bacterial cellulose membrane. The effects of initial Cr(VI) concentration, solution pH and solid/liquid ratio upon chromium removal were examined using the statistical Box-Behnken Design. Because of the possibility of magnetite dissolution during chromium(VI) adsorption, the degree of iron leaching was also analysed in the same conditions as Cr(VI) adsorption. From the factors affecting chromium(VI) adsorption the most important was solution pH. The highest Cr(VI) removal efficiency was observed at pH 4, accompanied by the lowest iron leaching in the solution. The adsorption experiments also indicated that the adsorption process of chromium(VI) is well described by Freundlich adsorption model. Our results proved that the BC-magnetite composites could be used for an efficient removal of chromium(VI) from diluted solutions with a minimum magnetite dissolution during operation. Copyright © 2016 Elsevier B.V. All rights reserved.

  18. Flexible Thermoplastic Denture Base Materials for Aesthetical Removable Partial Denture Framework

    OpenAIRE

    Singh, Kunwarjeet; Aeran, Himanshu; Kumar, Narender; Gupta, Nidhi

    2013-01-01

    Conventional fixed partial dentures, implant supported Fixed Partial Dentures (FDPs) and removable partial dentures are the most common treatment modalities for the aesthetic and functional rehabilitation of partially edentulous patients. Although implants and FDP have certain advantages over removable partial dentures, in some cases, removable partial dentures may be the only choice which is available. Removable cast partial dentures are used as definitive removable prostheses when indicated...

  19. Synthetically modified nano-cellulose for the removal of chromium: a green nanotech perspective.

    Science.gov (United States)

    Jain, Priyanka; Varshney, Shilpa; Srivastava, Shalini

    2017-02-01

    Existing processes for the decontamination of heavy metals from water are found to be cost-prohibitive and energy-intensive which is totally against the sustainable concept of development. Green nanotechnology for water purification for ecosystem management, agricultural and industry is an emerging as leading global priority and occupies better position over the current state of water purification. Herein, the diafunctionalised polyaniline modified nanocellulose composite sorbent (PANI-NCC) has been used to introduce amine and imine functionalities for the removal of trivalent and hexavalent chromium from water bodies. The fabricated nanobiomaterial has been authenticated by modern spectroscopic, microscopic techniques. The modified PANI-NCC is rod-like in shape, ~60 nm in size. The roughness and crystallinity index is also quantified and found to be 49.67 nm and 84.18%, respectively. The optimised experimental finding provides the efficient removal of trivalent [Cr(III)] (47.06 mg/g; 94.12%) and hexavalent [Cr(VI)] (48.92 mg/g; 97.84%) chromium from synthetic waste water. The fabricated nano biosorbent is deemed to be a potent biosorbent for technological development to remove the toxic metals in the real environmental water samples.

  20. Modacrylic anion-exchange fibers for Cr(VI) removal from chromium-plating rinse water in batch and flow-through column experiments.

    Science.gov (United States)

    Lee, Seung-Chan; Kang, Jin-Kyu; Sim, Eun-Hye; Choi, Nag-Choul; Kim, Song-Bae

    2017-11-10

    The aim of this study was to investigate Cr(VI) removal from chromium-plating rinse water using modacrylic anion-exchange fibers (KaracaronTM KC31). Batch experiments were performed with synthetic Cr(VI) solutions to characterize the KC31 fibers in Cr(VI) removal. Cr(VI) removal by the fibers was affected by solution pH; the Cr(VI) removal capacity was the highest at pH 2 and decreased gradually with a pH increase from 2 to 12. In regeneration and reuse experiments, the Cr(VI) removal capacity remained above 37.0 mg g -1 over five adsorption-desorption cycles, demonstrating that the fibers could be successfully regenerated with NaCl solution and reused. The maximum Cr(VI) removal capacity was determined to be 250.3 mg g -1 from the Langmuir model. In Fourier-transform infrared spectra, a Cr = O peak newly appeared at 897 cm -1 after Cr(VI) removal, whereas a Cr-O peak was detected at 772 cm -1 due to the association of Cr(VI) ions with ion-exchange sites. X-ray photoelectron spectroscopy analyses demonstrated that Cr(VI) was partially reduced to Cr(III) after the ion exchange on the surfaces of the fibers. Batch experiments with chromium-plating rinse water (Cr(VI) concentration = 1178.8 mg L -1 ) showed that the fibers had a Cr(VI) removal capacity of 28.1-186.4 mg g -1 under the given conditions (fiber dose = 1-10 g L -1 ). Column experiments (column length = 10 cm, inner diameter = 2.5 cm) were conducted to examine Cr(VI) removal from chromium-plating rinse water by the fibers under flow-through column conditions. The Cr(VI) removal capacities for the fibers at flow rates of 0.5 and 1.0 mL min -1 were 214.8 and 171.5 mg g -1 , respectively. This study demonstrates that KC31 fibers are effective in the removal of Cr(VI) ions from chromium-plating rinse water.

  1. Removal and Recovery of Chromium from Solutions Simulating Tannery Wastewater by Strong Acid Cation Exchanger

    OpenAIRE

    Cetin, Gulten; Kocaoba, Sevgi; Akcin, Goksel

    2013-01-01

    The process in this study was conducted on removal of chromium(III) in a solution simulating a typical spent chrome tanning bath by the resin having matrix of styrene-divinylbenzene-based macroporous sulphonate, Amberjet 1200Na. The column experiments were carried out with the bed volumes of the resin as 751 mL and 1016 mL for different installation systems of the laboratory-scale pilot plant. The feeding solutions in the bed volumes of 200 and 190 were used for each installation system. The ...

  2. Removal of hexavalent chromium upon interaction with biochar under acidic conditions: mechanistic insights and application.

    Science.gov (United States)

    Choudhary, Bharat; Paul, Debajyoti; Singh, Abhas; Gupta, Tarun

    2017-07-01

    Chromium pollution of soil and water is a serious environmental concern due to potential carcinogenicity of hexavalent chromium [Cr(VI)] when ingested. Eucalyptus bark biochar (EBB), a carbonaceous black porous material obtained by pyrolysis of biomass at 500 °C under oxygen-free atmosphere, was used to investigate the removal of aqueous Cr(VI) upon interaction with the EBB, the dominant Cr(VI) removal mechanism(s), and the applicability to treat Cr(VI)-contaminated wastewater. Batch experiments showed complete removal of aqueous Cr(VI) at pH 1-2; sorption was negligible at pH 1, but ~55% of total Cr was sorbed onto the EBB surface at pH 2. Detailed investigations on unreacted and reacted EBB through Fourier transform infrared spectroscopy and X-ray photoelectron spectrometry (XPS) indicate that the carboxylic groups in biochar played a dominant role in Cr(VI) sorption, whereas the phenolic groups were responsible for Cr(VI) reduction. The predominance of sorption-reduction mechanism was confirmed by XPS studies that indicated ~82% as Cr(III) and ~18% as Cr(VI) sorbed on the EBB surface. Significantly, Cr(VI) reduction was also facilitated by dissolved organic matter (DOM) extracted from biochar. This reduction was enhanced by the presence of biochar. Overall, the removal of Cr(VI) in the presence of biochar was affected by sorption due to electrostatic attraction, sorption-reduction mediated by surface organic complexes, and aqueous reduction by DOM. Relative dominance of the aqueous reduction mechanism depended on a critical biochar dosage for a given electrolyte pH and initial Cr(VI) concentration. The low-cost EBB developed here successfully removed all Cr(VI) in chrome tanning acidic wastewater and Cr(VI)-contaminated groundwater after pH adjustment, highlighting its potential applicability in effective Cr(VI) remediation.

  3. Implant-supported removable partial dentures in the mandible

    NARCIS (Netherlands)

    Louwerse, Charlotte

    2017-01-01

    Conventional removable partial dentures (RPD) in a free-ending situation in the lower jaw (i.e. only front teeth left) have a poor reputation. Several problems like discomfort and functional problems are frequently encountered, resulting in dissatisfied patients and desperate dentists. By supporting

  4. Acceptability of maxillary major connectors in removable partial ...

    African Journals Online (AJOL)

    Conclusions: The metal bar major connector was the most acceptable maxillary major connector while acrylic resin plate was more acceptable than metal plate maxillary major connector. It also confirmed the influence of connector design on patient acceptance of removable partial denture. African Health Sciences Vol.

  5. Comparative analysis of unilateral removable partial denture and classical removable partial denture by using finite element method

    Directory of Open Access Journals (Sweden)

    Radović Katarina

    2010-01-01

    Full Text Available Introduction. Various mobile devices are used in the therapy of unilateral free-end saddle. Unilateral dentures with precise connectivity elements are not used frequently. In this paper the problem of applying and functionality of unilateral freeend saddle denture without major connector was taken into consideration. Objective. The aim was to analyze and compare a unilateral RPD (removable partial denture and a classical RPD by calculating and analyzing stresses under different loads. Methods. 3D models of unilateral removable partial denture and classical removable partial denture with casted clasps were made by using computer program CATIA V5 (abutment teeth, canine and first premolar, with crowns and abutment tissues were also made. The models were built in full-scale. Stress analyses for both models were performed by applying a force of 300 N on the second premolar, a force of 500 N on the first molar and a force of 700 N on the second molar. Results. The Fault Model Extractor (FME analysis and calculation showed the complete behavior of unilateral removable partial denture and abutments (canine and first premolar, as well as the behavior of RPD under identical loading conditions. Applied forces with extreme values caused high stress levels on both models and their abutments within physiological limits. Conclusion. Having analyzed stresses under same conditions, we concluded that the unilateral RPD and classical RPD have similar physiological values.

  6. On the removal of hexavalent chromium from a Class F fly ash.

    Science.gov (United States)

    Huggins, F E; Rezaee, M; Honaker, R Q; Hower, J C

    2016-05-01

    Coarse and fine samples of a Class F fly ash obtained from commercial combustion of Illinois bituminous coal have been exposed to two long-term leaching tests designed to simulate conditions in waste impoundments. ICP-AES analysis indicated that the coarse and fine fly ash samples contained 135 and 171mg/kg Cr, respectively. Measurements by XAFS spectroscopy showed that the ash samples originally contained 5 and 8% of the chromium, respectively, in the hexavalent oxidation state, Cr(VI). After exposure to water for more than four months, the percentage of chromium as Cr(VI) in the fly-ash decreased significantly for the coarse and fine fly-ash in both tests. Combining the XAFS data with ICP-AES data on the concentration of chromium in the leachates indicated that, after the nineteen-week-long, more aggressive, kinetic test on the coarse fly ash, approximately 60% of the Cr(VI) had been leached, 20% had been reduced to Cr(III) and retained in the ash, and 20% remained as Cr(VI) in the ash. In contrast, during the six-month-long baseline test, very little Cr was actually leached from either the coarse or the fine fly-ash (ash was retained in the ash in that form, while the remainder, 34% and 80%, respectively, was reduced and retained in the ash as Cr(III). The results are interpreted as indicating that Cr(VI) present in Class F fly-ash can be reduced to Cr(III) when in contact with water and that such chemical reduction can compete with physical removal of Cr(VI) from the ash by aqueous leaching. Copyright © 2016 Elsevier Ltd. All rights reserved.

  7. Clinical evaluation of isolated abutment teeth in removable partial dentures

    Directory of Open Access Journals (Sweden)

    Zarrati S

    2011-02-01

    Full Text Available "nBackground and Aims: Nowadays, removable partial dentures are applied to patients who are not able to use dental implants or fixed prosthesis. Although based on the studies the users of removable partial dentures are in the risk of plaque accumulation and unacceptable changes such as gingivitis, periodontitis and mobility in abutment tooth. It is not clear whether the negative effects of removable partial dentures are more on the isolated teeth which are a kind of abutment adjacent to endentulous area in both sides. The purpose of this study was to investigate the clinical condition of isolated abutment teeth without splinting in comparison to control abutment from the aspects of B.O.P (bleeding on probing, mobility, pocket depth and gingivitis."nMaterials and Methods: In this cross-sectional study, the prepared questionnaires were filled out by 50 patients who received removable partial dentures in department of removable prosthodontics of dental school of Tehran University of Medical Sciences. The patients had isolated abutment tooth and did not have any systemic disease. The obtained data were analyzed. Using Wilcoxon, exact Fisher and Kruskal-Wallis test."nResults: B.O.P (P=0.004, pocket depth (P=0.035, and mobility (P<0.001 in isolated abutments were more than those in control abutments, but there were not significant differences in the degree of caries (P=0.083 and gingivitis (P=0.07."nConclusion: This study showed that clinical condition of isolated abutments is worse than that of control abutments. More attention should be paid to healthiness of isolated teeth without splinting and periodic follow ups should be done in these cases.

  8. [Treatment of tannery wastewater by infiltration percolation: chromium removal and speciation in soil].

    Science.gov (United States)

    Tiglyene, S; Jaouad, A; Mandi, L

    2008-06-01

    The aim of this paper was, on one hand, to study the treatment of raw tannery effluent by infiltration percolation system and, on the other hand, to determine the distribution and speciation of chromium in the used soil. The system pilot consisted of columns filled to 15 cm of gravel and 60 cm of soil (88% of sand). The columns irrigated by raw tannery wastewater with a daily hydraulic load of 5 cm per day (approximately 10 L every day). The water flowed vertically through the soil. The speciation of Cr was investigated by using selective five steps sequential extraction method. The results indicated that the pH of the treated wastewater increases by three units in comparison to the raw wastewater. The electrical conductivity of the effluent increases also after treatment. Over the whole experimental period, results revealed significant performances of infiltration percolation system for organic load reduction. The mean elimination rate was 74% for total COD. In addition, there was a significant accumulation of organic carbon (62%) in the surface strata for the system. The total chromium undergoes an overall removal of 98%. After seven months of experiment, the results indicated that the whole retention of Cr occurring in the surface horizon of the soil (69%). Furthermore, the speciation study of Cr in the soil revealed that the oxidizable fraction is the most represented 55%. The reducible and residual phases represent 17.5% and 18.5%, respectively. The carbonate fraction presented 9% while exchangeable fraction presented only 0.02%.

  9. TREATABILITY TEST REPORT FOR THE REMOVAL OF CHROMIUM FROM GROUNDWATER AT 100-D AREA USING ELECTROCOAGULATION

    Energy Technology Data Exchange (ETDEWEB)

    PETERSEN SW

    2009-09-24

    The U.S. Department of Energy (DOE) has committed to accelerate cleanup of contaminated groundwater along the Columbia River. The current treatment approach was driven by a series of Interim Action Records of Decision (IAROD) issued in the mid-1990s. Part of the approach for acceleration involves increasing the rate of groundwater extraction for the chromium plume north of the 100-D Reactor and injecting the treated water in strategic locations to hydraulically direct contaminated groundwater toward the extraction wells. The current treatment system uses ion exchange for Cr(VI) removal, with off-site regeneration of the ion exchange resins. Higher flow rates will increase the cost and frequency of ion exchange resin regeneration; therefore, alternative technologies are being considered for treatment at high flow rates. One of these technologies, electrocoagulation (EC), was evaluated through a pilot-scale treatability test. The primary purpose of the treatability study was to determine the effectiveness of Cr(VI) removal and the robustness/implementability of an EC system. Secondary purposes of the study were to gather information about derivative wastes and to obtain data applicable to scaling the process from the treatability scale to full-scale. The treatability study work plan identified a performance objective and four operational objectives. The performance objective for the treatability study was to determine the efficiency (effectiveness) of hexavalent chromium removal from the groundwater, with a desired concentration of {le} 20 micrograms per liter ({micro}g/L) Cr(VI) in the effluent prior to re-injection. Influent and effluent total chromium and hexavalent chromium data were collected using a field test kit for multiple samples per week, and from off-site laboratory analysis of samples collected approximately monthly. These data met all data quality requirements. Two of three effluent chromium samples analyzed in the off-site (that is, fixed) laboratory

  10. Chromium removal from water by activated carbon developed from waste rubber tires.

    Science.gov (United States)

    Gupta, Vinod Kumar; Ali, Imran; Saleh, Tawfik A; Siddiqui, M N; Agarwal, Shilpi

    2013-03-01

    Because of the continuous production of large amount of waste tires, the disposal of waste tires represents a major environmental issue throughout the world. This paper reports the utilization of waste tires (hard-to-dispose waste) as a precursor in the production of activated carbons (pollution-cleaning adsorbent). In the preparation of activated carbon (AC), waste rubber tire (WRT) was thermally treated and activated. The tire-derived activated carbon was characterized by means of scanning electron microscope, energy-dispersive X-ray spectroscopy, FTIR spectrophotometer, and X-ray diffraction. In the IR spectrum, a number of bands centred at about 3409, 2350, 1710, 1650, and 1300-1000 cm(-1) prove the present of hydroxyl and carboxyl groups on the surface of AC in addition to C═C double bonds. The developed AC was tested and evaluated as potential adsorbent removal of chromium (III). Experimental parameters, such as contact time, initial concentration, adsorbent dosage and pH were optimized. A rapid uptake of chromium ions was observed and the equilibrium is achieved in 1 h. It was also found that the adsorption process is pH dependent. This work adds to the global discussion of the cost-effective utilization of waste rubber tires for waste water treatment.

  11. Removal of Hexavalent Chromium from Aqueous Solutions Using Magnetic Nanoparticles Coated with Alumina and Modified by Cetyl Trimethyl Ammonium Bromide

    Directory of Open Access Journals (Sweden)

    Mohammad Malakootian

    2015-12-01

    Full Text Available Introduction: The development of an effective method regarding chromium removal from the environment is of great importance. Therefore, the present study aimed to examiner magnetic nanoparticles coated with alumina modified by Cetyl Trimethyl Ammonium Bromide (CTAB in the removal of Cr6+ through magnetic solid phase extraction method. Materials & Methods: At first, iron oxide nanoparticles were synthesized, coated with alumina, modified with CTAB and characterized with suitable instruments. The factors affecting the process of chromium removal were investigated, including the concentration of CTAB, the pH, the amount of nanoparticles, the sample volume, a proper eluent, the adsorption and desorption time, and the effect of interfering ions. Moreover, the chromium concentration was determined by flame atomic absorption spectrometric (FAAS technique. The adsorption isotherm, adsorption capacity, and recoverability of the adsorbent were further examined. Results: The modified magnetic nanoparticles were demonstrated to be homogeneous, spherical, with a size lower than 20 nanometer having a magnetic property. The optimal conditions for chromium removal entailed 7*10-6 mol/L concentration of CTAB, pH range of 6-8, 0.1 g of the nanoparticles, 10 mL volume of the chromium sample (5 &mug mL-1, nitric acid 2 M as a suitable eluent, 15 minutes of adsorption and desorption, and no interference of interfering ions in the process of chromium separation. The process efficiency under optimal conditions was determined to be over 95%, which this process followed the Langmuir adsorption isotherm. The adsorption capacity proved to be 23.8 mg/g. Reusing after four times of adsorbent recovering was effective in the chromium removal (80%. The method accuracy for five measurement times was 4.155% and the method’s LOD was 0.081 mg/L. Conclusion: The method enjoys the benefits of convenient preparation of the adsorbent, high selectivity, high accuracy, short process

  12. Use of flying ash in the chromium removal (III) of the liquid effluents of tanneries

    International Nuclear Information System (INIS)

    Gil Pavas, Edison; Saldarriaga Molina, Carlos

    1998-01-01

    This study describes a simple and economic method for the removal of chromium (III) from tannery waste waters using flying ash. The process is carried out batch-wise utilizing as variables the mass of flying ash, the time of contact and the temperature or pH. With these variables a Box-Wilson type of experimental design was done, which was then optimized with a statistical program. One as-received flying ash was utilized in the work as well as another one chemically treated. The results show the possibility of lowering the initial concentration in the waste liquor from 1850 ppm to 0,008, complying this way with environmental exigencies about this contaminant

  13. The Survey of Melia Azaderach L. ash in Removal of Hexavalent Chromium from Synthetic Electroplating Industry Wastewater

    Directory of Open Access Journals (Sweden)

    MT Ghaneian

    2014-11-01

    Conclusion: Melia azedarach ash is an effective adsorbent in removal of hexavalent chromium from synthetic electroplating industries wastewater. In addition, the use of this biosorbent in preparation and application aspects is simple and cheap compared to many other natural and man-made adsorbent.

  14. Chromium (VI) biosorption and removal of chemical oxygen demand by Spirulina platensis from wastewater-supplemented culture medium.

    Science.gov (United States)

    Magro, Clinei D; Deon, Maitê C; De Rossi, Andreia; Reinehr, Christian O; Hemkemeier, Marcelo; Colla, Luciane M

    2012-01-01

    The inappropriate discharge of wastewater containing high concentrations of toxic metals is a serious threat to the environment. Given that the microalga Spirulina platensis has demonstrated a capacity for chromium VI (Cr (VI) biosorption, we assessed the ideal concentration of chromium-containing wastewater required for maximum removal of Cr (VI) and chemical oxygen demand (COD) from the environment by using this microalga. The Paracas and Leb-52 strains of S. platensis, with initial wastewater concentrations of 0%, 12.5%, 25%, and 50%, were cultured in Zarrouk medium diluted to 50% under controlled air, temperature, and lighting conditions. The cultures were maintained for 28 days, and pH, biomass growth, COD, and Cr (VI) were assessed. The wastewater concentration influenced microalgal growth, especially at high concentrations. Removal of 82.19% COD and 60.92% Cr (VI) was obtained, but the COD removal was greater than the Cr (VI) removal in both strains of S. platensis.

  15. Ultra-trace recognition and removal of toxic chromium (VI) ions from water using visual mesocaptor.

    Science.gov (United States)

    Shenashen, Md A; Shahat, A; El-Safty, Sherif A

    2013-01-15

    The key to designing optical mesocaptors is to construct a chromogenic receptor, namely, diphenylcarbazide (DPC), as a nanoscale platform scavenger with different functional characteristics, such as density, accessibility, and intrinsic mobility. Engineering of optical captors allows facile and reliable signaling in continuous monitoring modes, and enables simple and high-speed removal of toxic chromium (VI) ions. Mesoporous aluminosilica monoliths, with unique morphologies, active surface sites, and physical properties, enhance sensing/removal characteristics in terms of sensitivity, selectivity, and response time. The systematic design of optical mesocaptor is based on a densely patterned selective binding site (DPC) in engineered mesocylinder carriers that have multidirectional pores and microsized particle-like monoliths to control the adsorption/detection assays of Cr(VI) ions. Synthetic mesocaptor can be used for visual removal of Cr(VI) ions even at low concentration levels of 10(-10)M (i.e., 0.07 ppb) with rapid response time in minutes. Moreover, these new classes of design-made hybrid mesocaptor exhibit long-term signaling stability and recognition functionalities that provided extraordinary sensitivity, selectivity, reusability, and fast kinetic detection and quantification of various deleterious metal ions in the environment. Copyright © 2012 Elsevier B.V. All rights reserved.

  16. Chromium(VI Removal from Aqueous Solution by Magnetite Coated by a Polymeric Ionic Liquid-Based Adsorbent

    Directory of Open Access Journals (Sweden)

    Thania Alexandra Ferreira

    2017-05-01

    Full Text Available An evaluation of the chromium(VI adsorption capacity of four magnetite sorbents coated with a polymer phase containing polymethacrylic acid or polyallyl-3-methylimidazolium is presented. Factors that influence the chromium(VI removal such as solution pH and contact time were investigated in batch experiments and in stirred tank reactor mode. Affinity and rate constants increased with the molar ratio of the imidazolium. The highest adsorption was obtained at pH 2.0 due to the contribution of electrostatic interactions.

  17. Factors influencing the provision of removable partial dentures by dentists in Ireland.

    Science.gov (United States)

    Allen, Finbarr

    2010-01-01

    Factors influencing clinical treatment of partially dentate patients are varied, and there is a need to identify factors influencing success in the provision of removable partial dentures. The aim of this study was to assess the attitudes of general dental practitioners (GDPs) in Ireland towards tooth replacement and use of RPDs, in partially dentate older adults. The sample frame was the Register of Dentists in Ireland; data were also collected from a sample of dentists practising under NHS regulations in Northern Ireland. Validated questionnaires were sent to all dentists on the Register of Dentists in the Republic of Ireland, and dentists working under NHS regulations registered with the Central Services Agency in Northern Ireland. Content of the questionnaire included details of the dentist themselves, their dental practice and the profile of partial denture provision. They were also asked to give their views on factors influencing the success or failure of an RPD, the process of providing RPDs and their attitudes to RPD provision. A total of 1,143 responses were received, a response rate of 45%. A mean number of 61 RPDs per annum were provided, with 75% of dentures provided being acrylic based. Respondents indicate their belief that cobalt-chromium based dentures had a longer prognosis than acrylic dentures, but less than half (46%) claim to design the frameworks themselves. Patients' attitudes are considered influential in the success of RPD provision, and their influence on appearance is considered the most important factor influencing success. The most important factors influencing failure are: the patient not requesting a denture; an RPD restoring unbounded saddles; and, lower RPDs. Although considered important, approximately 60% of the sample do not routinely organise follow-up appointments for patients provided with RPDs. The fee structures in the DTSS and DTBS are considered a barrier to quality in the provision of partial dentures.

  18. Factors influencing the provision of removable partial dentures by dentists in Ireland.

    LENUS (Irish Health Repository)

    Allen, Finbarr

    2011-03-15

    Factors influencing clinical treatment of partially dentate patients are varied, and there is a need to identify factors influencing success in the provision of removable partial dentures. The aim of this study was to assess the attitudes of general dental practitioners (GDPs) in Ireland towards tooth replacement and use of RPDs, in partially dentate older adults. The sample frame was the Register of Dentists in Ireland; data were also collected from a sample of dentists practising under NHS regulations in Northern Ireland. Validated questionnaires were sent to all dentists on the Register of Dentists in the Republic of Ireland, and dentists working under NHS regulations registered with the Central Services Agency in Northern Ireland. Content of the questionnaire included details of the dentist themselves, their dental practice and the profile of partial denture provision. They were also asked to give their views on factors influencing the success or failure of an RPD, the process of providing RPDs and their attitudes to RPD provision. A total of 1,143 responses were received, a response rate of 45%. A mean number of 61 RPDs per annum were provided, with 75% of dentures provided being acrylic based. Respondents indicate their belief that cobalt-chromium based dentures had a longer prognosis than acrylic dentures, but less than half (46%) claim to design the frameworks themselves. Patients\\' attitudes are considered influential in the success of RPD provision, and their influence on appearance is considered the most important factor influencing success. The most important factors influencing failure are: the patient not requesting a denture; an RPD restoring unbounded saddles; and, lower RPDs. Although considered important, approximately 60% of the sample do not routinely organise follow-up appointments for patients provided with RPDs. The fee structures in the DTSS and DTBS are considered a barrier to quality in the provision of partial dentures.

  19. Factors influencing the provision of removable partial dentures by dentists in Ireland.

    LENUS (Irish Health Repository)

    Allen, Finbarr

    2010-10-01

    Factors influencing clinical treatment of partially dentate patients are varied, and there is a need to identify factors influencing success in the provision of removable partial dentures. The aim of this study was to assess the attitudes of general dental practitioners (GDPs) in Ireland towards tooth replacement and use of RPDs, in partially dentate older adults. The sample frame was the Register of Dentists in Ireland; data were also collected from a sample of dentists practising under NHS regulations in Northern Ireland. Validated questionnaires were sent to all dentists on the Register of Dentists in the Republic of Ireland, and dentists working under NHS regulations registered with the Central Services Agency in Northern Ireland. Content of the questionnaire included details of the dentist themselves, their dental practice and the profile of partial denture provision. They were also asked to give their views on factors influencing the success or failure of an RPD, the process of providing RPDs and their attitudes to RPD provision. A total of 1,143 responses were received, a response rate of 45%. A mean number of 61 RPDs per annum were provided, with 75% of dentures provided being acrylic based. Respondents indicate their belief that cobalt-chromium based dentures had a longer prognosis than acrylic dentures, but less than half (46%) claim to design the frameworks themselves. Patients\\' attitudes are considered influential in the success of RPD provision, and their influence on appearance is considered the most important factor influencing success. The most important factors influencing failure are: the patient not requesting a denture; an RPD restoring unbounded saddles; and, lower RPDs. Although considered important, approximately 60% of the sample do not routinely organise follow-up appointments for patients provided with RPDs. The fee structures in the DTSS and DTBS are considered a barrier to quality in the provision of partial dentures.

  20. Removable partial dentures: The clinical need for innovation.

    Science.gov (United States)

    Campbell, Stephen D; Cooper, Lyndon; Craddock, Helen; Hyde, T Paul; Nattress, Brian; Pavitt, Sue H; Seymour, David W

    2017-09-01

    The number of partially dentate adults is increasing, and many patients will require replacement of missing teeth. Although current treatment options also include fixed partial dentures and implants, removable partial dentures (RPDs) can have advantages and are widely used in clinical practice. However, a significant need exists to advance materials and fabrication technologies because of the unwanted health consequences associated with current RPDs. The purpose of this review was to assess the current state of and future need for prosthetics such as RPDs for patients with partial edentulism, highlight areas of weakness, and outline possible solutions to issues that affect patient satisfaction and the use of RPDs. The data on treatment for partial edentulism were reviewed and summarized with a focus on currently available and future RPD designs, materials, means of production, and impact on oral health. Data on patient satisfaction and compliance with RPD treatment were also reviewed to assess patient-centered care. Design, materials, ease of repair, patient education, and follow-up for RPD treatment all had a significant impact on treatment success. Almost 40% of patients no longer use their RPD within 5 years because of factors such as sociodemographics, pain, and esthetics. Research on RPD-based treatment for partial edentulism for both disease-oriented and patient-centered outcomes is lacking. Future trials should evaluate new RPD materials and design technologies and include both long-term follow-up and health-related and patient-reported outcomes. Advances in materials and digital design/production along with patient education promise to further the application of RPDs and improve the quality of life for patients requiring RPDs. Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.

  1. Adsorptive Removal of Toxic Chromium from Waste-Water Using Wheat Straw and Eupatorium adenophorum

    Science.gov (United States)

    Song, Dagang; Pan, Kaiwen; Tariq, Akash; Azizullah, Azizullah; Sun, Feng; Li, Zilong; Xiong, Qinli

    2016-01-01

    Environmental pollution with heavy metals is a serious issue worldwide posing threats to humans, animals and plants and to the stability of overall ecosystem. Chromium (Cr) is one of most hazardous heavy metals with a high carcinogenic and recalcitrant nature. Aim of the present study was to select low-cost biosorbent using wheat straw and Eupatorium adenophorum through simple carbonization process, capable of removing Cr (VI) efficiently from wastewater. From studied plants a low cost adsorbent was prepared for removing Cr (VI) from aqueous solution following very simple carbonization method excluding activation process. Several factors such as pH, contact time, sorbent dosage and temperature were investigated for attaining ideal condition. For analysis of adsorption equilibrium isotherm data, Langmuir, Freundlich and Temkin models were used while pseudo-first-order, pseudo-second-order, external diffusion and intra-particle diffusion models were used for the analysis of kinetic data. The obtained results revealed that 99.9% of Cr (VI) removal was observed in the solution with a pH of 1.0. Among all the tested models Langmuir model fitted more closely according to the data obtained. Increase in adsorption capacity was observed with increasing temperature revealing endothermic nature of Cr (VI). The maximum Cr (VI) adsorption potential of E. adenophorum and wheat straw was 89.22 mg per 1 gram adsorbent at 308K. Kinetic data of absorption precisely followed pseudo-second-order model. Present study revealed highest potential of E. adenophorum and wheat straw for producing low cost adsorbent and to remove Cr (VI) from contaminated water. PMID:27911906

  2. Ion-exchange resin for removing hexavalent chromium from ground water at treatment facility C: Data on removal capacity, regeneration efficiency, and operation

    Energy Technology Data Exchange (ETDEWEB)

    Bahowick, S.; Dobie, D.; Kumamoto, G. [Lawrence Livermore National Lab., CA (United States)

    1996-12-31

    Lawrence Livermore National Laboratory (LLNL) is operated for the Department of Energy by the University of California. In July 1987, LLNL was placed on the National Priorities List based on the presence of volatile organic compounds (VOCs) in ground water. The July 1992 Record of Decision stipulates air stripping for treatment of VOCs and ion-exchange to treat chromium in the ground water for Treatment Facility C (TFC). TFC, which was activated in October 1993, was designed to treat influent ground water at 60 gpm with concentrations of hexavalent chromium averaging 30 ppb. The ion exchange system removes the hexavalent chromium to below its limit of detection (2 ppb). The resin used is a strongly basic Type I quaternary ammonium anion exchange resin with a styrene-divinylbenzene copolymer gel matrix. The total hexavalent chromium removed from the ground water as of October 8, 1995 was 660 grams. An initial operating capacity was achieved of 6.4 grams CrO{sub 4}{sup 2{minus}} removal per ft{sup 3} of resin, but this was observed to vary over the next two years. Variation was observed in the rate of breakthrough. The regeneration process was optimized to minimize waste produced and maximize regeneration of the resin. Elevated levels of chloride, sulfate, nitrate, potassium 40 and uranium have been observed in the regeneration waste. Because of the potassium and uranium content, the regenerated waste had to be disposed of as mixed waste.

  3. Implant-assisted removable partial dentures: practical considerations.

    Science.gov (United States)

    Omura, Aaron J; Latthe, Vaibhav; Marin, Mark M; Cagna, David R

    2016-01-01

    At the heart of prosthodontic treatment planning must be a sound understanding of the quality and reliability of the prosthodontic foundation. Implant prosthodontics relies almost entirely on the biological and mechanical properties of an osseous foundation. Initiation of therapy in the absence of a healthy and stable prosthodontic foundation risks unintended and suboptimal treatment outcomes. For conventional removable partial denture (RPD) therapy, consideration must be given to interactions between the soft and hard tissues available to support and stabilize planned prostheses. The strategic addition of implants to the partially edentulous foundation can improve the support, comfort, and esthetics of an RPD, resulting in elevated patient satisfaction and greater therapeutic success. This article discusses aspects of diagnosis, treatment planning, clinical management, laboratory execution, and maintenance that must be considered in order to obtain optimal results with implant-assisted RPDs.

  4. Removal of hexavalent chromium from contaminated waters by ultrasound-assisted aqueous solution ball milling.

    Science.gov (United States)

    Chen, Lin; Chen, Zhenhua; Chen, Ding; Xiong, Wei

    2017-02-01

    Batch mode experiments were conducted to study the removal of hexavalent chromium (Cr(VI)) from aqueous solutions using ultrasound-assisted aqueous solution ball milling. The results show that the reduction rate of Cr(VI) by ultrasound-assisted aqueous solution ball milling was significantly faster than that by ball milling or ultrasound treatment alone, and an initial Cr(VI) concentration of 166mg/L could be decreased to 0.35mg/L at 120min. The decisive factors, including initial concentration of Cr(VI), pH value, ultrasonic frequency and filling gas, were studied. It was found that the optimal ultrasonic frequency for ultrasound-assisted aqueous solution ball milling device was 20kHz, and the rate of Cr(VI) reduction as a function of filling gas followed the order: Ar>air>N 2 >O 2 . Samples were characterized by X-ray diffraction, fluorescence measurements, atomic absorption and the diphenylcarbazide colorimetric method. The Cr(VI) transformed into a precipitate that could be removed from the contaminated water, after which the water could be reused. Copyright © 2016. Published by Elsevier B.V.

  5. Overeruption of teeth opposing removable partial dentures: a preliminary study.

    Science.gov (United States)

    Matsuda, Ken-Ichi; Miyashita, Yuji; Ikebe, Kazunori; Enoki, Kaori; Kurushima, Yuko; Mihara, Yusuke; Maeda, Yoshinobu

    2014-01-01

    One of the purposes of prosthodontic treatment is to prevent overeruption of opposing teeth, but there is currently minimal literature describing the efficacy of removable partial dentures (RPDs) in performing this function. This study investigated overeruption following RPD treatment. The study participants were 33 patients treated with RPDs, and overeruption was evaluated by comparing the surface computeraided design data of dental casts made at two different time points-before and after RPD treatment. Overeruption was observed in 38.1% of teeth opposed by the RPD, which was much less than the proportion of teeth that overerupted when not opposed by the RPD.

  6. Guide-Plane Retention in Designing Removable Partial Dentures.

    Science.gov (United States)

    Mothopi-Peri, Matshediso; Owen, C Peter

    To compare the influence of abutment teeth guide planes and guiding surfaces on retention of a removable partial denture (RPD). Extracted teeth embedded into a maxillary cast in the first premolar and second molar positions simulated two bounded saddles. Acrylic resin RPDs were made with no guide planes, then with guide planes, then with guiding surfaces added to directly contact the guide planes. The maximum loads on removal from the cast were recorded. There was a significant increase in retention force of 1.6 times when only guide planes were present and of 10.2 times when guiding surfaces intimately contacted the guide planes. The retention of acrylic resin RPDs can be substantially increased by making their guiding surfaces intimately contact the guide planes of the teeth.

  7. Investigation of Apple Scum and Its Modification with Magnesium Chloride and Hydrogen Peroxide for Removal of Toxic Hexavalent Chromium from Aqueous Solution

    Directory of Open Access Journals (Sweden)

    M. Noori Sepehr

    2014-12-01

    Full Text Available Introduction: Chromium is one of the heavy metals present in effluents produced from industrial activities and exists in the trivalent and hexavalent state. It is mentioned that hexavalent chromium has is more hazardous due to its carcinogenic properties. Due to its hazard, Cr(VI must be removed from wastewaters prior discharge into the environment. For this reason, the present aimed for removal of hexavalent chromium by Apple Scum and its modification with magnesium chloride and hydrogen peroxide. Material and Methods: Apple Scum was obtained from Galin Plan as waste materials. The Apple Scum was modified with 2M MgCl2 and 30% H2O2. Several experimental parameters such as solution pH (1-9, contact time (1-100 min, solution temperature (20-60oC, adsorbent dosage (2-10 g/L and initial chromium concentration (10-100 mg/L was investigated. All experiments were done in batch system. Results: The results of present work reveals that chromium removal efficiency was increased with increase in adsorbent dosage, contact time and initial chromium concentration, while decreased for increase in solution pH and temperature. Higher removal efficiency was observed at pH 1, 100 min contact time, 100 mg/L chromium concentration and 20oC temperature. At this optimal condition up to 90% of chromium was removed. In addition, the modification of Apple Scum leads to increase in chromium removal efficiency up to 98% for MgCl2 modified adsorbent and up to 95% forH2O2 modified one. Conclusion: The results of present work well demonstrate the waste Apple Scum for removal of hexavalent chromium and its sorption capacity will be improved in the case of modification with H2O2 and MgCl2.

  8. Occlusion and Temporomandibular Function among Subjects with Mandibular Distal Extension Removable Partial Dentures.

    NARCIS (Netherlands)

    Creugers, N.H.J.; Witter, D.J.; Spijker, A. van 't; Gerritsen, A.E.; Kreulen, C.M.

    2010-01-01

    Objective. To quantify effects on occlusion and temporomandibular function of mandibular distal extension removable partial dentures in shortened dental arches. Methods. Subjects wearing mandibular extension removable partial dentures (n = 25) were compared with subjects with shortened dental arches

  9. Flexible thermoplastic denture base materials for aesthetical removable partial denture framework.

    Science.gov (United States)

    Singh, Kunwarjeet; Aeran, Himanshu; Kumar, Narender; Gupta, Nidhi

    2013-10-01

    Conventional fixed partial dentures, implant supported Fixed Partial Dentures (FDPs) and removable partial dentures are the most common treatment modalities for the aesthetic and functional rehabilitation of partially edentulous patients. Although implants and FDP have certain advantages over removable partial dentures, in some cases, removable partial dentures may be the only choice which is available. Removable cast partial dentures are used as definitive removable prostheses when indicated, but location of clasps may affect aesthetics. So, when patient is concerned about aesthetics, flexible partial dentures which is aesthetically superior to flipper and cast partial dentures, may be considered. But for the success of flexible removable partial denture, proper diagnosis, treatment planning and insertion technique of this prosthesis is very important, which have been thoroughly described in this article.

  10. Electrochemical removal of hexavalent chromium from wastewater using Platinum-Iron/Iron-carbon nanotubes and bipolar Electrodes

    Directory of Open Access Journals (Sweden)

    Hoshyar Hossini

    2015-01-01

    Full Text Available Background: In recent decades, electrocoagulation (EC has engrossed much attention as an environmental-friendly and effectiveness process. In addition, the EC process is a potential suitable way for treatment of wastewater with concern to costs and environment. The object of this study was electrochemical evaluation of chromium removal from industrial wastewater using Platinum and carbon nanotubes electrodes. Materials and Methods: The effect of key variables including pH (3–9, hexavalent chromium concentration (50–300 mg/l, supporting electrolyte (NaCl, KCl, Na2CO3 and KNO3 and its dosage, Oxidation-Reduction variations, sludge generation rate and current density (2–20 mA/cm2 was determined. Results: Based on experimental data, optimum conditions were determined in 20, 120 min, pH 3, NaCl 0.5% and 100 mg/L initial concentration of chromium. Conclusions: Removal of hexavalent chromium from the wastewater could be successfully performanced using Platinum-Iron/Iron-carbon nanotubes and bipolar Electrodes.

  11. A comparative study of the removal of trivalent chromium from aqueous solutions by bentonite and expanded perlite

    International Nuclear Information System (INIS)

    Chakir, Achraf; Bessiere, Jacques; Kacemi, Kacem EL.; Marouf, Bouchaieb

    2002-01-01

    Local bentonite and expanded perlite (Morocco) have been characterised and used for the removal of trivalent chromium from aqueous solutions. The kinetic study had showed that the uptake of Cr(III) by bentonite is very rapid compared to expanded perlite. To calculate the sorption capacities of the two sorbents, at different pH, the experimental data points have been fitted to the Freundlich and Langmuir models, respectively, for bentonite and expanded perlite. For both sorbents the sorption capacity increases with increasing the pH of the suspensions. The removal efficiency has been calculated for both sorbents resulting that bentonite (96% of Cr(III) was removed) is more effective in removing trivalent chromium from aqueous solution than expanded perlite (40% of Cr(III) was removed). In the absence of Cr(III) ions, both bentonite and expanded perlite samples yield negative zeta potential in the pH range of 2-11. The changes of expanded perlite charge, from negative to positive, observed after contact with trivalent chromium(III) solutions was related to Cr(III) sorption on the surface of the solid. Thus, it was concluded that surface complexation plays an important role in the sorption of Cr(III) species on expanded perlite. In the case of bentonite, cation-exchange is the predominate mechanism for sorption of trivalent chromium ions, wherefore no net changes of zeta potential was observed after Cr(III) sorption. X-ray photoelectron spectroscopy measurements, at different pH values, were also made to corroborate the zeta potential results

  12. Effect of complete and partial removable dentures on chewing movements.

    Science.gov (United States)

    Gonçalves, T M S V; Vilanova, L S R; Gonçalves, L M; Rodrigues Garcia, R C M

    2014-03-01

    Partial or complete edentulism impairs mastication. However, it is unclear how the chewing cycle is affected by prosthetics. We evaluated the chewing movements of patients fitted with complete (CD) or removable partial denture (RPD). A total of 29 subjects were kinesiographically evaluated during chewing of peanuts and Optocal portions in a random sequence. The subjects were divided into two groups according to prosthesis type. Group RPD was composed of 14 partially edentulous patients using a lower distal extension RPD (mean age 61 ± 8 years), and group CD contained 15 completely edentulous patients using CD (mean age 65·9 ± 7·9 years) in both jaws. Opening, closing, occlusal and masticatory cycle times, movement angle (opening and closing), maximum velocity (opening and closing), total area and chewing cycle amplitudes were evaluated. The results were subjected to anova and Tukey's HSD test at a significance level of 5%. The RPD group exhibited shorter opening and closing phases and masticatory cycle time (P  0·05). RPD wearers use a faster chewing sequence with greater vertical and lateral jaw excursions compared with CD wearers. © 2013 John Wiley & Sons Ltd.

  13. Cadmium and chromium removal kinetics from solution by two aquatic macrophytes

    International Nuclear Information System (INIS)

    Sune, N.; Sanchez, G.; Caffaratti, S.; Maine, M.A.

    2007-01-01

    The aim of this work was to determine chromium and cadmium bioaccumulation processes of two free-floating macrophytes commonly used in wetlands for water treatment: Salvinia herzogii and Pistia stratiotes. Metal removal from the solution involves two stages: a fast one and a slow one. The fast stage of the Cd uptake is significantly different for each species, while it is not significantly different in Cr uptake. The most important processes of Cd uptake are biological ones in S. herzogii and adsorption, chelation and ionic exchange are in P. stratiotes. The main processes of Cr uptake in both macrophytes are adsorption, chelation and ion exchange. The slow stage is different for each species and metal. Cr precipitation induced by roots occurs in P. stratiotes. Cr uptake through leaves is probably the main cause of the increase of Cr in the aerial parts of S. herzogii. - Cd uptake processes are biological processes in S. herzogii and adsorption, chelation and ionic exchange are in P. stratiotes, whereas Cr uptake processes in both macrophytes are adsorption, chelation and ion exchange

  14. Preparation of Silk Sericin/Lignin Blend Beads for the Removal of Hexavalent Chromium Ions.

    Science.gov (United States)

    Kwak, Hyo Won; Shin, Munju; Yun, Haesung; Lee, Ki Hoon

    2016-09-02

    In the present study, novel adsorbents having high adsorption capability and reusability were prepared using agricultural by-products: silk sericin and lignin. Silk sericin and lignin blend beads were successfully prepared using simple coagulation methods for the removal of hexavalent chromium (Cr(VI)) from aqueous solution. A 1 M lithium chloride (LiCl)/dimethyl sulfoxide (DMSO) solvent system successfully dissolved both sericin and lignin and had sufficient viscosity for bead preparation. Compared to the conventional sericin bead adsorbent, sericin/lignin blend beads showed higher Cr(VI) adsorption capacity. The amount of lignin added to the adsorbent greatly affected the adsorption capacity of the beads, and a 50:50 sericin/lignin blend ratio was optimal. Adsorption behavior followed the Freundlich isotherm, which means the adsorption of Cr(VI) occurred on the heterogeneous surface. Cr(VI) adsorption capability increased with temperature because of thermodynamic-kinetic effects. In addition, over 90% of Cr(VI) ions were recovered from the Cr(VI) adsorbed sericin/lignin beads in a 1 M NaOH solution. The adsorption-desorption recycling process was stable for more than seven cycles, and the recycling efficiency was 82%. It is expected that the sericin/lignin beads could be successfully applied in wastewater remediation especially for hazardous Cr(VI) ions in industrial wastewater.

  15. Preparation of Silk Sericin/Lignin Blend Beads for the Removal of Hexavalent Chromium Ions

    Directory of Open Access Journals (Sweden)

    Hyo Won Kwak

    2016-09-01

    Full Text Available In the present study, novel adsorbents having high adsorption capability and reusability were prepared using agricultural by-products: silk sericin and lignin. Silk sericin and lignin blend beads were successfully prepared using simple coagulation methods for the removal of hexavalent chromium (Cr(VI from aqueous solution. A 1 M lithium chloride (LiCl/dimethyl sulfoxide (DMSO solvent system successfully dissolved both sericin and lignin and had sufficient viscosity for bead preparation. Compared to the conventional sericin bead adsorbent, sericin/lignin blend beads showed higher Cr(VI adsorption capacity. The amount of lignin added to the adsorbent greatly affected the adsorption capacity of the beads, and a 50:50 sericin/lignin blend ratio was optimal. Adsorption behavior followed the Freundlich isotherm, which means the adsorption of Cr(VI occurred on the heterogeneous surface. Cr(VI adsorption capability increased with temperature because of thermodynamic-kinetic effects. In addition, over 90% of Cr(VI ions were recovered from the Cr(VI adsorbed sericin/lignin beads in a 1 M NaOH solution. The adsorption-desorption recycling process was stable for more than seven cycles, and the recycling efficiency was 82%. It is expected that the sericin/lignin beads could be successfully applied in wastewater remediation especially for hazardous Cr(VI ions in industrial wastewater.

  16. Preparation of Silk Sericin/Lignin Blend Beads for the Removal of Hexavalent Chromium Ions

    Science.gov (United States)

    Kwak, Hyo Won; Shin, Munju; Yun, Haesung; Lee, Ki Hoon

    2016-01-01

    In the present study, novel adsorbents having high adsorption capability and reusability were prepared using agricultural by-products: silk sericin and lignin. Silk sericin and lignin blend beads were successfully prepared using simple coagulation methods for the removal of hexavalent chromium (Cr(VI)) from aqueous solution. A 1 M lithium chloride (LiCl)/dimethyl sulfoxide (DMSO) solvent system successfully dissolved both sericin and lignin and had sufficient viscosity for bead preparation. Compared to the conventional sericin bead adsorbent, sericin/lignin blend beads showed higher Cr(VI) adsorption capacity. The amount of lignin added to the adsorbent greatly affected the adsorption capacity of the beads, and a 50:50 sericin/lignin blend ratio was optimal. Adsorption behavior followed the Freundlich isotherm, which means the adsorption of Cr(VI) occurred on the heterogeneous surface. Cr(VI) adsorption capability increased with temperature because of thermodynamic-kinetic effects. In addition, over 90% of Cr(VI) ions were recovered from the Cr(VI) adsorbed sericin/lignin beads in a 1 M NaOH solution. The adsorption-desorption recycling process was stable for more than seven cycles, and the recycling efficiency was 82%. It is expected that the sericin/lignin beads could be successfully applied in wastewater remediation especially for hazardous Cr(VI) ions in industrial wastewater. PMID:27598142

  17. Use of metallurgical dust for removal chromium ions from aqueous solutions

    Science.gov (United States)

    Pająk, Magdalena; Dzieniszewska, Agnieszka; Kyzioł-Komosińska, Joanna; Chrobok, Michał

    2018-01-01

    The aim of the study was to determine the potential for the application of dust from steel plant as an effective sorbent for removing Cr(III) and Cr(VI) in the form of simple and complex ions - Acid Blue 193 dye from aqueous solutions. Three isotherms models were used to interpret the experimental results namely: Langmuir, Freundlich, and Dubinin-Radushkevich. Estimated equations parameters allowed to determine the binding mechanism. Based on laboratory studies it was found that the dust was characterized by high sorption capacities for Cr ions and dye from the aqueous solution. The sorption capacity of the dust for Cr(III) and Cr(VI) ions depended on the degree of oxidation, pH of solution and kind of anion and changed in series: Cr(III)-Cl pH=5.0> Cr(III)-SO4 pH=5.0> Cr(III)-Cl pH=3.0> Cr(III)-SO4 pH=3.0> Cr(VI) pH=5.0> Cr(VI) pH=3.0. Dust was also characterized by a high maximum sorption capacity of dye at a range of 38.2 - 91.7 mg/g, depending on the dose of dust. Based on the study it was found that dust from a steel plant, containing iron oxides, can be used as low-cost and effective sorbent to remove pollutions containing chromium ions, especially from acidic wastewater.

  18. Use of metallurgical dust for removal chromium ions from aqueous solutions

    Directory of Open Access Journals (Sweden)

    Pająk Magdalena

    2018-01-01

    Full Text Available The aim of the study was to determine the potential for the application of dust from steel plant as an effective sorbent for removing Cr(III and Cr(VI in the form of simple and complex ions – Acid Blue 193 dye from aqueous solutions. Three isotherms models were used to interpret the experimental results namely: Langmuir, Freundlich, and Dubinin–Radushkevich. Estimated equations parameters allowed to determine the binding mechanism. Based on laboratory studies it was found that the dust was characterized by high sorption capacities for Cr ions and dye from the aqueous solution. The sorption capacity of the dust for Cr(III and Cr(VI ions depended on the degree of oxidation, pH of solution and kind of anion and changed in series: Cr(III-Cl pH=5.0> Cr(III-SO4 pH=5.0> Cr(III-Cl pH=3.0> Cr(III-SO4 pH=3.0> Cr(VI pH=5.0> Cr(VI pH=3.0. Dust was also characterized by a high maximum sorption capacity of dye at a range of 38.2 – 91.7 mg/g, depending on the dose of dust. Based on the study it was found that dust from a steel plant, containing iron oxides, can be used as low-cost and effective sorbent to remove pollutions containing chromium ions, especially from acidic wastewater.

  19. REMOVABLE PARTIAL DENTURE MANAGEMENT ON POST-MENOPAUSE OSTEOPOROTIC FEMALE

    Directory of Open Access Journals (Sweden)

    Nina Ariani

    2015-06-01

    Full Text Available Osteoporosis is a condition of generalised skeletal fragility caused by diminishing bone amount and disturbance in bone microarchitecture with implication that the bone's ability to withstand forces is decreased. This condition leads to more bone resorption. Some researchers show that this condition also affects jaw bone. Therefore we must take this condition into consideration during prothodontic treatment. Dental prostheses are made to restore stomatognatic function as well as to preserve what was left including alveolar bone. The ability of dental prostheses to preserve residual alveolar bone differs according to type of prostheses. The case presented here propose the treatment of osteoporotic female in Prosthodontics Clinic FKG UI with removable partial denture. Considerations in selecting the type and design of dental prostheses and attempts to modify factors that might play a role in bone resorption in connection with the patient's physical and psychological status will be discussed. Thorough examination, careful planning and good communication with the patient can provide optimum results.

  20. Epidemiological Data and Survival Rate of Removable Partial Dentures

    Science.gov (United States)

    Moreno, Amália; Haddad, Marcela Filié; Rocha, Eduardo Passos; Assunção, Wirley Gonçalves; Filho, Humberto Gennari; Santos, Emerson Gomes Dos; Sonego, Mariana Vilela; Santos, Daniela Micheline Dos

    2016-01-01

    Introduction The use of removable partial denture (RPD) is considered as low-cost and common treatment option to rehabilitate edentulous areas. Aim This study aimed to investigate the epidemiological data of patients rehabilitated with removable partial denture (RPD) in order to assess treatment survival rate and failures. Materials and Methods Epidemiological data and medical records of patients treated with RPD between 2007 and 2012 at the RPD discipline of a Brazilian University (Aracatuba Dental School- UNESP) were evaluated as well as dental records of patients who underwent RPD treatments (fabrication or repairs) between 2000 and 2010. Factors such as gender, age, presence of systemic disease, main complaint, edentulous arch, period and cause of denture replacement and the prosthesis characteristics were recorded. The chi-square test was used to assess the differences between the variables and the Kaplan Meyer to assess the survival of the RPDs evaluated. Results A total of 324 maxillary RPD and 432 mandibular RPD were fabricated. Most of the patients were women aging 41 to 60-year-old. The number of mandibular RPD Kennedy class I (26%) was statistically higher for the maxillary arch (p<.05). There was no association between main complaint to gender or the presence of systemic disease. The lingual plate was the most common major connector used in the mandible (32%). The main reason for altering the design of replaced RPDs were changes during treatment plan. Conclusion The number of patients who require RPD is large; most of RPDs are Kennedy Class I. A good treatment plan is very important for achieving a positive treatment outcome, and it is strictly related to the survival rate. PMID:27437367

  1. Process development for the removal of lead and chromium from aqueous solutions using red mud--an aluminium industry waste.

    Science.gov (United States)

    Gupta, V K; Gupta, M; Sharma, S

    2001-04-01

    Red mud, an aluminium industry waste, has been converted into an inexpensive and efficient adsorbent and used for the removal of lead and chromium from aqueous solutions. Effect of various factors on the removal of these metal ions from water (e.g. pH, adsorbent dose, adsorbate concentration, temperature, particle size, etc.) has been studied and discussed. The effect of presence of other metal ions/surfactants on the removal of Pb2+ and Cr6+ has also been studied. The material exhibits good adsorption capacity and the data follow both Freundlich and Langmuir models. Thermodynamic parameters indicate the feasibility of the process. Kinetic studies have been performed to understand the mechanism of adsorption. Dynamic modelling of lead and chromium removal on red mud has been undertaken and found to follow first-order kinetics. The rate constant and mass transfer coefficient have also been evaluated under optimum conditions of removal in order to understand the mechanism. Column studies have been carried out to compare these with batch capacities. The recovery of Pb2+ and Cr6+ and chemical regeneration of the spent column have also been tried.

  2. EXPERIMENTAL INVESTIGATION ON CHROMIUM(VI REMOVAL FROM AQUEOUS SOLUTION USING ACTIVATED CARBON RESORCINOL FORMALDEHYDE XEROGELS

    Directory of Open Access Journals (Sweden)

    Eghe A. Oyedoh

    2016-10-01

    Full Text Available The adsorption of chromium(VI metal ion in aqueous solutions by activated carbon resorcinol formaldehyde xerogels (ACRF was investigated. The results showed that pore structure, surface area and the adsorbent surface chemistry are important factors in the control of the adsorption of chromium(VI metal ions. The isotherm parameters were obtained from plots of the isotherms and from the application of Langmuir and Freundlich Isotherms. Based on regression analysis, the Langmuir isotherm model was the best fit. The maximum adsorption capacity of ACRF for chromium (VI was 241.9 mg/g. The pseudo-second-order kinetic model was the best fit to the experimental data for the adsorption of chromium metal ions by activated carbon resorcinol formaldehyde xerogels. The thermodynamics of Cr(VI ions adsorption onto ACRF was a spontaneous and endothermic process.

  3. Melanin-embedded materials effectively remove hexavalent chromium (CrVI) from aqueous solution.

    Science.gov (United States)

    Cuong, An Manh; Le Na, Nguyen Thi; Thang, Pham Nhat; Diep, Trinh Ngoc; Thuy, Ly Bich; Thanh, Nguyen Lai; Thang, Nguyen Dinh

    2018-02-23

    Currently, it is recognized that water polluted with toxic heavy metal ions may cause serious effects on human health. Therefore, the development of new materials for effective removal of heavy metal ions from water is still a widely important area. Melanin is being considered as a potential material for removal of heavy metal from water. In this study, we synthesized two melanin-embedded beads from two different melanin powder sources and named IMB (Isolated Melanin Bead originated from squid ink sac) and CMB (Commercial Melanin Bead originated from sesame seeds). These beads were of globular shape and 2-3 mm in diameter. We investigated and compared the sorption abilities of these two bead materials toward hexavalent-chromium (Cr VI ) in water. The isotherm sorption curves were established using Langmuir and Freundlich models in the optimized conditions of pH, sorption time, solid/liquid ratio, and initial concentration of Cr VI . The FITR analysis was also carried out to show the differences in surface properties of these two beads. The optimized conditions for isotherm sorption of Cr VI on IMB/CMB were set at pH values of 2/2, sorption times of 90/300 min, and solid-liquid ratios of 10/20 mg/mL. The maximum sorption capacities calculated based on the Langmuir model were 19.60 and 6.24 for IMB and CMB, respectively. However, the adsorption kinetic of Cr VI on the beads fitted the Freundlich model with R 2 values of 0.992 for IMB and 0.989 for CMB. The deduced Freundlich constant, 1/n, in the range of 0.2-0.8 indicated that these beads are good adsorption materials. In addition, structure analysis data revealed great differences in physical and chemical properties between IMB and CMB. Interestingly, FTIR analysis results showed strong signals of -OH (3295.35 cm - 1 ) and -C=O (1608.63 cm - 1 ) groups harboring on the IMB but not CMB. Moreover, loading of Cr VI on the IMB caused a shift of broad peaks from 3295.35 cm - 1 and 1608.63 cm - 1 to 3354

  4. Patient's Satisfaction with Removable Partial Dentures: A Retrospective Case Series.

    Science.gov (United States)

    Shala, Kujtim Sh; Dula, Linda J; Pustina-Krasniqi, Teuta; Bicaj, Teuta; Ahmedi, Enis F; Lila-Krasniqi, Zana; Tmava-Dragusha, Arlinda

    2016-01-01

    This retrospective clinical study aimed to assess patient's satisfaction with removable partial dentures (RPDs), as retention, chewing ability, aesthetics during the observation period. A total of 63 patients with RPDs, participated in this study. The following data was collected: Kennedy classification, denture design, denture support, satisfaction and success of RPD. The results showed that 73.6% of patients were wearing RPD for the first time and were finally satisfied. According to the denture support of RPDs, clasp-retained quadrangular RPDs were 100% effective, followed by triangular dental support 81% and linear dental support 47.7%. Comparison of RPDs with attachment with RPDs with claps assessed through Fisher exact test, confirmed statistically significant difference (P=0.008), despite retention; however, chewing ability and aesthetics showed no statistically significant difference with X 2 test on patient's satisfaction with RPD with or without attachment. Patients often would prefer not showing the anterior buccal clasps of RPD, therefore are generally satisfied more with RPD with attachment based on level of retention, chewing ability and aesthetics.

  5. Failures in the rehabilitation treatment with removable partial dentures.

    Science.gov (United States)

    Benso, Bruna; Kovalik, Ana C; Jorge, Janaina H; Campanha, Nara H

    2013-11-01

    Despite being functional and having aesthetic benefits, the acceptance of patients regarding the use of removable partial dentures (RPDs) has been low. In part, this is due to the deleterious effects that causes discomfort to the patient. Success depends not only on the care expended by the patient, including daily care and oral hygiene, but also on common goals set by their professional and clinical staff, aiming beyond aesthetics, to incorporate issues of functionality and the well-being of patients. For rehabilitation treatment with RPDs to reach the desired level of success without damaging the support structure, all the steps (diagnose, cavity preparation, adaptation of the metal structures, functional of distal extension and posterior follow-up) in the rehabilitative treatment should be carefully developed. A literature review was carried out, searching through MEDLINE (PubMed) articles published between 1965 and December 2012 including clinical trials and reviews about the use of RPDs. This study describes factors that lead to failures and complications in oral rehabilitation through the use of RPDs and suggests possible solutions.

  6. Chromium (III) removal by weak acid exchanger Amberlite IRC-50 (Na)

    Energy Technology Data Exchange (ETDEWEB)

    Mustafa, S. [National Centre of Excellence in Physical Chemistry, University of Peshawar, Peshawar 25010 (Pakistan)], E-mail: smustafa49@yahoo.com; Shah, K.H.; Naeem, A.; Waseem, M.; Tahir, M. [National Centre of Excellence in Physical Chemistry, University of Peshawar, Peshawar 25010 (Pakistan)

    2008-12-15

    Chromium (III) sorption on a weakly macroporous cation exchanger Amberlite IRC-50 (Na) is studied as a function of time and temperature. The rate constant values for chromium (III) sorption are calculated both for film and particle diffusion processes. The temperature is found to have a positive effect on both the diffusional processes. The high values of energy of activation confirm the particle diffusional nature of the process. The pH changes in the system show a competition between the Cr(OH){sup 2+} and H{sup +} ions for the exchange sites of the adsorbent. Equilibrium data are explained with the help of Langmuir equation. Various thermodynamic parameters ({delta}H{sup o}, {delta}S{sup o} and {delta}G{sup o}) from chromium (III) exchange on the resin are calculated.

