Does cement mantle thickness really matter?

OpenAIRE

Caruana, J.

2008-01-01

The thickness of the cement mantle around the femoral component of total hip replacements is a contributing factor to aseptic loosening and revision. Nevertheless, various designs of stems and surgical tooling lead to cement mantles of differing thicknesses. This thesis is concerned with variability in cement thickness around the Stanmore Hip, due to surgical approach, broach size and stem orientation, and its effects on stress and cracking in the cement. The extent to which cement mantle thi...

Contact damage failure analyses of fretting wear behavior of the metal stem titanium alloy-bone cement interface.

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Zhang, Lanfeng; Ge, Shirong; Liu, Hongtao; Wang, Qingliang; Wang, Liping; Xian, Cory J

2015-11-01

Although cemented titanium alloy is not favored currently in the Western world for its poor clinical and radiography outcomes, its lower modulus of elasticity and good biocompatibility are instrumental for its ability supporting and transforming physical load, and it is more suitable for usage in Chinese and Japanese populations due to their lower body weights and unique femoral characteristics. Through various friction tests of different cycles, loads and conditions and by examining fretting hysteresis loops, fatigue process curves and wear surfaces, the current study investigated fretting wear characteristics and wear mechanism of titanium alloy stem-bone cement interface. It was found that the combination of loads and displacement affected the wear quantity. Friction coefficient, which was in an inverse relationship to load under the same amplitude, was proportional to amplitudes under the same load. Additionally, calf serum was found to both lubricate and erode the wear interface. Moreover, cement fatigue contact areas appeared black/oxidative in dry and gruel in 25% calf serum. Fatigue scratches were detected within contact areas, and wear scars were found on cement and titanium surfaces, which were concave-shaped and ring concave/ convex-shaped, respectively. The coupling of thermoplastic effect and minimal torque damage has been proposed to be the major reason of contact damage. These data will be important for further studies analyzing metal-cement interface failure performance and solving interface friction and wear debris production issues. Copyright © 2015 Elsevier Ltd. All rights reserved.

The mechanical effect of the existing cement mantle on the in-cement femoral revision.

LENUS (Irish Health Repository)

Keeling, Parnell

2012-08-01

Cement-in-cement revision hip arthroplasty is an increasingly popular technique to replace a loose femoral stem which retains much of the original cement mantle. However, some concern exists regarding the retention of the existing fatigued and aged cement in such cement-in-cement revisions. This study investigates whether leaving an existing fatigued and aged cement mantle degrades the mechanical performance of a cement-in-cement revision construct.

Cement augmentation in the proximal femur to prevent stem subsidence in revision hip arthroplasty with Paprosky type II/IIIa defects

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Shang-Wen Tsai

2018-06-01

Full Text Available Background: Subsidence remains a common complication after revision hip arthroplasty which may lead to prolonged weight-bearing restrictions, leg-length discrepancies or considerable loss of function. We evaluated the effectiveness of cement augmentation in the proximal femoral metaphysis during a revision of femoral components to prevent post-operative stem subsidence. Methods: Forty patients were enrolled. Follow-up averaged 67.7 months (range: 24–149. Twenty-seven patients had a Paprosky type II defect and 13 had a type IIIa defect. All revision hip arthroplasty used a cementless, cylindrical, non-modular cobalt–chromium stem. The defect in the metaphysis was filled with antibiotic-loaded bone cement. Thirteen patients who had undergone stem revision only was allowed to walk immediately without weight-bearing restrictions. Twenty-seven patients who had undergone revision total hip arthroplasty was allowed partial weight-bearing within 6 weeks after surgery in the consideration of acetabular reconstruction. Results: Three patients (7.5% had post-surgery stem subsidences of three mm, five mm, and 10 mm, respectively, at three, one, and 14 months. There were no acute surgical site infections. There were three femoral stem failures: two delayed infections and one periprosthetic Vancouver B2 fracture. Both five- and 10-year survivorships of the femoral implant were 90.1%. Conclusion: An adequate length of the scratch-fit segment and diaphyseal ingrowth remain of paramount importance when revising femoral components. To fill metaphyseal bone defects with antibiotic-loaded bone cement may be an alternative method in dealing with proximal femoral bone loss during a femoral revision. Keywords: Bone defect, Cement augmentation, Femur, Revision hip arthroplasty, Subsidence

The mechanical effect of the existing cement mantle on the in-cement femoral revision.

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Keeling, Parnell; Lennon, Alexander B; Kenny, Patrick J; O'Reilly, Peter; Prendergast, Patrick J

2012-08-01

Cement-in-cement revision hip arthroplasty is an increasingly popular technique to replace a loose femoral stem which retains much of the original cement mantle. However, some concern exists regarding the retention of the existing fatigued and aged cement in such cement-in-cement revisions. This study investigates whether leaving an existing fatigued and aged cement mantle degrades the mechanical performance of a cement-in-cement revision construct. Primary cement mantles were formed by cementing a polished stem into sections of tubular steel. If in the test group, the mantle underwent conditioning in saline to simulate ageing and was subject to a fatigue of 1 million cycles. If in the control group no such conditioning or fatigue was carried out. The cement-in-cement procedure was then undertaken. Both groups underwent a fatigue of 1 million cycles subsequent to the revision procedure. Application of a Mann-Whitney test on the recorded subsidence (means: 0.51, 0.46, n=10+10, P=0.496) and inducible displacement (means: 0.38, 0.36, P=0.96) revealed that there was no statistical difference between the groups. This study represents further biomechanical investigation of the mechanical behaviour of cement-in-cement revision constructs. Results suggest that pre-revision fatigue and ageing of the cement may not be deleterious to the mechanical performance of the revision construct. Thus, this study provides biomechanical evidence to back-up recent successes with this useful revision technique. Copyright © 2012 Elsevier Ltd. All rights reserved.

10-year results of a new low-monomer cement: follow-up of a randomized RSA study.

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Söderlund, Per; Dahl, Jon; Röhrl, Stephan; Nivbrant, Bo; Nilsson, Kjell G

2012-12-01

The properties and performance of a new low-monomer cement were examined in this prospective randomized, controlled RSA study. 5-year data have already been published, showing no statistically significant differences compared to controls. In the present paper we present the 10-year results. 44 patients were originally randomized to receive total hip replacement with a Lubinus SPII titanium-aluminum-vanadium stem cemented either with the new Cemex Rx bone cement or with control bone cement, Palacos R. Patients were examined using RSA, Harris hip score, and conventional radiographs. At 10 years, 33 hips could be evaluated clinically and 30 hips could be evaluated with RSA (16 Cemex and 14 Palacos). 9 patients had died and 4 patients were too old or infirm to be investigated. Except for 1 hip that was revised for infection after less than 5 years, no further hips were revised before the 10-year follow-up. There were no statistically significant clinical differences between the groups. The Cemex cement had magnitudes of migration similar to or sometimes lower than those of Palacos cement. In both groups, most hips showed extensive radiolucent lines, probably due to the use of titanium alloy stems. At 10 years, the Cemex bone cement tested performed just as well as the control (Palacos bone cement).

[Early aseptic loosening of the CF 30 femoral stem].

Science.gov (United States)

Kovanda, M; Havlícek, V; Hudec, J

2007-02-01

The CF 30 stem in combination with a cementless acetabulum was used at the First Department of Orthopedic Surgery in Brno in the years 1994 to 1995. From the second year following implantation, aseptic stem loosening was recorded. In order to find explanation of this early loosening, the authors, in cooperation with the Institute of Solid Mechanics, Mechatronics and Biomechanics, carried out the stress-strain analysis in a model system. Eighty patients (31 men and 49 women) received a cemented CF30 femoral component in 1994. Of them, 16 patients underwent revision arthroplasty, three died of causes unrelated to the surgery, and four were lost to follow-up. The final clinical and radiographic check-up was carried out in 2001. The results of a comprehensive examination were available in 57 patients with a CF30 stem. The patients were evaluated on the basis of the Harris hip score and anteroposterior radiographs of the hip. X-ray films obtained immediately after surgery and those taken at regular intervals during follow-up were compared. The following characteristics were noted: translucent lines in individual zones along the stem at the cement-bone interface; osteolysis, i. e., non-linear translucent areas, at least 5 mm long, at the cement-bone interface; and subsidence of the femoral component, i. e., migration of the stem distal to the tip of the greater trochanter. The CF 30 stem survival curve showed that aseptic stem loosening occurred from post-implantation year 2, and increased during the following years. At 6 years and 6 months, a total of 16 patients underwent revision surgery, involving reimplantation in 14 and implant removal in 2 patients. Potential causes of aseptic loosening: Polyethylene wear.However, no acetabular loosening was found in this group, although acetabular components are reported to become loose more often than femoral components. By comparison of the stem survival curves for Poldi and CF 30 stems it appeared that, at 6 years and 6 months

Mechanical aspects of degree of cement bonding and implant wedge effect.

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Yoon, Yong-San; Oxland, Thomas R; Hodgson, Antony J; Duncan, Clive P; Masri, Bassam A; Choi, Donok

2008-11-01

The degree of bonding between the femoral stem and cement in total hip replacement remains controversial. Our objective was to determine the wedge effect by debonding and stem taper angle on the structural behavior of axisymmetric stem-cement-bone cylinder models. Stainless steel tapered plugs with a rough (i.e. bonded) or smooth (i.e. debonded) surface finish were used to emulate the femoral stem. Three different stem taper angles (5 degrees , 7.5 degrees , 10 degrees ) were used for the debonded constructs. Non-tapered and tapered (7.5 degrees ) aluminum cylindrical shells were used to emulate the diaphyseal and metaphyseal segments of the femur. The cement-aluminum cylinder interface was designed to have a shear strength that simulated bone-cement interfaces ( approximately 8MPa). The test involved applying axial compression at a rate of 0.02mm/s until failure. Six specimens were tested for each combination of the variables. Finite element analysis was used to enhance the understanding of the wedge effect. The debonded stems sustained about twice as much load as the bonded stem, regardless of taper angle. The metaphyseal model carried 35-50% greater loads than the diaphyseal models and the stem taper produced significant differences. Based on the finite element analysis, failure was most probably by shear at the cement-bone interface. Our results in this simplified model suggest that smooth (i.e. debonded) stems have greater failure loads and will incur less slippage or shear failure at the cement-bone interface than rough (i.e. bonded) stems.

Crown and bridge cements: clinical applications.

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Bunek, Sabiha S; Powers, John M

2012-12-01

Cement selection can be confusing because factors such as substrate, the type of restoration, and patient needs must be considered. Some substrates require additional treatment before cementation. This article describes the most commonly used traditional crown and bridge cements (GI and RMGI) used for metal and metal-ceramic restorations, and resin cements used for all-ceramic restorations. Advantages, disadvantages, indications, and contraindications of cements have been reviewed. Recommended uses of cements for metal, ceramic, and laboratory composite restorations have been presented. General guidelines for surface treatment ot silica- and zirconia-based restorations when using resin cements have been discussed.

Correlation between clinical performance and degree of conversion of resin cements: a literature review

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Grace DE SOUZA

2015-08-01

Full Text Available AbstractResin-based cements have been frequently employed in clinical practice to lute indirect restorations. However, there are numerous factors that may compromise the clinical performance of those cements. The aim of this literature review is to present and discuss some of the clinical factors that may affect the performance of current resin-based luting systems. Resin cements may have three different curing mechanisms: chemical curing, photo curing or a combination of both. Chemically cured systems are recommended to be used under opaque or thick restorations, due to the reduced access of the light. Photo-cured cements are mainly indicated for translucent veneers, due to the possibility of light transmission through the restoration. Dual-cured are more versatile systems and, theoretically, can be used in either situation, since the presence of both curing mechanisms might guarantee a high degree of conversion (DC under every condition. However, it has been demonstrated that clinical procedures and characteristics of the materials may have many different implications in the DC of currently available resin cements, affecting their mechanical properties, bond strength to the substrate and the esthetic results of the restoration. Factors such as curing mechanism, choice of adhesive system, indirect restorative material and light-curing device may affect the degree of conversion of the cement and, therefore, have an effect on the clinical performance of resin-based cements. Specific measures are to be taken to ensure a higher DC of the luting system to be used.

Peri-Implantitis Associated with Type of Cement: A Retrospective Analysis of Different Types of Cement and Their Clinical Correlation to the Peri-Implant Tissue.

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Korsch, Michael; Walther, Winfried

2015-10-01

The cementation of fixed implant-supported dental restorations involves the risk of leaving excess cement in the mouth which can promote biofilm formation in the peri-implant sulcus. As a result, an inflammation may develop. The aim of the present study was to investigate the clinical effect of two different luting cements on the peri-implant tissue. Within the scope of a retrospective clinical follow-up study, the prosthetic structures of 22 patients with 45 implants were revised. In all cases, a methacrylate cement (Premier Implant Cement [PIC], Premier® Dental Products Company, Plymouth Meeting, PA, USA) had been used for cementation. In 16 additional patients with 28 implants, the suprastructures were retained with a zinc oxide-eugenol cement (Temp Bond [TB], Kerr Sybron Dental Specialities, Glendora, CA, USA). These patients were evaluated in the course of routine treatment. In both populations, the retention time of the suprastructures was similar (TB 3.77 years, PIC 4.07 years). In the PIC cases, 62% of all implants had excess cement. In the TB cases, excess cement was not detectable on any of the implants. Bleeding on probing was significantly more frequent on implants cemented with PIC (100% with and 94% without excess cement) than on implants cemented with TB (46%). Pocket suppuration was observed on 89% of the PIC-cemented implants with excess cement (PIC without excess cement 24%), whereas implants with TB were not affected by it at all. The peri-implant bone loss was significantly greater in the PIC patients (with excess cement 1.37 mm, without excess cement 0.41 mm) than it was in the TB patients (0.07 mm). The frequency of undetected excess cement depends essentially on the type of cement used. Cements that tend to leave more undetected excess have a higher prevalence for peri-implant inflammation and cause a more severe peri-implant bone loss. © 2014 Wiley Periodicals, Inc.

[Poldi-Čech cemented femoral stem in total hip arthroplasty after 25 years].

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Rozkydal, Z; Janíček, P

2010-08-01

The aim of the study was to evaluate the results of Poldi-Čech femoral stem implantation in primary total hip arthroplasty after 25 years. A group of 65 patients (90 hips) with Poldi-Čech total hip arthroplasty carried out between 1974 and 1984 was evaluated at the end of 2009. The mean follow-up of all patients was 28 years (25 to 35). There were seven men and 58 women. The mean age at the time of implantation was 43 years (26 to 60) and at the latest follow-up it was 72 years. In all patients the cemented UHMW PE acetabular component (RCH 1000) was used together with AKV Ultra 2 Poldi steel femoral stems (1st, 2nd and 3rd generations). The stem was a monoblock with a 32-mm head. The evaluation of the results was based on the Harris hip score and X ray with an A-P view of the pelvis and the affected hip. Statistical analysis was made using the life-table method. At the latest follow up the mean Harris score was 69.7 points (40 to 88). There were 69 hips with an original Poldi-Čech femoral component still in situ, 64 of them were stable and five with radiological evidence of aseptic loosening. Five patients had undergone Girdlestone resection arthroplasty for septic loosening. Thirteen patients (16 hips) had femoral stem revision. The cumulative proportion of clinical survivorship of the Poldi-Čech femoral stem, with revision for any reason as the endpoint, .was 0.93 at 6 years, 0.84 at 12 years, and 0.77 at 18, 24 and 30 years after the index surgery. Radiographic findings revealed 64 hips with stable stems, five hips with ;aseptic loosening (probable, 0 possible, 2, definite, 3). Six- teen hips were after revision surgery for aseptic loosening of the stem and five hips were after Girdlestone resection arthroplasty for septic failure. The cumulative proportion of radiological survivorship of the Poldi-Čech femoral stem with any reason as the endpoint was 0.92 at 6 years, 0.78 at 12 years, 0.72 at 18 years, 0.69 at 24 years and 0.69 at 30 years. The Poldi

Continuous distal migration and internal rotation of the C-stem prosthesis without any adverse clinical effects: an RSA study of 33 primary total hip arthroplasties followed for up to ten years.

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von Schewelov, T; Carlsson, A; Sanzén, L; Besjakov, J

2014-05-01

In 2005, we demonstrated that the polished triple-tapered C-stem at two years had migrated distally and rotated internally. From that series, 33 patients have now been followed radiologically, clinically and by radiostereometric analysis (RSA) for up to ten years. The distal migration within the cement mantle had continued and reached a mean of 2 mm (0.5 to 4.0) at ten years. Internal rotation, also within the cement mantle, was a mean 3.8° (external 1.6° to internal 6.6°) The cement mantle did not show any sign of migration or loosening in relation to the femoral bone. There were no clinical or radiological signs indicating that the migration or rotation within the cement mantle had had any adverse effects for the patients.

Cemented total knee replacement in 24 dogs: surgical technique, clinical results, and complications.

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Allen, Matthew J; Leone, Kendall A; Lamonte, Kimberly; Townsend, Katy L; Mann, Kenneth A

2009-07-01

To characterize the performance of cemented total knee replacement (TKR) in dogs. Preclinical research study. Skeletally mature, male Hounds (25-30 kg; n=24) with no preexisting joint pathology. Dogs had unilateral cemented TKR and were evaluated at 6, 12, 26, or 52 weeks (6 dogs/time point) by radiography, bone density analysis, visual gait assessment, and direct measurement of thigh circumference and stifle joint range of motion as indicators of functional recovery. At study end, the stability of the cemented tibial component was determined by destructive mechanical testing. Joint stability was excellent in 16 dogs (67%) and good in 8 dogs. None of the tibial components had evidence of migration or periprosthetic osteolysis whereas 1 femoral component was loose at 52 weeks. There was an early and significant decrease in tibial bone density, likely because of disuse of the operated limb. Dogs returned to full activity by 12 weeks. The tibial cement-bone interface maintained its strength over 52 weeks. Cement provides stable fixation of the tibial component in canine TKR. Cemented TKR yields adequate clinical function and stifle joint excursion in the dog. Clinical studies are needed to determine the long-term fate of cemented TKR implants, to assess the influence of implant design on implant fixation and wear, and to obtain objective functional data.

Dental Cements for Luting and Bonding Restorations: Self-Adhesive Resin Cements.

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Manso, Adriana P; Carvalho, Ricardo M

2017-10-01

Self-adhesive resin cements combine easy application of conventional luting materials with improved mechanical properties and bonding capability of resin cements. The presence of functional acidic monomers, dual cure setting mechanism, and fillers capable of neutralizing the initial low pH of the cement are essential elements of the material and should be understood when selecting the ideal luting material for each clinical situation. This article addresses the most relevant aspects of self-adhesive resin cements and their potential impact on clinical performance. Although few clinical studies are available to establish solid clinical evidence, the information presented provides clinical guidance in the dynamic environment of material development. Copyright © 2017 Elsevier Inc. All rights reserved.

Clinical grade adult stem cell banking.

Science.gov (United States)

Thirumala, Sreedhar; Goebel, W Scott; Woods, Erik J

2009-07-01

There has been a great deal of scientific interest recently generated by the potential therapeutic applications of adult stem cells in human care but there are several challenges regarding quality and safety in clinical applications and a number of these challenges relate to the processing and banking of these cells ex-vivo. As the number of clinical trials and the variety of adult cells used in regenerative therapy increases, safety remains a primary concern. This has inspired many nations to formulate guidelines and standards for the quality of stem cell collection, processing, testing, banking, packaging and distribution. Clinically applicable cryopreservation and banking of adult stem cells offers unique opportunities to advance the potential uses and widespread implementation of these cells in clinical applications. Most current cryopreservation protocols include animal serum proteins and potentially toxic cryoprotectant additives (CPAs) that prevent direct use of these cells in human therapeutic applications. Long term cryopreservation of adult stem cells under good manufacturing conditions using animal product free solutions is critical to the widespread clinical implementation of ex-vivo adult stem cell therapies. Furthermore, to avoid any potential cryoprotectant related complications, reduced CPA concentrations and efficient post-thaw washing to remove CPA are also desirable. The present review focuses on the current strategies and important aspects of adult stem cell banking for clinical applications. These include current good manufacturing practices (cGMPs), animal protein free freezing solutions, cryoprotectants, freezing & thawing protocols, viability assays, packaging and distribution. The importance and benefits of banking clinical grade adult stem cells are also discussed.

Calcium silicate-based cements: composition, properties, and clinical applications.

Science.gov (United States)

Dawood, Alaa E; Parashos, Peter; Wong, Rebecca H K; Reynolds, Eric C; Manton, David J

2017-05-01

Mineral trioxide aggregate (MTA) is a calcium silicate-based cement (CSC) commonly used in endodontic procedures involving pulpal regeneration and hard tissue repair, such as pulp capping, pulpotomy, apexogenesis, apexification, perforation repair, and root-end filling. Despite the superior laboratory and clinical performance of MTA in comparison with previous endodontic repair cements, such as Ca(OH) 2 , MTA has poor handling properties and a long setting time. New CSC have been commercially launched and marketed to overcome the limitations of MTA. The aim of the present review was to explore the available literature on new CSC products, and to give evidence-based recommendations for the clinical use of these materials. Within the limitations of the available data in the literature regarding the properties and performance of the new CSC, the newer products could be promising alternatives to MTA; however, further research is required to support this assumption. © 2015 Wiley Publishing Asia Pty Ltd.

Aseptic loosening of the femoral implant after cemented total hip arthroplasty in dogs: 11 cases in 10 dogs (1991-1995)

International Nuclear Information System (INIS)

Edwards, M.R.; Egger, E.L.; Schwarz, P.D.

1997-01-01

Objective-To determine clinical signs, radiographic findings, results of surgical management, and potential causes of aseptic loosening of the femoral implant (ALFI) in dogs that have undergone cemented total hip arthroplasty (THA). Design-Retrospective study. Animals-11 cases of ALFI in 10 dogs. Procedure-Medical records of all dogs undergoing THA revision surgery were reviewed. Only dogs with ALFI were included. The prosthesis and cement were removed by creating a longitudinal osteotomy of the cranial femoral cortex. Postoperative radiographs of all dogs that underwent THA during the study period were reviewed. Results-The most common clinical sign was intermittent, subtle. or non-weight-bearing lameness. On radiographs obtained after THA, contact of the distal stem tip with cortical endosteum was evident in all dogs. Radiographic changes at the time of diagnosis of ALFI included asymmetric periosteal reaction along the femoral diaphysis, radiolucent lines between the prosthesis and cement, altered implant position, and femoral fracture. Surgical revision yielded good or excellent results in 9 cases. In 1 dog. the implant became infected; in another, aseptic loosening recurred. Aseptic loosening was significantly more common in dogs in which there was contact between the distal stem tip and cortical endosteum than in dogs in which there was no contact. Clinical Implications-ALFI is an uncommon, but important, complication of THA, and radiography is warranted in dogs with clinical signs of ALFI. Initial centering of the prosthetic stem within the femoral shaft may reduce the incidence of ALFI

A computerized pre-clinical test for cemented hip prostheses based on finite element techniques

NARCIS (Netherlands)

Stolk, Jan

2003-01-01

Despite the success of cemented total hip replacement (THR), high failure rates are occasionally reported for cemented hip implants that are introduced on the orthopaedic market. Rigorous pre-clinical testing of hip implants could prevent these disasters, by detecting unsafe implant designs at a

Stem cell clinics online: the direct-to-consumer portrayal of stem cell medicine.

Science.gov (United States)

Lau, Darren; Ogbogu, Ubaka; Taylor, Benjamin; Stafinski, Tania; Menon, Devidas; Caulfield, Timothy

2008-12-04

Despite the immature state of stem cell medicine, patients are seeking and accessing putative stem cell therapies in an "early market" in which direct-to-consumer advertising via the internet likely plays an important role. We analyzed stem cell clinic websites and appraised the relevant published clinical evidence of stem cell therapies to address three questions about the direct-to-consumer portrayal of stem cell medicine in this early market: What sorts of therapies are being offered? How are they portrayed? Is there clinical evidence to support the use of these therapies? We found that the portrayal of stem cell medicine on provider websites is optimistic and unsubstantiated by peer-reviewed literature.

Clinical trials for stem cell transplantation: when are they needed?

Science.gov (United States)

Van Pham, Phuc

2016-04-27

In recent years, both stem cell research and the clinical application of these promising cells have increased rapidly. About 1000 clinical trials using stem cells have to date been performed globally. More importantly, more than 10 stem cell-based products have been approved in some countries. With the rapid growth of stem cell applications, some countries have used clinical trials as a tool to diminish the rate of clinical stem cell applications. However, the point at which stem cell clinical trials are essential remains unclear. This commentary discusses when stem cell clinical trials are essential for stem cell transplantation therapies.

Factors influencing success of cement versus screw-retained implant restorations: a clinical review

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Ahmad Manawar

2012-10-01

Full Text Available Aim: As more and more dental practitioners are focusing on implant-supported fixed restorations, some clinicians favor the use of cement retained restorations while others consider screw retained prosthesis to be the best choice. Discussion: In screw-retained restorations, the fastening screw provides a solid joint between the restoration and the implant abutment, while in cement-retained prostheses the restorative screw is eliminated to enhance esthetics, occlusal stability, and passive fit of the restorations. The factors that influence the type of fixation of the prostheses to the implants like passivity of the framework, ease of fabrication, occlusion, esthetics, accessibility, retention and retrievability are discussed in this article with scientific studies demonstrating superior outcomes of one technique over another. Screwretained implant restorations have an advantage of predictable retention, retrievability and lack of potentially retained subgingival cement. However, a few disadvantages exist such as precise placement of the implant for optimal and esthetic location of the screw access hole and obtaining passive fit. On the other hand, cement retained restorations eliminate unesthetic screw access holes, have passive fit of castings, reduced complexity of clinical and lab procedures, enhanced esthetics, reduced cost factors and non disrupted morphology of the occlusal table. Conclusion: This article compares the advantages, potential disadvantages and limitations of screw and cement retained restorations and their specific implications in the most common clinical situation.

Characterisation of the surface topography, tomography and chemistry of fretting corrosion product found on retrieved polished femoral stems.

Science.gov (United States)

Bryant, M; Ward, M; Farrar, R; Freeman, R; Brummitt, K; Nolan, J; Neville, A

2014-04-01

This study presents the characterisation of the surface topography, tomography and chemistry of fretting corrosion product found on retrieved polished femoral stems. Scanning Electron Microscopy (SEM), X-ray Photoelectron Spectroscopy (XPS), Transmission Electron Microscopy (TEM) and Fourier Transform Infrared Spectroscopy (FI-IR) were utilised in order to assess the surface morphology of retrieved Metal-on-Metal Total Hip Replacements and surface chemistry of the films found on the surface. Gross slip, plastic deformation and directionality of the surface were extensively seen on the proximal surfaces of the retrievals. A more corrosive phenomenon was observed in the distal regions of the stem, demonstrating a seemingly intergranular attack. Tribochemical reactions were seen to occur within the stem-cement interfaces with tribofilms being observed on the femoral stem and counterpart PMMA bone cement. XPS, TEM-EDX and FT-IR analyses demonstrated that the films present in the stem surfaces were a complex mixture of chromium oxide and amorphous organic material. A comparison between current experimental and clinical literature has been conducted and findings from this study demonstrate that the formation and chemistry of films are drastically influenced by the type of wear or degradation mechanism. Films formed in the stem-cement interface are thought to further influence the biological environment outside the stem-cement interface due to the formation of Cr and O rich films within the interface whilst Co is free to migrate away. © 2013 Elsevier Ltd. All rights reserved.

The long-term in vivo behavior of polymethyl methacrylate bone cement in total hip arthroplasty.

Science.gov (United States)

Oonishi, Hiroyuki; Akiyama, Haruhiko; Takemoto, Mitsuru; Kawai, Toshiyuki; Yamamoto, Koji; Yamamuro, Takao; Oonishi, Hironobu; Nakamura, Takashi

2011-10-01

The long-term success of cemented total hip arthroplasty (THA) has been well established. Improved outcomes, both radiographically and clinically, have resulted mainly from advances in stem design and improvements in operating techniques. However, there is concern about the durability of bone cement in vivo. We evaluated the physical and chemical properties of CMW1 bone cements retrieved from patients undergoing revision THA. CMW1 cements were retrieved from 14 patients who underwent acetabular revision because of aseptic loosening. The time in vivo before revision was 7-30 years. The bending properties of the retrieved bone cement were assessed using the three-point bending method. The molecular weight and chemical structure were analyzed by gel permeation chromatography and Fourier-transform infrared spectroscopy. The porosity of the bone cements was evaluated by 3-D microcomputer tomography. The bending strength decreased with increasing time in vivo and depended on the density of the bone cement, which we assume to be determined by the porosity. There was no correlation between molecular weight and time in vivo. The infrared spectra were similar in the retrieved cements and in the control CMW1 cements. Our results indicate that polymer chain scission and significant hydrolysis do not occur in CMW1 cement after implantation in vivo, even in the long term. CMW1 cement was stable through long-term implantation and functional loading.

2-year follow-up report on micromotion of a short tibia stem. A prospective, randomized RSA study of 59 patients.

Science.gov (United States)

Molt, Mats; Toksvig-Larsen, Sören

2015-01-01

A shortened tibial stem could influence the early prosthetic fixation. We therefore compared the short stem to the standard-length stem using radiostereometric analysis (RSA) as primary outcome measure. 60 patients were randomized to receive a cemented Triathlon total knee arthroplasty (TKA) with a tibial tray of either standard or short stem length. The patients were blinded regarding treatment allocation. The micromotion of the tibial component was measured by RSA postoperatively, at 3 months, and after 1 and 2 years; clinical outcome was measured with the American Knee Society score (AKSS) and the knee osteoarthritis and injury outcome score (KOOS). The maximum total point motion (MTPM) for the standard stem was 0.36 (SD 0.16) mm at 3 months, 0.51 (SD 0.27) mm at 1 year, and 0.54 (SD 0.28) mm at 2 years. For the short stem, it was 0.42 (0.24) mm, 0.59 (0.43) mm, and 0.61 (0.39) mm. 4 short-stemmed components and 2 standard-stemmed components had more than 0.2 mm of migration between the first- and second-year follow-up, and were classified as continuously migrating. The short-stemmed cemented tibial prosthesis showed an early prosthetic migratory pattern similar to that of the standard-stemmed cemented Triathlon knee prosthesis. The number of continuously migrating tibial plates in each group is predictive of a lower revision rate than 5% at 10 years.

Clinical and computed tomographic evaluation of portland cement pulpotomy in primary molar: A case report

Directory of Open Access Journals (Sweden)

Kamrun Nahar

2016-08-01

Full Text Available The present case describes the clinical & radiographic outcome of a Portland Cement pulpotomy. The 5 years old girl presenting extensive carious exposure in her mandibular left 2nd deciduous molar and was suffering pain in her left lower jaw only on exposure to cold for last 2 days. She was ultimately diagnosed clinic-radio-graphically as a case of irreversible pulpitis. Coronal pulpotomy procedure was carried out in the responsible tooth and Portland cement (PC was applied as a medicament after pulpotomy. At the 3 & 6-months follow-up appointments, treated tooth was asymptomatic clinically and radiographic examinations revealed no sign of periradicular pathosis in the pulpotomized teeth. Additionally, the formation of a dentin bridge immediately below the PC in the treated tooth was confirmed by RVG and CBCT.

A Twofold Comparison between Dual Cure Resin Modified Cement and Glass Ionomer Cement for Orthodontic Band Cementation.

Science.gov (United States)

Attar, Hanaa El; Elhiny, Omnia; Salem, Ghada; Abdelrahman, Ahmed; Attia, Mazen

2016-12-15

To test the solubility of dual cure resin modified resin cement in a food simulating solution and the shear bond strength compared to conventional Glass ionomer cement. The materials tested were self-adhesive dual cure resin modified cement and Glass Ionomer (GIC). Twenty Teflon moulds were divided into two groups of tens. The first group was injected and packed with the modified resin cement, the second group was packed with GIC. To test the solubility, each mould was weighed before and after being placed in an analytical reagent for 30 days. The solubility was measured as the difference between the initial and final drying mass. To measure the Shear bond strength, 20 freshly extracted wisdom teeth were equally divided into two groups and embedded in self-cure acrylic resin. Four mm sections of stainless steel bands were cemented to the exposed buccal surfaces of teeth under a constant load of 500 g. Shear bond strength was measured using a computer controlled materials testing machine and the load required to deband the samples was recorded in Newtons. GIC showed significantly higher mean weight loss and an insignificant lower Shear bond strength, compared to dual cure resin Cement. It was found that dual cure resin modified cement was less soluble than glass ionomer cement and of comparable bond strength rendering it more useful clinically for orthodontic band cementation.

Stair climbing is more detrimental to the cement in hip replacement than walking

NARCIS (Netherlands)

Stolk, J.; Verdonschot, N.J.J.; Huiskes, H.W.J.

2002-01-01

Stair climbing may be detrimental to cemented total hip arthroplasties, because it subjects the reconstruction to high torsional loads. The current study investigated how stair climbing contributes to damage accumulation in the cement around a femoral stem compared with walking, taking into account

Femoral Component Revision with Use of Impaction Bone-Grafting and a Cemented Polished Stem: A Concise Follow-up, at Fifteen to Twenty Years, of a Previous Report*

NARCIS (Netherlands)

Te Stroet, M.A.; Gardeniers, J.W.M.; Verdonschot, N.J.; Rijnen, W.H.C.; Slooff, T.J.J.H.; Schreurs, B.W.

2012-01-01

We previously reported our results for thirty-three consecutive femoral component revisions with impaction bone-grafting, performed with the X-change femoral revision system and a cemented polished Exeter stem, at a minimum of eight years of follow-up. The present updated study shows the results

Clinical trials for stem cell therapies

Directory of Open Access Journals (Sweden)

Lomax Geoff

2011-05-01

Full Text Available Abstract In recent years, clinical trials with stem cells have taken the emerging field in many new directions. While numerous teams continue to refine and expand the role of bone marrow and cord blood stem cells for their vanguard uses in blood and immune disorders, many others are looking to expand the uses of the various types of stem cells found in bone marrow and cord blood, in particular mesenchymal stem cells, to uses beyond those that could be corrected by replacing cells in their own lineage. Early results from these trials have produced mixed results often showing minor or transitory improvements that may be attributed to extracellular factors. More research teams are accelerating the use of other types of adult stem cells, in particular neural stem cells for diseases where beneficial outcome could result from either in-lineage cell replacement or extracellular factors. At the same time, the first three trials using cells derived from pluripotent cells have begun.

Ethical clinical translation of stem cell interventions for neurologic disease

DEFF Research Database (Denmark)

Cote, David J; Bredenoord, Annelien L; Smith, Timothy R

2017-01-01

The application of stem cell transplants in clinical practice has increased in frequency in recent years. Many of the stem cell transplants in neurologic diseases, including stroke, Parkinson disease, spinal cord injury, and demyelinating diseases, are unproven-they have not been tested...... in prospective, controlled clinical trials and have not become accepted therapies. Stem cell transplant procedures currently being carried out have therapeutic aims, but are frequently experimental and unregulated, and could potentially put patients at risk. In some cases, patients undergoing such operations...... are not included in a clinical trial, and do not provide genuinely informed consent. For these reasons and others, some current stem cell interventions for neurologic diseases are ethically dubious and could jeopardize progress in the field. We provide discussion points for the evaluation of new stem cell...

The Use of a Modular Titanium Baseplate with a Press-Fit Keel Implanted with a Surface Cementing Technique for Primary Total Knee Arthroplasty

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Christopher E. Pelt

2014-01-01

Full Text Available Little data exists regarding outcomes following TKA performed with surface-cementation for the fixation of modular tibial baseplates with press-fit keels. Thus, we retrospectively reviewed the clinical and radiographic outcomes of 439 consecutive primary TKAs performed with surface cemented tibial components. There were 290 female patients and 149 male patients with average age of 62 years (range 30–84. Two tibial components were revised for aseptic loosening (0.5% and four tibial components (0.9% were removed to improve instability (n=2 or malalignment (n=2. Complications included 13 deep infections treated with 2-stage revision (12 and fusion (1. These results support the surface cement technique with a modular grit-blasted titanium surface and cruciform stem during primary TKA.

Can Arthroplasty Stem INfluence Outcome? (CASINO): a randomized controlled equivalence trial of 125 mm versus 150 mm Exeter V40 stems in total hip arthroplasty.

Science.gov (United States)

Hamilton, David F; Ohly, Nicholas E; Gaston, Paul

2018-04-16

The use of shorter length femoral stems during total hip arthroplasty has been suggested to accommodate wider patient femoral geometry and offer maximal bone preservation. However, cemented short-stem designs may increase the risk of varus stem malalignment and influence patient outcomes. CASINO is a multi-centre randomised equivalence trial that will recruit 220 patients undergoing total hip arthroplasty for osteoarthritis at two NHS hospitals in Scotland. Patients will be aged 45-80, undergoing unilateral primary hip arthroplasty, with no plan for contralateral procedure within the study timeframe, and able to comply with the protocol. Participants will be randomised to receive either a short (125 mm) or a standard (150 mm) Exeter V40 stem. The Contemporary acetabular component will be used in all cases. All implants will be cemented. Patient pain, function and satisfaction will be assessed using change from baseline measurement in Oxford Hip Score, Forgotten Joint Score, EQ-5D, pain numerical rating scores, and patient satisfaction questionnaire at baseline and at 1 and 2 years following surgery. Radiographic assessment will evaluate stem position and will be appraised by independent reviewers. Patients will be blind to implant allocation. Stem length may be associated with outcome; however, we can find no randomised trial in which researchers investigated the effect of stem length on patient outcome following cemented total hip arthroplasty. The aim of this trial is to determine if the use of short cemented stems offers equivalent patient outcomes to those achieved following surgery with standard length stems. International Standard Randomised Controlled Trial Number, ISRCTN13154542 , Registered on 30 June 2017.

The Corail stem as a reverse hybrid - survivorship and x-ray analysis at 10 years.

Science.gov (United States)

Wangen, Helge; Nordsletten, Lars; Boldt, Jens G; Fenstad, Anne M; Beverland, David E

2017-07-25

The use of a cemented cup together with an uncemented stem in total hip arthroplasty (THA) has become popular in Norway and Sweden during the last decade. The results of this prosthetic concept, reverse hybrid THA have been sparsely described.We report our experience of reverse hybrid THA, using the Elite plus polyethylene cemented cup together with the Corail fully hydroxyapatite-coated uncemented stem and a 28-mm alumina ceramic head. 132 consecutive reverse hybrid hip arthroplasties were performed from January 2000 to December 2003 in 126 patients with a mean age of 54.3 years (28-65). All patients were routinely reviewed at 3 months, 1, 5, 7 and 10 years postoperatively. At each follow-up patients were seen either by a consultant orthopaedic surgeon or a senior trainee. Anteroposterior pelvic and lateral x-rays of the hip were taken at each visit. To estimate the survival of the THAs we used the Kaplan-Meier method with 95% confidence interval (CI). Logistic regression analysis was performed to determine which factors affected the presence of radiolucency around the femoral stem. The mean follow-up was 11.1 years (9.0-14.2). 1 patient was lost to follow-up, and 7 patients were deceased at the time of 10-year follow up. At 10 years 7 patients have had further surgery. 5 for infection, 1 periprosthetic femoral fracture and 1 heterotopic bone formation. All stems were classified as well fixed. 2 cups were defined as loose at 10 years. 1 patient is scheduled for revision the other refused revision. The clinical outcome and radiological findings were assessed in 123 hips. The mean Harris Hip Score was 94 (35-100) at 10 years and the mean WOMAC score was 89 (30.2-100). We report good results with respect to clinical outcome and survival of the reverse hybrid concept in patients younger than 65. A successful outcome depends on meticulous preoperative planning, use of modern cementing techniques in the acetabulum and experience in implanting an uncemented stem.

Migration and strains induced by different designs of force-closed stems for THA.

Science.gov (United States)

Griza, Sandro; Gomes, Luiz Sérgio Marcelino; Cervieri, André; Strohaecker, Telmo Roberto

2015-01-01

Subtle differences in stem design can result in different mechanical responses of the total hip arthroplasty. Tests measuring migration of the stem relative to the femur, as well as the strains in the cement mantle and on the femur can detect different mechanical behavior between stems. In this article, conical, double and triple tapered stems were implanted in composite femurs and subjected to static and cyclic loads. Stems differed mainly on taper angle, calcar radius and proximal stiffness. Stem migration and strains on the femur and in the cement mantle were achieved. Significant differences (p mechanical tests were able to detect significant differences in the behavior of these resembling stems. Stem proximal stiffness and the calcar radius of the stem influence its rotational stability and the strain transmission to the femur.

A New Biphasic Dicalcium Silicate Bone Cement Implant

Directory of Open Access Journals (Sweden)

Fausto Zuleta

2017-07-01

Full Text Available This study aimed to investigate the processing parameters and biocompatibility of a novel biphasic dicalcium silicate (C2S cement. Biphasic α´L + β-C2Sss was synthesized by solid-state processing, and was used as a raw material to prepare the cement. In vitro bioactivity and biocompatibility studies were assessed by soaking the cement samples in simulated body fluid (SBF and human adipose stem cell cultures. Two critical-sized defects of 6 mm Ø were created in 15 NZ tibias. A porous cement made of the high temperature forms of C2S, with a low phosphorous substitution level, was produced. An apatite-like layer covered the cement’s surface after soaking in SBF. The cell attachment test showed that α´L + β-C2Sss supported cells sticking and spreading after 24 h of culture. The cement paste (55.86 ± 0.23 obtained higher bone-to-implant contact (BIC percentage values (better quality, closer contact in the histomorphometric analysis, and defect closure was significant compared to the control group (plastic. The residual material volume of the porous cement was 35.42 ± 2.08% of the initial value. The highest BIC and bone formation percentages were obtained on day 60. These results suggest that the cement paste is advantageous for initial bone regeneration.

CEMENT SLURRIES FOR GEOTHERMAL WELLS CEMENTING

Directory of Open Access Journals (Sweden)

Nediljka Gaurina-Međimurec

1994-12-01

Full Text Available During a well cementing special place belongs to the cement slurry design. To ensure the best quality of cementing, a thorough understanding of well parameters is essential, as well as behaviour of cement slurry (especially at high temperatures and application of proven cementing techniques. Many cement jobs fail because of bad job planning. Well cementing without regarding what should be accomplished, can lead to well problems (channels in the cement, unwanted water, gas or fluid production, pipe corrosion and expensive well repairs. Cementing temperature conditions are important because bot-tomhole circulating temperatures affect slurry thickening time, arheology, set time and compressive strength development. Knowing the actual temperature which cement encounters during placement allows the selection of proper cementing materials for a specific application. Slurry design is affected by well depth, bottom hole circulating temperature and static temperature, type or drilling fluid, slurry density, pumping time, quality of mix water, fluid loss control, flow regime, settling and free water, quality of cement, dry or liquid additives, strength development, and quality of the lab cement testing and equipment. Most Portland cements and Class J cement have shown suitable performances in geot-hermal wells. Cement system designs for geothermal wells differ from those for conventional high temperature oil and gas wells in the exclusive use of silica flour instead of silica sand, and the avoidance of fly ash as an extender. In this paper, Portland cement behaviour at high temperatures is described. Cement slurry and set cement properties are also described. Published in literature, the composition of cement slurries which were tested in geothermal conditions and which obtained required compressive strength and water permeability are listed. As a case of our practice geothermal wells Velika Ciglena-1 and Velika Ciglena-la are described.

Cemental tear: To know what we have neglected in dental practice

Directory of Open Access Journals (Sweden)

Po-Yuan Jeng

2018-04-01

Full Text Available Cemental tear is a special kind of root surface fracture, contributing to periodontal and periapical breakdown. However, it is a challenge for doctors to diagnose, resulting in delayed or improper treatment. We reviewed the predisposing factors, location, radiographic/clinical characteristics, diagnosis and treatments of cemental tears. From the literature, patients with cemental tear were mainly males, over 60 year-old. Possible predisposing factors include gender, age, tooth type, traumatic occlusal force and vital teeth. Cemental tears were common in upper and lower anterior teeth, single or multiple, and can be present in cervical, middle and apical third of roots. Morphology of cemental tears can be either piece-shaped or U-shaped. Clinically, cemental tear shows a unitary periodontal pocket and signs/symptoms mimicking localized periodontitis, apical periodontitis and vertical root fractures. Treatment of cemental tears include scaling, root planning, root canal treatment, periodontal/periapical surgery, guided tissue regeneration, bone grafting, and intentional replantation. Recurrence of cemental tear is possible especially when the fracture involves root apex. Extraction is recommended for teeth with poor prognosis. In conclusion, cemental tears can involve both periodontal and periapical area. Dentists should understand the predisposing factors and clinical features of cemental tears for early diagnosis/treatment to prevent bone loss/tooth extraction. Keywords: Cemental tear, Clinical characteristics, Surface root fracture, Periodontal/periapical breakdown, Recurrence, Predisposing factors

Mammary Stem Cells and Breast Cancer Stem Cells: Molecular Connections and Clinical Implications.

Science.gov (United States)

Celià-Terrassa, Toni

2018-05-04

Cancer arises from subpopulations of transformed cells with high tumor initiation and repopulation ability, known as cancer stem cells (CSCs), which share many similarities with their normal counterparts. In the mammary gland, several studies have shown common molecular regulators between adult mammary stem cells (MaSCs) and breast cancer stem cells (bCSCs). Cell plasticity and self-renewal are essential abilities for MaSCs to maintain tissue homeostasis and regenerate the gland after pregnancy. Intriguingly, these properties are similarly executed in breast cancer stem cells to drive tumor initiation, tumor heterogeneity and recurrence after chemotherapy. In addition, both stem cell phenotypes are strongly influenced by external signals from the microenvironment, immune cells and supportive specific niches. This review focuses on the intrinsic and extrinsic connections of MaSC and bCSCs with clinical implications for breast cancer progression and their possible therapeutic applications.

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.

Evaluation of stainless steel crowns cemented with glass-ionomer and resin-modified glass-ionomer luting cements.

Science.gov (United States)

Yilmaz, Yucel; Simsek, Sera; Dalmis, Anya; Gurbuz, Taskin; Kocogullari, M Elcin

2006-04-01

To evaluate in vitro and in vivo conditions of stainless steel crowns (SSC) cemented using one luting glass-ionomer cement (Aqua Meron) and one luting resin-modified glass-ionomer cement (Vitremer). In the in vitro part of this study, retentive properties of SSCs cemented using Aqua Meron and Vitremer on extracted primary first molars were tested. In addition, two specimens of each group were used to evaluate the tooth hard tissue-cement, within the cement itself, cement-SSC, and tooth hard tissue-cement-SSC under scanning electron microscope (SEM). In the in vivo part of this study, 152 SSCs were placed on the first or second primary molars of 86 children, and cemented using either Aqua Meron or Vitremer. The crowns were examined for retention. In addition, the clinical views of the crowns were recorded with an intraoral camera. No significant difference was found between the mean retentive forces of Aqua Meron and Vitremer (P> 0.05). SSCs cemented with Aqua Meron and Vitremer had an average lifespan of 26.44 and 24.07 months respectively. Only one (0.66%) of 152 SSCs was lost from the Aqua Meron group during post-cementation periods. Nineteen of the 152 SSCs (12.5%) had dents or perforations.

Stem cell tourism--a web-based analysis of clinical services available to international travellers.

Science.gov (United States)

Connolly, Ruairi; O'Brien, Timothy; Flaherty, Gerard

2014-01-01

Stem cell therapies are advertised through online resources which describe a range of treatments with diverse clinical indications. Stem cell tourists may not be aware of the information they should seek when consulting these clinics, or of the potential risks involved. The aim of this study was to characterise the therapies offered by online stem cell clinics. A web based search utilising five search terms was employed. The first twenty pages of each search result were screened against 340 variables. 224 out of 1091 websites advertised stem cell clinics. 68 eligible sites covering 21 countries were evaluated. The top five clinical indications for stem cell therapy were multiple sclerosis, anti-ageing, Parkinson's disease, stroke and spinal cord injury. Adult, autologous stem cells were the most commonly utilised stem cell, and these were frequently sourced from bone marrow and adipose tissue and administered intravenously. Thirty-four per cent of sites mentioned the number of patients treated while one quarter of clinics provided outcome data. Twenty-nine per cent of clinics had an internationally recognised accreditation. Fifteen per cent of clinics stated that their therapies posed no risk. Eighty-eight per cent of clinics claimed treatment effectiveness, with 16% describing their curative potential. Over 40% of sites did not specify the number or duration of treatments. Fifty-three per cent of clinics requested access to patients' medical records, and 12% recommended patients discuss the proposed therapy with their doctor. No clinic recommended that travellers consult a travel medicine specialist or receive vaccinations prior to their intended travel. One quarter of sites discussed contraindications to treatment, with 41% of sites detailing follow up patient care. There is potential for stem cell tourists to receive misleading or deficient information from online stem cell clinics. Both the stem cell tourist and travel medicine practitioner should be educated

CIRM Alpha Stem Cell Clinics: Collaboratively Addressing Regenerative Medicine Challenges.

Science.gov (United States)

Jamieson, Catriona H M; Millan, Maria T; Creasey, Abla A; Lomax, Geoff; Donohoe, Mary E; Walters, Mark C; Abedi, Mehrdad; Bota, Daniela A; Zaia, John A; Adams, John S

2018-06-01

The California Institute for Regenerative Medicine (CIRM) Alpha Stem Cell Clinic (ASCC) Network was launched in 2015 to address a compelling unmet medical need for rigorous, FDA-regulated, stem cell-related clinical trials for patients with challenging, incurable diseases. Here, we describe our multi-center experiences addressing current and future challenges. Copyright © 2018 Elsevier Inc. All rights reserved.

Representations of stem cell clinics on Twitter.

Science.gov (United States)

Kamenova, Kalina; Reshef, Amir; Caulfield, Timothy

2014-12-01

The practice of travelling abroad to receive unproven and unregulated stem cell treatments has become an increasingly problematic global phenomenon known as 'stem cell tourism'. In this paper, we examine representations of nine major clinics and providers of such treatments on the microblogging network Twitter. We collected and conducted a content analysis of Twitter posts (n = 363) by these establishments and by other users mentioning them, focusing specifically on marketing claims about treatment procedures and outcomes, discussions of safety and efficacy of stem cell transplants, and specific representations of patients' experiences. Our analysis has shown that there were explicit claims or suggestions of benefits associated with unproven stem cell treatments in approximately one third of the tweets and that patients' experiences, whenever referenced, were presented as invariably positive and as testimonials about the efficacy of stem cell transplants. Furthermore, the results indicated that the tone of most tweets (60.2 %) was overwhelmingly positive and there were rarely critical discussions about significant health risks associated with unproven stem cell therapies. When placed in the context of past research on the problems associated with the marketing of unproven stem cell therapies, this analysis of representations on Twitter suggests that discussions in social media have also remained largely uncritical of the stem cell tourism phenomenon, with inaccurate representations of risks and benefits for patients.

Low pH Cements

International Nuclear Information System (INIS)

Savage, David; Benbow, Steven

2007-05-01

The development of low-pH cements for use in geological repositories for radioactive waste stems from concerns over the potential for deleterious effects upon the host rock and other EBS materials (notably bentonite) under the hyperalkaline conditions (pH > 12) of cement pore fluids. Low pH cement (also known as low heat cement) was developed by the cement industry for use where large masses of cement (e.g. dams) could cause problems regarding heat generated during curing. In low pH cements, the amount of cement is reduced by substitution of materials such as fly ash, blast furnace slag, silica fume, and/or non-pozzolanic silica flour. SKB and Posiva have ruled out the use of blast furnace slag and fly-ash and are focusing on silica fume as a blending agent. Currently, no preferred composition has been identified by these agencies. SKB and Posiva have defined a pH limit ≤ 11 for cement grout leachates. To attain this pH, blending agents must comprise at least 50 wt % of dry materials. Because low pH cement has little, or no free portlandite, the cement consists predominantly of calcium silicate hydrate (CSH) gel with a Ca/Si ratio ≤ 0.8. Although there are potential implications for the performance of the spent fuel and cladding due to the presence of hyperalkaline fluids from cement, the principal focus for safety assessment lies with the behaviour of bentonite. There are a number of potential constraints on the interaction of hyperalkaline cement pore fluids with bentonite, including mass balance, thermodynamic issues, mass transport, and kinetics, but none of these is likely to be limiting if conventional OPC cements are employed in repository construction. Nevertheless: Low-pH cements may supply approximately 50 % less hydroxyl ions than conventional OPC for a given volume of cement, but mass balance constraints are complicated by the uncertainty concerning the type of secondary minerals produced during cement-bentonite interaction. The change of aqueous

Low pH Cements

Energy Technology Data Exchange (ETDEWEB)

Savage, David; Benbow, Steven [Quintessa Ltd., Henley-on-Thames (United Kingdom)

2007-05-15

The development of low-pH cements for use in geological repositories for radioactive waste stems from concerns over the potential for deleterious effects upon the host rock and other EBS materials (notably bentonite) under the hyperalkaline conditions (pH > 12) of cement pore fluids. Low pH cement (also known as low heat cement) was developed by the cement industry for use where large masses of cement (e.g. dams) could cause problems regarding heat generated during curing. In low pH cements, the amount of cement is reduced by substitution of materials such as fly ash, blast furnace slag, silica fume, and/or non-pozzolanic silica flour. SKB and Posiva have ruled out the use of blast furnace slag and fly-ash and are focusing on silica fume as a blending agent. Currently, no preferred composition has been identified by these agencies. SKB and Posiva have defined a pH limit {<=} 11 for cement grout leachates. To attain this pH, blending agents must comprise at least 50 wt % of dry materials. Because low pH cement has little, or no free portlandite, the cement consists predominantly of calcium silicate hydrate (CSH) gel with a Ca/Si ratio {<=} 0.8. Although there are potential implications for the performance of the spent fuel and cladding due to the presence of hyperalkaline fluids from cement, the principal focus for safety assessment lies with the behaviour of bentonite. There are a number of potential constraints on the interaction of hyperalkaline cement pore fluids with bentonite, including mass balance, thermodynamic issues, mass transport, and kinetics, but none of these is likely to be limiting if conventional OPC cements are employed in repository construction. Nevertheless: Low-pH cements may supply approximately 50 % less hydroxyl ions than conventional OPC for a given volume of cement, but mass balance constraints are complicated by the uncertainty concerning the type of secondary minerals produced during cement-bentonite interaction. The change of aqueous

Cement-Induced Chromate Occupational Allergic Contact Dermatitis.

