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Sample records for primary enamel knot

  1. Caspase 3 activation in the primary enamel knot of developing molar tooth

    Czech Academy of Sciences Publication Activity Database

    Matalová, Eva; Kovářů, František; Míšek, Ivan

    2006-01-01

    Roč. 55, 2 (2006), s. 183-188 ISSN 0862-8408 R&D Projects: GA ČR GA304/04/0101; GA AV ČR KJB500450503; GA MŠk OC B23.001 Institutional research plan: CEZ:AV0Z50450515 Keywords : apoptosis * caspase 3 * primary enamel knot Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 2.093, year: 2006

  2. Cell proliferation and apoptosis in the primary enamel knot measured by flow cytometry of laser microdissected samples

    Czech Academy of Sciences Publication Activity Database

    Matalová, Eva; Dubská, L.; Fleischmannová, Jana; Chlastáková, Ivana; Janečková, Eva; Tucker, A. S.

    2010-01-01

    Roč. 55, č. 8 (2010), s. 570-575 ISSN 0003-9969 R&D Projects: GA AV ČR KJB500450802; GA AV ČR IAA600450904; GA ČR GA203/08/1680 Institutional research plan: CEZ:AV0Z50450515 Keywords : Laser capture microdissection * Flow cytometry * Primary enamel knot Subject RIV: EA - Cell Biology Impact factor: 1.463, year: 2010

  3. Sprouty gene dosage influences temporal-spatial dynamics of primary enamel knot formation

    Czech Academy of Sciences Publication Activity Database

    Lochovská, Kateřina; Peterková, Renata; Pavlíková, Zuzana; Hovořáková, Mária

    2015-01-01

    Roč. 15, APR 22 (2015), s. 21 ISSN 1471-213X R&D Projects: GA ČR(CZ) GAP305/12/1766; GA ČR GB14-37368G Institutional support: RVO:68378041 Keywords : enamel knot * tooth development * mouse molar * sprouty genes * sonic hedgehog * cre-loxp system * supernumerary tooth Subject RIV: EA - Cell Biology Impact factor: 2.096, year: 2015

  4. Demineralization of Enamel in Primary Second Molars Related to Properties of the Enamel

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    N. Sabel

    2012-01-01

    Full Text Available Enamel structure is of importance in demineralization. Differences in porosity in enamel effect the rate of demineralization, seen between permanent and deciduous teeth. Individual differences have been shown in the mean mineral concentration values in enamel, the role of this in demineralization is not thoroughly investigated. The aim of this study was to study variations of depths of artificial lesions of demineralization and to analyze the depth in relation to variations in the chemical and mineral composition of the enamel. A demineralized lesion was created in second primary molars from 18 individuals. Depths of lesions were then related to individual chemical content of the enamel. Enamel responded to demineralization with different lesion depths and this was correlated to the chemical composition. The carbon content in sound enamel was shown to be higher where lesions developed deeper. The lesion was deeper when the degree of porosity of the enamel was higher.

  5. Determination of fracture toughness of human permanent and primary enamel using an indentation microfracture method.

    Science.gov (United States)

    Hayashi-Sakai, Sachiko; Sakai, Jun; Sakamoto, Makoto; Endo, Hideaki

    2012-09-01

    The purpose of the present study was to examine the fracture toughness and Vickers microhardness number of permanent and primary human enamel using the indentation microfracture method. Crack resistance and a parameter indirectly related to fracture toughness were measured in 48 enamel specimens from 16 permanent teeth and 12 enamel specimens obtained from six primary teeth. The Vickers microhardness number of the middle portion was greater than the upper portion in primary enamel. The fracture toughness was highest in the middle portion of permanent enamel, because fracture toughness greatly depends upon microstructure. These findings suggest that primary teeth are not miniature permanent teeth but have specific and characteristic mechanical properties.

  6. Microstructural analysis of demineralized primary enamel after in vitro toothbrushing

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    Neves Aline de Almeida

    2002-01-01

    Full Text Available The aim of this study was to investigate, in vitro, the morphological characteristics of demineralized primary enamel subjected to brushing with a dentifrice with or without fluoride. In order to do so, 32 enamel blocks were divided in 4 different groups containing 8 blocks each. They were separately immersed in artificial saliva for 15 days. The experimental groups were: C - control; E - submitted to etching with 37% phosphoric acid gel (30 s; EB - submitted to etching and brushing 3 times a day with a non-fluoridated dentifrice; EBF = submitted to etching and brushing 3 times a day with a fluoridated dentifrice. The toothbrushing force was standardized at 0.2 kgf and 15 double strokes were performed on each block. After the experimental period, the samples were prepared and examined under SEM. The control group (C showed a smooth surface, presenting scratches caused by habitual toothbrushing. The etched samples (E exhibited different degrees of surface disintegration, but the pattern of acid etching was predominantly the type II dissolution. The brushed surfaces were smooth, with elevations which corresponded to the exposure of Tomes? process pits and depressions which corresponded to interrod enamel. Particles resembling calcium carbonate were found in the most protected parts of the grooves. No morphological differences were observed between brushing with fluoridated (EBF and non-fluoridated (EB dentifrice. The results suggest that the mechanical abrasion caused by brushing demineralized enamel with dentifrice smoothes the rough etched surface, and the presence of fluoride does not cause morphological modifications in this pattern.

  7. Demineralization of Enamel in Primary Second Molars Related to Properties of the Enamel

    OpenAIRE

    Sabel, N.; Robertson, A.; Nietzsche, S.; Norén, J. G.

    2012-01-01

    Enamel structure is of importance in demineralization. Differences in porosity in enamel effect the rate of demineralization, seen between permanent and deciduous teeth. Individual differences have been shown in the mean mineral concentration values in enamel, the role of this in demineralization is not thoroughly investigated. The aim of this study was to study variations of depths of artificial lesions of demineralization and to analyze the depth in relation to variations in the chemical an...

  8. MicroCT study on the enamel mineral density of primary molars

    NARCIS (Netherlands)

    Elfrink, M.E.C.; Kalin, K.; van Ruijven, L.J.; ten Cate, J.M.; Veerkamp, J.S.J.

    2016-01-01

    Aim The aim of this study is to report on the mineral density of the enamel of primary molars related to the age of the child and to compare the mineral density of sound and carious enamel in those molars. Materials and methods This study included 23 children and 41 extracted primary molars. The

  9. Enamel Defects of Human Primary Dentition as Virtual Memory of Early Developmental Events

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    Naser Asl Aminabadi

    2009-12-01

    Full Text Available Background and aims. The objectives of the present study were to investigate the prevalence and the position of enamel defects of primary teeth and hence to estimate the approximate time of an insult. Material and methods. 121 children aged 3 to 5 years were included in the study. The Modified Developmental Defects of Enamel Index was used to diagnose and classify the defects. The defects were categorized as hypoplasia, hypocalcification or a combination of them. Each tooth was investigated for occlusal/incisal, middle, cervical, incisomiddle, cervicomiddle and complete crown defects. Results. 55.37% of the children were affected by enamel defects, 23.96% being categorized as hypocalcification and 22.31% as hypoplasia. The enamel defects were more abundant in maxillary primary incisors and mandibular primary canines. Minimum involvement was seen in maxillary primary second molars and mandibular primary lateral incisors. The prevalence of cervical defects in maxillary primary incisors was significantly more than the middle or incisal defects (P < 0.05. The prevalence of incisal defects in mandibular primary incisors was significantly more than the middle or cervical defects (P < 0.05. Conclusions. The results revealed a considerable number of enamel defects which are multiple, symmetric and chronologically accordant with the estimated neonatal line in primary teeth of healthy children.

  10. Primary enamel knot cell death in Apaf-1 and caspase-9 deficient mice

    Czech Academy of Sciences Publication Activity Database

    Šetková, Jana; Matalová, Eva; Sharpe, P. T.; Míšek, Ivan; Tucker, A. S.

    2007-01-01

    Roč. 52, 1 (2007), s. 15-19 ISSN 0003-9969 R&D Projects: GA AV ČR KJB500450503; GA ČR GA304/04/0101; GA MŠk OC B23.001 Institutional research plan: CEZ:AV0Z50450515 Keywords : dental apoptosis * apoptosome * apaf-1 knockout * caspase-9 knockout Subject RIV: FF - HEENT, Dentistry Impact factor: 1.554, year: 2007

  11. Selective Acid Etching Improves the Bond Strength of Universal Adhesive to Sound and Demineralized Enamel of Primary Teeth.

    Science.gov (United States)

    Antoniazzi, Bruna Feltrin; Nicoloso, Gabriel Ferreira; Lenzi, Tathiane Larissa; Soares, Fabio Zovico Maxnuck; Rocha, Rachel de Oliveira

    To evaluate the influence of enamel condition and etching strategy on bond strength of a universal adhesive in primary teeth. Thirty-six primary molars were randomly assigned to six groups (n = 6) according to the enamel condition (sound [S] and demineralized [DEM]/cariogenic challenge by pH cycling prior to restorative procedures) and adhesive system (Scotchbond Universal Adhesive [SBU]) used in either etch-and-rinse (ER) or selfetching (SE) mode, with Clearfil SE Bond as the self-etching control. The adhesives were applied to flat enamel surfaces and composite cylinders (0.72 mm2) were built up. After 24-h storage in water, specimens were subjected to the microshear test. Bond strength (MPa) data were analyzed using two-way ANOVA and Tukey's post-hoc tests (α = 0.05). Significant differences were found considering the factors adhesive system (p = 0.003) and enamel condition (p = 0.001). Demineralized enamel negatively affected the bond strength, with μSBS values approximately 50% lower than those obtained for sound enamel. SBU performed better in etch-and-rinse mode, and the bond strength found for SBU applied in self-etching mode was similar to that of CSE. Enamel etching with phosphoric acid improves the bond strength of a universal adhesive system to primary enamel. Demineralized primary enamel results in lower bond strength.

  12. Effect of Popping Chocolate and Candy on Enamel Microhardness of Primary and Permanent Teeth.

    Science.gov (United States)

    Tabari, Mitra; Alaghemand, Homayoon; Qujeq, Durdi; Mohammadi, Elahe

    2017-01-01

    Dental erosion is a common disease in children. Food diets, due to high amounts of juice, soft drinks, chewing gum, and acidic chocolate, are one of the most important risk factors in erosive processes among children. The aim of this study was to evaluate the effect of candy and chocolate on the microhardness of tooth enamel. Two types of popping candy and one type of popping chocolate were used in this study. Thirty-three healthy permanent premolar teeth and 33 primary incisor teeth (A or B) were selected. Five grams of each popping chocolate or candy was dissolved with 2 ml of artificial saliva. Subsequently, their pH and titrable acidity (TA) as well as microhardness and surface roughness of enamel were examined in the laboratory. Data were analyzed and evaluated Released 2011. IBM SPSS Statistics for Windows, Version 20.0. Armonk, NY through independent t -test, paired t -test, Tukey test, and ANOVA. The results of this study showed that only the pH of the candies was below the critical pH of the enamel (5.5) and their TA was B = 0.20 and C = 0.21. The most significant effect on the enamel microhardness of the permanent and primary teeth was by the following types of candy: orange flavor (C), strawberry flavor (B), and chocolate (A), respectively. This difference was significant ( P < 0.001) and the surface roughness increased after exposure. This study showed that popping chocolate and candy reduces microhardness of enamel.

  13. Analysis of enamel microbiopsies in shed primary teeth by Scanning Electron Microscopy (SEM) and Polarizing Microscopy (PM)

    International Nuclear Information System (INIS)

    Costa de Almeida, Glauce Regina; Molina, Gabriela Ferian; Meschiari, Cesar Arruda; Barbosa de Sousa, Frederico; Gerlach, Raquel Fernanda

    2009-01-01

    The aims of this study were 1) to verify how close to the theoretically presumed areas are the areas of enamel microbiopsies carried out in vivo or in exfoliated teeth; 2) to test whether the etching solution penetrates beyond the tape borders; 3) to test whether the etching solution demineralizes the enamel in depth. 24 shed upper primary central incisors were randomly divided into two groups: the Rehydrated Teeth Group and the Dry Teeth Group. An enamel microbiopsy was performed, and the enamel microbiopsies were then analyzed by Scanning Electron Microscopy (SEM) and Polarizing Microscopy (PM). Quantitative birefringence measurements were performed. The 'true' etched area was determined by measuring the etched enamel using the NIH Image analysis program. Enamel birefringence was compared using the paired t test. There was a statistically significant difference when the etched areas in the Rehydrated teeth were compared with those of the Dry teeth (p = 0.04). The etched areas varied from - 11.6% to 73.5% of the presumed area in the Rehydrated teeth, and from 6.6% to 61.3% in the Dry teeth. The mean percentage of variation in each group could be used as a correction factor for the etched area. Analysis of PM pictures shows no evidence of in-depth enamel demineralization by the etching solution. No statistically significant differences in enamel birefringence were observed between values underneath and outside the microbiopsy area in the same tooth, showing that no mineral loss occurred below the enamel superficial layer. Our data showed no evidence of in-depth enamel demineralization by the etching solution used in the enamel microbiopsy proposed for primary enamel. This study also showed a variation in the measured diameter of the enamel microbiopsy in nineteen teeth out of twenty four, indicating that in most cases the etching solution penetrated beyond the tape borders.