  7. Chromium removal through biosorption and bioaccumulation by bacteria from tannery effluents contaminated soil

    Energy Technology Data Exchange (ETDEWEB)

    Alam, Mohammad Zubair [Department of Agricultural Microbiology, Faculty of Agricultural Sciences, Aligarh Muslim University, Aligarh (India); Ahmad, Shamim [Microbiology Division, Institute of Ophthalmology, Faculty of Medicine, J.N. Medical College, Aligarh Muslim University, Aligarh (India)

    2011-03-15

    Four bacterial isolates (two resistant and two sensitive to chromium) were isolated from soil contaminated with tannery effluents at Jajmau (Kanpur), India, and were identified by 16S rDNA gene sequencing as Stenotrophomonas maltophilia, Exiguobacterium sp., Pantoea sp., and Aeromonas sp. Biosorption of chromium by dried and living biomasses was determined in the resistant and sensitive isolates. The effect of pH, initial metal concentration, and contact time on biosorption was studied. At pH 2.5 the living biomass of chromium resistant isolate Exiguobacterium sp. ZM-2 biosorbed maximum amount of Cr{sup 6+} (29.8 mg/g) whereas the dried biomass of this isolate biosorbed 20.1 mg/g at an initial concentration of 100 mg/L. In case of chromate sensitive isolates, much difference was not observed in biosorption capacities between their dried and living biomasses. The maximum biosorption of Cr{sup 3+} was observed at pH 4.5. However, biosorption was identical in resistant and sensitive isolates. The data on chromium biosorption were analyzed using Langmuir and Freundlich isotherm model. The biosorption data of Cr{sup 6+} and Cr{sup 3+} from aqueous solution were better fitted in Langmuir isotherm model compared to Freundlich isotherm model. Metal recovery through desorption was observed better with dried biomasses compared to the living biomasses for both types of chromium ions. Bioaccumulation of chromate was found higher in chromate resistant isolates compared to the chromate sensitive isolates. Transmission electron microscopy confirmed the accumulation of chromium in cytoplasm in the resistant isolates. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  8. [Routine oral examinations and specific after-care for removable partial dentures].

    Science.gov (United States)

    de Baat, C; Witter, D J; Keltjens, H M A M; Creugers, N H J

    2011-01-01

    Following treatment with a removable partial denture, routine oral examinations are required to stabilize the existing condition in a sustainable way and to make possible the timely treatment of anomalies which have appeared. In cases of problems assessed during a routine oral examination in relation to the removable partial dentures, maintenance, restorative and prosthetic treatment may be indicated. Maintenance treatments are indicated for small and easily retrievable alterations. In removable partial denture treatment, adequate space between prepared tooth and denture is essential. Possible prosthetic treatments of a removable partial denture are relining, rebasing, improving or renewing the maxillomandibular relation, repairment, and extension.

  9. Accuracy of CAD-CAM-fabricated removable partial dentures.

    Science.gov (United States)

    Arnold, Christin; Hey, Jeremias; Schweyen, Ramona; Setz, Jürgen M

    2018-04-01

    The conventional fabrication of removable partial dentures (RPDs) is a complex, error-prone, time-consuming, and expensive process. The use of computer-aided design and computer-aided manufacturing (CAD-CAM) techniques, especially rapid prototyping, promises a more effective method for fabricating RPD frameworks. The purpose of this in vitro study was to evaluate the fit of RPD clasps fabricated by means of 4 different CAD-CAM-systems and to compare those fittings with that of the conventional lost-wax casting technique (LWT). A master model of a partially edentulous maxilla with the canines and second molars as the remaining teeth was fabricated. After the model was optically scanned, we designed a quadrangularly supported RPD with 4 clasps and a palatal strap major connector. A standard tessellation language data set was used to fabricate 12 identical RPDs by using 4 different CAD-CAM techniques: indirect rapid prototyping (wax inject printing combined with LWT), direct rapid prototyping (selective laser melting), indirect milling (wax milling with LWT), and direct milling (resin milling [polyetheretherketone]). Three conventionally cast RPDs (LWT) served as the control group. The fit accuracy of the clasps (n=12 for each group) was determined in both the horizontal and vertical dimensions by using light microscopy. Indirectly milled RPDs (117 ±34 μm horizontal and 45 ±21 μm vertical) and directly milled RPDs (43 ±23 μm horizontal, and 38 ±21 μm vertical) showed significantly better (P<.05) fit than did conventionally fabricated LWT RPDs (133 ±59 μm horizontal; 73 ±25 μm vertical). The worst fit was found for RPDs fabricated using indirect rapid prototyping (323 ±188 μm horizontal and 112 ±60 μm vertical) or direct rapid prototyping (365 ±205 μm horizontal and 363 ±133 μm vertical), which were unstable on the master model, making them unsuitable for clinical use. Most RPDs exhibited smaller vertical measuring distances. Compared with the LWT

  10. Removal of chromium hexavalent of residual water from tannery using hydrotalcite

    International Nuclear Information System (INIS)

    Martinez G, S.; Martinez, V.; Bulbulian, S.

    2000-01-01

    One of the main problems of leather tanned is the treatment that must be give to the waste water polluted with chrome which stays in trivalent form, but it is easily oxidated at chromium hexavalent. This work pretends to find an elimination media for chromium (VI) from water using the original synthetic hydrotalcite and calcined as sorbent by its anion exchange and memory effect properties. The tannery water was characterized by X-ray diffraction, thermal gravimetric analysis, specific surface and infrared spectroscopy. (Author)

  11. Equilibrium and kinetic study on chromium (VI removal from simulated waste water using gooseberry seeds as a novel biosorbent

    Directory of Open Access Journals (Sweden)

    J. Aravind

    2015-07-01

    Full Text Available Gooseberry seed (Phyllanthus acidus was used as an adsorbent to determine its feasibility for the removal of Cr(VI. Various parameters such as pH, temperature, contact time, initial metal concentration and adsorbent dosage were investigated to determine the biosorption performance. Equilibrium was attained within 60 minutes and maximum removal of 96% was achieved under the optimum conditions at pH 2. The adsorption phenomenon demonstrated here was monolayer represented by Langmuir isotherm with R2 value of 0.992 and the Langmuir constants k and q0 was found to be 0.0061 (L/mg and 19.23 (mg/g. The adsorption system obeyed Pseudo second order kinetics with R2 value of 0.999. The results of the present study indicated that gooseberry seed powder can be employed as adsorbent for the effective removal of hexavalent chromium economically.

  12. Predictive modelling of chromium removal using multiple linear and nonlinear regression with special emphasis on operating parameters of bioelectrochemical reactor.

    Science.gov (United States)

    More, Anand Govind; Gupta, Sunil Kumar

    2018-03-24

    Bioelectrochemical system (BES) is a novel, self-sustaining metal removal technology functioning on the utilization of chemical energy of organic matter with the help of microorganisms. Experimental trials of two chambered BES reactor were conducted with varying substrate concentration using sodium acetate (500 mg/L to 2000 mg/L COD) and different initial chromium concentration (Cr i ) (10-100 mg/L) at different cathode pH (pH 1-7). In the current study mathematical models based on multiple linear regression (MLR) and non-linear regression (NLR) approach were developed using laboratory experimental data for determining chromium removal efficiency (CRE) in the cathode chamber of BES. Substrate concentration, rate of substrate consumption, Cr i , pH, temperature and hydraulic retention time (HRT) were the operating process parameters of the reactor considered for development of the proposed models. MLR showed a better correlation coefficient (0.972) as compared to NLR (0.952). Validation of the models using t-test analysis revealed unbiasedness of both the models, with t critical value (2.04) greater than t-calculated values for MLR (-0.708) and NLR (-0.86). The root-mean-square error (RMSE) for MLR and NLR were 5.06 % and 7.45 %, respectively. Comparison between both models suggested MLR to be best suited model for predicting the chromium removal behavior using the BES technology to specify a set of operating conditions for BES. Modelling the behavior of CRE will be helpful for scale up of BES technology at industrial level. Copyright © 2018 The Society for Biotechnology, Japan. Published by Elsevier B.V. All rights reserved.

  13. STEMS AND THEIR ASHES OF SOME HERBAL PLANTS AS ADSORBENTS IN THE REMOVAL OF CHROMIUM (VI) FROM WASTE WATERS

    OpenAIRE

    V. Krishna Veni; K. Ravindhranath

    2013-01-01

    A thorough investigation is made to explore the surface sorption abilities of powders of stems and their ashes of some herbal plants in controlling the Chromium (VI) pollution in waste waters. It is found that the powders of stems and their ashes of Achyranthes aspera, Mentha, Emblica officinalis, Hybiscus roja sinensis, Ocimum sanctum and Psidium guajava have strong affinity towards Chromate at low pH values. % of removal of Chromate is found to be pH sensitive and also depends on sorption c...

  14. Influence of adaptation of removable partial denture on masticatory performance.

    Directory of Open Access Journals (Sweden)

    Jorge Nakouzi

    2016-11-01

    Full Text Available Objective: To compare the masticatory performance (MP of patients with old removable partial denture (RPD, recently inserted RPD and already adapted RPD by means of the simple sieve test. Material and Methods: Twenty-nine adult (>18 years old volunteer patients were recruited, with lower and upper RPD, excluding total edentulous subjects in the upper and lower jaw, with temporomandibular disorders, severe periodontal disease, mental disability or systemic disease compromising the masticatory or nervous system. Dentures were designed and fabricated by an expert operator. MP was evaluated in old RPD (MP1, recently inserted RPD (MP2 and adapted RPD (MP3. The simple sieve test used was Edlund-Lamm in percentage of MP, using Optosil® Comfort condensation silicone tablets, with standard sizes (5.0x20mm. In each phase, the patient chewed the tablet with 20 masticatory strokes. The crushed fragments were dried at 80°C for 60 minutes and weighed on an analytical scale. A multiple vibration sieve analysis was performed, using sieves with opening sizes of 2.8mm and 1.4mm. Shapiro-Wilk test and Anova test with Bonferroni correction were performed. Results: It was observed that MP1 presented a mean of 8.40% (SD±5.59, MP2 a mean of 8.56% (SD±5.56, and MP3 a mean of 18.26% (SD±8.12. There was a significant difference (p<0.05 between the MP1-MP3 groups, as well as between the MP2-MP3 (p<0.05. Conclusion: There is a significant increase in MP thirty days after the insertion of RPD, checkups, and adjustments performed by the dentist.

  15. Removal of toxic chromium from aqueous solution, wastewater and saline water by marine red alga Pterocladia capillacea and its activated carbon

    Directory of Open Access Journals (Sweden)

    Ahmed El Nemr

    2015-01-01

    Full Text Available Pterocladia capillacea, a red marine macroalgae, was tested for its ability to remove toxic hexavalent chromium from aqueous solution. A new activated carbon obtained from P. capillacea via acid dehydration was also investigated as an adsorbent for toxic chromium. The experiments were conducted to study the effect of important parameters such as pH, chromium concentration and adsorbent weight. Batch equilibrium tests at different pH conditions showed that at pH 1.0, a maximum chromium uptake was observed for both inactivated dried red alga P. capillacea and its activated carbon. The maximum sorption capacities for dried red alga and its activated carbon were about 12 and 66 mgg−1, respectively, as calculated by Langmuir model. The ability of inactivated red alga P. capillacea and developed activated carbon to remove chromium from synthetic sea water, natural sea water and wastewater was investigated as well. Different isotherm models were used to analyze the experimental data and the models parameters were evaluated. This study showed that the activated carbon developed from red alga P. capillacea is a promising activated carbon for removal of toxic chromium.

  16. Trivalent chromium removal from wastewater using low cost activated carbon derived from agricultural waste material and activated carbon fabric cloth

    International Nuclear Information System (INIS)

    Mohan, Dinesh; Singh, Kunwar P.; Singh, Vinod K.

    2006-01-01

    An efficient adsorption process is developed for the decontamination of trivalent chromium from tannery effluents. A low cost activated carbon (ATFAC) was prepared from coconut shell fibers (an agricultural waste), characterized and utilized for Cr(III) removal from water/wastewater. A commercially available activated carbon fabric cloth (ACF) was also studied for comparative evaluation. All the equilibrium and kinetic studies were conducted at different temperatures, particle size, pHs, and adsorbent doses in batch mode. The Langmuir and Freundlich isotherm models were applied. The Langmuir model best fit the equilibrium isotherm data. The maximum adsorption capacities of ATFAC and ACF at 25 deg. C are 12.2 and 39.56 mg/g, respectively. Cr(III) adsorption increased with an increase in temperature (10 deg. C: ATFAC-10.97 mg/g, ACF-36.05 mg/g; 40 deg. C: ATFAC-16.10 mg/g, ACF-40.29 mg/g). The kinetic studies were conducted to delineate the effect of temperature, initial adsorbate concentration, particle size of the adsorbent, and solid to liquid ratio. The adsorption of Cr(III) follows the pseudo-second-order rate kinetics. From kinetic studies various rate and thermodynamic parameters such as effective diffusion coefficient, activation energy and entropy of activation were evaluated. The sorption capacity of activated carbon (ATFAC) and activated carbon fabric cloth is comparable to many other adsorbents/carbons/biosorbents utilized for the removal of trivalent chromium from water/wastewater

  17. Use of natural mordenite to remove chromium (III) and to neutralize pH of alkaline waste waters.

    Science.gov (United States)

    Córdova-Rodríguez, Valduvina; Rodríguez-Iznaga, Inocente; Acosta-Chávez, Raquel María; Chávez-Rivas, Fernando; Petranovskii, Vitalii; Pestryakov, Alexey

    2016-01-01

    The natural mordenite from Palmarito de Cauto deposit (PZ), Cuba, was studied in this work as an ion exchanger to remove Cr(3+) cations from alkaline aqueous solutions at different pH and chromium concentrations. The mordenite stability under cyclic treatment processes with alkaline solutions and its capacity to decrease the pH of the solutions was also analyzed. It was shown that PZ removes Cr(3+) ions from alkaline solutions, and it happens independently of the starting chromium concentration and the pH of the exchange solution used. This material has an important neutralizing effect on alkaline solutions, expressed in a significant pH decrease from the early stages of the treatments. For solutions with initial pH equal to 11, it decreases to a value of around seven. The stability of this material is not affected significantly after continuous cyclic treatment with NaOH solution, which shows that mordenite, in particular from Palmarito de Cauto deposit, has high stability in alkaline solutions. The results are important as they suggest that natural zeolites may be of interest in treatments of alkaline industrial waste effluents.

  18. Kinetics of the Removal of Chromium Complex Dye from Aqueous Solutions Using Activated Carbons and Polymeric Adsorbent

    Directory of Open Access Journals (Sweden)

    Eglė Kazlauskienė

    2011-04-01

    Full Text Available The kinetics of the removal of chromium complex dye (Lanasyn Navy M-DNL from aqueous solutions using polymeric adsorbent Macronet MN 200 (MN 200 as an alternative option for activated carbon Norit RB 0.8 CC (AC was studied in the batch system. The residual colour of dye solution treated with AC or MN 200 strongly depends on solution pH with lower values at acidic pH when a positively charged surface net is favourable for the adsorption of the dye anion. The removal of dye using MN 200 was found relatively higher than that using AC. The pseudo-second order and intraparticle diffusion models agreed well with experimental data. The parameters of these models were studied as a function of temperature and adsorbent nature.Article in Lithuanian

  19. Performance Study of Chromium (VI) Removal in Presence of Phenol in a Continuous Packed Bed Reactor by Escherichia coli Isolated from East Calcutta Wetlands

    Science.gov (United States)

    Chakraborty, Bhaswati; Indra, Suvendu; Hazra, Ditipriya; Betai, Rupal; Ray, Lalitagauri; Basu, Srabanti

    2013-01-01

    Organic pollutants, like phenol, along with heavy metals, like chromium, are present in various industrial effluents that pose serious health hazard to humans. The present study looked at removal of chromium (VI) in presence of phenol in a counter-current continuous packed bed reactor packed with E. coli cells immobilized on clay chips. The cells removed 85% of 500 mg/L of chromium (VI) from MS media containing glucose. Glucose was then replaced by 500 mg/L phenol. Temperature and pH of the MS media prior to addition of phenol were 30°C and 7, respectively. Hydraulic retention times of phenol- and chromium (VI)-containing synthetic media and air flow rates were varied to study the removal efficiency of the reactor system. Then temperature conditions of the reactor system were varied from 10°C to 50°C, the optimum being 30°C. The pH of the media was varied from pH 1 to pH 12, and the optimum pH was found to be 7. The maximum removal efficiency of 77.7% was achieved for synthetic media containing phenol and chromium (VI) in the continuous reactor system at optimized conditions, namely, hydraulic retention time at 4.44 hr, air flow rate at 2.5 lpm, temperature at 30°C, and pH at 7. PMID:24073400

  20. Chromium (VI removal from aqueous solutions using a polyethylenimine - epichlorohydrin resin

    Directory of Open Access Journals (Sweden)

    Sarri Sofia

    2016-01-01

    Full Text Available The ability of a synthesized polyethylenimine - epichlorohydrin resin to remove Cr(VI from aqueous solutions was investigated in absence (initial pH 2 to 7 and presence of background electrolytes (NaNO3 and Na2SO4 solutions of initial pH 3 and 6. The determined Cr-uptake was significantly higher than the one reported for the majority of other sorbents. The photo-metrically determined uptake data were modeled by the Langmuir, Redlich-Peterson, Langmuir-Freundlich, and Toth equations. The modeling results did not point out any preference to one specific model in terms of the goodness-of-fit and the prediction of maximum sorption capacity. The Cr-sorption kinetics was investigated at 15, 25, 35 and 45 oC using 51Cr-labeled solutions and γ-ray spectroscopy. The Cr-sorption was very fast at all studied temperatures and well reproduced by the pseudo-second order kinetics equation. Rate constant and activation energy values were calculated using the experimental data. The Cr-loaded resin was also examined by XRD, XPS, XAFS and SEM/EDS. The XPS and XAFS investigations indicated a partial reduction of Cr(VI to Cr(III. The environmental compatibility of the Cr-loaded resin was examined using the EPA-TCLP method. The Cr-binding by the resin was very stable and regeneration attempts by HCl solutions of pH 3 were rather unsuccessful.

  1. Load transfer characteristics of unilateral distal extension removable partial dentures with polyacetal resin supporting components.

    Science.gov (United States)

    Jiao, T; Chang, T; Caputo, A A

    2009-03-01

    To photoelastically examine load transfer by unilateral distal extension removable partial dentures with supporting and retentive components made of the lower stiffness polyacetal resins. A mandibular photoelastic model, with edentulous space distal to the right second premolar and missing the left first molar, was constructed to determine the load transmission characteristics of a unilateral distal extension base removable partial denture. Individual simulants were used for tooth structure, periodontal ligament, and alveolar bone. Three designs were fabricated: a major connector and clasps made from polyacetal resin, a metal framework as the major connector with polyacetal resin clasp and denture base, and a traditional metal framework I-bar removable partial denture. Simulated posterior bilateral and unilateral occlusal loads were applied to the removable partial dentures. Under bilateral and left side unilateral loading, the highest stress was observed adjacent to the left side posterior teeth with the polyacetal removable partial denture. The lowest stress was seen with the traditional metal framework. Unilateral loads on the right edentulous region produced similar distributed stress under the denture base with all three designs but a somewhat higher intensity with the polyacetal framework. The polyacetal resin removable partial denture concentrated the highest stresses to the abutment and the bone. The traditional metal framework I-bar removable partial denture most equitably distributed force. The hybrid design that combined a metal framework and polyacetal clasp and denture base may be a viable alternative when aesthetics are of primary concern.

  2. Sorption performance of activated nkaliki clay in removing chromium (vi) ion from aqueous solution: kinetics, isotherm, and thermodynamic studies

    International Nuclear Information System (INIS)

    Ajemba, R.O.; Ugonabo, V.I.; Okafor, V.N.

    2017-01-01

    Bentonite from Nkaliki was modified by acid activation using different concentrations of sulphuric acid. The physicochemical properties of the raw and modified samples were analyzed. The sorption performance of the modified and raw bentonite was studied in the removal of chromium (VI) ion from aqueous solution. Effect of key process parameters on the adsorption process was studied. Results of the physicochemical analyses showed that the acid activation altered the structural arrangements of the bentonite. The surface area and adsorption capacity increased from 37.6m/sup 2//g to 74m/sup 2//g and 45 to 98%, respectively, after activating with 6mol/l of H/sub 2/SO/sub 4/. The chromium (VI) ion adsorption increased with increase in process parameters studied. The kinetics analysis of the adsorption data follows the pseudo second-order kinetics, while equilibrium analysis conformed to the Langmuir isotherm. The thermodynamic parameters revealed that adsorption process is spontaneous and endothermic. This study shows that modified Nkaliki bentonite could be used for wastewater treatment. (author)

  3. Over-accumulation of putrescine induced by cyclohexylamine interferes with chromium accumulation and partially restores pollen tube growth in Actinidia deliciosa.

    Science.gov (United States)

    Scoccianti, Valeria; Iacobucci, Marta; Speranza, Anna; Antognoni, Fabiana

    2013-09-01

    Both trivalent and hexavalent chromium, i.e., Cr(III) and Cr(VI), respectively, were previously demonstrated to affect in vitro germination and ultrastructure of kiwifruit (Actinidia deliciosa) pollen. In the present work, the response to chromium in germinating pollen was evaluated in terms of changes in the polyamine profile. Slight, though significant, increases in free spermidine and spermine occurred after exposure to Cr(III), while the levels remained almost unchanged after Cr(VI) treatment. The spermidine synthase inhibitor cyclohexylamine (CHA) caused a dramatic increase in free putrescine in both chromium-treated and untreated samples, while spermidine content was not affected. Interestingly, CHA positively affected the performance of chromium-treated pollen by partially, though significantly, restoring pollen tube growth. The major growth recovery was registered with 1 mM CHA in the presence of Cr(VI), concomitant with a considerable reduction in uptake of the metal. Conversely, endogenous calcium levels were more heavily affected in Cr(III)-treated pollen. The effect of CHA on production of reactive oxygen species also varied depending on the chromium species. The response of pollen to the CHA-induced putrescine excess was compared with that exerted by an exogenous supply of the same diamine. Results show that in Cr(III)-treated pollen, putrescine over-accumulation induced by CHA exerted similar effects as exogenous putrescine, while this was not true in the Cr(VI) treatment. It appears that the diamine was able to improve pollen tolerance to metal stress through different mechanisms, mostly depending upon the chromium species, namely via reduced metal uptake or by substituting for calcium. Copyright © 2013 Elsevier Masson SAS. All rights reserved.

  4. Removal of Chromium and Cadmium from Wastewater in Waste Stabilization Ponds, Yazd-Iran

    Directory of Open Access Journals (Sweden)

    Mohammad Reza Samaei

    2016-04-01

    Full Text Available Background: Heavy metals have destructive and irreversible effects on the human, plants and animals. Some industries in Yazd enter industrial wastewater to municipal wastewater collection system. This can lead to high levels of heavy metals in wastewater and in turn in the wastewater treatment plant effluent. Methods: This study was carried out during four months from December 22, 2009 to May 20, 2010. The experiment was performed on the inflow, outlet of anaerobic pond and first and second facultative ponds of wastewater treatment plant and then transferred to the laboratory and measured by atomic absorption spectroscopy. Results: The results of the experiments showed that the average cadmium concentrations in the inflow, anaerobic pond outlet, and first and second facultative pond outlet were 0.0066, 0.0087, 0.0076, and 0.0083μg/l, respectively. The average amounts of chromium in the inflow, anaerobic pond outlet, and first and second facultative pond outlet were 0.0076, 0.0065, 0.0043, and 0.0056 μg/l, respectively. Cadmium concentration in the effluent was higher than standard. Conclusion: The comparison of the obtained data with Iranian standards for wastewater treatment for reuse in irrigation shows that the cadmium concentration exceeded the standard and the chromium concentration was lower than the standard. Therefore, it is not suitable for reuse in the crop farms and aquatic life

  5. Evaluation of articulation of Turkish phonemes after removable partial denture application

    Directory of Open Access Journals (Sweden)

    Özbeki Murat

    2003-01-01

    Full Text Available In this study, the adaptation of patients to removable partial dentures was evaluated related to articulation of Turkish phonemes. Articulation of /t,d,n,l,r/, /g,k/, /b,p,m/ and /s,z,Õ,v,f,y,j,h,c/ phonemes were evaluated by three speech pathologists, on records taken from 15 patients before the insertion of a removable partial denture, just after insertion, and one week later. The test consisted of evaluation of phoneme articulation of independent syllables in terms of distortion, omission, substitution, mass effect, hypernasality and hyponasality. Data were evaluated with Cochrane Q, McNemar and Kruskal-Wallis tests. The results showed that for some phonemes, problems in articulation occurred after the insertion of a removable partial denture while for others a significant amelioration was observed after the insertion of a removable partial denture. In general, problems in articulation of evaluated phonemes were resolved after one week of use.

  6. A Simple Chairside Technique of Removing Crown and Fixed Partial Denture Restorations

    Directory of Open Access Journals (Sweden)

    Abhinav Gupta

    2014-03-01

    Full Text Available Retrieving failed cemented crowns and fixed partial dentures with minimum discomfort to the patient has always been a clinical concern. This article describes a technique which will allow easy and predictable removal of these restorations.

  7. Optimization of hexavalent chromium removal from aqueous solution using acid-modified granular activated carbon as adsorbent through response surface methodology

    Energy Technology Data Exchange (ETDEWEB)

    Daoud, Waseem; Ebadi, Taghi; Fahimifar, Ahmad [Amirkabir University of Technology (Tehran Polytechnic), Tehran (Iran, Islamic Republic of)

    2015-06-15

    Response surface methodology (RSM) was applied to evaluate the effect of the main operational variables, including initial pH, initial chromium ion concentration, bulk density of GAC and time on the removal of hexavalent chromium Cr(Ⅵ) from contaminated groundwater by permeable reactive barriers (PRB) with acid-modified granular activated carbon (GAC) as an adsorbent material. The removal rates of Cr(Ⅵ) under different values of these parameters were investigated and results indicated high adsorption capacity at low pH and low initial metal ion concentration of Cr(Ⅵ), but the bulk density of GAC slightly influenced the process efficiency. According to the ANOVA (analysis of variance) results, the model presents high R{sup 2} values of 94.35% for Cr(Ⅵ) removal efficiency, which indicates that the accuracy of the polynomial models was good. Also, quadratic regression models with estimated coefficients were developed to describe the pollutant removals.

  8. Membrane Made of Cellulose Acetate with Polyacrylic Acid Reinforced with Carbon Nanotubes and Its Applicability for Chromium Removal

    Directory of Open Access Journals (Sweden)

    J. A. Sánchez-Márquez

    2015-01-01

    Full Text Available Membranes made of carbon nanotubes and cellulose acetate with polyacrylic acid were designed in order to study their properties and their applicability for chromium removal. The membranes were prepared by phase inversion method using cellulose acetate and polyacrylic acid. Carbon nanotubes were added to the membrane during their process of synthesis in proportions of 1% by weight. The pores in the material are formed in layers, giving the effect of depth and forming a network. Both the carbon nanotubes and membranes were characterized by IR, Raman, and SEM spectroscopy. In addition, the concentration of acidic and basic sites and the surface charge in the materials were determined. The concentration of acid sites for oxidized nanotubes was 4.0 meq/g. The removal of Cr(VI was studied as a function of contact time and of initial concentration of Cr(VI. The removal of Cr(VI (~90% mainly occurs in a contact time from 32 to 64 h when the initial concentration of Cr(VI is 1 mg/L.

  9. Study of Chromium Removal by the Electrodialysis of Tannery and Metal-Finishing Effluents

    Directory of Open Access Journals (Sweden)

    Ruan C. A. Moura

    2012-01-01

    Full Text Available The metal-finishing and tannery industries have been under strong pressure to replace their current wastewater treatment based on a physicochemical process. The electrodialysis process is becoming an interesting alternative for wastewater treatment. Electrodialysis is a membrane separation technique, in which ions are transported from one solution to another through ion-exchange membranes, using an electric field as the driving force. Blends of polystyrene and polyaniline were obtained in order to produce membranes for electrodialysis. The produced membranes were applied in the recovery of baths from the metal-finishing and tannery industries. The parameter for electrodialysis evaluation was the percentage of chromium extraction. The results obtained using these membranes were compared to those obtained with the commercial membrane Nafion 450.

  10. Hand-assisted partial nephrectomy with early arterial clamp removal: Impact of the learning curve

    DEFF Research Database (Denmark)

    Azawi, Nessn H; Norus, Thomas P; Wittendorff, Hans-Erik

    2014-01-01

    (40%), nine (45%) and 14 (70%) patients in cohorts 1, 2 and 3, respectively (p = 0.0185). CONCLUSIONS: Hand-assisted laparoscopic partial nephrectomy with early removal of arterial clamps is safe and easy to learn. An expert laparoscopic surgeon can perform hand-assisted laparoscopic partial...

  11. Removal of chromium(VI) and dye Alizarin Red S (ARS) using polymer-coated iron oxide (Fe3O4) magnetic nanoparticles by co-precipitation method

    Science.gov (United States)

    Hanif, Sara; Shahzad, Asma

    2014-06-01

    The present research was conducted with an aim to develop such adsorbent system: polymer-coated magnetic nanoparticles which can remove heavy metal and dye from water of different concentration. Synthesis of magnetic iron oxide nanoparticles for contaminated water purification has been one of the outcomes of application of rapidly growing field of Nanotechnology in Environmental Science. In the present study, the efficiency of magnetic nanoparticles for removal of Cr(VI) and dye (alizarin) from water solutions of known concentrations were evaluated. The nanoparticles were prepared by co-precipitation method and characterized by X-ray photoelectron spectroscopy, transmission electron microscopy, and Fourier transform infrared spectroscopy. Polymer-coated magnetic iron oxide nanoparticles carrying functional groups on their surface were synthesized by different methods for permanent magnet-assisted removal of heavy metal (chromium) and dye (Alizarin Red S) from water. The characterization showed that synthesized nanoparticles were in the size range of 10-50 nm. The adsorption capacities of the Fe3O4 using polyMETAC-coated particles for dye (Alizarin Red S) removal were 80-96 % and chromium 62-91 %. The chromium concentration was determined after magnetic separation using atomic absorption spectrophotometer and dye concentration was estimated with UV-visible spectrophotometer. Nanoparticles of polymer coated showed the highest removal capacity from water for metal and dye. The developed adsorbents had higher capacity for removal of heavy metal ions and dye.

  12. A method for assessment of quality of life in relation to prosthodontics. Partial edentulism and removable partial dentures

    DEFF Research Database (Denmark)

    Ozhayat, E B; Stoltze, K; Elverdam, B

    2007-01-01

    The aim of this study was to evaluate the possible use in prosthodontics of a method for an interview technique allowing maximal individuality within the cultural boundaries. The impact of partial edentulism and removable partial denture (RPD) wearing on quality of life was chosen as the target...... of the participants answered positively to questions about the test method, including self-knowledge, consciousness and identification of needs and wishes. The 'Schedule for the Evaluation of Individual Quality of Life - Direct Weighting' turned out to be a useful instrument for assessing patients' priorities...

  13. Management of long span partially edentulous maxilla with fixed removable denture prosthesis

    Directory of Open Access Journals (Sweden)

    Mahilan I Jeyavalan

    2012-01-01

    Full Text Available Restoration of a long span partially edentulous maxilla with tooth supported prosthesis is challenging because of inherent anatomic limitations and unfavourable biomechanics present after the loss of teeth. A tooth supported fixed-removable prosthesis is a treatment option for restoration of such long span partially edentulous maxillary arches. This prosthesis meets the requirements for esthetics, phonetics, comfort, and hygiene, as well as favourable biomechanical stress distribution to the remaining natural tooth abutments. This article presents a procedure for fabrication of a fixed-removable prosthesis that has cement-retained custom cast bar metal substructure and a ball attachment retained removable superstructure prosthesis.

  14. Implant-assisted removable partial dentures as an alternative treatment for partial edentulism: a review of the literature.

    Science.gov (United States)

    Chatzivasileiou, Konstantinos; Kotsiomiti, Eleni; Emmanouil, Ioannis

    2015-01-01

    This study reviewed the current literature concerning implant-assisted removable partial dentures (RPDs) in order to present the existing knowledge about performance issues. An electronic search was conducted on the PubMed database for published English-language articles that contained information about implant-assisted RPDs. A review of these articles indicated that the combination of dental implants with RPDs constitutes a cost-efficient prosthetic protocol that can offer solutions to problematic aspects of treatment with removable partial dentures. Well-designed studies are still needed to provide robust evidence on critical issues, such as design guidelines, long-term survival of implants associated with RPDs, and their effect on patients' quality of life.

  15. Evaluation of the Periodontal Status of Abutment Teeth in Removable Partial Dentures.

    Science.gov (United States)

    Correia, André Ricardo Maia; da Silva Lobo, Fábio Daniel; Miranda, Mónica Célia Pereira; Framegas de Araújo, Filipe Miguel Soares; Santos Marques, Tiago Miguel

    2017-12-15

    The purpose of this study was to evaluate whether the use of removable partial dentures affects the periodontal status of abutment teeth. An observational cross-sectional study was done on a sample of patients rehabilitated with removable partial dentures (2010 to 2013). At a recall appointment, a clinical examination was done to collect data related to the rehabilitation and periodontal status of the abutment teeth. Of 145 invited patients, 54 attended the requested follow-up appointment (37.2%). Mean patient age was 59.1 years, and the study population was 42.6% male and 57.4% female. The mean follow-up time for the prosthesis was 26 months. Abutment teeth had higher values in all periodontal variables (P removable partial dentures is affected by these rehabilitations. A recall program for these patients involving removable prosthodontics and periodontology appointments is mandatory.

  16. In situ removal of carbon contamination from a chromium-coated mirror: ideal optics to suppress higher-order harmonics in the carbon K-edge region.

    Science.gov (United States)

    Toyoshima, Akio; Kikuchi, Takashi; Tanaka, Hirokazu; Mase, Kazuhiko; Amemiya, Kenta

    2015-11-01

    Carbon-free chromium-coated optics are ideal in the carbon K-edge region (280-330 eV) because the reflectivity of first-order light is larger than that of gold-coated optics while the second-order harmonics (560-660 eV) are significantly suppressed by chromium L-edge and oxygen K-edge absorption. Here, chromium-, gold- and nickel-coated mirrors have been adopted in the vacuum ultraviolet and soft X-ray branch beamline BL-13B at the Photon Factory in Tsukuba, Japan. Carbon contamination on the chromium-coated mirror was almost completely removed by exposure to oxygen at a pressure of 8 × 10(-2) Pa for 1 h under irradiation of non-monochromated synchrotron radiation. The pressure in the chamber recovered to the order of 10(-7) Pa within a few hours. The reflectivity of the chromium-coated mirror of the second-order harmonics in the carbon K-edge region (560-660 eV) was found to be a factor of 0.1-0.48 smaller than that of the gold-coated mirror.

  17. Performance Evaluation of Electro-Fenton Process (EFP in Removal of Hexavalent Chromium in the Presence of Cyanide, as an Interfering Agent, from Synthetic Wastewaters

    Directory of Open Access Journals (Sweden)

    Ali Reza Rahmani

    2014-06-01

    Full Text Available Background: Chromium (VI is a hazardous pollutant that enters into the environment through different industrial wastewater. Therefore, Choice a suitable method for removal of the pollutant before discharging into the environment is necessary. The aim of this work was performance evaluation of Electro-Fenton process (EFP in removal of hexavalent chromium in the presence of cyanide, as an interfering agent, from synthetic wastewaters. Methods: In this experimental study, a reactor with 1 L useful volume and 4 electrodes made ​​of iron was used. pH, initial concentration of  chromium (VI, voltage, hydrogen peroxide and cyanide concentration, as an interfering agent, were investigated in order to determine the process efficiency. Results: Results reveals that the considered parameters were affected on the efficiency of the process. In optimum condition, pH=3 and voltage=20 V, initial concentration=100 mg/L, concentration of hydrogen peroxide=50 mL/L the maximum efficiency was reached up to 97%. Cyanide Presence, in the same condition, reduced the efficiency under 50 % and also, the efficiency was decreased by changing the parameters level from optimum condition. Conclusion: Results indicate the proper efficiency of chromium (VI by EFP process; however presence of other pollutants such as cyanide can cause efficiency decrease which must be considered in the process application.

  18. High efficient removal of chromium (VI) using glycine doped polypyrrole adsorbent from aqueous solution

    CSIR Research Space (South Africa)

    Ballav, N

    2012-08-01

    Full Text Available Glycine doped polypyrrole (PPy-gly) adsorbent was prepared via in situ polymerization of pyrrole (Py) monomer in the presence of glycine (gly) for the removal of Cr(VI). Formation of PPy homopolymer and inclusion of gly in the PPy matrix were...

  19. Magnetic biochar combining adsorption and separation recycle for removal of chromium in aqueous solution.

    Science.gov (United States)

    Xin, Ouyang; Yitong, Han; Xi, Cao; Jiawei, Chen

    2017-03-01

    Biochar has been developed in recent years for the removal of contaminants such as Cr (VI) in water. The enhancement of the adsorption capacity of biochar and its recyclable use are still challenges. In this study, magnetic biochar derived from corncobs and peanut hulls was synthesized under different pyrolysis temperatures after pretreating the biomass with a low concentration of 0.5 M FeCl 3 solution. The morphology, specific surface area, saturation magnetization and Fourier transform infrared spectroscopy (FT-IR) spectra were characterized for biochar. The magnetic biochar performed well in combining adsorption and separation recycle for the removal of Cr (VI) in water. The Cr (VI) adsorbance of the biochar was increased with the increase in pyrolysis temperature, and the magnetic biochar derived from corncobs showed better performance for both magnetization and removal of Cr (VI) than that from peanut hulls. The Langmuir model was used for the isothermal adsorption and the maximum Cr (VI) adsorption capacity of corncob magnetic biochar pyrolyzed at 650 °C reached 61.97 mg/g. An alkaline solution (0.1 M NaOH) favored the desorption of Cr (VI) from the magnetic biochar, and the removal of Cr (VI) still remained around 77.6% after four cycles of adsorption-desorption. The results showed that corncob derived magnetic biochar is a potentially efficient and recoverable adsorbent for remediation of heavy metals in water.

  20. [Effects of removable partial dentures on the quality of life in people with shortened dental arches].

    Science.gov (United States)

    Armellini, D B; Heydecke, G; Witter, D J; Creugers, N H J

    2009-12-01

    In order to assess the enhanced value of removable partial dentures on the quality of life, patients at 2 university clinics were screened for the presence of complete or shortened dental arches. Those selected were assigned to 1 of 5 subgroups: 1) a shortened dental arch with all frontal teeth, 2) a shortened dental arch with one or more frontal diastemas, 3) a shortened dental arch with all frontal teeth, restored by a removable partial denture, 4) a shortened dental arch and several diastemas, restored by a removable partial denture, 5) a complete dental arch. The participants completed the Oral Health Impact Profile (OHIP-49) and the Short Form Health Survey (SF-36). Clinical data recorded were: whether any teeth were missing and if so which, whether or not these had been replaced by a removable partial denture, and the number of occluding pairs of (pre)molars. The results revealed that a shortenend dental arch has a certain impact on the quality of life. However, the participants only experienced benefits from a removable partial denture if the denture also replaced frontal teeth.

  1. Characteristics and mechanisms of hexavalent chromium removal by biochar from sugar beet tailing

    International Nuclear Information System (INIS)

    Dong Xiaoling; Ma, Lena Q.; Li Yuncong

    2011-01-01

    Highlights: → Biochar from sugar beet tailing effectively removed Cr(VI) from solution. → Most of the Cr on the biochar was Cr(III). → Cr(VI) removal was via electrostatic attraction to biochar. → Reduction of Cr(VI) to Cr(III) ion and complexation between Cr(III) ion and biochar function groups were also important. → The maximum sorption capacity of biochar for Cr(VI) was123 mg/g. - Abstract: Removal of Cr(VI) from aqueous solutions using biochar from sugar beet tailing (SBT) was investigated as a function of pH, contact time, and biochar mass via batch experiments. The surface characteristics of SBT biochar before and after Cr(VI) sorption was investigated with scanning electron microscopy equipped with energy dispersive X-ray spectroscopy and Fourier transform infrared spectroscopy. Desorption and X-ray photoelectron spectroscopy studies showed that most of the Cr bound to SBT biochar was Cr(III). These results indicated that the electrostatic attraction of Cr(VI) to positively charged biochar surface, reduction of Cr(VI) to Cr(III) ion, and complexation between Cr(III) ion and SBT's function groups were probably responsible for Cr(VI) removal by SBT biochar. An initial solution with a pH of 2.0 was most favorable for Cr(VI) removal. The sorption process can be described by the pseudo-second order equation and Langmuir isotherm. The maximum sorption capacity for Cr(VI) was 123 mg/g under an acidic medium, which was comparable to other low-cost sorbents.

  2. Ion exchange removal of chromium (iii) from tannery wastes by using a strong acid cation exchange resin amberlite ir-120 h+ and its hybrids

    International Nuclear Information System (INIS)

    Ahmad, T.

    2014-01-01

    A strong acid cation exchange resin Amberlite IR-120 H+ and its hybrids with Mn(OH)/sub 2/, Cu(OH)/sub 2/ and Fe(OH)/sub 3/ are used for the removal of chromium (III) from spent tannery bath. The experimental data give good fits with the Langmuir sorption model. The thermodynamic parameters entropy (delta S), enthalpy (delta H) and free energy (delta G) changes are computed, which reveal that the chromium removal from tannery wastes by ion exchangers is an endothermic, physical sorption and entropically driven process. The rate of sorption is found to increase with the increase of resin dosage, stirring speed and temperature. Different kinetic models such as film diffusion, particle diffusion and Lagergren pseudo first order are used to evaluate the mechanism of the process. It is found that the hybrid ion exchange resins have better removal capacity as compared to the parent ion exchanger. The increase in the removal capacity is found to be in the order of the corresponding PZC values of the hybrid ion exchangers. Further, it is suggested that the higher exchange capacity is the result of Donnan effect and specific adsorption of chromium by the oxides / hydroxides present inside the matrix of the organic cation exchanger. (author)

  3. Effect of different cleansers on the weight and ion release of removable partial denture: an in vitro study

    Directory of Open Access Journals (Sweden)

    Daniela N.B. Felipucci

    2011-10-01

    Full Text Available OBJECTIVE: Removable partial dentures (RPD require different hygiene care, and association of brushing and chemical cleansing is the most recommended to control biofilm formation. However, the effect of cleansers has not been evaluated in RPD metallic components. The aim of this study was to evaluate in vitro the effect of different denture cleansers on the weight and ion release of RPD. MATERIAL AND METHODS: Five specimens (12x3 mm metallic disc positioned in a 38x18x4 mm mould filled with resin, 7 cleanser agents [Periogard (PE, Cepacol (CE, Corega Tabs (CT, Medical Interporous (MI, Polident (PO, 0.05% sodium hypochlorite (NaOCl, and distilled water (DW (control] and 2 cobalt-chromium alloys [DeguDent (DD, and VeraPDI (VPDI] were used for each experimental situation. One hundred and eighty immersions were performed and the weight was analyzed with a high precision analytic balance. Data were recorded before and after the immersions. The ion release was analyzed using mass spectrometry with inductively coupled plasma. Data were analyzed by two-way ANOVA and Tukey HSD post hoc test at 5% significance level. RESULTS: Statistical analysis showed that CT and MI had higher values of weight loss with higher change in VPDI alloy compared to DD. The solutions that caused more ion release were NaOCl and MI. CONCLUSIONS: It may be concluded that 0.05% NaOCl and Medical Interporous tablets are not suitable as auxiliary chemical solutions for RPD care.

  4. Removal of chromium (VI) from water by micro-alloyed aluminium ...

    African Journals Online (AJOL)

    This paper deals with Cr(VI) ion removal from water, by micro-alloyed aluminium composite (MAlC), under flow conditions. In a water environment the MAlC acts as a strong reducing agent. Dissolving it in water is accompanied by the generation of Al(III) ions and reduction of water to H2, with OH- ions. The final product is ...

  5. Chromium-based metal-organic framework MIL-101 as a highly effective catalyst in plasma for toluene removal

    Science.gov (United States)

    Wu, Junliang; Xia, Qibin; Xiao, Jing; Li, Zhong

    2017-11-01

    Catalytic performance of MIL-101—a type of chromium-based metal-organic frameworks (MOFs)—in a plasma catalysis system for toluene removal was experimentally studied. The MIL-101 was synthesized using a hydrothermal method, and its catalytic performance was compared to two other catalysts, Cr2O3/γ-Al2O3 and γ-Al2O3, in a dielectric barrier discharge (DBD) reactor. Results showed that the presence of a catalyst in plasma changed the voltage and current characteristic substantially, and promoted the performance of the plasma reactor. Among the catalysts, the MIL-101 exhibited a significantly high toluene conversion, which was 20% and 35% higher than Cr2O3/γ-Al2O3 and γ-Al2O3, respectively, under the same testing conditions, as well as higher carbon balance and CO2 selectivity. The analysis of by-products on the surfaces of the catalysts before and after reaction demonstrated that MIL-101 had better resistance towards by-products accumulation compared to Cr2O3/γ-Al2O3 and γ-Al2O3. The loading of MnO x on MIL-101 further promoted its catalytic performance. MIL-101 exhibits attractive catalytic properties as a catalyst in a plasma catalysis system for the decomposition of volatile organic compounds.

  6. Chromium-based metal-organic framework MIL-101 as a highly effective catalyst in plasma for toluene removal

    International Nuclear Information System (INIS)

    Wu, Junliang; Xia, Qibin; Xiao, Jing; Li, Zhong

    2017-01-01

    Catalytic performance of MIL-101—a type of chromium-based metal-organic frameworks (MOFs)—in a plasma catalysis system for toluene removal was experimentally studied. The MIL-101 was synthesized using a hydrothermal method, and its catalytic performance was compared to two other catalysts, Cr 2 O 3 / γ -Al 2 O 3 and γ -Al 2 O 3 , in a dielectric barrier discharge (DBD) reactor. Results showed that the presence of a catalyst in plasma changed the voltage and current characteristic substantially, and promoted the performance of the plasma reactor. Among the catalysts, the MIL-101 exhibited a significantly high toluene conversion, which was 20% and 35% higher than Cr 2 O 3 / γ -Al 2 O 3 and γ -Al 2 O 3 , respectively, under the same testing conditions, as well as higher carbon balance and CO 2 selectivity. The analysis of by-products on the surfaces of the catalysts before and after reaction demonstrated that MIL-101 had better resistance towards by-products accumulation compared to Cr 2 O 3 / γ -Al 2 O 3 and γ -Al 2 O 3 . The loading of MnO x on MIL-101 further promoted its catalytic performance. MIL-101 exhibits attractive catalytic properties as a catalyst in a plasma catalysis system for the decomposition of volatile organic compounds. (paper)

  7. Hexavalent Chromium Removal from Model Water and Car Shock Absorber Factory Effluent by Nanofiltration and Reverse Osmosis Membrane

    Directory of Open Access Journals (Sweden)

    Amine Mnif

    2017-01-01

    Full Text Available Nanofiltration and reverse osmosis are investigated as a possible alternative to the conventional methods of Cr(VI removal from model water and industrial effluent. The influences of feed concentration, water recovery, pH, and the coexisting anions were studied. The results have shown that retention rates of hexavalent chromium can reach 99.7% using nanofiltration membrane (NF-HL and vary from 85 to 99.9% using reverse osmosis membrane (RO-SG depending upon the composition of the solution and operating conditions. This work was also extended to investigate the separation of Cr(VI from car shock absorber factory effluent. The use of these membranes is very promising for Cr(VI water treatment and desalting industry effluent. Spiegler-Kedem model was applied to experimental results in the aim to determine phenomenological parameters, the reflection coefficient of the membrane (σ, and the solute permeability coefficient (Ps. The convective and diffusive parts of the mass transfer were quantified with predominance of the diffusive contribution.

  8. Developing a software for removable partial denture design: Part II: Introduction of RPD graph software

    Directory of Open Access Journals (Sweden)

    Nejatidanesh F

    2007-06-01

    Full Text Available Background and Aim: Designing removable partial dentures is one of the most important phases of prosthetic treatments. Computer can be used to facilitate and increase accuracy of removable partial denture design. The aim of this study was to develop a software for removable partial denture design.Materials and Methods: A questionnaire (discussed in part I and major textbooks, were used to determine the design rules.  The software (RPD Graph was developed using Visual C++ and Maryam program. The RPD Graph can determine the classification of partial edentulous arch. With defining the missing teeth and providing data about prognosis and conditions of abutment teeth, the removable partial design will be developed by RPD Graph. This software is a knowledge-based system which has specific characteristics. It can be used as an educational tool for teaching RPD design and as a clinical tool for supporting clinician's decision. In addition it can be developed to more complete softwares.

  9. Evaluating stress distribution in two different designs of class I partial removable dentures

    Directory of Open Access Journals (Sweden)

    F. Geramipanah

    1998-05-01

    Full Text Available In Present study a digital model of hemimaxillectomy was reconstructed by computer and stress distribution of removable partial dentures in tissues, periodontal ligament and bone were thoroughly evaluated. The maximum stress of two different removable partial denture designs which contained buccal and lingual c-shaped clasps respectively were analyzed and compared. It was assumed that a 90 gram force which is equal to an average obturator’s weight is applied outwardly. The results showed that the maximum stress distribution in these two designs is not significantly different.

  10. Polyacrylonitrile/polypyrrole core/shell nanofiber mat for the removal of hexavalent chromium from aqueous solution

    International Nuclear Information System (INIS)

    Wang, Jianqiang; Pan, Kai; He, Qiwei; Cao, Bing

    2013-01-01

    Highlights: ► PAN nanofibers obtained by electrospinning. ► PAN/PPy core/shell nanofiber membrane was prepared. ► PAN/PPy core/shell nanofiber membrane used for Cr(VI) removal. ► Adsorption capacity remained up to 80% within 5 times cycles. -- Abstract: Polyacrylonitrile/polypyrrole (PAN/PPy) core–shell structure nanofibers were prepared via electrospinning followed by in situ polymerization of pyrrole monomer for the removal of hexavalent chromium (Cr(VI)) from aqueous solution. Attenuated total reflections Fourier transform infrared (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS) results confirmed the presence of the polypyrrole (PPy) layer on the surface of PAN nanofibers. The morphology and structure of the core–shell PAN/PPy nanofibers were studied by scanning electron microscopy (SEM) and transmission electron microscope (TEM), and the core–shell structure can be clearly proved from the SEM and TEM images. Adsorption results indicated that the adsorption capacity increased with the initial solution pH decreased. The adsorption equilibrium reached within 30 and 90 min as the initial solution concentration increased from 100 to 200 mg/L, and the process can be described using the pseudo-second-order model. Isotherm data fitted well to the Langmuir isotherm model. Thermodynamic study revealed that the adsorption process is endothermic and spontaneous in nature. Desorption results showed that the adsorption capacity can remain up to 80% after 5 times usage. The adsorption mechanism was also studied by XPS

  11. Ammonium removal from municipal wastewater with application of ion exchange and partial nitritation/Anammox process

    OpenAIRE

    Malovanyy, Andriy

    2014-01-01

    Nitrogen removal from municipal wastewater with application of Anammox process offers cost reduction, especially if it is combined with maximal use of organic content of wastewater for biogas production. In this study a new technology is proposed, which is based on ammonium concentration from municipal wastewater by ion exchange followed by biological removal of ammonium from the concentrated stream by partial nitritation/Anammox process. In experiments on ammonium concentration four the most...

  12. Chromium (VI removal from aqueous solutions by purolite base anion-exchange resins with gel structure

    Directory of Open Access Journals (Sweden)

    Balan Catalin

    2013-01-01

    Full Text Available The removal of Cr (VI from aqueous solution using two strong base anionic resins with gel structure, Purolite A-400 (styrene-divinylbenzene matrix and Purolite A-850 (acrylic matrix was investigated in batch technique. The sorption efficiency was determined as a function of phases contact time, solution pH, resin dose, temperature and initial Cr (VI concentration. The percentage of Cr (VI removed reaches maximum values (up to 99 % in the pH range 4 - 5.3 under a resin dose of 6 g/L and of Cr (VI concentration up to 100 mg/L. An increase in temperature has a positive effect on the Cr (VI sorption process. The equilibrium sorption data were fitted with the Freundlich, Langmuir and Dubinin-Radushkevich isotherm models, using both linear and nonlinear regression method. The Langmuir model very well verifies the experimental data and gives the maximum sorption capacity of 120.55 mg Cr (VI/g and 95.82 mg Cr (VI/g for A-400 and A-850 resins, respectively. The thermodynamic study and mean free energy of sorption values calculated using Dubinin-Radushkevich equation indicated the sorption is a chemical endothermic process. The kinetic data were well described by pseudo-second order kinetic equation and the sorption process is controlled by external (film diffusion and intraparticle diffusion.

  13. Reduction and Removal of Chromium VI in Water by Powdered Activated Carbon

    Directory of Open Access Journals (Sweden)

    Yanan Chen

    2018-02-01

    Full Text Available Cr adsorption on wood-based powdered activated carbon (WPAC was characterized by scanning electron microscopy coupled with energy dispersive spectroscopy (SEM-EDS, Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS. The highest Cr(VI adsorption (40.04% was obtained under acidic conditions (pH 3, whereas Cr removal at pH 10 was only 0.34%. The mechanism of Cr(VI removal from aqueous solutions by WPAC was based on the reduction of Cr(VI to Cr(III with the concomitant oxidation of C-H and C-OH to C-OH and C=O, respectively, on the surface of WPAC, followed by Cr(III adsorption. Raman spectroscopy revealed a change in the WPAC structure in terms of the D/G band intensity ratio after Cr(VI adsorption. SEM-EDS analysis showed that the oxygen/carbon ratio on the WPAC surface increased from 9.85% to 17.74%. This result was confirmed by XPS measurements, which showed that 78.8% of Cr adsorbed on the WPAC surface was in the trivalent state. The amount of oxygen-containing functional groups on the surface increased due to the oxidation of graphitic carbons to C-OH and C=O groups.

  14. Chromium (Ⅵ) removal from aqueous solutions through powdered activated carbon countercurrent two-stage adsorption.

    Science.gov (United States)

    Wang, Wenqiang

    2018-01-01

    To exploit the adsorption capacity of commercial powdered activated carbon (PAC) and to improve the efficiency of Cr(VI) removal from aqueous solutions, the adsorption of Cr(VI) by commercial PAC and the countercurrent two-stage adsorption (CTA) process was investigated. Different adsorption kinetics models and isotherms were compared, and the pseudo-second-order model and the Langmuir and Freundlich models fit the experimental data well. The Cr(VI) removal efficiency was >80% and was improved by 37% through the CTA process compared with the conventional single-stage adsorption process when the initial Cr(VI) concentration was 50 mg/L with a PAC dose of 1.250 g/L and a pH of 3. A calculation method for calculating the effluent Cr(VI) concentration and the PAC dose was developed for the CTA process, and the validity of the method was confirmed by a deviation of <5%. Copyright © 2017. Published by Elsevier Ltd.

  15. Precursor preparation for Ca-Al layered double hydroxide to remove hexavalent chromium coexisting with calcium and magnesium chlorides

    Energy Technology Data Exchange (ETDEWEB)

    Zhong, Lihua; He, Xiaoman; Qu, Jun; Li, Xuewei; Lei, Zhiwu; Zhang, Qiwu [School of Resources and Environment Engineering, Wuhan University of Technology, Wuhan 430070 (China); Liu, Xinzhong [College of Ecological Environment and Urban Construction, Fujian University of Technology, Fuzhou 350118 (China)

    2017-01-15

    Al(OH){sub 3} and Ca(OH){sub 2} powders are co-ground to prepare a precursor which hydrates into a layered double hydroxide (LDH) phase by agitation in aqueous solution with target hexavalent chromium (Cr(VI)) at room temperature, to achieve an obvious improvement in removal efficiency of Cr(VI) through an easy incorporation into the structure. Although the prepared precursor transforms into LDH phases also when agitated in the solutions of calcium and magnesium chlorides, it incorporates Cr(VI) preferentially to the chloride salts when they coexist. The adsorption isotherm and kinetic studies show that the phenomena occurring on the Al-Ca precursor fit a pseudo-second-order kinetics with a Langmuir adsorption capacity of 59.45 mg/g. Besides, characterizations of the prepared precursor and the samples after adsorption are also performed by X-ray diffraction (XRD), Fourier transform infrared (FT-IR), Transmission electron microscope (TEM) to understand the reason of the preferential incorporation of Cr(VI) to the coexisting chloride salts during the LDH phase formation. - Graphical abstract: Activated Ca-Al hydroxides (C{sub 3}A) transformed into Ca-Al-OH compound when agitated in water. Ca-Al precursor (C{sub 3}A) was agitated in a hexavalent chromium (Cr(VI)) solution to form Al-Ca-CrO{sub 4} LDH product. Ca-Al-CrO{sub 4} LDH phase occurred preferentially to Ca-Al-MCl{sub 2} LDH phases in the solutions of calcium and magnesium chlorides, it incorporates Cr(VI) preferentially to the chloride salts when they coexist. - Highlights: • Activated Ca-Al hydroxides transformed into LDH when agitated in water with some inorganic substances. • Hexavalent Cr was incorporated in the LDH structure at high adsorption capacity. • Ca-Al-Cr LDH phase occurred preferentially to Ca-Al-MCl{sub 2} LDH phases with coexistence. • The prepared Ca-Al hydroxides had high performance as adsorbent even with high salinity of the solution.

  16. Partial Discharge Measurement in Operation: Problems with Disturbances and their Removing

    Directory of Open Access Journals (Sweden)

    Lenka Beranova

    2008-01-01

    Full Text Available Diagnostics by partial discharge measurement is a modern diagnostic method for determination of the state of insulating systems of high voltage machines and equipment. In the High Voltage Laboratory of the Czech Technical University in Prague was developed the complex measuring and evaluating system for partial discharge measurement. Unfortunately, the main problem of discharge activity measurement in practice is in electromagnetic disturbance. This article is focused on the removing this disturbance from measured data. Great problems in the evaluation of partial discharge data is in various sorts of interferences. 

  17. Removal of Hexavalent Chromium in Portland Cement Using Ground Granulated Blast-Furnace Slag Powder

    Directory of Open Access Journals (Sweden)

    Sungchul Bae

    2017-12-01

    Full Text Available Using ground granulated blast-furnace slag (GGBS under different alkaline conditions, we studied the mechanisms and extents of Cr(VI reduction and sorption and compared them to reactions with Portland cement (PC. We also investigated the effects of mixing PC/GGBS ratios on Cr(VI dissolution after carbonating the substrates. We observed a complete sorption and reduction of Cr(VI to Cr(III in a GGBS-in-Ca(OH2 solution (pH > ~12.5 after 10 h, whereas in distilled water (pH = ~11.5 GGBS exhibited only marginal sorption and reduction (20%. Cr reactions with dissolved ions in supernatants derived from GGBS indicated that the anions dissolved from GGBS act as a reducing agent for Cr(VI in a Ca(OH2 solution. Soft X-ray absorption microscopy identified a partial reduction of Cr(VI to Cr(III on the GGBS surface. The carbonation of pure PC paste substantially increased the amount of dissolved Cr(VI in a solution phase whereas a 5 wt % replacement of PC with GGBS significantly reduced the amount of dissolved Cr(VI. We concluded that in the mixed paste during the early curing stage GGBS reduced a significant fraction of Cr(VI to Cr(III and that the Cr(III adsorbed in the GGBS-PC mixture’s hydration products does not readily dissolve, even under carbonation conditions.

  18. Clinical Fit of Partial Removable Dental Prostheses Based on Alginate or Polyvinyl Siloxane Impressions.

    NARCIS (Netherlands)

    Fokkinga, W.A.; Witter, D.J.; Bronkhorst, E.M.; Creugers, N.H.J.

    2017-01-01

    PURPOSE: The aim of this study was to analyze the clinical fit of metal-frame partial removable dental prostheses (PRDPs) based on custom trays used with alginate or polyvinyl siloxane impression material. MATERIALS AND METHODS: Fifth-year students of the Nijmegen Dental School made 25 correct

  19. Impression Procedures for Metal Frame Removable Partial Dentures as Applied by General Dental Practitioners.

    NARCIS (Netherlands)

    Fokkinga, W.A.; Uchelen, J. van; Witter, D.J.; Mulder, J.; Creugers, N.H.J.

    2016-01-01

    This pilot study analyzed impression procedures for conventional metal frame removable partial dentures (RPDs). Heads of RPD departments of three dental laboratories were asked to record features of all incoming impressions for RPDs during a 2-month period. Records included: (1) impression

  20. [Treatment of removable partial dentures. 1. Legislation, rules of conduct, care plan and treatment plan

    NARCIS (Netherlands)

    Witter, D.J.; Brands, W.G.; Barl, J.C.; Creugers, N.H.J.

    2011-01-01

    An invasive treatment, such as the treatment involving a removable partial denture, requires a well-structured approach. Regulations governing the communication between a healthcare professional and a patient in the Netherlands can be found in the Dutch Medical Treatment Act and the Rules of Conduct

  1. Posterior open occlusion management by registration of overlay removable partial denture: A clinical report

    Science.gov (United States)

    Nosouhian, Saeid; Davoudi, Amin; Derhami, Mohammad

    2015-01-01

    This clinical report describes prosthetic rehabilitation of posterior open bite relationship in a patient with several missing teeth and skeletal Class III malocclusion. Primary diagnostic esthetic evaluations were performed by mounting casts in centric relation and estimating lost vertical dimension of occlusion. Exclusive treatments were designated by applying overlay removable partial denture with external attachment systems for higher retentions. PMID:26929544

  2. [Routine oral examinations and specific after-care for removable partial dentures

    NARCIS (Netherlands)

    Baat, C. de; Witter, D.J.; Keltjens, H.M.A.M.; Creugers, N.H.J.

    2011-01-01

    Following treatment with a removable partial denture, routine oral examinations are required to stabilize the existing condition in a sustainable way and to make possible the timely treatment of anomalies which have appeared. In cases of problems assessed during a routine oral examination in

  3. Implant-supported removable partial dentures in the mandible : A 3-16 year retrospective study

    NARCIS (Netherlands)

    Jensen, Charlotte; Meijer, Henny J A; Raghoebar, Gerry M; Kerdijk, Wouter; Cune, Marco S

    PURPOSE: The purpose of this retrospective study was to assess performance, together with biological and technical complications, of implant-supported removable partial dentures (ISRPD) in mandibular Kennedy class I situations with implants placed in the anterior or posterior position. METHODS: 23

  4. Occlusion and Temporomandibular Function among Subjects with Mandibular Distal Extension Removable Partial Dentures

    Science.gov (United States)

    Creugers, N. H. J.; Witter, D. J.; Van 't Spijker, A.; Gerritsen, A. E.; Kreulen, C. M.

    2010-01-01

    Objective. To quantify effects on occlusion and temporomandibular function of mandibular distal extension removable partial dentures in shortened dental arches. Methods. Subjects wearing mandibular extension removable partial dentures (n = 25) were compared with subjects with shortened dental arches without extension (n = 74) and with subjects who had worn a mandibular extension removable partial denture in the past (n = 19). Subjects with complete dentitions (n = 72) were controls. Data were collected at baseline and at 3-, 6-, and 9-year observations. Results. Occlusal activity in terms of reported awareness of bruxism and occlusal tooth wear of lower anterior teeth did not differ significantly between the groups. In contrast, occlusal tooth wear of premolars in shortened dental arches with or without extension dentures was significantly higher than in the controls. Differences amongst groups with respect to signs and symptoms related to temporomandibular disorders were not found. Occlusal support of the dentures did not influence anterior spatial relationship. Occlusal contacts of the denture teeth decreased from 70% for second premolars via 50% for first molars, to 30% for second molars. Conclusions. Mandibular distal extension removable partial dentures in moderate shortened dental arches had no effects on occlusion and temporomandibular function. PMID:20671961

  5. Occlusion and Temporomandibular Function among Subjects with Mandibular Distal Extension Removable Partial Dentures

    Directory of Open Access Journals (Sweden)

    N. H. J. Creugers

    2010-01-01

    Full Text Available Objective. To quantify effects on occlusion and temporomandibular function of mandibular distal extension removable partial dentures in shortened dental arches. Methods. Subjects wearing mandibular extension removable partial dentures (n=25 were compared with subjects with shortened dental arches without extension (n=74 and with subjects who had worn a mandibular extension removable partial denture in the past (n=19. Subjects with complete dentitions (n=72 were controls. Data were collected at baseline and at 3-, 6-, and 9-year observations. Results. Occlusal activity in terms of reported awareness of bruxism and occlusal tooth wear of lower anterior teeth did not differ significantly between the groups. In contrast, occlusal tooth wear of premolars in shortened dental arches with or without extension dentures was significantly higher than in the controls. Differences amongst groups with respect to signs and symptoms related to temporomandibular disorders were not found. Occlusal support of the dentures did not influence anterior spatial relationship. Occlusal contacts of the denture teeth decreased from 70% for second premolars via 50% for first molars, to 30% for second molars. Conclusions. Mandibular distal extension removable partial dentures in moderate shortened dental arches had no effects on occlusion and temporomandibular function.