Science.gov (United States)

Kridin, Khalaf; Bergman, Reuven; Khamaisi, Mogher; Zelber-Sagi, Shira; Weltfriend, Sara

2016-01-01

Hexavalent chromium in cement is a common cause of occupational allergic contact dermatitis (OACD). Analysis of patch test data during 1999 to 2013 was done. Patients with cement-induced chromate OACD filled the Dermatology Life Quality Index, graded 1 to 5. Of 4846 consecutive patients who were patch tested, 146 (3%) were chromate-sensitive. Of 46 (31.5%) who presented with chromate OACD, 27 (59%) had cement-induced chromate OACD. The proportion of chromate-sensitive patients with clinically relevant cement exposure increased from 7.7% in 2002 to 2004 to 28.7% in 2011 to 2013 (P = 0.04). The median age of presentation was younger than for other chromate-sensitive patients (32 vs 42 years). Hand eczema (88.9%) was the most frequent clinical presentation. Of the 27 with cement-induced chromate OACD, 21 (77.8%) had ongoing dermatitis at the time of the review. Although 14/27 (51.9%) changed their occupation to avoid exposure to cement, symptoms persisted in 9/14 (64.3%). Prolonged exposure to cement before development of symptoms was associated with chronicity. All the symptomatic patients experienced at least a moderate effect on their quality of life (grade 3 or higher on the Dermatology Life Quality Index). We recommend the adoption of the European legislation in Israel, to reduce the prevalence of chromate OACD from cement.

A randomized study on migration of the Spectron EF and the Charnley flanged 40 cemented femoral components using radiostereometric analysis at 2 years.

Science.gov (United States)

Kadar, Thomas; Hallan, Geir; Aamodt, Arild; Indrekvam, Kari; Badawy, Mona; Havelin, Leif Ivar; Stokke, Terje; Haugan, Kristin; Espehaug, Birgitte; Furnes, Ove

2011-10-01

We performed a randomized study to determine the migration patterns of the Spectron EF femoral stem and to compare them with those of the Charnley stem, which is regarded by many as the gold standard for comparison of implants due to its extensive documentation. 150 patients with a mean age of 70 years were randomized, single-blinded, to receive either a cemented Charnley flanged 40 monoblock, stainless steel, vaquasheen surface femoral stem with a 22.2-mm head (n = 30) or a cemented Spectron EF modular, matte, straight, collared, cobalt-chrome femoral stem with a 28-mm femoral head and a roughened proximal third of the stem (n = 120). The patients were followed with repeated radiostereometric analysis for 2 years to assess migration. At 2 years, stem retroversion was 2.3° and 0.7° (p < 0.001) and posterior translation was 0.44 mm and 0.17 mm (p = 0.002) for the Charnley group (n = 26) and the Spectron EF group (n = 74), respectively. Subsidence was 0.26 mm for the Charnley and 0.20 mm for the Spectron EF (p = 0.5). The Spectron EF femoral stem was more stable than the Charnley flanged 40 stem in our study when evaluated at 2 years. In a report from the Norwegian arthroplasty register, the Spectron EF stem had a higher revision rate due to aseptic loosening beyond 5 years than the Charnley. Initial stability is not invariably related to good long-term results. Our results emphasize the importance of prospective long-term follow-up of prosthetic implants in clinical trials and national registries and a stepwise introduction of implants.

Can finite element models detect clinically inferior cemented hip implants?

NARCIS (Netherlands)

Stolk, J.; Maher, S.A.; Verdonschot, N.J.J.; Prendergast, P.J.; Huiskes, R.

2003-01-01

Rigorous preclinical testing of cemented hip prostheses against the damage accumulation failure scenario will reduce the incidence of aseptic loosening. For that purpose, a finite element simulation is proposed that predicts damage accumulation in the cement mantle and prosthetic migration. If the

Cytotoxic effects of glass ionomer cements on human dental pulp stem cells correlate with fluoride release.

Science.gov (United States)

Kanjevac, Tatjana; Milovanovic, Marija; Volarevic, Vladislav; Lukic, Miodrag L; Arsenijevic, Nebojsa; Markovic, Dejan; Zdravkovic, Nebojsa; Tesic, Zivoslav; Lukic, Aleksandra

2012-01-01

Glass ionomer cements (GICs) are commonly used as restorative materials. Responses to GICs differ among cell types and it is therefore of importance to thoroughly investigate the influence of these restorative materials on pulp stem cells that are potential source for dental tissue regeneration. Eight biomaterials were tested: Fuji I, Fuji II, Fuji VIII, Fuji IX, Fuji Plus, Fuji Triage, Vitrebond and Composit. We compared their cytotoxic activity on human dental pulp stem cells (DPSC) and correlated this activity with the content of Fluoride, Aluminium and Strontium ions in their eluates. Elution samples of biomaterials were prepared in sterile tissue culture medium and the medium was tested for toxicity by an assay of cell survival/proliferation (MTT test) and apoptosis (Annexin V FITC Detection Kit). Concentrations of Fluoride, Aluminium and Strontium ions were tested by appropriate methods in the same eluates. Cell survival ranged between 79.62% (Fuji Triage) to 1.5% (Fuji Plus) and most dead DPSCs were in the stage of late apoptosis. Fluoride release correlated with cytotoxicity of GICs, while Aluminium and Strontium ions, present in significant amount in eluates of tested GICs did not. Fuji Plus, Vitrebond and Fuji VIII, which released fluoride in higher quantities than other GICs, were highly toxic to human DPSCs. Opposite, low levels of released fluoride correlated to low cytotoxic effect of Composit, Fuji I and Fuji Triage.

HDAC inhibitor-loaded bone cement for advanced local treatment of osteosarcoma and chondrosarcoma.

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Tonak, Marcus; Becker, Marc; Graf, Claudine; Eckhard, Lukas; Theobald, Matthias; Rommens, Pol-Maria; Wehler, Thomas C; Proschek, Dirk

2014-11-01

The treatment of osteosarcoma, especially wide resection, is challenging. An additional local drug therapy after resection using anti-neoplastic bone cement (Polymethylmethacrylate (PMMA)) could help improve the outcome of therapy. In this study, we evaluated the effects of PMMA loaded with valproic acid (VPA) and suberoylanilide hydroxamic acid (SAHA) on the cell activity of a SaOs-2 cell culture, as well as the elution rate of the drugs out of the bone cement. In our experiments, we used the SaOs-2 osteosarcoma and the SW1353 chondrosarcoma cell line. Bone cement clots (5 g) were prepared and loaded with different drug concentrations of VPA (25 mg and 50 mg) and SAHA (1 mg, 2.5 mg and 5 mg). Two control groups were established, one with a native cement clot, the other with human mesenchymal stem cells, in order to evaluate toxicity on non tumor-cells. Cell activity was measured using an Alamar Blue assay on days 1, 2, 3, 4 and 7. The cement clots were additionally examined in a material testing unit for biomechanical and structural changes. Tumor cells showed a significant and complete reduction of activity under therapy with VPA and SAHA. Drug release of VPA was extensive between days 0 and 3 and decreased progressively to day 7. Cumulative drug concentration in the medium continuously increased. Biomechanical testing of the cement clots showed no differences in stability and architecture compared to the control group. SaOs-2 and SW1353 cells with medium from native cement clots without drug therapy presented a cell activity of 100% in all groups and during all measurements. Human mesenchymal stem cells were not significantly affected during therapy with VPA and low concentrations of SAHA. In contrast, cell activity of human mesenchymal stem cells was significantly reduced under therapy with higher concentrations of SAHA, with an approximately linear decrease between days 0-3 and a rapidly decreasing activity between days 4-7. A local cytotoxic therapy in the

Low-cost glass ionomer cement as ART sealant in permanent molars: a randomized clinical trial

NARCIS (Netherlands)

Hesse, D.; Bonifácio, C.C.; Guglielmi, C. de Almeida Brandao; da Franca, C.; Mendes, F.M.; Raggio, D.P.

2015-01-01

Clinical trials are normally performed with well-known brands of glass ionomer cement (GIC), but the cost of these materials is high for public healthcare in less-affluent communities. Given the need to research cheaper materials, it seems pertinent to investigate the retention rate of a low-cost

The effect of distal ulnar implant stem material and length on bone strains.

Science.gov (United States)

Austman, Rebecca L; Beaton, Brendon J B; Quenneville, Cheryl E; King, Graham J W; Gordon, Karen D; Dunning, Cynthia E

2007-01-01

Implant design parameters can greatly affect load transfer from the implant stem to the bone. We have investigated the effect of length or material of distal ulnar implant stems on the surrounding bone strains. Eight cadaveric ulnas were instrumented with 12 strain gauges and secured in a customized jig. Strain data were collected while loads (5-30 N) were applied to the medial surface of the native ulnar head. The native ulnar head was removed, and a stainless steel implant with an 8-cm-long finely threaded stem was cemented into the canal. After the cement had cured, the 8-cm stem was removed, leaving a threaded cement mantle in the canal that could accept shorter threaded stems of interest. The loading protocol was then repeated for stainless steel stems that were 7, 5, and 3 cm in length, as well as for a 5-cm-long titanium alloy (TiAl(6)V(4)) stem. Other stainless steel stem lengths between 3 and 7 cm were tested at intervals of 0.5 cm, with only a 20 N load applied. No stem length tested matched the native strains at all gauge locations. No significant differences were found between any stem length and the native bone at the 5th and 6th strain gauge positions. Strains were consistently closer to the native bone strains with the titanium stem than the stainless steel stem for each gauge pair that was positioned on the bone overlying the stem. The 3-cm stem results were closer to the native strains than the 7-cm stem for all loads at gauges locations that were on top of the stem. The results from this study suggest that the optimal stem characteristics for distal ulnar implants from a load transfer point of view are possessed by shorter (approximately 3 to 4 cm) titanium stems.

Migration characteristics and early clinical results of the NANOS® short-stem hip arthroplasty.

Science.gov (United States)

Kaipel, Martin; Grabowiecki, Phillip; Sinz, Katrina; Farr, Sebastian; Sinz, Günter

2015-05-01

Femoral short stems promise essential advantages in total hip arthroplasty. Up to now, only short- and midterm clinical studies exist. Data on early stem migration that could predict later aseptic loosening at an early stage are rare. The purpose of this study was to assess migration patterns and clinical outcome 2 years after hip replacement by a metaphyseal anchored cementless short stem. Migration data and clinical results were prospectively assessed in 49 patients. Clinical outcome was measured using the Harris Hip Score (HHS). Migration analyses were performed using the computer-assisted Einzel-Bild-Roentgen-Analyse (EBRA) system. At 2 years after surgery, none of the implants needed revision, and HHS increased from 47.9 up to 98.1. Of 49 patients, 5 (10%) showed increased vertical stem migration (1.5 mm/2a) that might predict late aseptic loosening. Of 49 stems, 44 (90%) showed stable migration patterns indicating a beneficial long-term outcome. Results of this study confirm the excellent clinical data of previous works. Migration patterns strongly suggest that short-stem arthroplasty is not only an innovative but also a reliable strategy in total hip replacement.

Adipose Derived Mesenchymal Stem Cells In Wound Healing: A Clinical Review

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Gunalp Uzun

2014-08-01

Full Text Available The aim of this article is to review clinical studies on the use of adipose derived mesenchymal stem cells in the treatment of chronic wounds. A search on PubMed was performed on April 30th, 2014 to identify the relevant clinical studies. We reviewed 13 articles that reported the use adipose derived stem cells in the treatment of different types of wounds. Adipose derived stem cells have the potential to be used in the treatment of chronic wounds. However, standard methods for isolation, storage and application of these cells are needed. New materials to transfer these stem cells to injured tissues should be investigated. [Dis Mol Med 2014; 2(4.000: 57-64

Chemical and physical properties of bone cement for vertebroplasty

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Po-Liang Lai

2013-08-01

Full Text Available Vertebral compression fracture is the most common complication of osteoporosis. It may result in persistent severe pain and limited mobility, and significantly impacts the quality of life. Vertebroplasty involves a percutaneous injection of bone cement into the collapsed vertebrae by fluorescent guide. The most commonly used bone cement in percutaneous vertebroplasty is based on the polymerization of methylmethacrylate monomers to polymethylmethacrylate (PMMA polymers. However, information on the properties of bone cement is mostly published in the biomaterial sciences literature, a source with which the clinical community is generally unfamiliar. This review focuses on the chemistry of bone cement polymerization and the physical properties of PMMA. The effects of altering the portions and contents of monomer liquid and polymer powders on the setting time, polymerization temperature, and compressive strength of the cement are also discussed. This information will allow spine surgeons to manipulate bone cement characteristics for specific clinical applications and improve safety.

The effect of cup outer sizes on the contact mechanics and cement fixation of cemented total hip replacements.

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Hua, Xijin; Li, Junyan; Wang, Ling; Wilcox, Ruth; Fisher, John; Jin, Zhongmin

2015-10-01

One important loosening mechanism of the cemented total hip arthroplasty is the mechanical overload at the bone-cement interface and consequent failure of the cement fixation. Clinical studies have revealed that the outer diameter of the acetabular component is a key factor in influencing aseptic loosening of the hip arthroplasty. The aim of the present study was to investigate the influence of the cup outer diameter on the contact mechanics and cement fixation of a cemented total hip replacement (THR) with different wear penetration depths and under different cup inclination angles using finite element (FE) method. A three-dimensional FE model was developed based on a typical Charnley hip prosthesis. Two acetabular cup designs with outer diameters of 40 and 43 mm were modelled and the effect of cup outer diameter, penetration depth and cup inclination angle on the contact mechanics and cement fixation stresses in the cemented THR were studied. The results showed that for all penetration depths and cup inclination angles considered, the contact mechanics in terms of peak von Mises stress in the acetabular cup and peak contact pressure at the bearing surface for the two cup designs were similar (within 5%). However, the peak von Mises stress, the peak maximum principal stress and peak shear stress in the cement mantle at the bone-cement interface for the 43 mm diameter cup design were predicted to be lower compared to those for the 40 mm diameter cup design. The differences were predicted to be 15-19%, 15-22% and 18-20% respectively for different cup penetration depths and inclination angles, which compares to the clinical difference of aseptic loosening incidence of about 20% between the two cup designs. Copyright © 2015 IPEM. Published by Elsevier Ltd. All rights reserved.

Hurdles to clinical translation of human induced pluripotent stem cells.

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Neofytou, Evgenios; O'Brien, Connor Galen; Couture, Larry A; Wu, Joseph C

2015-07-01

Human pluripotent stem cells are known to have the capacity to renew indefinitely, being intrinsically able to differentiate into many different cell types. These characteristics have generated tremendous enthusiasm about the potential applications of these cells in regenerative medicine. However, major challenges remain with the development and testing of novel experimental stem cell therapeutics in the field. In this Review, we focus on the nature of the preclinical challenges and discuss potential solutions that could help overcome them. Furthermore, we discuss the use of allogeneic versus autologous stem cell products, including a review of their respective advantages and disadvantages, major clinical requirements, quality standards, time lines, and costs of clinical grade development.

Modified cementless total coxofemoral prosthesis: development, implantation and clinical evaluation

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S.A. Arias

2013-12-01

Full Text Available The aim of this study was to modify canine coxofemoral prostheses and the clinical evaluation of the implantation. Fifteen canine hips and femora of cadavers were used in order to study the surface points of modification in prostheses and develop a perforation guide. Femoral stems and acetabular components were perforated and coated with biphasic calcium phosphate layer. Twelve young adult male mongrel dogs were implanted with coxofemoral prostheses. Six were operated upon and implanted with cemented canine modular hip prostheses, establishing the control group. The remaining six were implanted with a novel design of cementless porous tricalcic phosphate-hydroxyapatite coated hip prostheses. Clinical and orthopedic performance, complications, and thigh muscular hypotrophy were assessed up to the 120th post-operatory day. After 120 days, animals with cementless prostheses had similar clinical and orthopedic performance compared to the cemented group despite the increased pain thigh hypotrophy. Animals that underwent cementless hip prosthesis evidenced more pain, compared to animals with cemented hip prosthesis that required longer recuperation time. No luxations, two fractures and two isquiatic neurapraxies were identified in the course of the study. Using both the cemented and the bioactive coated cementless model were suitable to dogs, showing clinical satisfactory results. Osseointegration and biological fixation were observed in the animals with the modified cementless hip prosthesis.

Cement pulmonary embolism after vertebroplasty.

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Sifuentes Giraldo, Walter Alberto; Lamúa Riazuelo, José Ramón; Gallego Rivera, José Ignacio; Vázquez Díaz, Mónica

2013-01-01

In recent years, the use of vertebral cementing techniques for vertebroplasty and kyphoplasty has spread for the treatment of pain associated with osteoporotic vertebral compression fractures. This is also associated with the increased incidence of complications related with these procedures, the most frequent being originated by leakage of cementation material. Cement can escape into the vertebral venous system and reach the pulmonary circulation through the azygous system and cava vein, producing a cement embolism. This is a frequent complication, occurring in up to 26% of patients undergoing vertebroplasty but, since most patients have no clinical or hemodynamical repercussion, this event usually goes unnoticed. However, some serious, and even fatal cases, have been reported. We report the case of a 74-year-old male patient who underwent vertebroplasty for persistent pain associated with osteoporotic L3 vertebral fracture and who developed a cement leak into the cava vein and right pulmonary artery during the procedure. Although he developed a pulmonary cement embolism, the patient remained asymptomatic and did not present complications during follow-up. Copyright © 2012 Elsevier España, S.L. All rights reserved.

High risk of early periprosthetic fractures after primary hip arthroplasty in elderly patients using a cemented, tapered, polished stem

Science.gov (United States)

Brodén, Cyrus; Mukka, Sebastian; Muren, Olle; Eisler, Thomas; Boden, Henrik; Stark, André; Sköldenberg, Olof

2015-01-01

Background and purpose Postoperative periprosthetic femoral fracture (PPF) after hip arthroplasty is associated with considerable morbidity and mortality. We assessed the incidence and characteristics of periprosthetic fractures in a consecutive cohort of elderly patients treated with a cemented, collarless, polished and tapered femoral stem (CPT). Patients and methods In this single-center prospective cohort study, we included 1,403 hips in 1,357 patients (mean age 82 (range 52–102) years, 72% women) with primary osteoarthritis (OA) or a femoral neck fracture (FNF) as indication for surgery (367 hips and 1,036 hips, respectively). 64% of patients were ASA class 3 or 4. Hip-related complications and need for repeat surgery were assessed at a mean follow-up time of 4 (1–7) years. A Cox regression analysis was used to evaluate risk factors associated with PPF. Results 47 hips (3.3%) sustained a periprosthetic fracture at median 7 (2–79) months postoperatively; 41 were comminute Vancouver B2 or complex C-type fractures. The fracture rate was 3.8% for FNF patients and 2.2% for OA patients (hazard ratio (HR) = 4; 95% CI: 1.3–12). Patients > 80 years of age also had a higher risk of fracture (HR = 2; 95% CI: 1.1–4.5). Interpretation We found a high incidence of early PPF associated with the CPT stem in this old and frail patient group. A possible explanation may be that the polished tapered stem acts as a wedge, splitting the femur after a direct hip contusion. Our results should be confirmed in larger, registry-based studies, but we advise caution when using this stem for this particular patient group. PMID:25280133

Strength Characteristics of Groundnut Leaf/Stem Ash (GLSA) Concrete

Science.gov (United States)

Oseni, O. W.; Audu, M. T.

2016-09-01

The compressive strength properties of concrete are substantial factors in the design and construction of concrete structures. Compressive strength directly affects the degree to which the concrete can be able to carry a load over time. These changes are complemented by deflections, cracks etc., in the structural elements of concrete. This research investigated the effect of groundnut leaf/stem ash (GLSA) on the compressive strength of concrete at 0%, 5 %, 10 % and 15 % replacements of cement. The effect of the water-cement ratio on properties such as the compressive strength, slump, flow and workability properties of groundnut leaf/stem ash (GLSA) mixes with OPC were evaluated to determine whether they are acceptable for use in concrete structural elements. A normal concrete mix with cement at 100 % (i.e., GLSA at 0%) with concrete grade C25 that can attain an average strength of 25 N/mm2 at 28 days was used as a control at design water-cement ratios of 0.65 and grading of (0.5-32) mm from fine to coarse aggregates was tested for: (1) compressive strength, and the (2) slump and flow Test. The results and observations showed that the concrete mixes from GLSA at 5 - 15 % ratios exhibit: pozzolanic properties and GLSA could be used as a partial replacement for cement at these percentage mix ratios compared with the control concrete; an increase in the water-cement ratio showed a significant decrease in the compressive strength and an increase in workability. Therefore, it is important that all concrete mixes exude an acceptably designed water-cement ratio for compressive strength characteristics for use in structures, water-cement ratio is a significant factor.

Effect of bioglass 45S5 addition on properties, microstructure and cellular response of tetracalcium phosphate/monetite cements

Energy Technology Data Exchange (ETDEWEB)

Stulajterova, R., E-mail: rstulajterova@saske.sk; Medvecky, L.; Giretova, M.; Sopcak, T.; Kovalcikova, A.

2017-04-15

Tetracalcium phosphate/nanomonetite (TTCPMH) cement composites with 7.5 and 15 wt% addition of melt-derived 45S5 bioactive glass were prepared by mechanical homogenization of powder components and 2% NaH{sub 2}PO{sub 4} solution was used as a hardening liquid. The properties of composites with the acidic (Ca/P ratio equal 1.5) or basic (Ca/P ratio equal 1.67) TTCPMH component were compared. Addition of glass component caused rapid rise in pH of composites up to 10. In microstructure of basic cement composite, the large bioglass particles weakly bounded to surrounding cement matrix were found contrary to a more compact microstructure of acidic cement composites with the high number of spherical silica particles. Both the significant refinement of hydroxyapatite particles and the change to needle-like morphology with rise in the content of bioglass were identified in hydroxyapatite coatings created during soaking of composites in phosphate buffered saline. In acidic cement mixtures, the increase of compressive strength with an amount of bioglass was found whereas the opposite tendency was revealed in the case of basic cement mixtures. The higher concentrations of ions were verified in solutions after immersion of acidic cement composites. The severe cytotoxicity of extracts and composite cement substrates containing 15 wt% of bioglass demonstrated adverse effects of both the ionic concentrations and unappropriate surface texture on proliferation of mesenchymal stem cells. The enhanced ALP activities of cells cultured on composite cements confirmed the positive effect of bioactive glass addition on differentiation of mesenchymal stem cells. - Highlights: • Novel B45S5 bioglass/tetracalcium phosphate/nanomonetite cement composites • Cement basicity negatively affected their microstructure. • Acid composite cements had higher compressive strengths than basic composites. • Fast differentiation of MSC to osteoblast line on composite with 7.5 wt% of bioglass �

Stem cell technology using bioceramics: hard tissue regeneration towards clinical application

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Hiroe Ohnishi, Yasuaki Oda and Hajime Ohgushi

2010-01-01

Full Text Available Mesenchymal stem cells (MSCs are adult stem cells which show differentiation capabilities toward various cell lineages. We have already used MSCs for treatments of osteoarthritis, bone necrosis and bone tumor. For this purpose, culture expanded MSCs were combined with various ceramics and then implanted. Because of rejection response to allogeneic MSC implantation, we have utilized patients' own MSCs for the treatment. Bone marrow is a good cell source of MSCs, although the MSCs also exist in adipose tissue. When comparing osteogenic differentiation of these MSCs, bone marrow MSCs show more extensive bone forming capability than adipose MSCs. Thus, the bone marrow MSCs are useful for bone tissue regeneration. However, the MSCs show limited proliferation and differentiation capabilities that hindered clinical applications in some cases. Recent advances reveal that transduction of plural transcription factors into human adult cells results in generation of new type of stem cells called induced pluripotent stem cells (iPS cells. A drawback of the iPS cells for clinical applications is tumor formation after their in vivo implantation; therefore it is difficult to use iPS cells for the treatment. To circumvent the problem, we transduced a single factor of either SOX2 or NANOG into the MSCs and found high proliferation as well as osteogenic differentiation capabilities of the MSCs. The stem cells could be combined with bioceramics for clinical applications. Here, we summarize our recent technologies using adult stem cells in viewpoints of bone tissue regeneration.

Evaluation of dentin hypersensitivity treatment with glass ionomer cements: A randomized clinical trial

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Marina de Matos MADRUGA

Full Text Available Abstract A randomized, double-blind, split-mouth clinical trial was performed compared the desensitizing efficacy of the resin-modified glass ionomer cement (GIC ClinproTM XT (3M ESPE, Minnesota, USA and the conventional GIC Vidrion R (SS White, Gloucester, UK in a 6-month follow-up. Subjects were required to have at least two teeth with dentin hypersensitivity. Teeth were divided at random into 2 groups, one group received Clinpro XT and the other conventional GIC Vidrion R. Treatments were assessed by tactile and air blast tests using Visual Analogue Scale (VAS at baseline, after 20 minutes, and at 7, 15, 21, 30, 90 and 180 days post-treatment. Twenty subjects (152 teeth were included. Both tests (tactile and air blast showed a significant reduction of dentin hypersensitivity immediately after the application of Vidrion R and Clinpro XT (20 min. VAS scores obtained along the 6-month follow-up were statistically lower when compared to initial rates (p 0.05. Both cements provided satisfactory results in long-term dental sensitivity reduction.

Gold nanoparticles in injectable calcium phosphate cement enhance osteogenic differentiation of human dental pulp stem cells.

Science.gov (United States)

Xia, Yang; Chen, Huimin; Zhang, Feimin; Bao, Chongyun; Weir, Michael D; Reynolds, Mark A; Ma, Junqing; Gu, Ning; Xu, Hockin H K

2018-01-01

In this study, a novel calcium phosphate cement containing gold nanoparticles (GNP-CPC) was developed. Its osteogenic induction ability on human dental pulp stem cells (hDPSCs) was investigated for the first time. The incorporation of GNPs improved hDPSCs behavior on CPC, including better cell adhesion (about 2-fold increase in cell spreading) and proliferation, and enhanced osteogenic differentiation (about 2-3-fold increase at 14 days). GNPs endow CPC with micro-nano-structure, thus improving surface properties for cell adhesion and subsequent behaviors. In addition, GNPs released from GNP-CPC were internalized by hDPSCs, as verified by transmission electron microscopy (TEM), thus enhancing cell functions. The culture media containing GNPs enhanced the cellular activities of hDPSCs. This result was consistent with and supported the osteogenic induction results of GNP-CPC. In conclusion, GNP-CPC significantly enhanced the osteogenic functions of hDPSCs. GNPs are promising to modify CPC with nanotopography and work as bioactive additives thus enhance bone regeneration. Copyright © 2017 Elsevier Inc. All rights reserved.

Strength Characteristics of Groundnut Leaf/Stem Ash (GLSA Concrete

Directory of Open Access Journals (Sweden)

Oseni O. W.

2016-09-01

Full Text Available The compressive strength properties of concrete are substantial factors in the design and construction of concrete structures. Compressive strength directly affects the degree to which the concrete can be able to carry a load over time. These changes are complemented by deflections, cracks etc., in the structural elements of concrete. This research investigated the effect of groundnut leaf/stem ash (GLSA on the compressive strength of concrete at 0%, 5 %, 10 % and 15 % replacements of cement. The effect of the water-cement ratio on properties such as the compressive strength, slump, flow and workability properties of groundnut leaf/stem ash (GLSA mixes with OPC were evaluated to determine whether they are acceptable for use in concrete structural elements. A normal concrete mix with cement at 100 % (i.e., GLSA at 0% with concrete grade C25 that can attain an average strength of 25 N/mm2 at 28 days was used as a control at design water-cement ratios of 0.65 and grading of (0.5-32 mm from fine to coarse aggregates was tested for: (1 compressive strength, and the (2 slump and flow Test. The results and observations showed that the concrete mixes from GLSA at 5 – 15 % ratios exhibit: pozzolanic properties and GLSA could be used as a partial replacement for cement at these percentage mix ratios compared with the control concrete; an increase in the water-cement ratio showed a significant decrease in the compressive strength and an increase in workability. Therefore, it is important that all concrete mixes exude an acceptably designed water-cement ratio for compressive strength characteristics for use in structures, water-cement ratio is a significant factor.

Understanding mineral trioxide aggregate/Portland-cement: a review of literature and background factors.

Science.gov (United States)

Steffen, R; van Waes, H

2009-06-01

This was to carry out a review of the literature concerning mineral trioxide aggregate (MTA) and Portland cement with regards to clinical, biological and mechanical findings and a possible substitution of MTA through Portland cement for endodontic use. Electronic literature search of scientific papers from January 1993 to January 2009 was carried out on the MEDLINE and Scopus databases using specific key words. In total, 57 papers were identified that dealt with MTA and Portland cement in a relevant way. The review of 50 papers conforming to the applied criteria showed that MTA and Portland cements have the same clinical, biological and mechanical properties. In animal experiments and technical characterisations both materials seemed to have very similar properties. The only difference is bismuth oxide in MTA added for better radio opacity. It seems likely that MTA materials are based on industrial Portland cements mixed with bismuth oxide. More studies, especially some long-term studies comparing MTA and Portland cement, are necessary. The existing literature gives a solid base for clinical studies with Portland cement in order to replace MTA as an endodontic material. Portland cement could be a substitute for most endodontic materials used in primary teeth.

Processes and Equipment for the Cementation of Radioactive Waste

International Nuclear Information System (INIS)

Schaefer, S.; Studenski, J.

2012-01-01

In this article a short selection of different cement mixer types provided by NUKEM Technologies is given. The variety stems on one hand from historical development, but more especially from specific customer demands to meet their local and technical requirements. The Slant Batch Mixer is successfully installed in several Waste Treatment Centers (WTC). NUKEM Technologies set up these mixers with necessary auxiliary systems to facilitate all the cementation tasks of a WTC. By the slant design of the mixer a homogeneous intermixing and a rapid and comprehensive emptying is achieved. The High Shear Mixer is a batch mixer producing a thixotropic, fast flowing colloidal cement slurry. NUKEM Technologies uses this cement slurry to bubble-free/ empty space-free grouting of pre-packed solid waste items in container. The High Throughput Continuous Mixer is a continuously operating screw mixer that provides a high throughput. One or more dry components are continuously fed to the mixer where liquid waste or water is added. The High Performance In-Drum Mixer is a combination of planetary mixer with double helical mixer. NUKEM Technologies recently has developed a new High Capacity Mixer (HCM) based on a well proven conventional concrete mixer. The HCM is the successor of the slant mixer and will expend NUKEM Technologies' portfolio of cementation units. (A.C.)

Stem cells: progressions and applications in clinical medicine

Directory of Open Access Journals (Sweden)

Ali Hosseini Bereshneh

2016-05-01

of them in transferring gene into different cells. Today, this method have had considerable progress in the treatment of many disease. In this review study, some aspect of stem cells like types and characteristic, origin, derivation techniques, storage conditions and differentiation to target tissues, current clinical usage and their therapeutic capabilities will be discussed.

Clinical and radiographic evaluation of Portland cement added to radiopacifying agents in primary molar pulpotomies.

Science.gov (United States)

Lourenço Neto, N; Marques, N C T; Fernandes, A P; Hungaro Duarte, M A; Abdo, R C C; Machado, M A A M; Oliveira, T M

2015-10-01

This was to evaluate the clinical and radiographic outcomes of Portland cement (PC) added to radiopacifying agents in primary molar pulpotomies. Thirty primary mandibular molars of children aged between 5 and 9 years were randomly assigned to the following groups: PC; PC with iodoform (PC + CHI(3)); PC with zirconium oxide (PC + ZrO(2)) and treated by pulpotomy technique. Clinical and radiographic follow-up assessments were performed at 6, 12 and 24 months. Statistical analysis was performed by Fisher's exact test (P < 0.05). The clinical and radiographic evaluations showed 100 % success rates, and the results showed no statistically significant difference between groups. According to this study, PC added to radiopacifying agents exhibited satisfactory clinical and radiographic results in primary molar pulpotomies.

Clinical perspectives of cancer stem cell research in radiation oncology

International Nuclear Information System (INIS)

Bütof, Rebecca; Baumann, Michael; Dubrovska, Anna

2013-01-01

Radiotherapy has a proven potential to eradicate cancer stem cells which is reflected by its curative potential in many cancer types. Considerable progress has been made in identification and biological characterisation of cancer stem cells during the past years. Recent biological findings indicate significant inter- and intratumoural and functional heterogeneity of cancer stem cells and lead to more complex models which have potential implications for radiobiology and radiotherapy. Clinical evidence is emerging that biomarkers of cancer stem cells may be prognostic for the outcome of radiotherapy in some tumour entities. Perspectives of cancer stem cell based research for radiotherapy reviewed here include their radioresistance compared to the mass of non-cancer stem cells which form the bulk of all tumour cells, implications for image- and non-image based predictive bio-assays of the outcome of radiotherapy and a combination of novel systemic treatments with radiotherapy

Ambivalent journeys of hope: embryonic stem cell therapy in a clinic in India.

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Prasad, Amit

2015-03-01

Stem cell therapy in non-Western countries such as India has received a lot of attention. Apart from media reports, there are a number of social science analyses of stem cell policy, therapy, and research, their ethical implications, and impact of advertising on patients. Nevertheless, in the media reports as well as in academic studies, experiences of patients, who undertake overseas journeys for stem cell therapy, have largely been either ignored or presented reductively, often as a "false hope." In this article, I analyze the experiences of patients and their "journeys of hope" to NuTech Mediworld, an embryonic stem cell therapy clinic in New Delhi, India. My analysis, which draws on my observations in the clinic and patients' experiences, instead of seeking to adjudicate whether embryonic stem cell therapy in clinics such as NuTech is right or wrong, true or false, focuses on how patients navigate and contest these concerns. I utilize Gilles Deleuze and Felix Guattari's "concepts," lines of flight and deterritorialization, to highlight how embryonic stem cell therapy's "political economy of hope" embodies deterritorialization of several "regimes of truth" and how these deterritorializations impact patients' experiences. © The Author(s) 2014.

A randomized clinical trial on the use of medical Portland cement, MTA and calcium hydroxide in indirect pulp treatment.

Science.gov (United States)

Petrou, Marina Agathi; Alhamoui, Fadi Alhaddad; Welk, Alexander; Altarabulsi, Mohammed Basel; Alkilzy, Mohammed; H Splieth, Christian

2014-01-01

Studies on indirect pulp treatment (IPT) show varying success rates of 73 to 97 %. The necessity of re-opening the cavity and the question of the optimal capping material is still under debate. The aim of this prospective in vivo study was to compare the clinical and microbiological outcomes of mineral trioxide aggregate (MTA), medical Portland cement, and calcium hydroxide on the dentin-pulp complex of permanent and primary teeth treated with two-step IPT. In 86 regular patients (51 % men; 49 % women; age 17.2 years ±13.8), one deep carious lesion each was treated with incomplete caries removal, randomly selected capping with either calcium hydroxide (n = 31), medical Portland cement (29) or white MTA (26), and re-entry (6.3 months ±1.0). Clinical (color, humidity, and consistency of dentin) and microbiological (Lactobacilli/Mutans Strep. counts) parameters were recorded at the first and second treatment. The IPT had a high success rate of 90.3 % regardless of the material used (p = 0.72). The arrested lesions showed consistently darker, dry, and therefore, sclerotic dentine (p Portland cement. The findings of this study could promote the improvement of the IPT as a one-step treatment of deep carious lesions when the remaining demineralized dentin would be sealed with durable restorations.

Ethics of international clinical research collaboration - the experience of AlloStem.

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Chaplin, C

2006-02-01

This paper examines the ethics of international clinical collaboration in stem cell research by focusing on the AlloStem project. AlloStem is an international research programme, financed by the European Union under the Sixth Framework Programme, with the aim of advancing the use of stem cells in treating leukaemia and other haematological diseases. Several areas of ethical importance are explored. Research justification and the need to consider both deontological and teleological aspects are examined. Ethical sensitivity in research and the requirement to respond to areas of ethical concern identified by the European Commission, such as the involvement of human beings, the use of human tissue, and the use of animals are also explored. Ethical issues around project structure and management, such as ethical standardization in international research, and achieving set targets are discussed. The ethical importance of dissemination of findings and teaching in clinical research is also considered. Finally, the distribution of benefits is addressed and the importance of distributive justice is emphasized.

Static coefficient of friction between stainless steel and PMMA used in cemented hip and knee implants.

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Nuño, N; Groppetti, R; Senin, N

2006-11-01

Design of cemented hip and knee implants, oriented to improve the longevity of artificial joints, is largely based on numerical models. The static coefficient of friction between the implant and the bone cement is necessary to characterize the interface conditions in these models and must be accurately provided. The measurement of this coefficient using a repeatable and reproducible methodology for materials used in total hip arthroplasty is missing from the literature. A micro-topographic surface analysis characterized the surfaces of the specimens used in the experiments. The coefficient of friction between stainless steel and bone cement in dry and wet conditions using bovine serum was determined using a prototype computerized sliding friction tester. The effects of surface roughness (polished versus matt) and of contact pressure on the coefficient of friction have also been investigated. The serum influences little the coefficient of friction for the matt steel surface, where the mechanical interactions due to higher roughness are still the most relevant factor. However, for polished steel surfaces, the restraining effect of proteins plays a very relevant role in increasing the coefficient of friction. When the coefficient of friction is used in finite element analysis, it is used for the debonded stem-cement situation. It can thus be assumed that serum will propagate between the stem and the cement mantle. The authors believe that the use of a static coefficient of friction of 0.3-0.4, measured in the present study, is appropriate in finite element models.

A Comparative Study of the Retentive Strengths of Commercial and Indigenously Developed Luting Cements using Both Lathe-cut and Clinically Simulated Specimens.

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Mathew, Joe; Kurian, Byju P; Philip, Biju; Mohammed, Sunil; Menon, Preetha; Raj, Rajan S

2016-08-01

Superior adhesive strength in luting agents is of paramount significance in fixed partial denture success. In this in vitro study five cements were tested for retentive qualities, using both lathe-cut and hand-prepared specimens. A total of 104 freshly extracted tooth specimens were prepared. Seventy of them were lathe-cut and 30 specimens were hand-prepared to simulate clinical conditions. Five different cements were tested, which included a compomer, a composite, a zinc phosphate, and 2 glass-ionomer luting cements. Of the 5, 2 trial cements were indigenously developed by Sree Chitra Tirunal Institute for Medical Sciences and Technology (SCTIMST), Trivandrum, India - a glass-ionomer cement (Chitra GIC) and a chemical-cure composite (Chitra CCC). All cements were compared within each group and between groups (lathe-prepared and hand-prepared). GC Fuji 1 (GC America) exhibited superior retentive strengths in both lathe-cut and hand-prepared specimens, whereas the compomer cement displayed the lowest values when tested. In lathe-cut specimens, statistical analysis showed no significant difference between GC Fuji 1 and indigenously developed Chitra CCC. Both Chitra CCC and GC Fuji 1 have comparable strengths in lathe-cut samples, making Chitra CCC a potential luting agent. Statistical analysis reveals that all cements, except GC Fuji 1, exhibited a significant decrease in strength due to the change in design uniformity. The chemical bonding of GC Fuji 1 proves to be quite strong irrespective of shape and precision of the tooth crown. The indigenously developed Chitra GIC and Chitra CCC showed promising results to be used as a potential luting agent.

Global regulatory developments for clinical stem cell research: diversification and challenges to collaborations.

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Rosemann, Achim; Bortz, Gabriela; Vasen, Federico; Sleeboom-Faulkner, Margaret

2016-10-01

In this article, we explore regulatory developments in stem cell medicine in seven jurisdictions: Japan, China, India, Argentina, Brazil, the USA and the EU. We will show that the research methods, ethical standards and approval procedures for the market use of clinical stem cell interventions are undergoing an important process of global diversification. We will discuss the implications of this process for international harmonization and the conduct of multicountry clinical research collaborations. It will become clear that the increasing heterogeneity of research standards and regulations in the stem cell field presents a significant challenge to international clinical trial partnerships, especially with countries that diverge from the regulatory models that have been developed in the USA and the EU.

Contact dermatitis in cement workers in Isfahan

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Iraji Fariba

2006-01-01

Full Text Available BACKGROUND: Due to recent industrialization and inadequately protected workers or in other words poor supervision on constructive workers habits in our large city of Isfahan cement contact dermatitis is relatively high especially among cement factory workers and constructive personnel. PURPOSES: To investigate the prevalence rate of cement contact dermatitis in cement factory workers in Isfahan. METHODS: A case-control clinical study was carried out by randomly selecing 150 factory workders and 150 official clerks in a cement factory in Isfahan in 2001. After a complete physical examination, data was recorded in observational checklists. FINDINGS: The percentages of contact dermatitis prevalences in the first and the second groups were 22% and 5.3% respectively. About 60% of cement workers with contact dermatitis were between 30-40 years of age. There was a direct relationship with age in both groups of the workers. In the high-exposure group, the hand eczema along was 70% but in the other group the percentage of involvement was the same in exposed and unexposed anatomical areas. CONCLUSIONS: There was a direct relationship between occurrence and the severity of involvement and duration of contact in the first group. Cent percent of cement workers had contact dermatitis after 10 or less years, but the percentage among the other group was 35%. LIMITATION: Irritant contact dermatitis to cement has not been detected.

Performance of Cement Containing Laterite as Supplementary Cementing Material

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Abbas Bukhari, Z. S.

2013-03-01

Full Text Available The utilization of different industrial waste, by-products or other materials such as ground granulated blast furnace slag, silica fume, fly ash, limestone, and kiln dust, etc. as supplemen- tary cementing materials has received considerable attention in recent years. A study has been conducted to look into the performance of laterite as Supplementary Cementing Materials (SCM. The study focuses on compressive strength performance of blended cement containing different percentage of laterite. The cement is replaced accordingly with percentage of 2 %, 5 %, 7 % and 10 % by weight. In addition, the effect of use of three chemically different laterites have been studied on physical performance of cement as in setting time, Le-Chatlier expansion, loss on ignition, insoluble residue, free lime and specifically compressive strength of cement cubes tested at the age of 3, 7, and 28 days. The results show that the strength of cement blended with laterite as SCM is enhanced. Key words: Portland cement, supplementary cementing materials (SCM, laterite, compressive strength KUI – 6/2013 Received January 4, 2012 Accepted February 11, 2013

Physicochemical properties of newly developed bioactive glass cement and its effects on various cells.

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Washio, Ayako; Nakagawa, Aika; Nishihara, Tatsuji; Maeda, Hidefumi; Kitamura, Chiaki

2015-02-01

Biomaterials used in dental treatments are expected to have favorable properties such as biocompatibility and an ability to induce tissue formation in dental pulp and periapical tissue, as well as sealing to block external stimuli. Bioactive glasses have been applied in bone engineering, but rarely applied in the field of dentistry. In the present study, bioactive glass cement for dental treatment was developed, and then its physicochemical properties and effects on cell responses were analyzed. To clarify the physicochemical attributes of the cement, field emission scanning electron microscopy, X-ray diffraction, and pH measurement were carried out. Cell attachment, morphology, and viability to the cement were also examined to clarify the effects of the cement on odontoblast-like cells (KN-3 cells), osteoblastic cells (MC3T3-E1 cells), human periodontal ligament stem/progenitor cells and neuro-differentiative cells (PC-12 cells). Hydroxyapatite-like precipitation was formed on the surface of the hardened cement and the pH level changed from pH10 to pH9, then stabilized in simulate body fluid. The cement had no cytotxic effects on these cells, and particulary induced process elongation of PC-12 cells. Our results suggest that the newly developed bioactive glass cement have capability of the application in dental procedures as bioactive cement. © 2014 Wiley Periodicals, Inc.

Human embryonic stem cell-encapsulation in alginate microbeads in macroporous calcium phosphate cement for bone tissue engineering

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Tang, Minghui; Chen, Wenchuan; Weir, Michael D.; Thein-Han, Wahwah; Xu, Hockin H. K.

2012-01-01

Human embryonic stem cells (hESCs) are exciting for regenerative medicine applications because of their strong proliferative ability and multilineage differentiation capability. To date there has been no report on hESC seeding with calcium phosphate cement (CPC). The objective of this study was to investigate hESC-derived mesenchymal stem cell (hESCd-MSC) encapsulation in hydrogel microbeads in macroporous CPC for bone tissue engineering. hESCs were cultured to form embryoid bodies (EBs), and the MSCs were then migrated out of the EBs. hESCd-MSCs had surface markers characteristic of MSCs, with positive alkaline phosphatase (ALP) staining when cultured in osteogenic medium. hESCd-MSCs were encapsulated in alginate at a density of 1 million cells/mL, with an average microbead size of 207 µm. CPC contained mannitol porogen to create a porosity of 64% and macropores with size of 218 µm, with 20% absorbable fibers for additional porosity when the fibers degrade. hESCd-MSCs encapsulated in microbeads in CPC had good viability from 1 to 21 d. ALP gene expression at 21 d was 25-fold that at 1 d. Osteocalcin (OC) at 21 d was two orders of magnitude of that at 1 d. ALP activity in colorimetric p-nitrophenyl phosphate assay at 21 d was 5-fold that at 1 d. Mineral synthesis by the encapsulated hESCd-MSCs at 21 d was 7-fold that at 1 d. Potential benefits of the CPC-stem cell paste include injectability, intimate adaptation to complex-shaped bone defects, ease in contouring to achieve esthetics in maxillofacial repairs, and in situ setting ability. In conclusion, hESCd-MSCs were encapsulated in alginate microbeads in macroporous CPC showing good cell viability, osteogenic differentiation and mineral synthesis for the first time. The hESCd-MSC-encapsulating macroporous CPC construct is promising for bone regeneration in a wide range of orthopedic and maxillofacial applications. PMID:22633970

A Simplified Method of Opacifying and Mixing Acrylic Cement for Percutaneous Vertebroplasty: A Clinical and In Vitro Study

International Nuclear Information System (INIS)

Teng Gaojun; He Shicheng; Deng Gang; Guo Jinhe; Fang Wen; Zhu Guangyu

2005-01-01

The objective of this study was to simplify the opacifying mixing process of the bone cement and contrast used for percutaneous vertebroplasty (PVP). We performed a biomechanical study of polymethyl methacrylate (PMMA) (Corinplast TM 3) using three different mixtures of PMMA, monomer, and contrast: group I, 2:1; group II, 3:2; group III, 3:2:1 ratio of powder/monomer/iodinated contrast (Omnipaque). In vitro biomechanical testing of ultimate compressive strength was carried out in all samples. Following the conclusion of a proper bone cement mixture regimen drawn from the in vitro study, PVP was performed in 125 patients: 58 with cancer, 12 with hemangioma, and 54 with osteoporotic fracture. The ultimate compressive strength in group III was decreased by 38% compared to groups II and I. Proper fluoroscopic visualization was achieved in all PVP procedures using this mixture. There were no major complications associated with injection of the cement mixture. Complete (CR) and partial response (PR) was obtained in 64% and 32.8%, respectively. No further vertebral collapse occurred during follow-up. The regimen using iodinated contrast for cement visualization during PVP provides a simple and convenient new method for mixing. Although the biomechanical strength is altered by the contrast medium added, it seems insignificant in clinical practice based on the authors' limited experience

Chemical constitution, physical properties, and biocompatibility of experimentally manufactured Portland cement.

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Hwang, Yun-Chan; Kim, Do-Hee; Hwang, In-Nam; Song, Sun-Ju; Park, Yeong-Joon; Koh, Jeong-Tae; Son, Ho-Hyun; Oh, Won-Mann

2011-01-01

An experimental Portland cement was manufactured with pure raw materials under controlled laboratory conditions. The aim of this study was to compare the chemical constitution, physical properties, and biocompatibility of experimentally manufactured Portland cement with those of mineral trioxide aggregate (MTA) and Portland cement. The composition of the cements was determined by scanning electron microscopy (SEM) and energy-dispersive x-ray analysis (EDAX). The setting time and compressive strength were tested. The biocompatibility was evaluated by using SEM and XTT assay. SEM and EDAX revealed the experimental Portland cement to have a similar composition to Portland cement. The setting time of the experimental Portland cement was significantly shorter than that of MTA and Portland cement. The compressive strength of the experimental Portland cement was lower than that of MTA and Portland cement. The experimental Portland cement showed a similar biocompatibility to MTA. The experimental Portland cement might be considered as a possible substitute for MTA in clinical usage after further testing. Copyright © 2011 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

In vitro evaluation of microleakage of various types of dental cements

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Medić Vesna

2010-01-01

Full Text Available Introduction. Microleakage is defined as the clinically undetectable seepage of oral fluids containing bacteria and debris between cement layer and tooth restoration. Objective. This in vitro study investigated the effect of different dental cements (zinc-phosphate, polycarboxylate, glass-ionomer and resin cement on microleakage in different ceramic crown systems (metal ceramic crown, metal ceramic crown with a porcelain margin, Empress 2 and In Ceram all-ceramic crowns fixed on extracted human teeth. Methods. One hundred and sixty intact human premolars were randomized to four groups of forty teeth each, according to the different ceramic crown systems. They were prepared in a standardized manner for metal-ceramic and all-ceramic crowns. Crowns were made following a standard laboratory technique, and each group of crowns were divided into four groups according to the different cement agents and cemented on their respective abutments. The specimens were subjected to thermocycling, placed in methylene blue solutions, embedded in resin blocks and vertically cut in the bucco-oral and meso-distal direction. The microleakage in the area of tooth-cement interface was defined as linear penetration of methylene blue and was determined with a microscope to assign microleakage scores using a five-point scale. Results. A significant association was found between a cement type and degree of microleakage (p=0.001. No statistically significant differences were found among the different ceramic crown systems luted with the same dental cement. The smallest degree of microleakage was observed in specimens luted with resin cement (X=1.73, followed by glass-ionomer cement (X=2.45 and polycarboxylate cement (X=3.20. The greatest degree of microleakage was detected in the crowns fixed with zincphosphate cement (X=3.33. Conclusion. The investigated dental cements revealed different sealing abilities. The use of resin cement resulted in the percentage of 0

Particulate metallic debris in cemented total hip arthroplasty.

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Salvati, E A; Betts, F; Doty, S B

1993-08-01

Several studies conducted by the authors in the last six years demonstrate that the generation of metallic debris is more severe with titanium alloy than with cobalt-chrome alloy femoral components in cemented total hip arthroplasty (THA). The debris is generated from the articulating surface, particularly if entrapped acrylic debris produces three-body wear, and from the stem surface when the component loosens and abrades against fragmented cement. In selected cases in which the titanium metallic debris is copious, premature failure and severe progressive bone loss occurs. Electron microscopy demonstrates that the particles of metallic debris can be extremely small (a few hundredths of 1 micron). They are phagocytized by the macrophages and transported to the phagolysosomes. In this highly corrosive environment, the very high surface area of the particles may release toxic concentrations of the constituents of the alloy intracellularly, probably leading to progressive cell degeneration and death, with subsequent release of intracellular enzymes and ingested metallic debris. This cycle most likely repeats itself, leading to tissue necrosis. The results presented do not support the use of titanium alloy femoral components for cemented THA, particularly for the articulating surface.

Cermet cements.

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McLean, J W

1990-01-01

Cermet ionomer cements are sintered metal/glass powders, which can be made to react with poly(acids). These new cements are significantly more resistant to abrasion than regular glass ionomer cements and are widely accepted as core build-up materials and lining cements. They can strengthen teeth and provide the clinician with an opportunity to treat early dental caries.

The combination of ultrasound with antibiotics released from bone cement decreases the viability of planktonic and biofilm bacteria: an in vitro study with clinical strains.

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Ensing, Geert T; Neut, Daniëlle; van Horn, Jim R; van der Mei, Henny C; Busscher, Henk J

2006-12-01

Antibiotic-loaded bone cements are used for the permanent fixation of joint prostheses. Antibiotic-loaded cements significantly decrease the incidence of infection. The objective of this study was to investigate whether the viability of bacteria derived from patients with a prosthesis-related infection could be further decreased when antibiotic release from bone cements was combined with application of pulsed ultrasound. Escherichia coli ATCC 10798, Staphylococcus aureus 7323, coagulase-negative staphylococci (CoNS 7368 and CoNS 7391) and Pseudomonas aeruginosa 5148 were grown planktonically in suspension and as a biofilm on three different bone cements: Palacos R without gentamicin as control, gentamicin-loaded Palacos R-G and gentamicin/clindamycin-loaded Copal. The viability of planktonic and biofilm bacteria was measured in the absence and presence of pulsed ultrasound for 40 h. Ultrasound itself did not affect bacterial viability. However, application of pulsed ultrasound in combination with antibiotic release by antibiotic-loaded bone cements yielded a reduction of both planktonic and biofilm bacterial viability compared with antibiotic release without application of ultrasound. This study shows that antibiotic release in combination with ultrasound increases the antimicrobial efficacy further than antibiotic release alone against a variety of clinical isolates. Application of ultrasound in combination with antibiotic release in clinical practice could therefore lead to better prevention or treatment of prosthesis-related infections.

Simplified cementation of lithium disilicate crowns: Retention with various adhesive resin cement combinations.

Science.gov (United States)

Johnson, Glen H; Lepe, Xavier; Patterson, Amanda; Schäfer, Oliver

2017-09-27

A composite resin cement and matching self-etch adhesive was developed to simplify the dependable retention of lithium disilicate crowns. The efficacy of this new system is unknown. The purpose of this in vitro study was to determine whether lithium disilicate crowns cemented with a new composite resin and adhesive system and 2 other popular systems provide clinically acceptable crown retention after long-term aging with monthly thermocycling. Extracted human molars were prepared with a flat occlusal surface, 20-degree convergence, and 4 mm axial length. The axio-occlusal line angle was slightly rounded. The preparation surface area was determined by optical scanning and the analysis of the standard tessellation language (STL) files. The specimens were distributed into 3 cement groups (n=12) to obtain equal mean surface areas. Lithium disilicate crowns (IPS e.max Press) were fabricated for each preparation, etched with 9.5% hydrofluoric acid for 15 seconds, and cleaned. Cement systems were RelyX Ultimate with Scotch Bond Universal (3M Dental Products); Monobond S, Multilink Automix with Multilink Primer A and B (Ivoclar Vivadent AG); and NX3 Nexus with OptiBond XTR (Kerr Corp). Each adhesive provided self-etching of the dentin. Before cementation, the prepared specimens were stored in 35°C water. A force of 196 N was used to cement the crowns, and the specimens were polymerized in a 35°C oven at 100% humidity. After 24 hours of storage at 100% humidity, the cemented crowns were thermocycled (5°C to 55°C) for 5000 cycles each month for 6 months. The crowns were removed axially at 0.5 mm/min. The removal force was recorded and the dislodgement stress calculated using the preparation surface area. The type of cement failure was recorded, and the data were analyzed by 1-way ANOVA and the chi-square test (α=.05) after the equality of variances had been assessed with the Levene test. The Levene test was nonsignificant (P=.936). The ANOVA revealed the mean removal

Pre-Clinical Cell-Based Therapy for Limbal Stem Cell Deficiency.