  14. Morphology of enamel in primary teeth from children in Thailand exposed to environmental lead

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    Youravong, Nattaporn [Epidemiology Unit, Faculty of Medicine, Prince of Songkla University, Songkhla (Thailand); Chongsuvivatwong, Virasakdi [Epidemiology Unit, Faculty of Medicine, Prince of Songkla University, Songkhla (Thailand); Teanpaisan, Rawee [Department of Stomatology, Faculty of Dentistry, Prince of Songkla University, Songkhla (Thailand); Geater, Alan F. [Epidemiology Unit, Faculty of Medicine, Prince of Songkla University, Songkhla (Thailand); Dietz, Wolfram [Centre of Electron Microscopy, Friedrich-Schiller-University Jena (Germany); Dahlen, Gunnar [Department of Oral Microbiology, Faculty of Odontology, Goeteborg University (Sweden); Noren, Joergen G. [Department of Pedodontics, Faculty of Odontology, Goeteborg University, Box 450 SE-405 30 Goeteborg (Sweden)]. E-mail: Jorgen.noren@odontologi.gu.se

    2005-09-15

    Lead is one of the major environmental pollutants and a health risk. Dental hard tissues have a capacity to accumulate lead from the environment. Eighty exfoliated primary teeth were collected from children residing around a shipyard area in southern Thailand, known for its lead contamination. The morphology of the enamel was examined by polarized light microscopy (PLM), microradiography (MRG), and scanning electron microscopy (SEM). The specimens derived from two groups of children, one group with high blood levels of lead (57 teeth) and one group having low blood levels of lead (23 teeth). The enamel irrespective of group appeared normal. However, in a majority of the specimens the enamel surface appeared hypomineralized, which was confirmed in SEM. No morphological changes connected to lead in blood could be found. The hypomineralized surface zone could possibly be attributed to an acid oral environment.

  15. Morphology of enamel in primary teeth from children in Thailand exposed to environmental lead

    International Nuclear Information System (INIS)

    Youravong, Nattaporn; Chongsuvivatwong, Virasakdi; Teanpaisan, Rawee; Geater, Alan F.; Dietz, Wolfram; Dahlen, Gunnar; Noren, Joergen G.

    2005-01-01

    Lead is one of the major environmental pollutants and a health risk. Dental hard tissues have a capacity to accumulate lead from the environment. Eighty exfoliated primary teeth were collected from children residing around a shipyard area in southern Thailand, known for its lead contamination. The morphology of the enamel was examined by polarized light microscopy (PLM), microradiography (MRG), and scanning electron microscopy (SEM). The specimens derived from two groups of children, one group with high blood levels of lead (57 teeth) and one group having low blood levels of lead (23 teeth). The enamel irrespective of group appeared normal. However, in a majority of the specimens the enamel surface appeared hypomineralized, which was confirmed in SEM. No morphological changes connected to lead in blood could be found. The hypomineralized surface zone could possibly be attributed to an acid oral environment

  16. Microtensile bond strength of contemporary adhesives to primary enamel and dentin.

    Science.gov (United States)

    Marquezan, Marcela; da Silveira, Bruno Lopes; Burnett, Luiz Henrique; Rodrigues, Célia Regina Martins Delgado; Kramer, Paulo Floriani

    2008-01-01

    The purpose of this study was to assess bond strength of three self-etching and two total-etch adhesive systems bonded to primary tooth enamel and dentin. Forty extracted primary human molars were selected and abraded in order to create flat buccal enamel and occlusal dentin surfaces. Teeth were assigned to one of the adhesive systems: Adper Scotch Bond Multi Purpose, Adper Single Bond 2, Adper Prompt L-Pop, Clearfil SE Bond and AdheSE. Immediately to adhesive application, a composite resin (Filtek Z250) block was built up. After 3 months of water storage, each sample was sequentially sectioned in order to obtain sticks with a square cross-sectional area of about 0.72 mm2. The specimens were fixed lengthways to a microtensile device and tested using a universal testing machine with a 50-N load cell at a crosshead speed of 0.5 mm/min. Microtensile bond strength values were recorded in MPa and compared by Analysis of Variance and the post hoc Tukey test (a = 0.05). In enamel, Clearfil SE Bond presented the highest values, followed by Adper Single Bond 2, AdheSE and Adper Scotch Bond Multi Purpose, without significant difference. The highest values in dentin were obtained with Adper Scotch Bond Multi Purpose and all other adhesives did not present significant different values from that, except Adper Prompt L-Pop that achieved the lowest bond strength in both substrates. Adper Scotch Bond Multi Purpose and Adper Single Bond 2 presented significantly lower values in enamel than in dentin although all other adhesives presented similar results in both substrates. contemporary adhesive systems present similar behaviors when bonded to primary teeth, with the exception of the one-step self-etching system; and self-etching systems can achieve bond strength values as good in enamel as in dentin of primary teeth.

  17. Nanostructural effect of acid-etching and fluoride application on human primary and permanent tooth enamels

    International Nuclear Information System (INIS)

    Cheong, Youjin; Choi, Samjin; Kim, So Jung; Park, Hun-Kuk

    2012-01-01

    This study examined the nanostructural effects of fluoride application and the acid-etching time with respect to the time elapsed after fluoride application on the primary and permanent tooth enamel layers using atomic force microscopy (AFM) and scanning electron microscopy (SEM). 192 non-carious teeth were assigned to sixteen experimental groups (n = 12) including primary (1 to 8) and permanent (9 to 16) teeth, based on the timing of acid-etching with 37% phosphoric acid after an acidulated phosphate fluoride (APF) pre-treatment. The APF pre-treatment led to a decrease in surface roughness in both the primary and permanent teeth. After the APF treatment, the roughness in both primary and permanent teeth increased with the time elapsed. An acid-etching time of 40 s led to increased nanostructural changes in the enamel surfaces compared to the conventional acid-etching time of 20 s. This acid-etching process led to a higher roughness changes in the primary teeth than in the permanent teeth. To obtain proper enamel adhesion of a sealant after APF pre-treatment, it is important to apply acid-etching two weeks after pre-treatment. In addition, the acid-etching time should be prolonged to apply etching more quickly than two weeks, regardless of the primary and permanent teeth. Highlights: ► APF pre-treatment led to decreased surface roughness in the enamel. ► After APF treatment, the more roughness increased with increasing time elapsed. ► Acid-etching should be performed two weeks after fluoride application.

  18. Nanostructural effect of acid-etching and fluoride application on human primary and permanent tooth enamels

    Energy Technology Data Exchange (ETDEWEB)

    Cheong, Youjin [Department of Biomedical Engineering and Healthcare Industry Research Institute, College of Medicine, Kyung Hee University, Seoul (Korea, Republic of); Choi, Samjin [Department of Biomedical Engineering and Healthcare Industry Research Institute, College of Medicine, Kyung Hee University, Seoul (Korea, Republic of); Department of Orthodontics, College of Dental Medicine, Kyung Hee University, Seoul (Korea, Republic of); Kim, So Jung [Department of Pediatric Dentistry, College of Dental Medicine, Kyung Hee University, Seoul (Korea, Republic of); Park, Hun-Kuk, E-mail: sigmoidus@khu.ac.kr [Department of Biomedical Engineering and Healthcare Industry Research Institute, College of Medicine, Kyung Hee University, Seoul (Korea, Republic of); Program of Medical Engineering, Kyung Hee University, Seoul (Korea, Republic of)

    2012-07-01

    This study examined the nanostructural effects of fluoride application and the acid-etching time with respect to the time elapsed after fluoride application on the primary and permanent tooth enamel layers using atomic force microscopy (AFM) and scanning electron microscopy (SEM). 192 non-carious teeth were assigned to sixteen experimental groups (n = 12) including primary (1 to 8) and permanent (9 to 16) teeth, based on the timing of acid-etching with 37% phosphoric acid after an acidulated phosphate fluoride (APF) pre-treatment. The APF pre-treatment led to a decrease in surface roughness in both the primary and permanent teeth. After the APF treatment, the roughness in both primary and permanent teeth increased with the time elapsed. An acid-etching time of 40 s led to increased nanostructural changes in the enamel surfaces compared to the conventional acid-etching time of 20 s. This acid-etching process led to a higher roughness changes in the primary teeth than in the permanent teeth. To obtain proper enamel adhesion of a sealant after APF pre-treatment, it is important to apply acid-etching two weeks after pre-treatment. In addition, the acid-etching time should be prolonged to apply etching more quickly than two weeks, regardless of the primary and permanent teeth. Highlights: Black-Right-Pointing-Pointer APF pre-treatment led to decreased surface roughness in the enamel. Black-Right-Pointing-Pointer After APF treatment, the more roughness increased with increasing time elapsed. Black-Right-Pointing-Pointer Acid-etching should be performed two weeks after fluoride application.

  19. Effect of foods and drinks on primary tooth enamel after erosive challenge with hydrochloric acid

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    Késsia Suênia Fidelis de MESQUITA-GUIMARÃES

    2015-01-01

    Full Text Available The aim of this study was to evaluate the effect of industrialised foods and drinks on primary tooth enamel previously eroded with hydrochloric acid (HCl. The crowns of one hundred two specimens were subjected to an erosive challenge with HCl and randomly divided into six groups (n = 17: Chocolate Milk (Toddynho® - Pepsico - negative control; Petit Suisse Yogurt (Danoninho® - Danone; Strawberry Yogurt (Vigor; Apple puree (Nestlé; Fermented Milk (Yakult® - Yakult; and Home Squeezed Style Orange Juice (del Valle - positive control. The 28-day immersion cycles for the test products were performed twice daily and were interspersed with exposure of the test substrate to artificial saliva. Measurements of enamel surface microhardness (SMH were performed initially, after immersion in HCl and at 7, 14, 21 and 28 days of experimentation. A two-way ANOVA, according to a split-plot design, followed by the sum of squares decomposition and Tukey’s test, revealed a significant effect for the interaction between Foods and Drinks and Length of Exposure (p < 0.00001. Orange juice resulted in greater mineral loss of enamel after 28 days. None of the test products was associated with recovery of tooth enamel microhardness.

  20. Erosive effects of acidic center-filled chewing gum on primary and permanent enamel

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    Bolan M

    2008-01-01

    Full Text Available Background: The higher incidence of dental erosion in children and teenagers possibly reflects a high intake of acidic food and beverages as well as a more frequent diagnosis on this condition. Aim: The aim of this study was to evaluate the erosive potential of acidic filling of chewing gum in primary and permanent enamel. Methods and Materials: Eighty enamel blocks (40 primary and 40 permanent teeth were used and randomly distributed into eight groups. Groups were divided according to types of dental substrates (permanent or primary, frequency of exposure to the acidic substance (2X or 4X/day, and concentration (pure or diluted. Exposure time to the acidic content of the chewing gum was five minutes under agitation, during five days. Results: All groups showed a significant decrease in surface microhardness (P < 0.001. There was neither any significant difference in the frequency of exposure to the acidic content nor to the types of dental substrates. There was a statistically significant difference between D1 (pure, 2X/day and D2 (diluted, 2X/day (P = 0.002, D3 (pure, 4X/day and D4 (diluted, 4X/day (P = 0.009 regarding the concentration, then the diluted acid content was associated with a greater decrease in microhardness. Conclusion: It is concluded that the acidic filling of a chewing gum reduced the microhardness of primary and permanent enamel.