  6. Cost-effectiveness of implant-supported mandibular removable partial dentures

    NARCIS (Netherlands)

    Jensen, Charlotte; Ross, Jamila; Feenstra, Talitha L; Raghoebar, Gerry M; Speksnijder, Caroline; Meijer, Henny J A; Cune, Marco S

    ObjectivesThe aim of this study was to conduct a cost-effectiveness analysis comparing conventional removable partial dentures (RPDs) and implant-supported RPDs (ISRPDs) treatment in patients with an edentulous maxilla and a bilateral free-ending situation in the mandible. Material and methodsThirty

  7. Implant-supported removable partial dentures in the mandible : A 3-16 year retrospective study

    NARCIS (Netherlands)

    Jensen, Charlotte; Meijer, Henny J. A.; Raghoebar, Gerry M.; Kerdijk, Wouter; Cune, Marco S.

    Purpose: The purpose of this retrospective study was to assess performance, together with biological and technical complications, of implant-supported removable partial dentures (ISRPD) in mandibular Kennedy class I situations with implants placed in the anterior or posterior position. Methods: 23

  8. Posterior open occlusion management by registration of overlay removable partial denture: A clinical report.

    Science.gov (United States)

    Nosouhian, Saeid; Davoudi, Amin; Derhami, Mohammad

    2015-01-01

    This clinical report describes prosthetic rehabilitation of posterior open bite relationship in a patient with several missing teeth and skeletal Class III malocclusion. Primary diagnostic esthetic evaluations were performed by mounting casts in centric relation and estimating lost vertical dimension of occlusion. Exclusive treatments were designated by applying overlay removable partial denture with external attachment systems for higher retentions.

  9. Posterior open occlusion management by registration of overlay removable partial denture: A clinical report

    Directory of Open Access Journals (Sweden)

    Saeid Nosouhian

    2015-01-01

    Full Text Available This clinical report describes prosthetic rehabilitation of posterior open bite relationship in a patient with several missing teeth and skeletal Class III malocclusion. Primary diagnostic esthetic evaluations were performed by mounting casts in centric relation and estimating lost vertical dimension of occlusion. Exclusive treatments were designated by applying overlay removable partial denture with external attachment systems for higher retentions.

  10. Response surface modeling and optimization of chromium(VI) removal from aqueous solution using Tamarind wood activated carbon in batch process.

    Science.gov (United States)

    Sahu, J N; Acharya, Jyotikusum; Meikap, B C

    2009-12-30

    The present paper discusses response surface methodology (RSM) as an efficient approach for predictive model building and optimization of chromium adsorption on developed activated carbon. In this work the application of RSM is presented for optimizing the removal of Cr(VI) ions from aqua solutions using activated carbon as adsorbent. All experiments were performed according to statistical designs in order to develop the predictive regression models used for optimization. The optimization of adsorption of chromium on activated carbon was carried out to ensure a high adsorption efficiency at low adsorbent dose and high initial concentration of Cr(VI). While the goal of adsorption of chromium optimization was to improve adsorption conditions in batch process, i.e., to minimize the adsorbent dose and to increase the initial concentration of Cr(VI). In the adsorption experiments a laboratory developed Tamarind wood activated carbon made of chemical activation (zinc chloride) was used. A 2(4) full factorial central composite design experimental design was employed. Analysis of variance (ANOVA) showed a high coefficient of determination value (R(2)=0.928) and satisfactory prediction second-order regression model was derived. Maximum chromium removal efficiency was predicted and experimentally validated. The optimum adsorbent dose, temperature, initial concentration of Cr(VI) and initial pH of the Cr(VI) solution were found to be 4.3g/l, 32 degrees C, 20.15 mg/l and 5.41 respectively. Under optimal value of process parameters, high removal (>89%) was obtained for Cr(VI).

  11. Arsenic, chromium and mercury removal using mussel shell ash or a sludge/ashes waste mixture.

    Science.gov (United States)

    Seco-Reigosa, Natalia; Peña-Rodríguez, Susana; Nóvoa-Muñoz, Juan Carlos; Arias-Estévez, Manuel; Fernández-Sanjurjo, María J; Alvarez-Rodríguez, Esperanza; Núñez-Delgado, Avelino

    2013-04-01

    Different batches of valued mussel shell and waste mussel shell ash are characterised. Shell ash has pH > 12 and high electrical conductivities (between 16.01 and 27.27 dS m(-1)), while calcined shell shows pH values up to 10.7 and electrical conductivities between 1.19 and 3.55 dS m(-1). X-ray fluorescence, nitric acid digestion and water extractions show higher concentrations in shell ash for most parameters. Calcite is the dominant crystalline compound in this ash (95.6%), followed by aragonite. Adsorption/desorption trials were performed for mussel shell ash and for a waste mixture including shell ash, sewage sludge and wood ash, showing the following percentage adsorptions: Hg(II) >94%, As(V) >96% and Cr(VI) between 11 and 30% for shell ash; Hg(II) >98%, As(V) >88% and Cr(VI) between 30 and 88% for the waste mixture. Hg and As desorption was ash and the waste mixture, while Cr desorption was between 92 and 45% for shell ash, and between 19 and 0% for the mixture. In view of that, mussel shell ash and the mixture including shell ash, sewage sludge and wood ash could be useful for Hg(II) and As(V) removal.

  12. Electrochemical Synthesis of Nitro-Chitosan and Its Performance in Chromium Removal

    Directory of Open Access Journals (Sweden)

    Scott M. McLennan

    2013-07-01

    Full Text Available A synthesized polymeric form of chitosan, electrochemically precipitated and photochemically modified, has been found to have significant value in removal of toxic chromate oxyanions from solution. Fourier Transform Infra-Red (FTIR, Raman and X-ray photoelectron spectroscopy (XPS indicated that a significant percentage of the amine functional groups were oxidized to nitro groups as a result of reactions with hydroxyl ions formed in the electrochemical process with additional oxidation occurring as a result of exposure to ultra-violet light. The adsorption capacity of the modified chitosan for chromate was investigated in a batch system by taking into account effects of initial concentration, pH of the solution and contact time. Nitro-chitosan showed greater adsorption capacity towards Cr (VI than other forms of chitosan, with a maximum adsorption of 173 mg/g. It was found that pH 3 is the optimum for adsorption, a Langmuir model is the best fit for the adsorption isotherm, and the kinetics of reaction followed a pseudo second order function. Overall, our results indicate that electrochemical modification of chitosan is an effective method to enhance the reactivity of chitosan towards metals.

  13. Removal of chromium(VI) from wastewater using phosphoric acid treated activated carbon

    Science.gov (United States)

    Suganthi, N.

    2013-06-01

    Activated carbon prepared by phosphoric acid treatment of tamarind nuts (seeds) was investigated for the removal of Cr(VI) from aqueous solutions. The characteristics of phosphorylated tamarind nut carbon (PTNC) were evaluated for porosity and surface area. The effect of contact time, pH, adsorbent dose and particle size variation were studied to evaluate the potential applicability of carbon for treating Cr(VI) containing wastewater. The adsorbent data were modeled by Langmiur and Freundlich classical adsorption isotherms. The kinetic studies showed that Cr(VI) adsorption on PTNC was in compliance with the pseudo-second-order kinetic model. Desorption studies indicated that ion-exchange mechanism was operating. The continuous adsorption was studied in glass columns of 2.5 cm diameter using electroplating wastewater to ascertain the practical applicability of PTNC in large scale. The mechanism of adsorption was found to be ion-exchange process and was supported by FTIR spectroscopy. The surface modification after adsorption was confirmed by SEM studies.

  14. Effective Removal of Hexavalent Chromium from Aqueous Solutions Using Ionic Liquid Modified Graphene Oxide Sorbent

    Directory of Open Access Journals (Sweden)

    A. Nasrollahpour

    2017-10-01

    Full Text Available Ionic liquid modified reduced graphene oxide (IL-rGO was prepared and examined for chromate removal. The sorbent was characterized by N2 adsorption-desorption measurement (BET, transmission electron microscopy (TEM, powder X-ray diffraction (XRD, and X-ray photoelectron spectroscopy (XPS analysis. The sorption behavior of chromate on the ionic liquid modified reduced graphene oxide sorbent from an aqueous medium was studied by varying the parameters such as contact time, initial chromate concentration, pH, and agitation speed. The results showed that sorption kinetics of chromate by IL-rGO follows the pseudo second order, which indicates that the sorption mechanism is both chemical and physical interaction. The sorption isotherm studies revealed that Langmuir model provided the best fit to all the experimental data with an adsorption capacity of 232.55 mg g–1 for IL-rGO. Thermodynamic parameters, such as Gibbs free energy (–2.85 kJ mol–1 at 298 K, enthalpy (55.41 kJ mol–1, and entropy (11.64 J mol–1 K–1 of sorption of the chromate on ionic liquid modified reduced graphene oxide was evaluated, and it was found that the reaction was spontaneous and endothermic in nature.

  15. Removal of hexavalent chromium from aqueous solution using exfoliated polyaniline/montmorillonite composite.

    Science.gov (United States)

    Chen, Jun; Hong, Xiaoqin; Zhao, Yongteng; Zhang, Qianfeng

    2014-01-01

    Exfoliated polyaniline/montmorillonite (PANI/MMT) composites with nanosheet structure were successfully prepared by in situ chemical oxidation polymerization with MMT platelets as the scaffold. Amphoteric polymer, (2-methacryloyloxyethyl)trimethyl ammonium chloride and methacrylate acid copolymer, was used to modify montmorillonite and a large number of carboxylic acids were introduced on the surface of the clay platelets, which can be used as a dopant of PANI and play a 'bridge' role to combine PANI with clay. Adsorption experiments were carried out to study the effects of pH, contact time, Cr(VI) concentration, adsorbent dose and temperature. The adsorption of Cr(VI) on the PANI/MMT was highly pH dependent and the adsorption kinetics followed a pseudo-second-order model. The Langmuir isothermal model described the adsorption isotherm data well and the maximum adsorption capacity increased with the increase in temperature. Thermodynamic investigation indicated that the adsorption process is spontaneous, endothermic and marked with an increase in randomness at the adsorbent - liquid interface. The maximum adsorption capacity of the PANI/MMT composites for Cr(VI) was 308.6 mg/g at 25 °C. The excellent adsorption characteristic of exfoliated PANI/MMT composites will render it a highly efficient and economically viable adsorbent for Cr(VI) removal.

  16. Evaluation of sustained release polylactate electron donors for removal of hexavalent chromium from contaminated groundwater

    Energy Technology Data Exchange (ETDEWEB)

    Brodie, E.L.; Joyner, D. C.; Faybishenko, B.; Conrad, M. E.; Rios-Velazquez, C.; Mork, B.; Willet, A.; Koenigsberg, S.; Herman, D.; Firestone, M. K.; Hazen, T. C.; Malave, Josue; Martinez, Ramon

    2011-02-15

    To evaluate the efficacy of bioimmobilization of Cr(VI) in groundwater at the Department of Energy Hanford site, we conducted a series of microcosm experiments using a range of commercial electron donors with varying degrees of lactate polymerization (polylactate). These experiments were conducted using Hanford Formation sediments (coarse sand and gravel) immersed in Hanford groundwater, which were amended with Cr(VI) and several types of lactate-based electron donors (Hydrogen Release Compound, HRC; primer-HRC, pHRC; extended release HRC) and the polylactate-cysteine form (Metal Remediation Compound, MRC). The results showed that polylactate compounds stimulated an increase in bacterial biomass and activity to a greater extent than sodium lactate when applied at equivalent carbon concentrations. At the same time, concentrations of headspace hydrogen and methane increased and correlated with changes in the microbial community structure. Enrichment of Pseudomonas spp. occurred with all lactate additions, and enrichment of sulfate-reducing Desulfosporosinus spp. occurred with almost complete sulfate reduction. The results of these experiments demonstrate that amendment with the pHRC and MRC forms result in effective removal of Cr(VI) from solution most likely by both direct (enzymatic) and indirect (microbially generated reductant) mechanisms.

  17. Preparation of Zn-Doped Biochar from Sewage Sludge for Chromium Ion Removal.

    Science.gov (United States)

    Nguyen, Nhat-Thien; Lee, Sung-Ying; Chen, Shiao-Shing; Nguyen, Nguyen-Cong; Chang, Chang-Tang; Hsiao, Shui-Shu; Trang, Le Thuy; Kao, Ching-Yang; Lin, Min-Fa; Wang, Liangui

    2018-08-01

    Recycling and reuse waste can result in significant savings in materials and energy. In this study, the adsorption of Cr(VI) was analyzed using activated carbon (AC) and biochar (BSC) made from sewage sludge. BSC materials were synthesized using zinc chloride as an activator coupled with carbonized sewage sludge. Specific surface area, pore size distribution, and pore volume were determined by measuring nitrogen adsorption-desorption (BET). BSC morphology was measured using field-emission scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDS). Results showed that the surface area and average pore volume of the BSC were 490 m2 g-1 and 0.8 cm3 g-1, respectively. SEM results revealed that BSC had uniform pore size. Effects of varying the initial Cr(VI) concentrations, pH values, and dosages of BSC on adsorption performance were also determined. Results showed that the maximum removal efficiency of Cr(VI) was above 99%, and adsorption capacity of 50% ZnCl2-BSC was 677 mg g-1.

  18. Removable Partial Denture Supported by Implants with Prefabricated Telescopic Abutments - A Case Report

    Science.gov (United States)

    Sehgal, Komal

    2014-01-01

    Implants have been designed to rehabilitate edentulous patients with fixed prosthesis or implant supported overdentures. Implant-supported single crowns and fixed partial dentures have become successful treatment alternatives to removable and fixed partial dentures. However, it is common to have clinical situations which make it impossible to use conventional as well as implant supported fixed partial dentures. The implant supported removable partial dentures can be a treatment modality that offers the multitude of benefits of implant-based therapy—biologic, biomechanical, social, and psychological to such patients. The aim of this article is to present a case report describing the fabrication and advantages of removable partial denture supported by teeth and implants for a patient with long edentulous span. The patient was satisfied with his dentures in terms of function and aesthetics. Regular follow-up visits over a period of three years revealed that the periodontal condition of remaining natural dentition and peri-implant conditions were stable. There was no evidence of excessive residual ridge resorption or mobility of the teeth, nor were any visible changes in the bone levels of the natural teeth or implants noted on radiographs. PMID:25121066

  19. Synthesis of magnetite derivatives nanoparticles and their application for the removal of chromium (VI) from aqueous solutions.

    Science.gov (United States)

    Tahar, Lotfi Ben; Oueslati, Mohamed Habid; Abualreish, Mustafa Jaipallah Abdelmageed

    2018-02-15

    Nowadays there is a continuously increasing worldwide concern for the development of efficient wastewaters treatment technologies. Among the heavy metal ions, chromium holds a distinct position due to its high toxic nature to biological systems. This study aims to assess magnetite derivatives nanoparticles for the removal of Cr(VI) species. Crystalline magnetite-rich (Magn) and pure maghemite (Magh) nanoparticles were produced by the polyol method and by subsequent heat treatment of Magn, respectively. The XRD analysis confirmed the formation of nanosized single phase cubic spinels with a cell parameter of 8.3710(2)Å for Magn and 8.3401(2)Å for Magh, consistent with those of a magnetite-rich ferrite and maghemite, respectively. TEM analysis showed that the two nanoferrites possessed comparable mean particle size of ∼15nm. Magn and Magh showed superparamagnetic behavior at room temperature and reasonable saturation magnetizations at 300K of 69 and 67emu.g -1 , respectively. The Curie temperature of both nanoferrites exceeded 350°C allowing the materials to work in severe conditions. Room temperature, batch adsorption experiments of Cr(VI) onto maghemite nanoparticles were carried out at pH 2.0. Adsorption efficiency increased rapidly was the increase of the nanoparticles dose. For a 20mg.L -1 Cr(VI) solution a 100% removal was found with ∼3g.L -1 dose. Additionally, for a given dose (4.0g.L -1 ), the adsorption rate measured as a function of time for different Cr(VI) concentrations was very rapid; ∼90% of removable Cr(VI) species was achieved within 10min. The high rate of Cr(VI) uptake takes advantages of the high active surface chemistry of the nanoparticles. The adsorption of Cr(VI) onto Magh nanoparticles followed a pseudo-second order kinetics indicating a chemisorption process. Further, the Langmuir isotherm model was found to best describe the equilibrium data with a maximum adsorption capacity of 12.5mg.g -1 for an adsorbent dosage of 4.0g.L -1

  20. Oxidized g-C3N4/polyaniline nanofiber composite for the selective removal of hexavalent chromium.

    Science.gov (United States)

    Kumar, Rajeev; Barakat, M A; Alseroury, F A

    2017-10-09

    Nanomaterials with selective adsorption properties are in demand for environmental applications. Herein, acid etching and oxidative decomposition of melon units of graphitic carbon nitride (g-C 3 N 4 ) was performed to obtain the oxidized graphitic carbon nitride (Ox-g-C 3 N 4 ) nanosheets. Ox- g-C 3 N 4 nanosheets were further decorated on the polyaniline nanofiber (Ox-g-C 3 N 4 /Pani-NF). Ox-g-C 3 N 4 /Pani-NF was well characterized and further applied for a selective removal of hexavalent chromium (Cr(VI)) form aqueous solution. The zeta potential analysis indicate that the surface of Ox-g-C 3 N 4 /Pani-NF was positively charged which could be beneficial to bind anionic Cr(VI) ions electrostatically. In addition, nitrogen and oxygen containing functional groups exist on the Ox-g-C 3 N 4 /Pani-NF were mainly responsible for adsorption of Cr(VI) ions from aqueous solution. Moreover, the adsorption of Cr(VI) ions was also dependent on solution pH, reaction temperature and initial concentration of Cr(VI) ions. The maximum monolayer adsorption capacity of Ox-g-C 3 N 4 /Pani-NF for Cr(VI), calculated from Langmuir isotherm was 178.57 mg/g at pH = 2 and 30 °C. The activation energy (Ea = -20.66 kJ/mol) and the enthalpy change (ΔH° = -22.055 kJ/mol) validate the role of physical forces in adsorption of Cr(VI). These results demonstrate that Ox-g-C 3 N 4 /Pani-NF can be used as a potential adsorbent for environmental remediation applications.

  1. Partial Nitrification and Denitrifying Phosphorus Removal in a Pilot-Scale ABR/MBR Combined Process.

    Science.gov (United States)

    Wu, Peng; Xu, Lezhong; Wang, Jianfang; Huang, Zhenxing; Zhang, Jiachao; Shen, Yaoliang

    2015-11-01

    A pilot-scale combined process consisting of an anaerobic baffled reactor (ABR) and an aerobic membrane bioreactor (MBR) for the purpose of achieving easy management, low energy demands, and high efficiencies on nutrient removal from municipal wastewater was investigated. The process operated at room temperature with hydraulic retention time (HRT) of 7.5 h, recycle ratio 1 of 200%, recycle ratio 2 of 100%, and dissolved oxygen (DO) of 1 mg/L and achieved good effluent quality with chemical oxygen demand (COD) of 25 mg/L, NH4 (+)-N of 4 mg/L, total nitrogen (TN) of 11 mg/L, and total phosphorus (TP) of 0.7 mg/L. The MBR achieved partial nitrification, and NO2 (-)-N has been accumulated (4 mg/L). Efficient short-cut denitrification was occurred in the ABR with a TN removal efficiency of 51%, while the role of denitrification and phosphorus removal removed partial TN (14%). Furthermore, nitrogen was further removed (11%) by simultaneous nitrification and denitrification in the MBR. In addition, phosphorus accumulating organisms in the MBR sufficiently uptake phosphorus; thus, effluent TP further reduced with a TP removal efficiency of 84%. Analysis of fluorescence in situ hybridization (FISH) showed that ammonia oxidizing bacteria (AOB) and phosphorus accumulating organisms (PAOs) were enriched in the process. In addition, the accumulation of NO2 (-)-N was contributed to the inhibition on the activities of the NOB rather than its elimination.

  2. Clinical Evaluation of Implant-Supported Removable Partial Dentures With a Stress-Breaking Attachment.

    Science.gov (United States)

    Suzuki, Yasunori; Kono, Kentaro; Shimpo, Hidemasa; Sato, Yohei; Ohkubo, Chikahiro

    2017-08-01

    The stress-breaking ball (SBB) attachment can distribute the occlusal force equally between the alveolar ridge and the implants. The purpose of this study was to evaluate the implant-supported distal extension removable partial dentures (RPDs) with SBB attachment in 10 patients who were partially edentulous. This randomized crossover study was designed to compare the function of RPDs with and without healing abutments and SBB attachments to support the posterior aspects of the RPDs. Mandibular jaw movements during mastication and the occlusal force and contact area were measured with a commercially available tracking device and pressure-sensitive sheets. Using a visual analog scale, 4 criteria-chewing, retention, stability, and comfort-were evaluated. All of the data obtained were analyzed using a 1-way analysis of variance (α = 0.05). There were no significant differences in either the mean time or the coefficient of variation among the SBB attachments and healing abutments of implant-supported removable partial dentures (ISRPDs) and conventional removable partial dentures (CRPDs). SBB attachments and healing abutments of ISRPDs had greater forces and contact areas than those of CRPDs with significant differences. For all criteria, patients preferred SBB attachments to healing abutments and CRPDs. The implant-supported distal extension RPDs with SBB attachment improved denture stability and patients' satisfaction.

  3. Correlation between factors associated with the removable partial dentures use and Candida spp. in saliva.

    Science.gov (United States)

    Gusmão, João Milton Rocha; Ferreira dos Santos, Silvana Soleo; Neisser, Maximiliano Piero; Jorge, Antônio Olavo Cardoso; Faria, Ms Ivan

    2011-12-01

    To correlate the presence and number of Candida spp. in the saliva of wearers of removable partial dentures retained with precision attachments with the proportion of metal/acrylic resin present in the dentures. Saliva samples from 40 removable partial denture wearers (test) and one paired sample of individuals, non-wearers of any type of removable denture (control) were collected, seeded, and the colony forming units of Candida counted and identified. The metal/acrylic resin proportion of each denture was quantified, using silicone plates pressed over each denture. Candida spp. was found in the saliva of 80% of the individuals in the test group and 65% of the control, with C. albicans being the most prevalent species. The test group presented with the highest number of colony forming units of Candida per ml of saliva, and there was weak correlation between this number and the metal and resin area of the denture (Pearson's coefficient of correlation). Greater prevalence and a higher number of colony forming units of Candida per ml of saliva occurred in removable partial denture wearers (p = 0.04) with a weak positive correlation between the metal and resin area and the number of colony forming units of Candida per ml of saliva. However, this correlation was more significant for the area of resin. © 2010 The Gerodontology Society and John Wiley & Sons A/S.

  4. Finite element analysis in defining the optimal shape and safety factor of retentive clasp arms of removable partial denture

    Directory of Open Access Journals (Sweden)

    Šćepanović Miodrag

    2013-01-01

    Full Text Available Bacground/Aim. Retentive force of removable partial denture (RPD directly depends on elastic force of stretched retentive clasp arms (RCAs. During deflection RCA must have even stress distribution. Safety factor is the concept which can be applied in estimating durability and functionality of RCAs. This study was based on analyzing properties of clasps designed by conventional clasp wax profiles and defining the optimal shapes of RCAs for stress distribution and safety factor aspects. Methods. Computer-aided-design (CAD models of RCAs with simulated properties of materials used for fabrication of RPD cobalt-chromium-molybdenum (CoCrMo alloy, commercially pure titanium (CPTi and polyacetale were analyzed. Results. The research showed that geometrics of Rapidflex profiles from the BIOS concept are defined for designing and modeling RCAs from CoCrMo alloys. I-Bar and Bonihard clasps made from CPTi might have the same design as Co- CrMo clasp only by safety factor aspect, but it is obvious that CPTi are much more flexible, so their shape must be more massive. Polyacetale clasps should not be fabricated by BIOS concept for CoCrMo alloy. A proof for that is the low value of safety factor. Conclusion. The BIOS concept should be used only for RCAs made of CoCrMo alloy and different wax profiles should be used for fabricating clasps of other investigated materials. The contribution of this study may be the improvement of present systems for defining the clasps shapes made from CoCrMo alloys. The more significant application is possibility of creating new concepts in defining shapes of RCA made from CPTi and polyacetale.

  5. Immediate Overlay Removable Partial Dentures for a Patient with Ectodermal Dysplasia: A Clinical Report

    Directory of Open Access Journals (Sweden)

    Ramin Negahdari

    2016-01-01

    Full Text Available Ectodermal dysplasia has several characteristic signs and symptoms, including anadontia or hypodontia, conical and hypoplastic teeth, atrophic alveolar ridges, protuberant lips, and hypotrichosis. Definitive treatment options for these patients are several including fixed, removable or implant-supported prostheses. Economic limitations or other priorities can prevent patients from choosing the most desirable treatment. This clinical report describes the prosthetic rehabilitation of a patient with ectodermal dysplasia. The treatment developed an overlay immediate removable partial denture fabricated to reconstruct acceptable occlusal vertical dimension, function and esthetics. A 2-year period of follow up showed the minor chipping of composite layer on the metal substructure.   Keywords: Ectodermal dysplasia, mouth rehabilitation

  6. Design concepts of a removable partial dental prosthesis with implant-supported abutments.

    Science.gov (United States)

    Yeung, Stephanie; Chee, Winston W L; Torbati, Arman

    2014-08-01

    A clinical report is presented that describes the restoration of a severe anterior maxillary ridge defect and pneumatized sinuses with a rotation-path partial removable dental prosthesis and implant-supported abutments. Other treatment options were considered and rejected based on patient preferences and limitations, which included avoiding invasive surgeries. The principles of integrating fixed and removable prosthesis design were applied. However, the clasp design was modified to take into account the direct bone-to-implant contact of the abutments. An esthetic and functional outcome was obtained without any overly invasive surgery. Copyright © 2014 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

  7. Detection of improvement in the masticatory function from old to new removable partial dentures using mixing ability test.

    Science.gov (United States)

    Asakawa, A; Fueki, K; Ohyama, T

    2005-09-01

    The aim of this study was to determine the sensitivity of the Mixing Ability Test to detect improvement of masticatory function in subjects on transition from old to new removable partial dentures. Thirty-two subjects (seven males, 25 females, mean age 65.0 years) with distal extension partially edentulous area in mandible and/or maxilla participated in the study. The following reasons were presented for replacing the old removable partial dentures with new ones: fracture and/or poor fitness of retainers, extraction of abutment teeth, poor fitness of denture base, severe wear of artificial teeth and request for metal base dentures. Masticatory function with old and new removable partial dentures after an adaptation period (mean 27.4 weeks) was evaluated by the Mixing Ability Test. Subjects were asked to masticate five two-coloured wax cubes with each removable partial denture. Mixing Ability Index was obtained from the colour mixture and shape of the masticated cubes. Wilcoxon signed-rank test was used to test the difference of Mixing Ability Indexes between old and new removable partial dentures. The mixing ability indexes with new removable partial dentures (mean+/- s.d.: 0.70+/- 0.68) was significantly higher (Premovable partial dentures (-0.11+/-1.13). The results suggest that the Mixing Ability Test was capable of detecting improvement in masticatory function with new removable partial dentures.

  8. Computer-guided implant planning using a preexisting removable partial dental prosthesis.

    Science.gov (United States)

    Kim, Jong-Eun; Shim, June-Sung

    2017-01-01

    Converting a conventional removable partial dental prosthesis (RPDP) into an implant-assisted removable partial dental prosthesis (IARPDP) may be facilitated by using data from the intaglio surface of the RPDP for proper implant placement. This procedure can be done by connecting the data from the intaglio surface of the RPDP to the residual ridge data of the cone beam computed tomography scan with implant planning software. However, although a misplaced implant under an RPDP can cause various complications, as yet, no technique has connected the information on a patient's existing RPDP to the implant planning software. This article presents computer-guided implant planning, using a patient's existing RPDP. Copyright © 2016 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

  9. The method of manufacture of nylon dental partially removable prosthesis using additive technologies

    Science.gov (United States)

    Kashapov, R. N.; Korobkina, A. I.; Platonov, E. V.; Saleeva, G. T.

    2014-12-01

    The article is devoted to the topic of creating new methods of dental prosthesis. The aim of this work is to investigate the possibility of using additive technology to create nylon prosthesis. As a result of experimental studies, was made a sample of nylon partially removable prosthesis using 3D printing has allowed to simplify, accelerate and reduce the coat of manufacturing high-precision nylon dentures.

  10. Full mouth rehabilitation of destroyed dentition with rotational path removable partial denture: a case report

    OpenAIRE

    Kim, Moon-Hyoung; Heo, Seong-Joo; Kim, Seong-Kyun; Koak, Jai-Young

    2010-01-01

    BACKGROUND Though implant dentistry is very successful and predictable in treatment of patients with destroyed dentition, there are some cases with limitations to implant therapy. In these cases, alternative treatment modality should be considered. CASE DESCRIPTION A patient with destroyed dentition was rehabilitated with a lateral rotational path removable partial denture. According to the diagnosis, we determined to raise vertical dimension for esthetic and functional restoration. The final...

  11. Synthesis and characterization of polyaniline/zeolite nanocomposite for the removal of chromium(VI from aqueous solution

    Directory of Open Access Journals (Sweden)

    Abdulsalam A. Shyaa

    2015-01-01

    Batch adsorption experiments were used to investigate the effect of various experimental parameters on the equilibrium adsorption of chromium(VI on PANI/zeolite nanocomposite. The adsorption characteristics of the composite toward Cr(VI in dilute aqueous solution were followed spectrophotometrically. The effect of contact time, size of the sorbent and the concentration of Cr(VI in solution on the metal uptake behavior of the composite were studied. It has been observed that the capacity of chromium adsorption on PANI/zeolite increases with initial metal concentration, the metal ion adsorption on surfactant is well represented by the Freundlich isotherm.

  12. Optimization of adsorption process parameters by response surface methodology for hexavalent chromium removal from aqueous solutions using Annona reticulata Linn peel microparticles.

    Science.gov (United States)

    Saranya, N; Nakeeran, E; Giri Nandagopal, M S; Selvaraju, N

    2017-05-01

    Fruit peel microparticles of Annona reticulata Linn were used as biosorbent for the sequestration of hexavalent chromium (CR(VI)). Characterization of the biosorbent was done using scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDXS), Fourier transfer infrared spectroscopy (FTIR), gas chromatography-mass spectrometry (GCMS), carbon, hydrogen, nitrogen and sulphur (CHNS) elemental analysis, mercury intrusion porosimetry and point of zero charge. Influential parameters were optimized using response surface methodology (RSM) with a total of 17 experimental runs based on the Box-Behnken design and found to be pH 1.0, temperature 25 °C and 100 mg/L initial chromium concentration. pH and concentration were found to be more influential than temperature. The analysis of variance indicated that a second-order polynomial regression equation was the most suitable for fitting the experimental data. The experimental runs showed a good correlation with the predicted responses (R 2 = 0.9956). The biosorption process fitted well with the Langmuir isotherm with an adsorption capacity of 108. 32 mg/g out of the other isotherms such as Freundlich and Dubinin-Radushkevich that were analyzed. Non linear pseudo first order, pseudo second order, and intraparticle diffusion kinetics were applied to describe the interaction between the biosorbent and Cr(VI). Desorption and regeneration performances showed that fruit peels of Annona reticulata Linn can be an environmental friendly option for hexavalent chromium removal from aqueous solutions.

  13. Removal of chromium (VI) ions from aqueous solutions using amine-impregnated TiO2 nanoparticles modified cellulose acetate membranes.

    Science.gov (United States)

    Gebru, Kibrom Alebel; Das, Chandan

    2018-01-01

    In this work, TiO 2 nanoparticles (NPs) were modified using tetraethylenepentamine (TEPA), ethylenediamine (EDA), and hexamethylenetetramine (HMTA) amines using impregnation process. The prepared amine modified TiO 2 samples were explored as an additive to fabricate ultrafiltration membranes with enhanced capacity towards the removal of chromium ions from aqueous solution. Modified membranes were prepared from cellulose acetate (CA) polymer blended with polyethylene glycol (PEG) additive, and amine modified TiO 2 by using phase inversion technique. Fourier transform infrared spectroscopy (FTIR), zeta potential (ζ), thermo gravimetric analysis (TGA), field emission scanning electron microscopy (FESEM), water contact angle (WCA), and atomic absorption spectrophotometer (AAS) studies were done to characterize the membranes in terms of chemical structure, electric charge, thermal stability, morphology, hydrophilicity, and removal performance. The pure water permeability and Cr (VI) ion removal efficiency of the unmodified (i.e. CA/U-Ti) and the amine modified (CA/Ti-HMTA, CA/Ti-EDA, and CA/Ti-TEPA) membranes were dependent on pH and metal ion concentration. Incorporation of amine modified TiO 2 composite to the CA polymer was found to improve the fouling and removal characteristics of the membranes during the chromium ultrafiltration process. The maximum removal efficiency result of Cr (VI) ions at pH of 3.5 using CA/Ti-TEPA membrane was 99.8%. The washing/regeneration cycle results in this study described as an essential part for prospect industrial applications of the prepared membranes. The maximum Cr (VI) removal results by using CA/Ti-TEPA membrane for four washing/regeneration cycles are 99.6%, 99.5%, 98.6% and, 96.6%, respectively. Copyright © 2017 Elsevier Ltd. All rights reserved.

  14. Connection of functional quality of partial removable dentures and the degree of patients' phonetic adaptation.

    Science.gov (United States)

    Artjomenko, Victoria; Vidzis, Aldis; Zigurs, Guntis

    2015-01-01

    Phonetic adaptation is a complex biological phenomenon with a highly individual course, depending on the patient's motivation to use prosthesis, on the functional quality of removable dentures. The aim of the study was to estimate phonetic adaptation in patients with partial dentures, connecting it to alteration in speech quality and dentures functional value. We examined some peculiarities of phonetic adaptation in 50 patients with removable dentures (50 patients with natural dentition were invited for the control group). The standardized evaluation protocols (12 speech quality determining parameters) were developed separately for Latvian and Russian native speakers. 500 speech video samples were recorded and analysed according to pre-established guidelines. The connection of speech quality and the functional quality of the dentures was assessed. Statistical analysis was performed using SPSS 20.0. P values equal to or less than 0.05 were considered to be statistically significant. In patients with appropriate functional quality of removable dentures distorted speech production was detected in 25% (pk=0.008) cases and in patients with inappropriate functional quality of the prosthesis - in 40% (pkdentures functional value were satisfied with their speech performance in 96% (pk=0.674), in the group with inappropriate dentures functional value only 59% (premovable dentures depends on the patient's individual adaptation capacity, prosthetic design and functional value. Thus statistically significant correlation between removable partial dentures functional value, duration of usage and the degree of patients' phonetic adaptation (p<0.001) may be considered to be confirmed.

  15. A field survey of the partially edentate elderly: Investigation of factors related to the usage rate of removable partial dentures.

    Science.gov (United States)

    Murai, S; Matsuda, K; Ikebe, K; Enoki, K; Hatta, K; Fujiwara, K; Maeda, Y

    2015-11-01

    Although the shortened dental arch (SDA) concept has been known to all over the world, acceptance of the SDA concept as an oral health standard can be questionable from the patients' point of view, even if it is biologically reasonable. Furthermore, because the health insurance system covers removable partial dentures (RPDs) for all citizens in Japan, SDA patients seem to prefer to receive prosthetic treatment to replace the missing teeth. However, there were few field surveys to investigate the usage rate of RPDs in Japan. The purpose of this study was to determine the usage rate of RPDs in older Japanese subjects and to investigate the factors related to the usage of RPDs. Partially edentate participants (n = 390) were included in this study. Oral examinations were conducted to record several indices. The Cochran-Armitage trend test was used to evaluate the relationship between the number of missing teeth and the usage rate of RPDs. Chi-squared tests and logistic regression analysis were conducted to evaluate the factors related to the usage rate of RPDs. Usage of RPDs had a significantly positive association with the number of missing distal extension teeth and bilaterally missing teeth. The usage rate of RPDs increased as the number of missing distal extension teeth increased (P for trend < 0·001). The conclusion of this study was that participants with missing distal extension teeth had higher usage rates of RPDs than other participants, and the usage rate increased as the number of missing distal extension teeth increased. © 2015 John Wiley & Sons Ltd.

  16. Occlusion removal method of partially occluded object using variance in computational integral imaging

    Science.gov (United States)

    Lee, Byung-Gook; Kang, Ho-Hyun; Kim, Eun-Soo

    2010-06-01

    Computational integral imaging is a promising technique in partially occluded 3D object recognition. With elemental images (EIs) of partially occluded 3D object, the plane image of 3D object to be interested was reconstructed at the location where 3D object was originally located using a computational integral imaging reconstruction (CIIR) algorithm. However, occlusion prevents the high-resolution reconstructed image due to superimposing its defocusing and blurred image at the same time. To overcome this problem, in this paper, we propose a novel occlusion removal method of partially occluded 3D object in computational integral imaging. In the proposed method, we use the variance of ray intensity distribution emitting from EIs and then a series of variance plane images from the EIs is used to estimate the area and distance of occlusion since the intensity variance of focused plane image for occlusion is the lowest at the occlusion location. On the basis of the extracted information, occlusion in the EIs is simply eliminated. Then, the plane images are reconstructed with the CIIR algorithm for the occlusion removed EIs, in which we can obtain the improved high-resolution plane image. To show the feasibility of our proposed scheme, some experiments were carried out and its results are presented as well. [Figure not available: see fulltext.

  17. Effect of Gamma Radiation sterilization versus Disinfection on Removable Partial Dentures (Microbiological study)

    International Nuclear Information System (INIS)

    Mohammed, M.A.

    2011-01-01

    The aim of the study was to compare between the effectiveness of disinfection, using commercially available Fittydent super cleansing tablets versus sterilization, using gamma radiation on candidal growth in maxillary removable partial dentures. Methods: Fourteen partially edentulous subjects were selected according to specific criteria and divided equally and randomly into two groups; Group I: disinfection group and Group II: sterilization group. Conventional maxillary removable partial dentures were constructed for all subjects. The swab technique was used to collect the samples one month after denture delivery, immediately after disinfection/sterilization, and then one week, two weeks, three weeks, four weeks, and five weeks after disinfection/sterilization respectively. Bacteriological candidal colony count was performed using a manual contact colony counter. Results: Both methods (disinfection and sterilization) led to a noticeable decrease in the candidal count. However this decrease was highly and markedly evident in Group II as compared to Group I. Infact, no candidal growth was recorded for group II immediately after strerilization and was maintained for two more weeks. Statistical analysis revealed highly significant differences between the two groups. Conclusions: Both methods were effective in decreasing the number of Candida albicans adhering to the denture. However, sterilization using Gamma radiation had a more superior immediate, as well as, long term efficiency as compared to disinfection using Fittydent super cleansing tablets.

  18. Potential Fish Production Impacts from Partial Removal of Decommissioned Oil and Gas Platforms off the Coast of California

    Science.gov (United States)

    Claisse, J.; Pondella, D.; Love, M.; Zahn, L.; Williams, C.; Bull, A. S.

    2016-02-01

    When oil and gas platforms become obsolete they go through a decommissioning process. This may include partial removal (from the surface to 26 m depth) or complete removal of the platform structure. While complete removal would likely eliminate most of the existing fish biomass and associated secondary production, we find that the potential impacts of partial removal would likely be limited on all but one platform off the coast of California. On average 80% of fish biomass and 86% of secondary fish production would be retained after partial removal, with above 90% retention expected for both metrics on many platforms. Partial removal would likely result in the loss of fish biomass and production for species typically found residing in the shallow portions of the platform structure. However, these fishes generally represent a small proportion of the fishes associated with these platforms. More characteristic of platform fauna are the primarily deeper-dwelling rockfishes (genus Sebastes). "Shell mounds" are biogenic reefs that surround some of these platforms resulting from an accumulation of mollusk shells that have fallen from the shallow areas of the platforms mostly above the depth of partial removal. We found that shell mounds are moderately productive fish habitats, similar to or greater than natural rocky reefs in the region at comparable depths. The complexity and areal extent of these biogenic habitats, and the associated fish biomass and production, will likely be reduced after either partial or complete platform removal. Habitat augmentation by placing the partially removed platform superstructure or some other additional habitat enrichment material (e.g., rock boulders) on the seafloor adjacent to the base of partially removed platforms provides additional options to enhance fish production, potentially mitigating reductions in shell mound habitat.

  19. A new injectable biphasic hydrogel based on partially hydrolyzed polyacrylamide and nano hydroxyapatite, crosslinked with chromium acetate, as scaffold for cartilage regeneration

    Science.gov (United States)

    Koushki, N.; Tavassoli, H.; Katbab, A. A.; Katbab, P.; Bonakdar, S.

    2015-05-01

    Polymer scaffolds are applied in the field of tissue engineering as three dimensional structures to organize cells and present stimuli to direct generation of a desired damaged tissue. In situ gelling scaffolds have attracted great attentions, as they are structurally similar to the extra cellular matrix (ECM). In the present work, attempts have been made to design and fabricate a new injectable and crosslinkable biphasic hydrogel based on partially hydrolyzed polyacrylamide (HPAM), chromium acetate as crosslink agent and nanocrystalline hydroxyapatite (nHAp) as reinforcing and bioactive agent for repair and regeneration of damaged cartilage. The distinct characteristic of HPAM is the presence of carboxylate anion groups on its backbone which allows to engineer the structure of the hydrogel for the desired bioactivity with appropriate cells differentiation towards both soft and hard (bone) tissues. The synthesized hydrogel exhibited bifunctional behavior which was derived by its biphasic structure in which one phase was loaded with nano hydroxyapatite to provide integration capability by subchondral bones and fix the hydrogel at cartilage defect without a need for suturing. The other phase differentiates the rabbit adipogenic mesenchymal stem cells (MSCs) towards soft tissue. Rheomechanical spectrometry (RMS) was employed to study the kinetic of the gelation including induction time and rate, as well as to measure the ultimate elastic modulus of the optimum crosslinked hydrogel. Surface tension measurement was also performed to tailor the surface characteristics of the gels. In vitro culturing of the cells inside the crosslinked hydrogel revealed high viability and high differentiation of the encapsulated rabbit stem cells, providing that the chromium acetate level was kept below 0.2 wt%. Based on the obtained results, the designed and fabricated biphasic hydrogel exhibited high potential as carrier for the stem cells for cartilage tissue engineering application

  20. Beidellite and other natural low-cost sorbents to remove chromium and cadmium from water and wastewater

    Directory of Open Access Journals (Sweden)

    Callejas, P.

    2010-04-01

    Full Text Available Laboratory experiments were conducted to examine ability of clay minerals and organic matter to remove the cadmium(II and chromium(III ions from aqueous effluents. Sample materials for the experiments were taken in Poland and Spain. Their chemical composition, specific surface area, pH in water and potassium chloride, ion exchange capacity and absorption of Cr (III and Cd (II have been studied. The clay samples exhibited greater sorption capacity for Cr(III than for Cd(II while organic matter, especially brown coal, better sorbed Cd(II than Cr(III. The Langmuir binding strength parameter (k was always greater for Cr than for Cd. On the basis of the sequential extraction and microanalysis by SEM it was stated that iron oxides were not involved in the Cd ion binding while their role in Cr(III binding was essential. Ion binding by Fe oxides and their missing at exchangeable positions yields weak both susceptibility to leaching and mobility of Cr(III ions. Instead, Cd(II ions are mainly bound at exchangeable positions, susceptible to leaching.

    La industria y las urbes descargan sobre los ríos aguas que representan un factor importante en la contaminación medioambiental. La agricultura se ve afectada, siendo uno de los problemas el alto contenido en metales pesados presentes en el suelo o las aguas utilizadas para el riego. En este trabajo se expone la posibilidad de utilizar materiales de bajo costo, minerales arcillosos y carboníferos, tomados en España y Polonia, para remediar esta contaminación. Se ha estudiado su composición química, superficie específica, pH en agua y cloruro potásico, capacidad de intercambio iónica y absorción de Cr (III y Cd(II. Las muestras arcillosas mostraron mayor capacidad de absorción para el ion Cr(III que para el Cd(II, mientras que las orgánicas, especialmente la denominada “ brown coal” (lignito, fueron mejores adsorbentes del ion Cd. El parámetro k obtenido en las isotermas de absorci

  1. Multicentre prospective evaluation of implant-assisted mandibular bilateral distal extension removable partial dentures: patient satisfaction.

    Science.gov (United States)

    Wismeijer, Daniel; Tawse-Smith, Andrew; Payne, Alan G T

    2013-01-01

    To compare the levels of patient satisfaction with either conventional mandibular bilateral distal extension partial dentures or those assisted by bilateral distal implants. Forty-eight participants who were dissatisfied with their existing conventional mandibular distal extension dentures opposing complete maxillary dentures were selected for a multicentre prospective study in New Zealand, Colombia and the Netherlands. A control group of 12 participants in New Zealand received conventional mandibular partial dentures. Three test groups involving 36 participants in New Zealand (12), Colombia (12) and the Netherlands (12) received bilateral distal implants in the second molar regions. After conventional loading, the test group participants initially had healing caps placed on the distal implants providing support only, followed after approximately 6 months by ball abutments (retentive anchors) for support and retention. Patient outcomes were determined with questionnaires completed at specific stages of the study for up to 3 years. Visual analogue scale, Likert and oral health impact questionnaires before and after treatment indicated improved results. There were significantly improved parameters of overall satisfaction, stability, chewing and appearance after 3 years (P removable partial dentures are a preferable treatment option for patients with complaints about their conventional distal extension partial dentures. © 2011 John Wiley & Sons A/S.

  2. Maxillary rehabilitation using fixed and removable partial dentures with attachments: a clinical report.

    Science.gov (United States)

    dos Santos Nunes Reis, José Maurício; da Cruz Perez, Luciano Elias; Alfenas, Bruna Fernandes Moreira; de Oliveira Abi-Rached, Filipe; Filho, João Neudenir Arioli

    2014-01-01

    Despite requiring dental crown preparation and possible root canal treatment, besides the difficulty of clinical and laboratory repairs, and financial burden, the association between fixed (FPD) and removable partial dentures (RPD) by means of attachments is an important alternative for oral rehabilitation, particularly when the use of dental implants and FPDs is limited or not indicated. Among the advantages of attachment-retained RPDs are the improvements in esthetics and biomechanics, as well as correction of the buccal arrangement of anterior teeth in Kennedy Class III partially edentulous arches. This article describes the treatment sequence and technique for the use of attachments in therapy combining FPD/RPD. © 2013 by the American College of Prosthodontists.

  3. Short-term retrospective case series of implant-assisted removable partial dentures with locator abutments.

    Science.gov (United States)

    Ortiz-Puigpelat, Octavi; Gargallo-Albiol, Jordi; Hernández-Alfaro, Federico; Cabratosa-Termes, Josep

    2014-01-01

    The purpose of this retrospective case series was to report on the clinical performance of implant-assisted removable partial dentures (IARPDs) with Locator abutments in different partial edentulism situations, with a mean follow-up period of 28.6 months. Twelve consecutive patients were treated with IARPDs. A total of 24 implants were placed in the edentulous area. Minimum follow-up period was 12 months. Overall patient satisfaction, health of peri-implant tissues, survival of implants and abutments, and prosthetic complications were reported. Overall implant survival was 91.6%; two implants failed. No major complications were reported-only one IARPD metal framework broke. No Locator abutment loosening was reported. Within the limitations of this retrospective study, treatment with IARPDs can improve the patient's function, phonetics, and esthetics without the need for extensive bone regeneration surgeries and prosthodontic rehabilitations. However, well-designed prospective clinical studies on IARPDs are needed to support their long-term use.

  4. Removable partial dentures: Patient satisfaction and complaints in Makkah City, KSA

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    Mohsen K. Aljabri, BDS

    2017-12-01

    Full Text Available Objective: To assess the satisfaction level and complaints among patients using different types of removable partial dentures (RPDs in Makkah city, KSA. Methods: In this retrospective study, 551 patients who had received RPDs between February and December 2015 were contacted by telephone. One hundred patients responded, and 60 of them agreed to participate in the study. The participants were asked two questions to determine their satisfaction level and complaints with RPD usage, eating, communication, and aesthetics. Data were analysed statistically by chi-square, analysis of variance, and Scheffe's tests. Results: Of 60 patients, 35% were very satisfied, 21.7% were satisfied and 23.3% were nearly satisfied. However, only 20% were not satisfied. There were no significant differences in mean RPD satisfaction among different age groups and between sexes (P > 0.01. There was a significant difference in satisfaction among RPD type (P < 0.01. However, no significant differences were recorded between either metal and acrylic, or acrylic and flexible RPDs (P < 0.01. As many as 26.7% of respondents complained of aesthetic problems, 16.7% complained of pain during mastication, 10% complained of gag reflex, and 8.3% complained of phonetic problems. However, the majority of respondents (38.3% had no complaints. Conclusion: The majority of patients were satisfied with the quality of removable partial dentures treatment in Makkah city hospitals. Oral rehabilitation with RPDs should be applied with care when patients have high aesthetic demands. Keywords: Aesthetics, Dental prosthesis, Oral complaints, Patient satisfaction, Removable partial denture

  5. Patient satisfaction with laser-sintered removable partial dentures: A crossover pilot clinical trial.

    Science.gov (United States)

    Almufleh, Balqees; Emami, Elham; Alageel, Omar; de Melo, Fabiana; Seng, Francois; Caron, Eric; Nader, Samer Abi; Al-Hashedi, Ashwaq; Albuquerque, Rubens; Feine, Jocelyne; Tamimi, Faleh

    2018-04-01

    Clinical data regarding newly introduced laser-sintered removable partial dentures (RPDs) are needed before this technique can be recommended. Currently, only a few clinical reports have been published, with no clinical studies. This clinical trial compared short-term satisfaction in patients wearing RPDs fabricated with conventional or computer-aided design and computer-aided manufacturing (CAD-CAM) laser-sintering technology. Twelve participants with partial edentulism were enrolled in this pilot crossover double-blinded clinical trial. Participants were randomly assigned to wear cast or CAD-CAM laser-sintered RPDs for alternate periods of 30 days. The outcome of interest was patient satisfaction as measured using the McGill Denture Satisfaction Instrument. Assessments was conducted at 1, 2, and 4 weeks. The participant's preference in regard to the type of prosthesis was assessed at the final evaluation. The linear mixed effects regression models for repeated measures were used to analyze the data, using the intention-to-treat principle. To assess the robustness of potential, incomplete adherence, sensitivity analyses were conducted. Statistically significant differences were found in patients' satisfaction between the 2 methods of RPD fabrication. Participants were significantly more satisfied with laser-sintered prostheses than cast prostheses in regard to general satisfaction, ability to speak, ability to clean, comfort, ability to masticate, masticatory efficiency, and oral condition (Premovable partial dentures may lead to better outcomes in terms of patient satisfaction in the short term. The conclusion from this pilot study requires confirmation by a larger randomized controlled trial. ClinicalTrials.gov. A study about patient satisfaction with laser-sintered removable partial dentures; NCT02769715. Copyright © 2017 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

  6. Three-dimensional finite element analysis of implant-assisted removable partial dentures.

    Science.gov (United States)

    Eom, Ju-Won; Lim, Young-Jun; Kim, Myung-Joo; Kwon, Ho-Beom

    2017-06-01

    Whether the implant abutment in implant-assisted removable partial dentures (IARPDs) functions as a natural removable partial denture (RPD) tooth abutment is unknown. The purpose of this 3-dimensional finite element study was to analyze the biomechanical behavior of implant crown, bone, RPD, and IARPD. Finite element models of the partial maxilla, teeth, and prostheses were generated on the basis of a patient's computed tomographic data. The teeth, surveyed crowns, and RPDs were created in the model. With the generated components, four 3-dimensional finite element models of the partial maxilla were constructed: tooth-supported RPD (TB), implant-supported RPD (IB), tooth-tissue-supported RPD (TT), and implant-tissue-supported RPD (IT) models. Oblique loading of 300 N was applied on the crowns and denture teeth. The von Mises stress and displacement of the denture abutment tooth and implant system were identified. The highest von Mises stress values of both IARPDs occurred on the implants, while those of both natural tooth RPDs occurred on the frameworks of the RPDs. The highest von Mises stress of model IT was about twice that of model IB, while the value of model TT was similar to that of model TB. The maximum displacement was greater in models TB and TT than in models IB and IT. Among the 4 models, the highest maximum displacement value was observed in the model TT and the lowest value was in the model IB. Finite element analysis revealed that the stress distribution pattern of the IARPDs was different from that of the natural tooth RPDs and the stress distribution of implant-supported RPD was different from that of implant-tissue-supported RPD. When implants are used for RPD abutments, more consideration concerning the RPD design and the number or location of the implant is necessary. Copyright © 2016 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

  7. Relevance of variations in the opposing dentition for the functionality of fixed and removable partial dentures: a systematic review.

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    Pommer, Bernhard; Krainhöfner, Martin; Watzek, Georg; Tepper, Gabor; Dintsios, Charalabos-Markos

    2012-01-01

    The aim of this systematic review was to evaluate the functionality of fixed and removable partial dentures as test interventions in relation to variations in the opposing dentition and their prosthetic restoration. The abstracts identified in the respective databases were screened independently by two investigators. RCTs and uncontrolled studies were considered, provided the patients were included consecutively and the confounding variables were adequately monitored. Seventeen papers were included. The study and publication quality was assessed using a "biometric quality" tool showing an overall poor quality. The reported outcomes, such as survival rates, were in each case obtained from a single study. Two possible trends could be deduced for the endpoint longevity: (a) the first trend in favor of removable partial dentures, compared to fixed partial dentures, with a fully edentulous opposing arch fitted with a removable prosthesis; (b) the second trend in favor of implant-supported partial dentures, compared to conventionally fixed partial dentures, with natural opposing dentition or with a removable partial denture in the opposing arch. No evidence could be generated as to whether, and if so how, variations in the opposing dentition have a bearing on the decision to fit a partially edentulous arch with a fixed or removable partial denture.

  8. Relevance of Variations in the Opposing Dentition for the Functionality of Fixed and Removable Partial Dentures: A Systematic Review

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    Bernhard Pommer

    2012-01-01

    Full Text Available The aim of this systematic review was to evaluate the functionality of fixed and removable partial dentures as test interventions in relation to variations in the opposing dentition and their prosthetic restoration. The abstracts identified in the respective databases were screened independently by two investigators. RCTs and uncontrolled studies were considered, provided the patients were included consecutively and the confounding variables were adequately monitored. Seventeen papers were included. The study and publication quality was assessed using a “biometric quality” tool showing an overall poor quality. The reported outcomes, such as survival rates, were in each case obtained from a single study. Two possible trends could be deduced for the endpoint longevity: (a the first trend in favor of removable partial dentures, compared to fixed partial dentures, with a fully edentulous opposing arch fitted with a removable prosthesis; (b the second trend in favor of implant-supported partial dentures, compared to conventionally fixed partial dentures, with natural opposing dentition or with a removable partial denture in the opposing arch. No evidence could be generated as to whether, and if so how, variations in the opposing dentition have a bearing on the decision to fit a partially edentulous arch with a fixed or removable partial denture.

  9. Impact on Dietary Intake of Removable Partial Dentures Replacing a Small Number of Teeth.

    Science.gov (United States)

    Inomata, Chisato; Ikebe, Kazunori; Okada, Tadashi; Takeshita, Hajime; Maeda, Yoshinobu

    2015-01-01

    The aim of this study was to clarify the impact of wearing removable partial dentures (RPDs) replacing a small number of teeth on dietary intake. Participants had at least 20 teeth and were classified as Eichner B1 or B2. The participants underwent dental and oral examinations, and their dietary intake was assessed. Analysis of covariance showed that RPD wearers consumed more vegetables, n-3 fatty acids, calcium, vitamin A, and dietary fiber than nonwearers after adjusting for possible confounding factors. It is concluded that RPDs are effective for improving dietary intake even in participants who have lost a small number of teeth.

  10. New Clasp Assembly for Distal Extension Removable Partial Dentures: The Reverse RPA Clasp.

    Science.gov (United States)

    Hakkoum, Mohammad Ayham

    2016-07-01

    Several clasp types are used in distal extension removable partial dentures. In some cases the terminal abutments have only distal retentive undercuts that can be occupied by bar clasps; however, bar clasps may be contraindicated with no suitable alternative. This article presents a reasonable solution by introducing a new clasp design as a modification to the well-known RPA clasp. The design includes a mesial rest, proximal plate, and buccal retentive arm arising from the rest and extending to reach the distal retentive undercut. © 2015 by the American College of Prosthodontists.

  11. Removable Partial Denture in a Cleft Lip and Palate Patient: A Case Report

    Science.gov (United States)

    Özdemir, Eylem

    2008-01-01

    This clinical report described the oral rehabilitation of a cleft lip and palate patient with removable partial denture. Although implant-supported fixed treatment was presented as part of the optimum treatment plan to achieve the best result, the patient declined this option due to the significant financial burden. Persons with a congenital or craniofacial defect are unique, and oral problems must be evaluated individually to the most ideal treatment. The changes in appearance, function, and psychological wellbeing have an enormous impact on patients' personal lives and are rewarding for the maxillofacial prosthodontist providing this care. PMID:18955808

  12. The impact of rehabilitation using removable partial dentures and functionally orientated treatment on oral health-related quality of life: a randomised controlled clinical trial.

    Science.gov (United States)

    McKenna, Gerald; Allen, P Finbarr; O'Mahony, Denis; Cronin, Michael; DaMata, Cristiane; Woods, Noel

    2015-01-01

    This study aimed to compare two different tooth replacement strategies for partially dentate older patients; namely functionally orientated treatment according to the principles of the shortened dental arch (SDA) and conventional treatment using removable partial dentures (RPDs) using a randomised controlled clinical trial. The primary outcome measure for this study was impact on oral health-related quality of life (OHRQoL) measured using the short form of the oral health impact profile (OHIP-14). Patients aged 65 years and older were randomly allocated to two different treatment groups: the RPD group and the SDA group. For the RPD group each patient was restored to complete arches with cobalt-chromium RPDs used to replace missing teeth. For the SDA group, patients were restored to a premolar occlusion of 10 occluding pairs of natural and replacement teeth using resin bonded bridgework (RBB). OHRQoL was measured using the OHIP-14 questionnaire administered at baseline, 1 month, 6 months and 12 months after treatment intervention. In total, 89 patients completed the RCT: 44 from the RPD group and 45 from the SDA group. Analysis using a mixed model of covariance (ANCOVA) illustrated that treatment according to the SDA concept resulted in significantly better mean OHIP-14 scores compared with RPD treatment (premovable dentures in terms of impact on OHRQoL. Copyright © 2014 Elsevier Ltd. All rights reserved.

  13. Bending properties of Ce-TZP/A nanocomposite clasps for removable partial dentures.

    Science.gov (United States)

    Urano, Shinjiro; Hotta, Yasuhiro; Miyazaki, Takashi; Baba, Kazuyoshi

    2015-01-01

    Ceria-stabilized zirconia/alumina nanocomposite (Ce-TZP/A) has excellent fracture toughness and bending strength that could be useful for partial denture framework application. The aim of this study was to investigate the effects of three-dimensional (3D) geometry on the bending and fatigue properties of a model simulation of Ce-TZP/A clasps. Half oval-shaped Ce-TZP/A rods were prepared in six 3D designs. Specimens were either of standard (width divided by thickness: 2.0/1.0 mm) or flat type (2.5/0.8 mm) cross-sectional areas with taper ratios of 1.0, 0.8, or 0.6. As a comparison, cobalt-chromium (Co-Cr) alloy rods of the same shape as the Ce-TZP/A standard shape rod were prepared. All specimens were subjected to the cantilever test and loaded until fracture. They were also cyclically loaded 106 times with various constant displacements, and the maximum displacement prior to fracture was determined for each specimen. Three-dimensional finite element analysis (3D FEA), simulating the cantilever test, was performed to determine the stress distribution during loading. Specimens with the standard cross-sectional shape exhibited higher rigidity and higher fracture loads than the flat specimens by the cantilever test. In addition, lower taper ratios were consistently associated with larger displacements at fracture. Fatigue tests revealed that the maximum displacement prior to fracture of Ce-TZP/A specimens was comparable to that of Co-Cr alloy specimens. The 3D FEA showed that specimens with a taper ratio of 0.6 had the least stress concentration. Ce-TZP/A clasp specimens with a standard cross-sectional shape and a 0.6 taper ratio exhibited the best bending properties among those tested.

  14. Comparison of Treatment Outcomes in Partially Edentulous Patients with Implant-Supported Fixed Prostheses and Removable Partial Dentures.

    Science.gov (United States)

    Nogawa, Toshifumi; Takayama, Yoshiyuki; Ishida, Keita; Yokoyama, Atsuro

    The aim of this study was to compare masticatory performance, occlusal force, and oral health-related quality of life (OHRQoL) in patients with mandibular distal-extension edentulism between those with implant-supported fixed prostheses (ISFPs) and those with removable partial dentures (RPDs), and to evaluate relationships among them. Subjects were recruited from patients using ISFPs or RPDs for mandibular distal-extension edentulism. Masticatory performance was evaluated based on the glucose extracted from chewed gummy jelly. Occlusal force was measured with a pressure-sensitive sheet, and data were subjected to computer analysis. The Japanese version of the Oral Health Impact Profile (OHIP-J) was used to evaluate OHRQoL. The masticatory performance, occlusal force, and OHIP-J scores of the ISFP and RPD groups were compared using the Wilcoxon rank-sum test. The relationships among the variables were analyzed using the Spearman rank correlation coefficient test. Multivariate logistic regression analysis was employed with the OHIP-J score as a dependent variable. Nineteen patients with ISFPs and 25 patients with RPDs participated in this study. No significant difference was observed between the two groups with regard to masticatory performance and occlusal force. The OHIP-J score was significantly lower in the ISFP group than in the RPD group. The OHIP-J score had no significant correlation with masticatory performance, but was significantly correlated with occlusal force and the prosthetic method. Multivariate logistic regression analysis showed that younger age, RPDs, and lower occlusal force were significantly associated with a higher OHIP-J summary score. The present results suggest that the difference in masticatory performance and occlusal force between ISFPs and RPDs is small, but ISFPs are superior to RPDs with regard to OHRQoL in patients with mandibular distal-extension edentulism. In addition, there appears to be a slight correlation between the OHIP

  15. PULPAL BLOOD FLOW CHANGES IN ABUTMENT TEETH OF REMOVABLE PARTIAL DENTURES

    Science.gov (United States)

    Kunt, Göknil Ergün; Kökçü, Deniz; Ceylan, Gözlem; Yılmaz, Nergiz; Güler, Ahmet Umut

    2009-01-01

    The purpose of this study was to investigate the effect of tooth supported (TSD) and toothtissue supported (TTSD) removable partial denture wearing on pulpal blood flow (PBF) of the abutment teeth by using Laser Doppler Flowmeter (LDF). Measurements were carried out on 60 teeth of 28 patients (28 teeth and 12 patients of TTSD group, 32 teeth and 16 patients of TSD group) who had not worn any type of removable partial dentures before, had no systemic problems and were non smokers. PBF values were recorded by LDF before insertion (day 0) and after insertion of dentures at day 1, day 7 and day 30. Statistical analysis was performed by student t test and covariance analyses of repeated measurements. In the group TTSD, the mean values of PBF decreased statistically significantly at day 1 after insertion when compared with PBF values before insertion (p<0,01). There was no statistically significant difference among PBF mean values on 1st, 7th and 30th day. However, in the group TSD, there was no statistically significant difference among PBF mean values before insertion and on 1st, 7th and 30th day. In other words, PBF mean values in group TSD continued without changing statistically significant on 1st, 7th and 30th day. TTSD wearing may show negative effect on the abutment teeth due to decreasing basal PBF. PMID:20001995

  16. Clinical evaluation of removable partial dentures on the periodontal health of abutment teeth: a retrospective study.