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Sehic, Amer; Utheim, Øygunn Aass; Ommundsen, Kristoffer; Utheim, Tor Paaske

2015-08-28

The cornea is essential for normal vision by maintaining transparency for light transmission. Limbal stem cells, which reside in the corneal periphery, contribute to the homeostasis of the corneal epithelium. Any damage or disease affecting the function of these cells may result in limbal stem cell deficiency (LSCD). The condition may result in both severe pain and blindness. Transplantation of ex vivo cultured cells onto the cornea is most often an effective therapeutic strategy for LSCD. The use of ex vivo cultured limbal epithelial cells (LEC), oral mucosal epithelial cells, and conjunctival epithelial cells to treat LSCD has been explored in humans. The present review focuses on the current state of knowledge of the many other cell-based therapies of LSCD that have so far exclusively been explored in animal models as there is currently no consensus on the best cell type for treating LSCD. Major findings of all these studies with special emphasis on substrates for culture and transplantation are systematically presented and discussed. Among the many potential cell types that still have not been used clinically, we conclude that two easily accessible autologous sources, epidermal stem cells and hair follicle-derived stem cells, are particularly strong candidates for future clinical trials.

Durability of cermet ionomer cement conditioned in different media.

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el-Din, I M

1992-01-01

The glass ionomer cement has exhibited significant adhesion to hard tooth structures, and good cariostatic properties. The sintering of the silver alloy powder and glass ionomer cement "cermet cement" has provided additional improvement in the physical properties of the restorative material. These were flexural resistance, wear resistance, increased radio-opacity, hardness and porosity. The improvement in the physical properties of the cermet glass cements has provided an extension in their clinical use as core build up, lining for inlays, amalgam and composite restoratives, fissure filling, restoration of primary teeth, class II tunnel preparation, treatment of root caries and repair of defective metal margins in crown and inlays.

Radiopacity of portland cement associated with different radiopacifying agents.

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Húngaro Duarte, Marco Antonio; de Oliveira El Kadre, Guâniara D'arc; Vivan, Rodrigo Ricci; Guerreiro Tanomaru, Juliane Maria; Tanomaru Filho, Mário; de Moraes, Ivaldo Gomes

2009-05-01

This study evaluated the radiopacity of Portland cement associated with the following radiopacifying agents: bismuth oxide, zinc oxide, lead oxide, bismuth subnitrate, bismuth carbonate, barium sulfate, iodoform, calcium tungstate, and zirconium oxide. A ratio of 20% radiopacifier and 80% white Portland cement by weight was used for analysis. Pure Portland cement and dentin served as controls. Cement/radiopacifier and dentin disc-shaped specimens were fabricated, and radiopacity testing was performed according to the ISO 6876/2001 standard for dental root sealing materials. Using Insight occlusal films, the specimens were radiographed near to a graduated aluminum stepwedge varying from 2 to 16 mm in thickness. The radiographs were digitized and radiopacity compared with the aluminum stepwedge using Digora software (Orion Corporation Soredex, Helsinki, Finland). The radiographic density data were converted into mmAl and analyzed statistically by analysis of variance and Tukey-Kramer test (alpha = 0.05). The radiopacity of pure Portland cement was significantly lower (p cement/radiopacifier mixtures were significantly more radiopaque than dentin and Portland cement alone (p cement/bismuth oxide and Portland cement/lead oxide presented the highest radiopacity values and differed significantly from the other materials (p cement/zinc oxide presented the lowest radiopacity values of all mixtures (p cement as radiopacifying agents. However, the possible interference of the radiopacifiers with the setting chemistry, biocompatibility, and physical properties of the Portland cement should be further investigated before any clinical recommendation can be done.

Challenges of stem cell-based pulp and dentin regeneration: a clinical perspective.

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Huang, George T-J; Al-Habib, Mey; Gauthier, Philippe

2013-03-01

There are two types of approaches to regenerate tissues: cell-based and cell-free. The former approach is to introduce exogenous cells into the host to regenerate tissues, and the latter is to use materials other than cells in an attempt to regenerate tissues. There has been a significant advancement in stem cell-based pulp and dentin regeneration research in the past few years. Studies in small and large animals have demonstrated that pulp/dentin-like tissues can be regenerated partially or completely in the root canal space with apical openings of 0.7-3.0 mm using dental pulp stem cells, including stem cells from apical papilla (SCAP) and subpopulations of pulp stem cells. Bone marrow mesenchymal stem cells (BMMSCs) and adipose tissue-derived MSCs (ADMSCs) have also been shown to regenerate pulp-like tissue. In contrast, the cell-free approach has not produced convincing evidence on pulp regeneration. However, one crucial concept has not been considered nor defined in the field of pulp/dentin regeneration and that is the critical size defect of dentin and pulp. Without such consideration and definition, it is difficult to predict or anticipate the extent of cell-free pulp regeneration that would occur. By reasoning, cell-free therapy is unlikely to regenerate an organ/tissue after total loss. Similarly, after a total loss of pulp, it is unlikely to regenerate without using exogenously introduced cells. A cell homing approach may provide a limited amount of tissue regeneration. Although stem cell-based pulp/dentin regeneration has shown great promise, clinical trials are difficult to launch at present. This article will address several issues that challenge and hinder the clinical applications of pulp/dentin regeneration which need to be overcome before stem cell-based pulp/dentin regeneration can occur in the clinic.

Ocular Stem Cell Research from Basic Science to Clinical Application: A Report from Zhongshan Ophthalmic Center Ocular Stem Cell Symposium

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Hong Ouyang

2016-03-01

Full Text Available Stem cells hold promise for treating a wide variety of diseases, including degenerative disorders of the eye. The eye is an ideal organ for stem cell therapy because of its relative immunological privilege, surgical accessibility, and its being a self-contained system. The eye also has many potential target diseases amenable to stem cell-based treatment, such as corneal limbal stem cell deficiency, glaucoma, age-related macular degeneration (AMD, and retinitis pigmentosa (RP. Among them, AMD and glaucoma are the two most common diseases, affecting over 200 million people worldwide. Recent results on the clinical trial of retinal pigment epithelial (RPE cells from human embryonic stem cells (hESCs and induced pluripotent stem cells (iPSCs in treating dry AMD and Stargardt’s disease in the US, Japan, England, and China have generated great excitement and hope. This marks the beginning of the ocular stem cell therapy era. The recent Zhongshan Ophthalmic Center Ocular Stem Cell Symposium discussed the potential applications of various stem cell types in stem cell-based therapies, drug discoveries and tissue engineering for treating ocular diseases.

Clinical and Radiographic Evaluation of the Effectiveness of Formocresol, Mineral Trioxide Aggregate, Portland Cement, and Enamel Matrix Derivative in Primary Teeth Pulpotomies: A Two Year Follow-Up.

Science.gov (United States)

Yildirim, Ceren; Basak, Feridun; Akgun, Ozlem Marti; Polat, Gunseli Guven; Altun, Ceyhan

2016-01-01

The aim of this study was to evaluate and to compare clinical and radiographic outcomes of 4 materials (formocresol, mineral trioxide aggregate (MTA), Portland cement and enamel matrix derivative) using in primary teeth pulpotomies. Sixty-five patients aged 5-9 years (32 female, 33 male) were included in this study. A total of 140 primary first and second molars with deep caries were treated with pulpotomy. All teeth were then restored with stainless steel crowns. The treated teeth were evaluated clinically and radiographically at 3, 6, 12, 18 and 24 months. At 24 months, the clinical success rates of formocresol, MTA, Portland cement, and enamel matrix derivative were 96.9%, 100%, 93.9%, and 93.3%, respectively. The corresponding radiographic success rates were 84.4%, 93.9%, 86.7% and 78.1%, respectively. Although there were no statistically significant differences in clinical and radiographic success rates among the 4 groups, MTA appears to be superior to formocresol, Portland cement, and enamel matrix derivative as a pulpotomy agent in primary teeth.

Concepts for the clinical use of stem cells in equine medicine

DEFF Research Database (Denmark)

Koch, Thomas Gadegaard; Berg, Lise Charlotte; Betts, Dean H.

2008-01-01

experimental and empirical commercial use. A better understanding of equine stem cell biology and concepts is needed in order to develop and evaluate rational clinical applications in the horse. Controlled, well-designed studies of the basic biologic characteristics and properties of these cells are needed......Stem cells from various tissues hold great promise for their therapeutic use in horses, but so far efficacy or proof-of-principle has not been established. The basic characteristics and properties of various equine stem cells remain largely unknown, despite their increasingly widespread...

Mesenchymal stem cells: biological characteristics and potential clinical applications

DEFF Research Database (Denmark)

Kassem, Moustapha

2004-01-01

are among the first stem cell types to be introduced in the clinic. Several studies have demonstrated the possible use of MSC in systemic transplantation for systemic diseases, local implantation for local tissue defects, as a vehicle for genes in gene therapy protocols or to generate transplantable tissues...... and organs in tissue engineering protocols. Before their widespread use in therapy, methods allowing the generation of large number of cells without affecting their differentiation potential as well as technologies that overcome immunological rejection (in case allogenic transplantation) must be developed.......Mesenchymal stem cells (MSC) are clonogenic, non-hematpoietic stem cells present in the bone marrow and are able to differentiate into multiple mesoderm-type cell lineages, for example, osteoblasts, chondrocytes, endothelial-cells and also non-mesoderm-type lineages, for example, neuronal...

The behavior of implant-supported dentures and abutments using the cemented cylinder technique with different resinous cements

Directory of Open Access Journals (Sweden)

Ivete Aparecida de Mathias Sartori

2008-01-01

Full Text Available Objective: Evaluate the behavior of implant-supported dentures and their components, made by cemented cylinder technique, using threetypes of resin cements. Methods: Fifty three patients, of whom 26 were women and 27 men, aged between 25 and 82 years. Results: With partial (54.43% and total (45.57% implant-supported dentures, of the Cone Morse, external and internal hexagon types (Neodent®, Curitiba, Brazil, totaling 237 fixations, were analyzed. The resin cements used were Panavia® (21.94%, EnForce® (58.23% and Rely X® (19.83% and the components were used in accordance with the Laboratory Immediate Loading - Neodent® sequence. The period of time of denture use ranged between 1 and 5 years. The results reported that 5(2.1% cylinders were loosened from metal structure (both belonging to Rely X group, 2(0.48% implants were lost after the first year of use, 16(6.75% denture retention screws wereloosened and 31(13.08% abutment screws were unloosened.Conclusion: The reasons for these failures probably are: metal structure internal retention failure, occlusal pattern, cementation technique and loading conditions. The cemented cylinder technique was effective when used in partial and total implant-supported rehabilitations, keeping prosthetic components stable, despite the resin cement utilized. However, further clinical studies must be conducted.

A comparative study of high-viscosity cement percutaneous vertebroplasty vs. low-viscosity cement percutaneous kyphoplasty for treatment of osteoporotic vertebral compression fractures.

Science.gov (United States)

Sun, Kai; Liu, Yang; Peng, Hao; Tan, Jun-Feng; Zhang, Mi; Zheng, Xian-Nian; Chen, Fang-Zhou; Li, Ming-Hui

2016-06-01

The clinical effects of two different methods-high-viscosity cement percutaneous vertebroplasty (PVP) and low-viscosity cement percutaneous kyphoplasty (PKP) in the treatment of osteoporotic vertebral compression fractures (OVCFs) were investigated. From June 2010 to August 2013, 98 cases of OVCFs were included in our study. Forty-six patients underwent high-viscosity PVP and 52 patients underwent low-viscosity PKP. The occurrence of cement leakage was observed. Pain relief and functional activity were evaluated using the Visual Analog Scale (VAS) and Oswestry Disability Index (ODI), respectively. Restoration of the vertebral body height and angle of kyphosis were assessed by comparing preoperative and postoperative measurements of the anterior heights, middle heights and the kyphotic angle of the fractured vertebra. Nine out of the 54 vertebra bodies and 11 out of the 60 vertebra bodies were observed to have cement leakage in the high-viscosity PVP and low-viscosity PKP groups, respectively. The rate of cement leakage, correction of anterior vertebral height and kyphotic angles showed no significant differences between the two groups (P>0.05). Low-viscosity PKP had significant advantage in terms of the restoration of middle vertebral height as compared with the high-viscosity PVP (Pviscosity PVP and low-viscosity PKP have similar clinical effects in terms of the rate of cement leakage, restoration of the anterior vertebral body height, changes of kyphotic angles, functional activity, and pain relief. Low-viscosity PKP is better than high-viscosity PVP in restoring the height of the middle vertebra.

ULTRA-LIGHTWEIGHT CEMENT

International Nuclear Information System (INIS)

Fred Sabins

2001-01-01

The objective of this project is to develop an improved ultra-lightweight cement using ultralight hollow glass spheres (ULHS). Work reported herein addresses Task 1: Assess Ultra-Lightweight Cementing Problems and Task 3: Test Ultra-Lightweight Cements. Results reported this quarter include a review and summary of Halliburton Energy Services (HES) and BJ Services historical performance data for lightweight cement applications. These data are analyzed and compared to ULHS cement and foamed cement performances. Similar data is expected from Schlumberger, and an analysis of this data will be completed in the following phases of the project. Quality control testing of materials used to formulate ULHS cements in the laboratory was completed to establish baseline material performance standards. A testing protocol was developed employing standard procedures as well as procedures tailored to evaluate ULHS and foamed cement. This protocol is presented and discussed. Results of further testing of ULHS cements are presented along with an analysis to establish cement performance design criteria to be used during the remainder of the project. Finally, a list of relevant literature on lightweight cement performance is compiled for review during the next quarter

The Alpha Stem Cell Clinic: a model for evaluating and delivering stem cell-based therapies.

Science.gov (United States)

Trounson, Alan; DeWitt, Natalie D; Feigal, Ellen G

2012-01-01

Cellular therapies require the careful preparation, expansion, characterization, and delivery of cells in a clinical environment. There are major challenges associated with the delivery of cell therapies and high costs that will limit the companies available to fully evaluate their merit in clinical trials, and will handicap their application at the present financial environment. Cells will be manufactured in good manufacturing practice or near-equivalent facilities with prerequisite safety practices in place, and cell delivery systems will be specialized and require well-trained medical and nursing staff, technicians or nurses trained to handle cells once delivered, patient counselors, as well as statisticians and database managers who will oversee the monitoring of patients in relatively long-term follow-up studies. The model proposed for Alpha Stem Cell Clinics will initially use the capacities and infrastructure that exist in the most advanced tertiary medical clinics for delivery of established bone marrow stem cell therapies. As the research evolves, they will incorporate improved procedures and cell preparations. This model enables commercialization of medical devices, reagents, and other products required for cell therapies. A carefully constructed cell therapy clinical infrastructure with the requisite scientific, technical, and medical expertise and operational efficiencies will have the capabilities to address three fundamental and critical functions: 1) fostering clinical trials; 2) evaluating and establishing safe and effective therapies, and 3) developing and maintaining the delivery of therapies approved by the Food and Drug Administration, or other regulatory agencies.

Cement-latex grouting mortar for cementing boreholes

Energy Technology Data Exchange (ETDEWEB)

Kateev, I S; Golyshkina, L A; Gorbunova, I V; Kurochkin, B M; Vakula, Ya V

1980-01-01

The need for the development of cement-latex grouting mortar for the purpose of separating strata when reinforcing boreholes at deposits in the Tatar Associated SSR is evaluated. Results of studies of the physical and mechanical properties of cement-latex grouting mortar systems (mortar plus brick) are presented. Formulas for preparing cement-latex grouting mortor are evaluated and results of industrial tests of such mortars shown.

TOPICAL REVIEW: Stem cell technology using bioceramics: hard tissue regeneration towards clinical application

Science.gov (United States)

Ohnishi, Hiroe; Oda, Yasuaki; Ohgushi, Hajime

2010-02-01

Mesenchymal stem cells (MSCs) are adult stem cells which show differentiation capabilities toward various cell lineages. We have already used MSCs for treatments of osteoarthritis, bone necrosis and bone tumor. For this purpose, culture expanded MSCs were combined with various ceramics and then implanted. Because of rejection response to allogeneic MSC implantation, we have utilized patients' own MSCs for the treatment. Bone marrow is a good cell source of MSCs, although the MSCs also exist in adipose tissue. When comparing osteogenic differentiation of these MSCs, bone marrow MSCs show more extensive bone forming capability than adipose MSCs. Thus, the bone marrow MSCs are useful for bone tissue regeneration. However, the MSCs show limited proliferation and differentiation capabilities that hindered clinical applications in some cases. Recent advances reveal that transduction of plural transcription factors into human adult cells results in generation of new type of stem cells called induced pluripotent stem cells (iPS cells). A drawback of the iPS cells for clinical applications is tumor formation after their in vivo implantation; therefore it is difficult to use iPS cells for the treatment. To circumvent the problem, we transduced a single factor of either SOX2 or NANOG into the MSCs and found high proliferation as well as osteogenic differentiation capabilities of the MSCs. The stem cells could be combined with bioceramics for clinical applications. Here, we summarize our recent technologies using adult stem cells in viewpoints of bone tissue regeneration.

Study on Cr(VI) Leaching from Cement and Cement Composites

Science.gov (United States)

Palascakova, Lenka; Kanuchova, Maria

2018-01-01

This paper reports an experimental study on hexavalent chromium leaching from cement samples and cement composites containing silica fume and zeolite additions that were subjected to various leaching agents. The water-soluble Cr(VI) concentrations in cements ranged from 0.2 to 3.2 mg/kg and represented only 1.8% of the total chromium content. The presence of chromium compounds with both chromium oxidation states of III and VI was detected in the cement samples by X-ray photoelectron spectroscopy (XPS). Leaching tests were performed in a Britton-Robinson buffer to simulate natural conditions and showed increased dissolution of Cr(VI) up to 6 mg/kg. The highest amount of leached hexavalent chromium was detected after leaching in HCl. The findings revealed that the leaching of chromium from cements was higher by 55–80% than that from the cement composites. A minimum concentration was observed for all cement samples when studying the relationship between the soluble Cr(VI) and the cement storage time. PMID:29690550

Adult Stromal (Skeletal, Mesenchymal) Stem Cells: Advances Towards Clinical Applications

DEFF Research Database (Denmark)

Kermani, Abbas Jafari; Harkness, Linda; Zaher, Walid

2014-01-01

Mesenchymal Stem Cells (MSC) are non-hematopoietic adult stromal cells that reside in a perivascular niche in close association with pericytes and endothelial cells and possess self-renewal and multi-lineage differentiation capacity. The origin, unique properties, and therapeutic benefits of MSC ...... the translation of MSC into clinic: Generation of MSC-like cells from human pluripotent stem cells, strategies to enhance homing of MSC to injured tissues, and targeting of MSC in vivo.......Mesenchymal Stem Cells (MSC) are non-hematopoietic adult stromal cells that reside in a perivascular niche in close association with pericytes and endothelial cells and possess self-renewal and multi-lineage differentiation capacity. The origin, unique properties, and therapeutic benefits of MSC...

ULTRA-LIGHTWEIGHT CEMENT

International Nuclear Information System (INIS)

Fred Sabins

2001-01-01

The objective of this project is to develop an improved ultra-lightweight cement using ultra-lightweight hollow glass spheres (ULHS). Work reported herein addresses Task 1: Assess Ultra-Lightweight Cementing Issues, Task 2: Review Russian Ultra-Lightweight Cement Literature, Task 3: Test Ultra-Lightweight Cements, and Task 8: Develop Field ULHS Cement Blending and Mixing Techniques. Results reported this quarter include: preliminary findings from a literature review focusing on problems associated with ultra-lightweight cements; summary of pertinent information from Russian ultra-lightweight cement literature review; laboratory tests comparing ULHS slurries to foamed slurries and sodium silicate slurries for two different applications; and initial laboratory studies with ULHS in preparation for a field job

Antibacterial Activity of Dental Cements Containing Quaternary Ammonium Polyethylenimine Nanoparticles

International Nuclear Information System (INIS)

Beyth, N.; Weiss, E.I.; Pilo, R.

2012-01-01

Glass ionomer cements (GICs) are commonly used for cementing full cast crown restorations. Regrettably, although the dental cements fill the gap between the tooth and the crown, bacterial micro leakage may occur, resulting in secondary caries. As micro leakage cannot be completely prevented, GCS possessing antibacterial properties are in demand. In the present study the antibacterial activity of insoluble, cross-linked quaternary ammonium polyethylenimine (Qp) nanoparticles incorporated at 1% w/w in two clinically available GCS were studied. The antibacterial activity was tested against Streptococcus mutans and Lactobacillus casei using the direct contact test (Dct) and the agar diffusion test (Ad). Using the direct contact test, antibacterial activity (P<0.05) was found in both tested GICs with incorporated QPEI nanoparticles, the effect lasting for at least one month. However, the ADT showed no inhibition halo in the test bacteria, indicating that the antimicrobial nanoparticles do not diffuse into the agar. The results show that the incorporation of QPEI nanoparticles in glass ionomer cements has a long-lasting antibacterial effect against Streptococcus mutans and Lactobacillus casei. Changing the antibacterial properties of glass ionomer cements by incorporating QPEI antibacterial nanoparticles may prolong the clinical performance of dental crowns.

Antibacterial Activity of Dental Cements Containing Quaternary Ammonium Polyethylenimine Nanoparticles

Directory of Open Access Journals (Sweden)

Nurit Beyth

2012-01-01

Full Text Available Glass ionomer cements (GICs are commonly used for cementing full cast crown restorations. Regrettably, although the dental cements fill the gap between the tooth and the crown, bacterial microleakage may occur, resulting in secondary caries. As microleakage cannot be completely prevented, GICs possessing antibacterial properties are in demand. In the present study the antibacterial activity of insoluble, cross-linked quaternary ammonium polyethylenimine (QPEI nanoparticles incorporated at 1% w/w in two clinically available GICs were studied. The antibacterial activity was tested against Streptococcus mutans and Lactobacillus casei using the direct contact test (DCT and the agar diffusion test (ADT. Using the direct contact test, antibacterial activity (<0.05 was found in both tested GICs with incorporated QPEI nanoparticles, the effect lasting for at least one month. However, the ADT showed no inhibition halo in the test bacteria, indicating that the antimicrobial nanoparticles do not diffuse into the agar. The results show that the incorporation of QPEI nanoparticles in glass ionomer cements has a long-lasting antibacterial effect against Streptococcus mutans and Lactobacillus casei. Changing the antibacterial properties of glass ionomer cements by incorporating QPEI antibacterial nanoparticles may prolong the clinical performance of dental crowns.

Portland cement versus MTA as a root-end filling material. A pilot study.

Science.gov (United States)

da Silva, Sérgio Ribeiro; da Silva Neto, José Dias; Veiga, Daniela Francescato; Schnaider, Taylor Brandão; Ferreira, Lydia Masako

2015-02-01

To assess periradicular lesions clinically and by computed tomography (CT) after endodontic surgery using either Portland cement or mineral trioxide aggregate (MTA) as a root-end filling material. Three patients diagnosed with periradicular lesions by cone-beam CT underwent endodontic surgery with root-end filling. Patient A was treated with MTA as the root-end filling material, patient B was treated with Portland cement and patient C had two teeth treated, one with MTA and the other with Portland cement. Six months after surgery, the patients were assessed clinically and by CT scan and the obtained results were compared. Periradicular tissue regeneration was observed in all cases, with no significant differences in bone formation when comparing the use of MTA and Portland cement as root-end filling materials. Both mineral trioxide aggregate and Portland cement were successful in the treatment of periradicular lesions.

Cement Formation

DEFF Research Database (Denmark)

Telschow, Samira; Jappe Frandsen, Flemming; Theisen, Kirsten

2012-01-01

Cement production has been subject to several technological changes, each of which requires detailed knowledge about the high multiplicity of processes, especially the high temperature process involved in the rotary kiln. This article gives an introduction to the topic of cement, including...... an overview of cement production, selected cement properties, and clinker phase relations. An extended summary of laboratory-scale investigations on clinkerization reactions, the most important reactions in cement production, is provided. Clinker formations by solid state reactions, solid−liquid and liquid......−liquid reactions are discussed, as are the influences of particles sizes on clinker phase formation. Furthermore, a mechanism for clinker phase formation in an industrial rotary kiln reactor is outlined....

Stem Cell Research and Clinical Translation: A Roadmap about Good Clinical Practice and Patient Care

Directory of Open Access Journals (Sweden)

Paola Frati

2017-01-01

Full Text Available The latest research achievements in the field of stem cells led in 2016 to the publication of “Guidelines for Stem Cell Research and Clinical Translation” by the International Society for Stem Cell Research (ISSCR. Updating the topics covered in previous publications, the new recommendations offer interesting ethical and scientific insights. Under the common principles of research integrity, protection of patient’s welfare, respect for the research subjects, transparency and social justice, the centrality of good clinical practice, and informed consent in research and translational medicine is supported. The guidelines implement the abovementioned publications, requiring rigor in all areas of research, promoting the validity of the scientific activity results and emphasizing the need for an accurate and efficient public communication. This paper aims to analyze the aforementioned guidelines in order to provide a valid interpretive tool for experts. In particular, a research activity focused on the bioethical, scientific, and social implications of the new recommendations is carried out in order to provide food for thought. Finally, as an emerging issue of potential impact of current guidelines, an overview on implications of compensation for egg donation is offered.

Application of MultiStem® allogeneic cells for immunomodulatory therapy: clinical progress and pre-clinical challenges in prophylaxis for graft vs host disease

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Bart eVaes

2012-11-01

Full Text Available The last decade has seen much progress in adjunctive cell therapy for immune disorders. Both corporate and institutional Phase III studies have been run using mesenchymal stromal cells (MSC for treatment of Graft vs Host Disease (GvHD, and product approval has been achieved for treatment of pediatric GvHD in Canada and New Zealand (Prochymal®; Osiris Therapeutics. This effectiveness has prompted the prophylactic use of adherent stem cells at the time of allogeneic hematopoietic stem cell transplantation (HSCT to prevent occurrence of GvHD and possibly provide stromal support for hematopoietic recovery. The MultiStem® product is an adult adherent stem cell product derived from bone marrow which has significant clinical exposure. MultiStem cells are currently in phase II clinical studies for treatment of ischemic stroke and ulcerative colitis, with Phase I studies completed in acute myocardial infarction and for GvHD prophylaxis in allogeneic HSCT, demonstrating that MultiStem administration was well tolerated while the incidence and severity of GvHD was reduced. In advancing this clinical approach, it is important to recognize that alternate models exist based on clinical manufacturing strategies. Corporate sponsors exploit the universal donor properties of adherent stem cells and manufacture at large scale, with many products obtained from one or limited donors and used across many patients. In Europe, institutional sponsors often produce allogeneic product in a patient designated context. For this approach, disposable bioreactors producing <10 products per donor in a closed system manner are very well suited. In this review, the use of adherent stem cells for GvHD prophylaxis is summarized and the suitability of disposable bioreactors for MultiStem production is presented, with an emphasis on quality control parameters, which are critical with a multiple donor approach for manufacturing.

Cementation of Glass-Ceramic Posterior Restorations: A Systematic Review

Science.gov (United States)

van den Breemer, Carline R. G.; Gresnigt, Marco M. M.; Cune, Marco S.

2015-01-01

Aim. The aim of this comprehensive review is to systematically organize the current knowledge regarding the cementation of glass-ceramic materials and restorations, with an additional focus on the benefits of Immediate Dentin Sealing (IDS). Materials and Methods. An extensive literature search concerning the cementation of single-unit glass-ceramic posterior restorations was conducted in the databases of MEDLINE (Pubmed), CENTRAL (Cochrane Central Register of Controlled Trials), and EMBASE. To be considered for inclusion, in vitro and in vivo studies should compare different cementation regimes involving a “glass-ceramic/cement/human tooth” complex. Results and Conclusions. 88 studies were included in total. The in vitro data were organized according to the following topics: (micro)shear and (micro)tensile bond strength, fracture strength, and marginal gap and integrity. For in vivo studies survival and quality of survival were considered. In vitro studies showed that adhesive systems (3-step, etch-and-rinse) result in the best (micro)shear bond strength values compared to self-adhesive and self-etch systems when luting glass-ceramic substrates to human dentin. The highest fracture strength is obtained with adhesive cements in particular. No marked clinical preference for one specific procedure could be demonstrated on the basis of the reviewed literature. The possible merits of IDS are most convincingly illustrated by the favorable microtensile bond strengths. No clinical studies regarding IDS were found. PMID:26557651

Evaluation of the amount of excess cement around the margins of cement-retained dental implant restorations: the effect of the cement application method.

Science.gov (United States)

Chee, Winston W L; Duncan, Jesse; Afshar, Manijeh; Moshaverinia, Alireza

2013-04-01

Complete removal of excess cement from subgingival margins after cementation of implant-supported restorations has been shown to be unpredictable. Remaining cement has been shown to be associated with periimplant inflammation and bleeding. The purpose of this study was to investigate and compare the amount of excess cement after cementation with 4 different methods of cement application for cement-retained implant-supported restorations. Ten implant replicas/abutments (3i) were embedded in acrylic resin blocks. Forty complete veneer crowns (CVCs) were fabricated by waxing onto the corresponding plastic waxing sleeves. The wax patterns were cast and the crowns were cemented to the implant replicas with either an interim (Temp Bond) or a definitive luting agent (FujiCEM). Four methods of cement application were used for cementation: Group IM-Cement applied on the internal marginal area of the crown only; Group AH-Cement applied on the apical half of the axial walls of the crown; Group AA-Cement applied to all axial walls of the interior surface of the crown, excluding the occlusal surface; and Group PI-Crown filled with cement then seated on a putty index formed to the internal configuration of the restoration (cementation device) (n=10). Cement on the external surfaces was removed before seating the restoration. Cement layers were applied on each crown, after which the crown was seated under constant load (80 N) for 10 minutes. The excess cement from each specimen was collected and measured. One operator performed all the procedures. Results for the groups were compared, with 1 and 2-way ANOVA and the Tukey multiple range test (α=.05). No significant difference in the amount of excess/used cement was observed between the 2 different types of cements (P=.1). Group PI showed the least amount of excess cement in comparison to other test groups (P=.031). No significant difference was found in the amount of excess cement among groups MI, AH, and AA. Group AA showed the

76 FR 76760 - Gray Portland Cement and Cement Clinker From Japan

Science.gov (United States)

2011-12-08

... and Cement Clinker From Japan Determination On the basis of the record \\1\\ developed in the subject... duty order on gray Portland cement and cement clinker from Japan would be likely to lead to... and Cement Clinker from Japan: Investigation No. 731- TA-461 (Third Review). By order of the...

A Review of Glass-Ionomer Cements for Clinical Dentistry

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Sharanbir K. Sidhu

2016-06-01

Full Text Available This article is an updated review of the published literature on glass-ionomer cements and covers their structure, properties and clinical uses within dentistry, with an emphasis on findings from the last five years or so. Glass-ionomers are shown to set by an acid-base reaction within 2–3 min and to form hard, reasonably strong materials with acceptable appearance. They release fluoride and are bioactive, so that they gradually develop a strong, durable interfacial ion-exchange layer at the interface with the tooth, which is responsible for their adhesion. Modified forms of glass-ionomers, namely resin-modified glass-ionomers and glass carbomer, are also described and their properties and applications covered. Physical properties of the resin-modified glass-ionomers are shown to be good, and comparable with those of conventional glass-ionomers, but biocompatibility is somewhat compromised by the presence of the resin component, 2 hydroxyethyl methacrylate. Properties of glass carbomer appear to be slightly inferior to those of the best modern conventional glass-ionomers, and there is not yet sufficient information to determine how their bioactivity compares, although they have been formulated to enhance this particular feature.

Nanoparticulate fillers improve the mechanical strength of bone cement.

Science.gov (United States)

Gomoll, Andreas H; Fitz, Wolfgang; Scott, Richard D; Thornhill, Thomas S; Bellare, Anuj

2008-06-01

Polymethylmethacrylate (PMMA-) based bone cement contains micrometer-size barium sulfate or zirconium oxide particles to radiopacify the cement for radiographic monitoring during follow-up. Considerable effort has been expended to improve the mechanical qualities of cements, largely through substitution of PMMA with new chemical structures. The introduction of these materials into clinical practice has been complicated by concerns over the unknown long-term risk profile of these new structures in vivo. We investigated a new composite with the well characterized chemical composition of current cements, but with nanoparticles instead of the conventional, micrometer-size barium sulfate radiopacifier. In this study, we replaced the barium sulfate microparticles that are usually present in commercial PMMA cements with barium sulfate nanoparticles. The resultant "microcomposite" and "nanocomposite" cements were then characterized through morphological investigations such as ultra-small angle X-ray scattering (USAXS) and scanning electron microscopy (SEM). Mechanical characterization included compression, tensile, compact tension, and fatigue testing. SEM and USAXS showed excellent dispersion of nanoparticles. Substitution of nanoparticles for microparticles resulted in a 41% increase in tensile strain-to-failure (p = 0.002) and a 70% increase in tensile work-of-fracture (p = 0.005). The nanocomposite cement also showed a two-fold increase in fatigue life compared to the conventional, microcomposite cement. In summary, nanoparticulate substitution of radiopacifiers substantially improved the in vitro mechanical properties of PMMA bone cement without changing the known chemical composition.

A prospective clinical trial on the influence of a triamcinolone/demeclocycline and a calcium hydroxide based temporary cement on pain perception

Directory of Open Access Journals (Sweden)

Willershausen Brita

2012-03-01

Full Text Available Abstract Introduction The aim of this clinical trial was to compare the degree of short term post-operative irritation after application of a triamcinolone/demeclocycyline based or a calcium hydroxide based provisional cement. Methods A total of 109 patients (55 female and 54 male; mean age: 51 ± 14 years with primary or secondary dentinal caries were randomly assigned to the two treatment groups of this biomedical clinical trial (phase III. Selection criteria were good systemic health and treated teeth, which were vital and showed no symptoms of pulpitis. Up to three teeth were prepared for indirect metallic restorations, and the provisional restorations were cemented with a triamcinolone/demeclocycyline (Ledermix or a calcium hydroxide (Provicol based material. The intensity of post-operative pain experienced was documented according to the VAS (4, 12, 20, 24, and 82 h and compared to VAS baseline. Results A total of 159 teeth were treated (Ledermix: 83 teeth, Provicol: 76 teeth. The minor irritation of the teeth, experienced prior to treatment, was similar in both groups; however, 4 h after treatment this value was significantly higher in the Provicol group than in the Ledermix group (p Conclusions The patients had no long term post-operative pain experience in both groups. However, within the first hours after cementation the sensation of pain was considerably higher in the Provicol group than in the Ledermix group.

Cementing a wellbore using cementing material encapsulated in a shell

Energy Technology Data Exchange (ETDEWEB)

Aines, Roger D.; Bourcier, William L.; Duoss, Eric B.; Spadaccini, Christopher M.; Cowan, Kenneth Michael

2016-08-16

A system for cementing a wellbore penetrating an earth formation into which a pipe extends. A cement material is positioned in the space between the wellbore and the pipe by circulated capsules containing the cement material through the pipe into the space between the wellbore and the pipe. The capsules contain the cementing material encapsulated in a shell. The capsules are added to a fluid and the fluid with capsules is circulated through the pipe into the space between the wellbore and the pipe. The shell is breached once the capsules contain the cementing material are in position in the space between the wellbore and the pipe.

Cementing a wellbore using cementing material encapsulated in a shell

Energy Technology Data Exchange (ETDEWEB)

Aines, Roger D.; Bourcier, William L.; Duoss, Eric B.; Floyd, III, William C.; Spadaccini, Christopher M.; Vericella, John J.; Cowan, Kenneth Michael

2017-03-14

A system for cementing a wellbore penetrating an earth formation into which a pipe extends. A cement material is positioned in the space between the wellbore and the pipe by circulated capsules containing the cement material through the pipe into the space between the wellbore and the pipe. The capsules contain the cementing material encapsulated in a shell. The capsules are added to a fluid and the fluid with capsules is circulated through the pipe into the space between the wellbore and the pipe. The shell is breached once the capsules contain the cementing material are in position in the space between the wellbore and the pipe.

Imaging: Guiding the Clinical Translation of Cardiac Stem Cell Therapy

Science.gov (United States)

Nguyen, Patricia K.; Lan, Feng; Wang, Yongming; Wu, Joseph C.

2011-01-01

Stem cells have been touted as the holy grail of medical therapy with promises to regenerate cardiac tissue, but it appears the jury is still out on this novel therapy. Using advanced imaging technology, scientists have discovered that these cells do not survive nor engraft long-term. In addition, only marginal benefit has been observed in large animal studies and human trials. However, all is not lost. Further application of advanced imaging technology will help scientists unravel the mysteries of stem cell therapy and address the clinical hurdles facing its routine implementation. In this review, we will discuss how advanced imaging technology will help investigators better define the optimal delivery method, improve survival and engraftment, and evaluate efficacy and safety. Insights gained from this review may direct the development of future preclinical investigations and clinical trials. PMID:21960727

Natural cement as the precursor of Portland cement: Methodology for its identification

International Nuclear Information System (INIS)

Varas, M.J.; Alvarez de Buergo, M.; Fort, R.

2005-01-01

When cements appeared in the 19th century, they took the place of traditional binding materials (lime, gypsum, and hydraulic lime) which had been used until that time. Early cements can be divided into two groups, natural and artificial (Portland) cements. Natural cements were introduced first, but their widespread usage was short-lived as they were quickly replaced by artificial cements (Portland), still the most important and predominant today. The main differences between natural and artificial cements arise during the manufacturing process. The final properties of the cements are greatly influenced by differences in the raw materials and burning temperatures employed. The aim of this paper is to assess the efficiency of traditional analytical techniques (petrographic microscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR)) used to differentiate natural and artificial cements

Comparison of the physical and mechanical properties of MTA and portland cement.

Science.gov (United States)

Islam, Intekhab; Chng, Hui Kheng; Yap, Adrian U Jin

2006-03-01

This study evaluated and compared the pH, radiopacity, setting time, solubility, dimensional change, and compressive strength of ProRoot MTA (PMTA), ProRoot MTA (tooth colored formula) (WMTA), white Portland cement (WP), and ordinary Portland cement (OP). The results showed that PMTA and Portland cement have very similar physical properties. However, the radiopacity of Portland cement is much lower than that of PMTA. The compressive strength of PMTA was greater than Portland cement at 28 days. The major constituent of PMTA is Portland cement. Given the low cost of Portland cement and similar properties when compared to PMTA, it is reasonable to consider Portland cement as a possible substitute for PMTA in endodontic applications. However, industrially manufactured Portland cement is not approved currently for use in the United States and therefore no clinical recommendation can be made for its use in the human body. Further in vitro and in vivo tests, especially with regards its biocompatibility, should be conducted to ascertain if it meets the FDA requirements for use as a medical device.

Feasibility of producing nano cement in a traditional cement factory in Iraq

Directory of Open Access Journals (Sweden)

Sada Abdalkhaliq Hasan Alyasri

2017-12-01

Full Text Available This study investigates the economic feasibility of producing nano cement through the establishment of a production line within an existing cement factory. Creating a nano cement production line within the Alkufa Cement factory in Iraq is selected as a case study. Evaluation measures including internal rate of return (IRR, net present value (NPV and breakeven point (BEP are used to evaluate the possible gain that can be achieved from this option. The results demonstrated a positive NPV. The IRR is found to be 26.8% and BEP is reached within 3 years after the establishment of the line. This indicates that producing nano cement in the existing cement factory is economically feasible and can be more advantageous than the ordinary cement.

Resolving ethical issues in stem cell clinical trials: the example of Parkinson disease.

Science.gov (United States)

Lo, Bernard; Parham, Lindsay

2010-01-01

Clinical trials of stem cell transplantation raise ethical issues that are intertwined with scientific and design issues, including choice of control group and intervention, background interventions, endpoints, and selection of subjects. We recommend that the review and IRB oversight of stem cell clinical trials should be strengthened. Scientific and ethics review should be integrated in order to better assess risks and potential benefits. Informed consent should be enhanced by assuring that participants comprehend key aspects of the trial. For the trial to yield generalizable knowledge, negative findings and serious adverse events must be reported.

Bioethics of Clinical Applications of Stem Cells.

Science.gov (United States)

Petrini, Carlo

2017-04-12

The clinical applications of stem cells pose a multitude of problems, including safety, efficacy, information and consent, the right to unproven treatments, the "right to try", costs, access, sustainability, scientific scrupulousness, patents and regulatory aspects, to name but a few. This article does not address individual issues, but rather introduces and discusses some of the possible approaches to solving the problems. The first part compares the consequentialist and deontological approaches, offering an overview of "top-down" and "bottom-up" models and proposing the principles of personalism as applied in clinical settings. The second part of the article suggests practical frameworks for organising the ethical issues, focusing in particular on the medical indications, patient preferences, quality of life, and contextual features.

Sustainable Development of the Cement Industry and Blended Cements to Meet Ecological Challenges

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Konstantin Sobolev

2003-01-01

Full Text Available The world production of cement has greatly increased in the past 10 years. This trend is the most significant factor affecting technological development and the updating of manufacturing facilities in the cement industry. Existing technology for the production of cement clinker is ecologically damaging; it consumes much energy and natural resources and also emits pollutants. A new approach to the production of blended or high-volume mineral additive (HVMA cement helps to improve its ecological compatibility. HVMA cement technology is based on the intergrinding of portland cement clinker, gypsum, mineral additives, and a special complex admixture. This new method increases the compressive strength of ordinary cement, improves durability of the cement-based materials, and - at the same time - uses inexpensive natural mineral additives or industrial by-products. This improvement leads to a reduction of energy consumption per unit of the cement produced. Higher strength, better durability, reduction of pollution at the clinker production stage, and decrease of landfill area occupied by industrial by-products, all provide ecological advantages for HVMA cement.

Cement for Oil Well Cementing Operations in Ghana

African Journals Online (AJOL)

Michael

For Portland cement to qualify as oil well cement, the chemical and physical properties must meet ..... Reservoir Engineering, Stanford University,. Stanford, California, pp. ... Construction”, PhD Thesis, Kwame Nkrumah. University of Science ...

Stem Cells of Dental Origin: Current Research Trends and Key Milestones towards Clinical Application

Directory of Open Access Journals (Sweden)

Athina Bakopoulou

2016-01-01

Full Text Available Dental Mesenchymal Stem Cells (MSCs, including Dental Pulp Stem Cells (DPSCs, Stem Cells from Human Exfoliated Deciduous teeth (SHED, and Stem Cells From Apical Papilla (SCAP, have been extensively studied using highly sophisticated in vitro and in vivo systems, yielding substantially improved understanding of their intriguing biological properties. Their capacity to reconstitute various dental and nondental tissues and the inherent angiogenic, neurogenic, and immunomodulatory properties of their secretome have been a subject of meticulous and costly research by various groups over the past decade. Key milestone achievements have exemplified their clinical utility in Regenerative Dentistry, as surrogate therapeutic modules for conventional biomaterial-based approaches, offering regeneration of damaged oral tissues instead of simply “filling the gaps.” Thus, the essential next step to validate these immense advances is the implementation of well-designed clinical trials paving the way for exploiting these fascinating research achievements for patient well-being: the ultimate aim of this ground breaking technology. This review paper presents a concise overview of the major biological properties of the human dental MSCs, critical for the translational pathway “from bench to clinic.”

Retention of metal-ceramic crowns with contemporary dental cements.

Science.gov (United States)

Johnson, Glen H; Lepe, Xavier; Zhang, Hai; Wataha, John C

2009-09-01

New types of crown and bridge cement are in use by practitioners, and independent studies are needed to assess their effectiveness. The authors conducted a study in three parts (study A, study B, and study C) and to determine how well these new cements retain metal-ceramic crowns. The authors prepared teeth with a 20-degree taper and a 4-millimeter length. They cast high-noble metal-ceramic copings, then fitted and cemented them with a force of 196 newtons. The types of cements they used were zinc phosphate, resin-modified glass ionomer, conventional resin and self-adhesive modified resin. They thermally cycled the cemented copings, then removed them. They recorded the removal force and calculated the stress of dislodgment by using the surface area of each preparation. They used a single-factor analysis of variance to analyze the data (alpha = .05). The mean stresses necessary to remove crowns, in megapascals, were 8.0 for RelyX Luting (3M ESPE, St. Paul, Minn.), 7.3 for RelyX Unicem (3M ESPE), 5.7 for Panavia F (Kuraray America, New York) and 4.0 for Fuji Plus (GC America, Alsip, Ill.) in study A; 8.1 for RelyX Luting, 2.6 for RelyX Luting Plus (3M ESPE) and 2.8 for Fuji CEM (GC America) in study B; and 4.9 for Maxcem (Kerr, Orange, Calif.), 4.0 for BisCem (Bisco, Schaumburg, Ill.), 3.7 for RelyX Unicem Clicker (3M ESPE), 2.9 for iCEM (Heraeus Kulzer, Armonk, N.Y.) and 2.3 for Fleck's Zinc Cement (Keystone Industries, Cherry Hill, N.J.) in study C. Powder-liquid versions of new cements were significantly more retentive than were paste-paste versions of the same cements. The mean value of crown removal stress for the new self-adhesive modified-resin cements varied appreciably among the four cements tested. All cements retained castings as well as or better than did zinc phosphate cement. Powder-liquid versions of cements, although less convenient to mix, may be a better clinical choice when crown retention is an issue. All cements tested will retain castings

Low force cementation.

Science.gov (United States)

Wilson, P R

1996-07-01

The marginal adaptation of full coverage restorations is adversely affected by the introduction of luting agents of various minimum film thicknesses during the cementation process. The increase in the marginal opening may have long-term detrimental effects on the health of both pulpal and periodontal tissues. The purpose of this study was to determine the effects of varying seating forces (2.5, 12.5, 25 N), venting, and cement types on post-cementation marginal elevation in cast crowns. A standardized cement space of 40 microns was provided between a machined gold crown and a stainless steel die. An occlusal vent was placed that could be opened or closed. The post-cementation crown elevation was measured, following the use of two commercially available capsulated dental cements (Phosphacap, and Ketac-cem Applicap). The results indicate that only the combination of Ketac-Cem Applicap and crown venting produced post-cementation crown elevation of less than 20 microns when 12.5 N seating force was used. Higher forces (25 N) and venting were required for comparable seating when using Phosphacap (19 microns). The amount of force required to allow maximum seating of cast crowns appears to be cement specific, and is reduced by effective venting procedures.

Setting Global Standards for Stem Cell Research and Clinical Translation: The 2016 ISSCR Guidelines

Directory of Open Access Journals (Sweden)

George Q. Daley

2016-06-01

Full Text Available The International Society for Stem Cell Research (ISSCR presents its 2016 Guidelines for Stem Cell Research and Clinical Translation (ISSCR, 2016. The 2016 guidelines reflect the revision and extension of two past sets of guidelines (ISSCR, 2006; ISSCR, 2008 to address new and emerging areas of stem cell discovery and application and evolving ethical, social, and policy challenges. These guidelines provide an integrated set of principles and best practices to drive progress in basic, translational, and clinical research. The guidelines demand rigor, oversight, and transparency in all aspects of practice, providing confidence to practitioners and public alike that stem cell science can proceed efficiently and remain responsive to public and patient interests. Here, we highlight key elements and recommendations in the guidelines and summarize the recommendations and deliberations behind them.

Synthesis of Portland cement and calcium sulfoaluminate-belite cement for sustainable development and performance

Science.gov (United States)

Chen, Irvin Allen

Portland cement concrete, the most widely used manufactured material in the world, is made primarily from water, mineral aggregates, and portland cement. The production of portland cement is energy intensive, accounting for 2% of primary energy consumption and 5% of industrial energy consumption globally. Moreover, portland cement manufacturing contributes significantly to greenhouse gases and accounts for 5% of the global CO2 emissions resulting from human activity. The primary objective of this research was to explore methods of reducing the environmental impact of cement production while maintaining or improving current performance standards. Two approaches were taken, (1) incorporation of waste materials in portland cement synthesis, and (2) optimization of an alternative environmental friendly binder, calcium sulfoaluminate-belite cement. These approaches can lead to less energy consumption, less emission of CO2, and more reuse of industrial waste materials for cement manufacturing. In the portland cement part of the research, portland cement clinkers conforming to the compositional specifications in ASTM C 150 for Type I cement were successfully synthesized from reagent-grade chemicals with 0% to 40% fly ash and 0% to 60% slag incorporation (with 10% intervals), 72.5% limestone with 27.5% fly ash, and 65% limestone with 35% slag. The synthesized portland cements had similar early-age hydration behavior to commercial portland cement. However, waste materials significantly affected cement phase formation. The C3S--C2S ratio decreased with increasing amounts of waste materials incorporated. These differences could have implications on proportioning of raw materials for cement production when using waste materials. In the calcium sulfoaluminate-belite cement part of the research, three calcium sulfoaluminate-belite cement clinkers with a range of phase compositions were successfully synthesized from reagent-grade chemicals. The synthesized calcium sulfoaluminate

BoneSource hydroxyapatite cement: a novel biomaterial for craniofacial skeletal tissue engineering and reconstruction.

Science.gov (United States)

Friedman, C D; Costantino, P D; Takagi, S; Chow, L C

1998-01-01

BoneSource-hydroxyapatite cement is a new self-setting calcium phosphate cement biomaterial. Its unique and innovative physical chemistry coupled with enhanced biocompatibility make it useful for craniofacial skeletal reconstruction. The general properties and clinical use guidelines are reviewed. The biomaterial and surgical applications offer insight into improved outcomes and potential new uses for hydroxyapatite cement systems.

Ultrafine portland cement performance

Directory of Open Access Journals (Sweden)

C. Argiz

2018-04-01

Full Text Available By mixing several binder materials and additions with different degrees of fineness, the packing density of the final product may be improved. In this work, ultrafine cement and silica fume mixes were studied to optimize the properties of cement-based materials. This research was performed in mortars made of two types of cement (ultrafine Portland cement and common Portland cement and two types of silica fume with different particle-size distributions. Two Portland cement replacement ratios of 4% and 10% of silica fume were selected and added by means of a mechanical blending method. The results revealed that the effect of the finer silica fume mixed with the coarse cement enhances the mechanical properties and pore structure refinement at a later age. This improvement is somewhat lower in the case of ultrafine cement with silica fume.

Physicochemical properties and biocompatibility of chitosan oligosaccharide/gelatin/calcium phosphate hybrid cements

Energy Technology Data Exchange (ETDEWEB)

Chiang, Ting-Yi [Department of Dental Laboratory Technology, Central Taiwan University of Science and Technology, Taichung 406, Taiwan (China); Ho, Chia-Che [Institute of Oral Biology and Biomaterials Science, Chung-Shan Medical University, Taichung 402, Taiwan (China); Chen, David Chan-Hen [Institute of Veterinary Microbiology, National Chung-Hsing University, Taichung 402, Taiwan (China); Lai, Meng-Heng [Institute of Oral Biology and Biomaterials Science, Chung-Shan Medical University, Taichung 402, Taiwan (China); Ding, Shinn-Jyh, E-mail: sjding@csmu.edu.tw [Institute of Oral Biology and Biomaterials Science, Chung-Shan Medical University, Taichung 402, Taiwan (China); Department of Dentistry, Chung-Shan Medical University Hospital, Taichung 402, Taiwan (China)

2010-04-15

A bone substitute material was developed consisting of a chitosan oligosaccharide (COS) solution in a liquid phase and gelatin (GLT) containing calcium phosphate powder in a solid phase. The physicochemical and biocompatible properties of the hybrid cements were evaluated. The addition of COS to cement did not affect the setting time or diametral tensile strength of the hybrid cements, whereas GLT significantly prolonged the setting time and decreased the strength slightly. The setting reaction was inhibited by the addition of GLT to the initial mixture, but not by COS. However, the presence of GLT appreciably improved the anti-washout properties of the hybrid cement compared with COS. COS may promote the cement's biocompatibility as an approximate twofold increase in cell proliferation for 10% COS-containing cements was observed on day 3 as compared with the controls. The combination of GLT and COS was chosen due to the benefits achieved from several synergistic effects and for their clinical applications. Cement with 5% GLT and 10% COS may be a better choice among cements in terms of anti-washout properties and biological activity.

Radioactive waste cementation

International Nuclear Information System (INIS)

Soriano B, A.

1996-01-01

This research was carried out to develop the most adequate technique to immobilize low and medium-activity radioactive waste. different brands of national cement were used, portland and pozzolanic cement. Prismatic and cylindrical test tubes were prepared with different water/cement (W/C) relationship. Additives such a as clay and bentonite were added in some other cases. Later, the properties of these test tubes were evaluated. Properties such as: mechanical resistance, immersion resistance, lixiviation and porosity resistance. Cement with the highest mechanical resistance values, 62,29 MPa was pozzolanic cement for a W/C relationship of 0,35. It must be mentioned that the other types of cements reached a mechanical resistance over 10 MPa, a value indicated by the international standards for transportation and storage of low and medium-activity radioactive waste at a superficial level. However, in the case of immersion resistance, Sol cement (portland type I) with a W/C relationship of 0,35 reached a compression resistance over 61,92 MPa; as in the previous cases, the other cements reached a mechanical resistance > 10 MPa. Regarding porosity, working with W/C relationships = 0,35 0,40 and 0,45, without additives and with additives, the percentage of porosity found for all cements is lower than 40% percentage indicated by international standards. With regard to the lixiviation test, pozzolanic cement best retained Cesium-137 and Cobalt-60, and increased its advantages when bentonite was added, obtaining a lixiviation rate of 2,02 x E-6 cm/day. Sol cement also improved its properties when bentonite was added and obtained a lixiviation rate of 2,84 x E-6 cm/day for Cesium-137. However, Cobalt-60 is almost completely retained with the 3 types of cement with or without additives, reaching the limits indicated by the international standards for the lixiviation rate of beta-gamma emitter < 5,00E-4 cm/day. Characterizing the final product involves the knowledge of its

Setting global standards for stem cell research and clinical translation : The 2016 ISSCR guidelines

NARCIS (Netherlands)

Daley, George Q.; Hyun, Insoo; Apperley, Jane F.; Barker, Roger A.; Benvenisty, Nissim; Bredenoord, Annelien L.; Breuer, Christopher K.; Caulfield, Timothy; Cedars, Marcelle I.; Frey-Vasconcells, Joyce; Heslop, Helen E.; Jin, Ying; Lee, Richard T.; McCabe, Christopher; Munsie, Megan; Murry, Charles E.; Piantadosi, Steven; Rao, Mahendra; Rooke, Heather M.; Sipp, Douglas; Studer, Lorenz; Sugarman, Jeremy; Takahashi, Masayo; Zimmerman, Mark; Kimmelman, Jonathan

2016-01-01

The International Society for Stem Cell Research (ISSCR) presents its 2016 Guidelines for Stem Cell Research and Clinical Translation (ISSCR, 2016). The 2016 guidelines reflect the revision and extension of two past sets of guidelines (ISSCR, 2006; ISSCR, 2008) to address new and emerging areas of

Setting time and sealing ability of alpha-tricalcium phosphate cement containing titanic oxide.