  1. Effects of a non-rinse conditioner on the enamel of primary teeth

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    Fava Marcelo

    2003-01-01

    Full Text Available The aim of this in vitro study was to evaluate by scanning electron microscopy the morphological aspects of the enamel of primary teeth after etching with 36% phosphoric acid or a non-rinse conditioner. Ten naturally exfoliated anterior primary teeth were selected. The samples were subjected to prophylaxis with pumice paste and water using a low-speed hand piece. Etching was done on the buccal surface. Specimens were divided into 2 groups: G1 (n=10: etching with 36% phosphoric acid gel - Conditioner 36 (Dentsply for 20 s, followed by water rinse for 15 s; G2 (n=10: etching with NRC - Non Rinse Conditioner (Dentsply for 20 s, followed by air drying for 15 s. The samples were dehydrated, mounted on metal stubs, coated with gold and observed with Jeol JSM-6100 scanning electron microscope. Electron-micrographic analysis showed that both etching agents were effective for etching the enamel of primary teeth causing the formation of microporosities on the enamel surface, although the etching pattern was more effective with the use of 36% phosphoric acid gel.

  2. Casein phosphopeptide-amorphous calcium phosphate and shear bond strength of adhesives to primary teeth enamel.

    Science.gov (United States)

    Farokh Gisovar, Elham; Hedayati, Nassim; Shadman, Niloofar; Shafiee, Leila

    2015-02-01

    CPP-ACP (Phosphopeptide-Amorphous Calcium Phosphate) has an important role in caries prevention in pediatric patients. This study was done, because of the great use of CPP-ACP and the need for restoration for teeth treated with CPP-ACP as well as the importance of shear bond strength of adhesives in the success of restorations. This study aimed to evaluate the effect of casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) on shear bond strength of dental adhesives to enamel of primary teeth molars. This in vitro study was conducted on 180 extracted primary molars. They were randomly divided into 6 groups and each group was divided into 2 subgroups (treated with CPP-ACP and untreated). In subgroups with CPP-ACP, enamel was treated with CPP-ACP paste 1 h/d for 5 days. Types of adhesives that were evaluated in this study were Tetric N-Bond, AdheSE, AdheSE One F, single Bond 2, SE Bond, and Adper Prompt L-Pop. Shear bond strength was tested with a universal testing machine and mode of failure was evaluated under stereomicroscope. Data were analyzed by T test, 2-way analysis of variance (ANOVA), Tukey and Fisher exact test using SPSS18. P adhesive systems to enamel of primary teeth treated and untreated with CPP-ACP showed no significant difference (P > 0.05). Mode of failure in all groups regardless of CPP-ACP administration was mainly adhesive type. Our results indicated that CPP-ACP did not affect shear bond strength of studied adhesives to primary teeth enamel. To have a successful and durable composite restoration, having a high strength bonding is essential. Considering the wide use of CPP-ACP in preventing tooth decay and the role of adhesive shear bond strength (SBS) in success of composite restoration, we conducted the present study to evaluate the effect of CPP-ACP on the SBS of adhesives to primary teeth enamel.

  3. Analysis of the interface zone between the glass ionomer and enamel and dentin of primary molars

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    Petrović Bojan B.

    2008-01-01

    Full Text Available Restoring carious teeth is one of the major dental treatment needs of young children. Conventional glassionomer materials are frequently used as filling materials in contemporary pediatric dentistry. The objective of this study was to evaluate the restorative and prophylactic efficacy of the newly marketed glass ionomer, Fuji Triage (GC, Tokyo, Japan, through morphological analysis of the interface zone between the material and the enamel and the dentin of primary molars and to determine the extent of the ion exchange at the interface zone. The sample consisted of 5 extracted intact first primary molars in which glassionomer had been used as filling material after standard class I cavity preparation. The material was placed according to the manufacturer's instructions and teeth were placed into dionised water prior to experiment. Six sections of each tooth had been examined using scanning electron microscopic and electron dispersive spectroscopic techniques (SEM/EDS. The parameters for evaluation included: morphological characteristics of the interface zone and the extent of the ion exchange between the material and the tooth structures Results were statistically analyzed using descriptive statistical methods. SEM/EDS analysis revealed the presence of the chemical bonding between the glass ionomer and the enamel and dentin, 5 and 15 μm in width, respectively. Ion exchange has not been detected in the enamel at the EDS sensitivity level. Strontium and fluor penetration has been detected in dentin. The ion exchange and chemical bonding formation justify the usage of the conventional glass ionomer materials for restorative procedures in primary molars.

  4. Biorhythms, deciduous enamel thickness, and primary bone growth: a test of the Havers-Halberg Oscillation hypothesis.

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    Mahoney, Patrick; Miszkiewicz, Justyna J; Pitfield, Rosie; Schlecht, Stephen H; Deter, Chris; Guatelli-Steinberg, Debbie

    2016-06-01

    Across mammalian species, the periodicity with which enamel layers form (Retzius periodicity) in permanent teeth corresponds with average body mass and the pace of life history. According to the Havers-Halberg Oscillation hypothesis (HHO), Retzius periodicity (RP) is a manifestation of a biorhythm that is also expressed in lamellar bone. Potentially, these links provide a basis for investigating aspects of a species' biology from fossilized teeth. Here, we tested intra-specific predictions of this hypothesis on skeletal samples of human juveniles. We measured daily enamel growth increments to calculate RP in deciduous molars (n = 25). Correlations were sought between RP, molar average and relative enamel thickness (AET, RET), and the average amount of primary bone growth (n = 7) in humeri of age-matched juveniles. Results show a previously undescribed relationship between RP and enamel thickness. Reduced major axis regression reveals RP is significantly and positively correlated with AET and RET, and scales isometrically. The direction of the correlation was opposite to HHO predictions as currently understood for human adults. Juveniles with higher RPs and thicker enamel had increased primary bone formation, which suggests a coordinating biorhythm. However, the direction of the correspondence was, again, opposite to predictions. Next, we compared RP from deciduous molars with new data for permanent molars, and with previously published values. The lowermost RP of 4 and 5 days in deciduous enamel extends below the lowermost RP of 6 days in permanent enamel. A lowered range of RP values in deciduous enamel implies that the underlying biorhythm might change with age. Our results develop the intra-specific HHO hypothesis. © 2016 Anatomical Society.

  5. Knotted vs. unknotted proteins: evidence of knot-promoting loops.

    Directory of Open Access Journals (Sweden)

    Raffaello Potestio

    Full Text Available Knotted proteins, because of their ability to fold reversibly in the same topologically entangled conformation, are the object of an increasing number of experimental and theoretical studies. The aim of the present investigation is to assess, on the basis of presently available structural data, the extent to which knotted proteins are isolated instances in sequence or structure space, and to use comparative schemes to understand whether specific protein segments can be associated to the occurrence of a knot in the native state. A significant sequence homology is found among a sizeable group of knotted and unknotted proteins. In this family, knotted members occupy a primary sub-branch of the phylogenetic tree and differ from unknotted ones only by additional loop segments. These "knot-promoting" loops, whose virtual bridging eliminates the knot, are found in various types of knotted proteins. Valuable insight into how knots form, or are encoded, in proteins could be obtained by targeting these regions in future computational studies or excision experiments.

  6. Success Evaluation of Pulpotomy in Primary Molars with Enamel Matrix Derivative: a Pilot Study

    Directory of Open Access Journals (Sweden)

    Fatemeh Mazhari

    2016-06-01

    Full Text Available Aim: To investigate the effect of Emdogain gel (EMD in pulpotomized primary molars and its clinical and radiographic outcomes. Methods and Materials: In this   study, 18 lower second primary molars of nine children were treated by   pulpotomy. The teeth were randomly assigned to the EMD (experimental and Formocresol (control groups in each patient (split mouth. Following removal of the coronal pulp and haemostasis, the pulp stumps were covered with Emdogain gel in the experimental group followed by application of resin-modified glass ionomer cement over the gel. In the control group, Formocresol (FC was placed with a cotton pellet over the pulp stumps. Lastly, the teeth in both groups were restored with stainless steel crowns. Results: Nine children referred with clinical failure before/at two months follow up. The radiographic evaluation revealed furcation involvement and extensive radicular radiolucency in molars treated with Emdogain gel. Conclusion: The present study showed the failure of enamel matrix derivative in pulpotomy of primary molars; therefore, we do not recommend using Emdogain as a pulpotomy agent for treatment of cariously exposed primary teeth

  7. Developmental defects of enamel and dental caries in the primary dentition: A systematic review and meta-analysis.

    Science.gov (United States)

    Costa, Francine S; Silveira, Ethieli R; Pinto, Gabriela S; Nascimento, Gustavo G; Thomson, William Murray; Demarco, Flávio F

    2017-05-01

    This systematic review and meta-analysis evaluated the association between developmental defects of enamel and dental caries in the primary dentition. Electronic searches were performed in PubMed, Web of Knowledge, Scopus and Scielo for the identification of relevant studies. Observational studies that examined the association between developmental defects of enamel and dental caries in the deciduous dentition were included. Additionally, meta-analysis, funnel plots and sensitivity analysis were employed to synthesize the available evidence. Multivariable meta-regression analysis was performed to explore heterogeneity among studies. A total of 318 articles were identified in the electronic searches. Of those, 16 studies were included in the meta-analysis. Pooled estimates revealed that children with developmental defects of enamel had higher odds of having dental caries (OR 3.32; 95%CI 2.41-4.57), with high heterogeneity between studies (I 2 80%). Methodological characteristic of the studies, such as where it was conducted, the examined teeth and the quality of the study explained about 30% of the variability. Concerning type of defect, children with hypoplasia and diffuse opacities had higher odds of having dental caries (OR 4.28; 95%CI 2.24-8.15; OR1.42; 95%CI 1.15-1.76, respectively). This systematic review and meta-analysis demonstrates a clear association between developmental defects of enamel and dental caries in the primary dentition. Copyright © 2017 Elsevier Ltd. All rights reserved.

  8. A Midsummer Knot's Dream

    Science.gov (United States)

    Henrich, A.; MacNaughton, N.; Narayan, S.; Pechenik, O.; Silversmith, R.; Townsend, J.

    2011-01-01

    We introduce playing games on the shadows of knots and demonstrate two novel games, namely, "To Knot or Not to Knot" and "Much Ado about Knotting." We discuss winning strategies for these games on certain families of knot shadows and go on to suggest variations of these games for further study.

  9. Tooth enamel mineralization in ungulates: implications for recovering a primary isotopic time-series

    Science.gov (United States)

    Passey, Benjamin H.; Cerling, Thure E.

    2002-09-01

    Temporal changes in the carbon and oxygen isotopic composition of an animal are an environmental and behavioral input signal that is recorded into the enamel of developing teeth. In this paper, we evaluate changes in phosphorus content and density along the axial lengths of three developing ungulate teeth to illustrate the protracted nature of mineral accumulation in a volume of developing enamel. The least mature enamel in these teeth contains by volume about 25% of the mineral mass of mature enamel, and the remaining 75% of the mineral accumulates during maturation. Using data from one of these teeth (a Hippopotamus amphibius canine), we develop a model for teeth growing at constant rate that describes how an input signal is recorded into tooth enamel. The model accounts for both the temporal and spatial patterns of amelogenesis (enamel formation) and the sampling geometry. The model shows that input signal attenuation occurs as a result of time-averaging during amelogenesis when the maturation interval is long compared to the duration of features in the input signal. Sampling does not induce significant attenuation, provided that the sampling interval is several times shorter than the maturation interval. We present a detailed δ 13C and δ 18O record for the H. amphibius canine and suggest possible input isotope signals that may have given rise to the measured isotope signal.

  10. Enamel defect of primary dentition in SGA children in relation to onset time of intrauterine growth disturbance

    Directory of Open Access Journals (Sweden)

    Willyanti Soewondo Sjarif

    2013-06-01

    Full Text Available Background: Prenatal disturbances disturb the development of organs resulting in small for gestational age (SGA babies and also causes enamel defects in primary teeth. There are disturbances occur in the beginning of pregnancy causing symmetrical SGA, and asymmetrical type of SGA, where the disturbances occur late in pregnancy. Purpose: This research was to determined differences in severity of enamel defect of primary dentition in small for gestational age children based on the time of intrauterine growth restriction. Methods: This was a clinical epidemiological cohort study. The Ponderal index was used to determine SGA type. The subjects were 129 SGA children aged 9-42 months, 82 with asymmetrical SGA and 47 with symmetrical SGA. Two hundred normal birth weight children were the control group. Intra-oral examinations to determine enamel defect used the FDI modification of the Developmental Defect of Enamel score at 3 months intervals. Statistical t-tests were used to test the difference in severity of enamel defect, and chisquare to find out the difference of Relative Risk Ratio (RRR. Results: The results showed that the enamel defect scores of symmetrical SGA were significantly higher than those with asymmetrical SGA. RRR for severe defect was also significantly higher in symmetrical type for anterior and canines. Conclusion: The study suggested that the severity of enamel defect for infants with symmetrical SGA was higher than those with asymmetrical SGA, indicating that the severity of the defect occurs in the beginning of pregnancy is more severe than in the late pregnancy.Latar belakang: Adanya gangguan prenatal mengganggu perkembangan organ, mengakibatkan terjadinya bayi lahir dengan kecil masa kehamilan (KMK dan defek email pada gigi sulung. Terdapat 2 tipe KMK yaitu tipe simetri; gangguan terjadi pada awal kehamilan; dimana lingkar kepala, berat dan panjang lahir lebih rendah dari normal. Tipe asimetri dimana gangguan terjadi saat

  11. Short communication: pre- and co-curing effect of adhesives on shear bond strengths of composite resins to primary enamel and dentine: an in vitro study.