    Science.gov (United States)

    Dula, Linda J; Ahmedi, Enis F; Lila-Krasniqi, Zana D; Shala, Kujtim Sh

    2015-01-01

    The aim of this retrospective study was to evaluate the effect of removable partial dentures in periodontal abutment teeth in relation to the type of denture support and design of RPD in a five-year worn period. Methods : A total of 64 patients with removable partial dentures (RPDs), participated in this study. It were examined ninety-one RPDs. There were seventy-five RPDs with clasp-retained and sixteenth were RPDs with attachments. There were 28 females and 36 males, aged between 40-64 years, 41 maxillary and 50 mandible RPDs. For each subjects the following data were collected: denture design, denture support, and Kennedy classification. Abutment teeth were assessed for plaque index (PI), calculus index (CI), blending on probing (BOP), probing depth (PD), gingival recession (GR), tooth mobility (TM). Level of significance was set at pdenture support of RPD, BOP, PD, PI, GR, CI and TM-index showed no statistically significant difference. Based on the denture design of RPD's, BOP, PD, PI, CI, and TM-index proved no statistically significant difference. Except GR-index according to denture design confirmed statistically significant difference in RPD with clasp pdentures and below the clasp arms in abutment teeth.

  17. Pulpal blood flow changes in abutment teeth of removable partial dentures

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    Göknil Ergün Kunt

    2009-11-01

    Full Text Available The purpose of this study was to investigate the effect of tooth supported (TSD and toothtissue supported (TTSD removable partial denture wearing on pulpal blood flow (PBF of the abutment teeth by using Laser Doppler Flowmeter (LDF.Measurements were carried out on 60 teeth of 28 patients (28 teeth and 12 patients of TTSD group, 32 teeth and 16 patients of TSD group who had not worn any type of removable partial dentures before, had no systemic problems and were non smokers. PBF values were recorded by LDF before insertion (day 0 and after insertion of dentures at day 1, day 7 and day 30. Statistical analysis was performed by student t test and covariance analyses of repeated measurements.In the group TTSD, the mean values of PBF decreased statistically significantly at day 1 after insertion when compared with PBF values before insertion (p<0,01. There was no statistically significant difference among PBF mean values on 1st, 7th and 30th day. However, in the group TSD, there was no statistically significant difference among PBF mean values before insertion and on 1st, 7th and 30th day. In other words, PBF mean values in group TSD continued without changing statistically significant on 1st, 7th and 30th day.TTSD wearing may show negative effect on the abutment teeth due to decreasing basal PBF.

  18. Usage of removable partial dentures in Saudi male patients after 1 year telephone interview

    Science.gov (United States)

    Akeel, Riyadh

    2010-01-01

    Objective The success of removable partial dentures (RPDs) is partly dependent on patients’ acceptance and compliance in using them. The purpose of this study was to describe the usage of removable partial dentures (RPDs) by patients 1 year after insertion and to evaluate the factors that influence their denture usage. Methods Forty-seven patients who received 75 new RPDs at the undergraduate clinic of College of Dentistry, King Saud University, were contacted by telephone 1 year later for an interview. The questions covered denture usage, patient’s satisfaction and reasons for non-use. Results Results showed that 36% of patients discarded or occasionally used their RPDs. There was no significant association between denture usage and RPD experience, location or Kennedy classification. A significantly more RPD rejection was found when it was opposed by natural teeth or complete denture. The most quoted reason for RPD rejection was pain and discomfort. Conclusion Despite the short follow-up period, RPDs were poorly accepted by patients treated by undergraduate students. PMID:23960487

  19. Chewing efficiency and occlusal forces in PMMA, acetal and polyamide removable partial denture wearers.

    Science.gov (United States)

    Macura-Karbownik, Anna; Chladek, Grzegorz; Żmudzki, Jarosław; Kasperski, Jacek

    2016-01-01

    Thermoplastic materials, such as acetal (AC) and polyamide (PA), constitute an alternative to polymethyl methacrylate (PMMA) based resins as the materials for removable partial dentures. However, none of the previous studies compared chewing efficiency and occlusal forces in the wearers of dentures made of various materials. Therefore, the aim of this study was to determine and compare the chewing efficiency and occlusal forces in PMMA, PA and AC RPDs' wearers. The hypothesis was that the type of denture base material shows a significant effect on chewing efficiency (expressed as a degree of food fragmentation) and occlusal force. The experiment included the group of 30 patients using removable partial dentures. The dentures made of PMMA, acetal and polyamide were tested in each patient. Each denture was worn for 90 days, with a random sequence of the denture manufacturing and insertion. After 7, 30 and 90 days of each denture wear, chewing efficiency coefficient was determined with the aid of a sieving method, and occlusal force was measured with a dynamometer. The use of dentures made of PMMA or acetal was reflected by a marked increase in chewing efficiency and occlusal force. None of these parameters changed significantly with the time of denture wear. Moreover, no significant correlation was found between chewing efficiency and occlusal forces. Denture base material exerts significant effects on the degree of food fragmentation and the level of occlusal forces. The use of dentures and clasps made of materials with lower modulus of elasticity is associated with lower chewing efficiency and lower occlusal forces.

  20. The Fatigue Behavior of Restorations Used Under the Rest of Removable Partial Denture

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    Farzin M

    2014-09-01

    Full Text Available Statement of Problem: The question about resistance of resin composites under rest in removable partial denture (RPD is still unanswered. It is important to find the strongest material that withstands the applied stresses when used under RPD components. Objectives: To evaluate and compare the fatigue behavior of amalgam and composite restorations used under the rest of the removable partial denture. Materials and Methods: Forty-five permanent human upper premolars were prepared with standard class II DO cavities and divided into 3 groups of specimens (n=15 for each group. Group I was filled with amalgam (Dispersalloy, group II and III were filled with resin composite (Flitek Z250 and Tetric ceram, respectively. The teeth were stored in distilled water for 14 days before testing. After thermocycling, the “staircase” approach was used to determine the flexural fatigue limits (FFL. The mean differences were evaluated using One-Way ANOVA and post hoc test. Results: A strong significant differences of flexural fatigue strength have been found between amalgam and composite groups (P<0.001. There was no significant difference between two groups of resin composite (P=0.1. Conclusions: To achieve more flexural fatigue strength in the rest seats, the use of resin composite in comparison with amalgam is recommended.

  1. Strain Distribution in a Kennedy Class I Implant Assisted Removable Partial Denture under Various Loading Conditions

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    Reza Shahmiri

    2013-01-01

    Full Text Available Purpose. This in vitro study investigates how unilateral and bilateral occlusal loads are transferred to an implant assisted removable partial denture (IARPD. Materials and Methods. A duplicate model of a Kennedy class I edentulous mandibular arch was made and then a conventional removable partial denture (RPD fabricated. Two Straumann implants were placed in the second molar region, and the prosthesis was modified to accommodate implant retained ball attachments. Strain gages were incorporated into the fitting surface of both the framework and acrylic to measure microstrain (μStrain. The IARPD was loaded to 120Ns unilaterally and bilaterally in three different loading positions. Statistical analysis was carried out using SPSS version 18.0 (SPSS, Inc., Chicago, IL, USA with an alpha level of 0.05 to compare the maximum μStrain values of the different loading conditions. Results. During unilateral and bilateral loading the maximum μStrain was predominantly observed in a buccal direction. As the load was moved anteriorly the μStrain increased in the mesial area. Unilateral loading resulted in a twisting of the structure and generated a strain mismatch between the metal and acrylic surfaces. Conclusions. Unilateral loading created lateral and vertical displacement of the IARPD. The curvature of the dental arch resulted in a twisting action which intensified as the unilateral load was moved anteriorly.

  2. Partial extracorporeal carbon dioxide removal using a standard continuous renal replacement therapy device: a preliminary study.

    Science.gov (United States)

    Quintard, Jean-Marie; Barbot, Olivier; Thevenot, Florence; de Matteis, Olivier; Benayoun, Laurent; Leibinger, Frank

    2014-01-01

    To test the feasibility, safety, and efficacy of partial extracorporeal CO2 removal (PECCO2R) using a standard continuous renal replacement (CRRT) device with a pediatric oxygenation membrane introduced into the circuit in a serial manner. In this retrospective single-center study, we have studied mechanically ventilated patients with persistent significant respiratory acidosis and acute renal failure requiring ongoing CRRT. Sixteen patients were treated with our PECCO2R device. PaCO2 and arterial pH were measured before as well as at 6 and 12 hours after PECCO2R implementation. Hemodynamic parameters were continuously monitored. Our PECCO2R system was efficient to significantly reduce PaCO2 and increase arterial pH. The median PaCO2 before treatment was 77 mm Hg (59-112) with a median reduction of 24 mm Hg after 6 hours and 30 mm Hg after 12 hours (31% and 39%, respectively). The median pH increase was 0.16 at 6 hours and 0.23 at 12 hours. Partial extracorporeal CO2 removal treatment had no effect on oxygenation. No complication was observed. Our PECCO2R approach based on the simple introduction of a pediatric extracorporeal membrane oxygenation membrane into the circuit of a standard CRRT device is easy to implement, safe, and efficient to improve respiratory acidosis.

  3. The Use of Digital Impressions to Fabricate Tooth-Supported Partial Removable Dental Prostheses: A Clinical Report.

    Science.gov (United States)

    Mansour, Mohamed; Sanchez, Eliana; Machado, Camilo

    2016-08-01

    Impression making is a critical step in the fabrication of a partial removable dental prosthesis (RDP). A technique is described for making final impressions to fabricate partial RDPs for Kennedy class III patients using a computer-aided design and computer-assisted manufacturing digital impression system. © 2015 by the American College of Prosthodontists.

  4. The effect of implant-supported removable partial dentures on oral health quality of life.

    Science.gov (United States)

    Gates, W Day; Cooper, Lyndon F; Sanders, Anne E; Reside, Glenn J; De Kok, Ingeborg J

    2014-02-01

    Removable partial dentures (RPDs) represent standard treatment for partial edentulism despite major shortcomings. To alleviate these shortcomings, endosseous implants provide support and stability as well as contribute to maintenance of alveolar bone. This prospective, within subject, time series study evaluated patient-based outcomes of RPDs compared to implant-supported removable partial dentures (ISRPDs). The study hypothesis was that the ISRPD would substantially improve oral health quality of life for patients. Seventeen patients requesting new mandibular Kennedy I or II RPDs received one 6-mm dental implant in one or both of the posterior edentulous areas. After healing, conventional RPDs were fabricated and delivered. Twelve weeks later, second-stage surgery was performed, and ball abutments with Clix attachments were inserted, thereby converting the prostheses to ISRPDs. Oral health quality of life was evaluated using the 49-item Oral Health Impact Profile (OHIP-49) questionnaire. The OHIP-49 was administered prior to treatment (baseline), at 6 and 12 weeks following RPD delivery and at 6 and 12 weeks following ISRPD conversion. Radiographic evaluation was performed at 6 and 12 weeks following ISRPD conversion. In statistical analysis, a fixed-slope random intercept variance components model took account of the multiple observations per person over time. In 17 subjects, 29 of 30 implants survived. The failed implant was replaced without complications. Abutment complications were limited to one abutment loosening and one attachment replacement. Minor prosthodontic complications were recorded. The OHIP-49 score reduced by 11.8 points, on average, at 12 weeks following ISRPD conversion (P = 0.011). Patients reported improved oral health following conversion to an ISRPD from RPD. The ISRPD involving short implants is one treatment option that should be considered when treatment planning Kennedy Class I and II patients. © 2012 John Wiley & Sons A/S.

  5. Multicentre prospective evaluation of implant-assisted mandibular removable partial dentures: surgical and prosthodontic outcomes.

    Science.gov (United States)

    Payne, Alan G T; Tawse-Smith, Andrew; Wismeijer, Daniel; De Silva, Rohana K; Ma, Sunyoung

    2017-01-01

    To determine implant survival and prosthodontic maintenance of implant-assisted mandibular removable partial dentures in a multicentre prospective study up to 10 years. Forty-eight participants with mandibular distal extension partial dentures were selected. A control group of 12 New Zealand participants had new conventional mandibular partial dentures made. Three test groups of 36 participants in New Zealand (n = 12), the Netherlands (n = 12) and Colombia (n = 12) had bilateral distal implants placed. Surgical and prosthodontic outcomes were documented with only healing caps placed (Stage 1) and with an attachment system (Stage 2). No implants failed after 3 years. Four late implant failures in three participants occurred in New Zealand (two unilateral implant failures after 5 and 8 years and two bilateral implant failures in the same participant after 6 and 10 years); two unilateral late implant failures occurred in the Netherlands and no late failures in Colombia. Implant survival rate was 92% by 10 years. Resonance frequency measurements were taken at surgery implant stability quotient (ISQ) 62.44 ± 7.46; range 40 - 79), baseline (ISQ 63.22 ± 6.17; range 50 - 74) and after 3 years (ISQ 66.38 ± 6.77; range 55 - 83). In New Zealand and Colombia, measured crestal bone levels were 2.03 ± 0.71 mm and 2.20 ± 0.81 mm, respectively, at baseline and 3 years. For Stage I, principal prosthodontic maintenance issues were loose healing caps among 10 New Zealand participants, four Colombian participants and one Netherlands participant. For Stage 2, matrix activation and overdenture puncture fractures resulted in 41 events (25 participants) in New Zealand over 10 years, whilst over 3 years, there were 14 events in nine Colombian participants and six events in five Netherlands participants. This clinical multicentre research complements previous case reports, case series, retrospective and prospective studies on the notion of implant

  6. Restoration of the Occlusal Vertical Dimension with an Overlay Removable Partial Denture: A Clinical Report.

    Science.gov (United States)

    Zanardi, Piero Rocha; Santos, Mayara Silva; Stegun, Roberto Chaib; Sesma, Newton; Costa, Bruno; Laganá, Dalva Cruz

    2016-10-01

    The process of tooth loss throughout life associated with severe occlusal wear may pose a challenge in the rehabilitation of partially edentulous arches. In these cases, many therapeutic procedures are necessary because each tooth must be restored to obtain the correct anatomical contour and recover the occlusal vertical dimension (OVD). A removable partial denture (RPD) with occlusal/incisal coverage, also known as an overlay RPD, is an alternative treatment option with fewer interventions, and, consequently, lower cost. This clinical report reviews the principles involved in the clinical indication for an overlay RPD, as well as the necessary planning and execution, to discuss the feasibility and clinical effectiveness of this treatment, identifying the indications, advantages, and disadvantages of this procedure through the presentation of a clinical case. The overlay RPD can be an alternative treatment for special situations involving partially edentulous arches in patients who need reestablishment of the OVD and/or realignment of the occlusal plane, and it can be used as a temporary or definitive treatment. The main advantages of this type of treatment are its simplicity, reversibility, and relatively low cost; however, further studies are needed to ensure the efficacy of this treatment option. © 2015 by the American College of Prosthodontists.

  7. Oral health-related quality of life and complications after treatment with partial removable dental prosthesis

    DEFF Research Database (Denmark)

    Al-Imam, H; Özhayat, E B; Benetti, A R

    2016-01-01

    The aims of this study were to measure and describe the oral health-related quality of life (OHRQoL) and to identify the complications caused by partial removable dental prosthesis (RDPs) in patients 1-5 years after treatment. Complications were identified in 65 patients who were treated with 83......-up examinations. Problems with eating and appearance registered at pre-treatment were improved at baseline and after 1-5 years. Problems with dentures that had been registered pre-treatment were improved at baseline but reoccurred after 1-5 years. The two most frequent complications were ill-fitting RDPs...... and inflammation of the oral mucosa, followed less frequently by fractures of the clasps. Treatment with RDPs improved OHRQoL, but denture-related problems partly remained, and new problems related to RDPs occurred 1-5 years after treatment. The two most frequent complications were ill-fitting RDPs...

  8. Impression Procedures for Metal Frame Removable Partial Dentures as Applied by General Dental Practitioners.

    Science.gov (United States)

    Fokkinga, Wietske A; van Uchelen, Judith; Witter, Dick J; Mulder, Jan; Creugers, Nico H J

    2016-01-01

    This pilot study analyzed impression procedures for conventional metal frame removable partial dentures (RPDs). Heads of RPD departments of three dental laboratories were asked to record features of all incoming impressions for RPDs during a 2-month period. Records included: (1) impression procedure, tray type (stock/custom), impression material (elastomer/alginate), use of border-molding material (yes/no); and (2) RPD type requested (distal-extension/tooth-bounded/combination). Of the 132 total RPD impressions, 111 (84%) involved custom trays, of which 73 (55%) were combined with an elastomer. Impression border-molding material was used in 4% of the cases. Associations between impression procedure and RPD type or dentists' year/university of graduation were not found.

  9. Severe Groin Pain Following Transobturator Tape Procedure Necessitating Partial Removal of the Tape

    Directory of Open Access Journals (Sweden)

    Gökçe Anık İlhan

    2016-01-01

    Full Text Available Groin pain after transobturator tape (TOT procedure can occur; however, severe groin pain and difficulty in ambulating requring exploration of the obturator compartment and surgical excision of the tape is uncommon. We present a case with severe groin pain after uncomplicated TOT in which the patient could not stand the pain despite conservative treatment. Unlike most cases presented in the literature, the pain could only be releived by partial removal of the tape. Although TOT is an effective and safe procedure in the treatment of stress urinary incontinance, obturator nerve entrapment may rarely occur and mesh dissection and excision may be the only choice to releive the pain in these patients with untolerable severe symptoms.

  10. [Evaluation of effects of quality scale for removable partial dentures in clinical application].

    Science.gov (United States)

    Lv, Jun-bang; Wu, Hui-liang; Zhang, Yan; Ke, Xiang-kang; Cao, Fu-xi; Gu, Liang; Wang, Xi-cai

    2013-02-01

    To evaluate the effects of quality scale for removable partial dentures (RPD)in clinical application. Quality scale for removable partial dentures was designed. Twelve items were devised for visual survey and try-in in base, artificial teeth, clasp, rest, connector and adjustment. The assessments were divided into 3 grades A, B and C. Four commercial dental laboratories were divided into experimental group and control group randomly. All RPD made in two groups were given score with the quality scale by single-blind method. In the experimental group,the technicians were familiar with the quality scale. The assessments were periodically feedbacked to administrative staffs and exchanges were carried out between doctors and technicians by telephone. No feedback information was provided in the control group. The assessments were compared between the two groups. The data was analyzed with SPSS17.0 software package. The scores of assessments for base, artificial teeth, clasp, rest, connector and adjustment in the experimental group were greater than that in the control group. The difference was significant between the two groups by analysis of variance (P<0.01). The grade A and C for RPD used acrylic resin, flexible resin and cast framework in the experimental group was 27.2%,39.5%,40.6% and 9.2%, 7.9%,7.2%, respectively. The grade B was in the majority. In the control group, the grade A and C was 9.4%,15.6%,15% and 40.6%,23.6%,25%,respectively. The majority was grade B and the grade C was significantly higher than the experimental group(P<0.05). Applying the quality scale of RPD can improve the fabricating quality of prosthesis.

  11. Adsorbent material based on passion-fruit wastes to remove lead (Pb), chromium (Cr) and copper (Cu) from metal-contaminated waters

    Science.gov (United States)

    Campos-Flores, Gaby; Castillo-Herrera, Alberto; Gurreonero-Fernández, Julio; Obeso-Obando, Aída; Díaz-Silva, Valeria; Vejarano, Ricardo

    2018-04-01

    The aim of the present work was to evaluate the feasibility of passion-fruit shell (PFS) biomass as adsorbent material to remove heavy metals from contaminated waters. Model mediums were used, which were composed of distilled water and the respective metal: lead (Pb), chromium (Cr) and copper (Cu), with a dose of 10g of dry PFSbiomass per liter of medium. The residual concentration of each metal was determined by Atomic Absorption Spectrophotometry (AAS). A good adsorption capacity was exhibited by this agro industrial waste, achieving removal levels of 96,93 and 82% for Pb, Cr and Cu, respectively. In addition, the results obtained showed an adequate fit to the Freundlich model (R2 > 0.91), on the basis of which, the following values of adsorption capacity (k: 1.7057, 0.6784, 0.3302) and adsorption intensity (n: 0.6869, 2.3474, 1.0499), for Pb, Cr and Cu respectively, were obtained. Our results suggest that Pb, Cr and Cu ions can be removed by more than 80% by using this agro industrial waste, which with a minimum treatment could be used as an adsorbent material in the treatment of metal-contaminated waters.

  12. A comparative study with biologically and chemically synthesized nZVI: applications in Cr (VI) removal and ecotoxicity assessment using indigenous microorganisms from chromium-contaminated site.

    Science.gov (United States)

    Ravikumar, K V G; Kumar, Deepak; Rajeshwari, A; Madhu, G M; Mrudula, P; Chandrasekaran, Natarajan; Mukherjee, Amitava

    2016-02-01

    In the present communication, we report a comparative study of Cr (VI) removal using biologically synthesized nano zero valent iron (BS-nZVI) and chemically synthesized nZVI (CS-nZVI), both immobilized in calcium alginate beads. The parameters like initial Cr (VI) concentration, nZVI concentration, and the contact time for Cr (VI) removal were optimized based on Box-Behnken design (BBD) by response surface modeling at a constant pH 7. Under the optimized conditions (concentration of nZVI = 1000 mg L(-1), contact time = ∼ 80 min, and initial concentration of Cr (VI) = 10 mg L(-1)), the Cr (VI) removal by the immobilized BS-nZVI and CS-nZVI alginate beads was 80.04 and 81.08 %, respectively. The adsorption of Cr (VI) onto the surface of alginate beads was confirmed by scanning electron microscopy with energy-dispersive x-ray spectroscopy (SEM-EDX), Fourier transform infrared spectroscopy (FT-IR), and Brunauer-Emmett-Teller (BET) analysis. The applicability of the process using both the sorbents was successfully test medium Cr (VI) spiked environmental water samples. In order to assess the ecotoxic effects of nZVI, the decline in cell viability, generation of intracellular reactive oxygen species (ROS), cell membrane damage, and biouptake was studied at 1000 mg L(-1) concentration, with five indigenous bacterial isolates from chromium-contaminated lake sediments and their consortium.

  13. [Developing a plan of treatment with a cast metal frame removable partial denture].

    Science.gov (United States)

    Witter, D J; Barèl, J C; Keltjens, H M A M; de Baat, C; Creugers, N H J

    2011-02-01

    When considering prosthetic replacement of absent teeth, a treatment plan is necessary. In evaluating whether replacement of teeth is sensible, the causes and consequences of tooth loss must be considered. This concerns information about problems having to do with the patient, potential complications, purely prosthodontic problems, and specific problems. The patient-related problems require collecting data through patient history as well as a clinical and radiologic examination. Complications are risk-factors which negatively influence the prognosis of general health or of a treatment. Potential complications should be eliminated as much as possible through a preliminary treatment. Purely prosthodontic problems are conditions in the area of absence of several teeth or parts of them, and in the area of occlusal and mandibular stability and articulation. Specific problems may be related to inadequate interocclusal space and the quality of the abutment teeth. A cast metal frame removable partial denture may be a relatively inexpensive and minimally treatment alternative for an expensive and complicated treatment with 1 or more fixed partial dentures.

  14. [Influence of attachment type on stress distribution of implant-supported removable partial dentures].

    Science.gov (United States)

    Yang, Xue; Rong, Qi-guo; Yang, Ya-dong

    2015-02-18

    To compare influences of different retention attachments on stress among supporting structures. By 3-dimensional laser scanner and reverse engineering computer aided design (CAD) software, a basic partially edentulous digital model with mandibular premolar and molar missing was established. Implant attachment and removable partial dentures (RPD) were added into the basic model to build three kinds of models: RPD only, RPD + implant + Locator attachment, and RPD + implant + Magfit attachment. Vertical and inclined loads were put on artificial teeth unilaterally. By means of 3-dimensional finite element analysis, the stress distribution and displacement of the main supportive structures were compared. A complete 3-dimensional finite element model was established, which contained tooth structure, and periodontal structures. The displacement of the denture was smaller in Locator (9.38 μm vertically, 45.48 μm obliquely) and Magfit models (9.54 μm vertically, 39.45 μm obliquely) compared with non-implant RPD model (95.27 μm vertically, 155.70 μm obliquely). Compared with the two different attachments, cortical bone stress value was higher in Locator model (Locator model 10.850 MPa vertically, 43.760 MPa obliquely; Magfit model 7.100 MPa vertically, 19.260 MPa obliquely).The stress value of abutment periodontal ligamentin Magfit model (0.420 MPa vertically) was lower than that in Locator model (0.520 MPa vertically). The existence of implant could reduce maximum von Mises value of each supportive structure when Kennedy I partially edentulous mandible was restored. Comparing the structure of Magfit and Locator attachment, the contact of Magfit attachment was rigid, while Locator was resilient. Locator attachment could improve stability of the denture dramatically. Locator had stronger effect on defending horizontal movement of the denture.

  15. [Treatment of removable partial dentures. 2. Causes and consequences of a reduced occlusal system].

    Science.gov (United States)

    Witter, D J; Barèl, J C; de Baat, C; Keltjens, H M A M; Creugers, N H J

    2011-01-01

    The occlusal system is part of the orofacial system and consists of the maxillary and mandibular alveolar ridge and teeth which are occluding or not or the removable denture teeth. The most prevalent causes of loss of teeth are insufficient oral self care or inadequate professional oral healthcare service. A reduced dentition can be described in terms of diastemas in the anterior region and number of occluding pairs of (pre)molars, differentiated as interrupted or shortened dental arches. Characteristic of a healthy functional occlusal system are the absence of pathology and the possibility to practice all oral functions without inconvenience. The consequences of a reduced occlusal system may be overload and/or migration of teeth, mandibular instability, and impaired esthetics and chewing function. Morphological and functional alterations can be considered to be adaptations to changed situations or to be pathological. The distinction between adaptation and pathology cannot be sharply defined. If prosthetic replacement of teeth is needed, the trend is to avoid removable partial dentures.

  16. Removable partial dentures vs overdentures in children with ectodermal dysplasia: two case reports.

    Science.gov (United States)

    Maroulakos, G; Artopoulou, I I; Angelopoulou, M V; Emmanouil, D

    2016-06-01

    Ectodermal dysplasia (ED) represents a disorder group characterised by abnormal development of the ectodermal derivatives. Removable partial dentures (RPD), complete dentures (CD) or overdentures (OD) are most often the treatment of choice for young affected patients. Prosthetic intervention is of utmost importance in the management of ED patients, as it resolves problems associated with functional, aesthetic, and psychological issues, and improves a patient's quality of life. However, few studies present the principles and guidelines that can assist in the decision-making process of the most appropriate removable prosthesis. The purpose of this study was to suggest a simple treatment decision-making algorithm for selecting an effective and individualised rehabilitative treatment plan, considering different parameters. The cases and treatment of two young ED patients are described and each one was treated with either RPDs or ODs. Periodic recalls were employed to manage problems, and monitor the changes associated with occlusion and fit of the prostheses in relation to each patient's growth. Both patients were followed up for more than 2 years and reported significant improvement in their appearance, masticatory function, and social behaviour as a result of the prosthetic rehabilitation. The main factors guiding the decision process towards the choice of an RPD or an OD are the presence of posterior natural teeth, facial aesthetics, lip support, number and size of existing natural teeth, and the occlusal vertical dimension.

  17. Reorientation simplified: A device for recording and reproducing the path of insertion for removable partial dentures

    Directory of Open Access Journals (Sweden)

    Vaibhav D Kamble

    2014-01-01

    Full Text Available Aim: The record of path of insertion on the dental cast is part of the dentist′s work authorization to the dental laboratory technician. The path of insertion record enables the dental technician to replace the cast on a surveyor in the same position that the dentist selected. Analysis of factors that influence the path of insertion should determine a path of insertion that will reduce the potential for dislodgement and promote stability of removable partial denture (RPD. Materials and Methods: The recording of the relation of a cast to a dental surveyor and the transfer of this relationship to the dental laboratory may be done by tripodization, by scoring the base of the cast, or by cementing a reference pin on the cast. Conclusion: Recording the established path of insertion can be difficult when the procedure uses a cemented pin and the casts are mounted in an articulator. This article describes a procedure for innovative dowel pin and sleeve device to record the path of insertion of RPDs, which serves the same purpose as the cemented pin but can be easily removed and replaced.

  18. Chromium allergy

    DEFF Research Database (Denmark)

    Hansen, M B; Johansen, J D; Menné, Torkil

    2003-01-01

    Most studies investigating chromium allergy have been performed with Cr(VI). However, real exposure to chromium from leather products includes both Cr(III) and Cr(VI). We have determined and compared the minimum elicitation threshold (MET) concentration for Cr(III) and Cr(VI) in Cr......(III) was concluded to play an important role in chromium allergy, because Cr(III) and Cr(VI) were both capable of eliciting eczema at low concentrations. Rather than regarding chromium dermatitis as a result of Cr(VI) allergy alone, it may be more correct to consider it as a result of a combined Cr(III) and Cr...

  19. Treatment of chromium contaminated soil using bioremediation

    Science.gov (United States)

    Purwanti, Ipung Fitri; Putri, Tesya Paramita; Kurniawan, Setyo Budi

    2017-11-01

    Chromium contamination in soil occurs due to the disposal of chromium industrial wastewater or sludge that excess the quality standard. Chromium concentration in soil is ranged between 1 to 300 mg/kg while the maximum health standard is 2.5 mg/kg. Bioremediation is one of technology that could be used for remediating heavy metal contamination in soil. Bacteria have an ability to remove heavy metal from soil. One bacteria species that capable to remove chromium from soil is Bacillus subtilis. The aim of this research was to know the chromium removal percentage in contaminated soil by Bacillus subtilis. Artificial chromium contaminated soil was used by mixing 425gram sand and chromium trichloride solution. Concentration of chromium added into the spiked soil were 50, 75, and 100 mg/L. During 14 days, pH, soil temperature and soil moisture were tested. Initial and final number of bacterial colony and chromium concentration analysed. The result showed that the highest percentage of chromium removal was 11% at a chromium concentration of 75 mg/L

  20. Final-impression techniques and materials for making complete and removable partial dentures.

    Science.gov (United States)

    Jayaraman, Srinivasan; Singh, Balendra P; Ramanathan, Balasubramanian; Pazhaniappan Pillai, Murukan; MacDonald, Laura; Kirubakaran, Richard

    2018-04-04

    Endentulism is relatively common and is often treated with the provision of complete or partial removable dentures. Clinicians make final impressions of complete dentures (CD) and removable partial dentures (RPD) using different techniques and materials. Applying the correct impression technique and material, based on an individual's oral condition, improves the quality of the prosthesis, which may improve quality of life. To assess the effects of different final-impression techniques and materials used to make complete dentures, for retention, stability, comfort, and quality of life in completely edentulous people.To assess the effects of different final-impression techniques and materials used to make removable partial dentures, for stability, comfort, overextension, and quality of life in partially edentulous people. Cochrane Oral Health's Information Specialist searched the following databases: Cochrane Oral Health's Trials Register (to 22 November 2017), the Cochrane Central Register of Controlled Trials (CENTRAL) (Cochrane Register of Studies, to 22 November 2017), MEDLINE Ovid (1946 to 22 November 2017), and Embase Ovid (21 December 2015 to 22 November 2017). The US National Institutes of Health Trials Registry (ClinicalTrials.gov) and the World Health Organization International Clinical Trials Registry Platform were searched for ongoing trials. No restrictions were placed on language or publication status when searching the electronic databases, however the search of Embase was restricted by date due to the Cochrane Centralised Search Project to identify all clinical trials and add them to CENTRAL. We included randomised controlled trials (RCTs) comparing different final-impression techniques and materials for treating people with complete dentures (CD) and removable partial dentures (RPD). For CD, we included trials that compared different materials or different techniques or both. In RPD for tooth-supported conditions, we included trials comparing the

  1. Nanospherical inorganic α-Fe core-organic shell necklaces for the removal of arsenic(V) and chromium(VI) from aqueous solution

    Science.gov (United States)

    Azzam, Ahmed M.; Shenashen, Mohamed A.; Selim, Mahmoud M.; Yamaguchi, Hitoshi; El-Sewify, Islam M.; Kawada, Satoshi; Alhamid, Abdulaziz A.; El-Safty, Sherif A.

    2017-10-01

    Mesoporous nanospherical necklaces (NSN) of inorganic α-Fe core-organic shell and ethylenediaminetetraacetic acid (EDTA) were fabricated. The necklaces were 1 μm in length and 50 nm in thickness, with massive nanospherical particles connecting and overlapping in a neat micro-/nano-necklace archery cage for capturing/trapping of As(V) and Cr(VI) species from water sources. The α-Fe core and the dressing shell of EDTA provided numerous active sites for adsorption, which led to 100% adsorption uptake of these toxic ions. The adsorption isotherms revealed that NSN adsorbent with mesoporous caves and organic-decorated surfaces was promising and effective for the spontaneous and endothermic removal of both ions from contaminated water. The NSN structure exhibited long-term stability. The adsorption efficiency and uptake of the deleterious arsenic and chromium species were achieved after multi-particulate processing of reuse cycles. The pH-dependent removal of As(V) and Cr(VI) species is an emerging topic in selective adsorption assays among competitive ions. Furthermore, the ion-selective conditions at pH 5 for As(V) and pH 7 for Cr(VI) significantly affected the adsorption capacity and affinity of 306.7 and 406.5 mg g-1 into NSN cages, respectively. The obtained results could be used as a basis to provide effective and low-cost products for the purification of wastewater resources from toxic metals.

  2. Evaluation of Team-Based Learning and Traditional Instruction in Teaching Removable Partial Denture Concepts.

    Science.gov (United States)

    Echeto, Luisa F; Sposetti, Venita; Childs, Gail; Aguilar, Maria L; Behar-Horenstein, Linda S; Rueda, Luis; Nimmo, Arthur

    2015-09-01

    The aim of this study was to evaluate the effectiveness of team-based learning (TBL) methodology on dental students' retention of knowledge regarding removable partial denture (RPD) treatment. The process of learning RPD treatment requires that students first acquire foundational knowledge and then use critical thinking skills to apply that knowledge to a variety of clinical situations. The traditional approach to teaching, characterized by a reliance on lectures, is not the most effective method for learning clinical applications. To address the limitations of that approach, the teaching methodology of the RPD preclinical course at the University of Florida was changed to TBL, which has been shown to motivate student learning and improve clinical performance. A written examination was constructed to compare the impact of TBL with that of traditional teaching regarding students' retention of knowledge and their ability to evaluate, diagnose, and treatment plan a partially edentulous patient with an RPD prosthesis. Students taught using traditional and TBL methods took the same examination. The response rate (those who completed the examination) for the class of 2013 (traditional method) was 94% (79 students of 84); for the class of 2014 (TBL method), it was 95% (78 students of 82). The results showed that students who learned RPD with TBL scored higher on the examination than those who learned RPD with traditional methods. Compared to the students taught with the traditional method, the TBL students' proportion of passing grades was statistically significantly higher (p=0.002), and 23.7% more TBL students passed the examination. The mean score for the TBL class (0.758) compared to the conventional class (0.700) was statistically significant with a large effect size, also demonstrating the practical significance of the findings. The results of the study suggest that TBL methodology is a promising approach to teaching RPD with successful outcomes.

  3. Maximum dislodging forces of mandibular implant-assisted removable partial dentures: in vitro assessment.

    Science.gov (United States)

    Gharehchahi, Jafar; Asadzadeh, Nafiseh; Mirmortazavi, Amirtaher; Shakeri, Mohammad Taghi

    2013-10-01

    The initial retention of implant-assisted removable partial dentures (IARPDs) is unknown. The purpose of this in vitro study was to compare maximum dislodging forces of distal extension mandibular IARPD with two different attachments and three clasp designs. A simulated class I partially edentulous mandible was prepared with two screw-type 3.75 × 12 mm implants in the first molar regions and 2 metal-ceramic crowns on distal abutments. Fifteen bilateral distal extension frameworks were conventionally fabricated in three clasp designs (suprabulge, infrabulge, no clasp). Locator attachments were connected to the 15 denture bases with autopolymerized resin. Each specimen was subject to four types of retention pulls (main, anterior, posterior, unilateral pull) five times with a universal testing machine. Locator attachments were replaced with O-ring attachments, and the same procedure was performed. Therefore, the study groups included: IRPD with Locator attachment and suprabulge clasp (group 1), IRPD with Locator attachment and infrabulge clasp (group 2), IRPD with Locator attachment and no clasp (group 3), IRPD with O-ring attachment and suprabulge clasp (group 4), IRPD with O-ring attachment and infrabulge clasp (group 5), IRPD with O-ring attachment and no clasp (group 6). Data were analyzed using one-way ANOVA, two-way ANOVA, and Tukey tests. The highest mean value was 22.99 lb for prostheses with a Locator attachment and suprabulge clasp. The lowest retentive values were recorded for IARPDs with O-ring attachments. The results of this in vitro study suggest that the precise selection of attachments with or without clasp assemblies may affect the clinical success of mandibular IARPDs. © 2013 by the American College of Prosthodontists.

  4. Implant retainers for free-end removable partial dentures affect mastication and nutrient intake.

    Science.gov (United States)

    Campos, Camila Heitor; Gonçalves, Thais Marques Simek Vega; Rodrigues Garcia, Renata Cunha Matheus

    2014-08-01

    This study measured swallowing threshold parameters and nutrient intake in partially dentate subjects rehabilitated by conventional free-end removable partial dentures (RPD) and by RPD over posterior implant retainers and ball attachments (BA). Eight subjects (two men and six women; mean age 60.1 ± 6.6 years old) received conventional total maxillary dentures and free-end RPD in the mandible. Two months after denture insertion, swallowing threshold and nutrient intake assessments occurred, which included an evaluation of the number of masticatory cycles and medium particle size (X₅₀) of a silicone test material (Optocal). A 3-day food diary verified nutrient intake based on a standard Brazilian Food Composition Table. Then, osseointegrated implants were placed bilaterally in the mandibular first molar region, followed by BA, which was fitted in the RPD bases after healing. After 2 months of the RPD over implants and BA use, variables were again assessed. Wilcoxon signed rank tests evaluated the data (P 0.05); however, subjects showed decreased X₅₀ values at the swallowing moment (P = 0.008) and increased daily energy (P = 0.008), carbohydrate (P = 0.016), protein (P = 0.023), calcium (P = 0.008), fiber (P = 0.016), and iron (P = 0.016) intake with RPD implants and BA inserts. No differences were found in fat consumption (P > 0.05). Implants and BA retainers over a free-end RPD resulted in smaller swallowed median particle size and improved nutrient intake. © 2013 John Wiley & Sons A/S. Published by Blackwell Publishing Ltd.

  5. Precision attachment-retained removable partial dentures. Part 3. General practitioner results up to 2 years.

    Science.gov (United States)

    Owall, B; Jönsson, L

    1998-01-01

    The aim of this study was to analyze the techniques, production problems, and 2-year results of attachment-retained removable partial denture (RPD) treatment provided by general practitioners in Sweden. At a major dental laboratory, consecutive cases involving new production of crowns, or of fixed partial dentures (FPDs) and RPDs retained with precision attachments, were studied. Parameters of the dentition, crown or FPD, type and brand of attachment, etc, as well as early satisfaction by dentist and patient, were recorded using specially designed forms at the dental laboratory and questionnaires for the dentists. After 2 years, questionnaires were again sent out to the dentists to record complications and patients' and dentists' opinions of the results. The sample gathered totaled 83 constructions. After 2 years, responses for 57 patients, all of whom had distal-extension RPDs, were received. Most drop-outs in the study were explicable. The most frequently cited reasons for using attachments were esthetics and need for crowning the teeth abutting the RPD. McCollum rigid slide attachment was the predominant brand used (43% of constructions). Dentists and patients were dissatisfied with 6% of the constructions. During the first 2 years, 22 of 57 constructions were complication-free. Seventeen had attachment complications and 9 had serious complications related to the abutment teeth or RPDs. A comparison between these 2 groups revealed that those with complications had every second abutment root-canal treated and a root post, while the group without complications had every fifth abutment root-canal treated. There were many technical and biotechnical complications and failures; the exact ratio, however, depended on the definition of "complications" and "failure." The 2-year results also deviated considerably from the dentists' opinions of the early results.

  6. Implant-supported removable partial dentures in the mandible: A 3-16 year retrospective study.

    Science.gov (United States)

    Jensen, Charlotte; Meijer, Henny J A; Raghoebar, Gerry M; Kerdijk, Wouter; Cune, Marco S

    2017-04-01

    The purpose of this retrospective study was to assess performance, together with biological and technical complications, of implant-supported removable partial dentures (ISRPD) in mandibular Kennedy class I situations with implants placed in the anterior or posterior position. 23 subjects with two endosseous implants to support a bilateral-free-ending mandibular removable denture were examined. Eight subjects had implants in the premolar (anterior) region and 15 subjects implants in the molar (posterior) region. Biological and technical complications were recorded from the patients' medical record. Patients filled out a validated questionnaire regarding their appreciation of oral health related quality of life (OHIP-NL49) and a VAS score on overall satisfaction. Over a mean follow-up period of 8 years (median 8 years, range 3-16 years) the cumulative implant survival rate was 91.7% (SE 0.05). Mean peri-implant bone loss was 0.9mm (SD 1.0mm). Scores for bleeding on probing, plaque and mucosal health were generally low, but significantly worse for posteriorly placed implants. Significantly more biological complications occurred in the posterior group (X 2 (1)=3.9; p=0.048). In 65% of the cases no technical complications were registered. Mean overall OHIP score was 16.1 (SD 18.4) and patients were highly satisfied (VAS: 8.4; SD 2.1). Within the limitations of this retrospective study, in case of a Kennedy class I situation in the mandible, an ISRPD is a viable treatment option with a high implant survival rate and satisfied patients after a maximum of 16 years. Technical and biological complications should be anticipated. Anteriorly placed implants performed slightly better. Copyright © 2016 Japan Prosthodontic Society. Published by Elsevier Ltd. All rights reserved.

  7. Microbiological analysis after complete or partial removal of carious dentin using two different techniques in primary teeth: A randomized clinical trial

    Directory of Open Access Journals (Sweden)

    Deepak Kumar Singhal

    2016-01-01

    Conclusion: Results suggest the use of partial caries removal in a single session as compared to complete caries removal as a part of treatment of deep lesions in deciduous teeth in order to reduce the risk of pulp exposure. Partial caries removal using ART can be preferred for community settings as public health procedure for caries management.

  8. A retrospective case series of implants used to restore partially edentulous patients with implant-supported removable partial dentures: 31-month mean follow-up results.

    Science.gov (United States)

    Grossmann, Yoav; Levin, Liran; Sadan, Avishai

    2008-09-01

    The incorporation of dental implants into removable partial dentures is a common clinical practice, but it is poorly documented in the dental literature. The purpose of this retrospective case series study was to evaluate the survival of endosseous dental implants used in restoring partially edentulous patients with implant-supported removable partial dentures (ISRPDs) of different configurations, based on up to 10 years of follow-up. The sample consisted of 23 consecutively treated partially edentulous patients, who, between 1996 and 2005, had a total of 44 implants placed in different arch sites and who were treated with ISRPDs. The mean age was 44.2 +/- 7.5 years at inclusion. Mean follow-up time from implant placement was 31.5 months (range, 9 to 120 months). Smoking status, arch configuration before and after implant placement, follow-up time from implant placement, implant location, implant dimensions, implant and abutment survival, and overall satisfaction (assessed by questionnaire) with the restoration are presented. The overall implant survival rate was 95.5%; 2 implants failed. Kennedy Class I in the maxilla (6 patients) followed by Kennedy Class II in the mandible (4 patients) were the most prevalent arch configurations before implant placement. Arch configuration was modified by implant placement in 6 patients (26.1%). During follow-up, 1 abutment tooth was lost 2 years after prosthesis delivery. All patients were satisfied with their prosthesis. Implant-supported removable partial dentures could serve as a long-term predictable treatment modality. Careful patient selection, with an appropriate maintenance and recall system, is recommended to obtain satisfactory results.

  9. Characterization of Penicillium oxalicum SL2 isolated from indoor air and its application to the removal of hexavalent chromium.

    Science.gov (United States)

    Long, Bibo; Ye, Binhui; Liu, Qinglin; Zhang, Shu; Ye, Jien; Zou, Lina; Shi, Jiyan

    2018-01-01

    Removal of toxic Cr(VI) by microbial reduction is a promising approach to reducing its ecotoxicological impact. To develop bioremediation technologies, many studies have evaluated the application of microorganisms isolated from Cr(VI)-contaminated sites. Nonetheless, little attention has been given to microbes from the environments without a history of Cr(VI) contamination. In this study, we aimed to characterize the Cr(VI) tolerance and removal abilities of a filamentous fungus strain, SL2, isolated from indoor air. Based on phenotypic characterization and rDNA sequence analysis, SL2 was identified as Penicillium oxalicum, a species that has not been extensively studied regarding Cr(VI) tolerance and reduction abilities. SL2 showed high tolerance to Cr(VI) on solid and in liquid media, facilitating its application to Cr(VI)-contaminated environments. Growth curves of SL2 in the presence of 0, 100, 400, or 1000 mg/L Cr(VI) were well simulated by the modified Gompertz model. The relative maximal colony diameter and maximal growth rate decreased as Cr(VI) concentration increased, while the lag time increased. SL2 manifested remarkable efficacy of removing Cr(VI). Mass balance analysis indicated that SL2 removed Cr(VI) by reduction, and incorporated 0.79 mg of Cr per gram of dry biomass. In electroplating wastewater, the initial rate of Cr(VI) removal was affected by the initial contaminant concentration. In conclusion, P. oxalicum SL2 represents a promising new candidate for Cr(VI) removal. Our results significantly expand the knowledge on potential application of this microorganism.

  10. Study of the removal of mercury(II) and chromium(VI) from aqueous solutions by Moroccan stevensite

    Energy Technology Data Exchange (ETDEWEB)

    Benhammou, A. [Ecole Superieure de Technologie, Route Dar Si Aissa, BP: 89 Safi (Morocco)]. E-mail: benhammou_ab@yahoo.fr; Yaacoubi, A. [Faculte des Sciences Semlalia, Avenue My Abdellah, BP: 2390 Marrakech (Morocco); Nibou, L. [Ecole Superieure de Technologie, Route Dar Si Aissa, BP: 89 Safi (Morocco); Tanouti, B. [Faculte des Sciences Semlalia, Avenue My Abdellah, BP: 2390 Marrakech (Morocco)

    2005-01-31

    The objective of the present study was to investigate the adsorption of the heavy metals mercury(II) and chromium(VI), from aqueous solutions, onto Moroccan stevensite. A mineralogical and physicochemical characterization of natural stevensite was carried out. In order to improve the adsorption capacity of stevensite for Cr(VI), a preparation of stevensite was carried out. It consists in saturating the stevensite by ferrous iron Fe(II) and reducing the total Fe by Na{sub 2}S{sub 2}O{sub 4}. Then, the adsorption experiments were studied in batch reactors at 25 {+-} 3 deg. C. The influence of the pH solution on the Cr(VI) and Hg(II) adsorption was studied in the pH range of 1.5-7.0. The optimum pH for the Cr(VI) adsorption is in the pH range of 2.0-5.0 while that of Hg(II) is at the pH values above 4.0. The adsorption kinetics were tested by a pseudo-second-order model. The adsorption rate of Hg(II) is 54.35 mmol kg{sup -1} min{sup -1} and that of Cr(VI) is 7.21 mmol kg{sup -1} min{sup -1}. The adsorption equilibrium time for Hg(II) and Cr(VI) was reached within 2 and 12 h, respectively. The adsorption isotherms were described by the Dubinin-Radushkevich model. The maximal adsorption capacity for Cr(VI) increases from 13.7 (raw stevensite) to 48.86 mmol kg{sup -1} (modified stevensite) while that of Hg(II) decreases from 205.8 to 166.9 mmol kg{sup -1}. The mechanism of Hg(II) and Cr(VI) adsorption was discussed.

  11. Study of the removal of mercury(II) and chromium(VI) from aqueous solutions by Moroccan stevensite.

    Science.gov (United States)

    Benhammou, A; Yaacoubi, A; Nibou, L; Tanouti, B

    2005-01-31

    The objective of the present study was to investigate the adsorption of the heavy metals mercury(II) and chromium(VI), from aqueous solutions, onto Moroccan stevensite. A mineralogical and physicochemical characterization of natural stevensite was carried out. In order to improve the adsorption capacity of stevensite for Cr(VI), a preparation of stevensite was carried out. It consists in saturating the stevensite by ferrous iron Fe(II) and reducing the total Fe by Na(2)S(2)O(4). Then, the adsorption experiments were studied in batch reactors at 25+/-3 degrees C. The influence of the pH solution on the Cr(VI) and Hg(II) adsorption was studied in the pH range of 1.5-7.0. The optimum pH for the Cr(VI) adsorption is in the pH range of 2.0-5.0 while that of Hg(II) is at the pH values above 4.0. The adsorption kinetics were tested by a pseudo-second-order model. The adsorption rate of Hg(II) is 54.35 mmol kg(-1)min(-1) and that of Cr(VI) is 7.21 mmol kg(-1)min(-1). The adsorption equilibrium time for Hg(II) and Cr(VI) was reached within 2 and 12 h, respectively. The adsorption isotherms were described by the Dubinin-Radushkevich model. The maximal adsorption capacity for Cr(VI) increases from 13.7 (raw stevensite) to 48.86 mmol kg(-1) (modified stevensite) while that of Hg(II) decreases from 205.8 to 166.9 mmol kg(-1). The mechanism of Hg(II) and Cr(VI) adsorption was discussed.

  12. Study of the removal of mercury(II) and chromium(VI) from aqueous solutions by Moroccan stevensite

    International Nuclear Information System (INIS)

    Benhammou, A.; Yaacoubi, A.; Nibou, L.; Tanouti, B.

    2005-01-01

    The objective of the present study was to investigate the adsorption of the heavy metals mercury(II) and chromium(VI), from aqueous solutions, onto Moroccan stevensite. A mineralogical and physicochemical characterization of natural stevensite was carried out. In order to improve the adsorption capacity of stevensite for Cr(VI), a preparation of stevensite was carried out. It consists in saturating the stevensite by ferrous iron Fe(II) and reducing the total Fe by Na 2 S 2 O 4 . Then, the adsorption experiments were studied in batch reactors at 25 ± 3 deg. C. The influence of the pH solution on the Cr(VI) and Hg(II) adsorption was studied in the pH range of 1.5-7.0. The optimum pH for the Cr(VI) adsorption is in the pH range of 2.0-5.0 while that of Hg(II) is at the pH values above 4.0. The adsorption kinetics were tested by a pseudo-second-order model. The adsorption rate of Hg(II) is 54.35 mmol kg -1 min -1 and that of Cr(VI) is 7.21 mmol kg -1 min -1 . The adsorption equilibrium time for Hg(II) and Cr(VI) was reached within 2 and 12 h, respectively. The adsorption isotherms were described by the Dubinin-Radushkevich model. The maximal adsorption capacity for Cr(VI) increases from 13.7 (raw stevensite) to 48.86 mmol kg -1 (modified stevensite) while that of Hg(II) decreases from 205.8 to 166.9 mmol kg -1 . The mechanism of Hg(II) and Cr(VI) adsorption was discussed

  13. Clinical effect of photodynamic therapy on primary carious dentin after partial caries removal

    Directory of Open Access Journals (Sweden)

    Pierre Adriano Moreno NEVES

    2016-01-01

    Full Text Available Abstract This study was conducted to assess the clinical effect of photodynamic therapy (PDT in the decontamination of the deep dentin of deciduous molars submitted to partial removal of carious tissue. After cavity preparation, dentin samples were taken from the pulp wall of nineteen deciduous molars before and after PDT application. Remaining dentin was treated with 0.01% methylene blue dye followed by irradiation with an InGaAlP diode laser (λ – 660 nm; 40 mW; 120 J/cm2; 120 s. Dentin samples were microbiologically assessed for the enumeration of total microorganisms, Lactobacillus spp. and mutans streptococci. There was no significant difference in the number of colony-forming units (CFU for any of the microorganisms assessed (p > 0.05. Photodynamic therapy, using 0.01% methylene blue dye at a dosimetry of 120 J/cm2 would not be a viable clinical alternative to reduce bacterial contamination in deep dentin.

  14. Clinical Fit of Partial Removable Dental Prostheses Based on Alginate or Polyvinyl Siloxane Impressions.

    Science.gov (United States)

    Fokkinga, Wietske A; Witter, Dick J; Bronkhorst, Ewald M; Creugers, Nico H

    The aim of this study was to analyze the clinical fit of metal-frame partial removable dental prostheses (PRDPs) based on custom trays used with alginate or polyvinyl siloxane impression material. Fifth-year students of the Nijmegen Dental School made 25 correct impressions for 23 PRDPs for 21 patients using alginate, and 31 correct impressions for 30 PRDPs for 28 patients using polyvinyl siloxane. Clinical fit of the framework as a whole and of each retainer separately were evaluated by calibrated supervisors during framework try-in before (first evaluation) and after (second evaluation) possible adjustments (score 0 = poor fit, up to score 3 = good fit). Framework fit and fit of the denture base were evaluated at delivery (third evaluation). Finally, postinsertion sessions were evaluated and total number of sessions needed, sore spots, adjustments to the denture base, and reported food-impaction were recorded. No significant differences in clinical fit (of the framework as a whole, for the retainers, or for the denture base) were found between the groups in the three evaluation sessions. Differences were not found for postinsertion sessions with one exception: in the alginate group, four subjects reported food impaction, versus none in the polyvinyl siloxane group. Clinical fit of metal-frame PRDPs based on impressions with custom trays combined with alginate or polyvinyl siloxane was similar.

  15. Patient’s Satisfaction with Removable Partial Dentures: A Retrospective Case Series

    Science.gov (United States)

    Shala, Kujtim Sh.; Dula, Linda J.; Pustina-Krasniqi, Teuta; Bicaj, Teuta; Ahmedi, Enis F.; Lila-Krasniqi, Zana; Tmava-Dragusha, Arlinda

    2016-01-01

    This retrospective clinical study aimed to assess patient’s satisfaction with removable partial dentures (RPDs), as retention, chewing ability, aesthetics during the observation period. Material and Methods: A total of 63 patients with RPDs, participated in this study. The following data was collected: Kennedy classification, denture design, denture support, satisfaction and success of RPD. Result: The results showed that 73.6% of patients were wearing RPD for the first time and were finally satisfied. According to the denture support of RPDs, clasp-retained quadrangular RPDs were 100% effective, followed by triangular dental support 81% and linear dental support 47.7%. Comparison of RPDs with attachment with RPDs with claps assessed through Fisher exact test, confirmed statistically significant difference (P=0.008), despite retention; however, chewing ability and aesthetics showed no statistically significant difference with X 2 test on patient’s satisfaction with RPD with or without attachment. Conclusion: Patients often would prefer not showing the anterior buccal clasps of RPD, therefore are generally satisfied more with RPD with attachment based on level of retention, chewing ability and aesthetics. PMID:28077970

  16. Prevalence of removable partial dentures users treated at the Aracatuba Dental School-UNESP.

    Science.gov (United States)

    Pellizzer, Eduardo P; Almeida, Daniel Augusto de Faria; Falcón-Antenucci, Rosse M; Sánchez, Daniela Mayumi I K; Zuim, Paulo Renato J; Verri, Fellippo R

    2012-06-01

    The aim of this study was to evaluate the frequency of removable partial dentures (RPD) at the Aracatuba Dental School. The study was conducted by analysing 412 clinical history of patients attended at the RPD clinics in the period from 2000 to 2007. 412 charts were analysed: 148 (35.9%) men and 264 (64.1%) women. The mean age was 53.8 years (men) and 52.4 years (women). A total of 556 dentures were made; of these, 233 (41.90%) were maxillary and 323 (58.09%) were mandibular dentures. The most frequent Kennedy classification found was Class III (maxilla) and Class I (mandible). In the maxilla, 55% (126) of the major connectors were of the anterior-posterior palatal bar, while in the mandible, 64% (202) were the lingual bar. As regards the claps, 401 were circumferential and 318 were bar claps. The mean age of the patients was 52.9 years with higher prevalence of female patients; the most frequent Kennedy's classification was Class I in mandible and Class III in maxilla; the most common major connector was anterior-posterior palatal bar for maxilla and lingual bar for mandible; the circumferential clasps were the most common retainer used in both jaws. © 2012 The Gerodontology Society and John Wiley & Sons A/S.

  17. Impact of periodontal maintenance on tooth survival in patients with removable partial dentures.

    Science.gov (United States)

    Tada, Sayaka; Allen, Patrick Finbarr; Ikebe, Kazunori; Matsuda, Ken-ichi; Maeda, Yoshinobu

    2015-01-01

    Removable partial dentures (RPDs) may have a negative impact on oral health and have the potential to cause further tooth loss, especially of abutment teeth. However, no evidence indicates the effective interval of regular periodontal maintenance after RPD provision. This practice-based cohort study aimed to examine the impact of regular periodontal maintenance visits on survival of RPD abutment teeth. One hundred and ninety-two patients had been previously provided with 304 new clasp-retained RPDs at Osaka University Dental Hospital, Japan. Using the Kaplan-Meier method and log-rank test, 1094 abutments were analysed to illustrate survival curves and to compare each curve. According to the frequency of periodontal maintenance, study samples were divided into three groups; every 3-6 months (3-6M) group, 1-year (1Y) group and no-maintenance (NM) group. Seven-year cumulative survival rates were 83.7% (3-6M), 75.5% (1Y) and 71.9% (NM) respectively. Survival of abutment teeth in the 3-6M group was significantly better than both 1Y (p = 0.005) and NM (p < 0.001) groups. These longitudinal clinical data indicates that periodontal maintenance at least once in 6 months had the most favourable outcome. Frequent periodontal maintenance after RPD provision could be effective in preventing further tooth loss. © 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  18. Muscle activity and masticatory efficiency with bilateral extension base removable partial dentures with different cusp angles.

    Science.gov (United States)

    Al-Omiri, Mahmoud K

    2018-03-01

    Whether masticatory efficiency and electromyographic activity are influenced by type of artificial teeth and food is unclear. The purpose of this clinical study was to evaluate the influence of extension base removable partial dentures (RPDs) with different cusp angles: anatomic (33 degrees), semianatomic (20 degrees), and nonanatomic (0 degrees) teeth on masticatory efficiency and muscle activity during the mastication of test foods with different textures. Twelve participants with RPDs were selected to perform masticatory efficiency and electromyographic tests. Surface electromyograms (EMGs) were used to record the activities of the masseter and temporalis muscles during the mastication of different types of test foods. The maximal voltage and duration were measured on the integrated EMG signal in each muscle during food mastication, and the mean reading of both sides was then recorded. Analysis of variance and the Tukey post hoc test were used to perform statistical analyses (α=.05). The masticatory efficiency of RPDs with nonanatomic teeth was significantly inferior to that of RPDs with anatomic and semianatomic teeth (P.05). Also, muscle activity (according to EMG) with RPDs with NA teeth was significantly higher than that with anatomic and semianatomic teeth (P<.05). RPDs with NA teeth were associated with higher EMG muscle activity and reduced masticatory efficiency than anatomic or semianatomic teeth. Copyright © 2017 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

  19. Biological response to self-etch adhesive after partial caries removal in rats.

    Science.gov (United States)

    Da Silva, Adriana Fernandes; Marques, Marcelo Rocha; Da Rosa, Wellington Luiz De Oliveira; Tarquinio, Sandra Beatriz Chaves; Rosalen, Pedro Luiz; Barros, Silvana Pereira

    2018-01-29

    The purposes of this study were to evaluate a model of slow caries progression and to investigate the performance of a self-etch adhesive system for partial caries removal. Rat molars were infected with Streptococcus sobrinus 6715 culture. Different time points were analyzed: days 78, 85, and 95 (± 2). After this, the samples were processed for morphological analysis. Additionally, the first molars were restored with zinc oxide and eugenol (IRM™; Dentsply; Brazil) or adhesive system (Clearfil SE Bond™; Kuraray Medical; Japan) 78 days after caries induction. After, 3 or 15 days post-treatment, the animals were euthanized, and their mandibles were processed for morphological analysis, classified by means of scores, and submitted to statistical analysis. Subsequently, immunohistochemical analysis was performed for osteonectin (OSN) and transforming growth factor-ß1 (TGF-ß1) expression. According to the caries induction model used, on day 95 greater inflammatory infiltration (p  0.05) and proved to be fundamental to control the carious lesion. The TGF-ß1 and OSN were shown to be active during the caries process. The slow caries lesion model was feasible for morphological analysis of the dentin-pulp complex. The self-etch adhesive system triggered no acute inflammatory infiltration or pulp necrosis, instead it seemed to stimulate early pulp repair. Clearfil SE Bond™ applied directly on caries-affected dentin did not predispose to pulp inflammation; instead, it appeared to provide early biological benefits.

  20. Use of RSM modeling for optimizing decolorization of simulated textile wastewater by Pseudomonas aeruginosa strain ZM130 capable of simultaneous removal of reactive dyes and hexavalent chromium.