Science.gov (United States)

Yoshikawa, M; Terada, Y; Toda, T

1998-10-01

We developed a new type of calcium phosphate cement for clinical use in endodontics as a root canal sealer or pulp cupping agent. The solid phase of the sealer is composed of 70% of alpha-tricalcium phosphate (alpha-TCP) and 30% of titanic oxide (TiO2), and the liquid phase is 37% citric acid, 5% tannic acid and 58% distilled water. TiO2 was added to control setting time and handling of the cement. We used commercially available calcium phosphate root canal sealer as a control. ISO standards specify that new endodontic products should be examined thoroughly before clinical use. It is important to carry out in vitro cytotoxicity and in vivo histocompatibility tests. We first did in vitro test of setting time and root canal sealing ability of the cement. We found that this developed calcium phosphate cement had an appropriate setting time and excellent sealing ability as a root canal sealer, and concluded that it was suitable for clinical use as a root canal sealer.

Parameters of Alumina Cement and Portland Cement with Addition of Chalcedonite Meal

Science.gov (United States)

Kotwa, Anna

2017-10-01

Aluminous cement is a quick binder with special properties. It is used primarily to make non-standard monolithic components exposed to high temperatures, + 1300°C. It is also a component of adhesives and mortars. It has a very short setting time. It is characterized by rapid increase in mechanical strength and resistance to aggressive sulphates. It can be used in reinforced concrete structures. Laying of concrete, construction mortar made of alumina cement can be carried out even at temperatures of -10°C. This article discusses a comparison of the parameters of hardened mortar made of alumina cement GÓRKAL 40 and Portland cement CEM I 42.5R. The mortars contain an addition of chalcedonite meal with pozzolanic properties, with particle size of less than 0.063μm. The meal was added in amounts of 5% and 20% of cement weight. Chalcedonite meal used in the laboratory research is waste material, resulting from chalcedonite aggregate mining. It has the same properties as the rock from which it originates. We have compared the parameters of hardened mortar i.e. compressive strength, water absorption and capillarity. The addition of 20% chalcedonite meal to mortars made from aluminous cement will decrease durability by 6.1% relative to aluminous cement mortar without addition of meal. Considering the results obtained during the absorbency tests, it can be stated that the addition of chalcedonite meal reduces weight gains in mortars made with cement CEM I 42.5 R and alumina cement. Use of alumina cement without addition of meal in mortars causes an increase of mass by 248% compared to Portland cement mortars without additions, in the absorption tests. The addition of chalcedonite meal did not cause increased weight gain in the capillary action tests. For the alumina cement mortars, a lesser weight gains of 24.7% was reported, compared to the Portland cement mortar after 28 days of maturing.

Cemented versus Uncemented Oxford Unicompartmental Knee Arthroplasty: Is There a Difference?

Directory of Open Access Journals (Sweden)

Burak Akan

2013-01-01

Full Text Available Purpose. The use of uncemented unicompartmental knee prostheses has recently increased. However, few studies on the outcomes of uncemented unicompartmental knee prostheses have been performed. The purpose of this study was to compare the outcomes of cemented and uncemented Oxford unicompartmental knee arthroplasty. Materials and Methods. This retrospective observational study evaluated the clinical and radiological outcomes of 263 medial Oxford unicompartmental prostheses (141 cemented, 122 uncemented implanted in 235 patients. The mean follow-up was 42 months in the cemented group and 30 months in the uncemented group. Results. At the last follow-up, there were no significant differences in the clinical results or survival rates between the two groups. However, the operation time in the uncemented unicompartmental knee arthroplasty group was shorter than that in the cemented unicompartmental knee arthroplasty group. In addition, the cost of uncemented arthroplasty was greater. Conclusion. Despite the successful midterm results in the uncemented unicompartmental knee arthroplasty group, a longer follow-up period is required to determine the best fixation mode.

Stem cell biobanks.

Science.gov (United States)

Bardelli, Silvana

2010-04-01

Stem cells contribute to innate healing and harbor a promising role for regenerative medicine. Stem cell banking through long-term storage of different stem cell platforms represents a fundamental source to preserve original features of stem cells for patient-specific clinical applications. Stem cell research and clinical translation constitute fundamental and indivisible modules catalyzed through biobanking activity, generating a return of investment.

Stem cells in clinical trials for treatment of retinal degeneration.

Science.gov (United States)

Klassen, Henry

2016-01-01

After decades of basic science research involving the testing of regenerative strategies in animal models of retinal degenerative diseases, a number of clinical trials are now underway, with additional trials set to begin shortly. These efforts will evaluate the safety and preliminary efficacy of cell-based products in the eyes of patients with a number of retinal conditions, notably including age-related macular degeneration, retinitis pigmentosa and Stargardt's disease. This review considers the scientific work and early trials with fetal cells and tissues that set the stage for the current clinical investigatory work, as well the trials themselves, specifically those either now completed, underway or close to initiation. The cells of interest include retinal pigment epithelial cells derived from embryonic stem or induced pluripotent stem cells, undifferentiated neural or retinal progenitors or cells from the vascular/bone marrow compartment or umbilical cord tissue. Degenerative diseases of the retina represent a popular target for emerging cell-based therapeutics and initial data from early stage clinical trials suggest that short-term safety objectives can be met in at least some cases. The question of efficacy will require additional time and testing to be adequately resolved.

Silver-Doped Calcium Phosphate Bone Cements with Antibacterial Properties

Directory of Open Access Journals (Sweden)

J. V. Rau

2016-04-01

Full Text Available Calcium phosphate bone cements (CPCs with antibacterial properties are demanded for clinical applications. In this study, we demonstrated the use of a relatively simple processing route based on preparation of silver-doped CPCs (CPCs-Ag through the preparation of solid dispersed active powder phase. Real-time monitoring of structural transformations and kinetics of several CPCs-Ag formulations (Ag = 0 wt %, 0.6 wt % and 1.0 wt % was performed by the Energy Dispersive X-ray Diffraction technique. The partial conversion of β-tricalcium phosphate (TCP phase into the dicalcium phosphate dihydrate (DCPD took place in all the investigated cement systems. In the pristine cement powders, Ag in its metallic form was found, whereas for CPC-Ag 0.6 wt % and CPC-Ag 1.0 wt % cements, CaAg(PO33 was detected and Ag (met. was no longer present. The CPC-Ag 0 wt % cement exhibited a compressive strength of 6.5 ± 1.0 MPa, whereas for the doped cements (CPC-Ag 0.6 wt % and CPC-Ag 1.0 wt % the reduced values of the compressive strength 4.0 ± 1.0 and 1.5 ± 1.0 MPa, respectively, were detected. Silver-ion release from CPC-Ag 0.6 wt % and CPC-Ag 1.0 wt % cements, measured by the Atomic Emission Spectroscopy, corresponds to the average values of 25 µg/L and 43 µg/L, respectively, rising a plateau after 15 days. The results of the antibacterial test proved the inhibitory effect towards pathogenic Escherichia coli for both CPC-Ag 0.6 wt % and CPC-Ag 1.0 wt % cements, better performances being observed for the cement with a higher Ag-content.

Human tooth germ stem cell response to calcium-silicate based endodontic cements

Directory of Open Access Journals (Sweden)

Esra Pamukcu Guven

2013-07-01

Full Text Available OBJECTIVE: The aim of this study was to compare the cytotoxic effects of endodontic cements on human tooth germ stem cells (hTGSCs. MTA Fillapex, a mineral trioxide aggregate (MTA-based, salicylate resin containing root canal sealer, was compared with iRoot SP, a bioceramic sealer, and AH Plus Jet, an epoxy resin-based root canal sealer. MATERIAL AND METHODS: To evaluate cytotoxicity, all materials were packed into Teflon rings (4 mmµ3 mm and co-cultured with hTGSCs with the aid of 24-well Transwell permeable supports, which had a pore size of 0.4 µm. Coverslips were coated with MTA Fillapex, iRoot SP and AH Plus Jet and each coverslip was placed onto the bottom of one well of a six-well plate for scanning electron microscopy (SEM analysis. Before the cytotoxicity and SEM analysis, all samples were stored at 37ºC and at 95% humidity and 5% CO2 for 24 hours to set. The cellular viability was analyzed using MTS test (3-(4,5-dimethyl-thiazol-2-yl-5-(3-carboxy-methoxy-phenyl-2-(4-sulfo-phenyl-2H-tetrazolium. The cytotoxic effects and SEM visualization of the tested materials were analyzed at 24-hour, 72-hour, one-week and two-week periods. RESULTS: On the 1st day, only MTA Fillapex caused cytotoxicity compared to negative control (NC group (p0.05. After 14 days of incubation with the test materials, MTA Fillapex exhibited significantly higher cytotoxicity compared with iRoot SP, AH Plus Jet and the NC group (P<0.008. In the SEM analysis, the highest levels of cell attachment were observed for iRoot SP and the control group. After 24 hours, MTA Fillapex reduced the number of cells attached to the surface. CONCLUSIONS: Within the limitations of this study, sealers exerted different cytotoxic effects on hTGSCs. Although all materials have exerted cellular toxicity, iRoot SP and AH Plus Jet may promote better attachment to hTGSCs.

Creep and fatigue behavior of a novel 2-component paste-like formulation of acrylic bone cements

OpenAIRE

Köster, U.; Jaeger, R.; Bardts, M.; Wahnes, C.; Büchner, H.; Kühn, K.-D.; Vogt, S.

2013-01-01

The fatigue and creep performance of two novel acrylic bone cement formulations (one bone cement without antibiotics, one with antibiotics) was compared to the performance of clinically used bone cements (Osteopal V, Palacos R, Simplex P, SmartSet GHV, Palacos R+G and CMW1 with Gentamicin). The preparation of the novel bone cement formulations involves the mixing of two paste-like substances in a static mixer integrated into the cartridge which is used to apply the bone cement. The fatigue pe...

Neoplastic stem cells: current concepts and clinical perspectives.

Science.gov (United States)

Schulenburg, Axel; Brämswig, Kira; Herrmann, Harald; Karlic, Heidrun; Mirkina, Irina; Hubmann, Rainer; Laffer, Sylvia; Marian, Brigitte; Shehata, Medhat; Krepler, Clemens; Pehamberger, Hubert; Grunt, Thomas; Jäger, Ulrich; Zielinski, Christoph C; Valent, Peter

2010-11-01

Neoplastic stem cells have initially been characterized in myeloid leukemias where NOD/SCID mouse-repopulating progenitors supposedly reside within a CD34+/Lin- subset of the malignant clone. These progenitors are considered to be self-renewing cells responsible for the in vivo long-term growth of neoplastic cells in leukemic patients. Therefore, these cells represent an attractive target of therapy. In some lymphoid leukemias, NOD/SCID mouse-repopulating cells were also reported to reside within the CD34+/Lin- subfraction of the clone. More recently, several attempts have been made to transfer the cancer stem cell concept to solid tumors and other non-hematopoietic neoplasms. In several of these tumors, the cell surface antigens AC133 (CD133) and CD44 are considered to indicate the potential of a cell to initiate permanent tumor formation in vivo. However, several questions concerning the phenotype, self-renewal capacity, stroma-dependence, and other properties of cancer- or leukemia-initiating cells remain to be solved. The current article provides a summary of our current knowledge on neoplastic (cancer) stem cells, with special emphasis on clinical implications and therapeutic options as well as a discussion about conceptual and technical limitations. Copyright © 2010 Elsevier Ireland Ltd. All rights reserved.

Use of Incineration Solid Waste Bottom Ash as Cement Mixture in Cement Production

Science.gov (United States)

Jun, N. H.; Abdullah, M. M. A. B.; Jin, T. S.; Kadir, A. A.; Tugui, C. A.; Sandu, A. V.

2017-06-01

Incineration solid waste bottom ash was use to examine the suitability as a substitution in cement production. This study enveloped an innovative technology option for designing new equivalent cement that contains incineration solid waste bottom ash. The compressive strength of the samples was determined at 7, 14, 28 and 90 days. The result was compared to control cement with cement mixture containing incineration waste bottom ash where the result proved that bottom ash cement mixture able achieve its equivalent performance compared to control cement which meeting the requirement of the standards according to EN 196-1. The pozzolanic activity index of bottom ash cement mixture reached 0.92 at 28 days and 0.95 at 90 and this values can be concluded as a pozzolanic material with positive pozzolanic activity. Calcium hydroxide in Portland cement decreasing with the increasing replacement of bottom ash where the reaction occur between Ca(OH)2 and active SiO2.

Effect of process variables on the preparation of artificial bone cements

Energy Technology Data Exchange (ETDEWEB)

Santos Junior, J.G.F.; Melo, P.A.; Pinto, J.C., E-mail: pinto@peq.coppe.ufrj.br, E-mail: jjunior@peq.coppe.ufrj.br, E-mail: melo@peq.coppe.ufrj.br [Coordenacao dos Programas de Pos-Graduacao de Engenharia (COPPE/UFRJ), RJ (Brazil). Programa de Engenharia Quimica; Pita, V.J.R.R., E-mail: vjpita@ima.ufrj.br [Universidade Federal do Rio de Janeiro (UFRJ), RJ (Brazil). Instituto de Macromoleculas; Nele, M., E-mail: nele@eq.ufrj.br [Universidade Federal do Rio de Janeiro (UFRJ), RJ (Brazil). Escola de Quimica

2013-10-15

The present work concerns the preparation of bone cements based on poly(methyl methacrylate) (PMMA), used mainly for prosthesis fixation and cavity filling for correction of human bone failures. A typical bone cement recipe contains methyl methacrylate, which polymerizes in situ during cement application. An inherent problem of this reaction is the large amount of heat released during the cement preparation, which may lead to irreparable damage of living tissues. Optimization of PMMA-based bone cement recipes is thus an important step towards safe and reliable clinical usage of these materials. Important process variables related to the reaction temperature profile and the mixing of the recipe constituents were studied in order to allow for the adequate production of bone cements. It is shown that the average molar mass and size of the PMMA particles used in the production of the bone cement, as well as incorporation of radiopaque contrast, co-monomers and fillers into the bone recipe play fundamental roles in the course of the polymerization reaction. Furthermore, the injection vessel geometry may interfere dramatically with the temperature profile and the time for its occurrence. Finally, it has been observed that the morphology of the PMMA particles strongly affects the mixing of the bone cement components. (author)

Effect of process variables on the preparation of artificial bone cements

Directory of Open Access Journals (Sweden)

J. G. F. Santos Jr.

2013-12-01

Full Text Available The present work concerns the preparation of bone cements based on poly(methyl methacrylate (PMMA, used mainly for prosthesis fixation and cavity filling for correction of human bone failures. A typical bone cement recipe contains methyl methacrylate, which polymerizes in situ during cement application. An inherent problem of this reaction is the large amount of heat released during the cement preparation, which may lead to irreparable damage of living tissues. Optimization of PMMA-based bone cement recipes is thus an important step towards safe and reliable clinical usage of these materials. Important process variables related to the reaction temperature profile and the mixing of the recipe constituents were studied in order to allow for the adequate production of bone cements. It is shown that the average molar mass and size of the PMMA particles used in the production of the bone cement, as well as incorporation of radiopaque contrast, co-monomers and fillers into the bone recipe play fundamental roles in the course of the polymerization reaction. Furthermore, the injection vessel geometry may interfere dramatically with the temperature profile and the time for its occurrence. Finally, it has been observed that the morphology of the PMMA particles strongly affects the mixing of the bone cement components.

Detecting Poor Cement Bonding and Zonal Isolation Problems Using Magnetic Cement Slurries

KAUST Repository

Nair, Sriramya D.; Patzek, Tadeusz; van Oort, Eric

2017-01-01

There has been growing interest in the use of magnetorheological fluids to improve displacement efficiency of fluids (drilling fluids, spacer fluids, cement slurries) in the eccentric casing annuli. When magnetic particles are mixed with the cement slurry for improved displacement, they provide an excellent opportunity for sensing the presence and quality of cement in the annulus. This work focuses on using sophisticated 3D computational electromagnetics to simulate the use of a magnetic cement slurry for well cement monitoring. The main goal is to develop a new tool, which is capable of locating magnetic cement slurry that is placed behind a stainless steel casing. An electromagnetic coil was used to generate a magnetic field inside the borehole. It was found that when a current was passed through the electric coils, magnetic field lines passed through the stainless steel casing, the cement annulus and the rock formation. Three sensors were placed inside the cased borehole and the magnetic field strength variations were observed at these locations. Various factors that have a significant influence on zonal isolation were considered. These include, effect of debonding between casing and cement annulus, effect of changing annuli thickness, influence of a fracture in the rock formation, effect of changing magnetic permeability of cement and finally influence of annuli eccentricity. Based on the results shown in the paper along with the next generation of supersensitive magnetic sensors that are being developed, the magnetic approach appears to be a viable alternative for evaluating the quality of the cement annulus to ensure good zonal isolation.

Detecting Poor Cement Bonding and Zonal Isolation Problems Using Magnetic Cement Slurries

KAUST Repository

Nair, Sriramya D.

2017-10-02

There has been growing interest in the use of magnetorheological fluids to improve displacement efficiency of fluids (drilling fluids, spacer fluids, cement slurries) in the eccentric casing annuli. When magnetic particles are mixed with the cement slurry for improved displacement, they provide an excellent opportunity for sensing the presence and quality of cement in the annulus. This work focuses on using sophisticated 3D computational electromagnetics to simulate the use of a magnetic cement slurry for well cement monitoring. The main goal is to develop a new tool, which is capable of locating magnetic cement slurry that is placed behind a stainless steel casing. An electromagnetic coil was used to generate a magnetic field inside the borehole. It was found that when a current was passed through the electric coils, magnetic field lines passed through the stainless steel casing, the cement annulus and the rock formation. Three sensors were placed inside the cased borehole and the magnetic field strength variations were observed at these locations. Various factors that have a significant influence on zonal isolation were considered. These include, effect of debonding between casing and cement annulus, effect of changing annuli thickness, influence of a fracture in the rock formation, effect of changing magnetic permeability of cement and finally influence of annuli eccentricity. Based on the results shown in the paper along with the next generation of supersensitive magnetic sensors that are being developed, the magnetic approach appears to be a viable alternative for evaluating the quality of the cement annulus to ensure good zonal isolation.

21 CFR 888.3353 - Hip joint metal/ceramic/polymer semi-constrained cemented or nonporous uncemented prosthesis.

Science.gov (United States)

2010-04-01

... linkage across-the-joint. The two-part femoral component consists of a femoral stem made of alloys to be... ceramic (aluminium oxide, A1203) head of the femoral component. The acetabular component is made of ultra... nonporous metal alloys, and used with or without bone cement. (b) Classification. Class II. [54 FR 48239...

The cement recycling of the earthquake disaster debris by Hachinohe Cement Co., Ltd

International Nuclear Information System (INIS)

Kataoka, Masayuki

2015-01-01

A tremendous quantity of earthquake disaster debris and tsunami sediment was resulted by the Great East Japan Earthquake on March 11, 2011. Hachinohe Cement Co., Ltd., a Sumitomo Osaka Cement subsidiary, was the first cement industry company to receive and process such waste materials outside of their usual prefecture area, while the company is performing their treatment and recycling services locally in Hachinohe City and Aomori Prefecture. This report provides an explanation about the recycling mechanism of waste materials and by-products in cement manufacturing process, and introduces an example of actual achievements for the disaster debris treatment by utilizing the cement recycling technologies at the Hachinohe Cement Plant. (author)

Effect of Cement Type on Autogenous Deformation of Cement-Based Materials

DEFF Research Database (Denmark)

Pietro, Lura; Ye, Guang; van Breugel, Klaas

2004-01-01

In this paper, measurements of non-evaporable water content, chemical shrinkage, autogenous deformation, internal relative humidity (RH), pore solution composition, and early-age elastic modulus are presented and discussed. All experiments were performed on Portland cement and blast-furnace slag...... (BFS) cement pastes. Self-desiccation shrinkage of the BFS cement paste was modeled based on the RH measurements, following the capillary-tension approach. The main findings of this study are: 1) self-desiccation shrinkage can be related to self-desiccation both for Portland and for BFS cement pastes......, taking into account the influence of the dissolved salts in the pore solution, 2) the BFS cement paste studied shows pronounced self-desiccation and self-desiccation shrinkage, mainly caused by its very fine pore structure....

The clinical application of mesenchymal stromal cells in hematopoietic stem cell transplantation

Directory of Open Access Journals (Sweden)

Ke Zhao

2016-05-01

Full Text Available Abstract Mesenchymal stromal cells (MSCs are multipotent stem cells well known for repairing tissue, supporting hematopoiesis, and modulating immune and inflammation response. These outstanding properties make MSCs as an attractive candidate for cellular therapy in immune-based disorders, especially hematopoietic stem cell transplantation (HSCT. In this review, we outline the progress of MSCs in preventing and treating engraftment failure (EF, graft-versus-host disease (GVHD following HSCT and critically discuss unsolved issues in clinical applications.

Extensively coated revision stems in proximally deficient femur: Early results in 15 patients

Directory of Open Access Journals (Sweden)

Marya SKS

2008-01-01

Full Text Available Background: Hip replacement following failed internal fixation (dynamic hip screw for intertrochanteric fractures or previous hip arthroplasty presents a major surgical challenge. Proximal fitting revision stems do not achieve adequate fixation. Distal fixation with long-stemmed extensively coated cementless implants (like the Solution™ system affords a suitable solution. We present our early results of 15 patients treated with extensively coated cementless revision stems. Materials and Methods: Fifteen patients with severely compromised proximal femora following either failed hip arthroplasty or failed internal fixation (dynamic hip screw fixation for intertrochanteric fractures were operated by the senior author over a two-year period. Eight patients had aseptic loosening of their femoral stems following cemented hip replacements, with severe thinning of their proximal cortices and impending stress fractures. Seven had secondary hip arthritis following failure of long implants for comminuted intertrochanteric or subtrochanteric femoral fractures. All patients were treated by removal of implant (cemented stems/DHS implants and insertion of long-stemmed extensively coated cementless revision (′ Solution™; DePuy, Warsaw (IN, US′ stems along with press-fit acetabular component (Duraloc Cup, DePuy, Warsaw (IN, US. All eight hip revisions needed extended trochanteric osteotomies. Results: All patients were primarily kept in bed on physiotherapy for six weeks and then gradually progressed to weight-bearing walking over the next six to eight weeks. The Harris Hip Scores and patient satisfaction were used for final evaluation. We achieved good results in the short term studied. In our first three patients (all following failed cemented total hip replacements, we resorted to cerclage wiring to hold osteotomised segments (done to facilitate stem removal. The subsequent 12 proceeded without the need for cerclage wiring. One patient had a

Foamed cement for squeeze cementing low-pressure, highly permeable reservoirs

International Nuclear Information System (INIS)

Chmllowski, W.; Kondratoff, L.B.

1992-01-01

Four different cement squeezing techniques have been used on wells producing from the Keg River formation in the Rainbow Lake area of Alberta, Canada. This paper evaluates 151 cement squeeze treatments performed at 96 wellsites and compares the use of foam cement vs. conventional squeeze treatments and techniques. Discussion includes key aspects, such as candidate selection, slurry design, treatment design, economic evaluation, and operational considerations

Advancing Stem Cell Biology toward Stem Cell Therapeutics

OpenAIRE

Scadden, David; Srivastava, Alok

2012-01-01

Here, the International Society for Stem Cell Research (ISSCR) Clinical Translation Committee introduces a series of articles outlining the current status, opportunities, and challenges surrounding the clinical translation of stem cell therapeutics for specific medical conditions.

Continuous monitoring of the zinc-phosphate acid-base cement setting reaction by proton nuclear magnetic relaxation

International Nuclear Information System (INIS)

Apih, T.; Lebar, A.; Pawlig, O.; Trettin, R.

2001-01-01

Proton nuclear magnetic relaxation is a well-established technique for continuous and non destructive monitoring of hydration of conventional Portland building cements. Here, we demonstrate the feasibility of nuclear magnetic resonance (NMR) monitoring of the setting reaction of zinc-phosphate acid-base dental cements, which harden in minutes as compared to days, as in the case of Portland cements. We compare the setting of cement powder (mainly, zinc oxide) prepared with clinically used aluminum-modified orthophosphoric acid solution with the setting of a model system where cement powder is mixed with pure orthophosphoric acid solution. In contrast to previously published NMR studies of setting Portland cements, where a decrease of spin-lattice relaxation time is attributed to enhanced relaxation at the growing internal surface, spin-lattice relaxation time T 1 increases during the set of clinically used zinc-phosphate cement. Comparison of these results with a detailed study of diffusion, viscosity, and magnetic-field dispersion of T 1 in pure and aluminum-modified orthophosphoric acid demonstrates that the increase of T 1 in the setting cement is connected with the increase of molecular mobility in the residual phosphoric acid solution. Although not taken into account so far, such effects may also significantly influence the relaxation times in setting Portland cements, particularly when admixtures with an effect on water viscosity are used. [copyright] 2001 American Institute of Physics

Cemented versus uncemented fixation in total hip replacement: a systematic review and meta-analysis of randomized controlled trials

Directory of Open Access Journals (Sweden)

Ali Abdulkarim

2013-03-01

Full Text Available The optimal method of fixation for primary total hip replacements (THR, particularly fixation with or without the use of cement is still controversial. In a systematic review and metaanalysis of all randomized controlled trials comparing cemented versus uncemented THRS available in the published literature, we found that there is no significant difference between cemented and uncemented THRs in terms of implant survival as measured by the revision rate. Better short-term clinical outcome, particularly an improved pain score can be obtained with cemented fixation. However, the results are unclear for the long-term clinical and functional outcome between the two groups. No difference was evident in the mortality and the post operative complication rate. On the other hand, the radiographic findings were variable and do not seem to correlate with clinical findings as differences in the surgical technique and prosthesis design might be associated with the incidence of osteolysis. We concluded in our review that cemented THR is similar if not superior to uncemented THR, and provides better short term clinical outcomes. Further research, improved methodology and longer follow up are necessary to better define specific subgroups of patients in whom the relative benefits of cemented and uncemented implant fixation can be clearly demonstrated.

Cemented versus uncemented fixation in total hip replacement: a systematic review and meta-analysis of randomized controlled trials.

LENUS (Irish Health Repository)

Abdulkarim, Ali

2013-02-22

The optimal method of fixation for primary total hip replacements (THR), particularly fixation with or without the use of cement is still controversial. In a systematic review and metaanalysis of all randomized controlled trials comparing cemented versus uncemented THRS available in the published literature, we found that there is no significant difference between cemented and uncemented THRs in terms of implant survival as measured by the revision rate. Better short-term clinical outcome, particularly an improved pain score can be obtained with cemented fixation. However, the results are unclear for the long-term clinical and functional outcome between the two groups. No difference was evident in the mortality and the post operative complication rate. On the other hand, the radiographic findings were variable and do not seem to correlate with clinical findings as differences in the surgical technique and prosthesis design might be associated with the incidence of osteolysis. We concluded in our review that cemented THR is similar if not superior to uncemented THR, and provides better short term clinical outcomes. Further research, improved methodology and longer follow up are necessary to better define specific subgroups of patients in whom the relative benefits of cemented and uncemented implant fixation can be clearly demonstrated.

Creep and fatigue behavior of a novel 2-component paste-like formulation of acrylic bone cements.

Science.gov (United States)

Köster, Ulrike; Jaeger, Raimund; Bardts, Mareike; Wahnes, Christian; Büchner, Hubert; Kühn, Klaus-Dieter; Vogt, Sebastian

2013-06-01

The fatigue and creep performance of two novel acrylic bone cement formulations (one bone cement without antibiotics, one with antibiotics) was compared to the performance of clinically used bone cements (Osteopal V, Palacos R, Simplex P, SmartSet GHV, Palacos R+G and CMW1 with Gentamicin). The preparation of the novel bone cement formulations involves the mixing of two paste-like substances in a static mixer integrated into the cartridge which is used to apply the bone cement. The fatigue performance of the two novel bone cement formulations is comparable to the performance of the reference bone cements. The creep compliance of the bone cements is significantly influenced by the effects of physical ageing. The model parameters of Struik's creep law are used to compare the creep behavior of different bone cements. The novel 2-component paste-like bone cement formulations are in the group of bone cements which exhibit a higher creep resistance.

Experimental study with domestic bone cement in the percutaneous vertebroplasty

International Nuclear Information System (INIS)

Ni Caifang; Liu Xisheng; Chen Long; Yang Huilin; Tang Tiansi; Ding Yi

2004-01-01

Objective: To study the feasibility of injecting domestic bone cement in the process of the percutaneous vertebroplasty. Methods: (1) Various types cement were disposed with domestic PMMA. The concretionary phases of cement were observed according to the stages and holding time. Then the most ideal ratio of the mixed cement was selected and ten cement columns were made with this ratio, which was taken as the trial group. The other ten referring to was taken as the contrast one. The biological mechanics was measured with a load and the data of the results were compared. (2) Twenty thoracic and lumbar adjacent bodies were removed intact from five human corpses. These bodies were divided into two groups, in one group PMMA were injected, the other was severed as the contrast one. Then in these twenty vertebral bodies the biological mechanics was measured and the treatment effect was evaluated. (3) In 12 healthy dogs PVP in lumber was tried so as to observe the operational difficulty during the process of injected this bone cement and CT was used to evaluate the result of PMMA, diffusion and the complications caused by it. Results: The most ideal ratio was 4:2.6:1 (g, ml, ml) between powder, monome and contrast. After injecting this kind of cement, the loading strength of these vertebral bodies was increased remarkably (P<0.01). Conclusion: Injecting domestic bone cement provides the theoretical foundations for the clinical application of PVP. (author)

Batako Quality Optimization with Addition of Palm Oil Stem Fiber from Kampar District and Dumai City

Science.gov (United States)

Zainuri; Yanti, Gusneli; Wahyuni Megasari, Shanti

2017-12-01

The waste of dry palm oil produced by 148 trees per hectare is 3,108 ton/month or 37,296 ton/year as calculated. Riau province has oil palm plantations covering an area of 2.399.172 hectares (BPS Riau Province, 2014). It can be estimated the amount of waste generated. Palm stem waste can be utilized, one of which is the utilization of midrib fiber as an added material in the manufacture of batako. Batako- fiber that is made still must be examined feasibility as building materials. The purpose of this study was to determine the optimization of the quality of batako works by the addition of palm stem fiber originated from the districts of Kampar and Dumai. This research used experimental method with laboratory research. Batako-fiber with the addition of palm fiber stem 1% of the weight of cement can increase the value of compressive strength above the normal batako and a batako with first quality according to SNI 03-0349-1989 standard. The use of palm stem fiber originating from the Kampar district resulted in better batakos with higher average compressive strength values than the dumai-derived fibers, especially in the addition of 1% fiber by weight of cement. The finding of this research is that the batakos originating from Kampar district are better than those from Dumai city. The most optimal addition of palm fiber burrs to batako-fiber products is 1% of the weight of cement.

The influence of cement type and temperature on chloride binding in cement paste

DEFF Research Database (Denmark)

Jensen, Ole Mejlhede; Korzen, Migge Sofie Hoffmann; Skibsted, Jørgen

1998-01-01

This paper describes effects of cement type and temperature on chloride binding in cement paste, which is an important subject in relation to life-time modelling of reinforced concrete structures. The influence of cement type on chloride binding is investigated by substituting cement with pure...... cement clinker. Both theoretical considerations and experimental data for chloride binding in cement pastes are presented. A physico-chemically based model to describe the influence of temperature on physical binding of chloride is presented. Solid-state 27Al and 29Si magic-angle spinning (MAS) nuclear...... magnetic resonance (NMR) spectroscopy has been used for quantification of the anhydrous and hydrated aluminate and silicate phases in the chloride exposed cement pastes. The 27Al isotropic chemical shift and nuclear quadrupole coupling is reported for a synthetic sample of Friedel's salt, Ca2Al(OH)6Cl×2H2O....

Clinical performance of stem cell therapy in patients with acute-on-chronic liver failure: a systematic review and meta-analysis.

Science.gov (United States)

Xue, Ran; Meng, Qinghua; Dong, Jinling; Li, Juan; Yao, Qinwei; Zhu, Yueke; Yu, Hongwei

2018-05-10

Stem cell therapy has been applied in the treatment of acute-on-chronic liver failure (ACLF). However, its clinical efficiency is still debatable. The aim of this systematic review and meta-analysis is to evaluate the clinical efficiency of stem cell therapy in the treatment of ACLF. The Cochrane Library, OVID, EMBASE, and PUBMED were searched to December 2017. Both randomized and non-randomized studies, assessing stem cell therapy in patients with ACLF, were included. The outcome measures were total bilirubin (TBIL), alanine transaminase (ALT), international normalized ratio (INR), albumin (ALB), and the model for end-stage liver disease (MELD) score. The quality of evidence was assessed by GRADEpro. Four randomized controlled trials and six non-randomized controlled trials were included. The TBIL levels significantly decreased at 1-, 3-, 12-month after the stem cell therapy (p = 0.0008; p = 0.04; p = 0.007). The ALT levels decreased significantly compared with the control group in the short-term (p stem cell therapy and control groups (p = 0.008). Further subgroup analysis for 3-month clinical performance according to the stem cell types have also been performed. This study suggests that the clinical outcomes of stem cell therapy were satisfied in patients with ACLF in the short-term. MSCs may be better than BM-MNCs in the stem cells transplantation of ACLF. However, more attention should focus on clinical trials in large-volume centers.

Single-visit endodontic treatment of mature teeth with chronic apical abscesses using mineral trioxide aggregate cement: a randomized clinical trial.

Science.gov (United States)

Alsulaimani, Reem Siraj

2016-08-23

Mature teeth with chronic apical abscesses characterized by intermittent discharge of pus through an associated sinus tract. This communication between oral mucosa and periapical inflammation is challenging for the sealing ability of root canal obturation material. Therefore, the study aim was to compare the outcomes of endodontic treatment using mineral trioxide aggregate (MTA) cement to the conventional gutta-percha cone and root canal sealer as an obturation material in mature teeth with chronic apical abscesses. Mature teeth with chronic apical abscesses referred to our clinic for root canal treatment between 2010 and 2012 were treated in a single visit and distributed among treatment (T) and control (C) groups using a predetermined randomization block (TCTC). After chemo-mechanical preparation, teeth in group T received MTA cement mixed in a 0.26 water to powder ratio, and teeth group C received gutta-percha and root canal sealer using the warm vertical technique. The treatment outcomes were defined as obturation length, periapical healing, resorption of extruded material, and survival rate at least 2.5 years after treatment. Three endodontists blinded to the type of obturation material documented treatment outcomes. Statistical analysis at P chronic apical abscesses using MTA cement were better, but not statistically significant, compared to conventional treatment. ISRCTN15285974 . Registered retrospectively 23 June 2015.

Characterization and chemical activity of Portland cement and two experimental cements with potential for use in dentistry.

Science.gov (United States)

Camilleri, J

2008-09-01

To evaluate the chemical activity of Portland cement and two other cement types with similar chemical composition to mineral trioxide aggregate with the aim of developing these cements for further applications in dentistry. The chemical composition of the three cement types namely Portland cement, calcium sulpho-aluminate cement and calcium fluoro-aluminate cement was evaluated by elemental analysis using energy dispersive analysis with X-ray under the scanning electron microscope and by X-ray diffraction analysis (XRD) to determine the phases. The constituents of the hydration reaction by-products were evaluated by XRD analysis of the set cements at 1, 7, 28 and 56 days and by analysis of the leachate by ion chromatography. The pH of both cements and leachate was determined at different time intervals. Cements admixed with micro-silica were also tested to determine the effect of micro-silica on the reaction by-products. All three cement types were composed of tricalcium silicate as the main constituent phase. The hydration reaction of Portland cement produced calcium hydroxide. However, this was not present in the other cements tested at all ages. Admixed micro-silica had little or no effect on the cements with regard to reaction by-products. The pH of all cements tested was alkaline. Both the experimental calcium sulpho-aluminate cement and calcium fluoro-aluminate cement had different hydration reactions to that of Portland cement even though calcium silicate was the major constituent element of both cement types. No calcium hydroxide was produced as a by-product to cement hydration. Micro-silica addition to the cement had no effect on the hydration reaction.

Pulp tissue response to Portland cement associated with different radio pacifying agents on pulpotomy of human primary molars.

Science.gov (United States)

Marques, N; Lourenço Neto, N; Fernandes, A P; Rodini, C; Hungaro Duarte, M; Rios, D; Machado, M A; Oliveira, T

2015-12-01

The objective of this research was to evaluate the response of Portland cement associated with different radio pacifying agents on pulp treatment of human primary teeth by clinical and radiographic exams and microscopic analysis. Thirty mandibular primary molars were randomly divided into the following groups: Group I - Portland cement; Group II - Portland cement with iodoform (Portland cement + CHI3 ); Group III - Portland cement with zirconium oxide (Portland cement + ZrO2 ); and treated by pulpotomy technique (removal of a portion of the pulp aiming to maintain the vitally of the remaining radicular pulp tissue using a therapeutic dressing). Clinical and radiographic evaluations were recorded at 6, 12 and 24 months follow-up. The teeth at the regular exfoliation period were extracted and processed for histological analysis. Data were tested using statistical analysis with a significance level of 5%. The microscopic findings were descriptively analysed. All treated teeth were clinically and radiographically successful at follow-up appointments. The microscopic analysis revealed positive response to pulp repair with hard tissue barrier formation and pulp calcification in the remaining roots of all available teeth. The findings of this study suggest that primary teeth pulp tissue exhibited satisfactory biological response to Portland cement associated with radio pacifying agents. However, further studies with long-term follow-up are needed to determine the safe clinical indication of this alternative material for pulp therapy of primary teeth. © 2015 The Authors Journal of Microscopy © 2015 Royal Microscopical Society.

Design of Fit-for-Purpose Cement to Restore Cement-Caprock Seal Integrity

Science.gov (United States)

Provost, R.

2015-12-01

This project aims to study critical research needs in the area of rock-cement interfaces, with a special focus on crosscutting applications in the Wellbore Integrity Pillar of the SubTER initiative. This study will focus on design and test fit-for-purpose cement formulations. The goals of this project are as follows: 1) perform preliminary study of dispersing nanomaterial admixtures in Ordinary Portland Cement (OPC) mixes, 2) characterize the cement-rock interface, and 3) identify potential high-performance cement additives that can improve sorption behavior, chemical durability, bond strength, and interfacial fracture toughness, as appropriate to specific subsurface operational needs. The work presented here focuses on a study of cement-shale interfaces to better understand failure mechanisms, with particular attention to measuring bond strength at the cement-shale interface. Both experimental testing and computational modeling were conducted to determine the mechanical behavior at the interface representing the interaction of cement and shale of a typical wellbore environment. Cohesive zone elements are used in the finite element method to computationally simulate the interface of the cement and rock materials with varying properties. Understanding the bond strength and mechanical performance of the cement-formation interface is critical to wellbore applications such as sequestration, oil and gas production and exploration and nuclear waste disposal. Improved shear bond strength is an indication of the capability of the interface to ensure zonal isolation and prevent zonal communication, two crucial goals in preserving wellbore integrity. Understanding shear bond strength development and interface mechanics will provide an idea as to how the cement-formation interface can be altered under environmental changes (temperature, pressure, chemical degradation, etc.) so that the previously described objectives can be achieved. Sandia National Laboratories is a multi

Recent technological updates and clinical applications of induced pluripotent stem cells.

Science.gov (United States)

Diecke, Sebastian; Jung, Seung Min; Lee, Jaecheol; Ju, Ji Hyeon

2014-09-01

Induced pluripotent stem cells (iPSCs) were first described in 2006 and have since emerged as a promising cell source for clinical applications. The rapid progression in iPSC technology is still ongoing and directed toward increasing the efficacy of iPSC production and reducing the immunogenic and tumorigenic potential of these cells. Enormous efforts have been made to apply iPSC-based technology in the clinic, for drug screening approaches and cell replacement therapy. Moreover, disease modeling using patient-specific iPSCs continues to expand our knowledge regarding the pathophysiology and prospective treatment of rare disorders. Furthermore, autologous stem cell therapy with patient-specific iPSCs shows great propensity for the minimization of immune reactions and the provision of a limitless supply of cells for transplantation. In this review, we discuss the recent updates in iPSC technology and the use of iPSCs in disease modeling and regenerative medicine.

Early subsidence of shape-closed hip arthroplasty stems is associated with late revision. A systematic review and meta-analysis of 24 RSA studies and 56 survival studies.

Science.gov (United States)

van der Voort, Paul; Pijls, Bart G; Nieuwenhuijse, Marc J; Jasper, Jorrit; Fiocco, Marta; Plevier, Josepha W M; Middeldorp, Saskia; Valstar, Edward R; Nelissen, Rob G H H

2015-01-01

Few studies have addressed the association between early migration of femoral stems and late aseptic revision in total hip arthroplasty. We performed a meta-regression analysis on 2 parallel systematic reviews and meta-analyses to determine the association between early migration and late aseptic revision of femoral stems. Of the 2 reviews, one covered early migration data obtained from radiostereometric analysis (RSA) studies and the other covered long-term aseptic revision rates obtained from survival studies with endpoint revision for aseptic loosening. Stems were stratified according to the design concept: cemented shape-closed, cemented force-closed, and uncemented. A weighted regression model was used to assess the association between early migration and late aseptic revision, and to correct for confounders. Thresholds for acceptable and unacceptable migration were determined in accordance with the national joint registries (≤ 5% revision at 10 years) and the NICE criteria (≤ 10% revision at 10 years). 24 studies (731 stems) were included in the RSA review and 56 studies (20,599 stems) were included in the survival analysis review. Combining both reviews for the 3 design concepts showed that for every 0.1-mm increase in 2-year subsidence, as measured with RSA, there was a 4% increase in revision rate for the shape-closed stem designs. This association remained after correction for age, sex, diagnosis, hospital type, continent, and study quality. The threshold for acceptable migration of shape-closed designs was defined at 0.15 mm; stems subsiding less than 0.15 mm in 2 years had revision rates of less than 5% at 10 years, while stems exceeding 0.15 mm subsidence had revision rates of more than 5%. There was a clinically relevant association between early subsidence of shape-closed femoral stems and late revision for aseptic loosening. This association can be used to assess the safety of shape-closed stem designs. The published research is not sufficient

Exploiting science? A systematic analysis of complementary and alternative medicine clinic websites' marketing of stem cell therapies.

Science.gov (United States)

Murdoch, Blake; Zarzeczny, Amy; Caulfield, Timothy

2018-02-28

To identify the frequency and qualitative characteristics of stem cell-related marketing claims made on websites of clinics featuring common types of complementary and alternative medicine practitioners. The involvement of complementary and alternative medicine practitioners in the marketing of stem cell therapies and stem cell-related interventions is understudied. This research explores the extent to which they are involved and collaborate with medical professionals. This knowledge will help with identifying and evaluating potential policy responses to this growing market. Systematic website analysis. Global. US and English-language bias due to methodology. Representations made on clinic websites in relation to practitioner types, stem cell therapies and their targets, stem cell-related interventions. Statements about stem cell therapies relating to evidence of inefficacy, limited evidence of efficacy, general procedural risks, risks specific to the mode of therapy, regulatory status, experimental or unproven nature of therapy. Use of hype language (eg, language that exaggerates potential benefits). 243 websites offered stem cell therapies. Many websites advertised stem cell transplantation from multiple sources, such as adipose-derived (112), bone marrow-derived (100), blood-derived (28), umbilical cord-derived (26) and others. Plant stem cell-based treatments and products (20) were also advertised. Purposes for and targets of treatment included pain, physical injury, a wide range of diseases and illnesses, cosmetic concerns, non-cosmetic ageing, sexual enhancement and others. Medical doctors (130), chiropractors (53) and naturopaths (44) commonly work in the clinics we found to be offering stem cell therapies. Few clinic websites advertising stem cell therapies included important additional information, including statements about evidence of inefficacy (present on only 12.76% of websites), statements about limited evidence of efficacy (18.93%), statements of

Porous surface modified bioactive bone cement for enhanced bone bonding.

Directory of Open Access Journals (Sweden)

Qiang He

Full Text Available Polymethylmethacrylate bone cement cannot provide an adhesive chemical bonding to form a stable cement-bone interface. Bioactive bone cements show bone bonding ability, but their clinical application is limited because bone resorption is observed after implantation. Porous polymethylmethacrylate can be achieved with the addition of carboxymethylcellulose, alginate and gelatin microparticles to promote bone ingrowth, but the mechanical properties are too low to be used in orthopedic applications. Bone ingrowth into cement could decrease the possibility of bone resorption and promote the formation of a stable interface. However, scarce literature is reported on bioactive bone cements that allow bone ingrowth. In this paper, we reported a porous surface modified bioactive bone cement with desired mechanical properties, which could allow for bone ingrowth.The porous surface modified bioactive bone cement was evaluated to determine its handling characteristics, mechanical properties and behavior in a simulated body fluid. The in vitro cellular responses of the samples were also investigated in terms of cell attachment, proliferation, and osteoblastic differentiation. Furthermore, bone ingrowth was examined in a rabbit femoral condyle defect model by using micro-CT imaging and histological analysis. The strength of the implant-bone interface was also investigated by push-out tests.The modified bone cement with a low content of bioactive fillers resulted in proper handling characteristics and adequate mechanical properties, but slightly affected its bioactivity. Moreover, the degree of attachment, proliferation and osteogenic differentiation of preosteoblast cells was also increased. The results of the push-out test revealed that higher interfacial bonding strength was achieved with the modified bone cement because of the formation of the apatite layer and the osseointegration after implantation in the bony defect.Our findings suggested a new bioactive

Effects of cement particle size distribution on performance properties of Portland cement-based materials

Energy Technology Data Exchange (ETDEWEB)

Bentz, D.P.; Garboczi, E.J.; Haecker, C.J.; Jensen, O.M.

1999-10-01

The original size, spatial distribution, and composition of Portland cement particles have a large influence on hydration kinetics, microstructure development, and ultimate properties of cement-based materials. In this paper, the effects of cement particle size distribution on a variety of performance properties are explored via computer simulation and a few experimental studies. Properties examined include setting time, heat release, capillary porosity percolation, diffusivity, chemical shrinkage, autogenous shrinkage, internal relative humidity evolution, and interfacial transition zone microstructure. The effects of flocculation and dispersion of the cement particles in the starting microstructures on resultant properties are also briefly evaluated. The computer simulations are conducted using two cement particle size distributions that bound those commonly in use today and three different water-to-cement ratios: 0.5, 0.3, and 0.246. For lower water-to-cement ratio systems, the use of coarser cements may offer equivalent or superior performance, as well as reducing production costs for the manufacturer.

Seating load parameters impact on dental ceramic reinforcement conferred by cementation with resin-cements.

LENUS (Irish Health Repository)

Addison, Owen

2010-09-01

Cementation of all-ceramic restorations with resin-cements has been demonstrated to reduce the incidence of fracture in service. The aim was to investigate the influence of loading force and loading duration applied during cementation on the reinforcement conferred by a resin-cement on a leucite reinforced glass-ceramic.

[Dislocated fracture of the lesser trochanter with malrotation of the stem after robot assisted implantation of a cementless hip prosthesis: a casuistic report].

Science.gov (United States)

Prymka, M; Hassenpflug, J

2003-08-01

This paper presents the case of a 63 year old female with a severe coxarthrosis. She got a robot assited implantation of a cementless hip prosthesis (Osteolock, Stryker-Howmedica, Mühlheim). As operation robot the CASPAR-System (Orto-Maquet, Rastatt) was used. Initially, the clinical progress of the patient was fine. She was nearly painfree within 14 days and showed an acceptable range of motion in the operated joint (flexion/ extension 90 degrees /05 degrees /00 degrees ). She was mobilized with crutches and 15 kg weight bearing at the operated leg. 3 weeks postoperative the patient complaint about increasing pain without trauma or intensification of the weight bearing. X-rays showed not only a dislocated fracture of the lesser trochanter, but also a sinking combined with a malrotation of the stem. A revision operation was necessary,where we implanted a cemented stem. Now clinical progress was completely satisfying.

A clinical trial to evaluate the retention of a silver cermet-ionomer cement used as a fissure sealant.

Science.gov (United States)

Mills, R W; Ball, I A

1993-01-01

A randomized clinical trial was under-taken to compare the retention of a silver cermet-ionomer cement, Ketac Silver, with a conventional, autopolymerizing BIS-GMA resin sealant, Delton, using matched pairs of fissure sites within each subject's mouth. One hundred twenty matched contralateral pairs of fissure sites in first and second permanent molars of 53 school children were sealed with the two materials. The choice of site and material was selected at random. The ages of the children ranged from five to 16 years; first permanent molars were sealed in the five- to 10-year age group, and second permanent molars in the 11- to 16-year age group. Sealants were assessed as present, partly present, or absent at 6, 12, and 24 months. The number of pairs of sites available for reassessment declined from 102 at six months to 59 at 24 months as patients were lost to the study. Retention rates were higher for the Ketac Silver sealants at all three inspection intervals (P cermet cement was better retained than conventional resin sealants in younger children.

Determining the water-cement ratio, cement content, water content and degree of hydration of hardened cement paste: Method development and validation on paste samples

International Nuclear Information System (INIS)

Wong, H.S.; Buenfeld, N.R.

2009-01-01

We propose a new method to estimate the initial cement content, water content and free water/cement ratio (w/c) of hardened cement-based materials made with Portland cements that have unknown mixture proportions and degree of hydration. This method first quantifies the composition of the hardened cement paste, i.e. the volumetric fractions of capillary pores, hydration products and unreacted cement, using high-resolution field emission scanning electron microscopy (FE-SEM) in the backscattered electron (BSE) mode and image analysis. From the obtained data and the volumetric increase of solids during cement hydration, we compute the initial free water content and cement content, hence the free w/c ratio. The same method can also be used to calculate the degree of hydration. The proposed method has the advantage that it is quantitative and does not require comparison with calibration graphs or reference samples made with the same materials and cured to the same degree of hydration as the tested sample. This paper reports the development, assumptions and limitations of the proposed method, and preliminary results from Portland cement pastes with a range of w/c ratios (0.25-0.50) and curing ages (3-90 days). We also discuss the extension of the technique to mortars and concretes, and samples made with blended cements.

Stability of reinforced cemented backfills

International Nuclear Information System (INIS)

Mitchell, R.J.; Stone, D.M.

1987-01-01

Mining with backfill has been the subject of several international meetings in recent years and a considerable research effort is being applied to improve both mining economics and ore recovery by using backfill for ground support. Classified mill tailings sands are the most commonly used backfill material but these fine sands must be stabilized before full ore pillar recovery can be achieved. Normal portland cement is generally used for stabilization but the high cost of cement prohibits high cement usage. This paper considers the use of reinforcements in cemented fill to reduce the cement usage. It is concluded that strong cemented layers at typical spacings of about 3 meters in a low cement content bulk fill can reinforce the fill and reduce the overall cement usage. Fibre reinforcements introduced into strong layers or into bulk fills are also known to be effective in reducing cement usage. Some development work is needed to produce the ideal type of anchored fibre in order to realize economic gains from fibre-reinforced fills

Microscale Investigation of Arsenic Distribution and Species in Cement Product from Cement Kiln Coprocessing Wastes

Directory of Open Access Journals (Sweden)

Yufei Yang

2013-01-01

Full Text Available To improve the understanding of the immobilization mechanism and the leaching risk of Arsenic (As in the cement product from coprocessing wastes using cement kiln, distribution and species of As in cement product were determined by microscale investigation methods, including electron probe microanalysis (EPMA and X-ray absorption spectroscopy. In this study, sodium arsenate crystals (Na3AsO412H2O were mixed with cement production raw materials and calcined to produce cement clinker. Then, clinker was mixed water to prepare cement paste. EPMA results showed that As was generally distributed throughout the cement paste. As content in calcium silicate hydrates gel (C-S-H was in low level, but higher than that in other cement mineral phases. This means that most of As is expected to form some compounds that disperse on the surfaces of cement mineral phases. Linear combination fitting (LCF of the X-ray absorption near edge structure spectra revealed that As in the cement paste was predominantly As(V and mainly existed as Mg3(AsO42, Ca3(AsO42, and Na2HAsO4.

Evaluation of cement thixotropy for the cement of oil wells in areas ...

African Journals Online (AJOL)

... economical for cementing job operations in wells with loss zones. The results also show that the effect of LHF is positive, since in addition to his contribution to long term performances, especially the durability of hardened concrete, it improves the thixotropy of cement made of plaster. Keywords: cementing; lost circulation; ...

The Challenges of First-in-Human Stem Cell Clinical Trials: What Does This Mean for Ethics and Institutional Review Boards?