    Science.gov (United States)

    Viswanathan, R; Shashibhushan, K K; Subba Reddy, V V

    2011-12-01

    To evaluate and compare shear bond strengths of composite resins to primary enamel and dentine when the adhesives are pre-cured (light cured before the application of the resin) or co-cured (adhesive and the resin light cured together). Buccal surfaces of 80 caries-free primary molars were wet ground to create bonding surfaces on enamel and dentine and specimens mounted on acrylic blocks. Two bonding agents (Prime and Bond NT® and Xeno III®) were applied to either enamel or dentine as per manufacturer's instructions. In 40 specimens, the bonding agent was light cured immediately after the application (pre-cured). The other 40 specimens were not light cured until the composite resin application (co-cured). Resin composite cylinders were made incrementally using acrylic moulds over the adhesives and light cured. Specimens were stored in deionised water for 24 hours at room temperature. Shear bond strength was measured using an Instron universal testing machine (in MPa) and was analysed with Student's unpaired t test. Light curing the adhesive separately produced significantly higher bond strengths to primary dentine than co-curing (padhesive separately did not produce significantly different bond strengths to primary enamel (p>0.05). Curing sequence had no significant effect on shear bond strength of adhesives on the primary enamel. Pre-curing adhesives before curing composite resins produced greater shear bond strength to primary dentine.

  12. Prevalence of dental anomalies and enamel hypoplasia in primary dentition among preschool children of West Godavari District, Andhra Pradesh -A cross - sectional study

    Directory of Open Access Journals (Sweden)

    Suzan Sahana

    2013-01-01

    Full Text Available Background: It is axiomatic that Pediatric dental anomalies and enamel hypoplasia (E.H are routinely encountered in primary dentition and early detection and prudent management of the condition facilitates normal occlusal development. Objectives: To determine the prevalence of various dental anomalies and enamel hypoplasia in preschool children between two to six years of age. Materials & Method: A total of 1898 children, between two to six years were randomly selected and screened for dental anomalies and enamel hypoplasia The chi square test was used to analyze the data statistically. Results: The overall prevalence rate of dental anomalies and enamel hypoplasia in this study was 0.63% and 8.95% respectively. Double teeth were the most frequently reported dental anomaly while supernumerary teeth were least reported. None of them reported with hypodontia.

  13. Handbook of knot theory

    CERN Document Server

    Menasco, William

    2005-01-01

    This book is a survey of current topics in the mathematical theory of knots. For a mathematician, a knot is a closed loop in 3-dimensional space: imagine knotting an extension cord and then closing it up by inserting its plug into its outlet. Knot theory is of central importance in pure and applied mathematics, as it stands at a crossroads of topology, combinatorics, algebra, mathematical physics and biochemistry.* Survey of mathematical knot theory* Articles by leading world authorities* Clear exposition, not over-technical* Accessible to readers with undergraduate background in mathematics

  14. Knots with proprety R+

    OpenAIRE

    Clark, Bradd Evans

    1983-01-01

    If we consider the set of manifolds that can be obtained by surgery on a fixed knot K, then we have an associated set of numbers corresponding to the Heegaard genus of these manifolds. It is known that there is an upper bound to this set of numbers. A knot K is said to have Property R+ if longitudinal surgery yields a manifold of highest possible Heegaard genus among those obtainable by surgery on K. In this paper we show that torus knots, 2-bridge knots, and knots which are the connected ...

  15. Knots and links

    CERN Document Server

    Rolfsen, Dale

    2003-01-01

    Rolfsen's beautiful book on knots and links can be read by anyone, from beginner to expert, who wants to learn about knot theory. Beginners with a basic background find an inviting introduction to the elements of topology, emphasizing the tools needed for understanding knots, the fundamental group and van Kampen's theorem, for example, which are then applied to concrete problems, such as computing knot groups. For experts, Rolfsen explains advanced topics, such as the connections between knot theory and surgery and how they are useful to understanding three-manifolds. Besides providing a guide

  16. Evaluation of primary tooth enamel surface morphology and microhardness after Nd:YAG laser irradiation and APF gel treatment--an in vitro study.

    Science.gov (United States)

    Banda, Naveen Reddy; Vanaja Reddy, G; Shashikiran, N D

    2011-01-01

    Laser irradiation and fluoride has been used as a preventive tool to combat dental caries in permanent teeth, but little has been done for primary teeth which are more prone to caries. The purpose of this study was to evaluate microhardness alterations in the primary tooth enamel after Nd-YAG laser irradiation alone and combined with topical fluoride treatment either before or after Nd-YAG laser irradiation. Ten primary molars were sectioned and assigned randomly to: control group, Nd-YAG laser irradiation, Nd-YAG lasing before APF and APF followed by Nd-YAG lasing. The groups were evaluated for microhardness. Surface morphological changes were observed using SEM. Statistical comparisons were performed. The control group's SEM showed a relatively smooth enamel surface and lasing group had fine cracks and porosities. In the lasing + fluoride group a homogenous confluent surface was seen. In the fluoride + lasing group an irregular contour with marked crack propagation was noted. There was a significant increase in the microhardness of the treatment groups. Nd-YAG laser irradiation and combined APF treatment of the primary tooth enamel gave morphologically hardened enamel surface which can be a protective barrier against a cariogenic attack.

  17. p38α MAPK Is Required for Tooth Morphogenesis and Enamel Secretion*

    Science.gov (United States)

    Greenblatt, Matthew B.; Kim, Jung-Min; Oh, Hwanhee; Park, Kwang Hwan; Choo, Min-Kyung; Sano, Yasuyo; Tye, Coralee E.; Skobe, Ziedonis; Davis, Roger J.; Park, Jin Mo; Bei, Marianna; Glimcher, Laurie H.; Shim, Jae-Hyuck

    2015-01-01

    An improved understanding of the molecular pathways that drive tooth morphogenesis and enamel secretion is needed to generate teeth from organ cultures for therapeutic implantation or to determine the pathogenesis of primary disorders of dentition (Abdollah, S., Macias-Silva, M., Tsukazaki, T., Hayashi, H., Attisano, L., and Wrana, J. L. (1997) J. Biol. Chem. 272, 27678–27685). Here we present a novel ectodermal dysplasia phenotype associated with conditional deletion of p38α MAPK in ectodermal appendages using K14-cre mice (p38αK14 mice). These mice display impaired patterning of dental cusps and a profound defect in the production and biomechanical strength of dental enamel because of defects in ameloblast differentiation and activity. In the absence of p38α, expression of amelogenin and β4-integrin in ameloblasts and p21 in the enamel knot was significantly reduced. Mice lacking the MAP2K MKK6, but not mice lacking MAP2K MKK3, also show the enamel defects, implying that MKK6 functions as an upstream kinase of p38α in ectodermal appendages. Lastly, stimulation with BMP2/7 in both explant culture and an ameloblast cell line confirm that p38α functions downstream of BMPs in this context. Thus, BMP-induced activation of the p38α MAPK pathway is critical for the morphogenesis of tooth cusps and the secretion of dental enamel. PMID:25406311

  18. Effect of conventional and sugar free pediatric syrup formulations on primary tooth enamel hardness: An in vitro study

    Directory of Open Access Journals (Sweden)

    Gaurao Vasant Mali

    2015-01-01

    Full Text Available Objectives: To assess and compare the effect of conventional and sugar free pediatric syrup formulations on primary tooth enamel hardness over a period of 14 days. Materials and Methods: An in vitro study was done on 40 noncarious deciduous teeth. 10 teeth in each group were dipped in 4 pediatric medicinal syrups (1 sugarfree and 3 conventional for 1 min thrice daily for 14 days and the enamel surface micro hardness was checked at baseline, 7 th day and 14 th day by Vickers hardness testing machine. The pH, titratable acidity and buffering capacity of the syrups were assessed. Results: The pH of syrups were above critical pH for demineralization of the tooth but tiratable acidity and buffering capacity differed. ANOVA test indicated that the reduction in mean micro hardness was maximum in Group D (Conventional Analgesic syrup and least in Group A (Sugarfree cough syrup on 7 th and 14 th day. On intergroup comparison there was no difference (P > 0.05 in micro hardness between Group B (Conventional Cough syrup and Group C (Conventional Antibiotic. However, highly significant (P < 0.01 difference between the either pair of Group B with Group D, and Group C with Group D on 14 th day. The percentage reduction in micro hardness on 14 th day was maximum for Group D (24.4 ± 2.2 and minimum for Group A (14.0 ± 1.3 which was statistically significant (P < 0.01. Conclusion: Sugar free pediatric medicines can be effective in reducing dental erosion and efforts should be made to incorporate sugar substitutes in formulation of pediatric medicines.

  19. Knots in Art

    Directory of Open Access Journals (Sweden)

    Radmila Sazdanović

    2012-06-01

    Full Text Available We analyze applications of knots and links in the Ancient art, beginning from Babylonian, Egyptian, Greek, Byzantine and Celtic art. Construction methods used in art are analyzed on the examples of Celtic art and ethnical art of Tchokwe people from Angola or Tamil art, where knots are constructed as mirror-curves. We propose different methods for generating knots and links based on geometric polyhedra, suitable for applications in architecture and sculpture.

  20. Knots in Art

    OpenAIRE

    Jablan, Slavik; Radović, Ljiljana; Sazdanović, Radmila; Zeković, Ana

    2012-01-01

    We analyze applications of knots and links in the Ancient art, beginning from Babylonian, Egyptian, Greek, Byzantine and Celtic art. Construction methods used in art are analyzed on the examples of Celtic art and ethnical art of Tchokwe people from Angola or Tamil art, where knots are constructed as mirror-curves. We propose different methods for generating knots and links based on geometric polyhedra, suitable for applications in architecture and sculpture.

  1. History and science of knots

    CERN Document Server

    Turner, J C

    1996-01-01

    This book brings together twenty essays on diverse topics in the history and science of knots. It is divided into five parts, which deal respectively with knots in prehistory and antiquity, non-European traditions, working knots, the developing science of knots, and decorative and other aspects of knots.Its authors include archaeologists who write on knots found in digs of ancient sites (one describes the knots used by the recently discovered Ice Man); practical knotters who have studied the history and uses of knots at sea, for fishing and for various life support activities; a historian of l

  2. A Stevedore's protein knot.

    Directory of Open Access Journals (Sweden)

    Daniel Bölinger

    2010-04-01

    Full Text Available Protein knots, mostly regarded as intriguing oddities, are gradually being recognized as significant structural motifs. Seven distinctly knotted folds have already been identified. It is by and large unclear how these exceptional structures actually fold, and only recently, experiments and simulations have begun to shed some light on this issue. In checking the new protein structures submitted to the Protein Data Bank, we encountered the most complex and the smallest knots to date: A recently uncovered alpha-haloacid dehalogenase structure contains a knot with six crossings, a so-called Stevedore knot, in a projection onto a plane. The smallest protein knot is present in an as yet unclassified protein fragment that consists of only 92 amino acids. The topological complexity of the Stevedore knot presents a puzzle as to how it could possibly fold. To unravel this enigma, we performed folding simulations with a structure-based coarse-grained model and uncovered a possible mechanism by which the knot forms in a single loop flip.

  3. Knots in polymers

    Indian Academy of Sciences (India)

    Abstract. Knots and topological entanglements play an important role in the statistical mechanics of polymers. While topological entanglement is a global property, it is possible to study the size of a knotted region both numerically and analytically. It can be shown that long-range repulsive interactions, as well as entropy ...

  4. Knot topology in QCD

    International Nuclear Information System (INIS)

    Zou, L.P.; Zhang, P.M.; Pak, D.G.