    Science.gov (United States)

    Maqbool, Zahid; Hussain, Sabir; Ahmad, Tanvir; Nadeem, Habibullah; Imran, Muhammad; Khalid, Azeem; Abid, Muhammad; Martin-Laurent, Fabrice

    2016-06-01

    Remediation of colored wastewater loaded with dyes and metal ions is a matter of interest nowadays. In this study, 220 bacteria isolated from textile wastewater were tested for their potential to decolorize each of the four reactive dyes (reactive red-120, reactive black-5, reactive yellow-2, and reactive orange-16) in the presence of a mixture of four different heavy metals (Cr, Zn, Pb, Cd) commonly found in textile effluents. Among the tested bacteria, the isolate ZM130 was found to be the most efficient in decolorizing reactive dyes in the presence of the mixture of heavy metals and was identified as Pseudomonas aeruginosa strain ZM130 by 16S rRNA gene analysis. The strain ZM130 was highly effective in simultaneously removing hexavalent chromium (25 mg L(-1)) and the azo dyes (100 mg L(-1)) from the simulated wastewater even in the presence of other three heavy metals (Zn, Pb, Cd). Simultaneous removal of chromium and azo dyes ranged as 76.6-98.7 % and 51.9-91.1 %, respectively, after 180 h incubation. On the basis of quadratic polynomial equation and response surfaces given by the response surface methodology (RSM), optimal salt content, pH, carbon co-substrate content, and level of multi-metal mixtures for decolorization of reactive red-120 in a simulated textile wastewater by the strain ZM130 were predicted to be 19.8, 7.8, and 6.33 g L(-1) and a multi-metal mixture (Cr 13.10 mg L(-1), Pb 26.21 mg L(-1), Cd 13.10 mg L(-1), Zn 26.21 mg L(-1)), respectively. Moreover, the strain ZM130 also exhibited laccase and nicotinamide adenine dinucleotide (reduced)-dichlorophenolindophenol reductase (NADH-DCIP reductase) activity during the decolorization of reactive red-120. However, the laccase activity was found to be maximum in the presence of 300 mg L(-1) of the dye as compared to other concentrations. Hence, the isolation of this strain might serve as a potential bio-resource required for developing the strategies aiming at bioremediation of the

  1. Fe(0)-Fe3O4 nanocomposites embedded polyvinyl alcohol/sodium alginate beads for chromium (VI) removal.

    Science.gov (United States)

    Lv, Xiaoshu; Jiang, Guangming; Xue, Xiaoqin; Wu, Donglei; Sheng, Tiantian; Sun, Chen; Xu, Xinhua

    2013-11-15

    In this study, Fe(0)-Fe3O4 nanocomposites embedded polyvinyl alcohol (PVA)/sodium alginate (SA) beads were synthesized, which exhibited an excellent physical properties and catalytic reactivity, and a robust performance of post-separation (complete separation using a simple grille) and reusability (efficiency of 69.8% after four runs) in Cr(VI) removal. 5.0 wt% PVA with 1.5 wt% SA was the optimal proportion for beads molding, and the followed acidification and reduction treatments were critical to ensure high mechanical strength and high Cr(VI) removal ability of beads. Effects of Fe(0) and Fe3O4 mass fraction, initial pH and Cr(VI) concentration on final removal efficiency were also evaluated. Merely 0.075 wt% Fe(0) together with 0.30 wt% Fe3O4 was sufficient to deal with 20 mg L(-1) Cr(VI) solution. The efficiency decreased from 100 to 79.5% as initial Cr(VI) increased from 5 to 40 mg L(-1), while from 99.3 to 76.3% with increasing pH from 3.0 to 11.0. This work provides a practical and high-efficient method for heavy metal removal from water body, and simultaneously solves the problems in stabilization, separation and regeneration of Fe(0) nanoparticles. Copyright © 2013 Elsevier B.V. All rights reserved.

  2. Implant-supported mandibular removable partial dentures : Functional, clinical and radiographical parameters in relation to implant position

    NARCIS (Netherlands)

    Jensen, Charlotte; Speksnijder, Caroline M.; Raghoebar, Gerry M.; Kerdijk, Wouter; Meijer, Henny J. A.; Cune, Marco S.

    Background: Patients with a Kennedy class I situation often encounter problems with their removable partial denture (RPD). Purpose: To assess the functional benefits of implant support to RPDs, the clinical performance of the implants and teeth and to determine the most favorable implant position:

  3. Implant-supported mandibular removable partial dentures; patient-based outcome measures in relation to implant position

    NARCIS (Netherlands)

    Jensen, Charlotte; Raghoebar, Gerry M.; Kerdijk, Wouter; Meijer, Henny J. A.; Cune, Marco S.

    2016-01-01

    Objectives: To assess the benefits of implant support to Removable Partial Dentures (RPD) in patients with a bilateral free-ending situation in the mandible and to determine the most favorable implant position: the premolar (PM) or the molar (M) region. Methods: Thirty subjects with a bilateral

  4. [A phd completed 10. Implant-supported removable partial -dentures in a Kennedy Class I-situation in the mandible].

    Science.gov (United States)

    Jensen-Louwerse, C

    2017-06-01

    Implant-supported removable partial dentures in the mandible often cause problems, which means that patients wear their dentures seldom if at all. A solution is to place implants that the dentures can be snapped onto. There is, however, no consensus about the best position of the implants in the mandible yet. In addition, it is worthwhile to balance the cost of treatment with its effectiveness. In a randomised cross-over clinical trial involving 30 patients with a shortened dental arch, the implant-supported removable partial denture in the mandible was evaluated based on the experience of the patient, mean time of wearing, chewing ability and the clinical and radiographic parameters in relation to 2 different implant positions: 2 in the pre-molar region or 2 in the molar region. The cost-effectiveness of both treatments was also evaluated. From the patient's point of view, the implant-supported removable partial dentures are best supported by implants placed in the molar region. The research also revealed, however, that significantly more bleeding occurred around implants placed in the molar region and from a clinical perspective placement in the pre-molar region would have preference. The cost-effectiveness of the treatment with an implant-supported removable partial denture depends on the choice of outcome measurement and monetary threshold.

  5. A Clinical Retrospective Study of Distal Extension Removable Partial Denture with Implant Surveyed Bridge or Stud Type Attachment

    Science.gov (United States)

    Bae, Eun-Bin; Kim, Seong-Jong; Choi, Jae-Won; Jeon, Young-Chan; Jeong, Chang-Mo; Yun, Mi-Jung; Lee, So-Hyoun

    2017-01-01

    This study was performed to make comparative analysis of the clinical findings between the two different types of the implant-assisted removable partial dentures: removable partial dentures using implant surveyed bridge as an abutment (ISBRPD) and overdenture type of removable partial denture using implant attachment (IARPD). Implant cumulative survival rate, marginal bone resorption, probing depth, peri-implant inflammation, bleeding, plaque, calculus, and complications were evaluated on 24 patients who were treated with implants in conjunction with removable partial denture and have used them for at least 1 year (ISCRPD: n = 12; IARPD: n = 12). There was no failed implant and all implants were functioning without clinical mobility. Marginal bone loss of ISCRPD (1.44 ± 0.57 mm) was significantly lower than that of IARPD (p 0.05), while the calculus was significantly more observed in ISCRPD group than in IARPD group (p < 0.05). The retention loss of IARPD was the most common complication. Within the limits of the present study, it was found that well-planned ISBRPD was clinically appropriate. Longitudinal and systematic clinical studies are necessary to confirm these results. PMID:28497062

  6. Theoretical role of adjunctive implant positional support in stress distribution of distal-extension mandibular removable partial dentures.

    Science.gov (United States)

    Xiao, Wei; Li, Zhiyong; Shen, Shiqian; Chen, Shaowu; Wang, Yining; Wang, Jiawei

    2014-01-01

    This preliminary study evaluated the adjunctive supporting role of diverse implant positions on stress distribution in a Class I removable partial denture (RPD) design. Nine three-dimensional finite element models were prepared to simulate mandibular RPD designs with three different loading conditions applied. Implant supported designs demonstrated lower stress value concentrations and mucosal displacement.

  7. A Clinical Retrospective Study of Distal Extension Removable Partial Denture with Implant Surveyed Bridge or Stud Type Attachment

    Directory of Open Access Journals (Sweden)

    Eun-Bin Bae

    2017-01-01

    Full Text Available This study was performed to make comparative analysis of the clinical findings between the two different types of the implant-assisted removable partial dentures: removable partial dentures using implant surveyed bridge as an abutment (ISBRPD and overdenture type of removable partial denture using implant attachment (IARPD. Implant cumulative survival rate, marginal bone resorption, probing depth, peri-implant inflammation, bleeding, plaque, calculus, and complications were evaluated on 24 patients who were treated with implants in conjunction with removable partial denture and have used them for at least 1 year (ISCRPD: n=12; IARPD: n=12. There was no failed implant and all implants were functioning without clinical mobility. Marginal bone loss of ISCRPD (1.44 ± 0.57 mm was significantly lower than that of IARPD (p0.05, while the calculus was significantly more observed in ISCRPD group than in IARPD group (p<0.05. The retention loss of IARPD was the most common complication. Within the limits of the present study, it was found that well-planned ISBRPD was clinically appropriate. Longitudinal and systematic clinical studies are necessary to confirm these results.

  8. A Clinical Retrospective Study of Distal Extension Removable Partial Denture with Implant Surveyed Bridge or Stud Type Attachment.

    Science.gov (United States)

    Bae, Eun-Bin; Kim, Seong-Jong; Choi, Jae-Won; Jeon, Young-Chan; Jeong, Chang-Mo; Yun, Mi-Jung; Lee, So-Hyoun; Huh, Jung-Bo

    2017-01-01

    This study was performed to make comparative analysis of the clinical findings between the two different types of the implant-assisted removable partial dentures: removable partial dentures using implant surveyed bridge as an abutment (ISBRPD) and overdenture type of removable partial denture using implant attachment (IARPD). Implant cumulative survival rate, marginal bone resorption, probing depth, peri-implant inflammation, bleeding, plaque, calculus, and complications were evaluated on 24 patients who were treated with implants in conjunction with removable partial denture and have used them for at least 1 year (ISCRPD: n = 12; IARPD: n = 12). There was no failed implant and all implants were functioning without clinical mobility. Marginal bone loss of ISCRPD (1.44 ± 0.57 mm) was significantly lower than that of IARPD ( p implant inflammation, bleeding, and plaque between the two groups ( p > 0.05), while the calculus was significantly more observed in ISCRPD group than in IARPD group ( p < 0.05). The retention loss of IARPD was the most common complication. Within the limits of the present study, it was found that well-planned ISBRPD was clinically appropriate. Longitudinal and systematic clinical studies are necessary to confirm these results.

  9. A Comparison of Oak Regeneration Conditions Following Midstory Injection and Partial Overstory Removal in a Tombigbee River Terrace

    Science.gov (United States)

    Stephen E. Peairs; Andrew W. Ezell; Keith L. Belli; John D. Hodges

    2004-01-01

    Bottomland hardwood stands comprised of a large oak component can be regenerated through natural oak regeneration. To maximize oak regeneration potential, the stand manager must practice silvicultural techniques that allow for necessary sunlight penetration to reach the forest floor. Control of stems occupying the midstory/understory and partial overstory removal are...

  10. Highly efficient removal of chromium(VI) by Fe/Ni bimetallic nanoparticles in an ultrasound-assisted system.

    Science.gov (United States)

    Zhou, Xiaobin; Jing, Guohua; Lv, Bihong; Zhou, Zuoming; Zhu, Runliang

    2016-10-01

    Highly active Fe/Ni bimetallic nanocomposites were prepared by using the liquid-phase reduction method, and they were proven to be effective for Cr(VI) removal coupled with US irradiation. The US-assisted Fe/Ni bimetallic system could maintain a good performance for Cr(VI) removal at a wide pH range of 3-9. Based on the characterization of the Fe/Ni nanoparticles before and after reaction, the high efficiency of the mixed system could attribute to the synergistic effects of the catalysis of Ni(0) and US cavitation. Ni(0) could facilitate the Cr(VI) reduction through electron transfer and catalytic hydrogenation. Meanwhile, US could fluidize the Fe/Ni nanoparticles to increase the actual reactive surface area and clean off the co-precipitated Fe(III)-Cr(III) hydroxides to maintain the active sites on the surface of the Fe/Ni nanoparticles. Thus, compared with shaking, the US-assisted Fe/Ni system was more efficient on Cr(VI) removal, which achieved 94.7% removal efficiency of Cr(VI) within 10 min. The pseudo-first-order rate constant (kobs) in US-assisted Fe/Ni system (0.5075 min(-1)) was over 5 times higher than that under shaking (0.0972 min(-1)). Moreover, the Fe/Ni nanoparticles still have a good performance under US irradiation after 26 days aging as well as regeneration. Copyright © 2016 Elsevier Ltd. All rights reserved.

  11. Pressure distribution of implant-supported removable partial dentures with stress-breaking attachments.

    Science.gov (United States)

    Kono, Kentaro; Kurihara, Daisuke; Suzuki, Yasunori; Ohkubo, Chikahiro

    2014-04-01

    This in vitro study investigated the pressure distribution of the implant-supported removable partial dentures (RPDs) with the stress-breaking attachments under the occlusal force. The experimental model of bilateral missing premolars and molars was modified from a commercial simulation model. Five pressure sensors were embedded near the bilateral first molars, first premolars, and medio-lingual alveolar crest. Two implants were placed near the second molars, and they were connected to the denture base using the following conditions: complete separation between the denture base and implant with cover screws (CRPD), flexible connection with a stress-breaking ball (SBB) attachment, and rigid connection without stress breaking with healing caps (HC). The pressure at five different areas of the soft tissue and the displacement of the RPDs were simultaneously measured, loading up to 50 N. The coefficient of variation (CV) for each connection was calculated from all data of the pressure at five areas to evaluate the pressure distribution. The pressure on medio-lingual alveolar crest and molars of the HC was less than SBB and CRPD. In contrast, the pressure on premolars of SBB was greater than for the HC and CRPD. The CV of SBB was less than that of HC and CRPD. Denture displacement of HC and SBB was less than for CRPD. Within the in vitro limitations, precise denture settlements and pressure distribution under the denture base could be controlled using an SBB attachment. An SBB attachment might be able to protect the implant from harmful force. Crown Copyright © 2014. Published by Elsevier Ltd. All rights reserved.

  12. Assessment of Periodontal and Hygiene Conditions of Removable Partial Dentures in Individuals With Clefts.

    Science.gov (United States)

    de Almeida, Ana Lúcia Pompéia Fraga; Catalani, Danilo Tomazzini; Garcia de Oliveira, Pedro César; Soares, Simone; Tunes, Fábio Sanches Magalhães; Neppelenbroek, Karin Hermana

    2016-11-01

      To assess hygiene conditions in removable partial dentures (RPDs) and to compare the periodontal status between abutment and nonabutment teeth in clefts patients.   Cross-sectional.   Tertiary referral hospital.   Forty-five patients of both genders, aged 20 to 75 years, who were upper RPD wearers for at least 2 years, with cleft lip, alveolus, and/or palate who attended follow-up appointments between 2010 and 2012.   The clinical periodontal parameters assessed on abutment teeth (experimental group) and nonabutment teeth (control group) were probing depth, clinical attachment level (CAL), plaque index, and gingival index (GI). The RPDs were evaluated under the following parameters: hygiene conditions and type of clasp on abutment. Both groups were analyzed using Mann-Whitney, Kruskal-Wallis, and Dunn's statistical test. Statistical significance was set at P < .05.   One hundred sixty-six abutment teeth and 168 nonabutment teeth were evaluated in 45 patients. A statistically significant difference was found between the groups for the CAL parameter (P = .03). With regard to the prostheses' hygiene conditions through the Tarbet index parameter, of the 186 quadrants evaluated, 143 scored 2 and 3. Ackers' clasps were the most frequent clasps (n = 111). A statistically significant difference was found for the GI parameter (P = .03).   It was possible to conclude, in this cross-sectional study, that in general terms, the use of RPDs did not interfere in the periodontal conditions of abutment teeth; however, most prostheses presented poor hygiene and high quantity of dental plaque.

  13. An ontology-driven, case-based clinical decision support model for removable partial denture design

    Science.gov (United States)

    Chen, Qingxiao; Wu, Ji; Li, Shusen; Lyu, Peijun; Wang, Yong; Li, Miao

    2016-06-01

    We present the initial work toward developing a clinical decision support model for specific design of removable partial dentures (RPDs) in dentistry. We developed an ontological paradigm to represent knowledge of a patient’s oral conditions and denture component parts. During the case-based reasoning process, a cosine similarity algorithm was applied to calculate similarity values between input patients and standard ontology cases. A group of designs from the most similar cases were output as the final results. To evaluate this model, the output designs of RPDs for 104 randomly selected patients were compared with those selected by professionals. An area under the curve of the receiver operating characteristic (AUC-ROC) was created by plotting true-positive rates against the false-positive rate at various threshold settings. The precision at position 5 of the retrieved cases was 0.67 and at the top of the curve it was 0.96, both of which are very high. The mean average of precision (MAP) was 0.61 and the normalized discounted cumulative gain (NDCG) was 0.74 both of which confirmed the efficient performance of our model. All the metrics demonstrated the efficiency of our model. This methodology merits further research development to match clinical applications for designing RPDs. This paper is organized as follows. After the introduction and description of the basis for the paper, the evaluation and results are presented in Section 2. Section 3 provides a discussion of the methodology and results. Section 4 describes the details of the ontology, similarity algorithm, and application.

  14. Cost-effectiveness of implant-supported mandibular removable partial dentures.

    Science.gov (United States)

    Jensen, Charlotte; Ross, Jamila; Feenstra, Talitha L; Raghoebar, Gerry M; Speksnijder, Caroline; Meijer, Henny J A; Cune, Marco S

    2017-05-01

    The aim of this study was to conduct a cost-effectiveness analysis comparing conventional removable partial dentures (RPDs) and implant-supported RPDs (ISRPDs) treatment in patients with an edentulous maxilla and a bilateral free-ending situation in the mandible. Thirty subjects were included. A new RPD was made and implant support was provided 3 months later. Treatment costs (opportunity costs and costs based on tariffs) were calculated. Treatment effect was expressed by means of the Dutch Oral Health Impact Profile questionnaire (OHIP-NL49), a chewing ability test (Mixing Ability Index, MAI) and a short-form health survey measuring perceived general health (SF-36), which was subsequently converted into quality-adjusted-life-years (QALYs). The incremental cost-effectiveness ratio (ICER) was the primary outcome measure of cost-effectiveness, comparing both treatment strategies. The mean total opportunity costs were €981 (95% CI €971-€991) for the RPD treatment and €2.480 (95% CI €2.461-€2.500) for the ISRPD treatment. The total costs derived from the national tariff structure were €850 for the RPD treatment and €2.610 for the ISRPD treatment. The ICER for OHIP-NL49 and MAI using the opportunity costs was €80 and €786, respectively. When using the tariff structure, corresponding ICERs were €94 and €921. The effect of supporting an RPD with implants when expressed in QALYs was negligible; hence an ICER was not determined. It is concluded that depending on the choice of outcome measure and monetary threshold, supporting an RPD with implants is cost-effective when payers are willing to pay more than €80 per OHIP point gained. Per MAI point gained, an additional €786 has to be invested. © 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  15. Remediation of soils contaminated with chromium using citric and hydrochloric acids: the role of chromium fractionation in chromium leaching.

    Science.gov (United States)

    Cheng, Shu-Fen; Huang, Chin-Yuan; Tu, Yao-Ting

    2011-01-01

    Acid washing is a common method for soil remediation, but is not always efficient for chromium-contaminated soil. Both soil particle size and the forms of chromium existing in the soil affect the efficiency of soil washing. Laboratory batch and column dissolution experiments were conducted to determine the efficiencies of citric and hydrochloric acids as agents to extract chromium from soils contaminated with chromium. The effects of soil particle size and chromium fractionation on Cr leaching were also investigated. About 90% of chromium in the studied soil existed either in residual form or bound to iron and manganese oxides, and Cr fraction distributions were similar for all soil particle sizes. Almost all exchangeable and carbonate-bound chromium was removed by washing once with 0.5 M HCl, whereas organic chromium was more effectively removed by washing with citric acid rather than with HCl solution of the same concentration. For chromium fractions that were either bound to Fe-Mn oxides or existed as residual forms, the efficiencies of acid washing were usually 20% or less, except for 0.5 M HCl solution, which had much higher efficiencies. Separation of the soil sample by particle size before the separate washing of the soil fractions had little improvement on the chromium removal.

  16. Biosynthesized iron nanoparticles in aqueous extracts of Eichhornia crassipes and its mechanism in the hexavalent chromium removal

    Science.gov (United States)

    Wei, Yufen; Fang, Zhanqiang; Zheng, Liuchun; Tsang, Eric Pokeung

    2017-03-01

    Eichhornia crassipes (water hyacinth), a species of invasive weeds has caused serious ecological damage due to its extraordinary fertility and growth rate. However, it has not yet been exploited for use as a resource. This paper reported the synthesis and characterization of amorphous iron nanoparticles (Ec-Fe-NPs) from Fe(III) salts in aqueous extracts of Eichhornia crassipes. The nanoparticles were characterized by SEM, EDS, TEM, XPS, FTIR, DLS and the zeta potential methods. The characterization results confirmed the successful synthesis of amorphous iron nanoparticles with diameters of 20-80 nm. Moreover, the nanoparticles were mainly composed of zero valent iron nanoparticles which were coated with various organic matters in the extracts as a capping or stabilizing agents. Batch experiments showed that 89.9% of Cr(VI) was removed by the Ec-Fe-NPs much higher than by the extracts alone (20.4%) and Fe3O4 nanoparticles (47.3%). Based on the kinetics study and the XPS analysis, a removal mechanism dominated by adsorption and reduction with subsequently co-precipitation was proposed.

  17. Natural biosorbents (garlic stem and horse chesnut shell) for removal of chromium(VI) from aqueous solutions.

    Science.gov (United States)

    Parlayıcı, Şerife; Pehlivan, Erol

    2015-12-01

    The biosorption of Cr(VI) by the garlic stem (GS)-Allium sativum L. and horse chesnut shell (HCS)-Aesculus hippocastanum plant residues in a batch type reactor was studied in detail for the purpose of wastewater treatment. The influence of initial Cr(VI) concentration, time, and pH was investigated to optimize Cr(VI) removal from aqueous solutions and equilibrium isotherms and kinetic data. This influence was evaluated. The adsorption capacity of the GS and the HCS for Cr(VI) was determined with the Langmuir and Freundlich isotherm models, and the data was fitted to the Langmuir. The adsorption capacity of the GS and the HCS was found to be 103.09 and 142.85 mg/g of adsorbent from a solution containing 3000 ppm of Cr(VI), respectively. The GS's capacity was considerably lower than that of the HCS in its natural form. Gibbs free energy was spontaneous for all interactions, and the adsorption process exhibited exothermic enthalpy values. The HCS was shown to be a promising biosorbent for Cr(VI) removal from aqueous solutions.

  18. Polyacrylonitrile/polyaniline core/shell nanofiber mat for removal of hexavalent chromium from aqueous solution: mechanism and applications

    KAUST Repository

    Wang, Jianqiang

    2013-01-01

    Polyacrylonitrile/polyaniline core/shell nanofibers were prepared via electrospinning followed by in situ polymerization of aniline. Nanofibers with different morphology were obtained by changing the polymerization temperature. When used as absorbent for Cr(vi) ions, the core/shell nanofiber mats exhibit excellent adsorption capability. The equilibrium capacity is 24.96, 37.24, and 52.00 mg g-1 for 105, 156, and 207 mg L-1 initial Cr(vi) solution, respectively, and the adsorption capacity increases with temperature. The adsorption follows a pseudo second order kinetics model and is best fit using the Langmuir isotherm model. The mats show excellent selectivity towards Cr(vi) ions in the presence of competing ions albeit a small decrease in adsorption is observed. The mats can be regenerated and reused after treatment with NaOH making them promising candidates as practical adsorbents for Cr(vi) removal. © The Royal Society of Chemistry 2013.

  19. Removal of Chromium(VI from aqueous solution using guar gum–nano zinc oxide biocomposite adsorbent

    Directory of Open Access Journals (Sweden)

    Tabrez A. Khan

    2017-05-01

    Full Text Available Guar gum–nano zinc oxide (GG/nZnO biocomposite was used as an adsorbent for enhanced removal of Cr(VI from aqueous solution. The maximum adsorption was achieved at 50 min contact time, 25 mg/L Cr(VI conc., 1.0 g/L adsorbent dose and 7.0 pH. Langmuir, Freundlich, Dubinin–Kaganer–Radushkevich and Temkin isotherm models were used to interpret the experimental data. The data obeyed both Langmuir and Freundlich models (R2 = 0.99 indicating a multilayer adsorption of Cr(VI onto the heterogeneous surface. The linear plots of Temkin isotherm showed adsorbent-adsorbate interactions. Moreover, the energy obtained from DKR isotherm (1.58–2.24 kJ/mol indicated a physical adsorption of the metal ions onto the adsorbent surface, which implies more feasibility of the regeneration of the adsorbent. GG/nZnO biocomposite adsorbent showed an improved adsorption capacity for Cr(VI (qm = 55.56 mg/g as compared to other adsorbents reported in the literature. Adsorption process followed pseudo-second order kinetics; controlled by both liquid-film and intra-particle diffusion mechanisms. Thermodynamic parameters (ΔGo, ΔHo and ΔSo reflected the feasibility, spontaneity and exothermic nature of adsorption. The results suggested that GG/nZnO biocomposite is economical, eco-friendly and capable to remove Cr(VI from natural water resources.

  20. Mini-Laparoscopy for Removal (Partial) of Adnexae at the Time of Hysterectomy.

    Science.gov (United States)

    Setúbal, António Gutierrez; Alves, João Sequeira; Lavado, Olga; Faria, Joana

    2017-02-01

    prophylactic salpingectomy versus adnexectomy, the patient opted to preserve her ovaries. A TLH with partial removal of the uterosacral ligaments nodules and prophylactic bilateral salpingectomy was performed. To begin, the patient was placed in lithotomy position with Allen stirrups at an angle of approximately 100 degrees. Standard trocar placement was used. A 5- or 10-mm 0° scope was placed at the level of the umbilicus and three 3-mm skin incisions were made for accessory lower quadrant trocar placement: 2 lateral, approximately 3 cm medial to the anterior superior iliac spine, and 1 suprapubic, slightly higher than the line made by the lateral trocars, ensuring that the distance between this port and the camera trocar exceeded 8 cm. This triangulation of the accessory ports allowed for good ergonomics for the surgeon. The procedure continued with abdominopelvic cavity inspection and bilateral transperitoneal ureter identification and eventual adhesiolysis, and then the following steps: The instruments used were a 10-mm scope, a 3-mm bipolar forceps, 3-mm cold scissors, a 3-mm suction-irrigation device and 3-mm grasping forceps. Mini-laparoscopy is an alternative to classic laparoscopy associated with greater patient satisfaction. Prophylactic salpingectomy has proven to reduce the risk of ovary, peritoneal, and tubal epithelial carcinomas as well as benign tubal diseases, and does not significantly increase the operative time or the incidence of postoperative complications. Copyright © 2016 AAGL. Published by Elsevier Inc. All rights reserved.

  1. Removal of Chromium(VI from Aqueous Solutions Using Fe3O4 Magnetic Polymer Microspheres Functionalized with Amino Groups

    Directory of Open Access Journals (Sweden)

    Kai Wang

    2015-12-01

    Full Text Available Magnetic polymer microspheres (MPMs using glycidylmethacrylate (GMA as a functional monomer were synthesized in the presence of Fe3O4 nanoparticles via dispersion polymerization. After polymerization, the magnetic polymer microbeads were modified with ethylenediamine (EDA. The obtained ethylenediamine-functionalized magnetic microspheres (EDA-MPMs were characterized by scanning electron microscope (SEM, X-ray diffraction (XRD, vibrating-sample magnetometer (VSM and Fourier transform infrared (FT-IR spectroscopy. Then the EDA-MPMs were applied as adsorbents for the removal of Cr(VI from aqueous solution. Langmuir equation was appropriate to describe the experimental data. The maximum adsorption capacities obtained from the Langmuir model were 236.9, 242.1 and 253.2 mg/g at 298, 308 and 318 K, respectively. The Cr(VI adsorption equilibrium was established within 120 min and the adsorption kinetics was compatibly described by the pseudo-second order equation. The thermodynamic parameters (ΔG°, ΔH°, ΔS° of the sorption process revealed that the adsorption was spontaneous and was an endothermic process. The regeneration study demonstrated that the EDA-MPMs could be repeatedly utilized with no significant loss of adsorption efficiency.

  2. Removal combined with reduction of hexavalent chromium from aqueous solution by Fe-ethylene glycol complex microspheres

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Yong-Xing [School of Physics and Electronic Information, Huaibei Normal University, Huaibei 235000 (China); Jia, Yong, E-mail: yjiaahedu@163.com [School of Pharmacy, Anhui University of Chinese Medicine, Hefei 230012 (China)

    2016-12-15

    Highlights: • Fe-EG complex microspheres were synthesized by a hydrothermal method. • The removal properties towards Cr(VI) ions were investigated. • The adsorption and reduction mechanism was revealed by FTIR and XPS. - Abstract: Three-dimensional Fe-ethylene glycol (Fe-EG) complex microspheres were synthesized by a facile hydrothermal method, and were characterized by field emission scanning electron microscopy and transmission electron microscopy. The adsorption as well as reduction properties of the obtained Fe-EG complex microspheres towards Cr(VI) ions were studied. The experiment data of adsorption kinetic and isotherm were fitted by nonlinear regression approach. In neutral condition, the maximum adsorption capacity was 49.78 mg g{sup −1} at room temperature, and was increased with the increasing of temperature. Thermodynamic parameters including the Gibbs free energy, standard enthalpy and standard entropy revealed that adsorption of Cr(VI) was a feasible, spontaneous and endothermic process. Spectroscopic analysis revealed the adsorption of Cr(VI) was a physical adsorption process. The adsorbed CrO{sub 4}{sup 2−} ions were partly reduced to Cr(OH){sub 3} by Fe(II) ions and the organic groups in the Fe-EG complex.

  3. Forças de mordida relacionadas a próteses parciais removíveis inferiores Biting forces related to partially removable mandibular dentures

    Directory of Open Access Journals (Sweden)

    Eduardo Piza PELLIZZER

    1998-10-01

    Full Text Available A pesquisa teve como objetivo determinar as forças de mordida de 73 indivíduos, por meio de um gnatodinamômetro. Os pacientes eram portadores de próteses parciais removíveis inferiores classes I, II ou III. A arcada antagonista era prótese, parcial removível ou fixa, ou total. Os resultados permitiram concluir que: as selas de extremidade livre, principalmente em suas posições extremas, conduziram a forças de mordida muito baixas; o envolvimento de prótese total, também, conduziu a forças de mordida baixas; o sexo masculino alcançou valores maiores que o feminino; com prótese parcial removível classe III, os dentes naturais molares e pré-molares desenvolveram valores maiores do que com classes I e II.The purpose of this study was to determine the biting forces of individuals wearing classes I, II or III partially removable mandibular dentures. Upper jaws presented fixed bridges, classes I, II or III partially removable dentures, or complete dentures. Measurements of biting forces were obtained by a gnathodynamometer. The conclusions were: classes I and II presented low biting forces, specially far from the last abutment tooth; when the opposite arcade was a complete denture, biting forces were low; males presented higher biting forces than females; natural molars and bicuspids presented higher biting forces with class III than with classes I or II.

  4. Efficacy of Denture Cleansers in Reducing Microbial Counts from Removable Partial Dentures: A Short-Term Clinical Evaluation

    OpenAIRE

    Lucena-Ferreira,Silvia Carneiro de; Cavalcanti,Indira Moraes Gomes; Cury,Altair Antoninha Del Bel

    2013-01-01

    This clinical study investigated if daily immersion in denture cleansers reduces microbial counts on removable partial denture's (RPD) biofilm. Twenty-five RPD wearer volunteers were selected and instructed to complement the hygiene of their dentures by immersing them in an enzymatic peroxide-based denture cleanser (Polident® 3 minute) once a day for 3 min for a period of 15 days. The biofilm was collected from RPD surfaces with a swab immediately before (baseline) and after the experimental ...

  5. Cell cycle indicators of buccal epithelial cells in the treatment of different types of removable plate partial dentures

    OpenAIRE

    E. V. Beliaiev; M. P. Odud; D. A. Lysenko

    2018-01-01

    The purpose of the work. To investigate nuclear DNA and buccal epithelial cells proliferative activity in patients with dental defects, who use removable partial dentures plates made of acrylic or thermoplastic. Materials and Methods. The study of buccal epithelial cell cycle parameters was carried out in 70 people. Among them 23 patients were treated with acrylic dentures prostheses, 23 patients – with thermoplastic-based prostheses. The comparison group consisted of 24 clinically health...

  6. Effect of implant support on mandibular distal extension removable partial dentures: relationship between denture supporting area and stress distribution.

    Science.gov (United States)

    Sato, Maki; Suzuki, Yasunori; Kurihara, Daisuke; Shimpo, Hidemasa; Ohkubo, Chikahiro

    2013-04-01

    This study explored the relationship between implant support and the denture-supporting area by comparing the stability of an implant-supported distal extension removable partial denture and a conventional distal extension removable partial denture. A model simulating a mandibular bilateral distal extension missing (#34-37 and #44-47) was fabricated using silicone impression material as soft tissue (2 mm thick) on an epoxy resin bone model. The denture base was reduced by 5 mm cutting part of both the retromolar pad and the lingual border. Loads of up to 5 kg were applied, and the pressure and displacement of the RPDs were simultaneously measured and analyzed using the Wilcoxon test (αremovable partial denture (ISRPD) was significantly less than on the conventional RPD (CRPD). As the supporting area of the denture base decreased, the pressure and the denture displacement of the CRPD were greater than for the ISRPD. This study indicated that implant placement at the distal edentulous ridge can prevent denture displacement of the distal extension bases, regardless of the supporting area of the denture base. Copyright © 2013 Japan Prosthodontic Society. Published by Elsevier Ltd. All rights reserved.

  7. Effects of denture maintenance on satisfaction levels of Taiwanese elderly using removable partial dentures: a pilot study.

    Science.gov (United States)

    Wu, Ju-Hui; Yang, Yi-Hsin; Wang, Chau-Hsiang; Lee, Huey-Er; Du, Je-Kang

    2012-06-01

    The aim of this study was to evaluate the correlation between patient satisfaction with removable partial dentures and denture maintenance by patients, including regular application of denture adhesives and cleansers. The success of removable partial dentures depends on patient satisfaction with dentures and their regular denture maintenance. Demographic information, the Oral Impacts on Daily Performance (OIDP) indicator and details of denture maintenance (including the use of denture cleansers and adhesives) were collected from 193 (41.5% men and 58.5% women) participants by using questionnaires. A dentist performed oral examinations to evaluate denture function according to the OIDP items photographically and recorded the number of remaining teeth and Kennedy's classification. Most participants were satisfied with their removable partial dentures and tended to have higher satisfaction levels than the dentist's estimation. Further, those using denture adhesives and cleansers had higher satisfaction levels than those not using such denture maintenance. Appropriate education regarding denture use is important because regular denture maintenance by patients affects their degree of satisfaction with dentures, as well as the dentist's skill and the patient's oral condition. Dentists could use this information to predict the potential success of dentures. © 2011 The Gerodontology Society and John Wiley & Sons A/S.

  8. Multicentre prospective evaluation of implant-assisted mandibular bilateral distal extension removable partial dentures: patient satisfaction

    NARCIS (Netherlands)

    Wismeijer, D.; Tawse-Smith, A.; Payne, A.G.T.

    2013-01-01

    Objective To compare the levels of patient satisfaction with either conventional mandibular bilateral distal extension partial dentures or those assisted by bilateral distal implants. Materials and methods Forty-eight participants who were dissatisfied with their existing conventional mandibular

  9. Comparison of functionally orientated tooth replacement and removable partial dentures on the nutritional status of partially dentate older patients: a randomised controlled clinical trial.

    Science.gov (United States)

    McKenna, Gerald; Allen, P Finbarr; O'Mahony, Denis; Flynn, Albert; Cronin, Michael; DaMata, Cristiane; Woods, Noel

    2014-06-01

    The aims of this study were to conduct a randomised controlled clinical trial (RCT) of partially dentate older adults comparing functionally orientated treatment based on the SDA concept with conventional treatment using RPDs to replace missing natural teeth. The two treatment strategies were evaluated according to their impact on nutritional status measured using haematological biomarkers. A randomised controlled clinical trial (RCT) was conducted of partially dentate patients aged 65 years and older (Trial Registration no. ISRCTN26302774). Each patient provided haematological samples which were screened for biochemical markers of nutritional status. Each sample was tested in Cork University Hospital for serum Albumin, serum Cholesterol, Ferritin, Folate, Vitamin B12 and 25-hydroxycholecalciferol (Vitamin D). A mixed model analysis of covariance (ANCOVA) indicated that for Vitamin B12 (p=0.9392), serum Folate (p=0.5827), Ferritin (p=0.6964), Albumin (p=0.8179), Serum Total Cholesterol (p=0.3670) and Vitamin D (p=0.7666) there were no statistically significant differences recorded between the two treatment groups. According to the mixed model analysis of covariance (ANCOVA) for Vitamin D there was a significant difference between levels recorded at post-operative time points after treatment intervention (p=0.0470). There was an increase of 7% in 25-hydroxycholecalciferol levels recorded at 6 months compared to baseline (p=0.0172). There was no further change in recorded levels at 12 months (p=0.6482) and these increases were similar within the two treatment groups (p>0.05). The only measure which illustrated consistent significant improvements in nutritional status for either group were Vitamin D levels. However no significant difference was recorded between the two treatment groups. Functionally orientated prosthodontic rehabilitation for partially dentate older patients was no worse than conventional removable partial dentures in terms of impact on nutritional

  10. The effect of magnesium on partial sulphate removal from mine water as gypsum.

    Science.gov (United States)

    Tolonen, Emma-Tuulia; Rämö, Jaakko; Lassi, Ulla

    2015-08-15

    The aim of this research was to investigate the effect of magnesium on the removal efficiency of sulphate as gypsum from mine water. The precipitation conditions were simulated with MINEQL + software and the simulation results were compared with the results from laboratory jar test experiments. Both the simulation and the laboratory results showed that magnesium in the mine water was maintaining sulphate in a soluble form as magnesium sulphate (MgSO4) at pH 9.6. Thus magnesium was preventing the removal of sulphate as gypsum (CaSO4·2H2O). However, change in the lime precipitation pH from 9.6 to 12.5 resulted in magnesium hydroxide (Mg(OH)2) precipitation and improved sulphate removal. Additionally, magnesium hydroxide could act as seed crystals for gypsum precipitation or co-precipitate sulphate further enhancing the removal of sulphate from mine water. Copyright © 2015 Elsevier Ltd. All rights reserved.

  11. The removable acrylic partial denture in primary care: the experience and satisfaction of dental surgeons

    Directory of Open Access Journals (Sweden)

    Rita de Cássia SILVA

    2017-11-01

    Full Text Available Abstract Introduction The guidelines of the National Politics of Oral Health have led to the inclusion of elemental prostheses in the list of Primary Care procedures. Objective This paper aimed to evaluate the performance and satisfaction of dental surgeons with the implementation of Acrylic Partial Dentures. Metodology The sample was composed by 159 dental surgeons (sample calculation, in Belo Horizonte, MG, Brazil, selected via raffle (simple random sampling. A structured questionnaire was built with 72 questions on the daily practice of the performance of dental surgeons, using the SurveyMonkey platform. Result The results showed that for most of dental surgeons, the inclusion on the list of primary care procedures was a positive initiative and they have enjoyed the experience of using Acrylic Partial Dentures. Dental surgeons who had graduated in private institutions reported to have had more failures than those who had graduated in public institutions. The better prepared dental surgeons reported less difficulties and failures, and the more satisfied professionals with the performance of Acrylic Partial Dentures related had also experienced fewer failures. Considering the indication, the majority of participants did it according to the protocol of the institution (only for anterior teeth but many revealed the use of dentures also for premolars. Conclusion Acrylic partial dentures have been a reality in the Brazilian social context even before their inclusion in the list of Primary Care procedures. Such inclusion indicates their relevance; however, it is necessary to have their confection systematized by a protocol in public services.

  12. [Quantitative and qualitative analysis of oral microbiota by orthopedic rehabilitation with full and partial removable dentures].

    Science.gov (United States)

    Stafeev, A A; Chesnokova, M G; Chesnokov, V A

    2015-01-01

    Microbiological analysis of biomaterial surface in dental prosthesis showed the most common colonizing gram-positive species to be S. aureus, Micrococcus spp., S. haemolyticus, E. faecalis, mainly massive colonization with S. aureus was seen. The highest concentration of C. albicans colonization was found in removable dentures and may have a destructive effect on prosthetic material.

  13. [Treatment of removable partial dentures. 2. Causes and consequences of a reduced occlusal system

    NARCIS (Netherlands)

    Witter, D.J.; Barel, J.C.; Baat, C. de; Keltjens, H.M.A.M.; Creugers, N.H.J.

    2011-01-01

    The occlusal system is part of the orofacial system and consists of the maxillary and mandibular alveolar ridge and teeth which are occluding or not or the removable denture teeth. The most prevalent causes of loss of teeth are insufficient oral self care or inadequate professional oral healthcare

  14. Removal of chromium hexavalent of residual water from tannery using hydrotalcite; Remocion de cromo hexavalente de aguas residuales de teneria utilizando hidrotalcita

    Energy Technology Data Exchange (ETDEWEB)

    Martinez G, S.; Martinez, V.; Bulbulian, S. [Instituto nacional de Investigaciones Nucleares, A.P. 18-1027, C.P. 11801 Mexico D.F. (Mexico)

    2000-07-01

    One of the main problems of leather tanned is the treatment that must be give to the waste water polluted with chrome which stays in trivalent form, but it is easily oxidated at chromium hexavalent. This work pretends to find an elimination media for chromium (VI) from water using the original synthetic hydrotalcite and calcined as sorbent by its anion exchange and memory effect properties. The tannery water was characterized by X-ray diffraction, thermal gravimetric analysis, specific surface and infrared spectroscopy. (Author)

  15. Loading Variables on Implant-Supported Distal-Extension Removable Partial Dentures: An In Vitro Pilot Study.

    Science.gov (United States)

    Hirata, Kiyotaka; Takahashi, Toshihito; Tomita, Akiko; Gonda, Tomoya; Maeda, Yoshinobu

    2016-01-01

    The aim of this study was to investigate strain on implants used for adjunctive support of distal extension removable partial dentures. An implant with strain gauges was used for testing purposes in two positions, parallel and inclined. Three loading scenarios--loading apparatus (LA), artificial teeth via cotton roll (CR), and artificial teeth (UT)--were studied and strains compared via the Kruskal-Wallis test (P=.05). Strain under CR was significantly larger than UT in parallel (P<.05). However, the opposite was observed in inclined. Strain in parallel was smallest for UT, whereas in inclined it was largest for CR.

  16. The removable acrylic partial denture in primary care: the experience and satisfaction of dental surgeons

    OpenAIRE

    Rita de Cássia SILVA; Raquel Conceição FERREIRA; Denise Vieira TRAVASSOS; Andréa Maria Duarte VARGAS

    2017-01-01

    Abstract Introduction The guidelines of the National Politics of Oral Health have led to the inclusion of elemental prostheses in the list of Primary Care procedures. Objective This paper aimed to evaluate the performance and satisfaction of dental surgeons with the implementation of Acrylic Partial Dentures. Metodology The sample was composed by 159 dental surgeons (sample calculation), in Belo Horizonte, MG, Brazil, selected via raffle (simple random sampling). A structured questionnaire...

  17. Microbiological analysis after complete or partial removal of carious dentin using two different techniques in primary teeth: A randomized clinical trial

    Science.gov (United States)

    Singhal, Deepak Kumar; Acharya, Shashidhar; Thakur, Arun Singh

    2016-01-01

    Background: The management of deep carious lesions can be done by various techniques but residual caries dilemma still persists and bacterial reduction in cavities treated by either partial or complete caries removal techniques is debatable. So the objective of the present randomized clinical trial was to compare microbial counts in cavities submitted to complete caries removal and partial caries removal using either hand instruments or burs before and after 3 weeks of restoration. Materials and Methods: Primary molars with acute carious lesions in inner half of dentine and vital pulp were randomly divided into three groups of 14 each: Group A: Partial caries removal using hand instruments atraumatic restorative treatment (ART) only; Group B: Partial caries removal using bur; Group C: Complete caries removal using bur and caries detector dye. Dentine sample obtained after caries removal and 3 weeks after restoration, were subjected to microbial culture and counting (colony-forming units [CFU]/mg of dentine) for total viable bacterial count, Streptococcus spp., mutans streptococci, Lactobacillus spp. Results: Three techniques of caries removal showed significant (P < 0.05) reduction in all microorganisms studied after 3 weeks of evaluation, but there was no statistically significant difference in percentage reduction of microbial count among three groups. Conclusion: Results suggest the use of partial caries removal in a single session as compared to complete caries removal as a part of treatment of deep lesions in deciduous teeth in order to reduce the risk of pulp exposure. Partial caries removal using ART can be preferred for community settings as public health procedure for caries management. PMID:26962313

  18. [Effect of removable partial dentures restoration on oral health-related quality of life of patients with shortened dental arch].

    Science.gov (United States)

    Fu, Zhen-nan; Lin, Xue-feng

    2013-11-01

    To assess the effect of removable partial dentures (PRD) restoration on oral health-related quality of life (OHRQOL) of subjects with shortened dental arches (SDA) using the Chinese version of the Oral Health Impact Profile (OHIP-14). Consecutive patients with shortened dental arches were recruited from the Department of Prosthodontics, Foshan Chancheng Hospital of Stomatology. The Chinese version of OHIP-14 was administered to each subject before treatment and after treatment. The subjective outcomes of removable partial dentures therapy on SDA were collected and the pre- and post-treatment scores of the Chinese version of OHIP-14 were compared. After treatment, significant decrease in patients' total score of OHRQOL [before: 9 (6, 12) ; after: 4 (2.25, 6)] was detected, as well as physical pain subscale, physical disability subscale and handicap subscale; and the score of OHRQOL in function limitation subscale increased [before: 0(0,0); after: 2(1, 2)]. The main impacts of shortened dental arch with intact anterior region affecting patients' OHRQOL are physical disability.From a quality-of-life perspective, patients with SDA can perceive benefits from RPD.

  19. Finite Element Analysis of Implant-Assisted Removable Partial Denture Attachment with Different Matrix Designs During Bilateral Loading.

    Science.gov (United States)

    Shahmiri, Reza; Das, Raj

    2016-01-01

    The aim of this study was to investigate the effect of different matrix designs on resilient attachment on an implant-assisted removable partial denture (IARPD) using finite element analysis (FEA). A laser scanner was used to extract the geometrical data of a human partially edentulous mandible. A 12-mm-long and 4.8-mm-diameter-wide implant was modeled, and two types of intradental attachment of snap fastener principle (elliptical) and resilient attachment (titanium) matrices were modeled along with tooth roots and periodontal ligaments. The modeling was performed with a combination of reverse engineering and solid modeling. The model incorporated a removable partial denture and was loaded with realistic bilateral forces. The FEA was used to analyze the stress and strain distributions in the IARPD and in the metal framework. Stresses and deformations in the metal framework and resin denture base surfaces were analyzed for the elliptical and titanium matrix designs. The maximum von Mises stresses were 605.85 and 614.96 MPa in the metal framework surface and 10.35 and 10.63 MPa in the resin denture base surface, respectively, for the elliptical and titanium matrix designs. The maximum deformations (displacements) were 418.5 and 428.3 μm in the metal framework surface for the elliptical and titanium matrix designs, respectively. The corresponding values of displacements for the resin denture base surface were 325.52 and 249.22 μm for the elliptical and titanium matrix designs, respectively. The maximum displacements in the matrixes were, however, nearly the same (229.51 and 229.47 μm) for both the elliptical and titanium matrixes. The titanium matrix design was a more favorable design compared with the elliptical design, because it had lower lateral deformation as indicated by the maximum displacement.

  20. Experience of partial dismantling and large component removal of light water reactors

    International Nuclear Information System (INIS)

    Dubourg, M.

    1987-01-01

    Not any of the French PWR reactors need to be decommissioned before the next decade or early 2000. However, feasibility studies of decommissioning have been undertaken and several dismantling scenarios have been considered including the dismantling of four PWR units and the on-site entombment of the active components into a reactor building for interim disposal. In addition to theoretical evaluation of radwaste volume and activity, several operations of partial dismantling of active components and decontamination activities have been conducted in view of dismantling for both PWR and BWR units. By analyzing the concept of both 900 and 1300 MWe PWR's, it appears that the design improvements taken into account for reducing occupational dose exposure of maintenance personnel and the development of automated tools for performing maintenance and repairs of major components, contribute to facilitate future dismantling and decommissioning operations

  1. Occlusion removal method of partially occluded 3D object using sub-image block matching in computational integral imaging.

    Science.gov (United States)

    Shin, Dong-Hak; Lee, Byung-Gook; Lee, Joon-Jae

    2008-10-13

    In this paper, we propose an occlusion removal method using sub-image block matching for improved recognition of partially occluded 3D objects in computational integral imaging (CII). When 3D plane images are reconstructed in CII, occlusion degrades the resolution of reconstructed images. To overcome this problem, we apply the sub-image transform to elemental image array (EIA) and these sub-images are employed using block matching method for depth estimation. Based on the estimated depth information, we remove the unknown occlusion. After completing the occlusion removal for all sub-images, we obtain the modified EIA without occlusion information through the inverse sub-image transform. Finally, the 3D plane images are reconstructed by using a computational integral imaging reconstruction method with the modified EIA. The proposed method can provide a substantial gain in terms of the visual quality of 3D reconstructed images. To show the usefulness of the proposed method we carry out some experiments and the results are presented.

  2. Possibilities for reduction of transverse projected emittances by partial removal of transverse to longitudinal beam correlations

    International Nuclear Information System (INIS)

    Balandin, V.; Decking, W.; Golubeva, N.

    2014-09-01

    We show that if in the particle beam there are linear correlations between energy of particles and their transverse positions and momenta (linear beam dispersions), then the transverse projected emittances always can be reduced by letting the beam to pass through magnetostatic system with specially chosen nonzero lattice dispersions. The maximum possible reduction of the transverse projected emittances occurs when all beam dispersions are zeroed, and the values of the lattice dispersions required for that are completely defined by the values of the beam dispersions and the beam rms energy spread and are independent from any other second-order central beam moments. Besides that, we prove that, alternatively, one can also use the lattice dispersions to remove linear correlations between longitudinal positions of particles and their transverse coordinates (linear beam tilts), but in this situation solution for the lattice dispersions is nonunique and the reduction of the transverse projected emittances is not guaranteed.

  3. Retrospective comparative ten-year study of cumulative survival rates of remaining teeth in large edentulism treated with implant-supported fixed partial dentures or removable partial dentures.

    Science.gov (United States)

    Yamazaki, Seiya; Arakawa, Hikaru; Maekawa, Kenji; Hara, Emilio Satoshi; Noda, Kinji; Minakuchi, Hajime; Sonoyama, Wataru; Matsuka, Yoshizo; Kuboki, Takuo

    2013-07-01

    This study aimed to compare the survival rates of remaining teeth between implant-supported fixed dentures (IFDs) and removable partial dentures (RPDs) in patients with large edentulous cases. The second goal was to assess the risk factors for remaining tooth loss. The study subjects were selected among those who received prosthodontic treatment at Okayama University Dental Hospital for their edentulous space exceeding at least four continuous missing teeth. Twenty-one patients were included in the IFD group and 82 patients were included in the RPD group. Survival rates of remaining teeth were calculated in three subcategories: (1) whole remaining teeth, (2) adjacent teeth to intended edentulous space, and (3) opposing teeth to intended edentulous space. The ten-year cumulative survival rate of the whole remaining teeth was significantly higher in the IFD group (40.0%) than in the RPD group (24.4%). On the other hand, there was no significant difference between two groups in the survival rate of teeth adjacent or opposing to intended edentulous space. A Cox proportional hazard analysis revealed that RPD restoration and gender (male) were the significant risk factors for remaining tooth loss (whole remaining teeth). These results suggest that IFD treatment can reduce the incidence of remaining tooth loss in large edentulous cases. Copyright © 2013 Japan Prosthodontic Society. Published by Elsevier Ltd. All rights reserved.

  4. Sorption of chromium(III) and chromium(VI) on lead sulfide

    International Nuclear Information System (INIS)

    Music, S.

    1985-01-01

    The sorption of chromium(III) and chromium(VI) on lead sulfide was investigated in dependence on pH, time of sorption, and on the concnetrations of sorbate and sorbent. The mechanisms of the sorption of Crsup(3+) and CrOsub(4)sup(2-) traces on lead sulfide are discussed; a difference between CrOsub(4)sup(2-) sorption on PbS and α-Fesub(2)Osub(3) was found. Sulfates and molybdates affect the removal of chromates from aqueous solutions. Lead sulfide carrier prepared in this work was also used for the preconcentration of chromium(III) and chromium(VI) from tap water. (author)

  5. Gum karaya (Sterculia urens) stabilized zero-valent iron nanoparticles: characterization and applications for the removal of chromium and volatile organic pollutants from water

    Czech Academy of Sciences Publication Activity Database

    Vinod, V.T.P.; Waclawek, S.; Senan, Ch.; Kupčík, Jaroslav; Pešková, K.; Černík, M.; Somashekarappa, H. M.

    2017-01-01

    Roč. 7, č. 23 (2017), s. 13997-14009 ISSN 2046-2069 R&D Projects: GA MŠk(CZ) LM2015073 Institutional support: RVO:61388980 Keywords : nanoscale zerovalent iron * ray photoelectron-spectroscopy * groundwater remediation * hexavalent chromium * xanthan gum * guar gum * waste-water Subject RIV: CA - Inorganic Chemistry OBOR OECD: Inorganic and nuclear chemistry Impact factor: 3.108, year: 2016

  6. The influence of removable partial dentures on the periodontal health of abutment and non-abutment teeth.

    Science.gov (United States)

    Dula, Linda J; Shala, Kujtim Sh; Pustina-Krasniqi, Teuta; Bicaj, Teuta; Ahmedi, Enis F

    2015-01-01

    The aim of this study was to evaluate the influence of removable partial dentures (RPD) on the periodontal health of abutment and non-abutment teeth. A total 107 patients with RPD participated in this study. It was examined 138 RPD, they were 87 with clasp-retained and 51 were RPD with attachments. The following periodontal parameters were evaluated for abutment and non-abutment teeth, plaque index (PLI), calculus index (CI), bleeding on probing (BOP), probing depth (PD) (mm) and tooth mobility (TM) index. These clinical measurements were taken immediately before insertion the RPD, then one and 3 months after insertion. The level of significance was set at (P 0.05). With carefully planned prosthetic treatment and adequate maintenance of the oral and denture hygiene, we can prevent the periodontal diseases.

  7. A critically appraised topic review of computer-aided design/computer-aided machining of removable partial denture frameworks.

    Science.gov (United States)

    Lang, Lisa A; Tulunoglu, Ibrahim

    2014-01-01

    A critically appraised topic (CAT) review is presented about the use of computer-aided design (CAD)/computer-aided machining (CAM) removable partial denture (RPD) frameworks. A systematic search of the literature supporting CAD/CAM RPD systems revealed no randomized clinical trials, hence the CAT review was performed. A PubMed search yielded 9 articles meeting the inclusion criteria. Each article was characterized by study design and level of evidence. No clinical outcomes research has been published on the use of CAD/CAM RPDs. Low levels of evidence were found in the available literature. Clinical research studies are needed to determine the efficacy of this treatment modality. Copyright © 2014 Elsevier Inc. All rights reserved.

  8. Resolution of Metallic Biliary Stent Allergic Reaction After Partial Stent Removal in a Patient with Nickel Sensitivity.

    Science.gov (United States)

    Esparaz, Anthony M; Ahmed, Muneeb

    2017-07-01

    Local and systemic reactions to implanted metallic devices, particularly to those containing nickel, are well documented. Metal ions are released due to exposure of the metal to blood, proteins, other body fluids, and sheer mechanical stress. Metal ions then complex with native proteins and become antigens, which can elicit hypersensitivity reactions. Another case report depicts a specific allergic complication (early stent occlusion) related to metallic biliary stent implantation. We present a case of allergic symptoms, associated with eating, in a patient who developed nickel sensitivity after biliary metal stent placement confirmed by allergic skin testing to the same metallic biliary stent placed one year earlier. Symptoms resolved following partial removal of the non-epithelialized portion of the biliary stent.

  9. Maxillary rehabilitation using a removable partial denture with attachments in a cleft lip and palate patient: a clinical report.

    Science.gov (United States)

    Palmeiro, Marina Rechden Lobato; Piffer, Caroline Scheeren; Brunetto, Vivian Martins; Maccari, Paulo César; Shinkai, Rosemary Sadami Arai

    2015-04-01

    Clefts of the lip and/or palate (CLP) are oral-facial defects that affect health and overall quality of life. CLP patients often need multidisciplinary treatment to restore oral function and esthetics. This paper describes the oral rehabilitation of a CLP adult patient who had maxillary bone and tooth loss, resulting in decreased occlusal vertical dimension. Functional and cosmetic rehabilitation was achieved using a maxillary removable partial denture (RPD) attached to telescopic crowns. Attachment-retained RPDs may be a cost-effective alternative for oral rehabilitation in challenging cases with substantial loss of oral tissues, especially when treatment with fixed dental prostheses and/or dental implants is not possible. © 2014 by the American College of Prosthodontists.

  10. Periodontal ligament influence on the stress distribution in a removable partial denture supported by implant: a finite element analysis

    Directory of Open Access Journals (Sweden)

    Carlos Marcelo Archangelo

    2012-06-01

    Full Text Available OBJECTIVES: The non-homogenous aspect of periodontal ligament (PDL has been examined using finite element analysis (FEA to better simulate PDL behavior. The aim of this study was to assess, by 2-D FEA, the influence of non-homogenous PDL on the stress distribution when the free-end saddle removable partial denture (RPD is partially supported by an osseointegrated implant. MATERIAL AND METHODS: Six finite element (FE models of a partially edentulous mandible were created to represent two types of PDL (non-homogenous and homogenous and two types of RPD (conventional RPD, supported by tooth and fibromucosa; and modified RPD, supported by tooth and implant [10.00x3.75 mm]. Two additional Fe models without RPD were used as control models. The non-homogenous PDL was modeled using beam elements to simulate the crest, horizontal, oblique and apical fibers. The load (50 N was applied in each cusp simultaneously. Regarding boundary conditions the border of alveolar ridge was fixed along the x axis. The FE software (Ansys 10.0 was used to compute the stress fields, and the von Mises stress criterion (svM was applied to analyze the results. RESULTS: The peak of svM in non-homogenous PDL was higher than that for the homogenous condition. The benefits of implants were enhanced for the non-homogenous PDL condition, with drastic svM reduction on the posterior half of the alveolar ridge. The implant did not reduce the stress on the support tooth for both PDL conditions. Conclusion: The PDL modeled in the non-homogeneous form increased the benefits of the osseointegrated implant in comparison with the homogeneous condition. Using the non-homogenous PDL, the presence of osseointegrated implant did not reduce the stress on the supporting tooth.

  11. Effect of telescopic distal extension removable partial dentures on oral health related quality of life and maximum bite force: A preliminary cross over study.

    Science.gov (United States)

    Elsyad, Moustafa Abdou; Mostafa, Aisha Zakaria

    2018-01-01

    This cross over study aimed to evaluate the effect of telescopic distal extension removable partial dentures on oral health related quality of life and maximum bite force MATERIALS AND METHODS: Twenty patients with complete maxillary edentulism and partially edentulous mandibles with anterior teeth only remaining were selected for this cross over study. All patients received complete maxillary dentures and mandibular partial removable dental prosthesis (PRDP, control). After 3 months of adaptation, PRDP was replaced with conventional telescopic partial dentures (TPD) or telescopic partial dentures with cantilevered extensions (TCPD) in a quasi-random method. Oral health related quality of life (OHRQoL) was measured using OHIP-14 questionnaire and Maximum bite force (MBF) was measured using a bite force transducer. Measurements were performed 3 months after using each of the following prostheses; PRDP, TPD, and TCPD. TCPD showed the OHIP-14 lowest scores (i.e., the highest patient satisfaction with their OHRQoL), followed by TPD, and PRDP showed the highest OHIP-14 scores (i.e., the lowest patient satisfaction with OHRQoL). TCPD showed the highest MBF (70.7 ± 3.71), followed by TPD (57.4 ± 3.43) and the lowest MBF (40.2 ± 2.20) was noted with PRDP. WITHIN The Limitations of This Study, Mandibular Telescopic Distal Extension Removable Partial Dentures with Cantilevered Extensions Were Associated with Improved Oral Health Related Quality of Life and Maximum Bite Force Compared to Telescopic or Conventional PRDP. Telescopic distal extension removable prostheses is an esthetic restoration in partially edentulous patients with free end saddle. This article describes the addition of cantilevered extensions of this prosthesis. The results showed that telescopic distal extension removable prostheses with cantilevered extensions were associated with improved oral health related quality of life and maximum bite force compared to telescopic or conventional RPDs

  12. Potential of Live Spirulina platensis on Biosorption of Hexavalent Chromium and Its Conversion to Trivalent Chromium.

    Science.gov (United States)

    Colla, Luciane Maria; Dal'Magro, Clinei; De Rossi, Andreia; Thomé, Antônio; Reinehr, Christian Oliveira; Bertolin, Telma Elita; Costa, Jorge Alberto Vieira

    2015-01-01

    Microalga biomass has been described worldwide according their capacity to realize biosorption of toxic metals. Chromium is one of the most toxic metals that could contaminate superficial and underground water. Considering the importance of Spirulina biomass in production of supplements for humans and for animal feed we assessed the biosorption of hexavalent chromium by living Spirulina platensis and its capacity to convert hexavalent chromium to trivalent chromium, less toxic, through its metabolism during growth. The active biomass was grown in Zarrouk medium diluted to 50% with distilled water, keeping the experiments under controlled conditions of aeration, temperature of 30°C and lighting of 1,800 lux. Hexavalent chromium was added using a potassium dichromate solution in fed-batch mode with the aim of evaluate the effect of several additions contaminant in the kinetic parameters of the culture. Cell growth was affected by the presence of chromium added at the beginning of cultures, and the best growth rates were obtained at lower metal concentrations in the medium. The biomass removed until 65.2% of hexavalent chromium added to the media, being 90.4% converted into trivalent chromium in the media and 9.6% retained in the biomass as trivalent chromium (0.931 mg.g(-1)).

  13. Cell cycle indicators of buccal epithelial cells in the treatment of different types of removable plate partial dentures

    Directory of Open Access Journals (Sweden)

    E. V. Beliaiev

    2018-02-01

    Full Text Available The purpose of the work. To investigate nuclear DNA and buccal epithelial cells proliferative activity in patients with dental defects, who use removable partial dentures plates made of acrylic or thermoplastic. Materials and Methods. The study of buccal epithelial cell cycle parameters was carried out in 70 people. Among them 23 patients were treated with acrylic dentures prostheses, 23 patients – with thermoplastic-based prostheses. The comparison group consisted of 24 clinically healthy persons without defects in the dentition. DNA content in human buccal epithelial cells nuclei was determined by flow cytometry. Results. The obtained indicators of buccal epithelial cell cycle of the control group indicate a high intensity of cell self-renewal in the normal range. It is suggested by a significant percentage of events occurring within the Sub-G1 range that characterizes apoptosis, as well as the fact that more than half of the cells were in the range of S + G2/M. It has been revealed by flow cytometry that the percentage of apoptosis in cells was higher in patients using acrylic dentures base plastic, showed initial signs of keratinization that was confirmed by increase in cells in the range of Sub-G1 and by their decrease in the range of S-G2/M. It has been established in the study of buccal epithelium cell cycle indicators in the dentures bases thermoplastic application that these prostheses did not affect the proliferative activity of buccal epithelial cells compared to the group using acrylic dentures bases with prolonged use. This is evident in almost the same number of cellular events ranging Sub-G1, so apoptosis in the thermoplastic dentures bases application corresponded to the control group indicators both in the early period and over a year of use. Conclusions. The direct negative effect of prostheses with acrylic bases on the complex mechanism of the oral cavity mucous membrane functioning has been revealed. Absence of dentures

  14. Implant-supported mandibular removable partial dentures; patient-based outcome measures in relation to implant position.