Directory of Open Access Journals (Sweden)

Roger A. Barker

2018-05-01

Full Text Available Stem cell-based clinical interventions are increasingly advancing through preclinical testing and approaching clinical trials. The complexity and diversity of these approaches, and the confusion created by unproven and untested stem cell-based “therapies,” create a growing need for a more comprehensive review of these early-stage human trials to ensure they place the patients at minimal risk of adverse events but are also based on solid evidence of preclinical efficacy with a clear scientific rationale for that effect. To address this issue and supplement the independent review process, especially that of the ethics and institutional review boards who may not be experts in stem cell biology, the International Society for Stem Cell Research (ISSCR has developed a set of practical questions to cover the major issues for which clear evidence-based answers need to be obtained before approving a stem cell-based trial. Keywords: human stem cell-derived interventions, early phase clinical trials, institutional review and ethics boards, review process, guidelines

The differences between soil grouting with cement slurry and cement-water glass slurry

Science.gov (United States)

Zhu, Mingting; Sui, Haitong; Yang, Honglu

2018-01-01

Cement slurry and cement-water glass slurry are the most widely applied for soil grouting reinforcement project. The viscosity change of cement slurry is negligible during grouting period and presumed to be time-independent while the viscosity of cement-water glass slurry increases with time quickly and is presumed to be time-dependent. Due to the significantly rheology differences between them, the grouting quality and the increasing characteristics of grouting parameters may be different, such as grouting pressure, grouting surrounding rock pressure, i.e., the change of surrounding rock pressure deduced by grouting pressure. Those are main factors for grouting design. In this paper, a large-scale 3D grouting simulation device was developed to simulate the surrounding curtain grouting for a tunnel. Two series of surrounding curtain grouting experiments under different geo-stress of 100 kPa, 150 kPa and 200 kPa were performed. The overload test on tunnel was performed to evaluate grouting effect of all surrounding curtain grouting experiments. In the present results, before 240 seconds, the grouting pressure increases slowly for both slurries; after 240 seconds the increase rate of grouting pressure for cement-water glass slurry increases quickly while that for cement slurry remains roughly constant. The increasing trend of grouting pressure for cement-water glass is similar to its viscosity. The setting time of cement-water glass slurry obtained from laboratory test is less than that in practical grouting where grout slurry solidifies in soil. The grouting effect of cement-water glass slurry is better than that of cement slurry and the grouting quality decreases with initial pressure.

Improvement of in vitro physicochemical properties and osteogenic activity of calcium sulfate cement for bone repair by dicalcium silicate

International Nuclear Information System (INIS)

Chen, Chun-Cheng; Wang, Chien-Wen; Hsueh, Nai-Shuo; Ding, Shinn-Jyh

2014-01-01

Highlights: • Dicalcium silicate can improve osteogenic activity of calcium sulfate cement. • The higher the calcium sulfate content, the shorter the setting time in the composite cement. • The results were useful for designing calcium-based cement with optimal properties. -- Abstract: An ideal bone graft substitute should have the same speed of degradation as formation of new bone tissue. To improve the properties of calcium sulfate hemihydrate (CSH) featured for its rapid resorption, a low degradation material of dicalcium silicate (DCS) was added to the CSH cement. This study examined the effect of DCS (20, 40, 60 and 80 wt%) on the in vitro physicochemical properties and osteogenic activities of the calcium-based composite cements. The diametral tensile strength, porosity and weight loss of the composite cements were evaluated before and after soaking in a simulated body fluid (SBF). The osteogenic activities, such as proliferation, differentiation and mineralization, of human mesenchymal stem cells (hMSCs) seeded on cement surfaces were also examined. As a result, the greater the DCS amount, the higher the setting time was in the cement. Before soaking in SBF, the diametral tensile strength of the composite cements was decreased due to the introduction of DCS. On 180-day soaking, the composite cements containing 20, 40, 60 and 80 wt% DCS lost 80%, 69%, 61% and 44% in strength, respectively. Regarding in vitro bioactivity, the DCS-rich cements were covered with clusters of apatite spherulites after soaking for 7 days, while there was no formation of apatite spherulites on the CSH-rich cement surfaces. The presence of DCS could reduce the degradation of the CSH cements, as evidenced in the results of weight loss and porosity. More importantly, DCS may promote effectively the cell proliferation, proliferation and mineralization. The combination of osteogenesis of DCS and degradation of CSH made the calcium-based composite cements an attractive choice for

Heat of hydration measurements on cemented radioactive wastes. Part 1: cement-water pastes

International Nuclear Information System (INIS)

Lee, D.J.

1983-12-01

This report describes the hydration of cement pastes in terms of chemical and kinetic models. A calorimetric technique was used to measure the heat of hydration to develop these models. The effects of temperature, water/cement ratio and cement replacements, ground granulated blast furnace slag (BFS) and pulverised fuel ash (PFA) on the hydration of ordinary Portland cement (OPC) is reported. The incorporation of BFS or PFA has a marked effect on the hydration reaction. The effect of temperature is also important but changing the water/cement ratio has little effect. Results from cement pastes containing only water and cement yield total heats of reaction of 400, 200 and 100 kJ/kg for OPC, BFS and PFA respectively. Using the results from the models which have been developed, the effect of major salts present in radioactive waste streams can be assessed. Values of the total heat of reaction, the time to complete 50 percent reaction, and the energy of activation, can be compared for different waste systems. (U.K.)

Sulfur polymer cement concrete

International Nuclear Information System (INIS)

Weber, H.H.; McBee, W.C.

1990-01-01

Sulfur-based composite materials formulated using sulfur polymer cement (SPC) and mineral aggregates are described and compared with conventional portland cement based materials. Materials characteristics presented include mechanical strength, chemical resistance, impact resistance, moisture permeation, and linear shrinkage during placement and curing. Examples of preparation and placement of sulfur polymer cement concrete (SC) are described using commercial scale equipment. SC applications presented are focused into hostile chemical environments where severe portland cement concrete (PCC) failure has occurred

Sustainable Development of the Cement Industry and Blended Cements to Meet Ecological Challenges

OpenAIRE

Sobolev, Konstantin

2003-01-01

The world production of cement has greatly increased in the past 10 years. This trend is the most significant factor affecting technological development and the updating of manufacturing facilities in the cement industry. Existing technology for the production of cement clinker is ecologically damaging; it consumes much energy and natural resources and also emits pollutants. A new approach to the production of blended or high-volume mineral additive (HVMA) cement helps to improve its ecologi...

Assessment of bone healing ability of calcium phosphate cements loaded with platelet lysate in rat calvarial defects.

Science.gov (United States)

Babo, Pedro S; Carvalho, Pedro P; Santo, Vítor E; Faria, Susana; Gomes, Manuela E; Reis, Rui L

2016-11-01

Injectable calcium phosphate cements have been used as a valid alternative to autologous bone grafts for bone augmentation with the additional advantage of enabling minimally invasive implantation procedures and for perfectly fitting the tissue defect. Nevertheless, they have low biodegradability and lack adequate biochemical signaling to promote bone healing and remodeling. In previous in vitro studies, we observed that the incorporation of platelet lysate directly into the cement paste or loaded in hyaluronic acid microspheres allowed to modulate the cement degradation and the in vitro expression of osteogenic markers in seeded human adipose derived stem cells. The present study aimed at investigating the possible effect of this system in new bone formation when implanted in calvarial bilateral defects in rats. Different formulations were assessed, namely plain calcium phosphate cements, calcium phosphate cements loaded with human platelet lysate, hybrid injectable formulations composed of the calcium phosphate cement incorporating hyaluronin acid non-loaded microparticles (20% hyaluronin acid) or with particles loaded with platelet lysate. The degradability and new bone regrowth were evaluated in terms of mineral volume in the defect, measured by micro-computed tomography and histomorphometric analysis upon 4, 8 and 12 weeks of implantation. We observed that the incorporation of hyaluronin acid microspheres induced an overly rapid cement degradation, impairing the osteoconductive properties of the cement composites. Moreover, the incorporation of platelet lysate induced higher bone healing than the materials without platelet lysate, up to four weeks after surgery. Nevertheless, this effect was not found to be significant when compared to the one observed in the sham-treated group. © The Author(s) 2016.

Evaluation of four biodegradable, injectable bone cements in an experimental drill hole model in sheep.

Science.gov (United States)

von Rechenberg, Brigitte; Génot, Oliver R; Nuss, Katja; Galuppo, Larry; Fulmer, Mark; Jacobson, Evan; Kronen, Peter; Zlinszky, Kati; Auer, Jörg A

2013-09-01

Four cement applications were tested in this investigation. Two dicalcium phosphate dihydrate (DCPD-brushite) hydraulic cements, an apatite hydraulic fiber loaded cement, and a calcium sulfate cement (Plaster of Paris) were implanted in epiphyseal and metaphyseal cylindrical bone defects in sheep. The in vivo study was performed to assess the biocompatibility and bone remodeling of four cement formulations. After time periods of 2, 4, and 6 months, the cement samples were clinically and histologically evaluated. Histomorphometrically, the amount of new bone formation, fibrous tissue, and bone marrow and the area of remaining cement were measured. In all specimens, no signs of inflammation were detectable either macroscopically or microscopically. Cements differed mainly in their resorption time. Calcium sulfate was already completely resorbed at 2 months and showed a variable amount of new bone formation and/or fibrous tissue in the original drill hole over all time periods. The two DCPD cements in contrast were degraded to a large amount at 6 months, whereas the apatite was almost unchanged over all time periods. Copyright © 2013. Published by Elsevier B.V.

Experimental Study on Artificial Cemented Sand Prepared with Ordinary Portland Cement with Different Contents

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Dongliang Li

2015-07-01

Full Text Available Artificial cemented sand test samples were prepared by using ordinary Portland cement (OPC as the cementing agent. Through uniaxial compression tests and consolidated drained triaxial compression tests, the stress-strain curves of the artificial cemented sand with different cementing agent contents (0.01, 0.03, 0.05 and 0.08 under various confining pressures (0.00 MPa, 0.25 MPa, 0.50 MPa and 1.00 MPa were obtained. Based on the test results, the effect of the cementing agent content (Cv on the physical and mechanical properties of the artificial cemented sand were analyzed and the Mohr-Coulomb strength theory was modified by using Cv. The research reveals that when Cv is high (e.g., Cv = 0.03, 0.05 or 0.08, the stress-strain curves of the samples indicate a strain softening behavior; under the same confining pressure, as Cv increases, both the peak strength and residual strength of the samples show a significant increase. When Cv is low (e.g., Cv = 0.01, the stress-strain curves of the samples indicate strain hardening behavior. From the test data, a function of Cv (the cementing agent content with c′ (the cohesion force of the sample and Δϕ′ (the increment of the angle of shearing resistance is obtained. Furthermore, through modification of the Mohr-Coulomb strength theory, the effect of cementing agent content on the strength of the cemented sand is demonstrated.

Experimental Study on Artificial Cemented Sand Prepared with Ordinary Portland Cement with Different Contents.

Science.gov (United States)

Li, Dongliang; Liu, Xinrong; Liu, Xianshan

2015-07-02

Artificial cemented sand test samples were prepared by using ordinary Portland cement (OPC) as the cementing agent. Through uniaxial compression tests and consolidated drained triaxial compression tests, the stress-strain curves of the artificial cemented sand with different cementing agent contents (0.01, 0.03, 0.05 and 0.08) under various confining pressures (0.00 MPa, 0.25 MPa, 0.50 MPa and 1.00 MPa) were obtained. Based on the test results, the effect of the cementing agent content ( C v ) on the physical and mechanical properties of the artificial cemented sand were analyzed and the Mohr-Coulomb strength theory was modified by using C v . The research reveals that when C v is high (e.g., C v = 0.03, 0.05 or 0.08), the stress-strain curves of the samples indicate a strain softening behavior; under the same confining pressure, as C v increases, both the peak strength and residual strength of the samples show a significant increase. When C v is low (e.g., C v = 0.01), the stress-strain curves of the samples indicate strain hardening behavior. From the test data, a function of C v (the cementing agent content) with c ' (the cohesion force of the sample) and Δϕ' (the increment of the angle of shearing resistance) is obtained. Furthermore, through modification of the Mohr-Coulomb strength theory, the effect of cementing agent content on the strength of the cemented sand is demonstrated.

Influence of Cements Containing Calcareous Fly Ash as a Main Component Properties of Fresh Cement Mixtures

Science.gov (United States)

Gołaszewski, Jacek; Kostrzanowska-Siedlarz, Aleksandra; Ponikiewski, Tomasz; Miera, Patrycja

2017-10-01

The main goal of presented research was to examine usability of cements containing calcareous fly ash (W) from technological point of view. In the paper the results of tests concerning the influence of CEM II and CEM IV cements containing fly ash (W) on rheological properties, air content, setting times and plastic shrinkage of mortars are presented and discussed. Moreover, compatibility of plasticizers with cements containing fly ash (W) was also studied. Additionally, setting time and hydration heat of cements containing calcareous fly ash (W) were determined. In a broader aspect, the research contributes to promulgation of the possibility of using calcareous fly ash (W) in cement and concrete technology, what greatly benefits the environment protection (utilization of waste fly ash). Calcareous fly ash can be used successfully as the main component of cement. Cements produced by blending with processed fly ash or cements produced by interginding are characterized by acceptable technological properties. In respect to CEM I cements, cements containing calcareous fly ash worsen workability, decrease air content, delay setting time of mixtures. Cements with calcareous fly ash show good compatibility with plasticizers.

Feasibility of mesenchymal stem cell culture expansion for a phase I clinical trial in multiple sclerosis.

Science.gov (United States)

Planchon, Sarah M; Lingas, Karen T; Reese Koç, Jane; Hooper, Brittney M; Maitra, Basabi; Fox, Robert M; Imrey, Peter B; Drake, Kylie M; Aldred, Micheala A; Lazarus, Hillard M; Cohen, Jeffrey A

2018-01-01

Multiple sclerosis is an inflammatory, neurodegenerative disease of the central nervous system for which therapeutic mesenchymal stem cell transplantation is under study. Published experience of culture-expanding multiple sclerosis patients' mesenchymal stem cells for clinical trials is limited. To determine the feasibility of culture-expanding multiple sclerosis patients' mesenchymal stem cells for clinical use. In a phase I trial, autologous, bone marrow-derived mesenchymal stem cells were isolated from 25 trial participants with multiple sclerosis and eight matched controls, and culture-expanded to a target single dose of 1-2 × 10 6 cells/kg. Viability, cell product identity and sterility were assessed prior to infusion. Cytogenetic stability was assessed by single nucleotide polymorphism analysis of mesenchymal stem cells from 18 multiple sclerosis patients and five controls. One patient failed screening. Mesenchymal stem cell culture expansion was successful for 24 of 25 multiple sclerosis patients and six of eight controls. The target dose was achieved in 16-62 days, requiring two to three cell passages. Growth rate and culture success did not correlate with demographic or multiple sclerosis disease characteristics. Cytogenetic studies identified changes on one chromosome of one control (4.3%) after extended time in culture. Culture expansion of mesenchymal stem cells from multiple sclerosis patients as donors is feasible. However, culture time should be minimized for cell products designated for therapeutic administration.

Comparison between three glass fiber post cementation techniques.

Science.gov (United States)

Migliau, Guido; Piccoli, Luca; Di Carlo, Stefano; Pompa, Giorgio; Besharat, Laith Konstantinos; Dolci, Marco

2017-01-01

The aim of this experimental study was to compare the traditional cement systems with those of the latest generation, to assess if indeed these could represent of viable substitutes in the cementation of indirect restorations, and in the specific case of endodontic posts. The assessment of the validity of the cementing methods was performed according to the test of the push-out, conducted on sections obtained from the roots of treated teeth. The samples were divided into three groups. Group A (10 samples): etching for 30 seconds with 37% orthophosphoric acid (Superlux-Thixo-etch-DMG) combined with a dual-curing adhesive system (LuxaBond-Total Etch-DMG), dual-cured resin-composite cement (LuxaCore-DMG) and glass fiber posts (LuxaPost-DMG). Group B (10 samples): self-adhesive resin cement (Breeze-Pentron Clinical) and glass fiber posts (LuxaPost-DMG). Group C (10 samples): 3 steps light-curing, self-etching, self-conditioning bonding agent (Contax-Total-etch-DMG), dual-cured resin-composite cement (LuxaCore-DMG) and glass fiber posts (LuxaPost-DMG). The survey was conducted by examining the breaking resistance of the post-cement-tooth complex, subjected to a mechanical force. Statistical analysis was performed using SPSS Inc. ver. 13.0, Chicago, IL, USA. Group A values of bond strenth ranged from a minimum of 10.14 Mpa to a maximum value of 14.73 Mpa with a mean value of 12.58 Mpa. In Group B the highest value of bond strength was 6.54 Mpa and the minimum 5.55 Mpa. The mean value of the bond strength for the entire group was 6.58 Mpa. In Group C the highest bond strength was 6.59 Mpa whereas the lowest bond strength was 4.84 Mpa. Mean value of the bond strength of Group C was calculated at 5.7 Mpa. Etching with orthophosphoric acid combined with a dual-curing adhesive system and a dual-cured resin-composite cement was the technique that guaranteed the highest bond strength. Lowest bond strength values were obtained when dual self-adhesive cement was used.

Development of high-performance blended cements

Science.gov (United States)

Wu, Zichao

2000-10-01

This thesis presents the development of high-performance blended cements from industrial by-products. To overcome the low-early strength of blended cements, several chemicals were studied as the activators for cement hydration. Sodium sulfate was discovered as the best activator. The blending proportions were optimized by Taguchi experimental design. The optimized blended cements containing up to 80% fly ash performed better than Type I cement in strength development and durability. Maintaining a constant cement content, concrete produced from the optimized blended cements had equal or higher strength and higher durability than that produced from Type I cement alone. The key for the activation mechanism was the reaction between added SO4 2- and Ca2+ dissolved from cement hydration products.

Cements in Radioactive Waste Disposal

International Nuclear Information System (INIS)

Glasser, F.P.

2013-01-01

The use of cement and concrete to immobilise radioactive waste is complicated by the wide- ranging nature of inorganic cementing agents available as well as the range of service environments in which cement is used and the different functions expected of cement. For example, Portland cement based concretes are widely used as structural materials for construction of vaults and tunnels. These constructions may experience a long pre-closure performance lifetime during which they are required to protect against collapse and ingress of water: strength and impermeability are key desirable characteristics. On the other hand, cement and concrete may be used to form backfills, ranging in permeability. Permeable formulations allow gas readily to escape, while impermeable barriers retard radionuclide transport and reduce access of ground water to the waste. A key feature of cements is that, while fresh, they pass through a fluid phase and can be formed into any shape desired or used to infiltrate other materials thereby enclosing them into a sealed matrix. Thereafter, setting and hardening is automatic and irreversible. Where concrete is used to form structural elements, it is also natural to use cement in other applications as it minimises potential for materials incompatibility. Thus cement- mainly Portland cement- has been widely used as an encapsulant for storage, transport and as a radiation shield for active wastes. Also, to form and stabilise structures such as vaults and silos. Relative to other potential matrices, cement also has a chemical immobilisation potential, reacting with and binding with many radionuclides. The chemical potential of cements is essentially sacrificial, thus limiting their performance lifetime. However performance may also be required in the civil engineering sense, where strength is important, so many factors, including a geochemical description of service conditions, may require to be assessed in order to predict performance lifetime. The

Cements in Radioactive Waste Disposal

Energy Technology Data Exchange (ETDEWEB)

Glasser, F. P. [University of Aberdeen, Scotland (United Kingdom)

2013-09-15

The use of cement and concrete to immobilise radioactive waste is complicated by the wide- ranging nature of inorganic cementing agents available as well as the range of service environments in which cement is used and the different functions expected of cement. For example, Portland cement based concretes are widely used as structural materials for construction of vaults and tunnels. These constructions may experience a long pre-closure performance lifetime during which they are required to protect against collapse and ingress of water: strength and impermeability are key desirable characteristics. On the other hand, cement and concrete may be used to form backfills, ranging in permeability. Permeable formulations allow gas readily to escape, while impermeable barriers retard radionuclide transport and reduce access of ground water to the waste. A key feature of cements is that, while fresh, they pass through a fluid phase and can be formed into any shape desired or used to infiltrate other materials thereby enclosing them into a sealed matrix. Thereafter, setting and hardening is automatic and irreversible. Where concrete is used to form structural elements, it is also natural to use cement in other applications as it minimises potential for materials incompatibility. Thus cement- mainly Portland cement- has been widely used as an encapsulant for storage, transport and as a radiation shield for active wastes. Also, to form and stabilise structures such as vaults and silos. Relative to other potential matrices, cement also has a chemical immobilisation potential, reacting with and binding with many radionuclides. The chemical potential of cements is essentially sacrificial, thus limiting their performance lifetime. However performance may also be required in the civil engineering sense, where strength is important, so many factors, including a geochemical description of service conditions, may require to be assessed in order to predict performance lifetime. The

Per-operative vibration analysis: a valuable tool for defining correct stem insertion: preliminary report.

Science.gov (United States)

Mulier, Michiel; Pastrav, Cesar; Van der Perre, Georges

2008-01-01

Defining the stem insertion end point during total hip replacement still relies on the surgeon's feeling. When a custom-made stem prosthesis with an optimal fit into the femoral canal is used, the risk of per-operative fractures is even greater than with standard prostheses. Vibration analysis is used in other clinical settings and has been tested as a means to detect optimal stem insertion in the laboratory. The first per-operative use of vibration analysis during non-cemented custom-made stem insertion in 30 patients is reported here. Thirty patients eligible for total hip replacement with uncemented stem prosthesis were included. The neck of the stem was connected with a shaker that emitted white noise as excitation signal and an impedance head that measured the frequency response. The response signal was sent to a computer that analyzed the frequency response function after each insertion phase. A technician present in the operating theatre but outside the laminated airflow provided feed-back to the surgeon. The correlation index between the frequency response function measured during the last two insertion hammering sessions was >0.99 in 86.7% of the cases. In four cases the surgeon stopped the insertion procedure because of a perceived risk of fracture. Two special cases illustrating the potential benefit of per-operative vibration analysis are described. The results of intra-operative vibration analysis indicate that this technique may be a useful tool assisting the orthopaedic surgeon in defining the insertion endpoint of the stem. The development of a more user-friendly device is therefore warranted.

Root perforations treatment using mineral trioxide aggregate and Portland cements.

Science.gov (United States)

Silva Neto, José Dias da; Brito, Rafael Horácio de; Schnaider, Taylor Brandão; Gragnani, Alfredo; Engelman, Mírian; Ferreira, Lydia Masako

2010-12-01

Clinical, radiological and histological evaluation of root perforations treated with mineral trioxide aggregate (MTA) or Portland cements, and calcium sulfate barrier. One molar and 11 premolar teeth of a male mongrel dog received endodontic treatment and furcations were perforated with a high-speed round bur and treated with a calcium sulfate barrier. MTA, Portland cement type II (PCII) and type V (PCV), and white Portland cement (WPC) were used as obturation materials. The teeth were restored with composite resin and periapical radiographs were taken. The animal was euthanized 120 days post-surgery for treatment evaluation. Right lower first premolar (MTA), right lower third premolar (PCV), left lower second premolar (MTA), and right lower second premolar (WPC): clinically normal, slightly radio-transparent area on the furcation, little inflammatory infiltrate, and new-bone formation. Left lower third premolar (PCII), right upper first premolar (WPC), right upper third premolar (PCII), and left upper first molar (PCV): clinically normal, radiopaque area on the furcation, and new-bone formation. Right upper second premolar (MTA), left upper second premolar (WPC), left upper third premolar (PCII): presence of furcation lesion, large radiolucent area, and intense inflammatory infiltrate. All obturation materials used in this study induced new-bone formation.

Potential and clinical utility of stem cells in cardiovascular disease

Directory of Open Access Journals (Sweden)

Korff Krause

2010-03-01

Full Text Available Korff Krause, Carsten Schneider, Kai Jaquet, Karl-Heinz KuckHanseatic Heart Center Hamburg, Department of Cardiology, Asklepios Hospital St. Georg, Hamburg, GermanyAbstract: The recent identification of bone marrow-derived adult stem cells and other types of stem cells that could improve heart function after transplantation have raised high expectations. The basic mechanisms have been studied mostly in murine models. However, these experiments revealed controversial results on transdifferentiation vs transfusion of adult stem cells vs paracrine effects of these cells, which is still being debated. Moreover, the reproducibility of these results in precisely translated large animal models is still less well investigated. Despite these weaknesses results of several clinical trials including several hundreds of patients with ischemic heart disease have been published. However, there are no solid data showing that any of these approaches can regenerate human myocardium. Even the effectiveness of cell therapy in these approaches is doubtful. In future we need in this important field of regenerative medicine: i more experimental data in large animals that are closer to the anatomy and physiology of humans, including data on dose effects, comparison of different cell types and different delivery routes; ii a better understanding of the molecular mechanisms involved in the fate of transplanted cells; iii more intensive research on genuine regenerative medicine, applying genetic regulation and cell engineering.Keywords: stem cells, cardiovascular disease

The effect of sand/cement ratio on radon exhalation from cement specimens containing 226Ra

International Nuclear Information System (INIS)

Takriti, S.; Shweikani, R.; Ali, A. F.; Rajaa, G.

2002-09-01

Portland cement was mixed with different kind of sand (calcite and silica) in different ratio to produce radioactive specimens with radium chloride. The release of radon from these samples was studied. The results showed that radon release from the calcite-cement samples increased with the increases of the sand mixed ratio until fixed value (about 20%) then decreased to less than its release from the beginning, and the release changed with the sand size also. Radon release from silica-cement samples had the same observations of calcite-cement samples. It was found that calcite-cement reduced the radon exhalation quantity rather than the silica-cement samples. The decreases of the radon exhalation from the cement-sand may be due to the creation of free spaces in the samples, which gave the possibility to radon to decay into these free spaces rather than radon exhalation. The daughters of the radon decay 214 Bi and 214 Pb reported by gamma measurements of the cement-sand samples. (author)

Cement for oil well developed from ordinary cement: characterization physical, chemical and mineralogical

International Nuclear Information System (INIS)

Oliveira, D.N.S.; Neves, G. de A.; Chaves, A.C.; Mendonca, A.M.G.D.; Lima, M.S. de; Bezerra, U.T.

2012-01-01

This work aims to characterize a new type of cement produced from the mixture of ordinary Portland cement, which can be used as an option in the cementing of oil wells. To enable this work we used the method of lineal programming for the new cement composition, then conducted tests to characterize through particle size analysis by laser diffraction, chemical analysis by EDX, TGA, X-ray diffraction, time grip, resistance to compression. The overall result showed that the new cement had made low-C3A, takes more time to the CPP, thermal stability up to 500 ° C, the kinetics of hydration and low levels of major components consistent with the specifications of ABNT. (author)

[Effect of ceramic thickness and resin cement shades on final color of heat-pressed ceramic veneers].

Science.gov (United States)

Ren, D F; Zhan, K R; Chen, X D; Xing, W Z

2017-02-09

Objective: To analyze the effect of ceramic materials thickness and resin cement shades on the final color of ceramic veneers in the discolored teeth, and to investigate the color agreement of try-in pastes to the corresponding resin cements. Methods: Sixty artificial maxillary central incisor teeth (C2 shade) were used to simulate the natural discolored teeth and prepared according to veneer tooth preparation protocol. Veneers of different thickness in the body region (0.50 and 0.75 mm) were fabricated using ceramic materials (LT A2 shade, IPS e.max Press). The ceramic veneer specimens were bonded to the artificial teeth using the 6 shades of resin cements (Variolink Veneer: shades of LV-3, LV-2, HV+3; RelyX™ Veneer: shades of TR, A3, WO) ( n= 5). A clinical spectrophotometer was used to measure the color parameters of ceramic veneers at the cervical, body and incisal regions. Color changes of veneers before and after cementation were calculated and registered as ΔE1, and the changes between try-in paste and the corresponding resin cements were registered as ΔE2. Results: Three-way ANOVA indicated that ΔE1 and ΔE2 values were significantly affected by the ceramic thickness, resin cement shades and measuring regions ( Pceramic veneers were cemented with resin cements in shades of HV+3 and WO. The ΔE2 values of six shades ranged from 0.60-2.56. The shades of HV+3, WO and A3 resin cements were more than 1.60. Conclusions: Different thickness of ceramic materials, resin cement shades and measuring regions could affect the final color of ceramic veneers. The color differences of some resin cements and corresponding try-in pastes might be observed in clinical practice.

Progressing a human embryonic stem-cell-based regenerative medicine therapy towards the clinic.

Science.gov (United States)

Whiting, Paul; Kerby, Julie; Coffey, Peter; da Cruz, Lyndon; McKernan, Ruth

2015-10-19

Since the first publication of the derivation of human embryonic stem cells in 1998, there has been hope and expectation that this technology will lead to a wave of regenerative medicine therapies with the potential to revolutionize our approach to managing certain diseases. Despite significant resources in this direction, the path to the clinic for an embryonic stem-cell-based regenerative medicine therapy has not proven straightforward, though in the past few years progress has been made. Here, with a focus upon retinal disease, we discuss the current status of the development of such therapies. We also highlight some of our own experiences of progressing a retinal pigment epithelium cell replacement therapy towards the clinic. © 2015 The Author(s).

Catching moving targets: cancer stem cell hierarchies, therapy-resistance & considerations for clinical intervention.

LENUS (Irish Health Repository)

Gasch, Claudia

2017-01-01

It is widely believed that targeting the tumour-initiating cancer stem cell (CSC) component of malignancy has great therapeutic potential, particularly in therapy-resistant disease. However, despite concerted efforts, CSC-targeting strategies have not been efficiently translated to the clinic. This is partly due to our incomplete understanding of the mechanisms underlying CSC therapy-resistance. In particular, the relationship between therapy-resistance and the organisation of CSCs as Stem-Progenitor-Differentiated cell hierarchies has not been widely studied. In this review we argue that modern clinical strategies should appreciate that the CSC hierarchy is a dynamic target that contains sensitive and resistant components and expresses a collection of therapy-resisting mechanisms. We propose that the CSC hierarchy at primary presentation changes in response to clinical intervention, resulting in a recurrent malignancy that should be targeted differently. As such, addressing the hierarchical organisation of CSCs into our bench-side theory should expedite translation of CSC-targeting to bed-side practice. In conclusion, we discuss strategies through which we can catch these moving clinical targets to specifically compromise therapy-resistant disease.

Informed consent in clinical trials using stem cells: Sugges tions and ...

African Journals Online (AJOL)

2015-08-01

Aug 1, 2015 ... research. The correlated results showed the need for continuous training and education of elucidators in order to make sure that they acquire and maintain ... in the recommendations show that improving IC related to stem cell research is a .... of this clinical trial. • Contact information and consultation service.

Development of a degradable cement of calcium phosphate and calcium sulfate composite for bone reconstruction

International Nuclear Information System (INIS)

Guo, H; Wei, J; Liu, C S

2006-01-01

A new type of composite bone cement was prepared and investigated by adding calcium sulfate (CS) to calcium phosphate cement (CPC). This composite cement can be handled as a paste and easily shaped into any contour, which can set within 5-20 min, the setting time largely depending on the liquid-solid (L/S) ratio; adding CS to CPC had little effect on the setting time of the composite cements. No obvious temperature increase and pH change were observed during setting and immersion in simulated body fluid (SBF). The compressive strength of the cement decreased with an increase in the content of CS. The degradation rate of the composite cements increased with time when the CS content was more than 20 wt%. Calcium deficient apatite could form on the surface of the composite cement because the release of calcium into SBF from the dissolution of CS and the apatite of the cement induced the new apatite formation; increasing the content of CS in the composite could improve the bioactivity of the composite cements. The results suggested that composite cement has a reasonable setting time, excellent degradability and suitable mechanical strength and bioactivity, which shows promising prospects for development as a clinical cement

Stem cells in dentistry--part I: stem cell sources.

Science.gov (United States)

Egusa, Hiroshi; Sonoyama, Wataru; Nishimura, Masahiro; Atsuta, Ikiru; Akiyama, Kentaro

2012-07-01

Stem cells can self-renew and produce different cell types, thus providing new strategies to regenerate missing tissues and treat diseases. In the field of dentistry, adult mesenchymal stem/stromal cells (MSCs) have been identified in several oral and maxillofacial tissues, which suggests that the oral tissues are a rich source of stem cells, and oral stem and mucosal cells are expected to provide an ideal source for genetically reprogrammed cells such as induced pluripotent stem (iPS) cells. Furthermore, oral tissues are expected to be not only a source but also a therapeutic target for stem cells, as stem cell and tissue engineering therapies in dentistry continue to attract increasing clinical interest. Part I of this review outlines various types of intra- and extra-oral tissue-derived stem cells with regard to clinical availability and applications in dentistry. Additionally, appropriate sources of stem cells for regenerative dentistry are discussed with regard to differentiation capacity, accessibility and possible immunomodulatory properties. Copyright © 2012 Japan Prosthodontic Society. Published by Elsevier Ltd. All rights reserved.

Study on properties and testing methods of thermo-responsive cementing system for well cementing in heavy oil thermal recovery

Science.gov (United States)

Li, Lianjiang

2017-08-01

In this paper, thermo-responsive cement slurry system were being developed, the properties of conventional cement slurry, compressive strength high temperature of cement sheath, mechanical properties of cement sheath and thermal properties of cement sheath were being tested. Results were being used and simulated by Well-Life Software, Thermo-responsive cement slurry system can meet the requirements of heavy oil thermal recovery production. Mechanical and thermal properties of thermo-responsive cement sheath were being tested. Tensile fracture energy of the thermo-responsive cement sheath is larger than conventional cement. The heat absorption capacity of conventional cement sheath is larger than that of thermo-responsive cement sheath, this means more heat is needed for the unit mass once increasing 1.0 °C, which also indicates that thermo-responsive cement own good heat insulating and preservation effects. The heat conductivity coefficient and thermal expansion coefficient of thermo-responsive cement is less than and conventional cement, this means that thermo-responsive cement have good heat preservation and insulation effects with good thermal expansion stabilities.

Effect of temporary cements on the microtensile bond strength of self-etching and self-adhesive resin cement.

Science.gov (United States)

Carvalho, Edilausson Moreno; Carvalho, Ceci Nunes; Loguercio, Alessandro Dourado; Lima, Darlon Martins; Bauer, José

2014-11-01

The aim of this study was to evaluate the microtensile bond strength (µTBS) of self-etching and self-adhesive resin cement systems to dentin affected by the presence of remnants of either eugenol-containing or eugenol-free temporary cements. Thirty extracted teeth were obtained and a flat dentin surface was exposed on each tooth. Acrylic blocks were fabricated and cemented either with one of two temporary cements, one zinc oxide eugenol (ZOE) and one eugenol free (ZOE-free), or without cement (control). After cementation, specimens were stored in water at 37°C for 1 week. The restorations and remnants of temporary cements were removed and dentin surfaces were cleaned with pumice. Resin composite blocks were cemented to the bonded dentin surfaces with one of two resin cements, either self-etching (Panavia F 2.0) or self-adhesive (RelyX U-100). After 24 h, the specimens were sectioned to obtain beams for submission to µTBS. The fracture mode was evaluated under a stereoscopic loupe and a scanning electron microscope (SEM). Data from µTBS were submitted to two-way repeated-measure ANOVA and the Tukey test (alpha = 0.05). The cross-product interaction was statistically significant (p cements reduced the bond strength to Panavia self-etching resin cements only (p cements did not interfere in the bond strength to dentin of self-adhesive resin cements.

An Experimental Study of Portland Cement and Superfine Cement Slurry Grouting in Loose Sand and Sandy Soil

Directory of Open Access Journals (Sweden)

Weijing Yao

2018-04-01

Full Text Available Grouting technology is widely applied in the fields of geotechnical engineering in infrastructure. Loose sand and sandy soil are common poor soils in tunnel and foundation treatments. It is necessary to use superfine cement slurry grouting in the micro-cracks of soil. The different effectiveness of Portland cement slurry and superfine cement slurry in sandy soil by the laboratory grouting experiment method were presented in this paper. The grouting situations of superfine cement slurry injected into sand and sandy soil were explored. The investigated parameters were the dry density, wet density, moisture content, internal friction angle, and cohesion force. The results show that the consolidation effect of superfine cement is better than that of Portland cement due to the small size of superfine cement particles. The superfine cement can diffuse into the sand by infiltration, extrusion, and splitting. When the water–cement ratio of superfine cement slurry is less than 2:1 grouting into loose sand, the dry and wet density decrease with the increase in the water–cement ratio, while the moisture content and cohesive force gradually increase. When the water–cement ratio of superfine cement slurry is 1:1 grouting into loose sand and sandy soil, the dry density, wet density, and cohesive force of loose sand are larger than those of sandy soil. The results of the experiment may be relevant for engineering applications.

[Correlation analysis of cement leakage with volume ratio of intravertebral bone cement to vertebral body and vertebral body wall incompetence in percutaneous vertebroplasty for osteoporotic vertebral compression fractures].

Science.gov (United States)

Liang, De; Ye, Linqiang; Jiang, Xiaobing; Huang, Weiquan; Yao, Zhensong; Tang, Yongchao; Zhang, Shuncong; Jin, Daxiang

2014-11-01

To investigate the risk factors of cement leakage in percutaneous vertebroplasty (PVP) for osteoporotic vertebral compression fracture (OVCF). Between March 2011 and March 2012, 98 patients with single level OVCF were treated by PVP, and the clinical data were analyzed retrospectively. There were 13 males and 85 females, with a mean age of 77.2 years (range, 54-95 years). The mean disease duration was 43 days (range, 15-120 days), and the mean T score of bone mineral density (BMD) was -3.8 (range, -6.7- -2.5). Bilateral transpedicular approach was used in all the patients. The patients were divided into cement leakage group and no cement leakage group by occurrence of cement leakage based on postoperative CT. Single factor analysis was used to analyze the difference between 2 groups in T score of BMD, operative level, preoperative anterior compression degree of operative vertebrae, preoperative middle compression degree of operative vertebrae, preoperative sagittal Cobb angle of operative vertebrae, preoperative vertebral body wall incompetence, cement volume, and volume ratio of intravertebral bone cement to vertebral body. All relevant factors were introduced to logistic regression analysis to analyze the risk factors of cement leakage. All procedures were performed successfully. The mean operation time was 40 minutes (range, 30-50 minutes), and the mean volume ratio of intravertebral bone cement to vertebral body was 24.88% (range, 7.84%-38.99%). Back pain was alleviated significantly in all the patients postoperatively. All patients were followed up with a mean time of 8 months (range, 6-12 months). Cement leakage occurred in 49 patients. Single factor analysis showed that there were significant differences in the volume ratio of intravertebral bone cement to vertebral body and preoperative vertebral body wall incompetence between 2 groups (P 0.05). The logistic regression analysis showed that the volume ratio of intravertebral bone cement to vertebral body (P

Asphalt cement poisoning

Science.gov (United States)

... petroleum material that hardens when it cools. Asphalt cement poisoning occurs when someone swallows asphalt. If hot ... found in: Road paving materials Roofing materials Tile cements Asphalt may also be used for other purposes.

Sustainable Blended Cements-Influences of Packing Density on Cement Paste Chemical Efficiency.

Science.gov (United States)

Knop, Yaniv; Peled, Alva

2018-04-18

This paper addresses the development of blended cements with reduced clinker amount by partial replacement of the clinker with more environmentally-friendly material (e.g., limestone powders). This development can lead to more sustainable cements with reduced greenhouse gas emission and energy consumption during their production. The reduced clicker content was based on improved particle packing density and surface area of the cement powder by using three different limestone particle diameters: smaller (7 µm, 3 µm) or larger (70 µm, 53 µm) than the clinker particles, or having a similar size (23 µm). The effects of the different limestone particle sizes on the chemical reactivity of the blended cement were studied by X-ray diffraction (XRD), thermogravimetry and differential thermogravimetry (TG/DTG), loss on ignition (LOI), isothermal calorimetry, and the water demand for reaching normal consistency. It was found that by blending the original cement with limestone, the hydration process and the reactivity of the limestone itself were increased by the increased surface area of the limestone particles. However, the carbonation reaction was decreased with the increased packing density of the blended cement with limestone, having various sizes.

Push-out bond strengths of different dental cements used to cement glass fiber posts.

Science.gov (United States)

Pereira, Jefferson Ricardo; Lins do Valle, Accácio; Ghizoni, Janaina Salomon; Lorenzoni, Fábio César; Ramos, Marcelo Barbosa; Barbosa, Marcelo Ramos; Dos Reis Só, Marcus Vinícius

2013-08-01

Since the introduction of glass fiber posts, irreversible vertical root fractures have become a rare occurrence; however, adhesive failure has become the primary failure mode. The purpose of this study was to evaluate the push-out bond strength of glass fiber posts cemented with different luting agents on 3 segments of the root. Eighty human maxillary canines with similar root lengths were randomly divided into 8 groups (n=10) according to the cement assessed (Rely X luting, Luting and Lining, Ketac Cem, Rely X ARC, Biscem, Duo-link, Rely X U100, and Variolink II). After standardized post space preparation, the root dentin was pretreated for dual-polymerizing resin cements and untreated for the other cements. The mixed luting cement paste was inserted into post spaces with a spiral file and applied to the post surface that was seated into the canal. After 7 days, the teeth were sectioned perpendicular to their long axis into 1-mm-thick sections. The push-out test was performed at a speed of 0.5 mm/min until extrusion of the post occurred. The results were evaluated by 2-way ANOVA and the all pairwise multiple comparison procedures (Tukey test) (α=.05). ANOVA showed that the type of interaction between cement and root location significantly influenced the push-out strength (Pcements and glass ionomer cements showed significantly higher values compared to dual-polymerizing resin cements. In all root segments, dual-polymerizing resin cements provided significantly lower bond strength. Significant differences among root segments were found only for Duo-link cement. Copyright © 2013 The Editorial Council of the Journal of Prosthetic Dentistry. Published by Mosby, Inc. All rights reserved.

Mineral resource of the month: hydraulic cement

Science.gov (United States)

van Oss, Hendrik G.

2012-01-01

Hydraulic cements are the binders in concrete and most mortars and stuccos. Concrete, particularly the reinforced variety, is the most versatile of all construction materials, and most of the hydraulic cement produced worldwide is portland cement or similar cements that have portland cement as a basis, such as blended cements and masonry cements. Cement typically makes up less than 15 percent of the concrete mix; most of the rest is aggregates. Not counting the weight of reinforcing media, 1 ton of cement will typically yield about 8 tons of concrete.

Stem Cell Basics

Science.gov (United States)

... Tips Info Center Research Topics Federal Policy Glossary Stem Cell Information General Information Clinical Trials Funding Information Current ... Basics » Stem Cell Basics I. Back to top Stem Cell Basics I. Introduction: What are stem cells, and ...

Hydration of fly ash cement and microstructure of fly ash cement pastes

Energy Technology Data Exchange (ETDEWEB)

Shiyuan, H.

1981-01-01

The strength development and hydration of fly ash cement and the influence of addition of gypsum on those were studied at normal and elevated temperatures. It was found that an addition of a proper amount of gypsum to fly ash cement could accelerate the pozzolanic reaction between CH and fly ash, and as a result, increase the strength of fly ash cement pastes after 28 days.

Analysis of Chemical Composition of Portland Cement in Ghana: A Key to Understand the Behavior of Cement

OpenAIRE

Bediako, Mark; Amankwah, Eric Opoku

2015-01-01

The performance of Portland cement in concrete or mortar formation is very well influenced by chemical compositions among other factors. Many engineers usually have little information on the chemical compositions of cement in making decisions for the choice of commercially available Portland cement in Ghana. This work analyzed five different brands of Portland cement in Ghana, namely, Ghacem ordinary Portland cement (OPC) and Portland limestone cement (PLC), CSIR-BRRI Pozzomix, Dangote OPC, a...

Influence of temporary cement contamination on the surface free energy and dentine bond strength of self-adhesive cements.

Science.gov (United States)

Takimoto, Masayuki; Ishii, Ryo; Iino, Masayoshi; Shimizu, Yusuke; Tsujimoto, Akimasa; Takamizawa, Toshiki; Ando, Susumu; Miyazaki, Masashi

2012-02-01

The surface free energy and dentine bond strength of self-adhesive cements were examined after the removal of temporary cements. The labial dentine surfaces of bovine mandibular incisors were wet ground with #600-grit SiC paper. Acrylic resin blocks were luted to the prepared dentine surfaces using HY Bond Temporary Cement Hard (HY), IP Temp Cement (IP), Fuji TEMP (FT) or Freegenol Temporary Cement (TC), and stored for 1 week. After removal of the temporary cements with an ultrasonic tip, the contact angle values of five specimens per test group were determined for the three test liquids, and the surface-energy parameters of the dentine surfaces were calculated. The dentine bond strengths of the self-adhesive cements were measured after removal of the temporary cements in a shear mode at a crosshead speed of 1.0mm/min. The data were subjected to one-way analysis of variance (ANOVA) followed by Tukey's HSD test. For all surfaces, the value of the estimated surface tension component γ(S)(d) (dispersion) was relatively constant at 41.7-43.3 mJm(-2). After removal of the temporary cements, the value of the γ(S)(h) (hydrogen-bonding) component decreased, particularly with FT and TC. The dentine bond strength of the self-adhesive cements was significantly higher for those without temporary cement contamination (8.2-10.6 MPa) than for those with temporary cement contamination (4.3-7.1 MPa). The γ(S) values decreased due to the decrease of γ(S)(h) values for the temporary cement-contaminated dentine. Contamination with temporary cements led to lower dentine bond strength. The presence of temporary cement interferes with the bonding performance of self-adhesive cements to dentine. Care should be taken in the methods of removal of temporary cement when using self-adhesive cements. Copyright © 2011 Elsevier Ltd. All rights reserved.

Potential Strategies to Address the Major Clinical Barriers Facing Stem Cell Regenerative Therapy for Cardiovascular Disease: A Review.

Science.gov (United States)

Nguyen, Patricia K; Neofytou, Evgenios; Rhee, June-Wha; Wu, Joseph C

2016-11-01

Although progress continues to be made in the field of stem cell regenerative medicine for the treatment of cardiovascular disease, significant barriers to clinical implementation still exist. To summarize the current barriers to the clinical implementation of stem cell therapy in patients with cardiovascular disease and to discuss potential strategies to overcome them. Information for this review was obtained through a search of PubMed and the Cochrane database for English-language studies published between January 1, 2000, and July 25, 2016. Ten randomized clinical trials and 8 systematic reviews were included. One of the major clinical barriers facing the routine implementation of stem cell therapy in patients with cardiovascular disease is the limited and inconsistent benefit observed thus far. Reasons for this finding are unclear but may be owing to poor cell retention and survival, as suggested by numerous preclinical studies and a small number of human studies incorporating imaging to determine cell fate. Additional studies in humans using imaging to determine cell fate are needed to understand how these factors contribute to the limited efficacy of stem cell therapy. Treatment strategies to address poor cell retention and survival are under investigation and include the following: coadministration of immunosuppressive and prosurvival agents, delivery of cardioprotective factors packaged in exosomes rather than the cells themselves, and use of tissue-engineering strategies to provide structural support for cells. If larger grafts are achieved using these strategies, it will be imperative to carefully monitor for the potential risks of tumorigenicity, immunogenicity, and arrhythmogenicity. Despite important achievements to date, stem cell therapy is not yet ready for routine clinical implementation. Significant research is still needed to address the clinical barriers outlined herein before the next wave of large clinical trials is under way.

Colorectal cancer and non-malignant respiratory disease in asbestos cement and cement workers

International Nuclear Information System (INIS)

Jacobsson, K.

1993-09-01

Radiologically visible parenchymal changes (small opacities >= 1/0;ILO 1980 classification) were present in 20% of a sample of workers (N=174), employed for 20 years (median) in an asbestos cement plant. Exposure-response relationships were found, after controlling for age and smoking habits. In a sample of asbestos cement workers with symptoms and signs suggestive of pulmonary disease (N=33), increased lung density measured by x-ray computed tomography, and reduced static lung volumes and lung compliance was found. In a cohort of asbestos cement workers (N=1.929) with an estimated median exposure of 1.2 fibres/ml, the mortality from non-malignant respiratory disease was increased in comparison to a regional reference cohort (N=1.233). A two-to three-fold increase of non-malignant respiratory mortality was noted among workers employed for more than a decade in the asbestos cement plant, compared to cement workers (N=1.526), who in their turn did not experience and increased risk compared to the general population. In the cohorts of asbestos cement and cement workers, there was a tow-to three-fold increased incidence of cancer in the right part of the colon, compared to the general population as well as to external reference cohorts of other industrial workers (N=3.965) and fishermen (N=8.092). A causal relation with the exposure to mineral dust and fibres was supported by the findings of higher risk estimated in subgroups with high cumulated asbestos doses or longer duration of cement work. The incidence of cancer in the left part of the colon was not increased. Morbidity data, but not mortality data, disclosed the subsite-specific risk pattern. Both asbestos cement workers and cement workers has an increased incidence of rectal cancer, compared with the general population, and with the fishermen. The risk was, however, of the same magnitude among the other industrial workers. 181 refs

Circulating mesenchymal stem cells and their clinical implications

Directory of Open Access Journals (Sweden)

Liangliang Xu

2014-01-01

Full Text Available Circulating mesenchymal stem cells (MSCs is a new cell source for tissue regeneration and tissue engineering. The characteristics of circulating MSCs are similar to those of bone marrow-derived MSCs (BM-MSCs, but they exist at a very low level in healthy individuals. It has been demonstrated that MSCs are able to migrate to the sites of injury and that they have some distinct genetic profiles compared to BM-MSCs. The current review summaries the basic knowledge of circulating MSCs and their potential clinical applications, such as mobilizing the BM-MSCs into circulation for therapy. The application of MSCs to cure a broad spectrum of diseases is promising, such as spinal cord injury, cardiovascular repair, bone and cartilage repair. The current review also discusses the issues of using of allogeneic MSCs for clinical therapy.

Migration and head penetration of Vitamin-E diffused cemented polyethylene cup compared to standard cemented cup in total hip arthroplasty: study protocol for a randomised, double-blind, controlled trial (E1 HIP).

Science.gov (United States)

Sköldenberg, Olof; Rysinska, Agata; Chammout, Ghazi; Salemyr, Mats; Muren, Olle; Bodén, Henrik; Eisler, Thomas

2016-07-07

In vitro, Vitamin-E-diffused, highly cross-linked polyethylene (PE) has been shown to have superior wear resistance and improved mechanical properties when compared to those of standard highly cross-linked PE liners used in total hip arthroplasty (THA). The aim of the study is to evaluate the safety of a new cemented acetabular cup with Vitamin-E-doped PE regarding migration, head penetration and clinical results. In this single-centre, double-blinded, randomised controlled trial, we will include 50 patients with primary hip osteoarthritis scheduled for THA and randomise them in a 1:1 ratio to a cemented cup with either argon gas-sterilised PE (control group) or Vitamin-E-diffused PE (vitamin-e group). All patients and the assessor of the primary outcome will be blinded and the same uncemented stem will be used for all participants. The primary end point will be proximal migration of the cup at 2 years after surgery measured with radiostereometry. Secondary end points include proximal migration at other follow-ups, total migration, femoral head penetration, clinical outcome scores and hip-related complications. Patients will be followed up at 3 months and at 1, 2, 5 and 10 years postoperatively. Results will be analysed using 95% CIs for the effect size. A regression model will also be used to adjust for stratification factors. The ethical committee at Karolinska Institutet has approved the study. The first results from the study will be disseminated to the medical community via presentations and publications in relevant medical journals when the last patient included has been followed up for 2 years. NCT02254980. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/

Compressive Strength and Physical Properties Behavior of Cement Mortars with addition of Cement Klin Dust

OpenAIRE

Auday A Mehatlaf

2017-01-01

Cement Klin Dust (CKD) was the waste of almost cement industry factories, so that in this paper utilization of CKD as filler in cement and/or concrete was the main objective. CKD from the Karbala cement factory had been used and analysis to know the chemical composition of the oxides was done. In this paper cement mortars with different weight percentages of CKD (0,5,10,20,30,40) had been prepared. Physical properties such as density and porosity were done in different age curing (3, 7, 28) d...

Chromium content in human skin after in vitro application of ordinary cement and ferrous-sulphate-reduced cement

DEFF Research Database (Denmark)

Fullerton, A; Gammelgaard, Bente; Avnstorp, C

1993-01-01

The amount of chromium found in human skin after in vitro application of cement suspensions on full-thickness human skin in diffusion cells was investigated. Cement suspensions made from ordinary Portland cement or Portland cement with the chromate reduced with added ferrous sulphate were used....... The cement suspensions were either applied on the skin surface under occlusion for 48 h or applied repeatedly every 24 h for 96 h. No statistically significant difference in chromium content of skin layers between skin exposed to ordinary Portland cement, skin exposed to cement with added ferrous sulphate...... and unexposed skin was observed, despite a more permeable skin barrier at the alkaline pH of the cement suspensions, i.e., pH 12.5. Increased chromium levels in epidermis and dermis were seen when ordinary Portland cement was applied as a suspension with added sodium sulphate (20%) on the skin surface for 96 h...

Hydration kinetics of cement composites with varying water-cement ratio using terahertz spectroscopy

Science.gov (United States)

Ray, Shaumik; Dash, Jyotirmayee; Devi, Nirmala; Sasmal, Saptarshi; Pesala, Bala

2015-03-01

Cement is mixed with water in an optimum ratio to form concrete with desirable mechanical strength and durability. The ability to track the consumption of major cement constituents, viz., Tri- and Dicalcium Silicates (C3S, C2S) reacting with water along with the formation of key hydration products, viz., Calcium-Silicate-Hydrate (C-S-H) which gives the overall strength to the concrete and Calcium Hydroxide (Ca(OH)2), a hydration product which reduces the strength and durability, using an efficient technique is highly desirable. Optimizing the amount of water to be mixed with cement is one of the main parameters which determine the strength of concrete. In this work, THz spectroscopy has been employed to track the variation in hydration kinetics for concrete samples with different water-cement ratios, viz., 0.3, 0.4, 0.5 and 0.6. Results show that for the sample with water-cement ratio of 0.3, significant amount of the C3S and C2S remain unreacted even after the initial hydration period of 28 days while for the cement with water-cement ratio of 0.6, most of the constituents get consumed during this stage. Analysis of the formation of Ca(OH)2 has been done which shows that the concrete sample with water-cement ratio of 0.6 produces the highest amount of Ca(OH)2 due to higher consumption of C3S/C2S in presence of excess water which is not desirable. Samples with water-cement ratio of 0.4 and 0.5 show more controlled reaction during the hydration which can imply formation of an optimized level of desired hydration products resulting in a more mechanically strong and durable concrete.