    2013-01-01

    We consider topological structure of classical vacuum solutions in quantum chromodynamics. Topologically non-equivalent vacuum configurations are classified by non-trivial second and third homotopy groups for coset of the color group SU(N) (N=2,3) under the action of maximal Abelian stability group. Starting with explicit vacuum knot configurations we study possible exact classical solutions. Exact analytic non-static knot solution in a simple CP 1 model in Euclidean space–time has been obtained. We construct an ansatz based on knot and monopole topological vacuum structure for searching new solutions in SU(2) and SU(3) QCD. We show that singular knot-like solutions in QCD in Minkowski space–time can be naturally obtained from knot solitons in integrable CP 1 models. A family of Skyrme type low energy effective theories of QCD admitting exact analytic solutions with non-vanishing Hopf charge is proposed

  5. 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.

  6. Colouring and knot polynomials

    International Nuclear Information System (INIS)

    Welsh, D.J.A.

    1991-01-01

    These lectures will attempt to explain a connection between the recent advances in knot theory using the Jones and related knot polynomials with classical problems in combinatorics and statistical mechanics. The difficulty of some of these problems will be analysed in the context of their computational complexity. In particular we shall discuss colourings and groups valued flows in graphs, knots and the Jones and Kauffman polynomials, the Ising, Potts and percolation problems of statistical physics, computational complexity of the above problems. (author). 20 refs, 9 figs

  7. The Mathematics of Knots

    CERN Document Server

    Banagl, Markus

    2011-01-01

    The present volume grew out of the Heidelberg Knot Theory Semester, organized by the editors in winter 2008/09 at Heidelberg University. The contributed papers bring the reader up to date on the currently most actively pursued areas of mathematical knot theory and its applications in mathematical physics and cell biology. Both original research and survey articles are presented; numerous illustrations support the text. The book will be of great interest to researchers in topology, geometry, and mathematical physics, graduate students specializing in knot theory, and cell biologists interested

  8. The mystery of knots

    CERN Document Server

    Aneziris, Charilaos N

    1999-01-01

    One of the most significant unsolved problems in mathematics is the complete classification of knots. The main purpose of this book is to introduce the reader to the use of computer programming to obtain the table of knots. The author presents this problem as clearly and methodically as possible, starting from the very basics. Mathematical ideas and concepts are extensively discussed, and no advanced background is required.

  9. Knotting in stretched polygons

    International Nuclear Information System (INIS)

    Rensburg, E J Janse van; Orlandini, E; Tesi, M C; Whittington, S G

    2008-01-01

    The knotting in a lattice polygon model of ring polymers is examined when a stretching force is applied to the polygon. By examining the incidence of cut-planes in the polygon, we prove a pattern theorem in the stretching regime for large applied forces. This theorem can be used to examine the incidence of entanglements such as knotting and writhing. In particular, we prove that for arbitrarily large positive, but finite, values of the stretching force, the probability that a stretched polygon is knotted approaches 1 as the length of the polygon increases. In the case of writhing, we prove that for stretched polygons of length n, and for every function f(n)=o(√n), the probability that the absolute value of the mean writhe is less than f(n) approaches 0 as n → ∞, for sufficiently large values of the applied stretching force

  10. Knots and Links

    Indian Academy of Sciences (India)

    in a fashion similar to sound waves, whose medium is air. Ether was believed ..... [3] Colin C Adams, The Knot Book, W H Freeman and Company, New. York. ... [5] Kelly S Chichak, Stuart j CantriU, Antony R Pease, Sheng-Hsien. Chiu, Gareth ...

  11. Knot theory in modern chemistry.

    Science.gov (United States)

    Horner, Kate E; Miller, Mark A; Steed, Jonathan W; Sutcliffe, Paul M

    2016-11-21

    Knot theory is a branch of pure mathematics, but it is increasingly being applied in a variety of sciences. Knots appear in chemistry, not only in synthetic molecular design, but also in an array of materials and media, including some not traditionally associated with knots. Mathematics and chemistry can now be used synergistically to identify, characterise and create knots, as well as to understand and predict their physical properties. This tutorial review provides a brief introduction to the mathematics of knots and related topological concepts in the context of the chemical sciences. We then survey the broad range of applications of the theory to contemporary research in the field.

  12. Proteins analysed as virtual knots

    Science.gov (United States)

    Alexander, Keith; Taylor, Alexander J.; Dennis, Mark R.

    2017-02-01

    Long, flexible physical filaments are naturally tangled and knotted, from macroscopic string down to long-chain molecules. The existence of knotting in a filament naturally affects its configuration and properties, and may be very stable or disappear rapidly under manipulation and interaction. Knotting has been previously identified in protein backbone chains, for which these mechanical constraints are of fundamental importance to their molecular functionality, despite their being open curves in which the knots are not mathematically well defined; knotting can only be identified by closing the termini of the chain somehow. We introduce a new method for resolving knotting in open curves using virtual knots, which are a wider class of topological objects that do not require a classical closure and so naturally capture the topological ambiguity inherent in open curves. We describe the results of analysing proteins in the Protein Data Bank by this new scheme, recovering and extending previous knotting results, and identifying topological interest in some new cases. The statistics of virtual knots in protein chains are compared with those of open random walks and Hamiltonian subchains on cubic lattices, identifying a regime of open curves in which the virtual knotting description is likely to be important.

  13. Braiding knots with topological strings

    International Nuclear Information System (INIS)

    Gu, Jie

    2015-08-01

    For an arbitrary knot in a three-sphere, the Ooguri-Vafa conjecture associates to it a unique stack of branes in type A topological string on the resolved conifold, and relates the colored HOMFLY invariants of the knot to the free energies on the branes. For torus knots, we use a modified version of the topological recursion developed by Eynard and Orantin to compute the free energies on the branes from the Aganagic-Vafa spectral curves of the branes, and find they are consistent with the known colored HOMFLY knot invariants a la the Ooguri-Vafa conjecture. In addition our modified topological recursion can reproduce the correct closed string free energies, which encode the information of the background geometry. We conjecture the modified topological recursion is applicable for branes associated to hyperbolic knots as well, encouraged by the observation that the modified topological recursion yields the correct planar closed string free energy from the Aganagic-Vafa spectral curves of hyperbolic knots. This has implications for the knot theory concerning distinguishing mutant knots with colored HOMFLY invariants. Furthermore, for hyperbolic knots, we present methods to compute colored HOMFLY invariants in nonsymmetric representations of U(N). The key step in this computation is computing quantum 6j-symbols in the quantum group U q (sl N ).

  14. Dental enamel cells express functional SOCE channels.

    Science.gov (United States)

    Nurbaeva, Meerim K; Eckstein, Miriam; Concepcion, Axel R; Smith, Charles E; Srikanth, Sonal; Paine, Michael L; Gwack, Yousang; Hubbard, Michael J; Feske, Stefan; Lacruz, Rodrigo S

    2015-10-30

    Dental enamel formation requires large quantities of Ca(2+) yet the mechanisms mediating Ca(2+) dynamics in enamel cells are unclear. Store-operated Ca(2+) entry (SOCE) channels are important Ca(2+) influx mechanisms in many cells. SOCE involves release of Ca(2+) from intracellular pools followed by Ca(2+) entry. The best-characterized SOCE channels are the Ca(2+) release-activated Ca(2+) (CRAC) channels. As patients with mutations in the CRAC channel genes STIM1 and ORAI1 show abnormal enamel mineralization, we hypothesized that CRAC channels might be an important Ca(2+) uptake mechanism in enamel cells. Investigating primary murine enamel cells, we found that key components of CRAC channels (ORAI1, ORAI2, ORAI3, STIM1, STIM2) were expressed and most abundant during the maturation stage of enamel development. Furthermore, inositol 1,4,5-trisphosphate receptor (IP3R) but not ryanodine receptor (RyR) expression was high in enamel cells suggesting that IP3Rs are the main ER Ca(2+) release mechanism. Passive depletion of ER Ca(2+) stores with thapsigargin resulted in a significant raise in [Ca(2+)]i consistent with SOCE. In cells pre-treated with the CRAC channel blocker Synta-66 Ca(2+) entry was significantly inhibited. These data demonstrate that enamel cells have SOCE mediated by CRAC channels and implicate them as a mechanism for Ca(2+) uptake in enamel formation.

  15. Computational Elastic Knots

    KAUST Repository

    Zhao, Xin

    2013-05-01

    Elastic rods have been studied intensively since the 18th century. Even now the theory of elastic rods is still developing and enjoying popularity in computer graphics and physical-based simulation. Elastic rods also draw attention from architects. Architectural structures, NODUS, were constructed by elastic rods as a new method of form-finding. We study discrete models of elastic rods and NODUS structures. We also develop computational tools to find the equilibria of elastic rods and the shape of NODUS. Applications of elastic rods in forming torus knot and closing Bishop frame are included in this thesis.

  16. Energy of knots and conformal geometry

    CERN Document Server

    O'Hara, Jun

    2003-01-01

    Energy of knots is a theory that was introduced to create a "canonical configuration" of a knot - a beautiful knot which represents its knot type. This book introduces several kinds of energies, and studies the problem of whether or not there is a "canonical configuration" of a knot in each knot type. It also considers this problems in the context of conformal geometry. The energies presented in the book are defined geometrically. They measure the complexity of embeddings and have applications to physical knotting and unknotting through numerical experiments. Contents: In Search of the "Optima

  17. Torus knots and mirror symmetry

    CERN Document Server

    Brini, Andrea; Marino, Marcos

    2012-01-01

    We propose a spectral curve describing torus knots and links in the B-model. In particular, the application of the topological recursion to this curve generates all their colored HOMFLY invariants. The curve is obtained by exploiting the full Sl(2, Z) symmetry of the spectral curve of the resolved conifold, and should be regarded as the mirror of the topological D-brane associated to torus knots in the large N Gopakumar-Vafa duality. Moreover, we derive the curve as the large N limit of the matrix model computing torus knot invariants.

  18. Intricate knots in proteins: Function and evolution.

    Directory of Open Access Journals (Sweden)

    Peter Virnau

    2006-09-01

    Full Text Available Our investigation of knotted structures in the Protein Data Bank reveals the most complicated knot discovered to date. We suggest that the occurrence of this knot in a human ubiquitin hydrolase might be related to the role of the enzyme in protein degradation. While knots are usually preserved among homologues, we also identify an exception in a transcarbamylase. This allows us to exemplify the function of knots in proteins and to suggest how they may have been created.

  19. Handbook of knotting and splicing

    CERN Document Server

    Hasluck, Paul N

    2005-01-01

    Clearly written and amply illustrated with 208 figures, this classic guide ranges from simple and useful knots to complex varieties. Additional topics include rope splicing, working cordage, hammock making, more.

  20. Recognition algorithms in knot theory

    International Nuclear Information System (INIS)

    Dynnikov, I A

    2003-01-01

    In this paper the problem of constructing algorithms for comparing knots and links is discussed. A survey of existing approaches and basic results in this area is given. In particular, diverse combinatorial methods for representing links are discussed, the Haken algorithm for recognizing a trivial knot (the unknot) and a scheme for constructing a general algorithm (using Haken's ideas) for comparing links are presented, an approach based on representing links by closed braids is described, the known algorithms for solving the word problem and the conjugacy problem for braid groups are described, and the complexity of the algorithms under consideration is discussed. A new method of combinatorial description of knots is given together with a new algorithm (based on this description) for recognizing the unknot by using a procedure for monotone simplification. In the conclusion of the paper several problems are formulated whose solution could help to advance towards the 'algorithmization' of knot theory

  1. Weaving Knotted Vector Fields with Tunable Helicity.

    Science.gov (United States)

    Kedia, Hridesh; Foster, David; Dennis, Mark R; Irvine, William T M

    2016-12-30

    We present a general construction of divergence-free knotted vector fields from complex scalar fields, whose closed field lines encode many kinds of knots and links, including torus knots, their cables, the figure-8 knot, and its generalizations. As finite-energy physical fields, they represent initial states for fields such as the magnetic field in a plasma, or the vorticity field in a fluid. We give a systematic procedure for calculating the vector potential, starting from complex scalar functions with knotted zero filaments, thus enabling an explicit computation of the helicity of these knotted fields. The construction can be used to generate isolated knotted flux tubes, filled by knots encoded in the lines of the vector field. Lastly, we give examples of manifestly knotted vector fields with vanishing helicity. Our results provide building blocks for analytical models and simulations alike.