    Science.gov (United States)

    Jensen, Charlotte; Raghoebar, Gerry M; Kerdijk, Wouter; Meijer, Henny J A; Cune, Marco S

    2016-12-01

    To assess the benefits of implant support to Removable Partial Dentures (RPD) in patients with a bilateral free-ending situation in the mandible and to determine the most favorable implant position: the premolar (PM) or the molar (M) region. Thirty subjects with a bilateral unbounded posterior saddle received 2 PM and 2M implants. A new RPD was placed. Implant support was provided 3 months later. Two PM implants supported the RPD. After 3 months the 2M implants were used or vice versa. Outcome measures included oral health related quality of life (OHIP-NL49), general health status (SF-36), contentment assessed on a Visual Analogue Scale (VAS) and the number of hours that the RPD was worn. Data were collected prior to treatment, 3 months after having functioned with a new RPD and after 3 and 6 months with implant support. Finally, patients expressed their preferred implant position. The general health status (SF-36) was not influenced. OHIP-NL49 values and mean wearing-time were statistical significantly more favorable for ISRPD's, regardless of the implant position. Per day, the ISRPD's were worn 2-3h more than the unsupported new RPD. Patients' expectations were met as the VAS-scores of anticipated and realized contentment did not reach a statistical significant level (p>0.05). VAS scores for ISRPD's with M implant support were higher than for PM implant support. Finally, 56.7% of subjects preferred the M implant support, 13.3% expressed no preference and 30% opted for PM implant support. Mandibular implant support favorably influences oral health related patient-based outcome measures in patients with a bilateral free-ending situation. The majority of patients prefer the implant support to be in the molar region. Patients with a bilateral free-ending situation in the mandible opposed by a maxillary denture benefit from implant support to their mandibular removable partial denture. Most patients prefer this support to be in the molar region. Copyright © 2016

  15. Changes in coagulation-fibrinolysis function in alveolar lavage fluid of endotoxemic dogs after partial removal of peripheral leukocytes

    Directory of Open Access Journals (Sweden)

    Shun-gang ZHOU

    2011-06-01

    Full Text Available Objective To observe the effect of partial removal of peripheral leucocytes on the coagulation-fibrinolysis function of alveolar lavage fluid(ALF in endotoxemic dogs,and explore the influence and mechanisms of activated leucocytes on lung injury in endotoxemic dogs.Methods Thirty male mongrel dogs were involved in present study and randomly divided into 3 groups(10 each: LPS group(group L,sham leukocytapheresis group(group S and leukocytapheresis group(group T.Endotoxemic model was reproduced in group L by administration of LPS(2mg/kg,but the animals did not receive leukocytapheresis.Animals in group T received leukocytapheresis using a continuous-flow blood cell separator 12-14 hours after administration of LPS.Animals in group S received sham leukocytapheresis(the end products were transfused back into the dogs at 12-14 hours after administration of LPS.At 36h after administration of LPS,the lung tissues were harvested to obtain ALF,and the levels of neutrophil elastase(NE,soluble thrombomodulin(sTM,activated protein C(APC and plasminogen activator inhibitor-1(PAI-1 in ALF were determined,the expression of thrombomodulin in lung tissue was observed by immunohistochemical staining,while the routine pathological examination and wet/dry ratio of lung tissue were performed.Results The APC level in ALF was significantly higher,while the NE,sTM and PAI-1 levels in ALF and wet/dry ratio of lung tissue were significantly lower in group T than in group L and group S(P < 0.05.Immunohistochemical examination revealed that the expression of thrombomodulin in lung tissue was higher in group T than in group L and group S.No significant difference was found between group L and group S in the indexes mentioned above.Pathological observation showed the incidence of acute lung injury was significantly lower in group T(2/10 than in group L(7/10 and group S(8/10,P < 0.05.Conclusion Partial removal of peripheral leukocytes may lower the level of NE in ALF

  16. Preliminary Clinical Application of Removable Partial Denture Frameworks Fabricated Using Computer-Aided Design and Rapid Prototyping Techniques.

    Science.gov (United States)

    Ye, Hongqiang; Ning, Jing; Li, Man; Niu, Li; Yang, Jian; Sun, Yuchun; Zhou, Yongsheng

    The aim of this study was to explore the application of computer-aided design and rapid prototyping (CAD/RP) for removable partial denture (RPD) frameworks and evaluate the fitness of the technique for clinical application. Three-dimensional (3D) images of dentition defects were obtained using a lab scanner. The RPD frameworks were designed using commercial dental software and manufactured using selective laser melting (SLM). A total of 15 cases of RPD prostheses were selected, wherein each patient received two types of RPD frameworks, prepared by CAD/RP and investment casting. Primary evaluation of the CAD/RP framework was performed by visual inspection. The gap between the occlusal rest and the relevant rest seat was then replaced using silicone, and the specimens were observed and measured. Paired t test was used to compare the average thickness and distributed thickness between the CAD/RP and investment casting frameworks. Analysis of variance test was used to compare the difference in thickness among different zones. The RPD framework was designed and directly manufactured using the SLM technique. CAD/RP frameworks may meet the clinical requirements with satisfactory retention and stability and no undesired rotation. Although the average gap between the occlusal rest and the corresponding rest seat of the CAD/RP frameworks was slightly larger than that of the investment casting frameworks (P designed and fabricated directly using digital techniques with acceptable results in clinical application.

  17. Influence of posterior dental arch length on brain activity during chewing in patients with mandibular distal extension removable partial dentures.

    Science.gov (United States)

    Shoi, K; Fueki, K; Usui, N; Taira, M; Wakabayashi, N

    2014-07-01

    It is well known that shortened dental arch decreases masticatory function. However, its potential to change brain activity during mastication is unknown. The present study investigates the effect of a shortened posterior dental arch with mandibular removable partial dentures (RPDs) on brain activity during gum chewing. Eleven subjects with missing mandibular molars (mean age, 66.1 years) on both sides received experimental RPDs with interchangeable artificial molars in a crossover trial design. Brain activity during gum chewing with RPDs containing (full dental arch) and lacking artificial molars (shortened dental arch) was measured using functional magnetic resonance imaging. Additionally, masticatory function was evaluated for each dental arch type. Food comminuting and mixing ability and the perceived chewing ability were significantly lower in subjects with a shortened dental arch than those with a full dental arch (P < 0.05). Brain activation during gum chewing with the full dental arch occurred in the middle frontal gyrus, primary sensorimotor cortex extending to the pre-central gyrus, supplementary motor area, putamen, insula and cerebellum. However, middle frontal gyrus activation was not observed during gum chewing with the shortened dental arch. These results suggest that shortened dental arch affects human brain activity in the middle frontal gyrus during gum chewing, and the decreased middle frontal gyrus activation may be associated with decreased masticatory function. © 2014 John Wiley & Sons Ltd.

  18. Implant-supported mandibular removable partial dentures: Functional, clinical and radiographical parameters in relation to implant position.

    Science.gov (United States)

    Jensen, Charlotte; Speksnijder, Caroline M; Raghoebar, Gerry M; Kerdijk, Wouter; Meijer, Henny J A; Cune, Marco S

    2017-06-01

    Patients with a Kennedy class I situation often encounter problems with their removable partial denture (RPD). To assess the functional benefits of implant support to RPDs, the clinical performance of the implants and teeth and to determine the most favorable implant position: the premolar (PM) or molar (M) region. Thirty subjects received 2 PM and 2 M implants. A new RPD was made. Implant support was provided 3 months later. In a cross-over model, randomly, 2 implants (PM or M) supported the RPD during 3 months. Masticatory performance was assessed using the mixing ability index (MAI). Clinical and radiographic parameters were assessed. Non-parametric statistical analysis for related samples and post hoc comparisons were performed. Masticatory performance differed significantly between the stages of treatment (P < .001). MAI-scores improved with implant support although the implant position had no significant effect. No complications to the implants or RPD were observed and clinical and radiographical parameters for both implants and teeth were favorable. Higher scores for bleeding on probing were seen for molar implants. Implant support to a Kennedy class I RPD significantly improves masticatory function, regardless of implant position. No major clinical problems were observed. © 2017 Wiley Periodicals, Inc.

  19. Three Dimensional Finite Element Analysis of Distal Abutment Stresses of Removable Partial Dentures with Different Retainer Designs

    Science.gov (United States)

    Zarrati, Simindokht; Heidari, Fatemeh; Kashani, Jamal

    2015-01-01

    Objectives: This finite element method study aimed to compare the amount of stress on an isolated mandibular second premolar in two conventional reciprocal parallel interface designs of removable partial dentures (RPDs) and the same RPD abutment tooth (not isolated). Materials and Methods: A Kennedy Class 1, modification 1 RPD framework was simulated on a 3D model of mandible with three different designs: an isolated tooth with a mesial rest, an isolated tooth with mesial and distal rests and an abutment with a mesial rest (which was not isolated); 26 N occlusal forces were exerted bilaterally on the first molar sites. Stress on the abutment teeth was analyzed using Cosmos Works 2009 Software. Results: In all designs, the abutment tooth stress concentration was located in the buccal alveolar crest. In the first model, the von Mises stress distribution in the contact area of I-bar clasp and cervical portion of the tooth was 19 MPa and the maximum stress was 30 MPa. In the second model, the maximum von Mises stress distribution was 15 MPa in the cervical of the tooth. In the third model, the maximum von Mises stress was located in the cervical of the tooth and the distal proximal plate. Conclusion: We recommend using both mesial and distal rests on the distal abutment teeth of distal extension RPDs. The abutment of an extension base RPD, which is not isolated in presence of its neighboring more anterior tooth, may have a better biomechanical prognosis. PMID:26884772

  20. Assessment of the fit of removable partial denture fabricated by computer-aided designing/computer aided manufacturing technology

    Directory of Open Access Journals (Sweden)

    Khalid A.O. Arafa

    2018-01-01

    Full Text Available Objective: To assess the level of evidence that supports the quality of fit for removable partial denture (RPD fabricated by computer-aided designing/computer aided manufacturing (CAD/CAM and rapid prototyping (RP technology. Methods: An electronic search was performed in Google Scholar, PubMed, and Cochrane library search engines, using Boolean operators. All articles published in English and published in the period from 1950 until April 2017 were eligible to be included in this review. The total number of articles contained the search terms in any part of the article (including titles, abstracts, or article texts were screened, which resulted in 214 articles. After exclusion of irrelevant and duplicated articles, 12 papers were included in this systematic review. Results: All the included studies were case reports, except one study, which was a case series that recruited 10 study participants. The visual and tactile examination in the cast or clinically in the patient’s mouth was the most-used method for assessment of the fit of RPDs. From all included studies, only one has assessed the internal fit between RPDs and oral tissues using silicone registration material. The vast majority of included studies found that the fit of RPDs ranged from satisfactory to excellent fit. Conclusion: Despite the lack of clinical trials that provide strong evidence, the available evidence supported the claim of good fit of RPDs fabricated by new technologies using CAD/CAM.

  1. Assessment of the fit of removable partial denture fabricated by computer-aided designing/computer aided manufacturing technology.

    Science.gov (United States)

    Arafa, Khalid A O

    2018-01-01

    To assess the level of evidence that supports the quality of fit for removable partial denture (RPD) fabricated by computer-aided designing/computer aided manufacturing (CAD/CAM) and rapid prototyping (RP) technology. Methods: An electronic search was performed in Google Scholar, PubMed, and Cochrane library search engines, using Boolean operators. All articles published in English and published in the period from 1950 until April 2017 were eligible to be included in this review. The total number of articles contained the search terms in any part of the article (including titles, abstracts, or article texts) were screened, which resulted in 214 articles. After exclusion of irrelevant and duplicated articles, 12 papers were included in this systematic review.  Results: All the included studies were case reports, except one study, which was a case series that recruited 10 study participants. The visual and tactile examination in the cast or clinically in the patient's mouth was the most-used method for assessment of the fit of RPDs. From all included studies, only one has assessed the internal fit between RPDs and oral tissues using silicone registration material. The vast majority of included studies found that the fit of RPDs ranged from satisfactory to excellent fit. Conclusion: Despite the lack of clinical trials that provide strong evidence, the available evidence supported the claim of good fit of RPDs fabricated by new technologies using CAD/CAM.

  2. [A preliminary study on the forming quality of titanium alloy removable partial denture frameworks fabricated by selective laser melting].

    Science.gov (United States)

    Liu, Y F; Yu, H; Wang, W N; Gao, B

    2017-06-09

    Objective: To evaluate the processing accuracy, internal quality and suitability of the titanium alloy frameworks of removable partial denture (RPD) fabricated by selective laser melting (SLM) technique, and to provide reference for clinical application. Methods: The plaster model of one clinical patient was used as the working model, and was scanned and reconstructed into a digital working model. A RPD framework was designed on it. Then, eight corresponding RPD frameworks were fabricated using SLM technique. Three-dimensional (3D) optical scanner was used to scan and obtain the 3D data of the frameworks and the data was compared with the original computer aided design (CAD) model to evaluate their processing precision. The traditional casting pure titanium frameworks was used as the control group, and the internal quality was analyzed by X-ray examination. Finally, the fitness of the frameworks was examined on the plaster model. Results: The overall average deviation of the titanium alloy RPD framework fabricated by SLM technology was (0.089±0.076) mm, the root mean square error was 0.103 mm. No visible pores, cracks and other internal defects was detected in the frameworks. The framework fits on the plaster model completely, and its tissue surface fitted on the plaster model well. There was no obvious movement. Conclusions: The titanium alloy RPD framework fabricated by SLM technology is of good quality.

  3. Hexavalent Chromium Compounds

    Science.gov (United States)

    Learn about chromium, exposure to which can increase your risk of lung cancer and cancer of the paranasal sinuses and nasal cavity. Hexavalent chromium compounds have been used as corrosion inhibitors in a wide variety of products and processes.

  4. The analysis of the mechanical properties of F75 Co-Cr alloy for use in selective laser melting (SLM manufacturing of removable partial dentures (RPD

    Directory of Open Access Journals (Sweden)

    D. Jevremovic

    2012-04-01

    Full Text Available The presented work discusses the applicability of the selective laser melting technique (SLM in manufacture of removable partial denture (RPD frameworks with the emphasis on material properties. The paper presents initial results of a conducted test of the mechanical properties of the F75 Co-Cr dental alloy used with selective laser melting.

  5. Determination of tracer quantities of chromium in uranium

    International Nuclear Information System (INIS)

    Huart, A.

    1959-01-01

    A method is described for the photometric determination of chromium in uranium by absorbency at 540 mμ of the Cr(VI) diphenylcarbazide combination. After attack by nitric acid, the solution is made perchloric, and the chromium oxidised at the boiling point by permanganate. Excess oxidant is removed by hydrochloric acid. Study of operating conditions resulted in a method with an accuracy of ± 0,5 ppm for 0,5 to 15 ppm chromium in the metal. (author) [fr

  6. [Dual insertion paths design characteristics and short-term clinical observation of rotational path removable partial dentures].

    Science.gov (United States)

    Li, Jian; Jiang, Ting; Li, Sai; Chen, Wei

    2013-02-18

    To investigate design methods of dual insertion paths and observe a short-term clinic overview of rotational path removable partial dentures (RPDs). In the study, 40 patients with partial edentulous arches were included and divided into two groups. The patients in group one were restored with rotational path RPDs (10 Kennedy class III and 10 Kennedy class IV respectively). The patients in group two (20 patients), whose edentulous area was matched with the patients' in group one, were restored with the linear path RPDs. After surveying and simulative preparation on diagnostic casts, the basic laws of designing rotational path RPDs were summarized. The oral preparation was accurately performed under the guidance of indices made on diagnostic casts after simulative preparation. The 40 dentures were recalled two weeks and one year after the insertion. The evaluations of the clinic outcome, including retention, stability, mastication function, esthetics and wearing convenience, were marked out as good, acceptable, and poor. The comparison of the evaluation results was performed between the two groups. In the rotational path design for Kennedy class III or IV RPDs, the angles (α) of dual insertion paths should be designed within a scope, approximate 10°-15°.When the angle (α) became larger, the denture retention turned to be better, but accordingly the posterior abutments needed more preparation. In the clinical application, the first insertions of the 40 dentures were all favorably accomplished. When the rotational path RPDs were compared to linear path RPDs, the time consuming on first insertion had no statistical difference[(32±8) min and (33±8) min respectively, P>0.05]. Recalled two weeks and one year after the insertion, in the esthetics evaluation, 20 rotational path RPDs were all evaluated as "A", but only 7(two weeks after) and 6 (one year after) linear path RPDs were evaluated as "A"(P<0.05). There was no significant difference in other evaluation results

  7. Veneered zirconia crowns as abutment teeth for partial removable dental prostheses: a clinical 4-year retrospective study.

    Science.gov (United States)

    Pihlaja, Juha; Näpänkangas, Ritva; Kuoppala, Ritva; Raustia, Aune

    2015-11-01

    The mechanical properties of zirconia suggest that it might serve as a material for abutment crowns for partial removable dental prostheses (RDPs). Only limited clinical evidence is available for the use of ceramics as abutment crowns. The purpose of this retrospective clinical study was to evaluate the outcome of veneered zirconia single crowns in abutment teeth for RPDs in participants treated by predoctoral students. Thirty-seven veneered zirconia single crowns in 17 participants (9 men and 8 women; mean age 62.5 years) were prepared as abutment teeth for a clasp-retained RDP with a metal framework: 22 crowns with an occlusal rest seat and 15 crowns with both an occlusal rest seat and retentive clasps. The mean follow-up time was 4.2 years (2.9 to 5.4 years). In a clinical examination, the anatomic form of the crown, marginal fidelity (the border between the crown and the tooth was felt with an explorer), wear of the ceramic surface in the rest seat, and fracture of the veneering porcelain were examined and assessed as good, acceptable, or unacceptable. The retention and stability of the RDPs were recorded as good, moderate, or poor. The complications found were fracture of the veneering porcelain (11%) and fracture of the occlusal rest seat (3%). Wear of porcelain at the occlusal contact point was found in 24% of the zirconia single crowns. Wear of the ceramic surfaces of the rest seats for the RDPs was not found. The retention was good in all RDPs. The stability was good in 73% and moderate in 23% of the RDPs. Veneered zirconia single crowns are suitable in abutment teeth for RDPs with a metal framework. Fracture in the veneering porcelain remains a problem with veneered zirconia, although the zirconia surface in the rest seats for RDPs showed no wear. Copyright © 2015 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

  8. Shape Optimization for Additive Manufacturing of Removable Partial Dentures--A New Paradigm for Prosthetic CAD/CAM.

    Science.gov (United States)

    Chen, Junning; Ahmad, Rohana; Suenaga, Hanako; Li, Wei; Sasaki, Keiichi; Swain, Michael; Li, Qing

    2015-01-01

    With ever-growing aging population and demand for denture treatments, pressure-induced mucosa lesion and residual ridge resorption remain main sources of clinical complications. Conventional denture design and fabrication are challenged for its labor and experience intensity, urgently necessitating an automatic procedure. This study aims to develop a fully automatic procedure enabling shape optimization and additive manufacturing of removable partial dentures (RPD), to maximize the uniformity of contact pressure distribution on the mucosa, thereby reducing associated clinical complications. A 3D heterogeneous finite element (FE) model was constructed from CT scan, and the critical tissue of mucosa was modeled as a hyperelastic material from in vivo clinical data. A contact shape optimization algorithm was developed based on the bi-directional evolutionary structural optimization (BESO) technique. Both initial and optimized dentures were prototyped by 3D printing technology and evaluated with in vitro tests. Through the optimization, the peak contact pressure was reduced by 70%, and the uniformity was improved by 63%. In vitro tests verified the effectiveness of this procedure, and the hydrostatic pressure induced in the mucosa is well below clinical pressure-pain thresholds (PPT), potentially lessening risk of residual ridge resorption. This proposed computational optimization and additive fabrication procedure provides a novel method for fast denture design and adjustment at low cost, with quantitative guidelines and computer aided design and manufacturing (CAD/CAM) for a specific patient. The integration of digitalized modeling, computational optimization, and free-form fabrication enables more efficient clinical adaptation. The customized optimal denture design is expected to minimize pain/discomfort and potentially reduce long-term residual ridge resorption.

  9. Oral health-related quality of life in patients treated by implant-supported fixed dentures and removable partial dentures.

    Science.gov (United States)

    Furuyama, Chisako; Takaba, Masayuki; Inukai, Mika; Mulligan, Roseann; Igarashi, Yoshimasa; Baba, Kazuyoshi

    2012-08-01

    This study investigated the association between denture status [implant-supported fixed dentures (IDs) and removable partial dentures (RPDs)] and oral health-related quality of life (OHRQoL). Consecutive patients with IDs and RPDs were recruited from the Prosthodontics Departments at Showa University and Tokyo Medical and Dental University. The Japanese version of the Oral Health Impact Profile (OHIP-J-49) was administered to each subject. For each OHIP-J-49 question, the subjects were asked to indicate the frequency with which they had experienced a dental problem during the last month. Responses were recorded on a 5 point Likert rating scale, with 0 being never and 4, very often. Summary scores were calculated and regression analyses conducted to investigate the association between denture status and OHIP-J-49 summary score. In total 79 ID subjects (mean age±SD of 51.7±12.4 years, 44.3% men) and 109 RPD subjects (mean age of 66.5±8.6 years, 30% men) participated after giving informed consent. The regression analysis between the type of treatment and the OHIP-J-49 summary score revealed a significant association with a coefficient of 17.0 (Confidence interval, CI: 10.9-23.1). When age and duration of denture usage, which had significant associations with OHIP-J-49, were included in this model, the regression coefficient remained virtually unchanged at 17.4 (CI: 9.75-25.0), thus indicating little potential confounding by them. OHRQoL in patients with implant-supported fixed dentures is generally less impaired than it is in those patients with RPDs. © 2011 John Wiley & Sons A/S.

  10. Periodontal Conditions of Abutments and Non-Abutments in Removable Partial Dentures over 7 Years of Use.

    Science.gov (United States)

    da Fonte Porto Carreiro, Adriana; de Carvalho Dias, Kássia; Correia Lopes, Ana Lílian; Bastos Machado Resende, Camila Maria; Luz de Aquino Martins, Ana Rafaela

    2017-12-01

    To evaluate the periodontal conditions and integrity of abutment and non-abutment teeth of patients evaluated 7 years after insertion of the removable partial denture (RPD). Twenty-two patients (17 women, 5 men) were assessed at the moment of denture insertion and 7 years later. The following items were verified in each assessment: bleeding on probing (BP), probing depth (PD), gingival recession (GR), and mobility (M), comparing direct and indirect abutment teeth, and the teeth not involved in the denture design. Tooth integrity was also evaluated and classified as intact when no caries or fractures were observed. The Kruskal-Wallis test was used to reveal statistical significance between the groups (p = 0.05) as well as the Bonferrroni-corrected Mann-Whitney test for post hoc comparison. The Wilcoxon test was used for evaluation within the group over time. Fisher's exact test was applied to cross data about abutment integrity. Statistically significant differences were found for GR (baseline, p < 0.001; 7 years, p < 0.001) and PD (baseline, p = 0.001; 7 years = 0.004) between the three groups at baseline and after 7 years of follow-up. Mean BP and M values increased from initial assessment to after 7 years of RPD use in every group, but no statistically significant difference was found between the groups. For abutment integrity, a statistically significant difference (p = 0.028) was observed, and the direct abutment exhibited more (33.3%) caries and fractures. RPDs generated more periodontal damage to direct abutments, since higher gingival recession probing depth indexes, and presence of caries and fractures were observed in comparison to indirect abutments and non-abutments. © 2016 by the American College of Prosthodontists.

  11. Three Dimensional Finite Element Analysis of Distal Abutment Stresses of Removable Partial Dentures with Different Retainer Designs

    Directory of Open Access Journals (Sweden)

    Simindokht Zarrati

    2015-11-01

    Full Text Available Objectives: This finite element method study aimed to compare the amount of stress on an isolated mandibular second premolar in two conventional reciprocal parallel interface designs of removable partial dentures (RPDs and the same RPD abutment tooth (not isolated.Materials and Methods: A Kennedy Class 1, modification 1 RPD framework was simulated on a 3D model of mandible with three different designs: an isolated tooth with a mesial rest, an isolated tooth with mesial and distal rests and an abutment with a mesial rest (which was not isolated; 26 N occlusal forces were exerted bilaterally on the first molar sites. Stress on the abutment teeth was analyzed using Cosmos Works 2009 Software.Results: In all designs, the abutment tooth stress concentration was located in the buccal alveolar crest. In the first model, the von Mises stress distribution in the contact area of I-bar clasp and cervical portion of the tooth was 19 MPa and the maximum stress was 30 MPa. In the second model, the maximum von Mises stress distribution was 15 MPa in the cervical of the tooth. In the third model, the maximum von Mises stress was located in the cervical of the tooth and the distal proximal plate.Conclusion: We recommend using both mesial and distal rests on the distal abutment teeth of distal extension RPDs. The abutment of an extension base RPD, which is not isolated in presence of its neighboring more anterior tooth, may have a better biomechanical prognosis.      

  12. Shape Optimization for Additive Manufacturing of Removable Partial Dentures - A New Paradigm for Prosthetic CAD/CAM

    Science.gov (United States)

    2015-01-01

    With ever-growing aging population and demand for denture treatments, pressure-induced mucosa lesion and residual ridge resorption remain main sources of clinical complications. Conventional denture design and fabrication are challenged for its labor and experience intensity, urgently necessitating an automatic procedure. This study aims to develop a fully automatic procedure enabling shape optimization and additive manufacturing of removable partial dentures (RPD), to maximize the uniformity of contact pressure distribution on the mucosa, thereby reducing associated clinical complications. A 3D heterogeneous finite element (FE) model was constructed from CT scan, and the critical tissue of mucosa was modeled as a hyperelastic material from in vivo clinical data. A contact shape optimization algorithm was developed based on the bi-directional evolutionary structural optimization (BESO) technique. Both initial and optimized dentures were prototyped by 3D printing technology and evaluated with in vitro tests. Through the optimization, the peak contact pressure was reduced by 70%, and the uniformity was improved by 63%. In vitro tests verified the effectiveness of this procedure, and the hydrostatic pressure induced in the mucosa is well below clinical pressure-pain thresholds (PPT), potentially lessening risk of residual ridge resorption. This proposed computational optimization and additive fabrication procedure provides a novel method for fast denture design and adjustment at low cost, with quantitative guidelines and computer aided design and manufacturing (CAD/CAM) for a specific patient. The integration of digitalized modeling, computational optimization, and free-form fabrication enables more efficient clinical adaptation. The customized optimal denture design is expected to minimize pain/discomfort and potentially reduce long-term residual ridge resorption. PMID:26161878

  13. Shape Optimization for Additive Manufacturing of Removable Partial Dentures--A New Paradigm for Prosthetic CAD/CAM.

    Directory of Open Access Journals (Sweden)

    Junning Chen

    Full Text Available With ever-growing aging population and demand for denture treatments, pressure-induced mucosa lesion and residual ridge resorption remain main sources of clinical complications. Conventional denture design and fabrication are challenged for its labor and experience intensity, urgently necessitating an automatic procedure. This study aims to develop a fully automatic procedure enabling shape optimization and additive manufacturing of removable partial dentures (RPD, to maximize the uniformity of contact pressure distribution on the mucosa, thereby reducing associated clinical complications. A 3D heterogeneous finite element (FE model was constructed from CT scan, and the critical tissue of mucosa was modeled as a hyperelastic material from in vivo clinical data. A contact shape optimization algorithm was developed based on the bi-directional evolutionary structural optimization (BESO technique. Both initial and optimized dentures were prototyped by 3D printing technology and evaluated with in vitro tests. Through the optimization, the peak contact pressure was reduced by 70%, and the uniformity was improved by 63%. In vitro tests verified the effectiveness of this procedure, and the hydrostatic pressure induced in the mucosa is well below clinical pressure-pain thresholds (PPT, potentially lessening risk of residual ridge resorption. This proposed computational optimization and additive fabrication procedure provides a novel method for fast denture design and adjustment at low cost, with quantitative guidelines and computer aided design and manufacturing (CAD/CAM for a specific patient. The integration of digitalized modeling, computational optimization, and free-form fabrication enables more efficient clinical adaptation. The customized optimal denture design is expected to minimize pain/discomfort and potentially reduce long-term residual ridge resorption.

  14. Synthesis of chitosan/polyvinyl alcohol/zeolite composite for removal of methyl orange, Congo red and chromium(VI) by flocculation/adsorption.

    Science.gov (United States)

    Habiba, Umma; Siddique, Tawsif A; Joo, Tan Chin; Salleh, Areisman; Ang, Bee Chin; Afifi, Amalina M

    2017-02-10

    A chitosan/polyvinyl alcohol (PVA)/zeolite composite was fabricated in this study. The composite was analyzed through field emission scanning electron microscopy, Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), thermogravimetric analysis, and weight loss test. FTIR and XRD results revealed a strong interaction among chitosan, PVA, and zeolite. Weight loss test results indicated that the composite was stable in acidic and basic media. Congo red was removed through flocculation, and the removal rate was 94% at an initial concentration of 100mg/L for a dose of 1g/L. The removal rate of methyl orange was controlled by adsorption at an initial concentration of less than 100mg/L. Flocculation occurred at high concentrations. The removal rate was also 94% at an initial concentration of 500mg/L for a dose of 5g/L. The adsorption behavior of the composite for the removal of methyl orange and Cr(VI) was described by using a pseudo-second-order kinetic model. The adsorption capacity of the composite for Cr(VI) was 450mg/g. Therefore, the synthesized composite exhibited versatility during the removal of dyes and heavy metals. Copyright © 2016 Elsevier Ltd. All rights reserved.

  15. remediation potential of Eichornia sp in conjunction with chromium

    African Journals Online (AJOL)

    Purpose: Evaluation of Cr (VI) removal by indigenous chromium resistant bacterial strains alone and in ... Chromium (Cr) is one of the toxic heavy metals ... membranes, ion exchange resins and reverse osmosis [3]. These expensive methodologies generate toxic by-products, so ecologically cost effective methods are ...

  16. Biosorption of chromium by mangrove-derived Aplanochytrium sp ...

    African Journals Online (AJOL)

    The microbial dried biomass of Thraustochytrids is used as bioadsorbent for the removal of the chromium in aqueous solution. In this investigation, three species of Thraustochydrids namely Aplanochytrium sp., Thraustochytrium sp. and Schizochytrium sp. were tested for the efficiency of chromium accumulation by culturing ...

  17. Influence of Implant Position on Stress Distribution in Implant-Assisted Distal Extension Removable Partial Dentures: A 3D Finite Element Analysis.

    Directory of Open Access Journals (Sweden)

    Yeganeh Memari

    2014-10-01

    Full Text Available Distal extension removable partial denture is a prosthesis with lack of distal dental support with a 13-fold difference in resiliency between the mucosa and the periodontal ligament, resulting in leverage during compression forces. It may be potentially destructive to the abutments and the surrounding tissues. The aim of this study was to assess the effect of implant location on stress distribution, in distal extension implant assisted removable partial dentures.Three-dimensional models of a bilateral distal extension partially edentulous mandible containing anterior teeth and first premolar in both sides of the arch, a partial removable denture and an implant (4×10mm were designed. With the aid of the finite element program ANSYS 8.0, the models were meshed and strictly vertical forces of 10 N were applied to each cusp tip. Displacement and von Mises Maps were plotted for visualization of results.When an implant was placed in the second premolar region, the highest stress on implant, abutment tooth and cancellous bone was shown. The lowest stress was shown on implant and bone in the 1(st molar area.Implants located in the first molar area showed the least distribution of stresses in the analyzed models.

  18. Influence of Implant Position on Stress Distribution in Implant-Assisted Distal Extension Removable Partial Dentures: A 3D Finite Element Analysis.

    Science.gov (United States)

    Memari, Yeganeh; Geramy, Allahyar; Fayaz, Amir; Rezvani Habib Abadi, Shirin; Mansouri, Yasaman

    2014-09-01

    Distal extension removable partial denture is a prosthesis with lack of distal dental support with a 13-fold difference in resiliency between the mucosa and the periodontal ligament, resulting in leverage during compression forces. It may be potentially destructive to the abutments and the surrounding tissues. The aim of this study was to assess the effect of implant location on stress distribution, in distal extension implant assisted removable partial dentures. Three-dimensional models of a bilateral distal extension partially edentulous mandible containing anterior teeth and first premolar in both sides of the arch, a partial removable denture and an implant (4×10mm) were designed. With the aid of the finite element program ANSYS 8.0, the models were meshed and strictly vertical forces of 10 N were applied to each cusp tip. Displacement and von Mises Maps were plotted for visualization of results. When an implant was placed in the second premolar region, the highest stress on implant, abutment tooth and cancellous bone was shown. The lowest stress was shown on implant and bone in the 1(st) molar area. Implants located in the first molar area showed the least distribution of stresses in the analyzed models.

  19. Application of Central Composite Design approach for removal of chromium (VI) from aqueous solution using weakly anionic resin: modeling, optimization, and study of interactive variables.

    Science.gov (United States)

    Bajpai, Shailendra; Gupta, S K; Dey, Apurba; Jha, M K; Bajpai, Vidushi; Joshi, Saurabh; Gupta, Arvind

    2012-08-15

    In this paper, response surface methodology (RSM) approach using Central Composite Design (CCD) is applied to develop mathematical model and optimize process parameters for Cr (VI) removal from aqueous streams using weakly anionic resin Amberlite IRA 96. The individual and combined effect of four process parameters, i.e. contact time, initial solution pH, initial Cr (VI) concentration and resin dose on Cr adsorption were studied. Analysis of variance (ANOVA) showed the relative significance of process parameters in removal process. Initial solution pH and resin dose were found to be more significant than contact time and initial Cr (VI) concentration. The second-order regression model was developed to predict the removal efficiency using Design Expert software. The optimal conditions to remove Cr from aqueous solution at constant temperature of 30°C and stirring speed of 250 rpm were found to be contact time 62.5 min, pH 1.96, initial Cr (VI) concentration 145.4 mg/L, and resin dose 8.51 g/L. At these conditions, high removal efficiency (93.26%) was achieved. FTIR and EDX analysis were conducted to interpret the functional groups involved during the Cr-resin interaction. Copyright © 2012 Elsevier B.V. All rights reserved.

  20. In Situ Removal of Cadmium and Chromium from Groundwater Using ZeoTech Reactive Barriers. Final Report for period October 1999-April 2000.

    Energy Technology Data Exchange (ETDEWEB)

    Rostami, H.; Silverstrim, T.

    2000-05-01

    The use of novel permeable reactive barrier (PRB) to remove and to stabilize heavy metals such as Cd and Cr from groundwater was studied. The barrier was made of fly ash, an appropriate material for high volume ion exchange. The fly ash is combined with chemicals to create activated ash material or AAM. PRB's, made from activated fly ash, AAM-PRB's, were used to treat contaminated water in situ. It was shown that the AAM-PRB was effective in removal of Cd and Cr from contaminated water, while at the same time utilizing waste fly ash that otherwise would be have to be landfilled.

  1. High-performance towards removal of toxic hexavalent chromium from aqueous solution using graphene oxide-alpha cyclodextrin-polypyrrole nanocomposites

    CSIR Research Space (South Africa)

    Chauke, VP

    2015-07-01

    Full Text Available Graphene oxide (GO) was functionalized with alpha cyclodextrin (aCD) through a covalent bond to form GO-aCD nanocomposites (NC). GO-aCD NC was further modified with polypyrrole (PPY) to afford an advanced GO-aCD-PPY NC for the removal of highly...

  2. Simultaneous preconcentration and removal of iron, chromium, nickel with N,N'-etylenebis-(ethane sulfonamide) ligand on activated carbon in aqueous solution and determination by ICP-OES.

    Science.gov (United States)

    Karacan, Mehmet Sayim; Aslantaş, Neslihan

    2008-07-15

    In this study, Fe, Cr and Ni have been preconcentrated and removed by using N,N'-ethylenebis (ethane sulfonamide), (ESEN) ligand on activated carbon (AC) in aqueous solution. For this purpose, complexes between these metals and ligands have been investigated and used in preconcentration and removal studies. Factors which have affected adsorption of metals on activated carbon have been optimized. Adsorbed metals have been preconcentrated 10-fold and determined by ICP-OES. Interferences of Ca, Mg and K to this process have been investigated. The proposed method has been applied to the tap water and Ankara Creek water in order to Fe, Cr, and Ni remediation and preconcentration. Determination of metals by ICP-OES has been checked with standard reference material (NIST 1643e). The proposed method provides the recoveries of 87%, 108% and 106% for Fe, Cr and Ni, respectively, in preconcentration. It also provides the removal of Fe, Cr and Ni by 93%, 100% and 100% removal from waters, respectively.

  3. Prospective clinical study of prosthetic treatment outcome of implantretained-removable-partial-denture during 5 year-follow-ups

    Directory of Open Access Journals (Sweden)

    Mehran Bahrami

    2017-11-01

    Full Text Available Background IRRPD offers patients the ability to upgrade their treatment planning to implant-supported-overdentures (ISOs or implant-supported-fixed-prostheses (ISFPs through insertion of more implants in the future after the loss of the remaining natural teeth. Aims The purpose of this prospective-clinical-study was to evaluate the success rate and treatment outcome of IRRPD for 15 patients, during at least 5-year-follow-ups after prosthetic rehabilitation with respect to implant mobility, peri-implant-marginal-bone-levels, and prosthetic complications. Methods 15 successive patients were attended the Department of Implantology and Prosthodontics in TUMS, and received Implant-Retained-Removable-Partial-Dentures (IRRPDs. Two standard-size-dental-implants (Implantium/Dentium system, internal hexagon, Seoul, South Korea were placed in distal-extension-areas for each patient. After the osseointegration period, all patients received IRRPDs using two Ball attachments. All the participated patients were followed-up at least for 5 years, and the survival rate of 30 implants was evaluated. The patients’ satisfaction of function, phonetics, and aesthetics was assessed by means of questionnaire. Results None of the studied patients reported any prosthetic complications during the follow-up-periods such as attachment loosening, metal housing loosening, or denture fracture. No implants failure was recorded, so that the cumulative-implant-survival rate was 100 per cent. The mean marginal-bone-resorption (MBR around the two implants was 0.9mm with a range of 0.5–1.4mm. Teeth aesthetics was judged as excellent or very good by 86.7 per cent of the patients, while phonetics and mastication were considered excellent or very good by 66.7 per cent and 73.3 per cent of the patients, respectively. Conclusion 15 patients received 30 implants for the fabrication of IRRPDs in the posterior-edentulous-sites. The IRRPDs were delivered to the patients by the same

  4. Fabrication of a Customized Ball Abutment to Correct a Nonparallel Implant Abutment for a Mandibular Implant-Supported Removable Partial Prosthesis: A Case Report

    Directory of Open Access Journals (Sweden)

    Hossein Dasht

    2017-12-01

    Full Text Available Introduction: While using an implant-supported removable partial prosthesis, the implant abutments should be parallel to one another along the path of insertion. If the implants and their attachments are placed vertically on a similar occlusal plane, not only is the retention improved, the prosthesis will also be maintained for a longer period. Case Report: A 65-year-old male patient referred to the School of Dentistry in Mashhad, Iran with complaints of discomfort with the removable partial dentures for his lower mandible. Due to the lack of parallelism in the supporting implants, prefabricated ball abutment could not be used. As a result, a customized ball abutment was fabricated in order to correct the non-parallelism of the implants. Conclusion: Using UCLA abutments could be a cost-efficient approach for the correction of misaligned implant abutments in implant-supported overdentures.

  5. Method for welding chromium molybdenum steels

    Science.gov (United States)

    Sikka, Vinod K.

    1986-01-01

    Chromium-molybdenum steels exhibit a weakening after welding in an area adjacent to the weld. This invention is an improved method for welding to eliminate the weakness by subjecting normalized steel to a partial temper prior to welding and subsequently fully tempering the welded article for optimum strength and ductility.

  6. Biosorption of hexavalent chromium in a tannery industry wastewater using fungi species

    OpenAIRE

    D. Sivakumar

    2016-01-01

    The isolated fungi species of different kinds from chromium contaminated soil sites located in Nagalkeni, Chennai were used for reducing chromium(VI) in a tannery industry wastewater of Nagalkeni, Chennai.  The experiments were conducted to know biosorption potential of isolated fungi species for removing chromium(VI) in a tannery industry wastewater against the different pH, fungi biomass and chromium(VI) concentration (dilution ratio).  The results of this study indicated that the order of ...

  7. One-step partial or complete caries removal and bonding with antibacterial or traditional self-etch adhesives: study protocol for a randomized controlled trial.

    Science.gov (United States)

    Villat, Cyril; Attal, Jean-Pierre; Brulat, Nathalie; Decup, Franck; Doméjean, Sophie; Dursun, Elisabeth; Fron-Chabouis, Hélène; Jacquot, Bruno; Muller Bolla, Michèle; Plasse-Pradelle, Nelly; Roche, Laurent; Maucort-Boulch, Delphine; Nony, Patrice; Gritsch, Kerstin; Millet, Pierre; Gueyffier, François; Grosgogeat, Brigitte

    2016-08-15

    Current concepts in conservative dentistry advocate minimally invasive dentistry and pulp vitality preservation. Moreover, complete removal of carious dentin in deep carious lesions often leads to pulp exposure and root canal treatment, despite the absence of irreversible pulp inflammation. For years, partial caries removal has been performed on primary teeth, but little evidence supports its effectiveness for permanent teeth. Furthermore, the recent development of new antibacterial adhesive systems could be interesting in the treatment of such lesions. The objectives of this study are to compare the effectiveness of partial versus complete carious dentin removal in deep lesions (primary objective) and the use of an antibacterial versus a traditional two-step self-etch adhesive system (main secondary objective). The DEep CAries Treatment (DECAT) study protocol is a multicenter, randomized, controlled superiority trial comparing partial versus complete caries removal followed by adhesive restoration. The minimum sample size required is 464 patients. Two successive randomizations will be performed (allocation ratio 1:1): the first for the type of excavation (partial versus complete) and the second (if no root canal treatment is required) for the type of adhesive (antibacterial versus traditional). For the two objectives, the outcome is the success of the treatment after 1 year, measured according to a composite outcome of five FDI criteria: material fracture and retention, marginal adaptation, radiographic examination (including apical pathologies), postoperative sensitivity and tooth vitality, and carious lesion recurrence. The study will investigate the interest of a conservative approach for the management of deep carious lesions in terms of dentin excavation and bioactive adhesive systems. The results may help practitioners achieve the most efficient restorative procedure to maintain pulp vitality and increase the restoration longevity. Clinical

  8. Rapid start-up of partial nitritation and simultaneously phosphorus removal (PNSPR) granular sludge reactor treating low-strength domestic sewage.

    Science.gov (United States)

    Zhang, Jianhua; Zhang, Qiong; Li, Xiyao; Miao, Yuanyuan; Sun, Yawen; Zhang, Miao; Peng, Yongzhen

    2017-11-01

    Obtaining desirable partial nitritation (PN) is crucial for successful application of the combined PN and anammox process. In this study, the partial nitritation and simultaneously phosphorus removal (PNSPR) 1 granular sludge reactor treating low-strength domestic sewage was rapidly started up in 67days through seeding denitrifying phosphorus removal (DPR) 2 sludge. The nitrite/ammonium ratio in effluent was approximately 1 and the nitrite accumulation rate (NAR) was more than 95%, about 93% of orthophosphate was removed. The DPR sludge rich in phosphate accumulating organisms (PAOs) with few nitrifying bacteria could promote the achievement of PNSPR. Quantitative microbial analysis showed that the ammonium oxidizing bacteria (AOB) gene ratio in sludge increased from 0.21% to 3.43%, while nitrite oxidizing bacteria (NOB) gradually decreased to 0.07%. The average particle size of sludge increased from 114 to 421μm, indicating the formation of PNSPR granules. The high phosphorus content in sludge and phosphorus removal facilitated rapid granulation. Copyright © 2017 Elsevier Ltd. All rights reserved.

  9. Simultaneous anaerobic oxidation/partial nitrification-denitrification for cost-effective and efficient removal of organic carbon and nitrogen from highly polluted streams.

    Science.gov (United States)

    Hosseinlou, Daniel; Sartaj, Majid; Delatolla, Robert

    2018-02-15

    Laboratory bench-scale anoxic/aerobic reactors with complete mix and continuous flow conditions were operated with high-strength synthetic wastewater to achieve simultaneous COD and nitrogen removal. High concentrations of organic carbon and nitrogen can be found in slaughterhouse, dairy, and food processing wastewaters, and also in some landfill leachates. Therefore, the goal of this study is to find a simple, efficient, reliable, cost-effective, and general solution for organic carbon and ammonia removal from streams with high influent concentrations of more than 5000 mg/L COD and 250 mg/L NH 3 -N. The highest COD (97%) and NH 3 -N (91%) removal efficiencies were obtained with initial COD and ammonia concentrations of 5211 mg/L and 262.8 mg/L NH 3 -N with volumetric loading rates of 11.26 kg COD/m 3  d and 0.57 kg NH 3 -N/m 3  d for COD and ammonia, respectively. Anaerobic oxidation is the main COD removal pathway in a simultaneous anaerobic oxidation/partial nitrification-denitrification (SAO/PND) system, and nitrogen removal significantly occurs via bacterial assimilation and partial nitrification-denitrification pathways. There are several advantages for this proposed SAO/PND system from a practical point of view, such as feasibility of simultaneous COD and nitrogen removal in a single reactor; simple operation; flexibility and practicality of this system as a general solution and cost effectiveness.

  10. A simple route to synthesize conductive stimuli-responsive polypyrrole nanocomposite hydrogel particles with strong magnetic properties and their performance for removal of hexavalent chromium ions from aqueous solution

    Science.gov (United States)

    Ahmad, Hasan; Rahman, Mohammad Mostafizar; Ali, Mohammad Azgar; Minami, Hideto; Tauer, Klaus; Gafur, Mohammad Abdul; Rahman, Mohammad Mahbubor

    2016-08-01

    A combination of maghemite polypyrrole (PPy/γ-Fe2O3) and stimuli-responsive properties in the same hydrogel microspheres is expected to enhance their application potential in various fields such as tissue engineering, regenerative medicine, biosensors, biomedical applications and removal of heavy metals from waste water, catalysis etc. In this investigation a simple two step process is used to prepare conductive stimuli-responsive polypyrrole (PPy) composite hydrogel particles with strong magnetic properties. Poly(styrene-methacrylic acid-N-isopropylacrylamide-polyethelene glycol methacrylate) or P(S-NIPAM-MAA-PEGMA) hydrogel seed particles are first prepared by soap-free precipitation copolymerization. The copolymer hydrogel particles exhibited both temperature- and pH-responsive volume phase transition. Conductive P(S-NIPAM-MAA-PEGMA)/PPy/γ-Fe2O3 nanocomposite hydrogel particles are then prepared by seeded chemical oxidative polymerization of pyrrole in the presence of P(S-NIPAM-MAA-PEGMA) hydrogel seed particles using FeCl3 as a oxidant and p-toluene sulfonic acid (p-TSA) as a dopant. In the reaction system FeCl3 functioned as a source of Fe(III) for the formation of γ-Fe2O3. This reaction also requires the initial presence of Fe(II) provided by the addition of FeCl2. The size and size distribution, surface structure, and morphology of the prepared conductive composite hydrogel particles are confirmed by FTIR, electron micrographs, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and UV-visible spectroscopy. The performance of nanocomposite hydrogel particles has been evaluated for the removal of hexavalent chromium (Cr) ions from water.

  11. A REVIEW OF BIOSORPTION OF CHROMIUM IONS BY MICROORGANISMS

    Directory of Open Access Journals (Sweden)

    Inga Zinicovscaia

    2012-12-01

    Full Text Available Due to its widespread industrial use, chromium has become a serious pollutant in diverse environmental settings. The main source of chromium pollution including the Republic o Moldova is industry. It is a great need to develop new eco-friendly methods of chromium removal. Biosorption of heavy metals is a most promising technology involved in the removal of toxic metals from industrial waste streams and natural waters. This article is an extended abstract of a communication presented at the Conference Ecological Chemistry 2012

  12. Chromium in diet

    Science.gov (United States)

    ... is important in the metabolism of fats and carbohydrates . It stimulates fatty acid and cholesterol synthesis, which are important for brain function and other body processes. Chromium also aids in insulin action and glucose metabolism. Food Sources The best source of chromium is brewer's yeast. ...

  13. Effect of the number of implants on stress distribution of anterior implant-supported fixed prostheses combined with a removable partial denture: a finite element analysis.

    Directory of Open Access Journals (Sweden)

    Minoo Mahshid

    2014-06-01

    Full Text Available The main goal of this study was to evaluate differences in stress distribution relevant to the number of implants under an anterior bridge when combined with a removable partial denture in the posterior region.Four three-dimensional finite element models (3D FEM were designed from a mandible containing an implant-supported bridge extending between canines, and a bilateral distal extension removable partial denture. A nonrigid connection was selected as the attachment method between the partial denture and the anterior implant-supported fixed prosthesis; 2, 3, 4 and 5 implants supporting the bridge all with 10mm length and 3.8 mm diameter were assessed. With the aid of the finite element program ANSYS 8.0, the models were loaded and von Mises stresses were evaluated.In spongy bone, stress forces showed a decrease from 2 implants to 4 implants but showed an increase in the 5-implant model. Stresses on cortical bone of terminal implants were in similar range in the 2-, 3- and 4-implant models. While, in the 5-implant model the amount of stresses on terminal implants increased dramatically. The stresses on implants were nearly similar in all models, with the greatest amount on terminal implants.Within the limitations of this study, 2-, 3- and 4-implant models showed less stress on cortical and spongy bone in comparison with the 5-implant model. The stresses transferred to implants were nearly similar.

  14. Prosthetic rehabilitation of mandibular defects with fixed-removable partial denture prosthesis using precision attachment: A twin case report

    Directory of Open Access Journals (Sweden)

    Vimal Kantilal Munot

    2017-01-01

    Full Text Available The restoration of normal function and esthetic appearance with a dental prosthesis is a major challenge in the rehabilitation of patients who have lost their teeth and surrounding bone because of surgery for oral cyst or tumor. Rehabilitation with fixed or removable prosthesis is even more challenging when the edentulous span is long and the ridge is defective. Anatomic deformities and unfavorable biomechanics encountered in the region of resection add to the misery. In such situation, a fixed-removable prosthesis allows favorable biomechanical stress distribution along with restoration of esthetics, phonetics, comfort, hygiene, and better postoperative care and maintenance. This article describes rehabilitation of two cases with mandibular defects with an attachment-retained fixed-removable hybrid prosthesis.

  15. Influence of connection type on the biomechanical behavior of distal extension mandibular removable partial dentures supported by implants and natural teeth.

    Science.gov (United States)

    Xiao, Wei; Li, Zhiyong; Shen, Shiqian; Chen, Shaowu; Chen, Sulin; Wang, Jiawei

    2016-02-01

    Few studies are performed to evaluate the influence of connection type on the stress distribution of distal extension mandibular removable partial dentures (RPDs) supported by both implants and natural teeth. In this study, five three-dimensional finite element models were prepared to simulate mandibular bilateral partially edentulous arches. Four were RPDs supported by both implants and natural teeth, and the other one was RPDs supported only by natural teeth. The maximum equivalent (EQV) stress values of bone around implants, the abutments, and the mucosa displacements of the related supporting structures were measured. It was found that a non-rigid telescopic coping was more favorable to protect the implant than a rigid telescopic coping. Compared with other connection types, the easy resilient attachment (ERA) system seemed to be effective to associate implant without complications. However, the results obtained in the present study should be cautiously interpreted in the clinic.

  16. A Novel Computer-Aided Design/Computer-Assisted Manufacture Method for One-Piece Removable Partial Denture and Evaluation of Fit.

    Science.gov (United States)

    Ye, Hongqiang; Li, Xinxin; Wang, Guanbo; Kang, Jing; Liu, Yushu; Sun, Yuchun; Zhou, Yongsheng

    2018-02-15

    To investigate a computer-aided design/computer-aided manufacturing (CAD/CAM) process for producing one-piece removable partial dentures (RPDs) and to evaluate their fits in vitro. A total of 15 one-piece RPDs were designed using dental CAD and reverse engineering software and then fabricated with polyetheretherketone (PEEK) using CAM. The gaps between RPDs and casts were measured and compared with traditional cast framework RPDs. Gaps were lower for one-piece PEEK RPDs compared to traditional RPDs. One-piece RPDs can be manufactured by CAD/CAM, and their fits were better than those of traditional RPDs.

  17. Nitrous oxide production in intermittently aerated Partial Nitritation-Anammox reactor: oxic N2O production dominates and relates with ammonia removal rate

    DEFF Research Database (Denmark)

    Blum, Jan-Michael; Jensen, Marlene Mark; Smets, Barth F.

    2018-01-01

    to an effective control of accumulation of nitrogen intermediates. However, due to frequent changes of redox conditions under intermittent aeration regimes, nitrous oxide production and emissions are dynamic. In this study the production and emission dynamics of nitrous oxide in an intermittently aerated......Emissions of the greenhouse gas nitrous oxide from the Partial Nitritation-Anammox process are of concern and can determine the carbon footprint of the process. In order to reduce nitrous oxide emissions intermittent aeration regimes have been shown to be a promising mode of operation, possibly due......-production rates were observed at ammonia removal rates below 5 mg NH3-N*gVSS−1*L−1, when the fraction of nitrous oxide produced was 0.011 ± 0.004% (per ammonia removed). Based on the nitrous oxide dynamics and correlations, reactor operation at relatively low nitrogen loadings (below 100 mg NH4+-N*L−1), ammonia...

  18. Chromium carcinogenicity: California strategies.

    Science.gov (United States)

    Alexeeff, G V; Satin, K; Painter, P; Zeise, L; Popejoy, C; Murchison, G

    1989-10-01

    Hexavalent chromium was identified by California as a toxic air contaminant (TAC) in January 1986. The California Department of Health Services (CDHS) concurred with the findings of the International Agency for Research on Cancer that there is sufficient evidence to demonstrate the carcinogenicity of chromium in both animals and humans. CDHS did not find any compelling evidence demonstrating the existence of a threshold with respect to chromium carcinogenesis. Experimental data was judged inadequate to assess potential human reproductive risks from ambient exposures. Other health effects were not expected to occur at ambient levels. The theoretically increased lifetime carcinogenic risk from a continuous lifetime exposure to hexavalent chromium fell within the range 12-146 cancer cases per nanogram hexavalent chromium per cubic meter of air per million people exposed, depending on the potency estimate used. The primary sources found to contribute significantly to the risk of exposure were chrome platers, chromic acid anodizing facilities and cooling towers utilizing hexavalent chromium as a corrosion inhibitor. Evaluation of genotoxicity data, animal studies and epidemiological studies indicates that further consideration should be given to the potential carcinogenicity of hexavalent chromium via the oral route.

  19. Biosorption of hexavalent chromium in a tannery industry wastewater using fungi species

    International Nuclear Information System (INIS)

    Sivakumar, D.

    2016-01-01

    The isolated fungi species of different kinds from chromium contaminated soil sites located in Nagalkeni, Chennai were used for reducing chromium(VI) in a tannery industry wastewater of Nagalkeni, Chennai. The experiments were conducted to know biosorption potential of isolated fungi species for removing chromium(VI) in a tannery industry wastewater against the different p H, fungi biomass and chromium(VI) concentration (dilution ratio). The results of this study indicated that the order of maximum removal of chromium(VI) by an isolated fungi species at an optimum pH of 3, fungi biomass of 4g and an initial chromium(VI) concentration of 18.125 mg/L (dilution ratio 4) is A. niger > A. flavus > A. fumigatus > A. nidulans > A. heteromorphus > A. foetidus > A. viridinutans. This study found that the maximum removal of chromium(VI) was achieved by Aspergillus niger (96.3 %) than other fungi species at chromium(VI) concentration of 18.125 mg/L in a tannery industry wastewater. The chromium removal from tannery industry wastewater was validated by checking chromium removal in an aqueous solution and by checking the removal efficiency of other parameters in a tannery industry wastewater using same isolated A. niger. Biosorption model was proposed to simulate the experimental condition for removing chromium(VI) in a tannery industry wastewater by all isolated fungi species. The R2 and x2 values of the proposed model predicted that the proposed biosorption model is very much useful for predicting the trend of reduction potential of chromium(VI) in a tannery industry wastewater by all isolated fungi species. This study suggested that one could select the type of fungi species, ion concentration level, selection of treatment period, quantity of biomass to be used, and p H level of the medium, to achieve the highest reduction of any toxic metals from any contaminated water, wastewater and soil environment.

  20. Corneal haze and visual outcome after collagen crosslinking for keratoconus: A comparison between total epithelium off and partial epithelial removal methods

    Directory of Open Access Journals (Sweden)

    Hasan Razmjoo

    2014-01-01

    Full Text Available Background: Keratoconus is an asymmetric, bilateral, progressive noninflammatory ectasia of the cornea that affects approximately 1 in 2000 of the general population. This may cause a significant negative impact on quality of life. Corneal collagen crosslinking (CXL is one of the recently introduced methods that have been used to decrease the progression of keratoconus, in particular, as well as other corneal-thinning processes. Materials and Methods: A total of 44 keratoconic eyes of 22 patients were enrolled in this randomized prospective study, after obtaining informed consent. In the first group, the corneal epithelium were totally removed and in the second group, the central 3 mm of epithelium was kept intact and partial removal was performed. After collagen crosslinking in both groups, comprehensive ophthalmologic examination was performed on all patients before and 6 months after the surgery. This article is registered at www.clinicaltrial.gov with registration number NCT01809977. Results: The difference between the two groups was not statistically significant regarding postoperative corneal haziness, refraction, and visual acuity (P > 0.05. However, comparison of pre- and postoperative parameters within each group revealed that total removal of the cornea has resulted in significant improvement of K-max (P value: 0.01 and Q-value (P value: 0.009; while eyes in partial removal group had better improvement of corrected vision (P value: 0.006. Both methods had significant and similar increase in optical corneal density (P < 0.0001. Conclusion: In our study, keeping the central corneal epithelium intact was not beneficial for decreasing corneal haziness, however, this method caused better improvement in corrected vision. Total epithelium off technique resulted in better improvement of K-max and Q-value.

  1. Nitrogen removal from slaughterhouse wastewater through partial nitrification followed by denitrification in intermittently aerated sequencing batch reactors at 11 degreeC.

    Science.gov (United States)

    Pan, Min; Henry, Liam Garry; Liu, Rui; Huang, Xiaoming

    2014-01-01

    This study is aimed to examine the removal of nitrogen from high strength slaughterhouse wastewater at 11 degreeC via partial nitrification followed by denitrification (PND), using the intermittently aerated sequencing batch reactor (IASBR) technology. The slaughterhouse wastewater contained chemical oxygen demand (COD) of 6068 mg/L, total nitrogen (TN) of 571 mg/L, total phosphorus (TP) of 51 mg/L and suspended solids of 1.8 g/L, on average. The laboratory-scale IASBR reactors had a working volume of 8 L and was operated at an average organic loading rate of 0.61 g COD/(L-d). At the cycle duration of 12 h, COD was efficiently removed under three aeration rates of 0.4, 0.6 and 0.8 L air/min. Among the three aeration rates, the optimum aeration rate was 0.6 L air/min with removals of COD, TN, and TP of 98%, 98%, and 96%, respectively. The treated wastewater met the Irish emission standards. The microbial community analysis by fluorescence in situ hybridization shows 12 +/- 0.4% of ammonium oxidizing bacteria, and 7.2 - 0.4% of nitrite oxidizing bacteria in the general bacteria (EUB) in the activated sludge at the aeration rate of 0.6 L air/min, leading to efficient partial nitrification. PND effectively removed nitrogen from slaughterhouse wastewater at 11degreeC, but PND efficiency was dependent on the aeration rate applied. PND efficiencies were up to 75.8%, 70.1% and only 25.4% at the aeration rates of 0.4, 0.6, and 0.8 L air/min.

  2. The feasibility of an up-flow partially aerated biological filter (U-PABF) for nitrogen and COD removal from domestic wastewater.

    Science.gov (United States)

    Tao, Chen; Peng, Tong; Feng, Chuanping; Chen, Nan; Hu, Qili; Hao, Chunbo

    2016-10-01

    An up-flow partially aerated biological filter (U-PABF) was developed to study the removal of nitrogen and chemical oxygen demand (COD) from synthetic domestic wastewater. The removal of NH4(+)-N was primarily attributed to adsorption in the zeolite U-PABF and to bioprocesses in the ceramic U-PABF. When the hydraulic retention time (HRT) was 5.2h, the ceramic U-PABF achieved a good performance and the NH4(+)-N, total nitrogen (TN), and COD removal efficiency reached 99.08±8.79%, 72.83±0.68%, and 89.38±1.04%, respectively. The analysis of NH4(+)-N, NO3(-)-N, NO2(-)-N, and TN at different depths revealed the simultaneous existence of nitrification-denitrification, and anaerobic ammonium oxidation (anammox) in ceramic U-PABF. Illumina pyrosequencing confirmed the existence of Planctomycetes, which are responsible for anammox. The results indicated that the nitrification-denitrification and anammox all contributed to the high removal of NH4(+)-N, TN, and COD in the U-PABF. Copyright © 2016 Elsevier Ltd. All rights reserved.

  3. A simple route to synthesize conductive stimuli-responsive polypyrrole nanocomposite hydrogel particles with strong magnetic properties and their performance for removal of hexavalent chromium ions from aqueous solution

    Energy Technology Data Exchange (ETDEWEB)

    Ahmad, Hasan, E-mail: samarhass@yahoo.com [Department of Chemistry, Rajshahi University, Rajshahi 6205 (Bangladesh); Rahman, Mohammad Mostafizar; Ali, Mohammad Azgar [Department of Chemistry, Rajshahi University, Rajshahi 6205 (Bangladesh); Minami, Hideto [Graduate School of Engineering, Kobe University, Kobe 657-8501 (Japan); Tauer, Klaus [Max Planck Institute of Colloid and Interfaces, Am Mühlenberg, 14476 Golm (Germany); Gafur, Mohammad Abdul [Pilot Plant and Process Development Centre, BCSIR, Dhaka 1205 (Bangladesh); Rahman, Mohammad Mahbubor [Department of Chemistry, Rajshahi University, Rajshahi 6205 (Bangladesh)

    2016-08-15

    A combination of maghemite polypyrrole (PPy/γ-Fe{sub 2}O{sub 3}) and stimuli-responsive properties in the same hydrogel microspheres is expected to enhance their application potential in various fields such as tissue engineering, regenerative medicine, biosensors, biomedical applications and removal of heavy metals from waste water, catalysis etc. In this investigation a simple two step process is used to prepare conductive stimuli-responsive polypyrrole (PPy) composite hydrogel particles with strong magnetic properties. Poly(styrene-methacrylic acid-N-isopropylacrylamide-polyethelene glycol methacrylate) or P(S-NIPAM-MAA-PEGMA) hydrogel seed particles are first prepared by soap-free precipitation copolymerization. The copolymer hydrogel particles exhibited both temperature- and pH-responsive volume phase transition. Conductive P(S-NIPAM-MAA-PEGMA)/PPy/γ-Fe{sub 2}O{sub 3} nanocomposite hydrogel particles are then prepared by seeded chemical oxidative polymerization of pyrrole in the presence of P(S-NIPAM-MAA-PEGMA) hydrogel seed particles using FeCl{sub 3} as a oxidant and p-toluene sulfonic acid ( p-TSA) as a dopant. In the reaction system FeCl{sub 3} functioned as a source of Fe(III) for the formation of γ-Fe{sub 2}O{sub 3}. This reaction also requires the initial presence of Fe(II) provided by the addition of FeCl{sub 2}. The size and size distribution, surface structure, and morphology of the prepared conductive composite hydrogel particles are confirmed by FTIR, electron micrographs, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and UV–visible spectroscopy. The performance of nanocomposite hydrogel particles has been evaluated for the removal of hexavalent chromium (Cr) ions from water. - Highlights: • P(S-NIPAM-MAA-PEGMA) hydrogel particles were prepared. • P(S-NIPAM-MAA-PEGMA)/PPy/γ-Fe{sub 2}O{sub 3} nanocomposite hydrogel particles were prepared. • Oxidative polymerization of pyrrole and precipitation of γ-Fe{sub 2}O{sub 3

  4. Impact of long-term partial aeration on the removal of 2,4,6-trichlorophenol in an initially methanogenic fluidized bed bioreactor.