Clinical efficacy of bone cement injectable pedicle screw system combined with intervertebral fusion in treatment of lumbar spondylolysis and osteoporosis

Directory of Open Access Journals (Sweden)

Peng-yi DAI

2016-10-01

Full Text Available Objective 　To observe the therapeutic effect of bone cement injectable pedicle screw system combined with intervertebral fusion for lumbar spondylolysis and osteoporosis. Methods 　The clinical data were analyzed retrospectively of 21 patients with lumbar spondylolysis and osteoporosis who received treatment of bone cement injectable pedicle screw system and intervertebral fusion from Aug. 2013 to Nov. 2015. The 21 patients (9 males and 12 females aged from 60 to 80 years (mean 64 years old; 6 of them presented degenerative spondylolysis, 15 with isthmic spondylolisthesis; 2 cases had I degree slippage, 13 had Ⅱdegree slippage, 6 had Ⅲdegree slippage, and all the cases were unisegmental slippage including 9 cases in L4 and 12 cases in L5. Bone mineral density of lumbar vertebrae (L2-L5 was measured with dual-energy X-ray absorptiometry, and T values conforming to the diagnostic criteria of osteoporosis were less than or equal to -2.5; All patients were operated with whole lamina resection for decompression, bone cement injectable pedicle screws system implantation, propped open reduction and fixation intervertebral fusion. The clinical outcomes were determined by the radiographic evaluation including intervertebral height, height of intervertebral foramen, slip distance, slip rate and slip angle, and Oswestry disability index (ODI on preoperative, 3 months after operation and the end of the time, and the interbody fusion were followed up. Results 　Cerebrospinal fluid leakage of incision was observed in two cases after operation, compression and dressing to incision, Trendelenburg position, dehydration and other treatments were taken, and the stitches of incisions were taken out on schedule. Slips in the 21 patients were reset to different extent, and lumbar physiological curvatures were recovered. The intervertebral height and height of intervertebral foramen were obviously higher 3 months after operation than that before operation (P0

Polymer-cement interactions towards improved wellbore cement fracture sealants

Science.gov (United States)

Beckingham, B. S.; Iloejesi, C.; Minkler, M. J.; Schindler, A. K.; Beckingham, L. E.

2017-12-01

Carbon capture, utilization, and storage (CCUS) in deep geologic formations is a promising means of reducing point source emissions of CO2. In these systems, CO2 is captured at the source and then injected to be utilized (eg. in enhanced oil recovery or as a working fluid in enhanced geothermal energy plants) or stored in geologic formations such as depleted oil and gas reservoirs or saline aquifers. While CCUS in subsurface systems could aid in reducing atmospheric CO2 emissions, the potential for CO2 leakage from these systems to overlying formations remains a major limitation and poses a significant risk to the security of injected CO2. Thus, improved materials for both initial wellbore isolation and repairing leakage pathways that develop over time are sought. One approach for the repair of cement fractures in wellbore (and other) systems is the injection of polymer materials into the fracture with a subsequent environmentally dependent (temperature, pressure, pH, etc.) densification or solidification. Here, we aim to investigate novel polymer materials for use to repair leaking wellbores in the context of CCUS. We synthesize and fully characterize a series of novel polymer materials and utilize a suite of analysis techniques to examine polymer-cement interactions at a range of conditions (namely temperature, pressure and pH). Initial findings will be leveraged to design novel polymer materials for further evaluation in polymer-cement composite cores, cement fracture healing, and the aging behavior of healed cements.

Absorption Characteristics of Cement Combination Concrete Containing Portland Cement, fly ash, and Metakaolin

Directory of Open Access Journals (Sweden)

Folagbade S.O.

2016-03-01

Full Text Available The resistance to water penetration of cement combination concretes containing Portland cement (PC, fly ash (FA, and metakaolin (MK have been investigated at different water/cement (w/c ratios, 28-day strengths, and depths of water penetration using their material costs and embodied carbon-dioxide (eCO2 contents. Results revealed that, at equal w/c ratio, eCO2 content reduced with increasing content of FA and MK. MK contributed to the 28-day strengths more than FA. Compared with PC, FA reduced cost and increased the depth of water penetration, MK increased cost and reduced the depth of water penetration, and their ternary combinations become beneficial. At equal strengths and levels of resistance to water penetration, most of the cement combination concretes are more environmentally compatible and costlier than PC concrete. Only MK binary cement concretes with 10%MK content or more and ternary cement concretes at a total replacement level of 55% with 10%MK content or more have higher resistance to water penetration than PC concrete.

ULTRA-LIGHTWEIGHT CEMENT

Energy Technology Data Exchange (ETDEWEB)

Fred Sabins

2001-10-23

The objective of this project is to develop an improved ultra-lightweight cement using ultra-lightweight hollow glass spheres (ULHS). Work reported herein addresses tasks performed in the fourth quarter as well as the other three quarters of the past year. The subjects that were covered in previous reports and that are also discussed in this report include: Analysis of field laboratory data of active cement applications from three oil-well service companies; Preliminary findings from a literature review focusing on problems associated with ultra-lightweight cements; Summary of pertinent information from Russian ultra-lightweight cement literature review; and Comparison of compressive strengths of ULHS systems using ultrasonic and crush methods Results reported from the fourth quarter include laboratory testing of ULHS systems along with other lightweight cement systems--foamed and sodium silicate slurries. These comparison studies were completed for two different densities (10.0 and 11.5 lb/gal) and three different field application scenarios. Additional testing included the mechanical properties of ULHS systems and other lightweight systems. Studies were also performed to examine the effect that circulation by centrifugal pump during mixing has on breakage of ULHS.

Safety and effectiveness of stem cell therapies in early-phase clinical trials in stroke: a systematic review and meta-analysis.

Science.gov (United States)

Nagpal, Anjali; Choy, Fong Chan; Howell, Stuart; Hillier, Susan; Chan, Fiona; Hamilton-Bruce, Monica A; Koblar, Simon A

2017-08-30

Stem cells have demonstrated encouraging potential as reparative therapy for patients suffering from post-stroke disability. Reperfusion interventions in the acute phase of stroke have shown significant benefit but are limited by a narrow window of opportunity in which they are beneficial. Thereafter, rehabilitation is the only intervention available. The current review summarises the current evidence for use of stem cell therapies in stroke from early-phase clinical trials. The safety and feasibility of administering different types of stem cell therapies in stroke seem to be reasonably proven. However, the effectiveness needs still to be established through bigger clinical trials with more pragmatic clinical trial designs that address the challenges raised by the heterogeneous nature of stroke per se, as well those due to unique characteristics of stem cells as therapeutic agents.

[Non-cemented self-locking total arthroplasty of the hip. Clinical and radiological results after three years].

Science.gov (United States)

Desjardins, A L; Roy, A; Duchesne, R; Béliveau, P; Fallaha, M; Bornais, S

1993-01-01

We reviewed 47 patients who had fifty-one (51) primary, cementless biofit total hip arthroplasties (THA) implanted at Maisonneuve-Rosemont Hospital between 1986 and 1990. An independent observer rated the patients on the Harris Hip Score (HHS) by questionnaire, physical examination and radiological assessment. The average follow-up was 40 months. Twenty-two percent (22%) of the femoral components had been revised because of incapacitating pain, limping or a HHS inferior to 60. A little more than 20% of the unrevised prostheses had a mediocre result (HHS inferior to 70). There was no correlation between results and radiological signs of instability. The femoral component of the hip arthroplasty has a poor clinical performance which compares unfavourably with cemented prostheses.

Is it cement to be? Downhole cement that uses zeolite additive may offer lightweight alternative

Energy Technology Data Exchange (ETDEWEB)

Mahoney, J.

2001-05-01

C2C Zeolite Corporation produces zeolites from a large deposit near Cache Creek, British Columbia, and processes them for use as an additive in downhole cement well casings. Early research indicates that zeolites can significantly improve the way downhole cement is made in the oil industry. Zeolites are made up mostly of silicates of aluminum and calcium. They have a great ability to absorb water, resulting in a lighter and more fluid cement than is currently available. C2C claims that zeolites will reduce cement weight, column pressure and operator costs. The cost benefits of using lighter cement downhole includes easier moving, processing and handling of the mix. Initial research suggests that zeolites might prove to be viable alternatives to other cement lighteners such as silica fumes or flyash. Zeolite-based cement also performed reasonably well in freeze-thaw tests and showed good adhesion and no evidence of shrinkage in downhole tests. 3 figs.

Prediction of hydroxyl concentrations in cement pore water using a numerical cement hydration model

NARCIS (Netherlands)

Eijk, van R.J.; Brouwers, H.J.H.

2000-01-01

In this paper, a 3D numerical cement hydration model is used for predicting alkali and hydroxyl concentrations in cement pore water. First, this numerical model is calibrated for Dutch cement employing both chemical shrinkage and calorimetric experiments. Secondly, the strength development of some

Development of low radio-activated cement. Characteristics of cement and clinker that decreased liquid phase content

International Nuclear Information System (INIS)

Ichitsubo, Koki

2008-01-01

Low radio-activated cement was developed by decreasing the parent elements of radionuclides in the materials. The characteristics of products, decreasing method of Na, Eu and Co in cement, design, tests, evaluation, and analysis of low radio-activated cement clinker are reported. In order to decrease the content of Na, Eu and Co, the raw materials have to include natural materials such as limestone and silica stone. The production method is the same as white cement. The low radio-activated cement produced by rotary kiln showed 4.9% C 3 A, 1.1% C 4 AF, 26.9% C 3 S and 61.0% C 2 S, which values were standardized by the Japanese Industrial Standards (JIS) of low temperature Portland cement. Another product that decreased a little more liquid phase content showed 4.0% C 3 A, 1.0% C 4 AF, 32.3% C 3 S and 56.5% C 2 S, which was standardized by JIS of sulfate resisting Portland cement. In the case of decommissioning reactor constructed by the low radio-activated cement, the whole amount of waste cement will be no more than the clearance level. (S.Y.)

The effects of cement-based and cement-ash-based mortar slabs on indoor air quality

DEFF Research Database (Denmark)

Krejcirikova, Barbora; Kolarik, Jakub; Wargocki, Pawel

2018-01-01

The effects of emissions from cement-based and cement-ash-based mortar slabs were studied. In the latter, 30% of the cement content had been replaced by sewage sludge ash. They were tested singly and together with either carpet or linoleum. The air exhausted from the chambers was assessed by means...... of odour intensity and chemical characterization of emissions. Odour intensity increased with the increased exposed area of the slabs. It did not differ significantly between cement-based or cement-ash-based mortar and neither did the chemical composition of the exhaust air. A significant sink effect...

Peri-implant stress correlates with bone and cement morphology: Micro-FE modeling of implanted cadaveric glenoids.

Science.gov (United States)

Wee, Hwabok; Armstrong, April D; Flint, Wesley W; Kunselman, Allen R; Lewis, Gregory S

2015-11-01

Aseptic loosening of cemented joint replacements is a complex biological and mechanical process, and remains a clinical concern especially in patients with poor bone quality. Utilizing high resolution finite element analysis of a series of implanted cadaver glenoids, the objective of this study was to quantify relationships between construct morphology and resulting mechanical stresses in cement and trabeculae. Eight glenoid cadavers were implanted with a cemented central peg implant. Specimens were imaged by micro-CT, and subject-specific finite element models were developed. Bone volume fraction, glenoid width, implant-cortex distance, cement volume, cement-cortex contact, and cement-bone interface area were measured. Axial loading was applied to the implant of each model and stress distributions were characterized. Correlation analysis was completed across all specimens for pairs of morphological and mechanical variables. The amount of trabecular bone with high stress was strongly negatively correlated with both cement volume and contact between the cement and cortex (r = -0.85 and -0.84, p implant-cortex distance. Contact between the cement and underlying cortex may dramatically reduce trabecular bone stresses surrounding the cement, and this contact depends on bone shape, cement amount, and implant positioning. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc.

Influence of carbonation on the acid neutralization capacity of cements and cement-solidified/stabilized electroplating sludge.

Science.gov (United States)

Chen, Quanyuan; Zhang, Lina; Ke, Yujuan; Hills, Colin; Kang, Yanming

2009-02-01

Portland cement (PC) and blended cements containing pulverized fuel ash (PFA) or granulated blast-furnace slag (GGBS) were used to solidify/stabilize an electroplating sludge in this work. The acid neutralization capacity (ANC) of the hydrated pastes increased in the order of PC > PC/GGBS > PC/PFA. The GGBS or PFA replacement (80 wt%) reduced the ANC of the hydrated pastes by 30-50%. The ANC of the blended cement-solidified electroplating sludge (cement/sludge 1:2) was 20-30% higher than that of the hydrated blended cement pastes. Upon carbonation, there was little difference in the ANC of the three cement pastes, but the presence of electroplating sludge (cement/sludge 1:2) increased the ANC by 20%. Blended cements were more effective binders for immobilization of Ni, Cr and Cu, compared with PC, whereas Zn was encapsulated more effectively in the latter. Accelerated carbonation improved the immobilization of Cr, Cu and Zn, but not Ni. The geochemical code PHREEQC, with the edited database from EQ3/6 and HATCHES, was used to calculate the saturation index and solubility of likely heavy metal precipitates in cement-based solidification/stabilization systems. The release of heavy metals could be related to the disruption of cement matrices and the remarkable variation of solubility of heavy metal precipitates at different pH values.

Research gaps identified during systematic reviews of clinical trials: glass-ionomer cements.

Science.gov (United States)

Mickenautsch, Steffen

2012-06-29

To report the results of an audit concerning research gaps in clinical trials that were accepted for appraisal in authored and published systematic reviews regarding the application of glass-ionomer cements (GIC) in dental practice Information concerning research gaps in trial precision was extracted, following a framework that included classification of the research gap reasons: 'imprecision of information (results)', 'biased information', 'inconsistency or unknown consistency' and 'not the right information', as well as research gap characterization using PICOS elements: population (P), intervention (I), comparison (C), outcomes (O) and setting (S). Internal trial validity assessment was based on the understanding that successful control for systematic error cannot be assured on the basis of inclusion of adequate methods alone, but also requires empirical evidence about whether such attempt was successful. A comprehensive and interconnected coverage of GIC-related clinical topics was established. The most common reasons found for gaps in trial precision were lack of sufficient trials and lack of sufficient large sample size. Only a few research gaps were ascribed to 'Lack of information' caused by focus on mainly surrogate trial outcomes. According to the chosen assessment criteria, a lack of adequate randomisation, allocation concealment and blinding/masking in trials covering all reviewed GIC topics was noted (selection- and detection/performance bias risk). Trial results appear to be less affected by loss-to-follow-up (attrition bias risk). This audit represents an adjunct of the systematic review articles it has covered. Its results do not change the systematic review's conclusions but highlight existing research gaps concerning the precision and internal validity of reviewed trials in detail. These gaps should be addressed in future GIC-related clinical research.

The stem-cell application in ischemic heart disease: Basic principles, specifics and practical experience from clinical studies

Directory of Open Access Journals (Sweden)

Banović Marko

2015-01-01

Full Text Available Longer life duration, different clinical presentations of coronary disease, as well as high incidence of comorbidity in patients with ischemic heart disease have led to an increase in the incidence of ischemic heart failure. Despite numerous and new treatment methods that act on different pathophysiological mechanisms that cause heart failure, and whose aim is to slowdown or stop the progression of this devastating disease, morbidity and mortality in these patients remain high. These facts have firstly led to the introduction of the experimental, and then clinical studies with the application of stem cells in patients with ischemic heart disease. Previous studies have shown that the application of stem cells is a feasible and safe method in patients with acute coronary syndrome, as well as in patients with chronic ischemic cardiomyopathy, but the efficacy of these methods in both of the abovementioned clinical syndromes has yet to be established. This review paper outlines the basic principles of treatment of ischemic heart disease with stem cells, as well as the experience and knowledge gained in previous clinical studies.

Monitoring cancer stem cells: insights into clinical oncology

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Lin SC

2016-02-01

Full Text Available ShuChen Lin,1,* YingChun Xu,2,* ZhiHua Gan,1 Kun Han,1 HaiYan Hu,3 Yang Yao,3 MingZhu Huang,4 DaLiu Min1 1Department of Oncology, Shanghai Sixth People’s Hospital East Campus, Shanghai Jiao Tong University, 2Department of Oncology, Renji Hospital, Shanghai Jiao Tong University, 3Department of Oncology, The Sixth People’s Hospital, Shanghai Jiao Tong University, 4Department of Medical Oncology, Cancer Hospital of Fudan University, Shanghai, People’s Republic of China *These authors contributed equally to this work Abstract: Cancer stem cells (CSCs are a small, characteristically distinctive subset of tumor cells responsible for tumor initiation and progression. Several treatment modalities, such as surgery, glycolytic inhibition, driving CSC proliferation, immunotherapy, and hypofractionated radiotherapy, may have the potential to eradicate CSCs. We propose that monitoring CSCs is important in clinical oncology as CSC populations may reflect true treatment response and assist with managing treatment strategies, such as defining optimal chemotherapy cycles, permitting pretreatment cancer surveillance, conducting a comprehensive treatment plan, modifying radiation treatment, and deploying rechallenge chemotherapy. Then, we describe methods for monitoring CSCs. Keywords: cancer stem cells, glycolytic inhibition, watchful waiting, rechallenge, immunotherapy

Health hazards of cement dust

International Nuclear Information System (INIS)

Meo, Sultan A.

2004-01-01

ven in the 21st century, millions of people are working daily in a dusty environment. They are exposed to different types of health hazards such as fume, gases and dust, which are risk factors in developing occupational disease. Cement industry is involved in the development of structure of this advanced and modern world but generates dust during its production. Cement dust causes lung function impairment, chronic obstructive lung disease, restrictive lung disease, pneumoconiosis and carcinoma of the lungs, stomach and colon. Other studies have shown that cement dust may enter into the systemic circulation and thereby reach the essentially all the organs of body and affects the different tissues including heart, liver, spleen, bone, muscles and hairs and ultimately affecting their micro-structure and physiological performance. Most of the studies have been previously attempted to evaluate the effects of cement dust exposure on the basis of spirometry or radiology, or both. However, collective effort describing the general effects of cement dust on different organ and systems in humans or animals, or both has not been published. Therefore, the aim of this review is to gather the potential toxic effects of cement dust and to minimize the health risks in cement mill workers by providing them with information regarding the hazards of cement dust. (author)

Evaluation of physico-chemical properties of Portland cements and MTA

Directory of Open Access Journals (Sweden)

Jorge Luis Gonçalves

2010-09-01

Full Text Available The purpose of this study was to evaluate the hydrogenionic potential and electrical conductivity of Portland cements and MTA, as well as the amount of arsenic and calcium released from these materials. In Teflon molds, samples of each material were agitated and added to plastic flasks containing distilled water for 3, 24, 72 and 168 h. The results were analyzed with a Kruskal-Wallis non-parametric test for global comparisons and a Dunn-Tukey test for pairwise comparisons. The results revealed no significant differences in the pH of the materials (p > 0.05. The electrical conductivity of the cements were not statistically different (p > 0.05. White non-structural cement and MTA BIO released the largest amount of calcium ions into solution (p 0.05. The results indicated that the physico-chemical properties of Portland cements and MTA were similar. Furthermore, all materials produced an alkaline environment and can be considered safe for clinical use because arsenic was not released. The electrical conductivity and the amount of calcium ions released into solution increased over time.

Evaluation of physico-chemical properties of Portland cements and MTA.

Science.gov (United States)

Gonçalves, Jorge Luis; Viapiana, Raqueli; Miranda, Carlos Eduardo Saraiva; Borges, Alvaro Henrique; Cruz Filho, Antônio Miranda da

2010-01-01

The purpose of this study was to evaluate the hydrogenionic potential and electrical conductivity of Portland cements and MTA, as well as the amount of arsenic and calcium released from these materials. In Teflon molds, samples of each material were agitated and added to plastic flasks containing distilled water for 3, 24, 72 and 168 h. The results were analyzed with a Kruskal-Wallis non-parametric test for global comparisons and a Dunn-Tukey test for pairwise comparisons. The results revealed no significant differences in the pH of the materials (p > 0.05). The electrical conductivity of the cements were not statistically different (p > 0.05). White non-structural cement and MTA BIO released the largest amount of calcium ions into solution (p 0.05). The results indicated that the physico-chemical properties of Portland cements and MTA were similar. Furthermore, all materials produced an alkaline environment and can be considered safe for clinical use because arsenic was not released. The electrical conductivity and the amount of calcium ions released into solution increased over time.

Using dehydrated cement paste as new type of cement additive

NARCIS (Netherlands)

Yu, R.; Shui, Z.H.; Dong, J

2013-01-01

This paper presents an experimental study, including evaluation and modification, on using dehydrated cement paste (DCP) as a new type of cement additive. After a series of processes, normal DCP (N-DCP) was produced as before and a modified form of DCP (M-DCP) was produced as well. The cementitious

Barium aluminate cement: its application

International Nuclear Information System (INIS)

Drozdz, M.; Wolek, W.

1975-01-01

The technology of manufacturing barium aluminate cement from barium sulfate and alumina, using a rotary kiln for firing the clinker is described. The method of granulation of the homogenized charge was used. Conditions of using the ''to mud'' method in industry were indicated. The physical and chemical properties of barium aluminate cement are determined and the quality of several batches of cement prepared on a semi-industrial scale and their suitability for making highly refractory concretes are tested. The optimal composition of the concretes is determined as a function of the mixing water and barium aluminate cement contents. Several experimental batches of concretes were used in the linings of furnaces in the steel industry. The suitability of these cements for use in fields other than steelmaking is examined. It is established that calcium aluminate cement has certain limited applications [fr

Comparative evaluation of marginal leakage of provisional crowns cemented with different temporary luting cements: In vitro study.

Science.gov (United States)

Arora, Sheen Juneja; Arora, Aman; Upadhyaya, Viram; Jain, Shilpi

2016-01-01

As, the longevity of provisional restorations is related to, a perfect adaptation and a strong, long-term union between restoration and teeth structures, therefore, evaluation of marginal leakage of provisional restorative materials luted with cements using the standardized procedures is essential. To compare the marginal leakage of the provisional crowns fabricated from Autopolymerizing acrylic resin crowns and bisphenol A-glycidyl dimethacrylate (BIS-GMA) resin crowns. To compare the marginal leakage of the provisional crowns fabricated from autopolymerizing acrylic resin crowns and BIS-GMA resin crowns cemented with different temporary luting cements. To compare the marginal leakage of the provisional crowns fabricated from autopolymerizing acrylic resin (SC-10) crowns cemented with different temporary luting cements. To compare the marginal leakage of the provisional crowns fabricated from BIS-GMA resin crowns (Protemp 4) cemented with different temporary luting cements. Freshly extracted 60 maxillary premolars of approximately similar dimensions were mounted in dental plaster. Tooth reduction with shoulder margin was planned to use a customized handpiece-holding jig. Provisional crowns were prepared using the wax pattern fabricated from computer aided designing/computer aided manufacturing milling machine following the tooth preparation. Sixty provisional crowns were made, thirty each of SC-10 and Protemp 4 and were then cemented with three different luting cements. Specimens were thermocycled, submerged in a 2% methylene blue solution, then sectioned and observed under a stereomicroscope for the evaluation of marginal microleakage. A five-level scale was used to score dye penetration in the tooth/cement interface and the results of this study was analyzed using the Chi-square test, Mann-Whitney U-test, Kruskal-Wallis H-test and the results were statistically significant P provisional crowns cemented with three different luting cements along the axial walls of

Analysis of CCRL proficiency cements 151 and 152 using the Virtual Cement and Concrete Testing Laboratory

International Nuclear Information System (INIS)

Bullard, Jeffrey W.; Stutzman, Paul E.

2006-01-01

To test the ability of the Virtual Cement and Concrete Testing Laboratory (VCCTL) software to predict cement hydration properties, characterization of mineralogy and phase distribution is necessary. Compositional and textural characteristics of Cement and Concrete Reference Laboratory (CCRL) cements 151 and 152 were determined via scanning electron microscopy (SEM) analysis followed by computer modeling of hydration properties. The general procedure to evaluate a cement is as follows: (1) two-dimensional SEM backscattered electron and X-ray microanalysis images of the cement are obtained, along with a measured particle size distribution (PSD); (2) based on analysis of these images and the measured PSD, three-dimensional microstructures of various water-to-cement ratios are created and hydrated using VCCTL, and (3) the model predictions for degree of hydration under saturated conditions, heat of hydration (ASTM C186), setting time (ASTM C191), and strength development of mortar cubes (ASTM C109) are compared to experimental measurements either performed at NIST or at the participating CCRL proficiency sample evaluation laboratories. For both cements, generally good agreement is observed between the model predictions and the experimental data

Physical characteristics, antimicrobial and odontogenesis potentials of calcium silicate cement containing hinokitiol

Energy Technology Data Exchange (ETDEWEB)

Huang, Ming-Hsien [Institute of Oral Science, Chung Shan Medical University, Taichung City, Taiwan (China); Shen, Yu-Fang; Hsu, Tuan-Ti [3D Printing Medical Research Center, China Medical University Hospital, China Medical University, Taichung City, Taiwan (China); Huang, Tsui-Hsien [School of Dentistry, Chung Shan Medical University, Taichung City, Taiwan (China); Department of Stomatology, Chung Shan Medical University Hospital, Taichung City, Taiwan (China); Shie, Ming-You, E-mail: eviltacasi@gmail.com [3D Printing Medical Research Center, China Medical University Hospital, China Medical University, Taichung City, Taiwan (China)

2016-08-01

Hinokitiol is a natural material and it has antibacterial and anti-inflammatory effects. The purpose of this study was to evaluate the material characterization, cell viability, antibacterial and anti-inflammatory abilities of the hinokitiol-modified calcium silicate (CS) cement as a root end filling material. The setting times, diametral tensile strength (DTS) values and XRD patterns of CS cements with 0–10 mM hinokitiol were examined. Then, the antibacterial effect and the expression levels of cyclooxygenase 2 (COX-2) and interleukin-1 (IL-1) of the hinokitiol-modified CS cements were evaluated. Furthermore, the cytocompatibility, the expression levels of the markers of odontoblastic differentiation, mineralized nodule formation and calcium deposition of human dental pulp cells (hDPCs) cultured on hinokitiol-modified CS cements were determined. The hinokitiol-modified CS cements had better antibacterial and anti-inflammatory abilities and cytocompatibility than non-modified CS cements. Otherwise, the hinokitiol-modified CS cements had suitable setting times and better odontoblastic potential of hDPCs. Previous report pointed out that the root-end filling materials may induce inflammatory cytokines reaction. In our study, hinokitiol-modified CS cements not only inhibited the expression level of inflammatory cytokines, but also had better cytocompatibility, antimicrobial properties and active ability of odontoblastic differentiation of hDPCs. Therefore, the hinokitiol-modified CS cement may be a potential root end filling material for clinic. - Highlights: • The hinokitiol-modified CS up-regulation of odontogenic of hDPCs. • Promoted proliferation of hDPCs on hinokitiol-modified CS. • The hinokitiol-modified CS cements not only inhibited the expression level of inflammatory cytokines, but also had better cytocompatibility. • The hinokitiol-modified CS up-regulation of odontogenic of hPDLs.

Physical characteristics, antimicrobial and odontogenesis potentials of calcium silicate cement containing hinokitiol

International Nuclear Information System (INIS)

Huang, Ming-Hsien; Shen, Yu-Fang; Hsu, Tuan-Ti; Huang, Tsui-Hsien; Shie, Ming-You

2016-01-01

Hinokitiol is a natural material and it has antibacterial and anti-inflammatory effects. The purpose of this study was to evaluate the material characterization, cell viability, antibacterial and anti-inflammatory abilities of the hinokitiol-modified calcium silicate (CS) cement as a root end filling material. The setting times, diametral tensile strength (DTS) values and XRD patterns of CS cements with 0–10 mM hinokitiol were examined. Then, the antibacterial effect and the expression levels of cyclooxygenase 2 (COX-2) and interleukin-1 (IL-1) of the hinokitiol-modified CS cements were evaluated. Furthermore, the cytocompatibility, the expression levels of the markers of odontoblastic differentiation, mineralized nodule formation and calcium deposition of human dental pulp cells (hDPCs) cultured on hinokitiol-modified CS cements were determined. The hinokitiol-modified CS cements had better antibacterial and anti-inflammatory abilities and cytocompatibility than non-modified CS cements. Otherwise, the hinokitiol-modified CS cements had suitable setting times and better odontoblastic potential of hDPCs. Previous report pointed out that the root-end filling materials may induce inflammatory cytokines reaction. In our study, hinokitiol-modified CS cements not only inhibited the expression level of inflammatory cytokines, but also had better cytocompatibility, antimicrobial properties and active ability of odontoblastic differentiation of hDPCs. Therefore, the hinokitiol-modified CS cement may be a potential root end filling material for clinic. - Highlights: • The hinokitiol-modified CS up-regulation of odontogenic of hDPCs. • Promoted proliferation of hDPCs on hinokitiol-modified CS. • The hinokitiol-modified CS cements not only inhibited the expression level of inflammatory cytokines, but also had better cytocompatibility. • The hinokitiol-modified CS up-regulation of odontogenic of hPDLs.

Comparative study on strength properties of cement mortar by partial replacement of cement with ceramic powder and silica fume

Science.gov (United States)

Himabindu, Ch.; Geethasri, Ch.; Hari, N.

2018-05-01

Cement mortar is a mixture of cement and sand. Usage of high amount of cement increases the consumption of natural resources and electric power. To overcome this problem we need to replace cement with some other material. Cement is replaced with many other materials like ceramic powder, silica fume, fly ash, granulated blast furnace slag, metakaolin etc.. In this research cement is replaced with ceramic powder and silica fume. Different combinations of ceramic powder and silica fume in cement were replaced. Cement mortar cubes of 1:3 grade were prepared. These cubes were cured under normal water for 7 days, 14days and 28 days. Compressive strength test was conducted for all mixes of cement mortar cubes.

Safety and function of a new clinical intracerebral microinjection instrument for stem cells and therapeutics examined in the Göttingen minipig

DEFF Research Database (Denmark)

Bjarkam, Carsten R; GLUD, AN; Margolin, Lee

2010-01-01

Safety and function of a new clinical intracerebral microinjection instrument for stem cells and therapeutics examined in the Göttingen minipig......Safety and function of a new clinical intracerebral microinjection instrument for stem cells and therapeutics examined in the Göttingen minipig...

Advanced cementation concepts

International Nuclear Information System (INIS)

Howard, C.G.

1989-10-01

The purpose of this programme of work was to investigate whether improvements could be made to existing formulations for cement suitable for the immobilization of intermediate level radioactive waste. Two additives were selected, microsilica and limestone flour. Improvements to the cement were only slight. (author)

Petroleum Sludge as gypsum replacement in cement plants: Its Impact on Cement Strength

Science.gov (United States)

Benlamoudi, Ali; Kadir, Aeslina Abdul; Khodja, Mohamed

2017-08-01

Due to high cost of cement manufacturing and the huge amount of resources exhaustion, companies are trying to incorporate alternative raw materials or by-products into cement production so as to produce alternative sustainable cement. Petroleum sludge is a dangerous waste that poses serious imparts on soil and groundwater. Given that this sludge contains a high percentage of anhydrite (CaSO4), which is the main component of gypsum (CaSO4.2H2O), it may play the same gypsum role in strength development. In this research, a total replacement of gypsum (100%) has been substituted by petroleum sludge in cement production and has led to an increase of 28.8% in UCS values after 28 curing days. Nevertheless, the burning of this waste has emitted a considerable amount of carbon monoxide (CO) gas that needs to be carefully considered prior to use petroleum sludge within cement plants.

Influence of Cement Particle-Size Distribution on Early Age Autogenous Strains and Stresses in Cement-Based Materials

DEFF Research Database (Denmark)

Bentz, Dale P.; Jensen, Ole Mejlhede; Hansen, Kurt Kielsgaard

2001-01-01

The influence of cement particle-size distribution on autogenous strains and stresses in cement pastes of identical water-to-cement ratios is examined for cement powders of four different finenesses. Experimental measurements include chemical shrinkage, to quantify degree of hydration; internal r...

Hypothermic manipulation of bone cement can extend the handling time during vertebroplasty

Directory of Open Access Journals (Sweden)

Lai Po-Liang

2012-10-01

Full Text Available Abstract Background Polymethylmethacrylate (PMMA is commonly used for clinical applications. However, the short handling time increases the probability of a surgeon missing the crucial period in which the cement maintains its ideal viscosity for a successful injection. The aim of this article was to illustrate the effects a reduction in temperature would have on the cement handling time during percutaneous vertebroplasty. Methods The injectability of bone cement was assessed using a cement compressor. By twisting the compressor, the piston transmits its axial load to the plunger, which then pumps the bone cement out. The experiments were categorized based on the different types of hypothermic manipulation that were used. In group I (room temperature, sham group, the syringes were kept at 22°C after mixing the bone cement. In group 2 (precooling the bone cement and the container, the PMMA powder and liquid, as well as the beaker, spatula, and syringe, were stored in the refrigerator (4°C overnight before mixing. In group 3 (ice bath cooling, the syringes were immediately submerged in ice water after mixing the bone cement at room temperature. Results The average liquid time, paste time, and handling time were 5.1 ± 0.7, 3.4 ± 0.3, and 8.5 ± 0.8 min, respectively, for group 1; 9.4 ± 1.1, 5.8 ± 0.5, and 15.2 ± 1.2 min, respectively, for group 2; and 83.8 ± 5.2, 28.8 ± 6.9, and 112.5 ± 11.3 min, respectively, for group 3. The liquid and paste times could be increased through different cooling methods. In addition, the liquid time (i.e. waiting time for ice bath cooling was longer than for that of the precooling method (p Conclusions Both precooling (i.e. lowering the initial temperature and ice bath cooling (i.e. lowering the surrounding temperature can effectively slow polymerization. Precooling is easy for clinical applications, while ice bath cooling might be more suitable for multiple-level vertebroplasty. Clinicians can take

Hypothermic manipulation of bone cement can extend the handling time during vertebroplasty.

Science.gov (United States)

Lai, Po-Liang; Tai, Ching-Lung; Chu, I-Ming; Fu, Tsai-Sheng; Chen, Lih-Huei; Chen, Wen-Jer

2012-10-16

Polymethylmethacrylate (PMMA) is commonly used for clinical applications. However, the short handling time increases the probability of a surgeon missing the crucial period in which the cement maintains its ideal viscosity for a successful injection. The aim of this article was to illustrate the effects a reduction in temperature would have on the cement handling time during percutaneous vertebroplasty. The injectability of bone cement was assessed using a cement compressor. By twisting the compressor, the piston transmits its axial load to the plunger, which then pumps the bone cement out. The experiments were categorized based on the different types of hypothermic manipulation that were used. In group I (room temperature, sham group), the syringes were kept at 22°C after mixing the bone cement. In group 2 (precooling the bone cement and the container), the PMMA powder and liquid, as well as the beaker, spatula, and syringe, were stored in the refrigerator (4°C) overnight before mixing. In group 3 (ice bath cooling), the syringes were immediately submerged in ice water after mixing the bone cement at room temperature. The average liquid time, paste time, and handling time were 5.1 ± 0.7, 3.4 ± 0.3, and 8.5 ± 0.8 min, respectively, for group 1; 9.4 ± 1.1, 5.8 ± 0.5, and 15.2 ± 1.2 min, respectively, for group 2; and 83.8 ± 5.2, 28.8 ± 6.9, and 112.5 ± 11.3 min, respectively, for group 3. The liquid and paste times could be increased through different cooling methods. In addition, the liquid time (i.e. waiting time) for ice bath cooling was longer than for that of the precooling method (p < 0.05). Both precooling (i.e. lowering the initial temperature) and ice bath cooling (i.e. lowering the surrounding temperature) can effectively slow polymerization. Precooling is easy for clinical applications, while ice bath cooling might be more suitable for multiple-level vertebroplasty. Clinicians can take advantage of the improved injectability without any

Cements in radioactive waste management. Characterization requirements of cement products for acceptance and quality assurance purposes

International Nuclear Information System (INIS)

Rahman, A.A.; Glasser, F.P.

1987-01-01

Cementitious materials are used as immobilizing matrices for low (LLW) and medium-level wastes (MLW) and are also components of the construction materials in the secondary barriers and the repositories. This report has concerned itself with a critical assessment of the quality assurance aspects of the immobilization and disposal of MLW and LLW cemented wastes. This report has collated the existing knowledge of the use and potential of cementitious materials in radioactive waste immobilization and highlighted the physico-chemical parameters. Subject areas include an assessment of immobilization objectives and cement as a durable material, waste stream and matrix characterization, quality assurance concepts, nature of cement-based systems, chemistry and modelling of cement hydration, role and effect of blending agents, radwaste-cement interaction, assessment of durability, degradative and radiolytic processes in cements and the behaviour of cement-based matrices and their near-field interactions with the environment and the repository conditions

Cementation of liquid radioactive waste

International Nuclear Information System (INIS)

Efremenkov, V.

2004-01-01

The cementation methods for immobilisation of radioactive wastes are discussed in terms of methodology, chemistry and properties of the different types of cements as well as the worldwide experience in this field. Two facilities for cementation - DEWA and MOWA - are described in details

Comparative study of nanomechanical properties of cements used in teeth restoration

International Nuclear Information System (INIS)

Peluccio, M S; Bignardi, C; Lombardo, S; Montevecchi, F M; Carossa, S

2007-01-01

The discipline of dental science includes the diagnosis of disease in the mouth and teeth, its manifestations and the procedures involved in the restoration of their integrity and function. Restoration of lost tooth structure with suitable materials plays an integral part in the successful rehabilitation of oral tissues. Several factors influence the performance of dental restorations. These factors include the type of cement used to bond crown restoration to prepared teeth. The nanoindentation method was used to explore the mechanical properties of different types of resin cement polymerized using different techniques. A Nano Indenter XP (from MTS Nano Instruments, USA) was used for the experimental tests. A sample of 40 extracted human teeth were restored using two different resin cements: Variolink II (Ivoclar Vivadent, Liechtenstein) and Venus A2 (Heraeus Kulzer, Germany). Both resin cements are light-cured and one of them is self-cured so that the degree of polymerization would be higher. The data obtained for nanohardness and the Young's modulus were analysed using ANOVA to evaluate the influence of different factors (the resin cement and polymerization technique used, the position on the tooth-restoration interface) and to determine the best performance for restoration. The results obtained could give a useful indication of the choice of cementation technique and of the materials used for the restoration of lost tooth structure in different clinical cases

Retention of long-term interim restorations with sodium fluoride enriched interim cement

Science.gov (United States)

Strash, Carolyn

Purpose: Interim fixed dental prostheses, or "provisional restorations", are fabricated to restore teeth when definitive prostheses are made indirectly. Patients undergoing extensive prosthodontic treatment frequently require provisionalization for several months or years. The ideal interim cement would retain the restoration for as long as needed and still allow for ease of removal. It would also avoid recurrent caries by preventing demineralization of tooth structure. This study aims to determine if adding sodium fluoride varnish to interim cement may assist in the retention of interim restorations. Materials and methods: stainless steel dies representing a crown preparation were fabricated. Provisional crowns were milled for the dies using CAD/CAM technology. Crowns were provisionally cemented onto the dies using TempBond NE and NexTemp provisional cements as well as a mixture of TempBond NE and Duraphat fluoride varnish. Samples were stored for 24h then tested or thermocycled for 2500 or 5000 cycles before being tested. Retentive strength of each cement was recorded using a universal testing machine. Results: TempBond NE and NexTemp cements performed similarly when tested after 24h. The addition of Duraphat significantly decreased the retention when added to TempBond NE. NexTemp cement had high variability in retention over all tested time periods. Thermocycling for 2500 and 5000 cycles significantly decreased the retention of all cements. Conclusions: The addition of Duraphat fluoride varnish significantly decreased the retention of TempBond NE and is therefore not recommended for clinical use. Thermocycling significantly reduced the retention of TempBond NE and NexTemp. This may suggest that use of these cements for three months, as simulated in this study, is not recommended.

Achievement of 900kgf/cm[sup 2] super workable high strength concrete with belite portland cement. (elevator building of cement silo in Chichibu cement). Part 1. ; Development of cement for super workable high strength concrete. Ko belite kei cement de 900kgf/cm[sup 2] wo tassei (Chichibu cement cement sairo no elevaor to). 1. ; Koryudo kokyodo concrete yo no cement no kaihatsu

Energy Technology Data Exchange (ETDEWEB)

Tanaka, M.; Fukaya, Y.; Nawa, T. (Chichibu Cement Co. Ltd., Tokyo (Japan))

1993-08-01

This paper describes the features of high belite Portland cement which can make the super workable high strength concrete, and the properties of concrete using this. The super workable concrete is required an excellent segregation resistance property as well as high flow property. Since the high belite Portland cement contains a small amount of C[sub 3]S in the clinker, the amounts of C[sub 3]A and C[sub 4]AF can be reduced without hindering the calcination of clinker. Additionally, since it contains a large amount of C[sub 2]S with low heat of hydration, an increase in the temperature of members can be suppressed. 'Chichibu High Flow Cement' having characteristics of this high belite Portland cement was developed for the super workable high strength concrete. The concrete using the High Flow Cement exhibited the maximum flow value of 70cm. It also exhibited the strength of 1,075 kgf/cm[sup 2] at the age of 91 days, and 1,100 kgf/cm[sup 2] at the age of 14 days under insulating. 4 refs., 8 figs., 2 tabs.

Cementation process study

International Nuclear Information System (INIS)

Park, H.H.; Han, K.W.; Ahn, S.J.; Choi, K.S.; Lee, M.W.; Ryu, Y.K.

1985-01-01

In the cementation process study, in 1984, design of the waste treatment simulator was finished for the first step. We can experience not only the operation of solidification system but the design and construction of comming large scale plant through the design of cementation process. (Author)

Compressive Strength and Physical Properties Behavior of Cement Mortars with addition of Cement Klin Dust

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Auday A Mehatlaf

2017-12-01

Full Text Available Cement Klin Dust (CKD was the waste of almost cement industry factories, so that in this paper utilization of CKD as filler in cement and/or concrete was the main objective. CKD from the Karbala cement factory had been used and analysis to know the chemical composition of the oxides was done. In this paper cement mortars with different weight percentages of CKD (0,5,10,20,30,40 had been prepared. Physical properties such as density and porosity were done in different age curing (3, 7, 28 day. In addition, mechanical properties included the coefficient of thermal conductivity and compressive strength had also observed with different age (3,7, and 28 for all prepared specimens. From the obtained the experimental results and their discussion, it was clear that the addition (20% of CKD had the good results in cement mortars.  

Cement Mason's Curriculum. Instructional Units.

Science.gov (United States)

Hendirx, Laborn J.; Patton, Bob

To assist cement mason instructors in providing comprehensive instruction to their students, this curriculum guide treats both the skills and information necessary for cement masons in commercial and industrial construction. Ten sections are included, as follow: related information, covering orientation, safety, the history of cement, and applying…

21 CFR 888.4200 - Cement dispenser.

Science.gov (United States)

2010-04-01

... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Cement dispenser. 888.4200 Section 888.4200 Food... DEVICES ORTHOPEDIC DEVICES Surgical Devices § 888.4200 Cement dispenser. (a) Identification. A cement dispenser is a nonpowered syringe-like device intended for use in placing bone cement (§ 888.3027) into...

[Significance of bone mineral density and modern cementing technique for in vitro cement penetration in total shoulder arthroplasty].

Science.gov (United States)

Pape, G; Raiss, P; Kleinschmidt, K; Schuld, C; Mohr, G; Loew, M; Rickert, M

2010-12-01

Loosening of the glenoid component is one of the major causes of failure in total shoulder arthroplasty. Possible risk factors for loosening of cemented components include an eccentric loading, poor bone quality, inadequate cementing technique and insufficient cement penetration. The application of a modern cementing technique has become an established procedure in total hip arthroplasty. The goal of modern cementing techniques in general is to improve the cement-penetration into the cancellous bone. Modern cementing techniques include the cement vacuum-mixing technique, retrograde filling of the cement under pressurisation and the use of a pulsatile lavage system. The main purpose of this study was to analyse cement penetration into the glenoid bone by using modern cement techniques and to investigate the relationship between the bone mineral density (BMD) and the cement penetration. Furthermore we measured the temperature at the glenoid surface before and after jet-lavage of different patients during total shoulder arthroplasty. It is known that the surrounding temperature of the bone has an effect on the polymerisation of the cement. Data from this experiment provide the temperature setting for the in-vitro study. The glenoid surface temperature was measured in 10 patients with a hand-held non-contact temperature measurement device. The bone mineral density was measured by DEXA. Eight paired cadaver scapulae were allocated (n = 16). Each pair comprised two scapulae from one donor (matched-pair design). Two different glenoid components were used, one with pegs and the other with a keel. The glenoids for the in-vitro study were prepared with the bone compaction technique by the same surgeon in all cases. Pulsatile lavage was used to clean the glenoid of blood and bone fragments. Low viscosity bone cement was applied retrogradely into the glenoid by using a syringe. A constant pressure was applied with a modified force sensor impactor. Micro-computed tomography

Impairment of resin cement application on the bond strength of indirect composite restorations

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Jovito Adiel SKUPIEN

2015-01-01

Full Text Available The aims of this study were to evaluate the effect of immediate and delayed resin cement application on the microtensile bond strength of indirect composite resin restorations and, to evaluate adhesive strategies (for regular resin cement or humidity parameters for self-adhesive resin cement. Forty-five enamel/dentin discs (0.5 mm height and 10 mm of diameter obtained from bovine teeth were divided into nine groups (n = 5. For regular cement, the variation factors were cementation technique at three levels (immediate cementation, 5 or 30 min after adhesive system application; and type of adhesive system at two levels (three- or two-step. For self-adhesive cement, the dentin moisture was the source of variation at three levels (normal, dry, or wet cementation. The specimens were submitted to microtensile bond strength (μTBS testing using a universal testing machine. Data were analyzed by ANOVA, Tukey’s test, and linear regression. Regular cement and three-step etch-and-rinse adhesive system showed the highest values of bond strength (25.21 MPa–30 min of delay. Only for this condition, three-step adhesive showed higher bond strength than the two-step adhesive. Nevertheless, the linear regression showed that irrespective of the strategy, the use of the two-step approach when compared with three-step adhesive system decreased μTBS (p < 0.001. The failure analysis showed predominant adhesive failures for all tested groups. All groups had comparable values of bond strength to bovine dentin when the same materials were used, even in suboptimal clinical conditions.

Development of cement material using inorganic additives

International Nuclear Information System (INIS)

Toyohara, Masumitsu; Satou, Tatsuaki; Wada, Mikio; Ishii, Tomoharu; Matsuo, Kazuaki.

1997-01-01

Inorganic admixtures to enhance the fluidity of cement material was developed. These admixtures turned into easy to immobilize the miscellaneous radioactive waste using cement material. It was found that the ζ potential of cement particles was directly proportional to the content of the inorganic admixtures in cement paste and the particles of cement were dispersed at the high ζ potential. The condensed sodium phosphate, which was the main component of the inorganic admixtures, retarded the dissolution of Ca 2+ ion from the cement, and generated the colloids by incorporating dissolved Ca 2+ ion. The cement material containing the inorganic admixtures was found to have the same mechanical strength and adsorption potential of radionuclides in comparison to normal cement materials. It was confirmed that the cement material containing the inorganic admixture was effectively filled gaps of miscellaneous radioactive waste. (author)

Cement Types, Composition, Uses and Advantages of Nanocement, Environmental Impact on Cement Production, and Possible Solutions

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S. P. Dunuweera

2018-01-01

Full Text Available We first discuss cement production and special nomenclature used by cement industrialists in expressing the composition of their cement products. We reveal different types of cement products, their compositions, properties, and typical uses. Wherever possible, we tend to give reasons as to why a particular cement type is more suitable for a given purpose than other types. Cement manufacturing processes are associated with emissions of large quantities of greenhouse gases and environmental pollutants. We give below quantitative and qualitative analyses of environmental impact of cement manufacturing. Controlling pollution is a mandatory legal and social requirement pertinent to any industry. As cement industry is one of the biggest CO2 emitters, it is appropriate to discuss different ways and means of CO2 capture, which will be done next. Finally, we give an account of production of nanocement and advantages associated with nanocement. Nanofillers such as nanotitania, nanosilica, and nanoalumina can be produced in large industrial scale via top-down approach of reducing size of naturally available bulk raw materials to those in the nanorange of 1 nm–100 nm. We mention the preparation of nanotitania and nanosilica from Sri Lankan mineral sands and quartz deposits, respectively, for the use as additives in cement products to improve performance and reduce the amount and cost of cement production and consequent environmental impacts. As of now, mineral sands and other treasures of minerals are exported without much value addition. Simple chemical modifications or physical treatments would add enormous value to these natural materials. Sri Lanka is gifted with highly pure quartz and graphite from which silica and graphite nanoparticles, respectively, can be prepared by simple size reduction processes. These can be used as additives in cements. Separation of constituents of mineral sands is already an ongoing process.

Clinical Trial Design for Testing the Stem Cell Model for the Prevention and Treatment of Cancer

International Nuclear Information System (INIS)

Reddy, Rishindra M.; Kakarala, Madhuri; Wicha, Max S.

2011-01-01

The cancer stem cell model introduces new strategies for the prevention and treatment of cancers. In cancers that appear to follow the stem cell model, pathways such as Wnt, Notch and Hedgehog may be targeted with natural compounds such as curcumin or drugs to reduce the risk of initiation of new tumors. Disease progression of established tumors could also potentially be inhibited by targeting the tumorigenic stem cells alone, rather than aiming to reduce overall tumor size. These new approaches mandate a change in the design of clinical trials and biomarkers chosen for efficacy assessment for preventative, neoadjuvant, adjuvant, and palliative treatments. Cancer treatments could be evaluated by assessing stem cell markers before and after treatment. Targeted stem cell specific treatment of cancers may not result in “complete” or “partial” responses radiologically, as stem cell targeting may not reduce the tumor bulk, but eliminate further tumorigenic potential. These changes are discussed using breast, pancreatic, and lung cancer as examples

Clinical Trial Design for Testing the Stem Cell Model for the Prevention and Treatment of Cancer

Energy Technology Data Exchange (ETDEWEB)

Reddy, Rishindra M., E-mail: reddyrm@med.umich.edu [Medical Center, University of Michigan, 1500 E. Medical Center Drive, 2120 Taubman Center, Ann Arbor, MI 48109 (United States); Kakarala, Madhuri; Wicha, Max S. [Comprehensive Cancer Center, University of Michigan, 1500 E. Medical Center Drive, Ann Arbor, MI 48109 (United States)

2011-06-20

The cancer stem cell model introduces new strategies for the prevention and treatment of cancers. In cancers that appear to follow the stem cell model, pathways such as Wnt, Notch and Hedgehog may be targeted with natural compounds such as curcumin or drugs to reduce the risk of initiation of new tumors. Disease progression of established tumors could also potentially be inhibited by targeting the tumorigenic stem cells alone, rather than aiming to reduce overall tumor size. These new approaches mandate a change in the design of clinical trials and biomarkers chosen for efficacy assessment for preventative, neoadjuvant, adjuvant, and palliative treatments. Cancer treatments could be evaluated by assessing stem cell markers before and after treatment. Targeted stem cell specific treatment of cancers may not result in “complete” or “partial” responses radiologically, as stem cell targeting may not reduce the tumor bulk, but eliminate further tumorigenic potential. These changes are discussed using breast, pancreatic, and lung cancer as examples.

The effect of a nano-filled resin coating on the 3-year clinical performance of a conventional high-viscosity glass-ionomer cement.

Science.gov (United States)

Diem, Vu Thi Kieu; Tyas, Martin J; Ngo, Hien C; Phuong, Lam Hoai; Khanh, Ngo Dong

2014-04-01

The main aim of the study was to compare the clinical performance of the conventional high-powder/liquid ratio glass-ionomer cement (GIC) Fuji IX GP Extra (F IX), Fuji IX GP Extra with a low-viscosity nano-filled resin coating, G-Coat Plus (F IX+GCP), and a resin composite, Solare (S), as a comparison material. Moderate-depth occlusal cavities in the first permanent molars of 91 11-12-year-old children (1-4 restorations per child) were restored with either F IX (87 restorations), F IX+GCP (84 restorations) or S (83 restorations). Direct clinical assessment, photographic assessment and assessment of stone casts of the restorations were carried out at 6 months, 1 year, 2 years and 3 years. The colour match with the tooth of the GIC restorations improved over the 3 years of the study. Marginal staining and marginal adaptation were minimal for all restorations; three restorations exhibited secondary caries at 3 years. From the assessment of the casts, at 2 years, there was significantly less wear of the F IX GP Extra+GCP restorations than the F IX GP Extra restorations (P G-Coat Plus showed acceptable clinical performance in occlusal cavities in children, the application of G-Coat Plus gave some protection against wear. The application of G-Coat Plus to Fuji IX GP Extra glass-ionomer cement may be beneficial in reducing wear in occlusal cavities.

[Bioethical challenges of stem cell tourism].

Science.gov (United States)

Ventura-Juncá, Patricio; Erices, Alejandro; Santos, Manuel J

2013-08-01

Stem cells have drawn extraordinary attention from scientists and the general public due to their potential to generate effective therapies for incurable diseases. At the same time, the production of embryonic stem cells involves a serious ethical issue concerning the destruction of human embryos. Although adult stem cells and induced pluripotential cells do not pose this ethical objection, there are other bioethical challenges common to all types of stem cells related particularly to the clinical use of stem cells. Their clinical use should be based on clinical trials, and in special situations, medical innovation, both of which have particular ethical dimensions. The media has raised unfounded expectations in patients and the public about the real clinical benefits of stem cells. At the same time, the number of unregulated clinics is increasing around the world, making direct offers through Internet of unproven stem cell therapies that attract desperate patients that have not found solutions in standard medicine. This is what is called stem cells tourism. This article reviews this situation, its consequences and the need for international cooperation to establish effective regulations to prevent the exploitation of patients and to endanger the prestige of legitimate stem cell research.

Effects of the super plasticizers and the water/cement ratio on the mini-slump of Portland cement pastes

International Nuclear Information System (INIS)

Meirelles, J.R.; Morelli, A.C.; Baldo, J.B.

1998-01-01

The rheology of Portland cement concrete is dominated by the cement paste rheology. In general the rheological behavior of cement pastes is evaluated by means of the mini-slump test. In the present paper it was investigated the effect of the water/cement ratio was as of two types of superplasticizers (melamine and naftalen based) on the mini-slump of pastes of common cement pastes. (author)

Influence of Temporary Cements on the Bond Strength of Self-Adhesive Cement to the Metal Coronal Substrate.