  2. Biomechanical evaluation of the Nice knot

    OpenAIRE

    Hill, Shannon W.; Chapman, Christopher R.; Adeeb, Samer; Duke, Kajsa; Beaupre, Lauren; Bouliane, Martin J.

    2016-01-01

    Background: The Nice knot is a bulky double-stranded knot. Biomechanical data supporting its use as well as the number of half hitches required to ensure knot security is lacking. Materials and Methods: Nice knots with, one, two, or three half-hitches were compared with the surgeon′s and Tennessee slider knots with three half hitches. Each knot was tied 10 times around a fixed diameter using four different sutures: FiberWire (Arthrex, Naples, FL), Ultrabraid (Smith and Nephew, Andover, MA...

  3. Amelogenin and Enamel Biomimetics

    Science.gov (United States)

    Ruan, Qichao; Moradian-Oldak, Janet

    2015-01-01

    Mature tooth enamel is acellular and does not regenerate itself. Developing technologies that rebuild tooth enamel and preserve tooth structure is therefore of great interest. Considering the importance of amelogenin protein in dental enamel formation, its ability to control apatite mineralization in vitro, and its potential to be applied in fabrication of future bio-inspired dental material this review focuses on two major subjects: amelogenin and enamel biomimetics. We review the most recent findings on amelogenin secondary and tertiary structural properties with a focus on its interactions with different targets including other enamel proteins, apatite mineral, and phospholipids. Following a brief overview of enamel hierarchical structure and its mechanical properties we will present the state-of-the-art strategies in the biomimetic reconstruction of human enamel. PMID:26251723

  4. Knot invariants derived from quandles and racks

    OpenAIRE

    Kamada, Seiichi

    2002-01-01

    The homology and cohomology of quandles and racks are used in knot theory: given a finite quandle and a cocycle, we can construct a knot invariant. This is a quick introductory survey to the invariants of knots derived from quandles and racks.

  5. How to Twist a Knot

    DEFF Research Database (Denmark)

    Randrup, Thomas; Røgen, Peter

    1997-01-01

    is an invariant of ambient isotopy measuring the topological twist of the closed strip. We classify closed strips in euclidean 3-space by their knots and their twisting number. We prove that this classification exactly divides closed strips into isotopy classes. Using this classification we point out how some...

  6. Mutual attraction of magnetic knots

    International Nuclear Information System (INIS)

    Parker, E.N.

    1978-01-01

    It is observed that the magnetic knots associated with active regions on the Sun have an attraction for each other during the formative period of the active regions, when new magnetic flux is coming to the surface. The attraction disappears when new flux ceases to rise through the surface. Then the magnetic spots and knots tend to come apart, leading to disintegration of the sunspots previously formed. The dissolution of the fields is to be expected, as a consequence of the magnetic repulsion of knots of like polarity and as a consequence of the hydromagnetic exchange instability.The purpose of this paper is to show that the mutual attraction of knots during the formative stages of a sunspot region may be understood as the mutual hydrodynamic attraction of the rising flux tubes. Two rising tubes attract each other, as a consequence of the wake of the leading tube when one is moving behind the other, and as a consequence of the Bernoulli effect when rising side by side

  7. Analysis of enamel development using murine model systems: approaches and limitations.

    Directory of Open Access Journals (Sweden)

    Megan K Pugach

    2014-09-01

    Full Text Available A primary goal of enamel research is to understand and potentially treat or prevent enamel defects related to amelogenesis imperfecta (AI. Rodents are ideal models to assist our understanding of how enamel is formed because they are easily genetically modified, and their continuously erupting incisors display all stages of enamel development and mineralization. While numerous methods have been developed to generate and analyze genetically modified rodent enamel, it is crucial to understand the limitations and challenges associated with these methods in order to draw appropriate conclusions that can be applied translationally, to AI patient care. We have highlighted methods involved in generating and analyzing rodent enamel and potential approaches to overcoming limitations of these methods: 1 generating transgenic, knockout and knockin mouse models, and 2 analyzing rodent enamel mineral density and functional properties (structure, mechanics of mature enamel. There is a need for a standardized workflow to analyze enamel phenotypes in rodent models so that investigators can compare data from different studies. These methods include analyses of gene and protein expression, developing enamel histology, enamel pigment, degree of mineralization, enamel structure and mechanical properties. Standardization of these methods with regard to stage of enamel development and sample preparation is crucial, and ideally investigators can use correlative and complementary techniques with the understanding that developing mouse enamel is dynamic and complex.

  8. Endocytosis and Enamel Formation

    Directory of Open Access Journals (Sweden)

    Cong-Dat Pham

    2017-07-01

    Full Text Available Enamel formation requires consecutive stages of development to achieve its characteristic extreme mineral hardness. Mineralization depends on the initial presence then removal of degraded enamel proteins from the matrix via endocytosis. The ameloblast membrane resides at the interface between matrix and cell. Enamel formation is controlled by ameloblasts that produce enamel in stages to build the enamel layer (secretory stage and to reach final mineralization (maturation stage. Each stage has specific functional requirements for the ameloblasts. Ameloblasts adopt different cell morphologies during each stage. Protein trafficking including the secretion and endocytosis of enamel proteins is a fundamental task in ameloblasts. The sites of internalization of enamel proteins on the ameloblast membrane are specific for every stage. In this review, an overview of endocytosis and trafficking of vesicles in ameloblasts is presented. The pathways for internalization and routing of vesicles are described. Endocytosis is proposed as a mechanism to remove debris of degraded enamel protein and to obtain feedback from the matrix on the status of the maturing enamel.

  9. Enamel tissue engineering using subcultured enamel organ epithelial cells in combination with dental pulp cells.

    Science.gov (United States)

    Honda, Masaki J; Shinmura, Yuka; Shinohara, Yoshinori

    2009-01-01

    We describe a strategy for the in vitro engineering of enamel tissue using a novel technique for culturing enamel organ epithelial (EOE) cells isolated from the enamel organ using 3T3-J2 cells as a feeder layer. These subcultured EOE cells retain the capacity to produce enamel structures over a period of extended culture. In brief, enamel organs from 6-month-old porcine third molars were dissociated into single cells and subcultured on 3T3-J2 feeder cell layers. These subcultured EOE cells were then seeded onto a collagen sponge in combination with primary dental pulp cells isolated at an early stage of crown formation, and these constructs were transplanted into athymic rats. After 4 weeks, complex enamel-dentin structures were detected in the implants. These results show that our culture technique maintained ameloblast lineage cells that were able to produce enamel in vivo. This novel subculture technique provides an important tool for tooth tissue engineering. Copyright 2008 S. Karger AG, Basel.

  10. DNA Knots: Theory and Experiments

    Science.gov (United States)

    Sumners, D. W.

    Cellular DNA is a long, thread-like molecule with remarkably complex topology. Enzymes that manipulate the geometry and topology of cellular DNA perform many vital cellular processes (including segregation of daughter chromosomes, gene regulation, DNA repair, and generation of antibody diversity). Some enzymes pass DNA through itself via enzyme-bridged transient breaks in the DNA; other enzymes break the DNA apart and reconnect it to different ends. In the topological approach to enzymology, circular DNA is incubated with an enzyme, producing an enzyme signature in the form of DNA knots and links. By observing the changes in DNA geometry (supercoiling) and topology (knotting and linking) due to enzyme action, the enzyme binding and mechanism can often be characterized. This paper will discuss some personal research history, and the tangle model for the analysis of site-specific recombination experiments on circular DNA.

  11. Accentuated lines in the enamel of primary incisors from skeletal remains: A contribution to the explanation of early childhood mortality in a medieval population from Poland.

    Science.gov (United States)

    Żądzińska, Elżbieta; Lorkiewicz, Wiesław; Kurek, Marta; Borowska-Strugińska, Beata

    2015-07-01

    Physiological disruptions resulting from an impoverished environment during the first years of life are of key importance for the health and biological status of individuals and populations. Studies of growth processes in archaeological populations point to the fact that the main causes of childhood mortality in the past are to be sought among extrinsic factors. Based on this assumption, one would expect random mortality of children, with the deceased individuals representing the entire subadult population. The purpose of this study is to explore whether differences in early childhood survival are reflected in differences in deciduous tooth enamel, which can provide an insight into the development of an individual during prenatal and perinatal ontogeny. Deciduous incisors were taken from 83 individuals aged 2.0-6.5 years from a medieval inhumation cemetery dated AD 1300-1600. Prenatal and postnatal enamel formation time, neonatal line width, and the number of accentuated lines were measured using an optical microscope. The significantly wider neonatal line and the higher frequency of accentuated lines in the enamel of the incisors of children who died at the age of 2-3 years suggest the occurrence of stronger or more frequent stress events in this group. These results indicate that in skeletal populations mortality was not exclusively determined by random external factors. Individuals predisposed by an unfavorable course of prenatal and perinatal growth were more likely to die in early childhood. © 2015 Wiley Periodicals, Inc.

  12. Characteristic length of the knotting probability revisited

    International Nuclear Information System (INIS)

    Uehara, Erica; Deguchi, Tetsuo

    2015-01-01

    We present a self-avoiding polygon (SAP) model for circular DNA in which the radius of impermeable cylindrical segments corresponds to the screening length of double-stranded DNA surrounded by counter ions. For the model we evaluate the probability for a generated SAP with N segments having a given knot K through simulation. We call it the knotting probability of a knot K with N segments for the SAP model. We show that when N is large the most significant factor in the knotting probability is given by the exponentially decaying part exp(−N/N K ), where the estimates of parameter N K are consistent with the same value for all the different knots we investigated. We thus call it the characteristic length of the knotting probability. We give formulae expressing the characteristic length as a function of the cylindrical radius r ex , i.e. the screening length of double-stranded DNA. (paper)

  13. The mathematics and physics of knots

    Energy Technology Data Exchange (ETDEWEB)

    Kauffman, Louis H [Department of Mathematics, Statistics and Computer Science, University of Illinois at Chicago, 851 South Morgan Street, Chicago, IL 60607-7045 (United States)

    2005-12-01

    This paper is an introduction to relationships between knot theory and theoretical physics. We give an exposition of the theory of polynomial invariants of knots and links, the Witten functional integral formulation of knot and link invariants, and the beginnings of topological quantum field theory, and show how the theory of knots is related to a number of key issues in mathematical physics, including loop quantum gravity and quantum information theory. Along with the references cited in the text below, we also recommend the following as sources of background information.

  14. Statics and dynamics of DNA knotting

    Science.gov (United States)

    Orlandini, Enzo

    2018-02-01

    Knots and entanglement in polymers and biopolymers such as DNA and proteins constitute a timely topic that spans various scientific disciplines ranging from physics to chemistry, biology and mathematics. Although in the past many advancements have been made in understanding the equilibrium knotting probability and knot complexity of long polymer chains in solutions, many questions have been addressed in recent years by both experimental and theoretical means—for instance, how the knotting probability depends on the quality of the solvent, the elastic properties of the molecule and its degree of confinement. How knots form, evolve and eventually disappear in a fluctuating chain. Are the equilibrium and non-equilibrium properties of knotted molecules affected by the knot swelling/shrinking dynamics? Moreover, thanks to the great advance in nanotechnology and micromanipulation techniques, nowadays knots can be ‘manually’ tied in a single DNA molecule, followed during their motion along the chains, forced to pass through nanopores, or stretched by external forces or elongational flows. All these experimental approaches allow access to new information on the interplay of topology and polymer physics, and this has opened new perspectives in the field. Here, we provide an overview of the current knowledge of this topic, stressing the main results obtained, including the recent developments in experimental and computational approaches. Since almost all experiments on knotting involve DNA, the review will be mainly focused on the topological properties of this fascinating and biologically relevant molecule.