    Science.gov (United States)

    Garibay-Orijel, Claudio; Hoyo-Vadillo, Carlos; Ponce-Noyola, Teresa; García-Mena, Jaime; Poggi-Varaldo, Héctor Mario

    2006-08-05

    A fluidized bed bioreactor (FBBR) was operated for more than 1000 days under two regimes, Methanogenic (M) and Methanogenic-Aerobic (M-A), to remove 2,4,6-trichlorophenol (TCP) and phenol (Phe) from a synthetic wastewater, containing different amounts of TCP and Phe, using different aeration flow-rates (0, 2.13, and 1.06 NL O(2)/L.day). M conditions (80:20 mg/L of TCP:Phe, 0 NL O(2)/L.day) showed similar TCP and Phe removal (>95%). Nevertheless accumulation of 4-chlorophenol (4CP) up to 16 mg/L and Phe up to 4 mg/L was observed, while in M-A conditions (80:20 mg/L of TCP:Phe, 2.13 NL O(2)/L.day) TCP and Phe removal achieved 99.9(+)% and after 70 days no accumulation of intermediates were detected. The increase of TCP and Phe in the influent under M-A conditions from 80:20 to 120:30 mg/L of TCP:Phe did not negatively affect the removal of TCP, intermediates and Phe; in fact, they were similar to those in previous M-A conditions. The decrease in the oxygen flow rate from 2.13 to 1.06 NL O(2)/L.day had no negative effect on pollutant removals, which were as high as in previous two M-A conditions. The specific methanogenic activity of bioparticles of the fluidized bed decreased with long-term partial aeration, starting from 1.097 mmol CH(4)/h.g(TKN) in the M regime (day 60) to TCP and less chlorinated intermediates could be achieved in an initially methanogenic FBBR under conditions of partial aeration, although long-term operation seemed to negatively affect the methanogenic activity of biomass. It is also likely that after extended aeration the microbial community was finally enriched with strains with the ability to attack 2,4,6-TCP under aerobic conditions. This report represents the first evidence of a long exposure to oxygen of an anaerobic microbial consortium that efficiently remove TCP. (c) 2006 Wiley Periodicals, Inc.

  5. Behavior of mandibular canines as abutment teeth and indirect retainers in Kennedy class II Removable Partial Denture Prosthesis

    Directory of Open Access Journals (Sweden)

    Marisol C. Camacho

    2018-03-01

    Full Text Available Purpose: The purpose of this study was to evaluate the behavior of mandibular canines acting as abutment teeth and indirect retainers of a Kennedy class II according to different designs: lingual rest and lingual rest associated with a reciprocal arm. Materials & methods: A resin cast with two simulated canine teeth was made in Ni-Cr alloy, representing a Kennedy class II mandibular arch. With the objective of simulating the resilience of the periodontal ligament, a polyurethane layer was added at the canine tooth's root. A metallic framework of Co-Cr alloy was fabricated with a T bar clasp and a lingual rest associated with a reciprocal arm. To obtain the second framework, the reciprocal arm was removed using a tungsten bur. Each framework was submitted to tensile force using a VersaTest machine. The magnitude and direction of canine movement during removal of the framework was measured using two dial gauges (mm. The axial tensile force required to remove the experimental framework (N was also evaluated. The data were compared using the paired t-test with 95% confidence intervals. Differences were considered significant at P < .05. Results: The mean retentive force of the modified design framework with the reciprocal arm was significantly higher (P < .0001 than that of the framework with the lingual rest. The abutment teeth showed movement in the lingual and mesial directions, and this movement was less when associated with the reciprocal arm design. Conclusion: The reciprocal arm in association with a lingual rest in the framework decreased the movement of the abutment teeth when analyzed in the bucco-lingual and mesio-distal directions and contributed to increased retention by friction. Keywords: Materials science, Dentistry, Engineering

  6. A Survey of Removable Partial Denture (RPD) Retentive Elements in Relation to the Type of Edentulism and Abutment Teeth Found in Commercial Laboratories, Athens, Greece

    Science.gov (United States)

    Sotiriou, Michael; Zissis, Alcibiades

    2014-01-01

    Objective The aim of this survey was to record removable partial denture (RPD) retentive elements and abutment teeth in partially edentulous patients, identified in commercial laboratories in Athens, Greece. Material and Methods 628 master casts with the corresponding cast metal frameworks used in the construction of RPDs were evaluated. Casts were photographed to identify the number and position of existing teeth, the partial edentulism class and the retentive elements. Prevalence tables and the x2 test were used for the statistical analysis of the collected data (α=.05). Results There were 276 maxillary (43.9%) and 352 (56.1%) mandibular casts. Maxillary edentulism entailed almost a total absence of right third molars in 96.7% and left third molars 96.0% of casts, with lower rates for the first and second molars. Edentulism in the posterior mandible presented a similar pattern. The most profound findings concerning retentive elements were: 91.9% of the retainers used were clasps and the remaining 8.1% were attachments. Of the clasps used, 48.9% were of the Roach Τ type, a finding more common in Kennedy Class I as compared to other Kennedy Classes (p<0.01). The circumferential clasps accounted for 19.3% of the total clasps used, and it was less frequently presented (8.8%) in Kennedy I Classes (p<0.01). Conclusions Roach clasps were used in the majority of cases whereas RPI clasps and attachments were rarely used. PMID:27688367

  7. Chromium removal from aqueous media by superparamagnetic ...

    Indian Academy of Sciences (India)

    from aqueous waste. The characterization of the prepared nanoparticles was done by XRD, FTIR, TEM and. VSM techniques. Adsorption of Cr(VI) on the surface of ..... Kizil R, Irudayaraj J and Seetharaman K 2002 J. Agric. Food Chem. 50 3912. 29. Tuutijärvi T, Lu J, Sillanpää M and Chen G 2009 J. Hazard. Mater. 166 1415.

  8. Partial removal and detoxification of Malachite Green and Crystal Violet from laboratory artificially contaminated water by Pleurotus ostreatus

    Directory of Open Access Journals (Sweden)

    Claudia Marcela Rivera-Hoyos

    2016-10-01

    Full Text Available The triphenylmethane dyes Malachite Green (MG and Crystal Violet (CV are cationic dyes and mix with domestic wastewater when dumped; increasing, among others, the chemical and biological demand of oxygen and can cause acute toxicity at different trophic levels. Promoting the removal (decolorization of MG and CV, and laccase activity (54.8 ± 8.9 and 30.6 ± 2.9 UL-1 respectively by using P. ostreatus viable biomass needed parameters such as pH (4.5 and 6.0, temperature (25 to 30 °C, stirring speed (120 rpm, percentage of inoculum (2% v/v, and dye concentration (20 and 10 mg L-1. In adsorption studies, it was showed that an acidic pH favors the adsorption of both dyes and the model of pseudo-second order describes best the phenomenon of adsorption. Finally, the germination index (GI, using Lactuca sativa seeds for the initial dyes solutions, was <50%; demonstrating its high phytotoxic effect. When dye solutions were treated with viable biomass, the GI increased, leaving open the possibility to performing future research to determine if the aqueous solutions, post-treated with P. ostreatus, could be used in treatments that generate less toxic water which could be used in processes that do not require potable water.

  9. Efficient Removal of Heavy Metals from Polluted Water with High Selectivity for Mercury(II) by 2-Imino-4-thiobiuret-Partially Reduced Graphene Oxide (IT-PRGO).

    Science.gov (United States)

    Awad, Fathi S; AbouZeid, Khaled M; El-Maaty, Weam M Abou; El-Wakil, Ahmad M; El-Shall, M Samy

    2017-10-04

    A novel chelating adsorbent, based on the chemical modification of graphene oxide by functionalization amidinothiourea to form 2-imino-4-thiobiuret-partially reduced graphene oxide (IT-PRGO), is used for the effective extraction of the toxic metal ions Hg(II), Cu(II), Pb(II), Cr(VI), and As(V) from wastewater. FTIR and Raman spectroscopy, XRD, and XPS confirm the successful incorporation of the amidinothiourea groups within the partially reduced GO nanosheets through nucleophilic substitution reactions with the acyl chloride groups in the chemically modified GO. The IT-PRGO adsorbent shows exceptional selectivity for the extraction of Hg(II) with a capacity of 624 mg/g, placing it among the top of carbon-based materials known for the high capacity of Hg(II) removal from aqueous solutions. The maximum sorption capacities for As(V), Cu(II), Cr(VI), and Pb(II) are 19.0, 37.0, 63.0, and 101.5 mg/g, respectively. The IT-PRGO displays a 100% removal of Hg(II) at concentrations up to 100 ppm with 90%, 95%, and 100% removal within 15, 30, and 90 min, respectively, at 50 ppm concentration. In a mixture of six heavy metal ions containing 10 ppm of each ion, the IT-PRGO shows a removal of 3% Zn(II), 4% Ni(II), 9% Cd(II), 21% Cu(II), 63% Pb(II), and 100% Hg(II). A monolayer adsorption behavior is suggested based on the excellent agreement of the experimental sorption isotherms with the Langmuir model. The sorption kinetics can be fitted well to a pseudo-second-order kinetic model which suggests a chemisorption mechanism via the amidinothiourea groups grafted on the reduced graphene oxide nanosheets. Desorption studies demonstrate that the IT-PRGO is easily regenerated with the desorption of the metal ions Hg(II), Cu(II), Pb(II), Cr(VI), and As(V) reaching 96%, 100%, 100%, 96%, and 100%, respectively, from their maximum sorption capacities using different eluents. The IT-PRGO is proposed as a top performing remediation adsorbent for the extraction of heavy metals from waste and

  10. Multifactorial risk assessment for survival of abutments of removable partial dentures based on practice-based longitudinal study.

    Science.gov (United States)

    Tada, Sayaka; Ikebe, Kazunori; Matsuda, Ken-Ichi; Maeda, Yoshinobu

    2013-12-01

    Predicting the tooth survival is such a great challenge for evidence-based dentistry. To prevent further tooth loss of partially edentulous patients, estimation of individualized risk and benefit for each residual tooth is important to the clinical decision-making. While there are several reports indicating a risk of losing the abutment teeth of RPDs, there are no existing reports exploring the cause of abutment loss by multifactorial analysis. The aim of this practice-based longitudinal study was to determine the prognostic factors affecting the survival period of RPD abutments using a multifactorial risk assessment. One hundred and forty-seven patients had been previously provided with a total of 236 new RPDs at the Osaka University Dental Hospital; the 856 abutments for these RPDs were analyzed. Survival of abutment teeth was estimated using the Kaplan-Meier method. Multivariate analysis was conducted by Cox's proportional hazard modelling. The 5-year survival rates were 86.6% for direct abutments and 93.1% for indirect abutments, compared with 95.8% survival in non-abutment teeth. The multivariate analysis showed that abutment survival was significantly associated with crown-root ratio (hazard ratio (HR): 3.13), root canal treatment (HR: 2.93), pocket depth (HR: 2.51), type of abutments (HR: 2.19) and occlusal support (HR: 1.90). From this practice-based longitudinal study, we concluded that RPD abutment teeth are more likely to be lost than other residual teeth. From the multifactorial risk factor assessment, several prognostic factors, such as occlusal support, crown-root ratio, root canal treatment, and pocket depth were suggested. These results could be used to estimate the individualized risk for the residual teeth, to predict the prognosis of RPD abutments and to facilitate an evidence-based clinical decision making. Copyright © 2013 Elsevier Ltd. All rights reserved.

  11. Preparation of Silica Modified with 2-Mercaptoimidazole and its SorptionProperties of Chromium(III

    Directory of Open Access Journals (Sweden)

    Harry Budiman

    2009-01-01

    Full Text Available Modified silica gel was prepared to remove the heavy metal of chromium(III from water sample. Silica gel was used as supporting material and the 2-mercaptoimidazole was immobilized onto surface silica so that the silica would have selective properties to adsorb the heavy metal chromium(III through the formation of coordination compound between the 2-mercaptoimidazole and chromium(III. The characterization of modified silica gel was carried out by analyzing the Fourier Transform Infrared Spectrum of this material in order to ensure the immobilization of 2-mercaptoimidazole onto the surface. The effect of pH solution, initial concentration of chromium(III, and interaction time were investigated in batch mode to find the adsorption properties of chromium(III onto modified silica. The condition optimum of these parameters was applied to determine the removal percentage of chromium(III in water sample using the modified silica gel

  12. Clinical performance of cements as luting agents for telescopic double crown-retained removable partial and complete overdentures.

    Science.gov (United States)

    Behr, Michael; Kolbeck, Carola; Lang, Reinhold; Hahnel, Sebastian; Dirschl, Lisa; Handel, Gerhard

    2009-01-01

    The aim of this study was to investigate the survival rates and technical failures of removable prostheses (RPs) supported by telescopic double crown (TDC)-retained abutment teeth luted with zinc-phosphate or glass-ionomer cement. Clinical records of 577 patients (288 women, 289 men) who received 577 TDC-retained RPs supported by 1,807 abutments at the Department of Prosthodontics of the University Hospital Regensburg, Regensburg, Germany, between 1984 and 2007 were analyzed. The 577 prostheses included 200 attached to telescopic crowns with friction fit (FFs), 62 to conical crowns (CCs), and 315 to parallel-sided telescopic crowns with clearance fit (CFs). Survival probabilities were evaluated for the RPs, loss of cementation of the inner copings, secondary caries, and abutment teeth that required endodontic treatment using the Kaplan-Meier method. A Cox regression analysis determined the impact of covariates such as sex, denture location (maxilla/mandible), Eichner classification, number of abutment teeth, and the type of double crown system used. The 10-year survival probability was 98.8% +/- 0.09% for FFs, 92.9% +/- 0.41% for CCs, and 86.6% +/- 0.05% for CFs. During the observation period, loss of cementation was frequently observed (FFs: 32%, CCs: 53.2%, CFs: 21.3%). After 15 years, more than 75% of patients had experienced at least one "loss of cementation" event. In this respect, zinc-oxide phosphate and glass-ionomer cements did not show any significant difference. The long-term successful outcome of the RP experience was not compromised, although numerous clinical visits were required for maintenance. The predominant maintenance procedure was the need for recementation of the inner copings.

  13. Using Intraoral Scanning Technology for Three-Dimensional Printing of Kennedy Class I Removable Partial Denture Metal Framework: A Clinical Report.

    Science.gov (United States)

    Hu, Feng; Pei, Zhenhua; Wen, Ying

    2017-11-16

    Removable partial dentures (RPDs) are used to restore missing teeth and are traditionally fabricated using the lost-wax casting technique. The casting process is arduous, time-consuming, and requires a skilled technician. The development of intraoral scanning and 3D printing technology has made rapid prototyping of the RPD more achievable. This article reports a completed case of direct fabrication of a maxillary RPD metal framework (Kennedy Class I) using intraoral scanning and 3D printing techniques. Acceptable fit and satisfactory clinical outcome were demonstrated. Intraoral scanning and 3D printing for fabrication of the RPD metal framework is a useful alternative to conventional impression and casting techniques, especially for patients suffering from nasal obstruction or intolerance. © 2017 by the American College of Prosthodontists.

  14. Prevalence of signs and symptoms of temporomandibular disorders (TMD) in patients wearing bimaxillary complete dentures, removable partial dentures and in students with natural dentition.

    Science.gov (United States)

    Bordin, Thaisa B; Conci, Ricardo A; Pezzini, Maristela M G; Pezzini, Rolando P; Mendonça, Márcio J

    2013-01-01

    Temporomandibular Disorder (TMD) has attained a prominent role within the context of dental care due to its high prevalence. The aim of this study was to evaluate the prevalence of signs and symptoms of TMD in students at the State University of West of Paraná (UNIOESTE) with natural dentition, and in patients with removable partial dentures and double complete dentures. A total of 210 randomly selected individuals of both genders were evaluated, being divided into three groups: seventy students at the UNIOESTE with natural dentition (Group 1), seventy patients with removable partial dentures (Group 2) and seventy patients with bimaxillary complete dentures (Group 3). The data were collected by a single examiner using the American Academy of Orofacial Pain questionnaire for triage, where a single affirmative response to any of the situations mentioned was enough to carry out clinical evaluation. Kolmogorov Smirnov, Mann Whitney, Chi-Square, ANOVA and Tukey's statistical tests were performed. The most prevalent signs and symptoms of TMD in Group 1 were pain or difficulty in chewing or talking, perception of recent change in bite and deviations during the course of mandibular movements. In Group 2 they were perceptions of recent changes in the bite, deflections in the mandibular movements, presence of joint sounds, pain during excursive movements and muscle tenderness. The most prevalent signs and symptoms in Group 3 were limited to mouth opening and poor stability and retention of at least one of the prostheses. Group 3 also reported having received treatment for headaches or facial pain with a high prevalence. Group 2 had the highest prevalence of signs and symptoms. Prevalence was similar in Groups 1 and 3.

  15. Removable partial denture models and comunication among dentists and laboratory technicians in the city of de Teresina, Piauí, Brazil

    Directory of Open Access Journals (Sweden)

    Carmem Dolores Vilarinho Soares de Moura

    2009-10-01

    Full Text Available Objective: To evaluate the quality of models for making removable partial dentures. Methods: In this Study, 140 models were analysed in 05 dental prosthesis laboratories in the city of Teresina, Piauí, Brazil, registered with the Conselho Regional de Odontologia. A form containing 14 closed questions was applied, and the data collected were submitted to statistical analysis using the SPSS program. The models were analysed under natural or artificial light and photographed for record and illustration purposes. Results: The results showed that in 100% of the cases the molding material used was alginate, and 93.43% of the models were poured by the dentist. Of these, 64.47% were poured in stone plaster and 36.43% in special plaster. According to criteria such as surface quality, reproduction of details, presence of bubbles and/or nodules, adequate reproduction of the edentulous area, 78.57% of the models were considered inadequate. The majority of the models (96.43%, were mounted in an articulator by the Dental Laboratory Technician, but only 1 dentist sent the record for mounting the models. The hinge type articulator was used in 97.14% of the mountings. In 94.29% of the cases, the planning and design were not executed by the dentist and in 87.86% of the cases no evidence of mouth preparation was found. In 80% of the cases, communication between the dentist and the Dental Laboratory Technician was done by telephone. Conclusion: Thus it was verified that the removable partial denture continues to be neglected as regards its clinical and laboratorial fabrication, through an excessive transfer of responsibilities from the dentist to the Dental Laboratory Technician and an inefficient communication between the two.

  16. Adsorption of Chromium from Aqueous Solution Using Polyaniline

    Directory of Open Access Journals (Sweden)

    Majid Riahi Samani

    2011-10-01

    Full Text Available New group of polymers have been synthesized that are conductive of electricity so they are called conducting polymers. One of the most conducting polymers is "polyaniline". In the present study, polyaniline was synthesized by oxidizing aniline monomer under strongly acidic conditions using potassium iodate as an initiator of oxidative polymerization. Synthesized polyaniline as a powder used as an adsorbent to remove chromium from aqueous solution. Experiments were conducted in batch mode with variables such as amount of polyaniline, chromium solution pH and adsorbtion isotherms. Due to presence of Cr (III in solution after using polyaniline, removal mechanism is the combination of surface adsorption and reduction. It seems that polyaniline reduces the Cr(VI to Cr(III and adsorbs the Cr(III and a part of remaining  Cr(VI. It is well known that nitrogen atom in compounds of amine derivative makes co-ordinate bond with positive charge of metals due to the presence of electron in sp3 orbital of nitrogen. The majority of total chromium removal  occurred at 30minute for polyaniline  and the optimum  time for  hexavalent chromium  removal was about 5 min. Polyaniline has the maximum total cheomiume removal at pH, 3-9. The maximum hexavalent chromium removal occurred at acidic pH for polyanilines. The equilibrium adsorption data for polyaniline fitted both Freundlich’s and Langmuir’s isotherms. This research shows that polyaniline can be used as an adsorbent  for removal chromium from aqueous solution.

  17. Immediate versus delayed loading of strategic mini dental implants for the stabilization of partial removable dental prostheses: a patient cluster randomized, parallel-group 3-year trial.

    Science.gov (United States)

    Mundt, Torsten; Al Jaghsi, Ahmad; Schwahn, Bernd; Hilgert, Janina; Lucas, Christian; Biffar, Reiner; Schwahn, Christian; Heinemann, Friedhelm

    2016-07-30

    Acceptable short-term survival rates (>90 %) of mini-implants (diameter implants as strategic abutments for a better retention of partial removable dental prosthesis (PRDP) are not available. The purpose of this study is to test the hypothesis that immediately loaded mini-implants show more bone loss and less success than strategic mini-implants with delayed loading. In this four-center (one university hospital, three dental practices in Germany), parallel-group, controlled clinical trial, which is cluster randomized on patient level, a total of 80 partially edentulous patients with unfavourable number and distribution of remaining abutment teeth in at least one jaw will receive supplementary min-implants to stabilize their PRDP. The mini-implant are either immediately loaded after implant placement (test group) or delayed after four months (control group). Follow-up of the patients will be performed for 36 months. The primary outcome is the radiographic bone level changes at implants. The secondary outcome is the implant success as a composite variable. Tertiary outcomes include clinical, subjective (quality of life, satisfaction, chewing ability) and dental or technical complications. Strategic implants under an existing PRDP are only documented for standard-diameter implants. Mini-implants could be a minimal invasive and low cost solution for this treatment modality. The trial is registered at Deutsches Register Klinischer Studien (German register of clinical trials) under DRKS-ID: DRKS00007589 ( www.germanctr.de ) on January 13(th), 2015.

  18. Impact of Removable Partial Dental Prostheses on the Oral Health-Related Quality of Life of a South African Cohort with Varied Distributions of Missing Posterior Teeth.

    Science.gov (United States)

    Khan, Sadika; Chikte, Usuf; Omar, Ridwaan

    2017-10-25

    To determine the impact of removable partial dental prostheses on satisfying the daily functioning and quality of life (QoL) of adult patients with different distributions of missing posterior teeth. A cross-sectional interventional study was carried out on 80 patients having variously distributed posteriorly shortened and interrupted arches. Treatment comprised provision of partial dentures by senior dental students, supervised by senior clinical teachers who had knowledge of the potential benefits of the shortened dental arch (SDA) concept. The Oral Impacts on Daily Performance Index was completed before and 6 months after prosthetic treatment across groups comprising Kennedy Classes I, II, and III arches. Analysis included descriptive statistics and associations and comparisons between variables. Mean age of patients was 57.4 years (SD = 13.1), many were retired (72.2%), and a majority were females (60%). Most patients lived in urban areas (95%), and were largely unemployed (63.3%). At pretreatment, only 31.3% of patients reported having good dental health and satisfaction with their current oral state, while 82.5% said they had a great need for treatment. The negative oral impacts that were most frequently experienced were those of eating (67.5%), smiling (50%), and being emotionally disturbed (63.8%). Post-treatment, 76.3% indicated good oral health and satisfaction with no significant differences between the 3 Kennedy groups. Any further negative impacts were reported mostly for Kennedy Classes I and II. Overall, significant reductions of negative impacts were observed following treatment with dentures, across the 3 Kennedy groups, with respect to improved function, satisfaction, and oral health-related QoL. The findings confirm the reliance by partially dentate patients in all 3 Kennedy groups on dentures for improved oral health, although the possible benefits of the SDA concept as an alternative treatment option was not specifically explored. © 2017 by

  19. Achieve efficient nitrogen removal from real sewage in a plug-flow integrated fixed-film activated sludge (IFAS) reactor via partial nitritation/anammox pathway.

    Science.gov (United States)

    Yang, Yandong; Zhang, Liang; Cheng, Jun; Zhang, Shujun; Li, Baikun; Peng, Yongzhen

    2017-09-01

    This study tested the feasibility of plug-flow integrated fixed-film activated sludge (IFAS) reactor in applying sewage partial nitritation/anammox (PN/A) process. The IFAS reactor was fed with real pre-treated sewage (C/N ratio=1.3) and operated for 200days. High nitrogen removal efficiency of 82% was achieved with nitrogen removal rates of 0.097±0.019kgN/(m 3 ·d). Therefore, plug-flow IFAS reactor could be an alternative to applying sewage PN/A process. Besides, it was found that the stability of sewage PN/A process was significantly affected by residual ammonium. Nitrate accumulated in effluent and PN/A performance deteriorated when residual ammonium was below 1mg/L. On the contrary, long-term stable PN/A operation was achieved when residual ammonium was over 3mg/L. Copyright © 2017 Elsevier Ltd. All rights reserved.

  20. Efecto de la asociación alga-bacteria Bostrychia calliptera (Rhodomelaceae en el porcentaje de remoción de cromo en laboratorio The effect of chromium removal by Algae-bacteria Bostrychia calliptera (Rhodomelaceae consortia under laboratory conditions

    Directory of Open Access Journals (Sweden)

    Ana Lucía Rengifo-Gallego

    2012-09-01

    Full Text Available Para determinar el porcentaje de remoción de cromo en la asociación alga-bacteria, se tomaron ejemplares del alga Bostrychia calliptera de pneumatóforos de Avicennia germinans y Rizophora mangle, en la desembocadura del Río Dagua, Pacífico colombiano. El ensayo se realizó in vitro en agua marina sintética a dos concentraciones de cromo 5 y 10mg/L, empleando biorreactores con cuatro tratamientos; i material Alga-Bacteria (AB, ii material algal con antibiótico Alga-antibiótico (AA, iii consorcio bacteriano natural (CBN y iv control sin presencia de B. calliptera ni bacteria. Se monitoreó el comportamiento de poblaciones bacterianas y el porcentaje de disminución de cromo mediante AAS (Espectroscopía de absorción atómica. Se obtuvo diferencias significativas entre los tratamientos Alga-bacteria (AB y el consorcio bacteriano natural (CBN, siendo Alga-bacteria más eficiente a 10mg/L (87%. El consorcio bacteriano natural CBN obtuvo mayor porcentaje de remoción a bajas concentraciones de cromo a 5ppm (62.85%. Los resultados mostraron una interacción positiva entre las bacterias asociadas (CBN a la superficie del alga roja B. calliptera en su proceso acumulativo de cromo.Water pollution is one of the most important environmental problems worldwide. Recently, biotechnology studies have oriented efforts to study algae-bacterium consortia with the aim to understand the mechanisms to find a possible solution in environmental sciences. This study determined the percentage of chromium removal by the alga-bacterium association exposed to a set of different chromium concentrations under controlled in vitro conditions. Wild plants of Bostrychia calliptera associated with bacterial populations were collected from Dagua River, Pacific coast of Colombia, and were monitored in the laboratory. The trial was conducted with synthetic seawater in bioreactors at two chromium levels: 5 and 10mg/L, and four different experimental treatments: i algae

  1. Chromium and aging

    Science.gov (United States)

    Aging is associated with increased blood glucose, insulin, blood lipids, and fat mass, and decreased lean body mass leading to increased incidences of diabetes and cardiovascular diseases. Improved chromium nutrition is associated with improvements in all of these variables. Insulin sensitivity de...

  2. Chromium isotope variations

    DEFF Research Database (Denmark)

    D'Arcy, Joan Mary

    Chromium (Cr) stable isotopes are a useful tracer of changes in redox conditions because changes in its oxidation state are accompanied by an isotopic fractionation. For this reason the Cr isotope system is being developed as a potential tool for paleo-redox reconstruction. Dissolved Cr in seawater...

  3. Treatment Outcomes Based on Patients' Self-Reported Measures after Receiving New Clasp or Precision Attachment-Retained Removable Partial Dentures.

    Science.gov (United States)

    Peršić, Sanja; Kranjčić, Josip; Pavičić, Daniela Kovačević; Mikić, Vlatka Lajnert; Čelebić, Asja

    2017-02-01

    To evaluate effects of a treatment taking into consideration esthetics, chewing, and oral health-related quality of life (OHRQoL) of two tooth replacement strategies for maxillary partially edentulous patients with clasp (C-RPD) and precision attachment (PA-RPD) retained removable partial dentures (RPD). The study included 150 patients (72 men, 78 women) who received maxillary RPDs; 88 patients received clasp and 62 patients received precision attachment retained RPDs. Patients completed three questionnaires before treatment and again 3 months after treatment: the Orofacial Esthetic Scale (OES), the Oral Health Impact Profile (OHIP-14), and the Chewing Function Questionnaire (CFQ). Statistical analysis comprised descriptive statistics, paired t-test, and two-factor ANOVA. Both RPD treatments yielded better after-treatment summary scores when compared with the baseline scores (p < 0.01); however, better results were obtained in the PA-RPD group. Gender, as a single factor, did not yield significant effects; mutual interaction of retention type and gender yielded significant effects. The PA-RPD female group assessed esthetics, chewing function, and OHRQoL significantly better than males, and significantly worse than males in the C-RPD group. The covariate baseline scores yielded statistically significant effects; patients with worse pretreatment condition benefited more from both therapies. Treatment outcomes were better in the PA-RPD group than the C-RPDs. Women showed greater concern for the treatment outcomes; their rates were significantly better than in male patients in the PA-RPD group; however, when their satisfaction was lower, their rates were significantly worse than in male patients (in the C-RPD group). © 2015 by the American College of Prosthodontists.

  4. Adsorption and desorption of hydrolyzed metal ions. 3. Scandium and chromium

    International Nuclear Information System (INIS)

    Gray, B.; Matijevic, E.; Clarkson Univ., Potsdam, NY

    1987-01-01

    Adsorption of scandium(III) and chromium(III) species on a PVC latex was measured using radioactive isotopes; the uptake increased with increasing pH. The data were interpreted by combining aspects of the models of James and Healy and also of Anderson and Bockris. The experimental and calculated results agree quite well for scandium, but not for chromium. The deviation in the latter case is believed to be due to polymerization of the hydrolyzed chromium cations and to the interaction of chromium with the anionic surface groups of the latex. Neither of these interactions occur with scandium. Hydrolyzed scandium species adsorbed on the latex were removed by acidifying the dispersion, while chromium complexes were not, substantiating the proposed difference in the chemical nature of chromium and scandium species at the solid/solution interface. 32 refs.; 8 figs.; 8 tabs

  5. A follow-up study on removable partial dentures in undergraduate program: part I. participants and denture use by telephone survey.

    Science.gov (United States)

    Yoshida, Eiko; Fueki, Kenji; Igarashi, Yoshimasa

    2011-07-04

    The aim of this study was to investigate the clinical outcome of removable partial dentures (RPDs) designed to minimize denture mobility during function. Using archived files of the undergraduate program between 2003 and 2005 at Tokyo Medical and Dental University, a list of 169 patients treated with 184 RPDs was created. The RPDs had either an acrylic resin-base or a cobalt-chrome framework-base. Two examiners telephoned all the listed patients and interviewed 118 patients (70%) regarding the use of their RPDs. Of 118 patients, 42 (36%) had stopped using, mainly due to problems with abutment teeth in resin-based dentures, and replacement in cobalt-chrome-based dentures. There was no significant difference in mean age, gender distribution, mean number of remaining/abutment teeth, distribution of denture arch, and Kennedy classification between denture use and nonuse groups (p>0.05). The nonuse group showed a significantly higher percentage of resin-base compared to the use group (p = 0.006). Logistic regression analysis indicated that resin-base was a significant risk factor for nonuse (p = 0.008). The present findings suggest that abutment teeth should be selected carefully, especially in this type of resin-based RPDs, and that the denture base material may be a critical factor which determines denture use.

  6. Clinical application of removable partial dentures using thermoplastic resin-part I: definition and indication of non-metal clasp dentures.

    Science.gov (United States)

    Fueki, Kenji; Ohkubo, Chikahiro; Yatabe, Masaru; Arakawa, Ichiro; Arita, Masahiro; Ino, Satoshi; Kanamori, Toshikazu; Kawai, Yasuhiko; Kawara, Misao; Komiyama, Osamu; Suzuki, Tetsuya; Nagata, Kazuhiro; Hosoki, Maki; Masumi, Shin-Ichi; Yamauchi, Mutsuo; Aita, Hideki; Ono, Takahiro; Kondo, Hisatomo; Tamaki, Katsushi; Matsuka, Yoshizo; Tsukasaki, Hiroaki; Fujisawa, Masanori; Baba, Kazuyoshi; Koyano, Kiyoshi; Yatani, Hirofumi

    2014-01-01

    This position paper proposes a definition and naming standard for removable partial dentures (RPDs) using thermoplastic resin, and presents a guideline for clinical application. A panel of 14 experts having broad experience with clinical application of RPDs using thermoplastic resin was selected from members of the Japan Prosthodontic Society. At a meeting of the panel, "non-metal clasp denture" was referred as the generic name of RPDs with retentive elements (resin clasps) made of thermoplastic resin. The panel classified non-metal clasp dentures into two types: one with a flexible structure that lacks a metal framework and the other having a rigid structure that includes a metal framework. According to current prosthetic principles, flexible non-metal clasp dentures are not recommended as definitive dentures, except for limited cases such as patients with a metal allergy. Rigid non-metal clasp dentures are recommended in cases where patients will not accept metal clasps for esthetic reasons. Non-metal clasp dentures should follow the same design principles as conventional RPDs using metal clasps. Copyright © 2013 Japan Prosthodontic Society. Published by Elsevier Ltd. All rights reserved.

  7. Transition from failing dentition to full-arch fixed implant-supported prosthesis with a staged approach using removable partial dentures: a case series.

    Science.gov (United States)

    Cortes, Arthur Rodriguez Gonzalez; Cortes, Djalma Nogueira; No-Cortes, Juliana; Arita, Emiko Saito

    2014-06-01

    The present retrospective case series is aimed at evaluating a staged approach using a removable partial denture (RPD) as an interim prosthesis in treatment to correct a failing dentition until such time as a full-arch fixed implant-supported prosthesis may be inserted. Eight patients, who had undergone maxillary full-arch rehabilitation with dental implants due to poor prognosis of their dentitions, were analyzed. All treatment included initial periodontal therapy and a strategic order of extraction of hopeless teeth. An RPD supported by selected teeth rehabilitated the compromised arch during implant osseointegration. These remaining teeth were extracted prior to definitive prosthesis delivery. Advantages and drawbacks of this technique were also recorded for the cases presented. Among the advantages provided by the staged approach are simplicity of fabrication, low cost, and ease of insertion. Additionally, RPD tooth support prevented contact between the interim prosthesis and healing abutments, promoting implant osseointegration. The main drawbacks were interference with speech and limited esthetic results. Implant survival rate was 100% within a follow-up of at least 1 year. The use of RPDs as interim prostheses allowed for the accomplishment of the analyzed rehabilitation treatments. It is a simple treatment alternative for patients with a low smile line. © 2013 by the American College of Prosthodontists.

  8. Zirconia-based dental crown to support a removable partial denture: a three-dimensional finite element analysis using contact elements and micro-CT data.

    Science.gov (United States)

    Rocha, Eduardo Passos; Anchieta, Rodolfo Bruniera; de Almeida, Erika Oliveira; Freitas, Amilcar Chagas; Martini, Ana Paula; Sotto-Maior, Bruno Sales; Luersen, Marco Antonio; Ko, Ching Chang

    2015-01-01

    Veneer fracture is the most common complication in zirconia-based restorations. The aim of this study was to evaluate the mechanical behavior of a zirconia-based crown in a lower canine tooth supporting removable partial denture (RPD) prosthesis, varying the bond quality of the veneer/coping interface. Microtomography (μCT) data of an extracted left lower canine were used to build the finite element model (M) varying the core material (gold core - MAu; zirconia core - MZi) and the quality of the veneer/core interface (complete bonded - MZi; incomplete bonded - MZi-NL). The incomplete bonding condition was only applied for zirconia coping by using contact elements (Target/Contact) with 0.3 frictional coefficients. Stress fields were obtained using Ansys Workbench 10.0. The loading condition (L = 1 N) was vertically applied at the base of the RPD prosthesis metallic support towards the dental apex. Maximum principal (σmax) and von Mises equivalent (σvM) stresses were obtained. The σmax (MPa) for the bonded condition was similar between gold and zirconia cores (MAu, 0.42; MZi, 0.40). The incomplete bonded condition (MZi-NL) raised σmax in the veneer up to 800% (3.23 MPa) in contrast to the bonded condition. The peak of σvM increased up to 270% in the MZi-NL. The incomplete bond condition increasing the stress in the veneer/zirconia interface.

  9. A treatment protocol for restoring occlusal vertical dimension using an overlay removable partial denture as an alternative to extensive fixed restorations: a clinical report.

    Science.gov (United States)

    Patel, Mit B; Bencharit, Sompop

    2009-10-30

    Treatment options for patients with severe attrition resulting in reduced occlusal vertical dimension are often limited to fixed prosthesis to reestablish proper occlusal vertical dimension and functional occlusion. In some cases such as when there are limited finances, minimal esthetic concerns, and medical considerations fixed prosthesis may not be the ideal treatment option. Overlay removable partial dentures (ORPDs) can be used as a provisional or interim prosthesis as well as permanent prosthesis in these cases. While ORPDs can provide a reversible and relatively inexpensive treatment for patients with a significantly compromised dental status, there is not much scientific evidence in the literature on ORPDs. Most studies published on ORPDs to date are primarily reviews and clinical reports. In this article, literatures on ORPDs are summarized and a patient treated with interim and permanent ORPDs is presented. This article reviews previously published literatures on the use of ORPDs. Indications, advantages and disadvantages are discussed. Treatment protocol with an example of the prosthodontic treatment of a patient with severely worn dentition with an interim ORPD and later a permanent ORPD are discussed in details.

  10. A Treatment Protocol for Restoring Occlusal Vertical Dimension Using an Overlay Removable Partial Denture as an Alternative to Extensive Fixed Restorations: A Clinical Report

    Science.gov (United States)

    Patel, Mit B; Bencharit, Sompop

    2009-01-01

    Treatment options for patients with severe attrition resulting in reduced occlusal vertical dimension are often limited to fixed prosthesis to reestablish proper occlusal vertical dimension and functional occlusion. In some cases such as when there are limited finances, minimal esthetic concerns, and medical considerations fixed prosthesis may not be the ideal treatment option. Overlay removable partial dentures (ORPDs) can be used as a provisional or interim prosthesis as well as permanent prosthesis in these cases. While ORPDs can provide a reversible and relatively inexpensive treatment for patients with a significantly compromised dental status, there is not much scientific evidence in the literature on ORPDs. Most studies published on ORPDs to date are primarily reviews and clinical reports. In this article, literatures on ORPDs are summarized and a patient treated with interim and permanent ORPDs is presented. This article reviews previously published literatures on the use of ORPDs. Indications, advantages and disadvantages are discussed. Treatment protocol with an example of the prosthodontic treatment of a patient with severely worn dentition with an interim ORPD and later a permanent ORPD are discussed in details. PMID:19915723

  11. Fit accuracy of metal partial removable dental prosthesis frameworks fabricated by traditional or light curing modeling material technique: An in vitro study

    Science.gov (United States)

    Anan, Mohammad Tarek M.; Al-Saadi, Mohannad H.

    2015-01-01

    Objective The aim of this study was to compare the fit accuracies of metal partial removable dental prosthesis (PRDP) frameworks fabricated by the traditional technique (TT) or the light-curing modeling material technique (LCMT). Materials and methods A metal model of a Kennedy class III modification 1 mandibular dental arch with two edentulous spaces of different spans, short and long, was used for the study. Thirty identical working casts were used to produce 15 PRDP frameworks each by TT and by LCMT. Every framework was transferred to a metal master cast to measure the gap between the metal base of the framework and the crest of the alveolar ridge of the cast. Gaps were measured at three points on each side by a USB digital intraoral camera at ×16.5 magnification. Images were transferred to a graphics editing program. A single examiner performed all measurements. The two-tailed t-test was performed at the 5% significance level. Results The mean gap value was significantly smaller in the LCMT group compared to the TT group. The mean value of the short edentulous span was significantly smaller than that of the long edentulous span in the LCMT group, whereas the opposite result was obtained in the TT group. Conclusion Within the limitations of this study, it can be concluded that the fit of the LCMT-fabricated frameworks was better than the fit of the TT-fabricated frameworks. The framework fit can differ according to the span of the edentate ridge and the fabrication technique for the metal framework. PMID:26236129

  12. Improvement of oral health-related quality-of-life by use of different kinds of double-crown-retained removable partial dentures.

    Science.gov (United States)

    Stober, Thomas; Danner, Daniel; Bömicke, Wolfgang; Hassel, Alexander J

    2016-01-01

    To verify the hypotheses that treatment with double-crown-retained removable partial dentures (RPDs) improves oral health-related quality-of life (OHRQoL) over a 36-month period and that the performance of RPDs retained by use of electroplated double crowns (EP-RPDs) was different to that of RPDs retained by use of cast double crowns (C-RPDs). Fifty-four patients (mean age = 64 years, 63% men) were recruited and randomly assigned to C-RPD or EP-RPD. OHRQoL was assessed pre-treatment, post-treatment and 6, 12, 24 and 36 months after insertion, by use of the oral health impact profile (OHIP). An unweighted total score was calculated (OHIP-SUM). A two-level hierarchical model was used for statistical analysis. First-level units were the measurements on the six occasions; second-level units were the patients. Improvement of OHRQoL was observed in both groups after treatment (t = 7.27, p < 0.001). Whereas a treatment-material interaction indicated that treatment with EP-RPDs resulted in greater immediate improvement of OHRQoL, a time-material interaction indicated that long-term improvement was greater for C-RPDs. Treatment with EP-RPDs and C-RPDs improved OHRQoL initially. Over a period of 36 months the effect was significant. The treatment is, therefore, a promising therapeutic option. The cast conical design seems to have advantages with regard to long-term OHRQoL.

  13. Unsplinted implants and teeth supporting maxillary removable partial dentures retained by telescopic crowns: a retrospective study with >6 years of follow-up.

    Science.gov (United States)

    Frisch, Eberhard; Ratka-Krüger, Petra; Wenz, Hans-Jürgen

    2015-09-01

    Data regarding tooth- and implant-supported maxillary removable partial dentures (TIRPDs) are scarce. The objective of this research was to perform a retrospective evaluation of the clinical long-term outcome of maxillary TIRPDs rigidly retained via telescopic crowns in patients undergoing supportive post-implant therapy (SIT). The inclusion criteria were met by 26 patients restored with maxillary TIRPDs between 1997 and 2011 in a private practice. Primary crowns (Marburg double crowns, MDCs) on teeth were cemented, whereas those on implants were screw-retained. Using patient records and data from a cross-sectional clinical examination in 2013, the survival rates of the teeth, implants and prostheses, together with the biological and technical complications, were analyzed. After 6.12 ± 3.80 (range: 2-16) years of loading, 23 non-smoking patients with 23 dentures supported by 60 implants and 66 teeth were available for assessment. Nine teeth (survival rate: 86.36%) were lost, whereas 1 implant (survival rate: 98.36%) failed because of peri-implantitis. Although 30 implants (50%) in 16 patients (69.57%) showed bleeding on probing (BOP+), no further peri-implantitis was observed. The mean peri-implant probing depth (PPD) was 3.68 ± 0.71 mm. All dentures were functional and required technical maintenance efforts amounting to 0.128 treatments per patient per year (T/P/Y). Within the limitations of this study, we conclude that TIRPDs retained via MDCs may represent a viable treatment option for patients with residual maxillary teeth. © 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  14. Falhas de grampos circunferenciais de próteses removíveis em função de ciclagens de flexão Removable partial denture clasp failure related to flexural cycling

    Directory of Open Access Journals (Sweden)

    Marco Antonio MELONCINI

    1998-07-01

    Full Text Available A finalidade da pesquisa foi a determinação da freqüência da perda de retenção de grampos de próteses removíveis. A freqüência foi determinada após os vários períodos de ciclagem (x103: 1, 5, 15, 25. O número de freqüências foi baseado no número de "células" vazias, ou inexistentes, por fratura de grampos ou presença de retenção menor que 120 g, quando era feito ajuste. Assim, o número de "células" vazias é caracterizado pelo número de grampos que se fraturaram ou perderam retenção. As variáveis foram: 4 ligas de metais básicos; 2 tipos de grampos (padrão e extra, mais fino; dentes pré-molar e molar. Os resultados permitiram concluir que: o número de "células" vazias depende das ligas, tanto com ajuste como sem; o número de falhas sem ajuste não foi dependente do tipo de grampo, porém, com ajuste, o extra apresentou menor freqüência de falhas; a freqüência de falhas foi muito grande; e quase a metade ocorreu até 1.000 ciclos.The purpose of this research was to study the frequency of retention loss of removable partial denture clasps. Loss of retention was determined after several cycling periods (initially zero, and 1, 5, 15 and 25 thousand. Frequency was based on the number of vacant spaces when the clasp failed by rupture or retention loss under 120g. Thus, the number of vacant spaces depends on the number of clasps fractured and/or that lost retention. Other variables were: four base metal alloys, two types of clasps (standard and extra, which was thinner, and two teeth (premolar and molar. The conclusions were that: the number of vacant spaces depends on alloys with or without adjustment; with adjustment the extra clasp presented less failures; frequency of clasp failures is very high and almost half occurred up to 1,000 cycles.

  15. Biosorption of hexavalent chromium in a tannery industry wastewater using fungi species

    Directory of Open Access Journals (Sweden)

    D. Sivakumar

    2016-03-01

    Full Text Available The isolated fungi species of different kinds from chromium contaminated soil sites located in Nagalkeni, Chennai were used for reducing chromium(VI in a tannery industry wastewater of Nagalkeni, Chennai.  The experiments were conducted to know biosorption potential of isolated fungi species for removing chromium(VI in a tannery industry wastewater against the different pH, fungi biomass and chromium(VI concentration (dilution ratio.  The results of this study indicated that the order of maximum removal of chromium(VI by an isolated fungi species at an optimum pH of 3, fungi biomass of 4g andan initial chromium(VI concentration of 18.125 mg/L (dilution ratio 4is A. niger > A. flavus > A. fumigatus > A. nidulans > A. heteromorphus > A. foetidus > A. viridinutans.  This study found that the maximum removal of chromium(VI was achieved by Aspergillus niger (96.3 % than other fungi species at chromium(VI concentration of 18.125 mg/Lin a tannery industry wastewater. The chromium removal from tannery industry wastewater was validated by checking chromium removal in an aqueous solution and by checking the removal efficiency of other parameters in a tannery industry wastewater using same isolated A. niger.  Biosorption model was proposed to simulate the experimental condition for removing chromium(VI in a tannery industry wastewater by all isolated fungi species. The R2 and  values of the proposed model predicted that the proposed biosorption model is very much useful for predicting the trend of reduction potential of chromium(VI in a tannery industry wastewater by all isolated fungi species.  This study suggested that one could select the type of fungi species, ion concentration level, selection of treatment period, quantity of biomass to be used, and pH level of the medium, to achieve the highest reduction of any toxic metals from any contaminated water, wastewater and soil environment.

  16. The removal of toxic metals from liquid effluents by ion exchange resins. Part IV: Chromium(III)/H+ /Lewatit SP112; La eliminación de metales tóxicos presentes en efluentes líquidos mediante resinas de cambio iónico. Parte IV: cromo(III)/H+/Lewatit SP112

    Energy Technology Data Exchange (ETDEWEB)

    Alguacil, F.J.

    2017-09-01

    This investigation presented results on the removal of chromium(III), from aqueous solution in the 0-5 pH range, using Lewatit SP112 cationic exchange resin. Several aspects affecting the ion exchange process were evaluated, including: the influence of the stirring speed, temperature, pH of the solution, resin dosage and aqueous ionic strength. The selectivity of the system was tested against the presence of other metals in the aqueous solution, whereas the removal of chromium(III) from solutions was compared with results obtained using multiwalled carbon nanotubes as adsorbents. From the batch experimental data, best fit of the results is obtained with the Langmuir model, whereas the ion exchange process is best explained by the pseudo-second order model, moreover, experimental data responded well to the film-diffusion controlled model. Elution of the chromium(III) loaded into the resin is well accomplished by the use of sodium hydroxide solutions. [Spanish] En este trabajo se presentan los resultados obtenidos en la eliminación de cromo(III) de disoluciones acuosas (pH 0-5) mediante la resina de intercambio catiónico Lewatit SP112. Se han investigado algunas variables que pueden afectar al sistema: influencia de la agitación, temperatura, pH y fuerza iónica del medio acuoso y cantidad de resina; también se ha investigado acerca de la selectividad del sistema cuando otros metales están presentes en el medio acuoso, comparándose los resultados de la eliminación del cromo(III) usando la resina con los resultados obtenidos cuando se emplea otro adsorbente como son los nanotubos de carbono de pared múltiple. Los resultados experimentales indican que la carga del cromo(III) en la resina responde mejor al modelo de Langmuir, mientras que los modelos cinéticos indican que la carga del metal en la resina responde al modelo de pseudo-segundo orden y difusión en la capa límite. La elución del cromo(III) se realiza con disoluciones de hidróxid.

  17. Chromium in Postmortem Material.

    Science.gov (United States)

    Dudek-Adamska, Danuta; Lech, Teresa; Konopka, Tomasz; Kościelniak, Paweł

    2018-04-17

    Recently, considerable attention has been paid to the negative effects caused by the presence and constant increase in concentration of heavy metals in the environment, as well as to the determination of their content in human biological samples. In this paper, the concentration of chromium in samples of blood and internal organs collected at autopsy from 21 female and 39 male non-occupationally exposed subjects is presented. Elemental analysis was carried out by an electrothermal atomic absorption spectrometer after microwave-assisted acid digestion. Reference ranges of chromium in the blood, brain, stomach, liver, kidneys, lungs, and heart (wet weight) in the population of Southern Poland were found to be 0.11-16.4 ng/mL, 4.7-136 ng/g, 6.1-76.4 ng/g, 11-506 ng/g, 2.9-298 ng/g, 13-798 ng/g, and 3.6-320 ng/g, respectively.

  18. Role of paramagnetic chromium in chromium(VI)-induced damage in cultured mammalian cells.

    OpenAIRE

    Sugiyama, M

    1994-01-01

    Chromium(VI) compounds are known to be potent toxic and carcinogenic agents. Because chromium(VI) is easily taken up by cells and is subsequently reduced to chromium(III), the formation of paramagnetic chromium such as chromium(V) and chromium(III) is believed to play a role in the adverse biological effects of chromium(VI) compounds. The present report, uses electron spin resonance (ESR) spectroscopy; the importance of the role of paramagnetic chromium in chromium(VI)-induced damage in intac...

  19. Specification for corrosion-resisting chromium and chromium-nickel steel covered welding electrodes

    International Nuclear Information System (INIS)

    Anon.

    1981-01-01

    This specification prescribes requirements for covered corrosion-resisting chromium and chromium-nickel steel electrodes. These electrodes are normally used for shielded metal arc welding, and include those alloy steels designated as corrosion or heat-resisting chromium and chromium-nickel steels, in which chromium exceeds 4.0% and nickel does not exceed 50.0%

  20. Specification for corrosion-resisting chromium and chromium-nickel steel covered welding electrodes

    International Nuclear Information System (INIS)

    Anon.

    1981-01-01

    This specification prescribes requirements for covered corrosion-resisting chromium and chromium-nickel steel electrodes. These electrodes are normally used for shielded metal arc welding, and include those alloy steels designated as corrosion or heat-resisting chromium and chromium-nickel steels, in which chromium exceeds 4.0 percent and nickel does not exceed 50.0 percent

  1. 29 CFR 1915.1026 - Chromium (VI).

    Science.gov (United States)

    2010-07-01

    ... 29 Labor 7 2010-07-01 2010-07-01 false Chromium (VI). 1915.1026 Section 1915.1026 Labor... § 1915.1026 Chromium (VI). (a) Scope. (1) This standard applies to occupational exposures to chromium (VI... cement; or (4) Where the employer has objective data demonstrating that a material containing chromium or...

  2. 29 CFR 1926.1126 - Chromium (VI).

    Science.gov (United States)

    2010-07-01

    ... 29 Labor 8 2010-07-01 2010-07-01 false Chromium (VI). 1926.1126 Section 1926.1126 Labor... Chromium (VI). (a) Scope. (1) This standard applies to occupational exposures to chromium (VI) in all forms... objective data demonstrating that a material containing chromium or a specific process, operation, or...

  3. On texture formation of chromium electrodeposits

    DEFF Research Database (Denmark)

    Nielsen, Christian Bergenstof; Leisner, Peter; Horsewell, Andy

    1998-01-01

    The microstructure, texture and hardness of electrodeposited hard, direct current (DC) chromium and pulsed reversed chromium has been investigated. These investigations suggest that the growth and texture of hard chromium is controlled by inhibition processes and reactions. Further, it has been...... established that codeposition of Cr2O3 nanoparticles is a general feature of DC chromium electrodeposition....

  4. 29 CFR 1910.1026 - Chromium (VI).

    Science.gov (United States)

    2010-07-01

    ... 29 Labor 6 2010-07-01 2010-07-01 false Chromium (VI). 1910.1026 Section 1910.1026 Labor... Chromium (VI). (a) Scope. (1) This standard applies to occupational exposures to chromium (VI) in all forms... objective data demonstrating that a material containing chromium or a specific process, operation, or...

  5. Agroindustrial Waste for Lead and Chromium Biosorption

    Directory of Open Access Journals (Sweden)

    Susana P. Boeykens

    2018-06-01

    Full Text Available There is a need to re-evaluate the residues generated in industrial processes for the production of new raw material, reducing the volume of waste. In this regard, the biosorption is a low-cost alternative method for treating effluents compared to conventional methods. The main objectives of this research were: the evaluation of the biosorbent capacity of six waste materials for the extraction of chromium(VI and lead(II ions from aqueous solutions and, the determination of the adsorption and kinetic parameters for the more efficient system. The materials evaluated were: peanut shell (Arachis hypagaea, sugarcane bagasse (Saccharum officinarum, avocado peel (Persea americana, pecan nutshell (Carya illinoinensis, wheat bran (Triticum aestivum and banana peel (Mussa paradisiaca. The highest percentage of lead removal was obtained with wheat bran (89%. For chromium, the percentage was generally much lower compared with lead for all tested biosorbents, the banana peel being the most efficient with a 10% removal. The models that better describe the adsorption processes were: Langmuir and Freundlich. The pseudo-second order kinetic model allowed obtaining the parameters for both systems. The equilibrium time, in both systems, was reached after 60 minutes. The study of Fourier Transformed Infrared spectra and the results of desorption experiments allowed to hypothesize on the mechanisms involved in the adsorption of these metals.

  6. Development of Alkaline Oxidative Dissolution Methods for Chromium (III) Compounds Present in Hanford Site Tank Sludges

    International Nuclear Information System (INIS)

    Krot, N.N.; Shilov, V.P.; Fedoseev, A.M.; Budantseva, N.A.; Nikonov, M.V.; Yusov, A.B.; Garnov, A.Yu.; Charushnikova, I.A.; Perminov, V.P.; Astafurova, L.N.; Lapitskaya, T.S.; Makarenkov, V.I.

    1999-01-01

    The high-level radioactive waste sludge in the underground storage tanks at the Hanford Site contains various chromium(III)solid phases. Dissolution and removal of chromium from tank waste sludges is desirable prior to high-level waste vitrification because increased volume is required to incorporate the residual chromium. Unfortunately, dissolution of chromium from the sludge to form Cr(OH) 4 - through treatment with heated NaOH solution (also used to dissolve aluminum phases and metathesize phosphates to sodium salts) generally has been unsuccessful in tests with both simulated and genuine Hanford waste sludges. Oxidative dissolution of the Cr(III) compounds to form soluble chromate has been proposed as an alternative chromium solid phase dissolution method and results of limited prior testing have been reported

  7. Chromium Distribution between Liquid Slag and Matte Phases

    Science.gov (United States)

    Eric, R. Hurman

    The distribution of chromium between liquid silicate slags and copper-iron-nickel matte phases encountered in electric smelting of PGM containing South African sulphide concentrates were experimentally studied under controlled partial pressures of oxygen and sulphur. The reported experiments were conducted under silica saturation through the use of silica crucibles. Seven representative slag compositions were equilibrated with a typical sulphur deficient matte containing 18% Ni, 11% Cu, 42% Fe and 29% S. The slag constituents varied in the following ranges: SiO2: 42-58%, Al2O3: 3.5-9.0%, Fe2O3: 13-21%, MgO: 15.6-25%, CaO: 2-15%, Cr2O3: 0.2-3.5%. The slag and matte samples were synthetically prepared from pure components. The chromium content of the two phases was analysed chemically. According to the present available results of this ongoing research it was found that the partition of chromium to the matte phase decreased with an increase in the partial pressures of both oxygen and sulphur where the value of the distribution coefficient of chromium between the matte and the slag phase varied from as low as 0.07 to as high as 5.5.

  8. Study of the Thermodynamics of Chromium(III) and Chromium(VI) Binding to Fe3O4 and MnFe2O4 nanoparticles

    Science.gov (United States)

    Luther, Steven; Brogfeld, Nathan; Kim, Jisoo; Parsons, J.G.

    2013-01-01

    Removal of chromium(III) or (VI) from aqueous solution was achieved using Fe3O4, and MnFe2O4 nanomaterials. The nanomaterials were synthesized using a precipitation method and characterized using XRD. The size of the nanomaterials was determined to be 22.4 ± 0.9 nm (Fe3O4) and 15.5 ± 0.5 nm (MnFe2O4). The optimal binding pH for chromium(III) and chromium(VI) were pH 6 and pH 3. Isotherm studies were performed, under light and dark conditions, to determine the capacity of the nanomaterials. The capacities for the light studies with MnFe2O4 and Fe3O4 were determined to be 7.189 and 10.63 mg/g, respectively, for chromium(III). The capacities for the light studies with MnFe2O4 and Fe3O4 were 3.21 and 3.46 mg/g, respectively, for chromium(VI). Under dark reaction conditions the binding of chromium(III) to the MnFe2O4 and Fe3O4 nanomaterials were 5.74 and 15.9 mg/g, respectively. The binding capacity for the binding of chromium(VI) to MnFe2O4 and Fe3O4 under dark reaction conditions were 3.87 and 8.54 mg/g, respectively. The thermodynamics for the reactions showed negative ΔG values, and positive ΔH values. The ΔS values were positive for the binding of chromium(III) and for chromium(VI) binding under dark reaction conditions. The ΔS values for chromium(VI) binding under the light reaction conditions were determined to be negative. PMID:23558081

  9. Design of a biofilter to reduce the contamination content by chromium generated in the industries of the leather tanning

    International Nuclear Information System (INIS)

    Higuera C, Oscar F; Arroyave L, Juan F; Florez G, Luis

    2009-01-01

    The industrial sector of the tanneries generates unloadings with high volumes of chromium concentrates. The chromium is used in this industry like tanning agent. The tanning of skins presents some difficulties with the use of chromium salts, must to the great amount of tanning agent that does not fix to the skin and finally unloading to the environment, in waste waters causing negative effects in the environment and to the human health. The object of this work is to provide an alternative for the Chromium removal of waste water from tannery using coffee leaf variety castle, coffee Arabica

  10. The effectiveness of Mendong plant (Fimbrystilis globulosa as a phytoremediator of soil contaminated with chromium of industrial waste

    Directory of Open Access Journals (Sweden)

    Pungky Ferina

    2017-07-01

    Full Text Available The textile industry produces sideline output in the form of dangerous waste. The textile industrial waste containing heavy metal, one of which is Chromium (Cr.  Chromium is very dangerous metal for environment, especially chromium hexavalent that has properties of soluble, carcinogenic, and toxic. The pollution of chromium in soil is a problem that the action to be taken with the technology of bioremediation. Phytoremediation of soil contaminated with chromium using Mendong plant (Fimbrystilis globulosa, combined with association of microorganisms Agrobacterium sp I3 and compost. This study was conducted in field experiment plots using a completely randomized block design. Data were analyzed using Anova followed by Duncan and correlation tests. The results showed that the Mendong plant was an effective phytoremediator of soil contaminated with chromium and it can be used as a chromium accumulator plant. The highest decrease of soil chromium content of 58.39% was observed on the combined artificial fertilizer, Agrobacterium sp I3 and Mendong plant treatment (P1B1T1. Removal effectiveness of chromium at the treatments using Mendong plant was higher than without the Mendong plant. Chromium uptake in shoots was higher than in roots of Mendong plant. Bioremediation increased the total bacterial colonies, decreased soil pH, and increased cation exchange capacity of the soil. The growth of the Mendong plant was in a good condition during the process of bioremediation.

  11. Interaction of propylene with reduced surface of chromium molybdate

    International Nuclear Information System (INIS)

    Konovalova, N.D.; Belokopytov, Yu.V.

    1978-01-01

    It has been found that reduction of oxidated chromium molybdate sample by propylene at 450 deg C does not change the form of energy surface heterogeneity and also practically does not effect activation desorption energy of C 3 H 6 . It is shown that oxygen of this catalyst volume is movable and is responsible for formation of products of C 3 H 6 partial oxidation (acetic aldehyde and acrolein) in the sample reduction by propylene

  12. Optimization of chromium and tannic acid bioremediation by Aspergillus niveus using Plackett-Burman design and response surface methodology.

    Science.gov (United States)

    Chaudhary, Prachi; Chhokar, Vinod; Choudhary, Pragati; Kumar, Anil; Beniwal, Vikas

    2017-11-14

    A chromium and tannic acid resistance fungal strain was isolated from tannery effluent, and identified as Aspergillus niveus MCC 1318 based on its rDNA gene sequence. The MIC (minimum inhibitory concentration) of the isolate against chromium and tannic acid was found to be 200 ppm and 5% respectively. Optimization of physiochemical parameters for biosorption of chromium and tannic acid degradation was carried out by Plackett-Burman design followed by response surface methodology (RSM). The maximum chromium removal and tannic acid degradation was found to be 92 and 68% respectively by A. niveus. Chromium removal and tannic acid degradation was increased up to 11 and 6% respectively after optimization. Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) was used to investigate biosorption phenomena.