Science.gov (United States)

Peixoto, Raniel Fernandes; De Aguiar, Caio Rocha; Jacob, Eduardo Santana; Macedo, Ana Paula; De Mattos, Maria da Gloria Chiarello; Antunes, Rossana Pereira de Almeida

2015-01-01

This research evaluated the influence of temporary cements (eugenol-containing [EC] or eugenol-free [EF]) on the tensile strength of Ni-Cr copings fixed with self-adhesive resin cement to the metal coronal substrate. Thirty-six temporary crowns were divided into 4 groups (n=9) according to the temporary cements: Provy, Dentsply (eugenol-containing), Temp Cem, Vigodent (eugenol-containing), RelyX Temp NE, 3M ESPE (eugenol-free) and Temp Bond NE, Kerr Corp (eugenol-free). After 24 h of temporary cementation, tensile strength tests were performed in a universal testing machine at a crosshead speed of 0.5 mm/min and 1 kN (100 kgf) load cell. Afterwards, the cast metal cores were cleaned by scraping with curettes and air jet. Thirty-six Ni-Cr copings were cemented to the cast metal cores with self-adhesive resin cement (RelyX U200, 3M ESPE). Tensile strength tests were performed again. In the temporary cementation, Temp Bond NE (12.91 ± 2.54) and Temp Cem (12.22 ± 2.96) presented the highest values of tensile strength and were statistically similar to each other (p>0.05). Statistically significant difference (pcementation of Ni-Cr copings with self-adhesive resin cement. In addition, Temp Cem (120.68 ± 48.27) and RelyX Temp NE (103.04 ± 26.09) showed intermediate tensile strength values. In conclusion, the Provy eugenol-containing temporary cement was associated with the highest bond strength among the resin cements when Ni-Cr copings were cemented to cast metal cores. However, the eugenol cannot be considered a determining factor in increased bond strength, since the other tested cements (1 eugenol-containing and 2 eugenol-free) were similar.

Research gaps identified during systematic reviews of clinical trials: glass-ionomer cements

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Mickenautsch Steffen

2012-06-01

Full Text Available Abstract Background To report the results of an audit concerning research gaps in clinical trials that were accepted for appraisal in authored and published systematic reviews regarding the application of glass-ionomer cements (GIC in dental practice Methods Information concerning research gaps in trial precision was extracted, following a framework that included classification of the research gap reasons: ‘imprecision of information (results’, ‘biased information’, ‘inconsistency or unknown consistency’ and ‘not the right information’, as well as research gap characterization using PICOS elements: population (P, intervention (I, comparison (C, outcomes (O and setting (S. Internal trial validity assessment was based on the understanding that successful control for systematic error cannot be assured on the basis of inclusion of adequate methods alone, but also requires empirical evidence about whether such attempt was successful. Results A comprehensive and interconnected coverage of GIC-related clinical topics was established. The most common reasons found for gaps in trial precision were lack of sufficient trials and lack of sufficient large sample size. Only a few research gaps were ascribed to ‘Lack of information’ caused by focus on mainly surrogate trial outcomes. According to the chosen assessment criteria, a lack of adequate randomisation, allocation concealment and blinding/masking in trials covering all reviewed GIC topics was noted (selection- and detection/performance bias risk. Trial results appear to be less affected by loss-to-follow-up (attrition bias risk. Conclusion This audit represents an adjunct of the systematic review articles it has covered. Its results do not change the systematic review’s conclusions but highlight existing research gaps concerning the precision and internal validity of reviewed trials in detail. These gaps should be addressed in future GIC-related clinical research.

Rietveld analysis, powder diffraction and cement

International Nuclear Information System (INIS)

Peterson, V.

2002-01-01

Full text: Phase quantification of cement is essential in its industrial use, however many methods are inaccurate and/or time consuming. Powder diffraction is one of the more accurate techniques used for quantitative phase analysis of cement. There has been an increase in the use of Rietveld refinement and powder diffraction for the analysis and phase quantification of cement and its components in recent years. The complex nature of cement components, existence of solid solutions, polymorphic variation of phases and overlapping phase peaks in diffraction patterns makes phase quantification of cements by powder diffraction difficult. The main phase in cement is alite, a solid solution of tricalcium silicate. Tricalcium silicate has been found to exist in seven modifications in three crystal systems, including triclinic, monoclinic, and rhombohedral structures. Hence, phase quantification of cements using Rietveld methods usually involves the simultaneous modelling of several tricalcium silicate structures to fit the complex alite phase. An industry ordinary Portland cement, industry and standard clinker, and a synthetic tricalcium silicate were characterised using neutron, laboratory x-ray and synchrotron powder diffraction. Diffraction patterns were analysed using full-profile Rietveld refinement. This enabled comparison of x-ray, neutron and synchrotron data for phase quantification of the cement and examination of the tricalcium silicate. Excellent Rietveld fits were achieved, however the results showed that the quantitative phase analysis results differed for some phases in the same clinker sample between various data sources. This presentation will give a short introduction about cement components including polymorphism, followed by the presentation of some problems in phase quantification of cements and the role of Rietveld refinement in solving these problems. Copyright (2002) Australian X-ray Analytical Association Inc

76 FR 50252 - Gray Portland Cement and Cement Clinker From Japan; Scheduling of an Expedited Five-Year Review...

Science.gov (United States)

2011-08-12

... INTERNATIONAL TRADE COMMISSION [Investigation No. 731-TA-461 (Third Review)] Gray Portland Cement and Cement Clinker From Japan; Scheduling of an Expedited Five-Year Review Concerning the Antidumping Duty Order on Gray Portland Cement and Cement Clinker From Japan AGENCY: United States International...

Biocompatibility of Portland cement combined with different radiopacifying agents.

Science.gov (United States)

Lourenço Neto, Natalino; Marques, Nádia C T; Fernandes, Ana Paula; Rodini, Camila O; Duarte, Marco A H; Lima, Marta C; Machado, Maria A A M; Abdo, Ruy C C; Oliveira, Thais M

2014-03-01

The aim of this study was to evaluate the response of rat subcutaneous tissue to Portland cement combined with two different radiopacifying agents, iodoform (CHI3) and zirconium oxide (ZrO2). These materials were placed in polyethylene tubes and implanted into the dorsal connective tissue of Wistar rats for 7 and 15 days. The specimens were then stained with hematoxylin and eosin, and inflammatory reaction parameters were evaluated by light microscopy. The intensity of the inflammatory response to the sealants was analyzed by two blind calibrated observers throughout the experimental period. Histological analysis showed that all the materials caused a moderated inflammatory reaction at 7 days, which then diminished with time. At 15 days, the inflammatory reaction was almost absent, and fibroblasts and collagen fibers were observed indicating normal tissue healing. The degrees of the inflammatory reaction on different days throughout the experimental period were compared using the non-parametric Kruskal-Wallis test. Statistical analysis demonstrated no significant differences amongst the groups, and Portland cement associated with radiopacifying agents gave satisfactory results. Therefore, Portland cement used in combination with radiopacifying agents can be considered a biocompatible material. Although our results are very encouraging, further studies are needed in order to establish safe clinical indications for Portland cement combined with radiopacifying agents.

Effect of ultrasonic instrumentation on the bond strength of crowns cemented with zinc phosphate cement to natural teeth. An in vitro study

Directory of Open Access Journals (Sweden)

Antonio Braulino de Melo Filho

2008-09-01

Full Text Available Several studies have reported the benefits of sonic and/or ultrasonic instrumentation for root debridement, with most of them focusing on changes in periodontal clinical parameters. The present study investigated possible alterations in the tensile bond strength of crowns cemented with zinc phosphate cement to natural teeth after ultrasonic instrumentation. Forty recently extracted intact human third molars were selected, cleaned and stored in physiologic serum at 4°C. They received standard preparations, at a 16º convergence angle, and AgPd alloy crowns. The crowns were cemented with zinc phosphate cement and then divided into four groups of 10 teeth each. Each group was then subdivided into two subgroups, with one of the subgroups being submitted to 5,000 thermal cycles ranging from 55 ± 2 to 5 ± 2°C, while the other was not. Each group was submitted to ultrasonic instrumentation for different periods of time: group 1 - 0 min (control, group 2 - 5 min, group 3 - 10 min, and group 4 - 15 min. Tensile bond strength tests were performed with an Instron testing machine (model 4310. Statistical analysis was performed using ANOVA and Tukey's test at the 5% level of significance. A significant reduction in the tensile bond strength of crowns cemented with zinc phosphate and submitted to thermal cycles was observed at 15 min (196.75 N versus 0 min = 452.01 N, 5 min = 444.23 N and 10 min = 470.85 N. Thermal cycling and ultrasonic instrumentation for 15 min caused a significant reduction in tensile bond strength (p < .05.

Biomedical and Clinical Promises of Human Pluripotent Stem Cells for Neurological Disorders

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Nopporn Jongkamonwiwat

2013-01-01

Full Text Available Neurological disorders are characterized by the chronic and progressive loss of neuronal structures and functions. There is a variability of the onsets and causes of clinical manifestations. Cell therapy has brought a new concept to overcome brain diseases, but the advancement of this therapy is limited by the demands of specialized neurons. Human pluripotent stem cells (hPSCs have been promised as a renewable resource for generating human neurons for both laboratory and clinical purposes. By the modulations of appropriate signalling pathways, desired neuron subtypes can be obtained, and induced pluripotent stem cells (iPSCs provide genetically matched neurons for treating patients. These hPSC-derived neurons can also be used for disease modeling and drug screening. Since the most urgent problem today in transplantation is the lack of suitable donor organs and tissues, the derivation of neural progenitor cells from hPSCs has opened a new avenue for regenerative medicine. In this review, we summarize the recent reports that show how to generate neural derivatives from hPSCs, and discuss the current evidence of using these cells in animal studies. We also highlight the possibilities and concerns of translating these hPSC-derived neurons for biomedical and clinical uses in order to fight against neurological disorders.

A Study on the Manufacturing Properties of Crack Self-Healing Capsules Using Cement Powder for Addition to Cement Composites

OpenAIRE

Choi, Yun-Wang; Oh, Sung-Rok; Choi, Byung-Keol

2017-01-01

We fabricated crack self-healing capsules using cement powder for mixing into cement composites and evaluated the properties of the capsule manufacturing process in this study. The manufacture of the self-healing capsules is divided into core production processing of granulating cement in powder form and a coating process for creating a wall on the surfaces of the granulated cement particles. The produced capsules contain unhardened cement and can be mixed directly with the cement composite m...

Cement replacement materials. Properties, durability, sustainability

International Nuclear Information System (INIS)

Ramezanianpour, Ali Akbar

2014-01-01

The aim of this book is to present the latest findings in the properties and application of Supplementary Cementing Materials and blended cements currently used in the world in concrete. Sustainability is an important issue all over the world. Carbon dioxide emission has been a serious problem in the world due to the greenhouse effect. Today many countries agreed to reduce the emission of CO2. Many phases of cement and concrete technology can affect sustainability. Cement and concrete industry is responsible for the production of 7% carbon dioxide of the total world CO2 emission. The use of supplementary cementing materials (SCM), design of concrete mixtures with optimum content of cement and enhancement of concrete durability are the main issues towards sustainability in concrete industry.

Characterization of monolith block of spent resin cementation

International Nuclear Information System (INIS)

Prayitno; Endro-Kismolo; Isman MT

1996-01-01

Spent resin immobilization process with cement was done to prevent release of radionuclide in the ultimate storage or disposal. The varied Composition of water/cement ratio in the cementation process were 0.3; 0.4; 0.5 and the various weight of resin waste are 25 g, 37.5 g and 50 gram. The compressive strength of the various water/cement ratio without spent resin was bigger than 0.3. This investigation proved that the compressive strength of Tiga Roda cement was bigger than those of Gresik cement or Nusantara cement. The compressive of the cement block of were the spent resin cementation was influenced by the water/cement ratio and the total spent resin addition. The best condition reached at the water/cement ratio of 0.3 and 25 gram spent resin, was compressive strength of 17.86 N/mm 2 . Leaching rate of the various weight composition of spent resin cementation for 91 days were between 10 -2 - 10 -4 gram.cm -2 .day -1

Setting time and flowability of accelerated Portland cement mixed with polycarboxylate superplasticizer.

Science.gov (United States)

Wongkornchaowalit, Norachai; Lertchirakarn, Veera

2011-03-01

Important limitations of mineral trioxide aggregate for use in clinical procedures are extended setting time and difficult handling characteristics. The removal of gypsum at the end stage of the Portland cement manufacturing process and polycarboxylate superplasticizer admixture may solve these limitations. Different concentrations of polycarboxylate superplasticizer (0%, 1.2%, 1.8%, and 2.4% by volume) and liquid-to-powder ratios (0.27, 0.30, and 0.33 by weight) were mixed with white Portland cement without gypsum (AWPC-experimental material). Type 1 ordinary white Portland cement mixed with distilled water at the same ratios as the experimental material was used as controls. All samples were tested for setting time and flowability according to the International Organization for Standardization 6876:2001 guideline. The data were analyzed by two-way analysis of variance. Then, one-way analysis of variance and multiple comparison tests were used to analyze the significance among groups. The data are presented in mean ± standard deviation values. In all experimental groups, the setting times were in the range of 4.2 ± 0.4 to 11.3 ± 0.2 minutes, which were significantly (p setting time and increased flowability of cement, which would be beneficial for clinical use. Copyright © 2011 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

A Study on the Manufacturing Properties of Crack Self-Healing Capsules Using Cement Powder for Addition to Cement Composites

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Yun-Wang Choi

2017-01-01

Full Text Available We fabricated crack self-healing capsules using cement powder for mixing into cement composites and evaluated the properties of the capsule manufacturing process in this study. The manufacture of the self-healing capsules is divided into core production processing of granulating cement in powder form and a coating process for creating a wall on the surfaces of the granulated cement particles. The produced capsules contain unhardened cement and can be mixed directly with the cement composite materials because they are protected from moisture by the wall material. Therefore, the untreated cement is present in the form of a capsule within the cement composite, and hydration can be induced by moisture penetrating the crack surface in the event of cracking. In the process of granulating the cement, it is important to obtain a suitable consistency through the kneading agent and to maintain the moisture barrier performance of the wall material. We can utilize the results of this study as a basis for advanced self-healing capsule technology for cement composites.

Effect of modified cementation technique on marginal fit and apical spread of excess cement for implant restorations: An in vitro study

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Brijesh Patel

2016-01-01

Full Text Available Aim: To investigate and compare the vertical marginal discrepancy and spread of excess cement after cementation with modified cementation technique and conventional technique. Materials and Methods: Ten implant analogs with prefabricated standard abutments of similar dimensions were mounted individually in self-cure acrylic blocks subcrestally. Forty ideal metal coping specimens were prepared by conventional lost wax technique. Measurement of the marginal discrepancy at the implant-crown interface was done using a stereomicroscope before cementation. Abutment replicas (ARs were prepared for twenty specimens using cast copings and pattern resin. All forty copings were cemented according to the following cementation techniques and cement types, with ten specimens in each group. (1 Group 1: Half filling (HF cementation technique using provisional cement. (2 Group 2: HF cementation technique using permanent cement. (3 Group 3: AR technique using provisional cement. (4 Group 4: AR technique using permanent cement. Specimens were subjected to measurement of marginal discrepancy and spread of excess cement using stereomicroscope after cementation procedure. Data were analyzed using paired t-test and unpaired t-test. Results: AR technique showed significantly less marginal discrepancy (P = 0.000 and apical spread of excess cement (P = 0.002 than conventional HF technique. Provisional cement showed significantly more marginal discrepancy (HF-P = 0.000 and AR-P = 0.001 and less apical spread of excess cement (HF-P = 0.023 and AR-P = 0.002 and among both technique. Statistical Analysis: Unpaired t-test. Conclusion: An alternative technique of using AR is effective technique to prevent peri-implant diseases.

A cement based syntactic foam

International Nuclear Information System (INIS)

Li Guoqiang; Muthyala, Venkata D.

2008-01-01

In this study, a cement based syntactic foam core was proposed and experimentally investigated for composite sandwich structures. This was a multi-phase composite material with microballoon dispersed in a rubber latex toughened cement paste matrix. A trace amount of microfiber was also incorporated to increase the number of mechanisms for energy absorption and a small amount of nanoclay was added to improve the crystal structure of the hydrates. Three groups of cement based syntactic foams with varying cement content were investigated. A fourth group of specimens containing pure cement paste were also prepared as control. Each group contained 24 beam specimens. The total number of beam specimens was 96. The dimension of each beam was 30.5 cm x 5.1 cm x 1.5 cm. Twelve foam specimens from each group were wrapped with plain woven 7715 style glass fabric reinforced epoxy to prepare sandwich beams. Twelve cubic foam specimens, three from each group, with a side length of 5.1 cm, were also prepared. Three types of testing, low velocity impact test and four-point bending test on the beam specimens and compression test on the cubic specimens, were conducted to evaluate the impact energy dissipation, stress-strain behavior, and residual strength. Scanning electron microscope (SEM) was also used to examine the energy dissipation mechanisms in the micro-length scale. It was found that the cement based syntactic foam has a higher capacity for dissipating impact energy with an insignificant reduction in strength as compared to the control cement paste core. When compared to a polymer based foam core having similar compositions, it was found that the cement based foam has a comparable energy dissipation capacity. The developed cement based syntactic foam would be a viable alternative for core materials in impact-tolerant composite sandwich structures

Equally good fixation of cemented and uncemented cups in total trapeziometacarpal joint prostheses. A randomized clinical RSA study with 2-year follow-up.

Science.gov (United States)

Hansen, Torben Baek; Stilling, Maiken

2013-02-01

Cup failure is a recognized problem in total trapeziometacarpal (TM) joint prostheses; it may be related to poor fixation, which can be revealed by radiostereometric analysis (RSA). We compared the early implant migration of cemented trapezium cups to that of uncemented screw cups. In a prospective, parallel-group, randomized patient-blinded clinical trial, we included 32 hands in 28 patients (5 males) with a mean age of 58 (40-77) years and with Eaton stage-2 or -3 osteoarthritis of the trapeziometacarpal joint. Patients were randomized to surgery with a cemented DLC all-polyethylene cup (C) (n = 16) or an uncemented hydroxyapatite-coated chrome-cobalt Elektra screw cup (UC) (n = 16). Uncemented cups were inserted without threading of the bone. Stereoradiographs for evaluation of cup migration (primary effect size) and DASH and pain scores were obtained during 2 years of follow-up. The 2-year total translation (TT) was similar (p = 0.2): 0.24 mm (SD 0.10) for the C (n = 11) and 0.19 mm (SD 0.16) for the UC (n = 11). Variances were similar (p = 0.4). Judged by RSA, 2 UC cups and 1 C cup became loose (TT > 1 mm). Both UC cups were found to be loose at revision. Grip strength, pain, and DASH scores were similar between groups at all measurement points. Early implant fixation and clinical outcome were equally good with both cup designs. This is the first clinical RSA study on trapezium cups, and the method appears to be clinically useful for detection of loose implants.

Effect of different resin luting cements on the marginal fit of lithium disilicate pressed crowns.

Science.gov (United States)

Mounajjed, Radek; Salinas, Thomas J; Ingr, Tomas; Azar, Basel

2017-11-15

The vertical marginal discrepancy of restorations can increase upon cementation, and poor marginal fit can lead to cement dissolution, marginal discoloration, microleakage, and secondary caries. The amount of increase is related to the type of luting cement used, but how lithium disilicate pressed crowns are affected by different resin cements is unclear. The purpose of this in vitro study was to compare the effect of using different resin luting cements on the vertical marginal discrepancy of lithium disilicate pressed crowns. A total of 18 intact extracted mandibular third molars were disinfected in a solution of 10% formalin for 7 days and were then prepared to receive a ceramic crown. Impressions were made with polyvinyl siloxane and lithium disilicate pressed crowns made and cemented with 1 of 3 resin luting cements. The marginal discrepancy was measured at 4 points on the finishing line of each tooth, with optical microscopy at ×200 magnification before and after cementation. Statistical analysis was done with the Kruskal-Wallis test to compare the median marginal increase among the 3 groups. The least amount of marginal increase after cementation was with Harvard PremiumFlow cement, with an average marginal increase of 42 ±11 μm. RelyX Ultimate cement increased the margins by an average 45 ±29 μm. The highest marginal increase was found in the Enamel Plus HRi preheated composite resin group (116 ±47 μm). The marginal increase of pressed crowns cemented with preheated composite resin (Enamel Plus HRi) exceeded the clinically acceptable range of marginal discrepancy. Copyright © 2017 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

A Clinical Indications Prediction Scale Based on TWIST1 for Human Mesenchymal Stem Cells

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Siddaraju V. Boregowda

2016-02-01

Full Text Available In addition to their stem/progenitor properties, mesenchymal stem cells (MSCs also exhibit potent effector (angiogenic, antiinflammatory, immuno-modulatory functions that are largely paracrine in nature. It is widely believed that effector functions underlie most of the therapeutic potential of MSCs and are independent of their stem/progenitor properties. Here we demonstrate that stem/progenitor and effector functions are coordinately regulated at the cellular level by the transcription factor Twist1 and specified within populations according to a hierarchical model. We further show that manipulation of Twist1 levels by genetic approaches or by exposure to widely used culture supplements including fibroblast growth factor 2 (Ffg2 and interferon gamma (IFN-gamma alters MSC efficacy in cell-based and in vivo assays in a predictable manner. Thus, by mechanistically linking stem/progenitor and effector functions our studies provide a unifying framework in the form of an MSC hierarchy that models the functional complexity of populations. Using this framework, we developed a CLinical Indications Prediction (CLIP scale that predicts how donor-to-donor heterogeneity and culture conditions impact the therapeutic efficacy of MSC populations for different disease indications.

Radioactivity of bone cement

International Nuclear Information System (INIS)

Scherer, M.A.; Winkler, R.; Ascherl, R.; Lenz, E.

1993-01-01

A total of 14 samples of different types of bone cement from five different manufacturers were examined for their radioactivity. Each of the investigated bone cements showed a low radioactivity level, i.e. between [de

Production of portland cement using Moroccan oil shale and comparative study between conventional cement plant and cement plant using oil shale

International Nuclear Information System (INIS)

Doumbouya, M.; Kacemi, K.E.; Kitane, S.

2012-01-01

Like the use of coal ash from power plants as an addition to cement, oil shale are used for cement production on an industrial scale in Estonia, China, USA and Germany. Oil shale can be utilized in manufacturing the cement. In addition to the utilization of these by-products after combustion, it can also reduce the required temperature for the clinkering reactions during the production of Portland clinker. We performed a study on the Moroccan oil shale to maximize the use of oil shale ash in the manufacturing of Portland cement. We found that Moroccan oil shale ash can be used up to 30% with 70% Portland clinker without altering its principle properties. The corresponding temperature required to generate the required liquid for the clinkering reactions as well as the essential ingredients for clinker was found to be around 850 to 1000 deg. C. The operating temperatures for this optimized blend ratio were found to 1000 deg. C. The resulting Portland clinker from this ratio will need further testing in accordance with international standards for Portland cement to examine properties like strength and setting time. (author)

Reducing cement's CO2 footprint

Science.gov (United States)

van Oss, Hendrik G.

2011-01-01

The manufacturing process for Portland cement causes high levels of greenhouse gas emissions. However, environmental impacts can be reduced by using more energy-efficient kilns and replacing fossil energy with alternative fuels. Although carbon capture and new cements with less CO2 emission are still in the experimental phase, all these innovations can help develop a cleaner cement industry.

Through BHA (Bottom Hole Assembly) cementing with proprietary cementing technology

Energy Technology Data Exchange (ETDEWEB)

Fanguy, Charles ' Joey' ; Mueller, Dan T. [BJ Services Company, Houston, TX (United States); Garrett, J.C. [Palm Energy Partners, LLC, Metairie, LA (United States)

2004-07-01

There are many problems that can arise when drilling into sub-normally pressured or naturally fractured zones. Lost circulation is one problem that is commonly encountered while drilling oil and gas wells. Lost circulation can lead to increased costs associated with drilling due to rig time, spreadsheet costs, and expensive mud system losses. Cement is one of the most effective treatment options, although it is not normally considered the first option because most operators are forced to trip out of the wellbore and utilize a squeeze packer. This is not always a viable option because of potential well control issues associated with the hydrostatic pressure reduction due to the losses of the whole mud. One treatment option that is commonly overlooked is pumping cement slurries through the bottom hole assembly and drill bit. This is generally not attempted for a variety of reasons. These reasons include: I Concern about 'squeezing off' of the cement in the bit II Lack of potential quality control associated with mixing 'on the fly' III Lack of the ability to test the actual mixed slurry samples The use of a pre-mixed, storable cement slurry has eliminated the concerns associated with pumping cement slurries through mud motors, MWD tools, BHA's, and drill bits. This advanced cement technology has been successfully utilized while reducing the risks associated with these lost circulation treatments. In addition, this technology has eliminated the costs associated with using a squeeze packer and the rig time required for several trips out of the wellbore. The paper will describe the premixed slurry properties and QA/QC procedures that are required for successful through the bit operations. This paper will also provide case histories of successful through the bit operation, as well as background information leading to the treatments. The case histories include successful through the bit remediation of severe lost circulation zones and as well the

Cementation of the solid radioactive waste with polymer-cement solutions using the method of impregnation

International Nuclear Information System (INIS)

Gorbunova, O.

2015-01-01

Cementation of solid radioactive waste (SRW), i.e. inclusion of solid radioactive waste into cement matrix without cavities - is one of the main technological processes used for conditioning low and intermediate level radioactive waste. At FSUE 'Radon' the industrialized method of impregnation has been developed and since 2003 has been using for cementation of solid radioactive waste. The technology is that the polymer-cement solution, having high penetrating properties, is supplied under pressure through a tube to the bottom of the container in which solid radioactive waste has preliminarily been placed. The polymer-cement solution is evenly moving upwards through the channels between the particles of solid radioactive waste, fills the voids in the bulk volume of the waste and hardens, forming a cement compound, the amount of which is equal to the original volume. The aim of the investigation was a selection of a cement solution suitable for SRW impregnation (including fine particles) without solution depletion and bottom layers stuffing. It has been chosen a polymer: PHMG (polyhexamethylene-guanidine), which is a stabilizing and water-retaining component of the cement solution. The experiments confirm that the polymer increases the permeability of the cement solution by a 2-2.5 factor, the viscosity by a 1.2 factor, the stability of the consistency by a 1.5-1.7 factor, and extends the operating range of the W/C ratio to 0.5-1.1. So it is possible to penetrate a volume of SRW bigger by a 1.5-2.0 factor. It has been proved, that PHMG polymer increases strength and frost-resistance of the final compounds by a 1.8-2.7 factor, and contributes to fast strength development at the beginning of hardening and it decreases Cs-137 leashing rate by a 1.5-2 factor

Comparison of modified sulfur cement and hydraulic cement for encapsulation of radioactive and mixed wastes

International Nuclear Information System (INIS)

Kalb, P.D.; Heiser, J.H. III; Colombo, P.

1990-01-01

The majority of solidification/stabilization systems for low-level radioactive waste (LLW) and mixed waste, both in the commercial sector and at Department of Energy (DOE) facilities, utilize hydraulic cement (such as portland cement) to encapsulate waste materials and yield a monolithic solid waste form for disposal. Because hydraulic cement requires a chemical hydration reaction for setting and hardening, it is subject to potential interactions between elements in the waste and binder that can retard or prevent solidification. A new and innovative process utilizing modified sulfur cement developed by the US Bureau of Mines has been applied at Brookhaven National Laboratory (BNL) for the encapsulation of many of these problem wastes. Modified sulfur cement is a thermoplastic material, and as such, it can be heated above its melting point, combined with dry waste products to form a homogeneous mixture, and cooled to form a monolithic solid product. Under sponsorship of the DOE, research and development efforts at BNL have successfully applied the modified sulfur cement process for treatment of a range of LLWs including sodium sulfate salts, boric acid salts, and incinerator bottom ash and for mixed waste contaminated incinerator fly ash. Process development studies were conducted to determine optimal waste loadings for each waste type. Property evaluation studies were conducted to test waste form behavior under disposal conditions by applying relevant performance testing criteria established by the Nuclear Regulatory Commission (for LLW) and the Environmental Protection Agency (for hazardous wastes). Based on both processing and performance considerations, significantly greater waste loadings were achieved using modified sulfur cement when compared with hydraulic cement. Technology demonstration of the modified sulfur cement encapsulation system using production-scale equipment is scheduled for FY 1991

Influence of bone density on the cement fixation of femoral hip resurfacing components.

Science.gov (United States)

Bitsch, Rudi G; Jäger, Sebastian; Lürssen, Marcus; Loidolt, Travis; Schmalzried, Thomas P; Clarius, Michael

2010-08-01

In clinical outcome studies, small component sizes, female gender, femoral shape, focal bone defects, bad bone quality, and biomechanics have been associated with failures of resurfacing arthroplasties. We used a well-established experimental setup and human bone specimens to analyze the effects of bone density on cement fixation of femoral hip resurfacing components. Thirty-one fresh frozen femora were prepared for resurfacing using the original instruments. ASR resurfacing prostheses were implanted after dual-energy X-ray densitometer scans. Real-time measurements of pressure and temperature during implantation, analyses of cement penetration, and measurements of micro motions under torque application were performed. The associations of bone density and measurement data were examined calculating regression lines and multiple correlation coefficients; acceptability was tested with ANOVA. We found significant relations between bone density and micro motion, cement penetration, cement mantle thickness, cement pressure, and interface temperature. Mean bone density of the femora was 0.82 +/- 0.13 g/cm(2), t-score was -0.7 +/- 1.0, and mean micro motion between bone and femoral resurfacing component was 17.5 +/- 9.1 microm/Nm. The regression line between bone density and micro motion was equal to -56.7 x bone density + 63.8, R = 0.815 (p density scans are most helpful for patient selection in hip resurfacing, and a better bone quality leads to higher initial component stability. A sophisticated cementing technique is recommended to avoid vigorous impaction and incomplete seating, since increasing bone density also results in higher cement pressures, lower cement penetration, lower interface temperatures, and thicker cement mantles. Copyright 2010 Orthopaedic Research Society. Published by Wiley Periodicals, Inc.

Fracture strengths of chair-side-generated veneers cemented with glass fibers.

Science.gov (United States)

Turkaslan, S; Bagis, B; Akan, E; Mutluay, M M; Vallittu, P K

2015-01-01

CAD/CAM (computer-aided design and computer-aided manufacturing) systems have refreshed the idea of chair-side production of restorations, but the fracture of ceramic veneers remains a problem. Cementation with glass fibers may improve the fracture strengths and affect the failure modes of CAD/CAM-generated ceramic veneers. Therefore, this study compared the fracture strengths of ceramic veneers produced at chair side and cemented with or without glass fibers with those of composite veneers. Thirty intact mandibular incisors were randomly divided into three groups ( n = 10) and treated with CAD/CAM-fabricated veneers cemented with dual-cure composite resin luting cement (CRLC; Group 1), CAD/CAM-fabricated veneers cemented with a glass fiber network (GFN) and dual-cure CRLC (Group 2), and a direct particulate filler composite veneer constructed utilizing fiber and a restorative composite resin (Group 3). The specimens were tested with a universal testing machine after thermal cycling treatment. The loads at the start of fracture were the lowest for traditionally fabricated composite veneers and higher for CAD/CAM-generated. Veneers cemented either without or with the GFN. The failure initiation loads (N) for the veneers were 798.92 for Group 1, 836.27 for Group 2, and 585.93 for Group 3. The predominant failure mode is adhesive failure between the laminates and teeth for Group 1, cohesive failure in the luting layer for Group 2, and cohesive laminate failure for Group 3, which showed chipping and small fractures. Ceramic material is a reliable alternative for veneer construction at chair side. Fibers at the cementation interface may improve the clinical longevity and provide higher fracture strength values.

The Comparison of Sorption and Solubility Behavior of Four Different Resin Luting Cements in Different Storage Media.

Science.gov (United States)

Giti, Rashin; Vojdani, Mahroo; Abduo, Jaafar; Bagheri, Rafat

2016-06-01

Structural integrity and dimensional stability are the key factors that determine the clinical success and durability of luting cements in the oral cavity. Sorption and solubility of self-adhesive resin luting cements in food-simulating solutions has not been studied sufficiently. This study aimed to compare the sorption and solubility of 2 conventional and 2 self-adhesive resin-based luting cements immersed in four different storage media. A total of 32 disc-shaped specimens were prepared from each of four resin luting cements; seT (SDI), Panavia F (Kuraray), Clearfil SA Cement (Kuraray), and Choice 2 (Bisco). Eight specimens of each material were immersed in all tested solutions including n-heptane 97%, distilled water, apple juice, or Listerine mouth wash. Sorption and solubility were measured by weighing the specimens before and after immersion and desiccation. Data were analyzed by SPSS version 18, using two-way ANOVA and Tukey's HSD test with p≤ 0.05 set as the level of significance. There was a statistically significant interaction between the materials and solutions. The effect of media on the sorption and solubility was material-dependent. While seT showed the highest values of the sorption in almost all solutions, Choice 2 showed the least values of sorption and solubility. Immersion in apple juice caused more sorption than other solutions (p≤ 0.05). The sorption and solubility behavior of the studied cements were significantly affected by their composition and the storage media. The more hydrophobic materials with higher filler content like Choice 2 resin cement showed the least sorption and solubility. Due to their lower sorption and solubility, these types of resin-based luting cements are recommended to be used clinically.

Coupling failure between stem and femoral component in a constrained revision total knee arthroplasty.

LENUS (Irish Health Repository)

Butt, Ahsan Javed

2013-02-01

Knee revision using constrained implants is associated with greater stresses on the implant and interface surfaces. The present report describes a case of failure of the screw coupling between the stem and the femoral component. The cause of the failure is surmised with outline of the treatment in this case with extensive femoral bone loss. Revision implant stability was augmented with the use of a cemented femoral stem, screw fixation and the metaphyseal sleeve of an S-ROM modular hip system (DePuy international Ltd).

A comparative evaluation of compressive strength of Portland cement with zinc oxide eugenol and Polymer-reinforced cement: an in vitro analysis.

Science.gov (United States)

Prakasam, S; Bharadwaj, Prakasam; Loganathan, S C; Prasanth, B Krishna

2014-01-01

The purpose of this study is to evaluate the ultimate compressive strength of 50% and 25% Portland cement mixed with Polymer-reinforced zinc oxide eugenol and zinc oxide eugenol cement after 1 hour, 24 hours, and 7 days. One hundred and eighty samples were selected. The samples were made cylindrical of size 6 × 8 mm and were divided into six groups as follows with each group consisting of 10 samples. Group 1: Polymer-reinforced zinc oxide eugenol with 50% Portland cement (PMZNPC 50%) Group 2: Polymer-reinforced zinc oxide eugenol with 25% Portland cement (PMZNPC 25%) Group 3: Polymer-reinforced zinc oxide eugenol with 0% Portland cement (PMZNPC 0%) Group 4: Zinc oxide eugenol with 50% Portland cement (ZNPC 50%) Group 5: Zinc oxide eugenol with 25% Portland cement (ZNPC 25%) Group 6: Zinc oxide eugenol with 0% Portland cement (ZNPC 0%) These samples were further subdivided based on time interval and were tested at 1 hour, 24 hours and at 7 th day. After each period of time all the specimens were tested by vertical CVR loaded frame with capacity of 5 tones/0473-10kan National Physical laboratory, New Delhi and the results were statistically analyzed using ANOVA and Scheffe test. Polymer-reinforced cement with 50% Portland cement, Zinc oxide with 50% Portland cement, Polymer-reinforced cement with 25% Portland cement and Zinc oxide with 25% Portland cement exhibited higher compressive strength when compared to Zinc oxide with 0% Portland cement and Polymer-reinforced cement with 0% Portland cement, at different periods of time. The difference between these two groups were statistically significant (P Portland cement in Zinc oxide eugenol and Polymer-modified zinc oxide cement can be used as core build up material and permanent filling material. It is concluded that 50% and 25% Portland cement in zinc oxide eugenol and polymer-modified zinc oxide eugenol results in higher compressive strength and hence can be used as permanent filling material and core built

Stem cell-based treatments against stroke: observations from human proof-of-concept studies and considerations regarding clinical applicability

Directory of Open Access Journals (Sweden)

Thorsten Roland Doeppner

2014-10-01

Full Text Available Ischemic stroke remains a heavy burden for industrialized countries. The only causal therapy is the recanalization of occluded vessels via thrombolysis, which due to a narrow time window still can be offered only to a minority of patients. Since the majority of patients continues to exhibit neurological deficits even following successful thrombolysis, restorative therapies are urgently needed that promote brain remodeling and repair once stroke injury has occurred. Due to their unique properties of action, stem cell-based strategies gained increasing interest during recent years. Using various stroke models in both rodents and primates, the transplantation of stem cells, namely of bone marrow derived mesenchymal stem cells (MSCs or neural progenitor cells (NPCs, has been shown to promote neurological recovery most likely via indirect bystander actions. In view of promising observations, clinical proof-of-concept studies are currently under way, in which effects of stem and precursor cells are evaluated in human stroke patients. In this review we summarize already published studies, which due to the broad experience in other medical contexts mostly employed bone marrow-derived MSCs by means of intravenous transplantation. With the overall number of clinical trials limited in number, only a fraction of these studies used non-treated control groups, and only single studies were adequately blinded. Despite these limitations, first promising results justify the need for more elaborate clinical trials in order to make stem cell transplantation a success for stroke treatment in the future.

Portland cement hydration and early setting of cement stone intended for efficient paving materials

Science.gov (United States)

Grishina, A.

2017-10-01

Due to the growth of load on automotive roads, modern transportation engineering is in need of efficient paving materials. Runways and most advanced highways require Portland cement concretes. This makes important the studies directed to improvement of binders for such concretes. In the present work some peculiarities of the process of Portland cement hydration and early setting of cement stone with barium hydrosilicate sol were examined. It was found that the admixture of said sol leads to a shift in the induction period to later times without significant change in its duration. The admixture of a modifier with nanoscale barium hydrosilicates increases the degree of hydration of the cement clinker minerals and changes the phase composition of the hydration products; in particular, the content of portlandite and tricalcium silicate decreases, while the amount of ettringite increases. Changes in the hydration processes of Portland cement and early setting of cement stone that are caused by the nanoscale barium hydrosilicates, allow to forecast positive technological effects both at the stage of manufacturing and at the stage of operation. In particular, the formwork age can be reduced, turnover of molds can be increased, formation of secondary ettringite and corrosion of the first type can be eliminated.

Facial skeletal augmentation using hydroxyapatite cement.

Science.gov (United States)

Shindo, M L; Costantino, P D; Friedman, C D; Chow, L C

1993-02-01

This study investigates the use of a new calcium phosphate cement, which sets to solid, microporous hydroxyapatite, for facial bone augmentation. In six dogs, the supraorbital ridges were augmented bilaterally with this hydroxyapatite cement. On one side, the hydroxyapatite cement was placed directly onto the bone within a subperiosteal pocket. On the opposite side, the cement was contained within a collagen membrane tubule and then inserted into a subperiosteal pocket. The use of collagen tubules facilitated easy, precise placement of the cement. All implants maintained their original augmented height throughout the duration of the study. They were well tolerated without extrusion or migration, and there was no significant sustained inflammatory response. Histologic studies, performed at 3, 6, and 9 months revealed that when the cement was placed directly onto bone, progressive replacement of the implant by bone (osseointegration of the hydroxyapatite with the underlying bone) without a loss of volume was observed. In contrast, when the cement-collagen tubule combination was inserted, primarily a fibrous union was noted. Despite such fibrous union, the hydroxyapatite-collagen implant solidly bonded to the underlying bone, and no implant resorption was observed. Hydroxyapatite cement can be used successfully for the experimental augmentation of the craniofacial skeleton and may be applicable for such uses in humans.

Cement/slag chemistry studies

International Nuclear Information System (INIS)

Glasser, F.P.; Macphee, D.; Atkins, M.; Beckley, N.; Carson, S.O.; Wilding, C.R.; McHugh, G.

1988-01-01

The performance of cement-based matrices intended for radwaste immobilization is assessed. The long-term performance of the matrix is characterized by thermodynamic evaluation of experimental data. The results are presented in a general form, amenable to a range of specific formulations. The interaction of specific radwaste components with cements has been studied, using Iodine as an example. It occurs as both I - and IO 3 - species, but these differ sharply in sorption characteristics. The effect of ionizing radiation of the pH and E h of cement matrices is reported. (author)

The cement solidification systems at LANL

International Nuclear Information System (INIS)

Veazey, G.W.

1990-01-01

There are two major cement solidification systems at Los Alamos National Laboratory. Both are focused primarily around treating waste from the evaporator at TA-55, the Plutonium Processing Facility. The evaporator receives the liquid waste stream from TA-55's nitric acid-based, aqueous-processing operations and concentrates the majority of the radionuclides in the evaporator bottoms solution. This is sent to the TA-55 cementation system. The evaporator distillate is sent to the TA-50 facility, where the radionuclides are precipitated and then cemented. Both systems treat TRU-level waste, and so are operated according to the criteria for WIPP-destined waste, but they differ in both cement type and mixing method. The TA-55 systems uses Envirostone, a gypsum-based cement and in-drum prop mixing; the TA-50 systems uses Portland cement and drum tumbling for mixing

Chemistry of cements for nuclear applications

International Nuclear Information System (INIS)

Barrett, P.; Glasser, F.P.

1992-01-01

In recent times the nuclear industry has thrown up challenges which cannot be met by the application of conventional civil and materials engineering knowledge. The contributions in this volume investigate all aspects of cement performance. The scope of the papers demonstrates the current balance of activities which have as their objective the elucidation of kinetics and immobilization, determining material interactions and of assessing future performance. The papers reflect the varied goals of the sponsors who include national governments, the Commission of the European Communities and the nuclear industries. In six parts attention is paid to the durability of cement and concrete in repository environment; interactions between cement, waste components and ground water; properties and performance of cement materials; leach behavior and mechanisms, diffusional properties of cement and concrete, including porosity-permeability relationships; and thermodynamics of cementitious systems and modelling of cement performance

Characterization of cement-stabilized Cd wastes

International Nuclear Information System (INIS)

Maria Diez, J.; Madrid, J.; Macias, A.

1996-01-01

Portland cement affords both physical and chemical immobilization of cadmium. The immobilization has been studied analyzing the pore fluid of cement samples and characterizing the solid pastes by X-ray diffraction. The influence of cadmium on the cement hydration and on its mechanical properties has been also studied by isothermal conduction calorimetry and by the measure of strength and setting development. Finally, the effect of cement carbonation on the immobilization of cadmium has been analyzed

Pre-cementation of deep shaft

Science.gov (United States)

Heinz, W. F.

1988-12-01

Pre-cementation or pre-grouting of deep shafts in South Africa is an established technique to improve safety and reduce water ingress during shaft sinking. The recent completion of several pre-cementation projects for shafts deeper than 1000m has once again highlighted the effectiveness of pre-grouting of shafts utilizing deep slimline boreholes and incorporating wireline technique for drilling and conventional deep borehole grouting techniques for pre-cementation. Pre-cementation of deep shaft will: (i) Increase the safety of shaft sinking operation (ii) Minimize water and gas inflow during shaft sinking (iii) Minimize the time lost due to additional grouting operations during sinking of the shaft and hence minimize costly delays and standing time of shaft sinking crews and equipment. (iv) Provide detailed information of the geology of the proposed shaft site. Informations on anomalies, dykes, faults as well as reef (gold bearing conglomerates) intersections can be obtained from the evaluation of cores of the pre-cementation boreholes. (v) Provide improved rock strength for excavations in the immediate vicinity of the shaft area. The paper describes pre-cementation techniques recently applied successfully from surface and some conclusions drawn for further considerations.

Creep behavior of bone cement: a method for time extrapolation using time-temperature equivalence.

Science.gov (United States)

Morgan, R L; Farrar, D F; Rose, J; Forster, H; Morgan, I

2003-04-01

The clinical lifetime of poly(methyl methacrylate) (PMMA) bone cement is considerably longer than the time over which it is convenient to perform creep testing. Consequently, it is desirable to be able to predict the long term creep behavior of bone cement from the results of short term testing. A simple method is described for prediction of long term creep using the principle of time-temperature equivalence in polymers. The use of the method is illustrated using a commercial acrylic bone cement. A creep strain of approximately 0.6% is predicted after 400 days under a constant flexural stress of 2 MPa. The temperature range and stress levels over which it is appropriate to perform testing are described. Finally, the effects of physical aging on the accuracy of the method are discussed and creep data from aged cement are reported.

Preparation of hydraulic cement

Energy Technology Data Exchange (ETDEWEB)

1921-08-28

A process for the preparation of hydraulic cement by the use of oil-shale residues is characterized in that the oil-shale refuse is mixed with granular basic blast-furnace slag and a small amount of portland cement and ground together.

The Challenges of First-in-Human Stem Cell Clinical Trials: What Does This Mean for Ethics and Institutional Review Boards?

Science.gov (United States)

Barker, Roger A; Carpenter, Melissa K; Forbes, Stuart; Goldman, Steven A; Jamieson, Catriona; Murry, Charles E; Takahashi, Jun; Weir, Gordon

2018-05-08

Stem cell-based clinical interventions are increasingly advancing through preclinical testing and approaching clinical trials. The complexity and diversity of these approaches, and the confusion created by unproven and untested stem cell-based "therapies," create a growing need for a more comprehensive review of these early-stage human trials to ensure they place the patients at minimal risk of adverse events but are also based on solid evidence of preclinical efficacy with a clear scientific rationale for that effect. To address this issue and supplement the independent review process, especially that of the ethics and institutional review boards who may not be experts in stem cell biology, the International Society for Stem Cell Research (ISSCR) has developed a set of practical questions to cover the major issues for which clear evidence-based answers need to be obtained before approving a stem cell-based trial. Copyright © 2018 The Authors. Published by Elsevier Inc. All rights reserved.

The effect of fly ash and coconut fibre ash as cement replacement materials on cement paste strength

Science.gov (United States)

Bayuaji, R.; Kurniawan, R. W.; Yasin, A. K.; Fatoni, H. AT; Lutfi, F. M. A.

2016-04-01

Concrete is the backbone material in the construction field. The main concept of the concrete material is composed of a binder and filler. Cement, concrete main binder highlighted by environmentalists as one of the industry are not environmentally friendly because of the burning of cement raw materials in the kiln requires energy up to a temperature of 1450° C and the output air waste CO2. On the other hand, the compound content of cement that can be utilized in innovation is Calcium Hydroxide (CaOH), this compound will react with pozzolan material and produces additional strength and durability of concrete, Calcium Silicate Hydrates (CSH). The objective of this research is to explore coconut fibers ash and fly ash. This material was used as cement replacement materials on cement paste. Experimental method was used in this study. SNI-03-1974-1990 is standard used to clarify the compressive strength of cement paste at the age of 7 days. The result of this study that the optimum composition of coconut fiber ash and fly ash to substitute 30% of cement with 25% and 5% for coconut fibers ash and fly ash with similar strength if to be compared normal cement paste.

Leaching of tritium from a cement composite

International Nuclear Information System (INIS)

Matsuzuru, Hideo; Ito, Akihiko

1978-10-01

Leaching of tritium from cement composites into an aqueous phase has been studied to evaluate the safety of incorporation of the tritiated liquid waste into cement. Leaching tests were performed by the method recommended by the International Atomic Energy Agency. The Leaching fraction was measured as functions of waste-cement ratio (Wa/C), temperature of leachant and curing time. The tritium leachability of cement in the long term test follows the order: alumina cement portland cement slag cement. The fraction of tritium leached increases with increasing Wa/C and temperature and decreasing curing period. A deionized water as a leachant gives a slightly higher leachability than synthetic sea water. The amount leached of tritium from a 200 l drum size specimen was estimated on the basis of the above results. (author)

An Experimental Study of Portland Cement and Superfine Cement Slurry Grouting in Loose Sand and Sandy Soil

OpenAIRE

Weijing Yao; Jianyong Pang; Yushan Liu

2018-01-01

Grouting technology is widely applied in the fields of geotechnical engineering in infrastructure. Loose sand and sandy soil are common poor soils in tunnel and foundation treatments. It is necessary to use superfine cement slurry grouting in the micro-cracks of soil. The different effectiveness of Portland cement slurry and superfine cement slurry in sandy soil by the laboratory grouting experiment method were presented in this paper. The grouting situations of superfine cement slurry inject...

Laboratory Electrical Resistivity Studies on Cement Stabilized Soil

Science.gov (United States)

Lokesh, K. N.; Jacob, Jinu Mary

2017-01-01

Electrical resistivity measurement of freshly prepared uncured and cured soil-cement materials is done and the correlations between the factors controlling the performance of soil-cement and electrical resistivity are discussed in this paper. Conventional quality control of soil-cement quite often involves wastage of a lot of material, if it does not meet the strength criteria. In this study, it is observed that, in soil-cement, resistivity follows a similar trend as unconfined compressive strength, with increase in cement content and time of curing. Quantitative relations developed for predicting 7-day strength of soil-cement mix, using resistivity of the soil-cement samples at freshly prepared state, after 1-hour curing help to decide whether the soil-cement mix meets the desired strength and performance criteria. This offers the option of the soil-cement mix to be upgraded (possibly with additional cement) in its fresh state itself, if it does not fulfil the performance criteria, rather than wasting the material after hardening. PMID:28540364

Dose response effect of cement dust on respiratory muscles competence in cement mill workers.

Science.gov (United States)

Meo, Sultan A; Azeem, Muhammad A; Qureshi, Aijaz A; Ghori, G Moinudin; Al-Drees, Abdul Majeed; Feisal Subhan, Mirza Muhammad

2006-12-01

Electromyography (EMG) of respiratory muscles is a reliable method of assessing the ventilatory muscle function, but still its use has not been fully utilized to determine the occupational and environmental hazards on respiratory muscles. Therefore, EMG of intercostal muscles was performed to determine the dose response effect of cement dust on respiratory muscles competence. Matched cross-sectional study of EMG in 50 non-smoking cement mill workers with an age range of 20 - 60 years, who worked without the benefit of cement dust control ventilation or respiratory protective devices. EMG was performed by using surface electrodes and chart recorder. Significant reduction was observed in number of peaks (p competence and stratification of results shows a dose-effect of years of exposure in cement mill.

Corrosion-resistant Foamed Cements for Carbon Steels

Energy Technology Data Exchange (ETDEWEB)

Sugama T.; Gill, S.; Pyatina, T., Muraca, A.; Keese, R.; Khan, A.; Bour, D.

2012-12-01

The cementitious material consisting of Secar #80, Class F fly ash, and sodium silicate designed as an alternative thermal-shock resistant cement for the Enhanced Geothermal System (EGS) wells was treated with cocamidopropyl dimethylamine oxide-based compound as foaming agent (FA) to prepare numerous air bubble-dispersed low density cement slurries of and #61603;1.3 g/cm3. Then, the foamed slurry was modified with acrylic emulsion (AE) as corrosion inhibitor. We detailed the positive effects of the acrylic polymer (AP) in this emulsion on the five different properties of the foamed cement: 1) The hydrothermal stability of the AP in 200 and #61616;C-autoclaved cements; 2) the hydrolysis-hydration reactions of the slurry at 85 and #61616;C; 3) the composition of crystalline phases assembled and the microstructure developed in autoclaved cements; 4) the mechanical behaviors of the autoclaved cements; and, 5) the corrosion mitigation of carbon steel (CS) by the polymer. For the first property, the hydrothermal-catalyzed acid-base interactions between the AP and cement resulted in Ca-or Na-complexed carboxylate derivatives, which led to the improvement of thermal stability of the AP. This interaction also stimulated the cement hydration reactions, enhancing the total heat evolved during cement’s curing. Addition of AP did not alter any of the crystalline phase compositions responsible for the strength of the cement. Furthermore, the AP-modified cement developed the porous microstructure with numerous defect-free cavities of disconnected voids. These effects together contributed to the improvement of compressive-strength and –toughness of the cured cement. AP modification of the cement also offered an improved protection of CS against brine-caused corrosion. There were three major factors governing the corrosion protection: 1) Reducing the extents of infiltration and transportation of corrosive electrolytes through the cement layer deposited on the underlying CS

Heat transfer properties and thermal cure of glass-ionomer dental cements.

Science.gov (United States)

Gavic, Lidia; Gorseta, Kristina; Glavina, Domagoj; Czarnecka, Beata; Nicholson, John W

2015-10-01

Under clinical conditions, conventional glass-ionomer dental cements can be cured by application of heat from dental cure lamps, which causes acceleration in the setting. In order for this to be successful, such heat must be able to spread sufficiently through the cement to enhance cure, but not transmit heat so effectively that the underlying dental pulp of the tooth is damaged. The current study was aimed at measuring heat transfer properties of modern restorative glass-ionomers to determine the extent to which they meet these twin requirements. Three commercial glass ionomer cements (Ionofil Molar, Ketac Molar and Equia™ Fill) were used in association with three different light emitting diode cure lamps designed for clinical use. In addition, for each cement, one set of specimens was allowed to cure without application of a lamp. Temperature changes were measured at three different depths (2, 3 and 4 mm) after cure times of 20, 40 and 60 s. The difference among the tested groups was evaluated by ANOVA (P heat irradiation, but much greater temperature increases when exposed to the cure lamp. However, temperature rises did not exceed 12.9 °C. Application of the cure lamp led to the establishment of a temperature gradient throughout each specimen. Differences were typically significant (P heating effect. Because the thermal conductivity of glass-ionomers is low, temperature rises at 4 mm depths were much lower than at 2 mm. At no time did the temperature rise sufficiently to cause concern about potential damage to the pulp.

INFLUENCE OF WINE ACID ON RHEOLOGICAL PROPERTIES OF WELL BORE CEMENT SLURRIES AND HARDENED CEMENT PROPERTIES

Directory of Open Access Journals (Sweden)

Nediljka Gaurina-Međimurec

1989-12-01

Full Text Available Adaptation of commercial types of domestic cements for use in cementing the deep wells is a process by which Yugoslav oil industry tends to solve problems of completion of those wells independently. In order to design a domestic, cheep and effective retarder, tests of applicability of wine acid on cement slurries have been carried out. Besides examining the necessary wine acid content to achieve desirable Theological properties, the influence of this additive on properties of hardened cement samples has been tested too (the paper is published in Croatian.

Controlled, prospective, randomized, clinical split-mouth evaluation of partial ceramic crowns luted with a new, universal adhesive system/resin cement: results after 18 months.