  15. The entropic cost to tie a knot

    International Nuclear Information System (INIS)

    Baiesi, M; Orlandini, E; Stella, A L

    2010-01-01

    We estimate by Monte Carlo simulations the configurational entropy of N-step polygons in the cubic lattice with fixed knot type. By collecting rich statistics of configurations with very large values of N we are able to analyse the asymptotic behaviour of the partition function of the problem for different knot types. Our results confirm that, in the large N limit, each prime knot is localized in a small region of the polygon, regardless of the possible presence of other knots. Each prime knot component may slide along the unknotted region contributing to the overall configurational entropy with a term proportional to lnN. Furthermore, we discover that the mere existence of a knot requires a well defined entropic cost that scales exponentially with its minimal length. In the case of polygons with composite knots it turns out that the partition function can be simply factorized in terms that depend only on prime components, with an additional combinatorial factor that takes into account the statistical property that by interchanging two identical prime knot components in the polygon the corresponding set of overall configurations remains unaltered. Finally, the above results allow one to conjecture a sequence of inequalities for the connective constants of polygons whose topology varies within a given family of composite knot types

  16. Integral Suture-Handling Techniques for Arthroscopic Sliding Knots

    OpenAIRE

    Kanchanatawan, Wichan; Kongtharvonskul, Jatupon; Dorjiee, Gem; Suppauksorn, Sunikom; Pornvoranunt, Umpire; Karchana, Pongsakorn

    2016-01-01

    In arthroscopic tissue repair, the final step is achieving adequate tissue approximation with a secure knot. The sliding knot is widely preferred over the nonsliding knot, with numerous publications describing knot configurations. However, in the literature there are few published descriptions of suture-handling techniques, even though they are fundamental to arthroscopic knot tying. We describe integral suture-handling techniques for arthroscopic sliding knots to improve the surgeon's perfor...

  17. Protein- mediated enamel mineralization

    Science.gov (United States)

    Moradian-Oldak, Janet

    2012-01-01

    Enamel is a hard nanocomposite bioceramic with significant resilience that protects the mammalian tooth from external physical and chemical damages. The remarkable mechanical properties of enamel are associated with its hierarchical structural organization and its thorough connection with underlying dentin. This dynamic mineralizing system offers scientists a wealth of information that allows the study of basic principals of organic matrix-mediated biomineralization and can potentially be utilized in the fields of material science and engineering for development and design of biomimetic materials. This chapter will provide a brief overview of enamel hierarchical structure and properties as well as the process and stages of amelogenesis. Particular emphasis is given to current knowledge of extracellular matrix protein and proteinases, and the structural chemistry of the matrix components and their putative functions. The chapter will conclude by discussing the potential of enamel for regrowth. PMID:22652761

  18. Differential and symplectic topology of knots and curves

    CERN Document Server

    Tabachnikov, S

    1999-01-01

    This book presents a collection of papers on two related topics: topology of knots and knot-like objects (such as curves on surfaces) and topology of Legendrian knots and links in 3-dimensional contact manifolds. Featured is the work of international experts in knot theory (""quantum"" knot invariants, knot invariants of finite type), in symplectic and contact topology, and in singularity theory. The interplay of diverse methods from these fields makes this volume unique in the study of Legendrian knots and knot-like objects such as wave fronts. A particularly enticing feature of the volume is

  19. Ileosigmoid knot: A case report

    International Nuclear Information System (INIS)

    Baheti, Akshay D; Patel, Darshana; Hira, Priya; Babu, Donald

    2011-01-01

    The ileosigmoid knot is an uncommon but life-threatening cause of closed loop intestinal obstruction. Its treatment is different from a simple volvulus in that it has to be operated upon immediately. Preoperative CT scan diagnosis and prompt treatment can lead to a good outcome. Findings of simultaneous ileal and sigmoid ischemia with non-ischemic colon interposed in between should, in an appropriate clinical setting, indicate this condition. The presence of the whirl sign, medially deviated distal descending colon and cecum, and mesenteric vascular structures from the superior mesenteric vessels that converge toward the sigmoid colon on CT scan help clinch the diagnosis

  20. On two-generator satellite knots

    OpenAIRE

    Bleiler, Steven A.; Jones, Amelia C.

    1997-01-01

    Techniques are introduced which determine the geometric structure of non-simple two-generator $3$-manifolds from purely algebraic data. As an application, the satellite knots in the $3$-sphere with a two-generator presentation in which at least one generator is represented by a meridian for the knot are classified.

  1. Asymptotic laws for random knot diagrams

    Science.gov (United States)

    Chapman, Harrison

    2017-06-01

    We study random knotting by considering knot and link diagrams as decorated, (rooted) topological maps on spheres and pulling them uniformly from among sets of a given number of vertices n, as first established in recent work with Cantarella and Mastin. The knot diagram model is an exciting new model which captures both the random geometry of space curve models of knotting as well as the ease of computing invariants from diagrams. We prove that unknot diagrams are asymptotically exponentially rare, an analogue of Sumners and Whittington’s landmark result for self-avoiding polygons. Our proof uses the same key idea: we first show that knot diagrams obey a pattern theorem, which describes their fractal structure. We examine how quickly this behavior occurs in practice. As a consequence, almost all diagrams are asymmetric, simplifying sampling from this model. We conclude with experimental data on knotting in this model. This model of random knotting is similar to those studied by Diao et al, and Dunfield et al.

  2. Phase behaviour of polyethylene knotted ring chains

    International Nuclear Information System (INIS)

    Wen Xiao-Hui; Xia A-Gen; Chen Hong-Ping; Zhang Lin-Xi

    2011-01-01

    The phase behaviour of polyethylene knotted ring chains is investigated by using molecular dynamics simulations. In this paper, we focus on the collapse of the polyethylene knotted ring chain, and also present the results of linear and ring chains for comparison. At high temperatures, a fully extensive knot structure is observed. The mean-square radius of gyration per bond (S 2 )/(Nb 2 ) and the shape factor (δ*) depend on not only the chain length but also the knot type. With temperature decreasing, chain collapse is observed, and the collapse temperature decreases with the chain length increasing. The actual collapse transition can be determined by the specific heat capacity C v , and the knotted ring chain undergoes gas—liquid—solid-like transition directly. The phase transition of a knotted ring chain is only one-stage collapse, which is different from the polyethylene linear and ring chains. This investigation can provide some insights into the statistical properties of knotted polymer chains. (condensed matter: structural, mechanical, and thermal properties)

  3. Legendrian and transverse cables of positive torus knots

    DEFF Research Database (Denmark)

    B. Etnyre, John; la Fountain, Douglas James; Tosun, Bulent

    In this paper we classify Legendrian and transverse knots in the knot types obtained from positive torus knots by cabling. This classification allows us to demonstrate several new phenomena. Specifically, we show there are knot types that have non-destabilizable Legendrian representatives whose T...

  4. Open knot-tying skills: residents skills assessed

    NARCIS (Netherlands)

    van Empel, P.J.; Verdam, M.G.E.; Huirne, J.A.; Bonjer, H.J.; Meijerink, W.J.; Scheele, F.

    2013-01-01

    Aim: Open knot-tying and suturing skills are fundamental surgical skills, founding many alternative knot-tying techniques. It is therefore mandatory for residents to possess adequate basic open knot-tying skills. The aim of this study was to compare an objective assessment of open knot-tying skills

  5. Knot positioning during McDonald cervical cerclage, does it make a difference? A cohort study.

    Science.gov (United States)

    Atia, Hytham; Ellaithy, Mohamed; Altraigey, Ahmed; Ibrahim, Heba

    2018-05-15

    To study the effect of McDonald cerclage knot position on the different maternal and neonatal outcomes. This historical cohort study included women with singleton pregnancy who had a prophylactic McDonald cervical cerclage between 1 May 2010 and 31 September 2017. Maternal and neonatal outcome parameters were compared between the anterior and posterior knot cerclage procedures. The primary outcome measure was the rate of term birth. 550 Women had a prophylactic McDonald cervical cerclage, 306 with anterior knot (Group A) and 244 with posterior knot (Group B). There were no statistically significant differences regarding gestational age (GA) at delivery (36.3 ± 4.2 versus 35.8 ± 5.3 for groups A and B respectively), term birth rate, post-cerclage cervical length, symptomatic vaginitis, urinary tract infection, difficult cerclage removal and cervical lacerations. Similarly, there were no statistically significant differences as regards the studied neonatal outcomes including take home babies, neonatal intensive care admission, respiratory distress syndrome and neonatal sepsis. Survival analysis on GA at delivery demonstrated no statistically significant difference as regards the proportion of term deliveries in the anterior and posterior knot cerclage groups (log-rank test p-value = .478). Knot positioning during McDonald cervical cerclage, anteriorly or posteriorly, didn't significantly impact the studied maternal and neonatal outcomes.

  6. Enamel formation in vitro in mouse molar explants exposed to amelogenin polypeptides ATMP and LRAP on enamel development.

    Science.gov (United States)

    Ravindranath, Rajeswari M H; Devarajan, Asokan; Bringas, Pablo

    2007-12-01

    The enamel matrix contains amelogenin, leucine-rich amelogenin-polypeptide (LRAP), resulting from alternative splicing of the primary amelogenin-RNA transcript and tyrosine-rich amelogenin-polypeptide (TRAP), a proteolytic product of amelogenin. Presence of amelogenin-trityrosyl-motif peptide (ATMP) distinguishes TRAP from LRAP. The roles of these polypeptides in the formation of enamel remain to be elucidated. The mouse in vitro molar tooth-organ developed from bud stage (E16) was exposed to LRAP, ATMP, and mutated ATMP (T-ATMP, third proline replaced by threonine). The histology and morphometry of the explants on day-12 in culture was examined using Mallory's stain. Guanidine-HCl soluble protein concentrations of explants were compared. The enamel width and protein solubility indicate that the explant on day-12 is comparable to postnatal molar on day-3 in vivo. The enamel of both untreated explants as well as that in vivo is fuchinophilic (acid fuchsin, AF+). ATMP reduced the ameloblast-height, accumulated AF+ spherules at the apical end of ameloblasts, and disrupted enamel-dentin bonding. T-ATMP abrogated deposition of AF+ material on the aniline blue positive (AB+) enamel matrix. LRAP reduced ameloblast-height, increased the enamel-width without disruption (at 17.25 nmol) and increased the density of AF+ dentinal tubules. AF+ substance from the tubules is released onto the surface of the dentin. The Guanidine-HCl-soluble protein is elevated in ATMP-treated explants but decreased in LRAP-treated explants. Exogenous ATMP, T-ATMP and LRAP have divergent effects on developing enamel. Exogenous ATMP, but not LRAP, abrogates enamel-dentin bonding at 17.25 nmol. LRAP may play a role in the differentiation of ameloblasts, growth of enamel and formation of dentinal tubules.

  7. Are There Knots in Chromosomes?

    Directory of Open Access Journals (Sweden)

    Jonathan T. Siebert

    2017-08-01

    Full Text Available Recent developments have for the first time allowed the determination of three-dimensional structures of individual chromosomes and genomes in nuclei of single haploid mouse embryonic stem (ES cells based on Hi–C chromosome conformation contact data. Although these first structures have a relatively low resolution, they provide the first experimental data that can be used to study chromosome and intact genome folding. Here we further analyze these structures and provide the first evidence that G1 phase chromosomes are knotted, consistent with the fact that plots of contact probability vs sequence separation show a power law dependence that is intermediate between that of a fractal globule and an equilibrium structure.

  8. Grid homology for knots and links

    CERN Document Server

    Ozsváth, Peter S; Szabó, Zoltán

    2015-01-01

    Knot theory is a classical area of low-dimensional topology, directly connected with the theory of three-manifolds and smooth four-manifold topology. In recent years, the subject has undergone transformative changes thanks to its connections with a number of other mathematical disciplines, including gauge theory; representation theory and categorification; contact geometry; and the theory of pseudo-holomorphic curves. Starting from the combinatorial point of view on knots using their grid diagrams, this book serves as an introduction to knot theory, specifically as it relates to some of the ab

  9. Molecular knots in biology and chemistry

    International Nuclear Information System (INIS)

    Lim, Nicole C H; Jackson, Sophie E

    2015-01-01

    Knots and entanglements are ubiquitous. Beyond their aesthetic appeal, these fascinating topological entities can be either useful or cumbersome. In recent decades, the importance and prevalence of molecular knots have been increasingly recognised by scientists from different disciplines. In this review, we provide an overview on the various molecular knots found in naturally occurring biological systems (DNA, RNA and proteins), and those created by synthetic chemists. We discuss the current knowledge in these fields, including recent developments in experimental and, in some cases, computational studies which are beginning to shed light into the complex interplay between the structure, formation and properties of these topologically intricate molecules. (paper)

  10. In Search of Functional Advantages of Knots in Proteins.

    Science.gov (United States)

    Dabrowski-Tumanski, Pawel; Stasiak, Andrzej; Sulkowska, Joanna I

    2016-01-01

    We analysed the structure of deeply knotted proteins representing three unrelated families of knotted proteins. We looked at the correlation between positions of knotted cores in these proteins and such local structural characteristics as the number of intra-chain contacts, structural stability and solvent accessibility. We observed that the knotted cores and especially their borders showed strong enrichment in the number of contacts. These regions showed also increased thermal stability, whereas their solvent accessibility was decreased. Interestingly, the active sites within these knotted proteins preferentially located in the regions with increased number of contacts that also have increased thermal stability and decreased solvent accessibility. Our results suggest that knotting of polypeptide chains provides a favourable environment for the active sites observed in knotted proteins. Some knotted proteins have homologues without a knot. Interestingly, these unknotted homologues form local entanglements that retain structural characteristics of the knotted cores.