  13. Influence of Partial Dam Removal on Change of Channel Morphology and Physical Habitats: A Case Study of Yu-Sheng River

    Science.gov (United States)

    Hao Weng, Chung; Yeh, Chao Hsien

    2017-04-01

    The rivers in Taiwan have the characteristic of large slope gradient and fast flow velocity caused by rugged terrain. And Taiwan often aces many typhoons which will bring large rainfall in the summer. In early Taiwan, river management was more focus on flood control, flood protection and disaster reduction. In recent years, the rise of ecological conservation awareness for the precious fish species brings spotlight on the Taiwan salmon (Oncorhynchus masou formosanus) which lives in the river section of this study. In order to make sure ecological corridor continuing, dam removal is the frequently discussed measure in recent years and its impact on environmental is also highly concerned. Since the dam removal may causes severe changes to the river channel, the action of dam removal needs careful evaluation. As one of the endangered species, Taiwan salmon is considered a national treasure of Taiwan and it was originally an offshore migration of the Pacific salmon. After the ice age and geographical isolation, it becomes as an unique subspecies of Taiwan and evolved into landlocked salmon. Now the Taiwan salmon habitats only exists in few upstream creeks and the total number of wild Taiwan salmon in 2015 was about 4,300. In order to expand the connectivity of the fish habitats in Chi-Jia-Wan creek basin, several dam removal projects had completed with good results. Therefore, this paper focuses on the dam removal of Yu-Sheng creek dam. In this paper, a digital elevation model (DEM) of about 1 kilometer channel of the Yu-Sheng creek dam is obtained by unmanned aerial vehicle (UAV). Using CCHE2D model, the simulation of dam removal will reveal the impact on channel morphology. After model parameter identification and verification, this study simulated the scenarios of three historical typhoon events with recurrence interval of two years, fifteen years, and three decades under four different patterns of dam removal to identify the the head erosion, flow pattern, and

  14. Sequestration of chromium by exopolysaccharides of Nostoc and Gloeocapsa from dilute aqueous solutions

    Energy Technology Data Exchange (ETDEWEB)

    Sharma, Mona [Department of Environmental Science and Engineering, Guru Jambheshwar University of Science and Technology, Hisar-125 001 (India); Kaushik, Anubha [Department of Environmental Science and Engineering, Guru Jambheshwar University of Science and Technology, Hisar-125 001 (India)], E-mail: aks_10@yahoo.com; Somvir,; Bala, Kiran; Kamra, Anjana [Department of Environmental Science and Engineering, Guru Jambheshwar University of Science and Technology, Hisar-125 001 (India)

    2008-09-15

    This article reports the chromium removal potential of exopolysaccharides (EPS) of two indigenously isolated cyanobacterial strains, Gloeocapsa calcarea and Nostoc punctiforme. The biosorption was studied by varying pH from 2 to 6 and initial chromium concentration from 5 to 20 mg/L to find out the optimized conditions for maximum chromium removal by EPS. Two equilibrium models, Langmuir and Freundlich, were used to explain these results. The Freundlich model was found to be better applicable to the experimental data as compared to Langmuir as inferred from high value of coefficient of determination whereas the optimal conditions were found to be same for the two (pH 2 and initial chromium concentration 20 mg/L). EPS production by the two strains was also studied which was found to be higher for Gloeocapsa. On the basis of experimental results and model parameters, it can be inferred that the EPS extracted from Nostoc has comparatively high biosorption capacity and can be utilized for the removal of chromium from dilute aqueous solution. Adsorption of chromium on EPS was further confirmed by surface morphology observed in scanning electron micrographs.

  15. Chromium(VI) bioremediation by probiotics.

    Science.gov (United States)

    Younan, Soraia; Sakita, Gabriel Z; Albuquerque, Talita R; Keller, Rogéria; Bremer-Neto, Hermann

    2016-09-01

    Chromium is a common mineral in the earth's crust and can be released into the environment from anthropogenic sources. Intake of hexavalent chromium (Cr(VI)) through drinking water and food causes toxic effects, leading to serious diseases, and is a commonly reported environmental problem. Microorganisms can mitigate or prevent the toxic effects caused by heavy metals in addition to having effective resistance mechanisms to prevent cell damage and bind to these metals, sequestering them from the cell surface and removing them from the body. Species of Lactobacillus, Streptococcus, Bacillus and Bifidobacterium present in the human mouth and gut and in fermented foods have the ability to bind and detoxify some of these substances. This review address the primary topics related to Cr(VI) poisoning in animals and humans and the use of probiotics as a way to mitigate or prevent the toxic effects caused by Cr(VI). Further advances in the genetic knowledge of such microorganisms may lead to discoveries which will clarify the most active microorganisms that act as bioprotectants in bodies exposed to Cr(VI) and are an affordable option for people and animals intoxicated by the oral route. © 2016 Society of Chemical Industry. © 2016 Society of Chemical Industry.

  16. Removal of trace metal contaminants from potable water by electrocoagulation

    OpenAIRE

    Heffron, Joe; Marhefke, Matt; Mayer, Brooke K.

    2016-01-01

    This study investigated the effects of four operational and environmental variables on the removal of trace metal contaminants from drinking water by electrocoagulation (EC). Removal efficiencies for five metals (arsenic, cadmium, chromium, lead and nickel) were compared under varying combinations of electrode material, post-treatment, water composition and pH. Iron electrodes out-performed aluminum electrodes in removing chromium and arsenic. At pH 6.5, aluminum electrodes were slightly more...

  17. Acute Severe Chromium Poisoning After Dermal Exposure to Hexavalent Chromium

    Directory of Open Access Journals (Sweden)

    Chun-Chi Lin

    2009-04-01

    Full Text Available Severe acute chromium poisoning related to dermal involvement has rarely been reported in the literature. We report a case of acute severe chromium poisoning through skin exposure as a result of a chemical burn of 15% of the body surface area and multiple organ failure after short-term exposure. Medical interventions, including mechanical ventilation, continuous venovenous hemofiltration, and plasmapheresis were performed. In addition, a chelating agent, dimercapto-propane sulfonic acid, was infused intravenously, combined with intravenous N-acetylcysteine and ascorbic acid as adjuvant therapy. The patient was discharged on day 33 without long-term sequelae. The consequence of transdermal exposure of hexavalent chromium should not be overlooked.

  18. Specification for corrosion-resisting chromium and chromium-nickel steel covered welding electrodes

    International Nuclear Information System (INIS)

    Anon.

    1983-01-01

    This specification prescribes requirements for covered corrosion-resisting chromium and chromium-nickel steel electrodes. These electrodes normally are used for shielded metal arc welding, and include those alloy steels designated as corrosion or heat-resisting chromium-nickel steels in which chromium exceeds 4.0 percent and nickel does not exceed 50.0 percent

  19. Chromium Salen Mediated Alkene Epoxidation

    DEFF Research Database (Denmark)

    Petersen, Kaare Brandt; Norrby, Per-Ola; Daly, Adrian M.

    2002-01-01

    The mechanism of alkene epoxidation by chromium(v) oxo salen complexes has been studied by DFT and experimental methods. The reaction is compared to the closely related Mn-catalyzed process in an attempt to understand the dramatic difference in selectivity between the two systems. Overall......, the studies show that the reactions have many similarities, but also a few critical differences. In agreement with experiment, the chromium system requires a change from low- to high-spin in the catalytic cycle, whereas the manganese system can proceed either with spin inversion or entirely on the high......-spin surface. The low-spin addition of metal oxo species to an alkene leads to an intermediate which forms epoxide either with a barrier on the low-spin surface or without a barrier after spin inversion. Supporting evidence for this intermediate was obtained by using vinylcyclopropane traps. The chromium...

  20. Adsorption of chromium(VI) on pomace-An olive oil industry waste: Batch and column studies

    International Nuclear Information System (INIS)

    Malkoc, Emine; Nuhoglu, Yasar; Dundar, Murat

    2006-01-01

    The waste pomace of olive oil factory (WPOOF) was tested for its ability to remove chromium(VI) from aqueous solution by batch and column experiments. Various thermodynamic parameters, such as ΔG o , ΔH o and ΔS o have been calculated. The thermodynamics of chromium(VI) ion onto WPOOF system indicates spontaneous and endothermic nature of the process. The ability of WPOOF to adsorb chromium(VI) in a fixed bed column was investigated, as well. The effect of operating parameters such as flow rate and inlet metal ion concentration on the sorption characteristics of WPOOF was investigated. The longest breakthrough time and maximum of Cr(VI) adsorption is obtained at pH 2.0. The total adsorbed quantities, equilibrium uptakes and total removal percents of chromium(VI) related to the effluent volumes were determined by evaluating the breakthrough curves obtained at different flow rates and different inlet chromium(VI) concentrations for adsorbent. The data confirmed that the total amount of sorbed chromium(VI) and equilibrium chromium(VI) uptake decreased with increasing flow rate and increased with increasing inlet chromium(VI) concentration. The Adams-Bohart model were used to analyze the experimental data and the model parameters were evaluated

  1. Chromium Uptake Efficiency of Spinacea olaracea from ...

    African Journals Online (AJOL)

    The aim of the study was to evaluate the uptake of chromium by Spinacea olaracea and its accumulation in roots and shoots of plants grown in pots at various concentrations of chromium (30, 60, 90,120,150 mg/l). The results revealed that the levels of chromium accumulation in roots and shoots were higher at minimum ...

  2. Chromium evaluation in work atmospheres in an industry of tanneries and one of galvanoplasty

    International Nuclear Information System (INIS)

    Agudelo V, Sonia; Duarte Martha

    1994-01-01

    In tannery and galvanoplasty industries situated in Bogota (Colombia) hexavalent chromium and total soluble chromium were determinate in air samples in order to evaluated occupational exposition and risks for the worker of these factories. Samples were collected by suction pumps located near the breathing space of workers using PVC filters as captors. Samples were collected following the methodology of partial consecutive periods. Determination of Cr (VI) was done calorimetrically. Total soluble chromium was determinate by flame atomic absorption, previous optimization of procedures. Results for tannery Cr (VI) are located in the range non-detectable to 9.4 /m3 total soluble chromium was found between non detectable and 74.0 /m3. Cr (VI) in galvanoplasty varies between non detectable and 500 /m3. Probability of occupational risk were found in tannery and galvanoplasty industries

  3. mechanism for partial oxidation of cyclohexene by chromium (vi)

    African Journals Online (AJOL)

    DJFLEX

    detection limit of the classical test but was detected by the IR spectroscopic test. The unsaturation detected by decolourisation of the permanganate may be from the allylic ketone. GC/MS Analysis of Cyclohexene Oxidation Products. The chromatogram gave eleven (11) distinct peaks. On comparing the MS spectrum of each ...

  4. Biosorption of hexavalent chromium (chromium (VI) ion from ...

    African Journals Online (AJOL)

    taye

    2015-04-01

    Apr 1, 2015 ... industrial discharges (Wang and Cheng, 2009). Hexavalent Chromium (Cr (VI) is a by-product released into the aquatic environment by many industrial activities such as leather tanning, chrome plating, stainless steel welding, pigment production and nuclear weapon production (Gonzalez et al., 2003).

  5. Environmental biochemistry of chromium.

    Science.gov (United States)

    Losi, M E; Amrhein, C; Frankenberger, W T

    1994-01-01

    Chromium is a d-block transitional element with many industrial uses. It occurs naturally in various crustal materials and is discharged to the environment as industrial waste. Although it can occur in a number of oxidation states, only 3+ and 6+ are found in environmental systems. The environmental behavior of Cr is largely a function of its oxidation state. Hexavalent Cr compounds (mainly chromates and dichromates) are considered toxic to a variety of terrestrial and aquatic organisms and are mobile in soil/water systems, much more so than trivalent Cr compounds. This is largely because of differing chemical properties: Hexavalent Cr compounds are strong oxidizers and highly soluble, while trivalent Cr compounds tend to form relatively inert precipitates at near-neutral pH. The trivalent state is generally considered to be the stable form in equilibrium with most soil/water systems. A diagram of the Cr cycle in soils and water is given in Fig. 6 (Bartlett 1991). This illustration provides a summary of environmentally relevant reactions. Beginning with hexavalent Cr that is released into the environment as industrial waste, there are a number of possible fates, including pollution of soil and surface water and leaching into groundwater, where it may remain stable and, in turn, can be taken up by plants or animals, and adsorption/precipitation, involving soil colloids and/or organic matter. Herein lies much of the environmental concern associated with the hexavalent form. A portion of the Cr(VI) will be reduced to the trivalent form by inorganic electron donors, such as Fe2+ and S2-, or by bioprocesses involving organic matter. Following this conversion, Cr3+ can be expected to precipitate as oxides and hydroxides or to form complexes with numerous ligands. This fraction includes a vast majority of global Cr reserves. Soluble Cr3+ complexes, such as those formed with citrate, can undergo oxidation when they come in contact with manganese dioxide, thus reforming

  6. Prótese parcial removível associada à prótese fixa adesiva através de encaixe extracoronário = Resin-bonded fixed dentures and extracoronal precision attachments in removable partial dentures

    Directory of Open Access Journals (Sweden)

    Cosme, Dúcia Caldas

    2005-01-01

    Full Text Available A prótese parcial removível é uma alternativa de reabilitação que tem como vantagem o pequeno desgaste dos dentes suportes, mas quando compromete os dentes anteriores apresenta um inconveniente estético que é o abraçamento de parte da face vestibular pelos retentores diretos. Para eliminar este efeito estético negativo indica-se o uso de prótese parcial fixa associada à removível através de encaixes, que apresenta a desvantagem biológica provocada pelo preparo dos dentes pilares. Desta forma, a associação de prótese parcial fixa adesiva à prótese parcial removível através de encaixes extracoronários confere uma combinação vantajosa sob os pontos de vista biológico, estético e biomecânico, uma vez que reúne os principais aspectos de ambos os tipos de reabilitação protética como mais uma alternativa de tratamento

  7. The electrochemistry of chromium, chromium-boron and chromium-phosphorus alloys

    International Nuclear Information System (INIS)

    Moffat, T.P.; Ruf, R.R.; Latanision, R.M.

    1987-01-01

    It is fairly well established that chromium-metalloid interactions represent the key to understanding the remarkable corrosion behavior of TM-Cr-M glasses; (Fe, Ni, Co,...)-Cr-(P, Si, C, S). The character and kinetics of passive film growth on the glasses are being studied ni order to assess the role of the film former, chromium, and the metalloids in the passivation process. A series of thin film microcrystalline chromium, Cr-B and Cr-P binary alloys have been fabricated by physical vapor deposition techniques. Vacuum melted conventionally processed chromium has also been studied. Examination of these materials in lM H/sub 2/SO/sub 4/ and lM HCl by voltammetry, potentiostatic and impedance techniques yields the following conclusion: 1. Pure chromium with a grain size varying from < 400 A to 0.5 mm exhibits no well defined differences in electrochemical behavior in lM H/sub 2/SO/sub 4/. 2. The tremendous corrosion resistance of Cr-B alloys has been confirmed. 3. The beneficial effects observed for boron alloyed with chromium may be considered surprising in view of the neutral/negative influence of alloying boron with iron, i.e. Fe/sub 80/B/sub 20/. 4. The interaction of the electrochemistry of the metalloid constituent with that of the transition base element determines the corrosion behavior. 5. Preliminary work with Cr-P alloys indicates that certain compositions exhibit promising properties - certain films were found to be intact after two days of immersion in concentrated HCl. Further work is in progress

  8. Iron-nickel-chromium alloys

    International Nuclear Information System (INIS)

    Karenko, M.K.

    1981-01-01

    A specification is given for iron-nickel-chromium age-hardenable alloys suitable for use in fast breeder reactor ducts and cladding, which utilize the gamma-double prime strengthening phase and are characterized in having a delta or eta phase distributed at or near grain boundaries. A range of compositions is given. (author)

  9. Chromium isotope uptake in carbonates

    DEFF Research Database (Denmark)

    Rodler, Alexandra

    Chromium (Cr) is a redox sensitive element potentially capable of tracing fine-scale fluctuations of the oxygenation of Earth’s early surface environments and seawater. The Cr isotope composition of carbonates could perhaps be used as paleo-redox proxy to elucidate changes in the geological past...

  10. Chromium Chemistry in the Subsurface

    Science.gov (United States)

    Chromium (VI) (Cr) is carcinogenic and a threat to human and ecological health. There are adequate and acceptable methods to characterize and assess Cr contaminated sites. Cr chemistry in the environment is well understood. There are documented methods to address Cr contaminat...

  11. Chemical phase separation in binary iron-chromium alloys

    International Nuclear Information System (INIS)

    Hawick, K.A.

    1992-01-01

    A study of chromium-enriched domain growth occurring in binary Fe-Cr alloys quenched from above to various temperatures within the miscibility gap has been made. This paper presents kinetic sequences of in-situ small angle neutron scattering (SANS) data for ageing times up to 75 hours on alloys containing 20, 20 and 40 atomic percent chromium. The SANS measurement are compared with partial structure functions obtained from computer simulations performed on a distributed array processor (DAP). The authors use a pair-potential lattice model, but simulate large systems containing up to 16 million lattice sites. The authors find good agreement between the scaled structure factors for our SANS data and computer simulated system

  12. Effect of recasting on the thickness of metal-ceramic interface of nickel-chromium and cobalt-chromium alloys

    Directory of Open Access Journals (Sweden)

    Mirković Nemanja

    2008-01-01

    Full Text Available Introduction/Aim. This research was done to establish recasting effects of nickel-chromium and cobalt-chromium alloys on the thickness of their metal-ceramic interface in making fixed partial dentures. Metal-ceramic interface determines their functional integrity and prevents damages on ceramics during mastication. Investigation of metal-ceramic samples is supposed to show if base metal alloys for metalceramics are successfully recycled without any risk of reduction of metal-ceramic interface thickness. Methods. The research was performed as an experimental study. Per six metal-ceramic samples of nickel-chromium alloy (Wiron99 and cobalt-chromium alloy (Wirobond C were made each. Alloy residues were recycled through twelve casting generations with the addition of 50% of new alloy on the occasion of every recasting. Analysis Energy Dispersive X-ray (EDX (Oxford Instruments and Scanning Electon Microscop (SEM analysis (JEOL were used to determine thickness of metal-ceramic interface together with PC Software for quantification of visual information's (KVI POPOVAC. Results. Results of this research introduced significant differences between thickness of metal-ceramic interface in every examined recycle generation. Recasting had negative effect on thickness of metal-ceramic interface of the examined alloys. This research showed almost linear reduction of elastic modulus up to the 12th generation of recycling. Conclusion. Recasting of nickel-chromium and cobaltchromium alloys is not recommended because of reduced thickness of metal-ceramic interface of these alloys. Instead of recycling, the alloy residues should be returned to the manufacturers.

  13. Adsorption of chromium onto activated alumina: kinetics and thermodynamics studies.

    Science.gov (United States)

    Marzouk, Ikhlass; Dammak, Lassaad; Hamrouni, Béchir

    2013-02-01

    In this study, the removal of chromium (VI) by adsorption on activated alumina was investigated and the results were fitted to Langmuir, Freundlich, Dubinin-Redushkevich, and Temkin adsorption models at various temperatures. The constants of each model were evaluated depending on temperature. Thermodynamic parameters for the adsorption system were determined at 10, 25 and 40 degrees C. (deltaH degrees = -21.18 kJ x mol(-1); deltaG degrees = -8.75 to -7.43 kJ x mol(-1) and deltaS degrees = -0.043 kJ x K(-1) x mol(-1)). The obtained values showed that chromium (VI) adsorption is a spontaneous and exothermic process. The kinetic process was evaluated by first-order, second-order and Elovich kinetic models.

  14. Biotransformation of chromium (VI) in liquid effluents by resistant bacteria isolated from the Matanza-Riachuelo basin, in Argentina.

    Science.gov (United States)

    González, Ana Julieta; Caimán, Carolina; Gorino, Natalia; Fortunato, María Susana; Radice, Marcela; Gómez, Carlos; Mujica, Carolina; Marquina, Lorena; Gallego, Alfredo; Korol, Sonia Edith

    2017-10-10

    The aims of this investigation were to evaluate the bacterial resistance to zinc, copper, chromium (VI) and lead in surface water streams from Buenos Aires, Argentina; to select a chromium-resistant strain able to remove the metal in batch process and to evaluate the potential of this strain to remove chromium (VI) in liquid effluents. Bacterial resistance to the metals was evaluated by determining the minimal inhibitory concentration. The kinetic of chromium (VI) removal by one of the resistant strains was studied in nutrient broth with 50 and 100 mg L -1 of the metal, as well as an effluent from an electroplating industry. High resistance to all the metals under study was observed in the bacterial communities of the Matanza-Riachuelo basin. A chromium-resistant strain was isolated and identified as Microbacterium sp. It was able to remove 50 and 100 mg L -1 of Cr (VI) in 36 and 66 h respectively, with efficiency higher than 99%. Experiments with liquid effluents showed the ability of the strain to transform 150 mg L -1 of the metal in 84 h, with efficiency higher than 99%. These results show the potential of this native strain for the treatment of liquid effluents that contain chromium (VI).

  15. Chromium in aqueous nitrate plutonium process streams: Corrosion of 316 stainless steel and chromium speciation

    International Nuclear Information System (INIS)

    Smith, W.H.; Purdy, G.

    1994-01-01

    According to the measurements made in this study, the only situation in which chromium (+6) could exist in a plutonium process solution is one in which a feed containing chromium is dissolved in a glass pot dissolver in high nitric acid concentration and at high temperature. But when the resulting feed is prepared for ion exchange, the chemical treatment reduces chromium to the +3 state. Any solution being processed through the evaporator will only contain chromium in the +3 state and any chromium salts remaining in the evaporator bottoms will be chromium +3 salts

  16. Spectroscopic analysis of chromium bioremediation products

    Science.gov (United States)

    Varadharajan, C.; Nico, P. S.; Yang, L.; Marcus, M. A.; Steefel, C.; Larsen, J. T.; Beller, H. R.; Brodie, E. L.

    2010-12-01

    Remediation of chromium contamination frequently involves reducing the toxic and soluble hexavalent form, Cr(VI), to the relatively harmless and mostly immobile trivalent state, Cr(III). The objective of this study is to identify the biogeochemical reactions that control in situ chromium reduction in the presence of different dominant electron acceptors, i.e., NO3-, Fe(III), and SO42-. It was hypothesized that indirect, abiotic reduction of Cr(VI) by reduced metabolic products [Fe(II) and sulfides] would dominate over direct enzymatic reduction by denitrifying, iron-reducing, or sulfate-reducing bacteria. It is further hypothesized that the enzymatic reduction of Cr(VI) would produce relatively pure chromium hydroxide precipitates, whereas indirect reduction would result in mixed Cr-Fe hydroxide solid phases. Flow-through columns containing homogenized sediments from the 100H site at Hanford, WA were subjected to nitrate-, sulfate- or iron-reducing conditions in the presence of 5 µM Cr(VI) and 5 mM lactate. Cr(VI) was depleted in the effluent solutions from the nitrate- and sulfate-reducing columns; however only a small amount of Cr(VI) was removed under iron-reducing conditions. Preliminary analysis of micro X-ray absorption spectra indicate that the untreated and iron-reducing column sediments contained pre-existing Cr in the form of primary minerals, e.g. chromite and/or Cr-bearing micas. However, there was an increase in the relative abundance of mixed-phase Cr-Fe hydroxides, i.e., Cr1-xFex(OH)3 in the nitrate- and sulfate-treated columns. A possible explanation for the observations is that the production of Fe(II) was enhanced under the nitrate- and sulfate- reducing conditions, and was most likely sulfide-driven in the latter case. The Fe(II) was subsequently available for reduction of Cr(VI) resulting in the mixed-phase precipitates. The results from the spectroscopic analysis support the hypothesis that Fe(II)-mediated Cr reduction prevails over direct

  17. Removal of Cr(VI) ions by sewage sludge compost biomass from aqueous solutions: Reduction to Cr(III) and biosorption

    Science.gov (United States)

    Chen, Huixia; Dou, Junfeng; Xu, Hongbin

    2017-12-01

    Sewage sludge compost biomass was used as a novel biosorbent to remove hexavalent chromium from water. Surface area analysis, scanning electron microscopy, fourier-transform infrared spectroscopy, energy-dispersive X-ray spectroscopy, and point zero charge was applied to study the microstructure, compositions and chemical bonding states of the biomass adsorbent. Effects of contact time, biomass dosage, agitation speed, pH, the initial concentration of Cr(VI) and Cr(Ⅲ) on its adsorption removal were also performed in the batch experiments. A model describing adsorption, desorption and reduction phenomena during the sorption process has been referenced to model Cr(VI) sorption onto sewage sludge compost biomass. The result of characterization test shows that adsorption of Cr(VI) onto sewage sludge compost biomass followed by the partial reduction to Cr(Ⅲ) by biomass groups such as hydroxyl, carboxyl, and amino groups. The absorption kinetics model in the description of adsorption-coupled reduction of Cr(VI) fits successfully the kinetic data obtained at different temperatures and describes the kinetics profile of total, hexavalent and trivalent chromium. The study shows that sewage sludge compost biomass could be used as a potential biosorbent for removal of hexavalent chromium from wastewaters.

  18. Biosorption of chromium from electroplating and galvanizing industrial effluents under extreme conditions using Chlorella vulgaris

    Directory of Open Access Journals (Sweden)

    G. Sibi

    2016-07-01

    Full Text Available Hexavalent chromium [Cr(VI] is a toxic oxidized form and an important metal pollutant in the water bodies. Biosorption of chromium(VI offers a potential alternative to conventional metal removal methods. Dried biomass of Chlorella vulgaris was used as biosorbent for the removal of Cr(VI from electroplating and galvanizing industry effluents as a function of biosorbent dosage, contact time, pH, salinity and initial metal ion concentration. Batch experiments were conducted for biosorption and the optimum conditions were 1 g/L biomass, 4 h contact time, pH 2 and 2.893 mS/cm of electrical conductivity. The chromium biosorption was strictly pH dependent with a maximum Cr removal of 63.2 mg/L at pH 2. Highest Cr removal at a concentration of 81.3 mg/L was observed at Electrical conductivity (EC value of 2.893 mS/cm. A comparison of Langmuir and Freundlich isotherm models revealed that Freundlich isotherm model fitted the experimental data based on R2, qmax and standard error values. The results suggest that C. vulgaris biomass could be considered a promising low-cost biosorbent for the removal of Cr(VI from electroplating and galvanizing industry effluents. Keywords: Biosorption, Chlorella vulgaris, Microalgae, Hexavalent chromium

  19. Responses of endogenous proline in rice seedlings under chromium exposure

    Directory of Open Access Journals (Sweden)

    X.Z. Yu

    2016-12-01

    Full Text Available Hydroponic experiments were performed to exam the dynamic change of endogenous proline in rice seedlings exposed to potassium chromate chromium (VI or chromium nitrate chromium (III. Although accumulation of both chromium species in rice seedlings was obvious, more chromium was detected in plant tissues of rice seedlings exposed to chromium (III than those in chromium (VI, majority being in roots rather than shoots. Results also showed that the accumulation capacity of chromium by rice seedlings was positively correlated to chromium concentrations supplied in both chromium variants and the accumulation curve depicted an exponential trend in both chromium treatments over the entire period of exposure. Proline assays showed that both chromium variants induced the change of endogenous proline in shoots and roots of rice seedlings. Chromium (VI of 12.8 mg/L increased proline content significantly (p

  20. Synthesis of chromium containing pigments from chromium galvanic sludges

    International Nuclear Information System (INIS)

    Andreola, F.; Barbieri, L.; Bondioli, F.; Cannio, M.; Ferrari, A.M.; Lancellotti, I.

    2008-01-01

    In this work the screening results of the scientific activity conducted on laboratory scale to valorise chromium(III) contained in the galvanic sludge as chromium precursor for ceramic pigments are reported. The valorisation of this waste as a secondary raw material (SRM) is obtained by achievement of thermal and chemical stable crystal structures able to color ceramic material. Two different pigments pink CaCr 0.04 Sn 0.97 SiO 5 and green Ca 3 Cr 2 (SiO 4 ) 3 were synthesized by solid-state reactions using dried Cr sludge as chromium oxide precursor. The obtained pigments were characterized by X-ray diffraction and SEM analysis. Furthermore the color developed in a suitable ceramic glaze was investigated in comparison with the color developed by the pigments prepared from pure Cr 2 O 3 . The characterization carried out corroborates the thermal and chemical stability of the synthesized pigments and, especially for the Cr-Sn pink pigment, the powders develop an intense color that is very similar to the color developed by the pigments obtained starting from pure Cr 2 O 3

  1. Evaluation of chromium speciation and transport characteristics in the Hanford Site 100D and 100H areas

    International Nuclear Information System (INIS)

    Thornton, E.C.; Amonette, J.E.; Olivier, J.

    1995-08-01

    Field and laboratory investigations have been conducted to define the fate and transport characteristics of chromium contamination present in the 100D/H Areas of the Hanford Site. This information is relevant to assessing the impact of the release of hexavalent chromium to the Columbia River. Included in this study was the determination of the concentration and aqueous speciation of chromium in the unconfined acquifer and an assessment of potential changes in speciation as groundwater passes through the river/acquifer transition zone and mixes with the Columbia River. The results of this study indicate that chromium present within the Hanford acquifer is predominantly in the oxidized hexavalent state. Chromium is apparently stable in the oxidized form owing to its lack of organic matter within the acquifer. A portion of the chromium is removed as groundwater passes through the transition zone due to reduction and precipitation associated with sediment/water interaction processes. Chemical data collected from seep water samples, however, suggests, that most of the hexavalent chromium ultimately discharges into the Columbia River. Dilution of hexavalent chromium subsequently occurs during the mixing of groundwater and river water, with relatively little change taking place in speciation

  2. New ceramics incorporated with industrial by-products as pore formers for sorption of toxic chromium from aqueous media

    Science.gov (United States)

    Domopoulou, Artemi

    2015-04-01

    The incorporation of secondary resources including various industrial wastes as pore-forming agents into clayey raw material mixtures for the development of tailored porous ceramic microstructures is currently of increasing interest. In the present research, sintered ceramic compacts were developed incorporated with industrial solid by-products as pore formers, and then used as new sorbents for chromium removal from aqueous media. The microstructures obtained were characterized through X-ray diffraction (XRD) analysis as well as scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectrometry (EDX). Sorption potential of chromium from synthetic solutions on the porous ceramics was studied by static adsorption experiments as a function of the pore-former percentage in the ceramic matrix as well as the initial heavy metal (chromium) concentration, solution pH and temperature. Kinetic studies were conducted and adsorption isotherms of chromium were determined using the Langmuir equation. Preliminary experimental results concerning the adsorption characteristics of chromium on the ceramic materials produced appear encouraging for their possible beneficial use as new sorbents for the removal of toxic chromium from aqueous media. Keywords: sorbents, ceramics, industrial solid by-products, pore-former, chromium. Acknowledgements: This research has been co-financed by the European Union (European Social Fund - ESF) and Greek national funds through the Operational Program "Education and Lifelong Learning" of the National Strategic Reference Framework (NSRF) - Research Funding Program ARCHIMEDES III: Investing in knowledge society through the European Social Fund.

  3. Carbon, chromium and molybdenum contents

    International Nuclear Information System (INIS)

    Sinatora, A; Goldenstein, H.; Mei, P.R.; Albertin, E.; Fuoco, R.; Mariotto, C.L.

    1992-01-01

    This work describes solidification experiments on white cast iron, with 15 and 20% of chromium, 2.3, 3.0 and 3.6 % of carbon and 0.0, 1.5 and 2.5 % of molybdenum in test de samples with 30 mm diameter. Measurements were performed on the austenite and eutectic formation arrests, the number of the eutectic carbide particles relative to the total and the eutectic volumes, and the volume fraction of the primary austenite

  4. Inoculation of chromium white cast iron

    Directory of Open Access Journals (Sweden)

    D. Kopyciński

    2009-01-01

    Full Text Available It has been proved that an addition of boron carbide introduced as an inoculant to the chromium white cast iron changes the structureof castings. Castings after inoculation revealed a different structure with numerous grains. Primary precipitates of chromium carbide also appeared, reducing the mechanical properties of as-cast parts. Properly established heat treatment regime makes chromium iron castings regain their, originally high, mechanical properties.

  5. A homoleptic chromium(iii) carboxylate.

    Science.gov (United States)

    Sydora, O L; Hart, R T; Eckert, N A; Martinez Baez, E; Clark, A E; Benmore, C J

    2018-04-03

    Structurally characterized chromium(iii) carboxylates form clusters with a variety of bridging groups introduced from aqueous reaction conditions. The first homoleptic monomeric chromium(iii) carboxylate has been prepared using an anhydrous salt metathesis synthetic route. The carboxylate groups coordinate the chromium in a bidentate chelate yielding an aliphatic soluble complex. The complex was characterized by a variety of methods including high energy X-ray diffraction, FD-MS, IR and Raman spectroscopy, complemented by DFT modeling.

  6. Peat and coconut fiber as biofilters for chromium adsorption from contaminated wastewaters.

    Science.gov (United States)

    Henryk, Kołoczek; Jarosław, Chwastowski; Witold, Żukowski

    2016-01-01

    Batch adsorption experiments were performed for the removal of chromium (III) and chromium (VI) ions from aqueous solutions using Canadian peat and coconut fiber. The Langmuir model was used to describe the adsorption isotherm. The maximum adsorption for peat reached 18.75 mg/g for Cr(III) and 8.02 mg/g for Cr(VI), whereas the value for fiber was slightly higher and reached 19.21 mg/g for Cr(III) and 9.54 mg/g for Cr(VI). Both chromium forms could be easily eluted from the materials. The adsorption of chromium forms to organic matter could be explained in terms of formation of donor-acceptor chemical covalent bound with hydroxyl groups as ligands and chromium as the central atom in the formed complex. The chromate-reducing activities were monitored with the use of electron paramagnetic resonance spectroscopy. The results showed that both adsorption and reduction occurred simultaneously and the maximum adsorption capacity of hexavalent chromium being equal to 95% for fiber and 92% for peat was obtained at pH 1.5. The reduction of Cr(VI) in wastewaters began immediately and disappeared after 20 h. Both materials contained yeast and fungi species which can be responsible for reduction of chromium compounds, due to their enzymatic activity (Chwastowski and Koloczek (Acta Biochim Pol 60: 829-834, 2013)). The reduction of Cr(VI) is a two-phase process, the first phase being rapid and based on chemical reaction and the second phase having biological features. After the recovery step, both types of organic materials can be used again for chromium adsorption without any loss in the metal uptake. Both of the materials could be used as biofilters in the wastewater treatment plants.

  7. Serum chromium concentrations in type 2 diabetic patients attending ...

    African Journals Online (AJOL)

    FPG). Lower serum chromium concentrations and poor chromium status are common in type 2 diabetics in Osogbo, Nigeria. Keywords: Diabetes, serum chromium, glucose tolerance, insulin. International Journal of Natural and Applied Sciences ...

  8. Recovery of Chromium Ions From Electroplating Wastewater by Flotation, Gamma Irradiation and Adsorption onto Hydrogels

    International Nuclear Information System (INIS)

    Eid, M.; Dessouki, A.M.; Omar, A.M.

    2005-01-01

    At present, the wastewater treatment facilities in many plating plants are approaching their time for replacement. On this occasion there is a strong requirement to re-evaluate the wastewater treatment measures from the point of view of treatment technology. Laboratory investigation was undertaken on the flotation of Cr (VI) from aqueous suspension over whole ph range, aiming at the separation of chromium by flotation. The cationic surfactant (hexadecyl triethyl ammonium bromide) was applied as a collector. Surface properties, in particular the critical micelle concentration, the effectiveness of surface tension reduction, efficiency, surface excess and the minimum surface area were measured at 30 μ C. The electro-flotation was applied with and without the collector at different times for the removal of chromium (VI). The results were discussed in term of surface properties of the collectors at the solution/air interface. Further work took place by irradiating the water samples by gamma- irradiation to reduce the highly toxic Cr(VI) to the much less toxic and less soluble Cr1 in water; therefore, there is a potential for the complete removal of chromium from aqueous solutions. The possibility of using hydrogels for the uptake of irradiated chromium solutions by different hydrogels was investigated. The structure of the hydrogels was estimated by using FT1R and the pore structure of the hydrogels before and after dictating with chromium ions was monitored by SEM. The adsorption studies show that, it is ph dependent. Lowering of the chromium concentration below the maximum permissible value have been achieved after the treatment of chromium solution by flotation, gamma irradiation and adsorption onto hydrogels

  9. A comparative study of sorption of chromium (III) onto chitin and chitosan

    Science.gov (United States)

    Singh, Pooja; Nagendran, R.

    2016-06-01

    Heavy metals have always been the most hazardous components in the wastewater of industries like electroplating, automobiles, mining facilities and fertilizer manufacturers. Treatment of heavy metal laden wastewater requires expensive operational and maintenance systems. Food processing industries create a huge amount of shell waste which is sold to poultry farms in powdered form but the quantity thus used is still not comparable to the left over waste. The shell contains chitin which acts as an adsorbent for the heavy metals and can be used to treat heavy metal wastewater. The paper presents a study on the use of chitin and its processed product, chitosan, to remove chromium. Shake flask experiment was conducted to compare the adsorptive capacity of chitin and chitosan for chromium removal from simulated solution and isotherm studies were carried out. The studies showed that the chitosan was a better adsorbent than chitin. Both chitin and chitosan gave best adsorption results at pH 3. Chitin exhibited maximum chromium removal of 49.98 % in 20 min, whereas chitosan showed 50 % removal efficiency at a contact time of 20 min showing higher adsorptive capacity for chromium than chitin. The Langmiur and Freundlich isotherm studies showed very good adsorption capacity and monolayer interaction according to the regression coefficient 0.973 for chitosan and 0.915 for chitin. The regression coefficient for Freundlich isotherm was 0.894 and 0.831 for chitosan and chitin, respectively.

  10. Chromium VI adsorption on cerium oxide nanoparticles and morphology changes during the process

    Energy Technology Data Exchange (ETDEWEB)

    Recillas, Sonia; Colon, Joan [Department of Chemical Engineering, Engineering School, Autonomous University of Barcelona, 08193 Bellaterra (Spain); Casals, Eudald; Gonzalez, Edgar [Catalan Institute of Nanotechnology, Autonomous University of Barcelona Campus, 08193 Bellaterra (Spain); Puntes, Victor [Catalan Institute of Nanotechnology, Autonomous University of Barcelona Campus, 08193 Bellaterra (Spain); Catalan Institute of Research and Advanced Studies, Passeig Lluis Companys, 23, 08010 Barcelona (Spain); Sanchez, Antoni, E-mail: antoni.sanchez@uab.cat [Department of Chemical Engineering, Engineering School, Autonomous University of Barcelona, 08193 Bellaterra (Spain); Font, Xavier [Department of Chemical Engineering, Engineering School, Autonomous University of Barcelona, 08193 Bellaterra (Spain)

    2010-12-15

    In this study, suspended cerium oxide nanoparticles stabilized with hexamethylenetetramine were used for the removal of dissolved chromium VI in pure water. Several concentrations of adsorbent and adsorbate were tested, trying to cover a large range of possible real conditions. Results showed that the Freundlich isotherm represented well the adsorption equilibrium reached between nanoparticles and chromium, whereas adsorption kinetics could be modeled by a pseudo-second-order expression. The separation of chromium-cerium nanoparticles from the medium and the desorption of chromium using sodium hydroxide without cerium losses was obtained. Nanoparticles agglomeration and morphological changes during the adsorption-desorption process were observed by TEM. Another remarkable result obtained in this study is the low toxicity in the water treated by nanoparticles measured by the Microtox commercial method. These results can be used to propose this treatment sequence for a clean and simple removal of drinking water or wastewater re-use when a high toxicity heavy metal such as chromium VI is the responsible for water pollution.

  11. Laboratory scale electrokinetic remediation of hexavalent chromium from contaminated soil

    International Nuclear Information System (INIS)

    Khalid, M.; Ahmed, N.

    2008-01-01

    Pakistan hosts a variety of waste soils around industrial sites located in and around large population centers. Clean up of these waste soils is essential to save potable groundwater reserves beneath these waste soils. Among several waste remediation approaches, the electrokinetic remediation (EKR) technology has fast emerged as a reliable, powerful and highly prominent candidate for effective in situ removal of soluble and leachable toxic species of metals, radionuclides, organics from contaminated soils and water environment. This paper presents results of the first laboratory trial experiment performed at PINSTECH, Islamabad, Pakistan to demonstrate applicability of EKR approach for removal of aqueous phase chromium from silty clay soil around Islamabad. The electro osmotic flow rate was 3.13 ml/hour while the mass balance calculations revealed that the removal efficiency of Cr(VI) was 44.58% for the experimental soil during a period of 24 hours of electro remediation. (author)

  12. Bioremediation of the Soils Contaminated with Cadmium and Chromium, by the Earthworm Eisenia fetida

    Directory of Open Access Journals (Sweden)

    Elham Aseman- Bashiz1

    2014-07-01

    Full Text Available One of the most important environmental problems in the world is the soils contamination by heavy metals in the industrial areas, and especially the contamination of the agricultural lands. The use of earthworms to bioremediate the soils results in reducing the pollutants concentration through a bioaccumulation mechanism on the contaminants in the earthworm's body. Hence, the present study aimed to prove the biological effectiveness of Eisenia fetida earthworms in bioremediation the soils contaminated with chromium and cadmium. Concentration of chromium and cadmium pollution in soil was determined to be 0.04 mg/g and 0.08 mg/g respectively. 30 worms were added to 500 g soil samples. Chromium and cadmium concentration in soil and in the body of worms was measured at two time periods of 21 and 42 days. To measure the concentration of chromium and cadmium we used ICP spectrometry. Software in usage was SPSS version 17. There was a significant correlation between the reduction of chromium and cadmium metals in the soils and the accumulation of chromium and cadmium metals in the worm’s body. A significant decline of chromium levels of the soil was observed in the days 21 and 42 during the study compared to initial amount of 0.1 mg/g. on the other hand chromium concentration of the soil decreased from 0.14 mg/g to 0.1 mg/g after 42 days. Comparison of mortality in two different time periods showed that by passing the time and by increase in soil chromium and cadmium concentrations the death toll of worms rises. The increased mortality of worms in the soil at a concentration of 0.08 mg/g of chromium, say that using the worms for bioremediation is not recommended at such concentration of chromium but using the worms for the removal of cadmium at concentrations of 0.04 mg/g and 0.08 mg/g in the soil is recommended.

  13. Enhanced sludge processing of HLW: Hydrothermal oxidation of chromium, technetium, and complexants by nitrate. 1997 mid-year progress report

    International Nuclear Information System (INIS)

    Buelow, S.

    1997-01-01

    'Treatment of High Level Waste (HLW) is the second most costly problem identified by OEM. In order to minimize costs of disposal, the volume of HLW requiring vitrification and long term storage must be reduced. Methods for efficient separation of chromium from waste sludges, such as the Hanford Tank Wastes (HTW), are key to achieving this goal since the allowed level of chromium in high level glass controls waste loading. At concentrations above 0.5 to 1.0 wt.% chromium prevents proper vitrification of the waste. Chromium in sludges most likely exists as extremely insoluble oxides and minerals, with chromium in the plus III oxidation state [1]. In order to solubilize and separate it from other sludge components, Cr(III) must be oxidized to the more soluble Cr(VI) state. Efficient separation of chromium from HLW could produce an estimated savings of $3.4B[2]. Additionally, the efficient separation of technetium [3], TRU, and other metals may require the reformulation of solids to free trapped species as well as the destruction of organic complexants. New chemical processes are needed to separate chromium and other metals from tank wastes. Ideally they should not utilize additional reagents which would increase waste volume or require subsequent removal. The goal of this project is to apply hydrothermal processing for enhanced chromium separation from HLW sludges. Initially, the authors seek to develop a fundamental understanding of chromium speciation, oxidation/reduction and dissolution kinetics, reaction mechanisms, and transport properties under hydrothermal conditions in both simple and complex salt solutions. The authors also wish to evaluate the potential of hydrothermal processing for enhanced separations of technetium and TRU by examining technetium and TRU speciation at hydrothermal conditions optimal for chromium dissolution.'

  14. Partial priapism

    DEFF Research Database (Denmark)

    Høyerup, Peter; Dahl, Claus; Azawi, Nessn Htum

    2014-01-01

    Partial priapism, also called partial segmental thrombosis of the corpus cavernosum, is a rare urological condition. Factors such as bicycle riding, drug usage, penile trauma and haematological diseases have been associated with the condition. Medical treatment with low molecular weight heparin (...... (LMWH) or acetylsalicylic acid is first choice treatment, and surgery is preserved for patients unresponsive to analgesics. In this report we describe the case of a 70-year-old man with partial priapism after blood transfusions treated successfully with LMWH....

  15. Chromium in aqueous nitrate plutonium process streams: Corrosion of 316 stainless steel and chromium speciation

    International Nuclear Information System (INIS)

    Smith, W.H.; Purdy, G.M.

    1995-01-01

    This study was undertaken to determine if chromium(+6) could exist in plutonium process solutions under normal operating conditions. Four individual reactions were studied: the rate of dissolution of stainless steel, which is the principal source of chromium in process solutions; the rate of oxidation of chromium(+3) to chromium(+6) by nitric acid; and the reduction of chromium(+6) back to chromium(+3) by reaction with stainless steel and with oxalic acid. The stainless steel corrosion rate was found to increase with increasing nitric acid concentration, increasing hydrofluoric acid concentration, and increasing temperature. Oxidation of chromium(+3) to chromium(+6) was negligible at room temperature and only became significant in hot concentrated nitric acid. The rate of reduction of chromium(+6) back to chromium(+3) by reaction with stainless steel or oxalic acid was found to be much greater than the rate of the reverse oxidation reaction. Based on these findings and taking into account normal operating conditions, it was determined that although there would be considerable chromium in plutonium process streams it would rarely be found in the (+6) oxidation state and would not exist in the (+6) state in the final process waste solutions

  16. Chromium in aqueous nitrate plutonium process streams: Corrosion of 316 stainless steel and chromium speciation

    International Nuclear Information System (INIS)

    Smith, W.H.; Purdy, G.

    1995-01-01

    This study was undertaken to determine if chromium +6 could exist in plutonium process solutions under normal operating conditions. Four individual reactions were studied: the rate of dissolution of stainless steel, which is the principal source of chromium in process solutions; the rate of oxidation of chromium +3 to chromium +6 by nitric. acid; and the reduction of chromium +6 back to chromium +3 by reaction with stainless steel and with oxalic acid. The stainless steel corrosion rate was found to increase with increasing nitric acid concentration, increasing hydrofluoric acid concentration, and increasing temperature. Oxidation of chromium +3 to chromium +6 was negligible at room temperature and only became significant in hot concentrated nitric acid. The rate of reduction of chromium +6 back to chromium +3 by reaction with stainless steel or oxalic acid was found to be much greater than the rate of the reverse oxidation reaction. Based on these findings and taking into account normal operating conditions, it was determined that although there would be considerable chromium in plutonium process streams it would rarely be found in the +6 oxidation state and would not exist in the +6 state in the final process waste solutions

  17. Roentgenoelectronic investigation into oxidation of iron-chromium and iron-chromium-nickel alloys

    International Nuclear Information System (INIS)

    Akimov, A.G.; Rozenfel'd, I.L.; Kazanskij, L.P.; Machavariani, G.V.

    1978-01-01

    Kinetics of iron-chromium and iron-chromium-nickel alloy oxidation (of the Kh13 and Kh18N10T steels) in oxygen was investigated using X-ray electron spectroscopy. It was found that according to X-ray electron spectra chromium oxidation kinetics in the iron-chromium alloy differs significantly from oxidation kinetics of chromium pattern. Layer by layer X-ray electron analysis showed that chromium is subjected to a deeper oxidation as compared to iron, and accordingly, Cr 2 O 3 layer with pure iron impregnations is placed between the layer of mixed oxide (Fe 3 O 4 +Cr 2 O 3 ) and metal. A model of the iron-chromium alloy surface is suggested. The mixed oxide composition on the steel surface is presented as spinel Fesub(2+x)Crsub(1-x)Osub(y)

  18. Removal of hexavalent chromium using chitosan prepared from ...

    African Journals Online (AJOL)

    Thus, in this work, the main concern has been the preparation of chitin and chitosan from the raw materials of shrimp shells and the characterization of the prepared chitosan by field emission scanning electron microscopy (FESEM) and Fourier transform infrared spectroscopy (FTIR). The work was then shifted to investigate ...

  19. Evaluation of selected wetland plants for removal of chromium from ...

    African Journals Online (AJOL)

    user

    demand (COD), biochemical oxygen demand (BOD) and nitrogen under a 5 day hydraulic retention time were analyzed based on HACH manual. The Cr in the plant tissue was analyzed through .... measured for five days of hydraulic retention time (HRT) using a stopwatch and measuring cylinder (Figure 1). The wastewater ...

  20. Removal of chromium and nickel ions from aqueous solution by ...

    African Journals Online (AJOL)

    The study investigated the adsorption of Cr(VI) and Ni(II) on modified coconut husk (low cost adsorbent) for the remediation of Cr(VI) and Ni(II) from some synthetic industrial waste effluents. The coconut husk was modified by mixing with 0.1 M NaOH and HCl respectively. The effects of varying adsorbent loading, hydrogen ...

  1. OPTIMIZATION OF NICKEL (II) AND CHROMIUM (III) REMOVAL ...

    African Journals Online (AJOL)

    RSM)was used to study the effect of three adsorption variables (pH, initial concentration, and adsorbent dosage) in order to determine the optimum process conditions for the adsorptions of Ni (II) and Cr (III) onto sulphuric acid modified sorghum ...

  2. Removal of chromium ion from leather industrial wastes by activated ...

    African Journals Online (AJOL)

    293 – 323 K). The adsorption of Cr from industrial wastage was found to be exothermic. Thermodynamic parameters such as free energy (G°), enthalpy (H°) and entropy (S°) of adsorption was also calculated and interpreted from the slope and ...

  3. Removal of chromium and nickel ions from aqueous solution by ...

    African Journals Online (AJOL)

    EJIRO

    adsorbent loading, hydrogen ion concentration, contact time and temperature of adsorption were ... The adverse effects caused by these heavy metals are of ... It is highly mobile in soil and aquatic system and is a strong oxidant capable of being adsorbed by the skin (Singh and Singh,. *Corresponding author. E-mail: ...

  4. Selective removal of chromium (VI) from sulphates and other metal ...

    African Journals Online (AJOL)

    Leaching of the chromate template from the polymer particles was achieved with successive stirring of the ion-imprinted polymer (IIP) particles in 4 M HNO3 solutions to obtain leached materials, which were then ... Despite the method's very low detection limits for direct injection (below 1 μg∙ℓ-1), no Cr (VI) was obtained.

  5. Removal of chromium and lead from drill cuttings using activated ...

    African Journals Online (AJOL)

    user

    2009-07-14

    Jul 14, 2009 ... disposal of drill cuttings normally requires transport of the cuttings to a suitable landfill or shore-based processing system. Presently in Nigeria, drill ..... Kinetics and Thermodynamic Study of Lead Adsorption onto Acti- vated Carbon from Coconut and Sea Hull of the Palm Tree. J. Environ. Sci and Tech.

  6. Removal of hexavalent chromium using chitosan prepared from ...

    African Journals Online (AJOL)

    sunny t

    III) and the hexavalent Cr(VI) species, although there are various .... Afr. J. Biotechnol. 6(25):2924-2931. Benhabiles M S, Drouiche N, Lounici H, Pauss A, Mameri N (2013a). Effect of shrimp chitosan coatings as affected by chitosan extraction.

  7. Removal of Lead and Chromium from Aqueous Solution onto ...

    African Journals Online (AJOL)

    The maximum adsorption capacity Qe was found to be 34.48 and 16.13 mg/g for Pb (II) and Cr (VI), respectively. The Langmuir isotherm model showed a better fit to the equilibrium data than the Freundlich isotherm model. The mechanism of adsorption for both metal ions onto the FPAC agrees well with pseudo second ...

  8. Chromium tolerance and reduction potential of Staphylococci ...

    African Journals Online (AJOL)

    In order to study the microbiology of chromium tolerance and reduction at a fly ash dumping site in South Africa, 15 core samples were investigated. It was shown that the 30 year old dumping site exhibited high concentrations of Cr (VI) ranging from 1.6 to 9.6 mg/g. From this contaminated fly ash dumping site, 67 chromium ...

  9. Mechanical properties of composite coatings of chromium and nanodiamonds on aluminum

    Directory of Open Access Journals (Sweden)

    Gidikova Nelly

    2018-01-01

    Full Text Available Aluminum offers engineers weight saving advantages in their product design. However, aluminum has poor wear and friction properties. In addition, the surface oxide layer of this chemically active metal, which gives it the corrosion resistance, makes it a very difficult metal to plate [1]. Specific pre-treatment must be applied to remove the oxide layer from the aluminum surface. The nanodiamond particles additionally facilitates the process of chromium deposition. The object of this study is to evaluate the impact of nanodiamonds on the mechanical properties of the chromium coating plated on

  10. Partial priapism

    DEFF Research Database (Denmark)

    Hoyerup, Peter; Azawi, Nessn Htum

    2013-01-01

    With only 34 prior cases in world literature, partial priapism (PP), also called partial segmental thrombosis of the corpus cavernosum, is a rare urological condition. The aetiology and treatment of PP is still unclear, but bicycle riding, trauma, drug usage, sexual intercourse, haematological...

  11. Total control of chromium in tanneries - thermal decomposition of filtration cake from enzymatic hydrolysis of chrome shavings.

    Science.gov (United States)

    Kocurek, P; Kolomazník, K; Bařinová, M; Hendrych, J

    2017-04-01

    This paper deals with the problem of chromium recovery from chrome-tanned waste and thus with reducing the environmental impact of the leather industry. Chrome-tanned waste was transformed by alkaline enzymatic hydrolysis promoted by magnesium oxide into practically chromium-free, commercially applicable collagen hydrolysate and filtration cake containing a high portion of chromium. The crude and magnesium-deprived chromium cakes were subjected to a process of thermal decomposition at 650°C under oxygen-free conditions to reduce the amount of this waste and to study the effect of magnesium removal on the resulting products. Oxygen-free conditions were applied in order to prevent the oxidation of trivalent chromium into the hazardous hexavalent form. Thermal decomposition products from both crude and magnesium-deprived chrome cakes were characterized by high chromium content over 50%, which occurred as eskolaite (Cr 2 O 3 ) and magnesiochromite (MgCr 2 O 4 ) crystal phases, respectively. Thermal decomposition decreased the amount of chrome cake dry feed by 90%. Based on the performed experiments, a scheme for the total control of chromium in the leather industry was designed.

  12. Adsorption of Chromium Ion by Acid Activated Low Cost Carbon-Kinetic, Mechanistic, Thermodynamic and Equilibrium Studies

    Directory of Open Access Journals (Sweden)

    S. Arivoli

    2008-01-01

    Full Text Available A carbonaceous adsorbent prepared from an indigenous waste by acid treatment was tested for its efficiency in removing chromium ion. The parameters studied include agitation time, initial chromium ion concentration, carbon dose, pH and temperature. The adsorption followed first order reaction equation and the rate is mainly controlled by intra-particle diffusion. Freundlich and Langmuir isotherm models were applied to the equilibrium data. The adsorption capacity (Qm obtained from the Langmuir isotherm plots were 27.40, 26.06, 26.06 and 26.17 mg/g respectively at an initial pH of 7.0 at 30, 40, 50 and 60°C. The temperature variation study showed that the chromium ion adsorption is endothermic and spontaneous with increased randomness at the solid solution interface. Significant effect on adsorption was observed on varying the pH of the chromium ion solutions. Almost 70% removal of chromium ion was observed at 60°C. The Langmuir and Freundlich isotherms obtained, positive ∆H0 value, pH dependent results and desorption of dye in mineral acid suggest that the adsorption of chromium ion on PDC involves physisorption mechanism.

  13. Evaluation of dum palm kernel activated carbon in chromium and lead adsorption from synthetic waste water

    Directory of Open Access Journals (Sweden)

    HI Mohammed

    2016-09-01

    Full Text Available This study aimed at the co-current removal of chromium and lead ions from synthetic waste water using dum palm kernel activated carbon. The adsorption experiment was conducted by varying time, pH and concentrations of the simulated solution. The data obtained were analyzed, and the best conditions for the uptake were at pH of 6, equilibrium time of 40 minutes. The two best isotherms models for the adsorption system were Sip, and Dubinin–Radushkevich, models respectively. Based on the Temkin adsorption energy calculated as 9.5793 and 0.4997 J/mol, the uptake of lead and chromium were chemisorption and physico-sorption, respectively. The maximum uptake calculated from Dubinin–Radushkevich plots were 14.1696 and 7.7191 mg/g, for lead and chromium, respectively.International Journal of Environment Vol.5(3 2016, pp.104-118

  14. Reduction of Health Risks Due to Chromium(VI)Using Mesquite: A Potential Cr Phytoremediator

    Energy Technology Data Exchange (ETDEWEB)

    Gardea-Torresdey, Jorge L.; Aldrich, Mary V.; Peralta-Videa, Jose R.; Parsons, Jason G.

    2004-03-29

    Chromium is a transition metal extensively used in industry. Cr mining and industrial operations account for chromium wastes at Superfund sites in the United States. A study was performed to investigate the possibility of using mesquite (Prosopis spp.), which is an indigenous desert plant species, to remove Cr from contaminated sites. In this study, mesquite plants were grown in an agar-based medium containing 75 mg L-1 and 125 mg L-1 of Cr(VI). The Cr content of leaf tissue (992 mg kg-1 of dry weight, from 125 mg L-1 of Cr(VI)) indicated that mesquite could be classified as a chromium hyperaccumulator. X-ray absorption spectroscopy (XAS) studies performed to experimental samples showed that mesquite roots absorbed some of the supplied Cr(VI). However, the data analyses of plant tissues demonstrated that the absorbed Cr(VI) was fully reduced to Cr(III) in the leaf tissue.

  15. Disturbance response indicators of Impatiens walleriana exposed to benzene and chromium.

    Science.gov (United States)

    Campos, V; Lessa, S S; Ramos, R L; Shinzato, M C; Medeiros, T A M

    2017-08-03

    The purpose of this study was to evaluate the remediation potential and disturbance response indicators of Impatiens walleriana exposed to benzene and chromium. Numerous studies over the years have found abundant evidence of the carcinogenicity of benzene and chromium (VI) in humans. Benzene and chromium are two toxic industrial chemicals commonly found together at contaminated sites, and one of the most common management strategies employed in the recovery of sites contaminated by petroleum products and trace metals is in situ remediation. Given that increasing interest has focused on the use of plants as depollution agents, direct injection tests and benzene misting were performed on I. walleriana to evaluate the remediation potential of this species. I. walleriana accumulated hexavalent chromium, mainly in the root system (164.23 mg kg -1 ), to the detriment of the aerial part (39.72 mg kg -1 ), and presented visible damage only at the highest concentration (30 mg L -1 ). Unlike chromium (VI), chromium (III) was retained almost entirely by the soil, leaving it available for removal by phytotechnology. However, after the contamination stopped, I. walleriana responded positively to the detoxification process, recovering its stem stiffness and leaf color. I. walleriana showed visible changes such as leaf chlorosis during the ten days of benzene contamination. When benzene is absorbed by the roots, it is translocated to and accumulated in the plant's aerial part. This mechanism the plant uses ensures its tolerance to the organic compound, enabling the species to survive and reproduce after treatment with benzene. Although I. walleriana accumulates minor amounts of hexavalent chromium in the aerial part, this amount suffices to induce greater oxidative stress and to increase the amount of hydrogen peroxide when compared to that of benzene. It was therefore concluded that I. walleriana is a species that possesses desirable characteristics for phytotechnology.

  16. Low-chromium reduced-activation chromium-tungsten steels

    Energy Technology Data Exchange (ETDEWEB)

    Klueh, R.L.; Alexander, D.J.; Maziasz, P.J. [Oak Ridge National Lab., TN (United States)

    1996-10-01

    Bainitic microstructures formed during continuous cooling can differ from classical upper and lower bainite formed during isothermal transformation. Two types of non-classical bainite were observed depending on the cooling rate: carbide-free acicular bainite at rapid cooling rates and granular bainite at slower cooling rates. The Charpy impact toughness of the acicular ferrite was found to be considerably better than for the granular bainite. It was postulated that alloying to improve the hardenability of the steel would promote the formation of acicular bainite, just as increasing the cooling rate does. To test this, chromium and tungsten were added to the 2 1/4Cr-2W and 2 1/4Cr-2WV steel compositions to increase their hardenability, and the microstructures and mechanical properties were examined.

  17. Experimental patch testing with chromium-coated materials

    DEFF Research Database (Denmark)

    Bregnbak, David; Thyssen, Jacob P; Jellesen, Morten Stendahl

    2017-01-01

    Chromium coatings on metal alloys can be decorative, and prevent corrosion and metal ion release. We recently showed that handling of a chromium-containing disc resulted in chromium deposition on the skin. To examine patch test reactivity to chromium-coated discs. We included 15 patients: 10...

  18. Sorption of Chromium (VI Using Excess Municipal Sludge

    Directory of Open Access Journals (Sweden)

    Farzaneh Mohammadi

    2014-04-01

    Full Text Available Removing or decreasing hexavalent Chromium from wastewater to the permitted levels is important due to its non-biodegradation, bioaccumulation, cancer-causing and toxic effects. In this study, biosorption of Cr(VI from aqueous solutions by Excess Active Municipal Sludge was investigated as a function of initial Chromium (VI concentration (in the range of 5-90 mg/l, initial pH (in the range of 2-8, agitation speed (in the range of 50-200 rpm, adsorbent dosage (in the range of 2-10 g/l and agitation time (in the range of 5-480 min in a batch system. The optimum conditions were found by full factorial design approach. The results showed that the equilibrium time for adsorbent is 120 minutes. Also, sorption data have a good fitness by Freundlich isotherm model and adsorption kinetic is adopted with pseudo-second order model. In batch studies, at optimum condition (90 mg/l initial concentration, pH 2, agitation speed 200 rpm and adsorbent dosage 4 g/l, the adsorption performance was about 96%; the maximum adsorption capacity was calculated about 41.69 mg of Cr/g of adsorbent. Overall, it can be concluded that Excess Active Municipal Sludge, has a good performance as a biological, biodegradable, abundant and low-cost adsorbent for the removal of Cr (VI from aqueous solutions.

  19. Reproductive toxicological aspects of chromium in males

    International Nuclear Information System (INIS)

    Ernst, E.

    1994-01-01

    To expand our present understanding of the effects of chromium on male fertility a number of studies were designed to achieve this through the use of chromium intoxicated experimental animals and through investigation of sexual hormones and sperm quality in welders. Also in view of the lack of an experimental model for effects of noxious substance on the epididymal spermatozoa the main objectives of the series of studies reviewed here were: A. To establish a model for evaluation of epididymal sperm count and motility in the rat. B. To investigate and compare the effects of tri- and hexavalent chromium on epididymal spermatozoa. Further to describe the effects of low-dose long-time exposure of rats to the most toxicological interesting chromium oxidative state - hexavalent chromium. C. By the use of autoradiography and γ-countinuing to expand the present knowledge on the distribution of chromium in the body with special reference to the male reproductive organs. D. To describe the effects of exposure to hexavalent chromium in welding fume on levels of sexual hormones and semen parameters in welders. (EG)

  20. Reproductive toxicological aspects of chromium in males

    Energy Technology Data Exchange (ETDEWEB)

    Ernst, E.

    1994-12-31

    To expand our present understanding of the effects of chromium on male fertility a number of studies were designed to achieve this through the use of chromium intoxicated experimental animals and through investigation of sexual hormones and sperm quality in welders. Also in view of the lack of an experimental model for effects of noxious substance on the epididymal spermatozoa the main objectives of the series of studies reviewed here were: A. To establish a model for evaluation of epididymal sperm count and motility in the rat. B. To investigate and compare the effects of tri- and hexavalent chromium on epididymal spermatozoa. Further to describe the effects of low-dose long-time exposure of rats to the most toxicological interesting chromium oxidative state - hexavalent chromium. C. By the use of autoradiography and {gamma}-countinuing to expand the present knowledge on the distribution of chromium in the body with special reference to the male reproductive organs. D. To describe the effects of exposure to hexavalent chromium in welding fume on levels of sexual hormones and semen parameters in welders. (EG).