Science.gov (United States)

Vogl, Vanessa; Hiller, Karl-Anton; Buchalla, Wolfgang; Federlin, Marianne; Schmalz, Gottfried

2016-12-01

A new universal adhesive with corresponding luting composite was recently marketed which can be used both, in a self-etch or in an etch-and-rinse mode. In this study, the clinical performance of partial ceramic crowns (PCCs) inserted with this adhesive and the corresponding luting material used in a self-etch or selective etch approach was compared with a self-adhesive universal luting material. Three PCCs were placed in a split-mouth design in 50 patients. Two PCCs were luted with a combination of a universal adhesive/resin cement (Scotchbond Universal/RelyX Ultimate, 3M ESPE) with (SB+E)/without (SB-E) selective enamel etching. Another PCC was luted with a self-adhesive resin cement (RelyX Unicem 2, 3M ESPE). Forty-eight patients were evaluated clinically according to FDI criteria at baseline and 6, 12 and 18 months. For statistical analyses, the chi-square test (α = 0.05) and Kaplan-Meier analysis were applied. Clinically, no statistically significant differences between groups were detected over time. Within groups, clinically significant increase for criterion "marginal staining" was detected for SB-E over 18 months. Kaplan-Meier analysis revealed significantly higher retention rates for SB+E (97.8 %) and SB-E (95.6 %) in comparison to RXU2 (75.6 %). The 18-month clinical performance of a new universal adhesive/composite combination showed no differences with respect to bonding strategy and may be recommended for luting PCCs. Longer-term evaluation is needed to confirm superiority of SB+E over SB-E. At 18 months, the new multi-mode adhesive, Scotchbond Universal, showed clinically reliable results when used for luting PCCs.

Physical properties and comparative strength of a bioactive luting cement.

Science.gov (United States)

Jefferies, Steven; Lööf, Jesper; Pameijer, Cornelis H; Boston, Daniel; Galbraith, Colin; Hermansson, Leif

2013-01-01

cement at Vickers hardness of 51.4 plus or equal to 10. There was no evidence of cracks due to radial expansion in PJCs by the Ceramir C and B cement. All luting cements tested demonstrated compressive strengths well in excess of the ISO requirement for water-based cements of no less than 50 MPa. Ceramir C and B showed significantly higher CS than RelyX Luting Cement after 24 hours, but was not significantly higher than either Fuji Plus or RelyX Unicem. The ST and FT values of CC and B conform to and are within the boundaries of the requirements of the standard. Surface hardness was statistically higher than and comparable to zinc phosphate cement. There was no evidence of potentially clinically significant and deleterious expansion behavior by this cement. All cements tested demonstrated acceptable strength properties. Within the limits of this study, Ceramir C and B is deemed to possess physical properties suitable for a dental luting cement.

Calcium Aluminate Cement Hydration Model

Directory of Open Access Journals (Sweden)

Matusinović, T.

2011-01-01

Full Text Available Calcium aluminate cement (AC is a very versatile special cement used for specific applications. As the hydration of AC is highly temperature dependent, yielding structurally different hydration products that continuously alter material properties, a good knowledge of thermal properties at early stages of hydration is essential. The kinetics of AC hydration is a complex process and the use of single mechanisms models cannot describe the rate of hydration during the whole stage.This paper examines the influence of temperature (ϑ=5–20 °C and water-to-cement mass ratio (mH /mAC = 0.4; 0.5 and 1.0 on hydration of commercial iron-rich AC ISTRA 40 (producer: Istra Cement, Pula, Croatia, which is a part of CALUCEM group, Figs 1–3. The flow rate of heat generation of cement pastes as a result of the hydration reactions was measured with differential microcalorimeter. Chemically bonded water in the hydrated cement samples was determined by thermo-gravimetry.Far less heat is liberated when cement and water come in contact for the first time, Fig. 1, than in the case for portland cement (PC. Higher water-to-cement ratio increases the heat evolved at later ages (Fig. 3 due to higher quantity of water available for hydration. A significant effect of the water-to-cement ratio on the hydration rate and hydration degree showed the importance of water as being the limiting reactant that slows down the reaction early. A simplified stoichiometric model of early age AC hydration (eq. (8 based on reaction schemes of principal minerals, nominally CA, C12A7 and C4AF (Table 1, was employed. Hydration kinetics after the induction period (ϑ < 20 °C had been successfully described (Fig. 4 and Table 2 by a proposed model (eq. (23 which simultaneously comprised three main mechanisms: nucleation and growth, interaction at phase boundary, and mass transfer. In the proposed kinetic model the nucleation and growth is proportional to the amount of reacted minerals (eq

Percutaneous bone cement refixation of aseptically loose hip prostheses: the effect of interface tissue removal on injected cement volumes

Energy Technology Data Exchange (ETDEWEB)

Malan, Daniel F. [Leiden University Medical Center, Department of Orthopaedics, Leiden (Netherlands); Delft University of Technology, Department of Intelligent Systems, Delft (Netherlands); Valstar, Edward R. [Leiden University Medical Center, Department of Orthopaedics, Leiden (Netherlands); Delft University of Technology, Department of Biomechanical Engineering, Delft (Netherlands); Nelissen, Rob G.H.H. [Leiden University Medical Center, Department of Orthopaedics, Leiden (Netherlands)

2014-11-15

To quantify whether injected cement volumes differed between two groups of patients who underwent experimental minimally invasive percutaneous cement injection procedures to stabilize aseptically loose hip prostheses. One patient group was preoperatively treated using gene-directed enzyme prodrug therapy to remove fibrous interface tissue, while the other group received no preoperative treatment. It was hypothesized that cement penetration may have been inhibited by the presence of fibrous interface tissue in periprosthetic lesions. We analyzed 17 patients (14 female, 3 male, ages 72-91, ASA categories 2-4) who were treated at our institution. Osteolytic lesions and injected cement were manually delineated using 3D CT image segmentation, and the deposition of injected cement was quantified. Patients who underwent preoperative gene-directed enzyme therapy to remove fibrous tissue exhibited larger injected cement volumes than those who did not. The observed median increase in injected cement volume was 6.8 ml. Higher cement leakage volumes were also observed for this group. We conclude that prior removal of periprosthetic fibrous interface tissue may enable better cement flow and penetration. This might lead to better refixation of aseptically loosened prostheses. (orig.)

CO2 Capture by Cement Raw Meal

DEFF Research Database (Denmark)

Pathi, Sharat Kumar; Lin, Weigang; Illerup, Jytte Boll

2013-01-01

The cement industry is one of the major sources of CO2 emissions and is likely to contribute to further increases in the near future. The carbonate looping process has the potential to capture CO2 emissions from the cement industry, in which raw meal for cement production could be used...... as the sorbent. Cyclic experiments were carried out in a TGA apparatus using industrial cement raw meal and synthetic raw meal as sorbents, with limestone as the reference. The results show that the CO2 capture capacities of the cement raw meal and the synthetic raw meal are comparable to those of pure limestone...... that raw meal could be used as a sorbent for the easy integration of the carbonate looping process into the cement pyro process for reducing CO2 emissions from the cement production process....

[Cement augmentation on the spine : Biomechanical considerations].

Science.gov (United States)

Kolb, J P; Weiser, L; Kueny, R A; Huber, G; Rueger, J M; Lehmann, W

2015-09-01

Vertebral compression fractures are the most common osteoporotic fractures. Since the introduction of vertebroplasty and screw augmentation, the management of osteoporotic fractures has changed significantly. The biomechanical characteristics of the risk of adjacent fractures and novel treatment modalities for osteoporotic vertebral fractures, including pure cement augmentation by vertebroplasty, and cement augmentation of screws for posterior instrumentation, are explored. Eighteen human osteoporotic lumbar spines (L1-5) adjacent to vertebral bodies after vertebroplasty were tested in a servo-hydraulic machine. As augmentation compounds we used standard cement and a modified low-strength cement. Different anchoring pedicle screws were tested with and without cement augmentation in another cohort of human specimens with a simple pull-out test and a fatigue test that better reflects physiological conditions. Cement augmentation in the osteoporotic spine leads to greater biomechanical stability. However, change in vertebral stiffness resulted in alterations with the risk of adjacent fractures. By using a less firm cement compound, the risk of adjacent fractures is significantly reduced. Both screw augmentation techniques resulted in a significant increase in the withdrawal force compared with the group without cement. Augmentation using perforated screws showed the highest stability in the fatigue test. The augmentation of cement leads to a significant change in the biomechanical properties. Differences in the stability of adjacent vertebral bodies increase the risk of adjacent fractures, which could be mitigated by a modified cement compound with reduced strength. Screws that were specifically designed for cement application displayed greatest stability in the fatigue test.

Tympanoplasty with ionomeric cement

DEFF Research Database (Denmark)

Kjeldsen, A D; Grøntved, A M

2000-01-01

with isolated erosion of the long incus process have been treated with a new surgical technique in which the ossicular chain was rebuilt with ionomeric cement. The results in hearing performance (mean pure-tone average (PTA) 0.5, 1 and 2 kHz) were evaluated pre- and post-surgery, and compared to those...... of > 10 dB, in 4 there was a slight improvement and in 2 a decline. The difference was not statistically significant. Hearing improvement using ionomeric cement in type II tympanoplasty was satisfactory. Reconstruction of the ossicular chain with ionomeric cement is recommended, as the procedure is easy...

Sulphur cement pre-composition and process for preparing such sulphur cement pre-composition

NARCIS (Netherlands)

2013-01-01

The invention provides a process for the preparation of a sulphur cement pre-composition comprising reacting sulphur modifier with polysulphide-containing organosilane to obtain in the presence of sulphur the sulphur cement pre-composition, wherein the organosilane has the general molecular formula:

Immunoregulation by Mesenchymal Stem Cells: Biological Aspects and Clinical Applications

Science.gov (United States)

Castro-Manrreza, Marta E.; Montesinos, Juan J.

2015-01-01

Mesenchymal stem cells (MSCs) are multipotent cells capable of differentiation into mesenchymal lineages and that can be isolated from various tissues and easily cultivated in vitro. Currently, MSCs are of considerable interest because of the biological characteristics that confer high potential applicability in the clinical treatment of many diseases. Specifically, because of their high immunoregulatory capacity, MSCs are used as tools in cellular therapies for clinical protocols involving immune system alterations. In this review, we discuss the current knowledge about the capacity of MSCs for the immunoregulation of immunocompetent cells and emphasize the effects of MSCs on T cells, principal effectors of the immune response, and the immunosuppressive effects mediated by the secretion of soluble factors and membrane molecules. We also describe the mechanisms of MSC immunoregulatory modulation and the participation of MSCs as immune response regulators in several autoimmune diseases, and we emphasize the clinical application in graft versus host disease (GVHD). PMID:25961059

Photoactive glazed polymer-cement composite

Science.gov (United States)

Baltes, Liana; Patachia, Silvia; Tierean, Mircea; Ekincioglu, Ozgur; Ozkul, Hulusi M.

2018-04-01

Macro defect free cements (MDF), a kind of polymer-cement composites, are characterized by remarkably high mechanical properties. Their flexural strengths are 20-30 times higher than those of conventional cement pastes, nearly equal to that of an ordinary steel. The main drawback of MDF cements is their sensitivity to water. This paper presents a method to both diminish the negative impact of water on MDF cements mechanical properties and to enlarge their application by conferring photoactivity. These tasks were solved by glazing MDF cement with an ecological glaze containing nano-particles of TiO2. Efficiency of photocatalytic activity of this material was tested against methylene blue aqueous solution (4.4 mg/L). Influence of the photocatalyst concentration in the glaze paste and of the contact time on the photocatalysis process (efficiency and kinetic) was studied. The best obtained photocatalysis yield was of 97.35%, after 8 h of exposure to 254 nm UV radiation when used an MDF glazed with 10% TiO2 in the enamel paste. Surface of glazed material was characterized by optic microscopy, scratch test, SEM, XRD, and EDS. All these properties were correlated with the aesthetic aspect of the glazed surface aiming to propose using of this material for sustainable construction development.

Comparative evaluation of marginal leakage of provisional crowns cemented with different temporary luting cements: In vitro study

Directory of Open Access Journals (Sweden)

Sheen Juneja Arora

2016-01-01

Conclusion: The temporary cements with eugenol showed more microleakage than those without eugenol. SC-10 crowns showed more microleakage compared to Protemp 4 crowns. SC-10 crowns cemented with Kalzinol showed maximum microleakage and Protemp 4 crowns cemented with HY bond showed least microleakage.

Aspects of bonding between resin luting cements and glass ceramic materials.

Science.gov (United States)

Tian, Tian; Tsoi, James Kit-Hon; Matinlinna, Jukka P; Burrow, Michael F

2014-07-01

The bonding interface of glass ceramics and resin luting cements plays an important role in the long-term durability of ceramic restorations. The purpose of this systematic review is to discuss the various factors involved with the bond between glass ceramics and resin luting cements. An electronic Pubmed, Medline and Embase search was conducted to obtain laboratory studies on resin-ceramic bonding published in English and Chinese between 1972 and 2012. Eighty-three articles were included in this review. Various factors that have a possible impact on the bond between glass ceramics and resin cements were discussed, including ceramic type, ceramic crystal structure, resin luting cements, light curing, surface treatments, and laboratory test methodology. Resin-ceramic bonding has been improved substantially in the past few years. Hydrofluoric acid (HF) etching followed by silanizaiton has become the most widely accepted surface treatment for glass ceramics. However, further studies need to be undertaken to improve surface preparations without HF because of its toxicity. Laboratory test methods are also required to better simulate the actual oral environment for more clinically compatible testing. Copyright © 2014 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Development of an Improved Cement for Geothermal Wells

Energy Technology Data Exchange (ETDEWEB)

Trabits, George [Trabits Group, LLC, Wasilla, AK (United States)

2015-04-20

After an oil, gas, or geothermal production well has been drilled, the well must be stabilized with a casing (sections of steel pipe that are joined together) in order to prevent the walls of the well from collapsing. The gap between the casing and the walls of the well is filled with cement, which locks the casing into place. The casing and cementing of geothermal wells is complicated by the harsh conditions of high temperature, high pressure, and a chemical environment (brines with high concentrations of carbon dioxide and sulfuric acid) that degrades conventional Portland cement. During the 1990s and early 2000s, the U.S. Department of Energy’s Geothermal Technologies Office (GTO) provided support for the development of fly-ash-modified calcium aluminate phosphate (CaP) cement, which offers improved resistance to degradation compared with conventional cement. However, the use of CaP cements involves some operational constraints that can increase the cost and complexity of well cementing. In some cases, CaP cements are incompatible with chemical additives that are commonly used to adjust cement setting time. Care must also be taken to ensure that CaP cements do not become contaminated with leftover conventional cement in pumping equipment used in conventional well cementing. With assistance from GTO, Trabits Group, LLC has developed a zeolite-containing cement that performs well in harsh geothermal conditions (thermal stability at temperatures of up to 300°C and resistance to carbonation) and is easy to use (can be easily adjusted with additives and eliminates the need to “sterilize” pumping equipment as with CaP cements). This combination of properties reduces the complexity/cost of well cementing, which will help enable the widespread development of geothermal energy in the United States.

Effect of Abutment Modification and Cement Type on Retention of Cement-Retained Implant Supported Crowns

OpenAIRE

Farzin, Mitra; Torabi, Kianoosh; Ahangari, Ahmad Hasan; Derafshi, Reza

2014-01-01

Objective: Provisional cements are commonly used to facilitate retrievability of cement-retained fixed implant restorations; but compromised abutment preparation may affect the retention of implant-retained crowns.The purpose of this study was to investigate the effect of abutment design and type of luting agent on the retentive strength of cement-retained implant restorations. Materials and Method: Two prefabricated abutments were attached to their corresponding analogs and embedded in an ac...

Alternative Fuel for Portland Cement Processing

Energy Technology Data Exchange (ETDEWEB)

Schindler, Anton K; Duke, Steve R; Burch, Thomas E; Davis, Edward W; Zee, Ralph H; Bransby, David I; Hopkins, Carla; Thompson, Rutherford L; Duan, Jingran; ; Venkatasubramanian, Vignesh; Stephen, Giles

2012-06-30

The production of cement involves a combination of numerous raw materials, strictly monitored system processes, and temperatures on the order of 1500 °C. Immense quantities of fuel are required for the production of cement. Traditionally, energy from fossil fuels was solely relied upon for the production of cement. The overarching project objective is to evaluate the use of alternative fuels to lessen the dependence on non-renewable resources to produce portland cement. The key objective of using alternative fuels is to continue to produce high-quality cement while decreasing the use of non-renewable fuels and minimizing the impact on the environment. Burn characteristics and thermodynamic parameters were evaluated with a laboratory burn simulator under conditions that mimic those in the preheater where the fuels are brought into a cement plant. A drop-tube furnace and visualization method were developed that show potential for evaluating time- and space-resolved temperature distributions for fuel solid particles and liquid droplets undergoing combustion in various combustion atmospheres. Downdraft gasification has been explored as a means to extract chemical energy from poultry litter while limiting the throughput of potentially deleterious components with regards to use in firing a cement kiln. Results have shown that the clinkering is temperature independent, at least within the controllable temperature range. Limestone also had only a slight effect on the fusion when used to coat the pellets. However, limestone addition did display some promise in regards to chlorine capture, as ash analyses showed chlorine concentrations of more than four times greater in the limestone infused ash as compared to raw poultry litter. A reliable and convenient sampling procedure was developed to estimate the combustion quality of broiler litter that is the best compromise between convenience and reliability by means of statistical analysis. Multi-day trial burns were conducted

The Influence of Abutment Surface Treatment and the Type of Luting Cement on Shear Bond Strength between Titanium/Cement/Zirconia

Directory of Open Access Journals (Sweden)

Beata Śmielak

2015-01-01

Full Text Available Objectives. The objectives of this study were to evaluate the shear bond strength of zirconia cylinders on a modified titanium surface using different luting cement types. Material and Methods. Eighty titanium disks were divided into two groups (n=40, which were treated with either grinding or a combination of sandblasting and grinding. Then, each group was subdivided into 4 groups (n=10 and the disks were bonded to disks of sintered zirconia using one of four cement types (permanent: composite cement; temporary: polycarboxylate cement, zinc-oxide-eugenol cement, and resin cement. Shear bond strength (SBS was measured in a universal testing machine. Fracture pattern and site characteristic were recorded. A fractographic analysis was performed with SEM. The chemical analysis of the composition of the fractures was performed using energy-dispersive X-ray spectroscopy (EDS. The results of the experiment were analyzed with two-way analysis of variance and Tukey post hoc test. Results. The highest mean values of SBS were achieved when grinding was combined with sandblasting and when composite cement was used (18.18 MPa. In the temporary cement group, the highest mean values of SBS were for polycarboxylate cement after grinding (3.57 MPa. Conclusion. The choice of cement has a crucial influence on the titanium-cement-zirconia interface quality.

Energetically Modified Cement (EMC) - Performance Mechanism

Energy Technology Data Exchange (ETDEWEB)

Ronin, Vladimir; Elfgren, Lennart [Luleaa Univ. of Technology (Sweden). Centre for High Performance Cement

2003-03-01

Energetically Modified Cements, EMC, made of intensively milled cement (50%) and fillers (50%) of quartz or fly ash have been compared to blends of Ordinary Portland Cement, OPC, and fillers. The EMCs have better properties than other blends and are comparable to unblended OPC. This remarkable fact can probably be explained as follows. The grinding process reduces the size of both cement grains and fillers. This combined with the creation of micro defects gives the ground cement a very high degree of hydration. The increased early hydration and a better distribution of hydration products results in an extensive pore size refinement of the hardened binder. This pore size refinement leads to a favorably reduced permeability and diffusivity and very good mechanical properties.

Optimization of mix design by using superplasticized cement

International Nuclear Information System (INIS)

Khaskheli, G.B.; Kumar, A.; Umrani, A.N.

2009-01-01

Superplasticizers are high range water reducers which are capable of producing high-strength concrete with low permeability. Recently a cement factory in Sindh has launched SPC (Superplasticized Cement) which contains the required amount of superplasticizers. It is needed to investigate its performance compared to that of OPC (Ordinal-Y Portland Cement). This study is framed to optimize various strengths of structural concrete through the use of SPC of the cement factory. In total 288 cubes (6x6x6) were cast and tested for four different compressive strength of concrete (8000, 6000, 5000 and 4000 psi) manufactured with two brands of cement (OPC and SPC) of the cement factory and two different coarse aggregate sizes (40 and 20 mm) at three different curing ages (7,14 and 28 days). The effect on compressive strength of structural concrete was also observed by adopting 5 and 10% reduction in cement content of the superplasticized cement. Results have indicated that structural concrete made with superplasticized cement could give higher compressive strength than that of OPC at all the curing ages, and 10% saving in cement content could be achieved by using superplasticized cement. Structural concrete made with superplasticized cement could attain higher strength in a shorter period of time, and workability of structural concrete could be increased by using SPC. (author)

Molecular biology of breast cancer stem cells: potential clinical applications.

Science.gov (United States)

Nguyen, Nam P; Almeida, Fabio S; Chi, Alex; Nguyen, Ly M; Cohen, Deirdre; Karlsson, Ulf; Vinh-Hung, Vincent

2010-10-01

Breast cancer stem cells (CSC) have been postulated recently as responsible for failure of breast cancer treatment. The purpose of this study is to review breast CSCs molecular biology with respect to their mechanism of resistance to conventional therapy, and to develop treatment strategies that may improve survival of breast cancer patients. A literature search has identified in vitro and in vivo studies of breast CSCs. Breast CSCs overexpress breast cancer resistance protein (BCRP) which allows cancer cells to transport actively chemotherapy agents out of the cells. Radioresistance is modulated through activation of Wnt signaling pathway and overexpression of genes coding for glutathione. Lapatinib can selectively target HER-2 positive breast CSCs and improves disease-free survival in these patients. Metformin may target basal type breast CSCs. Parthenolide and oncolytic viruses are promising targeting agents for breast CSCs. Future clinical trials for breast cancer should include anti-cancer stem cells targeting agents in addition to conventional chemotherapy. Hypofractionation radiotherapy may be indicated for residual disease post chemotherapy. 2010 Elsevier Ltd. All rights reserved.

Thermodynamic modelling of alkali-activated slag cements

International Nuclear Information System (INIS)

Myers, Rupert J.; Lothenbach, Barbara; Bernal, Susan A.; Provis, John L.

2015-01-01

Highlights: • A thermodynamic modelling analysis of alkali-activated slag cements is presented. • Thermodynamic database describes zeolites, alkali carbonates, C–(N–)A–S–H gel. • Updated thermodynamic model for Mg–Al layered double hydroxides. • Description of phase assemblages in Na 2 SiO 3 - and Na 2 CO 3 -activated slag cements. • Phase diagrams for NaOH-activated and Na 2 SiO 3 -activated slag cements are simulated. - Abstract: This paper presents a thermodynamic modelling analysis of alkali-activated slag-based cements, which are high performance and potentially low-CO 2 binders relative to Portland cement. The thermodynamic database used here contains a calcium (alkali) aluminosilicate hydrate ideal solid solution model (CNASH-ss), alkali carbonate and zeolite phases, and an ideal solid solution model for a hydrotalcite-like Mg–Al layered double hydroxide phase. Simulated phase diagrams for NaOH- and Na 2 SiO 3 -activated slag-based cements demonstrate the high stability of zeolites and other solid phases in these materials. Thermodynamic modelling provides a good description of the chemical compositions and types of phases formed in Na 2 SiO 3 -activated slag cements over the most relevant bulk chemical composition range for these cements, and the simulated volumetric properties of the cement paste are consistent with previously measured and estimated values. Experimentally determined and simulated solid phase assemblages for Na 2 CO 3 -activated slag cements were also found to be in good agreement. These results can be used to design the chemistry of alkali-activated slag-based cements, to further promote the uptake of this technology and valorisation of metallurgical slags

Stem cells: roadmap to the clinic

OpenAIRE

Daley, George Q.

2010-01-01

Over the last decade, a remarkable number of papers have been published in which the biology of stem cells is introduced with words and phrases such as “promise,” “rapid progress,” and “future therapies.” To separate myth and hype from reality, the articles in this Stem Cells Review series comprise a rich resource on the state of this fast-paced field and provide a balanced perspective on some of the major advances. They recount what the field has achieved over the past decade and where the f...

Signal-inducing bone cements for MRI-guided spinal cementoplasty: evaluation of contrast-agent-based polymethylmethacrylate cements

International Nuclear Information System (INIS)

Bail, Hermann Josef; Tsitsilonis, Serafim; Wichlas, Florian; Sattig, Christoph; Papanikolaou, Ioannis; Teichgraeber, Ulf Karl Mart

2012-01-01

The purpose of this work is to evaluate two signal-inducing bone cements for MRI-guided spinal cementoplasty. The bone cements were made of polymethylmethacrylate (PMMA, 5 ml monomeric, 12 g polymeric) and gadoterate meglumine as a contrast agent (CA, 0-40 μl) with either saline solution (NaCl, 2-4 ml) or hydroxyapatite bone substitute (HA, 2-4 ml). The cement's signal was assessed in an open 1-Tesla MR scanner, with T1W TSE and fast interventional T1W TSE pulse sequences, and the ideal amount of each component was determined. The compressive and bending strength for different amounts of NaCl and HA were evaluated. The cement's MRI signal depended on the concentration of CA, the amount of NaCl or HA, and the pulse sequence. The signal peaks were recorded between 1 and 10 μl CA per ml NaCl or HA, and were higher in fast T1W TSE than in T1W TSE images. The NaCl-PMMA-CA cements had a greater MRI signal intensity and compressive strength; the HA-PMMA-CA cements had a superior bending strength. Concerning the MR signal and biomechanical properties, these cements would permit MRI-guided cementoplasty. Due to its higher signal and greater compressive strength, the NaCl-PMMA-CA compound appears to be superior to the HA-PMMA-CA compound. (orig.)

Characterization of experimental cements with endodontic goal

International Nuclear Information System (INIS)

Dantas, A.M.X.; Sousa, W.J.B.; Oliveira, E.D.C.; Carrodeguas, R.G.; Fook, M.V. Lia; Universidade Estadual da Paraiba

2017-01-01

The present study aimed to characterize experimental endodontic cements using as comparative parameter MTA cement. Two experimental endodontic cements were assessed: one based on 95% tri-strontium aluminate and 5% gypsum (CE1) and another based on 50% Sr_3Al_2O_6 and 50% non-structural white cement (CE2). Experimental cements were manipulated and characterized by scanning electron microscopy (SEM), coupled to EDS mode, X-ray diffractometer (XRD) and Thermogravimetric (TG) analysis. Data analysis demonstrated that the particles of the materials used presented varied shapes and sizes, with similar elements and crystalline behavior. However, CE1 presented increased mass loss. Experimental cements presents similarities to MTA, nevertheless, further studies are encourage to determinate comparative properties with the commercially material. (author)

Clinical efficacy of gene-modified stem cells in adenosine deaminase-deficient immunodeficiency.

Science.gov (United States)

Shaw, Kit L; Garabedian, Elizabeth; Mishra, Suparna; Barman, Provaboti; Davila, Alejandra; Carbonaro, Denise; Shupien, Sally; Silvin, Christopher; Geiger, Sabine; Nowicki, Barbara; Smogorzewska, E Monika; Brown, Berkley; Wang, Xiaoyan; de Oliveira, Satiro; Choi, Yeong; Ikeda, Alan; Terrazas, Dayna; Fu, Pei-Yu; Yu, Allen; Fernandez, Beatriz Campo; Cooper, Aaron R; Engel, Barbara; Podsakoff, Greg; Balamurugan, Arumugam; Anderson, Stacie; Muul, Linda; Jagadeesh, G Jayashree; Kapoor, Neena; Tse, John; Moore, Theodore B; Purdy, Ken; Rishi, Radha; Mohan, Kathey; Skoda-Smith, Suzanne; Buchbinder, David; Abraham, Roshini S; Scharenberg, Andrew; Yang, Otto O; Cornetta, Kenneth; Gjertson, David; Hershfield, Michael; Sokolic, Rob; Candotti, Fabio; Kohn, Donald B

2017-05-01

Autologous hematopoietic stem cell transplantation (HSCT) of gene-modified cells is an alternative to enzyme replacement therapy (ERT) and allogeneic HSCT that has shown clinical benefit for adenosine deaminase-deficient (ADA-deficient) SCID when combined with reduced intensity conditioning (RIC) and ERT cessation. Clinical safety and therapeutic efficacy were evaluated in a phase II study. Ten subjects with confirmed ADA-deficient SCID and no available matched sibling or family donor were enrolled between 2009 and 2012 and received transplantation with autologous hematopoietic CD34+ cells that were modified with the human ADA cDNA (MND-ADA) γ-retroviral vector after conditioning with busulfan (90 mg/m2) and ERT cessation. Subjects were followed from 33 to 84 months at the time of data analysis. Safety of the procedure was assessed by recording the number of adverse events. Efficacy was assessed by measuring engraftment of gene-modified hematopoietic stem/progenitor cells, ADA gene expression, and immune reconstitution. With the exception of the oldest subject (15 years old at enrollment), all subjects remained off ERT with normalized peripheral blood mononuclear cell (PBMC) ADA activity, improved lymphocyte numbers, and normal proliferative responses to mitogens. Three of nine subjects were able to discontinue intravenous immunoglobulin replacement therapy. The MND-ADA vector was persistently detected in PBMCs (vector copy number [VCN] = 0.1-2.6) and granulocytes (VCN = 0.01-0.3) through the most recent visits at the time of this writing. No patient has developed a leukoproliferative disorder or other vector-related clinical complication since transplant. These results demonstrate clinical therapeutic efficacy from gene therapy for ADA-deficient SCID, with an excellent clinical safety profile. ClinicalTrials.gov NCT00794508. Food and Drug Administration Office of Orphan Product Development award, RO1 FD003005; NHLBI awards, PO1 HL73104 and Z01 HG000122; UCLA

Clinical efficacy of gene-modified stem cells in adenosine deaminase–deficient immunodeficiency

Science.gov (United States)

Shaw, Kit L.; Garabedian, Elizabeth; Mishra, Suparna; Barman, Provaboti; Davila, Alejandra; Carbonaro, Denise; Shupien, Sally; Silvin, Christopher; Geiger, Sabine; Nowicki, Barbara; Smogorzewska, E. Monika; Brown, Berkley; Wang, Xiaoyan; de Oliveira, Satiro; Choi, Yeong; Ikeda, Alan; Terrazas, Dayna; Fu, Pei-Yu; Yu, Allen; Fernandez, Beatriz Campo; Cooper, Aaron R.; Engel, Barbara; Podsakoff, Greg; Balamurugan, Arumugam; Anderson, Stacie; Muul, Linda; Jagadeesh, G. Jayashree; Kapoor, Neena; Tse, John; Moore, Theodore B.; Purdy, Ken; Rishi, Radha; Mohan, Kathey; Skoda-Smith, Suzanne; Buchbinder, David; Abraham, Roshini S.; Scharenberg, Andrew; Yang, Otto O.; Cornetta, Kenneth; Gjertson, David; Hershfield, Michael; Sokolic, Rob; Candotti, Fabio

2017-01-01

BACKGROUND. Autologous hematopoietic stem cell transplantation (HSCT) of gene-modified cells is an alternative to enzyme replacement therapy (ERT) and allogeneic HSCT that has shown clinical benefit for adenosine deaminase–deficient (ADA-deficient) SCID when combined with reduced intensity conditioning (RIC) and ERT cessation. Clinical safety and therapeutic efficacy were evaluated in a phase II study. METHODS. Ten subjects with confirmed ADA-deficient SCID and no available matched sibling or family donor were enrolled between 2009 and 2012 and received transplantation with autologous hematopoietic CD34+ cells that were modified with the human ADA cDNA (MND-ADA) γ-retroviral vector after conditioning with busulfan (90 mg/m2) and ERT cessation. Subjects were followed from 33 to 84 months at the time of data analysis. Safety of the procedure was assessed by recording the number of adverse events. Efficacy was assessed by measuring engraftment of gene-modified hematopoietic stem/progenitor cells, ADA gene expression, and immune reconstitution. RESULTS. With the exception of the oldest subject (15 years old at enrollment), all subjects remained off ERT with normalized peripheral blood mononuclear cell (PBMC) ADA activity, improved lymphocyte numbers, and normal proliferative responses to mitogens. Three of nine subjects were able to discontinue intravenous immunoglobulin replacement therapy. The MND-ADA vector was persistently detected in PBMCs (vector copy number [VCN] = 0.1–2.6) and granulocytes (VCN = 0.01–0.3) through the most recent visits at the time of this writing. No patient has developed a leukoproliferative disorder or other vector-related clinical complication since transplant. CONCLUSION. These results demonstrate clinical therapeutic efficacy from gene therapy for ADA-deficient SCID, with an excellent clinical safety profile. TRIAL REGISTRATION. ClinicalTrials.gov NCT00794508. FUNDING. Food and Drug Administration Office of Orphan Product

Modified pavement cement concrete

Science.gov (United States)

Botsman, L. N.; Ageeva, M. S.; Botsman, A. N.; Shapovalov, S. M.

2018-03-01

The paper suggests design principles of pavement cement concrete, which covers optimization of compositions and structures at the stage of mixture components selection due to the use of plasticizing agents and air-retaining substances that increase the viability of a concrete mixture. It also demonstrates advisability of using plasticizing agents together with air-retaining substances when developing pavement concrete compositions, which provides for the improvement of physical and mechanical properties of concrete and the reduction of cement binding agent consumption thus preserving strength indicators. The paper shows dependences of the main physical-mechanical parameters of concrete on cement consumption, a type and amount of additives.

Analysis of cement-treated clay behavior by micromechanical approach

OpenAIRE

Zhang , Dong-Mei; Yin , Zhenyu; Hicher , Pierre Yves; Huang , Hong-Wei

2013-01-01

International audience; Experimental results show the significant influence of cement content on the mechanical properties of cement-treated clays. Cementation is produced by mixing a certain amount of cement with the saturated clay. The purpose of this paper is to model the cementation effect on the mechanical behavior of cement-treated clay. A micromechanical stress-strain model is developed considering explicitly the cementation at inter-cluster contacts. The inter-cluster bonding and debo...

The economics of using prophylactic antibiotic-loaded bone cement in total knee replacement.

Science.gov (United States)

Gutowski, C J; Zmistowski, B M; Clyde, C T; Parvizi, J

2014-01-01

The rate of peri-prosthetic infection following total joint replacement continues to rise, and attempts to curb this trend have included the use of antibiotic-loaded bone cement at the time of primary surgery. We have investigated the clinical- and cost-effectiveness of the use of antibiotic-loaded cement for primary total knee replacement (TKR) by comparing the rate of infection in 3048 TKRs performed without loaded cement over a three-year period versus the incidence of infection after 4830 TKRs performed with tobramycin-loaded cement over a later period of time of a similar duration. In order to adjust for confounding factors, the rate of infection in 3347 and 4702 uncemented total hip replacements (THR) performed during the same time periods, respectively, was also examined. There were no significant differences in the characteristics of the patients in the different cohorts. The absolute rate of infection increased when antibiotic-loaded cement was used in TKR. However, this rate of increase was less than the rate of increase in infection following uncemented THR during the same period. If the rise in the rate of infection observed in THR were extrapolated to the TKR cohort, 18 additional cases of infection would have been expected to occur in the cohort receiving antibiotic-loaded cement, compared with the number observed. Depending on the type of antibiotic-loaded cement that is used, its cost in all primary TKRs ranges between USD $2112.72 and USD $112 606.67 per case of infection that is prevented.

Leach characterization of cement encapsulated wastes

International Nuclear Information System (INIS)

Roy, D.M.; Scheetz, B.E.; Wakeley, L.D.; Barnes, M.W.

1982-01-01

Matrix encapsulation of defense nuclear waste as well as intermediate-level commercial wastes within a low-temperature cementitious composite were investigated. The cements for this study included both as-received and modified calcium silicate and calcium aluminate cements. Specimens were prepared following conventional formulation techniques designed to produce dense monoliths, followed by curing at 60 0 C. An alternative preparation procedure is contrasted in which the specimens were ''warm'' pressed in a uniaxial press at 150 0 C at 50,000 psi for 0.5 h. Specimens of the waste/cement composites were leached in deionized water following three different procedures which span a wide range of temperatures and solution saturation conditions. Aluminate and compositionally adjusted silicate cements exhibited a better retentivity for Cs and Sr than did the as-received silicate cement. 15 refs

Cement production from coal conversion residues

International Nuclear Information System (INIS)

Brown, L.D.; Clavenna, L.R.; Eakman, J.M.; Nahas, N.C.

1981-01-01

Cement is produced by feeding residue solids containing carbonaceous material and ash constituents obtained from converting a carbonaceous feed material into liquids and/or gases into a cement-making zone and burning the carbon in the residue solids to supply at least a portion of the energy required to convert the solids into cement

Calcium Orthophosphate Cements and Concretes

Directory of Open Access Journals (Sweden)

Sergey V. Dorozhkin

2009-03-01

Full Text Available In early 1980s, researchers discovered self-setting calcium orthophosphate cements, which are a bioactive and biodegradable grafting material in the form of a powder and a liquid. Both phases form after mixing a viscous paste that after being implanted, sets and hardens within the body as either a non-stoichiometric calcium deficient hydroxyapatite (CDHA or brushite, sometimes blended with unreacted particles and other phases. As both CDHA and brushite are remarkably biocompartible and bioresorbable (therefore, in vivo they can be replaced with newly forming bone, calcium orthophosphate cements represent a good correction technique for non-weight-bearing bone fractures or defects and appear to be very promising materials for bone grafting applications. Besides, these cements possess an excellent osteoconductivity, molding capabilities and easy manipulation. Furthermore, reinforced cement formulations are available, which in a certain sense might be described as calcium orthophosphate concretes. The concepts established by calcium orthophosphate cement pioneers in the early 1980s were used as a platform to initiate a new generation of bone substitute materials for commercialization. Since then, advances have been made in the composition, performance and manufacturing; several beneficial formulations have already been introduced as a result. Many other compositions are in experimental stages. In this review, an insight into calcium orthophosphate cements and concretes, as excellent biomaterials suitable for both dental and bone grafting application, has been provided.

Development of a biodegradable bone cement

International Nuclear Information System (INIS)

Yusof Abdullah; Nurhaslinda Ee Abdullah; Wee Pee Chai; Norita Mohd Zain

2002-01-01

Biodegradable bone cement is a newly developed bone repair material, which is able to give immediate support to the implant area, and does not obstruct the bone repairing and regeneration process through appropriate biodegradation rate, which is synchronized with the mechanical load it should bear. The purpose of this study is to locally produce biodegradable bone cement using HA as absorbable filler. The cement is composed of an absorbable filler and unsaturated polyester for 100% degradation. Cross-linking effect is achieved through the action of poly (vinyl pyrrol lidone) (PVP) and an initiator. On the other hand, PPF was synthesized using direct esterification method. Characteristics of the bone cement were studied; these included the curing time, cross-linking effect and curing temperature. The products were characterized using X-Ray diffraction (XRD) to perform phase analysis and Scanning Electrons Microscopes to determine the morphology. The physical and mechanical properties of the bone cement were also investigated. The biocompatibility of the bone cement was tested using simulated body physiological solution. (Author)

Thermo-cured glass ionomer cements in restorative dentistry.

Science.gov (United States)

Gorseta, Kristina; Glavina, Domagoj

2017-01-01

Numerous positive properties of glass ionomer cements including biocompatibility, bioactivity, releasing of fluoride and good adhesion to hard dental tissue even under wet conditions and easy of handling are reasons for their wide use in paediatric and restorative dentistry. Their biggest drawbacks are the weaker mechanical properties. An important step forward in improving GIC's features is thermo-curing with the dental polymerization unit during setting of the material. Due to their slow setting characteristics the GIC is vulnerable to early exposure to moisture. After thermo curing, cements retain all the benefits of GIC with developed better mechanical properties, improved marginal adaptation, increased microhardness and shear bond strength. Adding external energy through thermocuring or ultrasound during the setting of conventional GIC is crucial to achieve faster and better initial mechanical properties. Further clinical studies are needed to confirm these findings.

21 CFR 888.3027 - Polymethylmethacrylate (PMMA) bone cement.

Science.gov (United States)

2010-04-01

... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Polymethylmethacrylate (PMMA) bone cement. 888... Polymethylmethacrylate (PMMA) bone cement. (a) Identification. Polymethylmethacrylate (PMMA) bone cement is a device...: Polymethylmethacrylate (PMMA) Bone Cement.” [67 FR 46855, July 17, 2002] ...

Effects on Setting, Strength, Moisture Resistance and Linear Changes of Sorel’s Cement on Mixing Portland Cement as an Additive

OpenAIRE

Mathur, Ritu; Chandrawat, M. P. S.; Sharma, Sanjay K.

2009-01-01

Magnesium oxysulphate cement (MOC, Magnesia / Sorel’s Cement), discovered by Sorel S.T. in 1867 and has versatile cementing characteristics. It is prepared by the reaction of magnesium sulphate with magnesia in aqueous solution. Dolomite is used as inert filler to absorb the heat evolved during the exothermic formations of oxysulphate cement. Additives play an important role to modify the properties of Sorel’s cement by nullifying the harmful effects of the impurities present in the matrix...

Cement-based materials' characterization using ultrasonic attenuation

Science.gov (United States)

Punurai, Wonsiri

The quantitative nondestructive evaluation (NDE) of cement-based materials is a critical area of research that is leading to advances in the health monitoring and condition assessment of the civil infrastructure. Ultrasonic NDE has been implemented with varying levels of success to characterize cement-based materials with complex microstructure and damage. A major issue with the application of ultrasonic techniques to characterize cement-based materials is their inherent inhomogeneity at multiple length scales. Ultrasonic waves propagating in these materials exhibit a high degree of attenuation losses, making quantitative interpretations difficult. Physically, these attenuation losses are a combination of internal friction in a viscoelastic material (ultrasonic absorption), and the scattering losses due to the material heterogeneity. The objective of this research is to use ultrasonic attenuation to characterize the microstructure of heterogeneous cement-based materials. The study considers a real, but simplified cement-based material, cement paste---a common bonding matrix of all cement-based composites. Cement paste consists of Portland cement and water but does not include aggregates. First, this research presents the findings of a theoretical study that uses a set of existing acoustics models to quantify the scattered ultrasonic wavefield from a known distribution of entrained air voids. These attenuation results are then coupled with experimental measurements to develop an inversion procedure that directly predicts the size and volume fraction of entrained air voids in a cement paste specimen. Optical studies verify the accuracy of the proposed inversion scheme. These results demonstrate the effectiveness of using attenuation to measure the average size, volume fraction of entrained air voids and the existence of additional larger entrapped air voids in hardened cement paste. Finally, coherent and diffuse ultrasonic waves are used to develop a direct

EVALUATION OF THE THIXOTROPY OF OIL-WELL CEMENTS USED FOR CEMENTING LOST CIRCULATION ZONES: EFFECT OF PLASTER AND BLAST FURNACE SLAG

Directory of Open Access Journals (Sweden)

T. Bouziani

2015-08-01

Full Text Available Cementing of oil and gas wells can be a very delicate operation. Among the concerns of service companies, during this operation are the nature and conditions of the formations in well. This is the case of cementing operations in southern Algeria, specifically on the fields of In-Amen, where the formations in lost zones are naturally weak and highly permeable. In these areas, drilling fluids (muds and cements pumped will be, completely or partially lost, what we call "lost circulation". Thixotropic cements are useful to overcome lost circulation problems. They are characterized by a special rheological behavior, allowing it to plug lost zones when they are pumped.Our work aims to assess the thixotropy of cements perapred with two types of cement (class G Asland cement and CEM I 42.5 portland cement with the plaster, using a viscometer with coaxial cylinder (couette type. Moreover, the effect of blast furnace slag (LHF on the properties and thixotropic mixtures prepared was also studied. The results show that portland cement (available locally can produce mixes with higher and more stable thixotropy than the class G cement (from importation, which is a practical and economical for cementing job operations in wells with loss zones. The results also show that the effect of LHF is positive, since in addition to his contribution to long term performances, especially the durability of hardened concrete, it improves the thixotropy of cement made of plaster.

Influence of agglomeration of a recycled cement additive on the hydration and microstructure development of cement based materials

NARCIS (Netherlands)

Yu, R.; Shui, Z.H.

2013-01-01

This paper presents a study, including experimental and mechanism analysis, on investigating the effect of agglomeration of a recycled cement additive on the hydration and microstructure development of cement based materials. The recycled additive is firstly produced form waste hardened cement paste

21 CFR 872.3275 - Dental cement.

Science.gov (United States)

2010-04-01

... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Dental cement. 872.3275 Section 872.3275 Food and... DENTAL DEVICES Prosthetic Devices § 872.3275 Dental cement. (a) Zinc oxide-eugenol—(1) Identification... filling or as a base cement to affix a temporary tooth filling, to affix dental devices such as crowns or...

Clinical Applications of Mesenchymal Stem Cells in Chronic Diseases

Directory of Open Access Journals (Sweden)

Andrea Farini

2014-01-01

Full Text Available Extraordinary progress in understanding several key features of stem cells has been made in the last ten years, including definition of the niche, and identification of signals regulating mobilization and homing as well as partial understanding of the mechanisms controlling self-renewal, commitment, and differentiation. This progress produced invaluable tools for the development of rational cell therapy protocols that have yielded positive results in preclinical models of genetic and acquired diseases and, in several cases, have entered clinical experimentation with positive outcome. Adult mesenchymal stem cells (MSCs are nonhematopoietic cells with multilineage potential to differentiate into various tissues of mesodermal origin. They can be isolated from bone marrow and other tissues and have the capacity to extensively proliferate in vitro. Moreover, MSCs have also been shown to produce anti-inflammatory molecules which can modulate humoral and cellular immune responses. Considering their regenerative potential and immunoregulatory effect, MSC therapy is a promising tool in the treatment of degenerative, inflammatory, and autoimmune diseases. It is obvious that much work remains to be done to increase our knowledge of the mechanisms regulating development, homeostasis, and tissue repair and thus to provide new tools to implement the efficacy of cell therapy trials.

Diffusion of radon through varying depths of cement

International Nuclear Information System (INIS)

Takriti, S.; Shweikani, R.; Ali, A.F.; Hushari, M.; Kheitou, M.

2001-01-01

Portland cement was mixed with different concentrations of radium chloride (1200, 2400 and 3600 Bq) to produce radioactive sources. These sources were surrounded with cement of different thickness (1, 2 and 4 cm). The release of radon from these sources (before and after being surrounded) was studied. The results showed that radon release from the sources itself was less then its release from the same source after being surrounded by cement, and the release did not change with the thickness of cement. Samples were covered with a thin layer of polyethylene before being surrounded with cement. It was found that this additional layer reduced the radon exhalation. This thin layer stopped any reaction between the source and the surrounding cement during solidification of the cement layers. These reactions are thought to be the reason for the increase of radon exhalation from the sources surrounded by cement

Effect of power toothbrushing on simulated wear of dental cement margins.

Science.gov (United States)

Black, Marsha A; Bayne, Stephen C; Peterson, Charlotte A

2007-01-01

Power toothbrushes (PTBs), in combination with abrasive dentifrices, may encourage wear of dental cements at crown margins. The objective of this in vitro simulation was to control the clinical variables associated with PTB use and measure the potential side effects of PTBs with mild and abrasive dentifrices. Four PTBs ( Braun-Oral-B-Professional Care at 150 g brushing force, Sonicare-Elite at 90 g, Colgate-Actibrush at 200 g and Crest-Spinbrush-Pro at 250 g) and 2 dentifrices mixed 1:1 with tap water (Mild= Colgate-Total, Colgate-Palmolive; Abrasive= Close-up, Chesebrough-Ponds) versus tap water alone (control) were used to abrade 2 cements (Fleck's Mizzy Zinc Phosphate [ZP]; 3M-ESPE Unicem universal cement [UC]) using cement-filled slots (160 m wide) cut into wear-resistant ceramic blocks. A custom fixture controlled PTB/block alignment, PTB loads, and other testing variables. Wear was measured (3 profilometer traces/slot, 5 slots/block/group, baseline to 5-year differences) and analyzed (3-way ANOVA, p PTBs and both dentifrices. Brushing with water showed no effects (pPTBs. Pooled 5y-wear levels for ZP for both dentifrices approximately 21 microm /5y) were similar to values for current-day posterior composite materials. Combinations of PTBs with mild and abrasive dentifrices produced significant wear with ZP but not UC; thus, resin-composite cements seem to represent a better choice for wear resistance.

Alternative Fuels in Cement Production

DEFF Research Database (Denmark)

Larsen, Morten Boberg

The substitution of alternative for fossil fuels in cement production has increased significantly in the last decade. Of these new alternative fuels, solid state fuels presently account for the largest part, and in particular, meat and bone meal, plastics and tyre derived fuels (TDF) accounted...... for the most significant alternative fuel energy contributors in the German cement industry. Solid alternative fuels are typically high in volatile content and they may differ significantly in physical and chemical properties compared to traditional solid fossil fuels. From the process point of view......, considering a modern kiln system for cement production, the use of alternative fuels mainly influences 1) kiln process stability (may accelerate build up of blockages preventing gas and/or solids flow), 2) cement clinker quality, 3) emissions, and 4) decreased production capacity. Kiln process stability...

Stabilization/solidification of selenium-impacted soils using Portland cement and cement kiln dust.

Science.gov (United States)

Moon, Deok Hyun; Grubb, Dennis G; Reilly, Trevor L

2009-09-15

Stabilization/solidification (S/S) processes were utilized to immobilize selenium (Se) as selenite (SeO(3)(2-)) and selenate (SeO(4)(2-)). Artificially contaminated soils were prepared by individually spiking kaolinite, montmorillonite and dredged material (DM; an organic silt) with 1000 mg/kg of each selenium compound. After mellowing for 7 days, the Se-impacted soils were each stabilized with 5, 10 and 15% Type I/II Portland cement (P) and cement kiln dust (C) and then were cured for 7 and 28 days. The toxicity characteristic leaching procedure (TCLP) was used to evaluate the effectiveness of the S/S treatments. At 28 days curing, P doses of 10 and 15% produced five out of six TCLP-Se(IV) concentrations below 10mg/L, whereas only the 15% C in DM had a TCLP-Se(IV) concentration soil-cement slurries aged for 30 days enabled the identification of Se precipitates by X-ray powder diffraction (XRD) and scanning electron microscopy (SEM)-energy dispersive X-ray spectroscopy (EDX). XRD and SEM-EDX analyses of the Se(IV)- and Se(VI)-soil-cement slurries revealed that the key selenium bearing phases for all three soil-cement slurries were calcium selenite hydrate (CaSeO(3).H(2)O) and selenate substituted ettringite (Ca(6)Al(2)(SeO(4))(3)(OH)(12).26H(2)O), respectively.

Treatment of a Vertical Root Fracture Using Dual-Curing Resin Cement: A Case Report

Directory of Open Access Journals (Sweden)

Nima Moradi Majd

2012-01-01

Full Text Available Introduction. Vertical root fracture (VRF is one of the most frustrating complications of root canal treatment. The prognosis of the root with VRF is poor therefore tooth extraction and root amputation are usually the only treatment options. However, bonding of the fracture line with adhesive resin cement during the intentional replantation procedure was recently suggested as an alternative to tooth extraction. Methods. A vertically fractured left maxillary incisor was carefully extracted, fracture line was treated with adhesive resin cement, a retrograde cavity was produced and filled with calcium-enriched mixture (CEM cement, and tooth was replanted. Results. After 12 months the tooth was asymptomatic. The size of periapical radiolucency was noticeably reduced and there was no clinical sign of ankylosis. Conclusion. Using adhesive resin cement to bond the fracture lines extraorally in roots with VRF and intentional replantation of the reconstructed teeth could be considered as an alternative to tooth extraction, especially for anterior teeth.

Applicability of low alkalinity cement for construction and alteration of bentonite in the cement

International Nuclear Information System (INIS)

Iriya, K.; Fujii, K.; Kubo, H.; Uegaki, Y.

2002-02-01

A concept of radioactive waste repository in which both bentonite and cementitious materials exist in deep cavern as engineered barriers is proposed. It is pointed out that pore water of cement is approximately 12.0 to 13.0 of pH and that it maintains for a long period. Therefore alteration of bentonite and rocks should be studied. Mixing test upon some interaction between modeled cement water and bentonite and rocks have been carried out since 1995 as a part of TRU repository's study. And low alkalinity of cement has been studied as parallel to study on alteration of bentonite. HFSC which has high fly ash content and which shows approximately 10.5 to 11.0 of pH of pore water was developed. Cementitious materials are generally use as a combination with steel, since its tensile strength is low. The corrosion of steel in concrete becomes a big problem in case of decreasing pH of cement. There is little available reference, since low alkalinity cement is quite new and special ordered one. Accelerating test for corrosion in low alkalinity concrete were carried out in order to collect data of corrosion. Although alteration of bentonite by several types of modeled cement water was tested. Long term test by actual cement pore water has not carried out. The alteration in 360 days was investigated. Conclusion obtained in this study is following. Corrosion of steel (re-bar) 1) Re-bar in HFSC with 60% of W/C is significantly corroded. The corrosion rate is bigger than the rate of ordinary used cement. 2) Diffusivity of Cl - ion in HFSC is similar to it in OPC comparing by the same water powder ratio. 3) Corrosion rate of HFSC 30 is similar to OPC60. However corrosion is progressed in HFSC 30 without Cl - ion due to lower alkalinity, but it isn't done in OPC within a certain amount of Cl - ion. Alteration of bentonite and rocks 1) Although no secondary minerals was observed in HFSC, monmorironite is gradually lost by increasing calcite. 2) Secondary minerals were observed in

Estimation and measurement of porosity change in cement paste

International Nuclear Information System (INIS)

Lee, Eunyong; Jung, Haeryong; Kwon, Ki-jung; Kim, Do-Gyeum

2011-01-01

Laboratory-scale experiments were performed to understand the porosity change of cement pastes. The cement pastes were prepared using commercially available Type-I ordinary Portland cement (OPC). As the cement pastes were exposed in water, the porosity of the cement pastes sharply increased; however, the slow decrease of porosity was observed as the dissolution period was extended more than 50 days. As expected, the dissolution reaction was significantly influenced by w/c ratio and the ionic strength of solution. A thermodynamic model was applied to simulate the porosity change of the cement pastes. It was highly influenced by the depth of the cement pastes. There was porosity increase on the surface of the cement pastes due to dissolution of hydration products, such as portlandite, ettringite, and CSH. However, the decrease of porosity was estimated inside the cement pastes due to the precipitation of cement minerals. (author)