  11. Studying uniform thickness II: Transversely nonsimple iterated torus knots

    DEFF Research Database (Denmark)

    LaFountain, Douglas

    2011-01-01

    We prove that an iterated torus knot type in the standard contact 3-sphere fails the uniform thickness property (UTP) if and only if it is formed from repeated positive cablings, which is precisely when an iterated torus knot supports the standard contact structure. This is the first complete UTP...... classification for a large class of knots. We also show that all iterated torus knots that fail the UTP support cabling knot types that are transversely non-simple....

  12. Lattices gauge theories in terms of knots

    International Nuclear Information System (INIS)

    Vecernyes, P.

    1989-01-01

    Cluster expansion is developed in lattice gauge theories with finite gauge groups in d≥3 dimensions where the clusters are connected (d - 2)-dimensional surfaces which can branch along (d - 3)-cells. The interaction between them has a knot theoretical interpretation. It can be many body linking or knotting self-interaction. For small enough gauge coupling g the authors prove analyticity of the correlation functions in the variable exp(-1/g 2

  13. On the universality of knot probability ratios

    Energy Technology Data Exchange (ETDEWEB)

    Janse van Rensburg, E J [Department of Mathematics and Statistics, York University, Toronto, Ontario M3J 1P3 (Canada); Rechnitzer, A, E-mail: rensburg@yorku.ca, E-mail: andrewr@math.ubc.ca [Department of Mathematics, University of British Columbia, 1984 Mathematics Road, Vancouver, BC V6T 1Z2 (Canada)

    2011-04-22

    Let p{sub n} denote the number of self-avoiding polygons of length n on a regular three-dimensional lattice, and let p{sub n}(K) be the number which have knot type K. The probability that a random polygon of length n has knot type K is p{sub n}(K)/p{sub n} and is known to decay exponentially with length (Sumners and Whittington 1988 J. Phys. A: Math. Gen. 21 1689-94, Pippenger 1989 Discrete Appl. Math. 25 273-8). Little is known rigorously about the asymptotics of p{sub n}(K), but there is substantial numerical evidence. It is believed that the entropic exponent, {alpha}, is universal, while the exponential growth rate is independent of the knot type but varies with the lattice. The amplitude, C{sub K}, depends on both the lattice and the knot type. The above asymptotic form implies that the relative probability of a random polygon of length n having prime knot type K over prime knot type L. In the thermodynamic limit this probability ratio becomes an amplitude ratio; it should be universal and depend only on the knot types K and L. In this communication we examine the universality of these probability ratios for polygons in the simple cubic, face-centred cubic and body-centred cubic lattices. Our results support the hypothesis that these are universal quantities. For example, we estimate that a long random polygon is approximately 28 times more likely to be a trefoil than be a figure-eight, independent of the underlying lattice, giving an estimate of the intrinsic entropy associated with knot types in closed curves. (fast track communication)

  14. Enamel formation and amelogenesis imperfecta.

    Science.gov (United States)

    Hu, Jan C-C; Chun, Yong-Hee P; Al Hazzazzi, Turki; Simmer, James P

    2007-01-01

    Dental enamel is the epithelial-derived hard tissue covering the crowns of teeth. It is the most highly mineralized and hardest tissue in the body. Dental enamel is acellular and has no physiological means of repair outside of the protective and remineralization potential provided by saliva. Enamel is comprised of highly organized hydroxyapatite crystals that form in a defined extracellular space, the contents of which are supplied and regulated by ameloblasts. The entire process is under genetic instruction. The genetic control of amelogenesis is poorly understood, but requires the activities of multiple components that are uniquely important for dental enamel formation. Amelogenesis imperfecta (AI) is a collective designation for the variety of inherited conditions displaying isolated enamel malformations, but the designation is also used to indicate the presence of an enamel phenotype in syndromes. Recently, genetic studies have demonstrated the importance of genes encoding enamel matrix proteins in the etiology of isolated AI. Here we review the essential elements of dental enamel formation and the results of genetic analyses that have identified disease-causing mutations in genes encoding enamel matrix proteins. In addition, we provide a fresh perspective on the roles matrix proteins play in catalyzing the biomineralization of dental enamel. Copyright 2007 S. Karger AG, Basel.

  15. Legendrian and transverse cables of positive torus knots

    DEFF Research Database (Denmark)

    Etnyre, John; LaFountain, Douglas; Tosun, Bülent

    2012-01-01

    Thurston-Bennequin invariant is arbitrarily far from maximal. We also exhibit Legendrian knots requiring arbitrarily many stabilizations before they become Legendrian isotopic. Similar new phenomena are observed for transverse knots. To achieve these results we define and study "partially thickenable" tori......In this paper we classify Legendrian and transverse knots in the knot types obtained from positive torus knots by cabling. This classification allows us to demonstrate several new phenomena. Specifically, we show there are knot types that have non-destabilizable Legendrian representatives whose...

  16. Hipoplasia Enamel Pada Penderita Penyakit Eksantema

    OpenAIRE

    Dewi saputri

    2008-01-01

    Hipoplasia enamel merupakan gangguan pada masa pemhentukan matriks organik yang menyebabkan gangguan struktur pada enamel sehingga secara klinis terlihat pada suatu bagian dari gigi tidak terbentuk enamel dan kadang-kadang sama sekali tidak terbentuk enamel, serta diikuti dengan perubahan warna pada gigi. Dikenal berbagai faktor penyebab hipoplasia enamel, salah satunya adalah penyakit eksantema yaitu menyebabkan infeksi pada bayi dan anak-anak. Gambaran histopatologis hipoplasia enamel adala...

  17. A Fourth KLK4 Mutation Is Associated with Enamel Hypomineralisation and Structural Abnormalities

    Directory of Open Access Journals (Sweden)

    Claire E. L. Smith

    2017-05-01

    Full Text Available “Amelogenesis imperfecta” (AI describes a group of genetic conditions that result in defects in tooth enamel formation. Mutations in many genes are known to cause AI, including the gene encoding the serine protease, kallikrein related peptidase 4 (KLK4, expressed during the maturation stage of amelogenesis. In this study we report the fourth KLK4 mutation to be identified in autosomal recessively-inherited hypomaturation type AI, c.632delT, p.(L211Rfs*37 (NM_004917.4, NP_004908.4. This homozygous variant was identified in five Pakistani AI families and is predicted to result in a transcript with a premature stop codon that escapes nonsense mediated decay. However, the protein may misfold, as three of six disulphide bonds would be disrupted, and may be degraded or non-functional as a result. Primary teeth were obtained from one affected individual. The enamel phenotype was characterized using high-resolution computerized X-ray tomography (CT, scanning electron microscopy (SEM, energy dispersive X-ray spectroscopy (EDX, and microhardness testing (MH. Enamel from the affected individual (referred to as KLK4 enamel was hypomineralised in comparison with matched control enamel. Furthermore, KLK4 inner enamel was hypomineralised compared with KLK4 outer enamel. SEM showed a clear structural demarcation between KLK4 inner and outer enamel, although enamel structure was similar to control tissue overall. EDX showed that KLK4 inner enamel contained less calcium and phosphorus and more nitrogen than control inner enamel and KLK4 outer enamel. MH testing showed that KLK4 inner enamel was significantly softer than KLK4 outer enamel (p < 0.001. However, the hardness of control inner enamel was not significantly different to that of control outer enamel. Overall, these findings suggest that the KLK4 c.632delT mutation may be a common cause of autosomal recessive AI in the Pakistani population. The phenotype data obtained mirror findings in the Klk4

  18. Microstructure of enamel.

    Science.gov (United States)

    Boyde, A

    1997-01-01

    Enamel is a composite material consisting of mineral and organic phases. The properties of the mineral phase are modulated dramatically by its division into microscopic crystals, cemented together by the organic matrix protein polymer. A good concept of the 3D orientations of the crystals derives from visualizing their growth perpendicular to the surface in which they develop, which is pitted by the secretory poles of the ameloblasts. The arrangement of the crystals is the cause of the discontinuities, known as the prism boundaries or junctions, in the otherwise continuous structure. These locations acquire a more concentrated organic matrix during maturation, and they are both crack stoppers and crack propagation tracks in the adult tissue. Any tendency of prisms to cleave may be reduced by their varicosities, which reflect daily variations in the rate of production; their cross-sectional shape; the non-parallelism of adjacent groups, which develops through translocation of groups of cells across the surface during development; and the support of any one microscopic tissue element by other tissue, including dentine, placed to resist an applied load. Incremental growth lines are preferential cleavage planes within the enamel. Failure patterns of enamel in normal and abnormal use can be explained by these parameters, with additional consideration of functional variation and fatigue.

  19. Dental Enamel Development: Proteinases and Their Enamel Matrix Substrates

    Science.gov (United States)

    Bartlett, John D.

    2013-01-01

    This review focuses on recent discoveries and delves in detail about what is known about each of the proteins (amelogenin, ameloblastin, and enamelin) and proteinases (matrix metalloproteinase-20 and kallikrein-related peptidase-4) that are secreted into the enamel matrix. After an overview of enamel development, this review focuses on these enamel proteins by describing their nomenclature, tissue expression, functions, proteinase activation, and proteinase substrate specificity. These proteins and their respective null mice and human mutations are also evaluated to shed light on the mechanisms that cause nonsyndromic enamel malformations termed amelogenesis imperfecta. Pertinent controversies are addressed. For example, do any of these proteins have a critical function in addition to their role in enamel development? Does amelogenin initiate crystallite growth, does it inhibit crystallite growth in width and thickness, or does it do neither? Detailed examination of the null mouse literature provides unmistakable clues and/or answers to these questions, and this data is thoroughly analyzed. Striking conclusions from this analysis reveal that widely held paradigms of enamel formation are inadequate. The final section of this review weaves the recent data into a plausible new mechanism by which these enamel matrix proteins support and promote enamel development. PMID:24159389

  20. Bicarbonate Transport During Enamel Maturation.

    Science.gov (United States)

    Yin, Kaifeng; Paine, Michael L

    2017-11-01

    Amelogenesis (tooth enamel formation) is a biomineralization process consisting primarily of two stages (secretory stage and maturation stage) with unique features. During the secretory stage, the inner epithelium of the enamel organ (i.e., the ameloblast cells) synthesizes and secretes enamel matrix proteins (EMPs) into the enamel space. The protein-rich enamel matrix forms a highly organized architecture in a pH-neutral microenvironment. As amelogenesis transitions to maturation stage, EMPs are degraded and internalized by ameloblasts through endosomal-lysosomal pathways. Enamel crystallite formation is initiated early in the secretory stage, however, during maturation stage the more rapid deposition of calcium and phosphate into the enamel space results in a rapid expansion of crystallite length and mineral volume. During maturation-stage amelogenesis, the pH value of enamel varies considerably from slightly above neutral to acidic. Extracellular acid-base balance during enamel maturation is tightly controlled by ameloblast-mediated regulatory networks, which include significant synthesis and movement of bicarbonate ions from both the enamel papillary layer cells and ameloblasts. In this review we summarize the carbonic anhydrases and the carbonate transporters/exchangers involved in pH regulation in maturation-stage amelogenesis. Proteins that have been shown to be instrumental in this process include CA2, CA6, CFTR, AE2, NBCe1, SLC26A1/SAT1, SLC26A3/DRA, SLC26A4/PDS, SLC26A6/PAT1, and SLC26A7/SUT2. In addition, we discuss the association of miRNA regulation with bicarbonate transport in tooth enamel formation.

  1. In Search of Functional Advantages of Knots in Proteins.

    OpenAIRE

    Dabrowski-Tumanski, P.; Stasiak, A.; Sulkowska, J.I.

    2016-01-01

    We analysed the structure of deeply knotted proteins representing three unrelated families of knotted proteins. We looked at the correlation between positions of knotted cores in these proteins and such local structural characteristics as the number of intra-chain contacts, structural stability and solvent accessibility. We observed that the knotted cores and especially their borders showed strong enrichment in the number of contacts. These regions showed also increased thermal stability, whe...

  2. On the concordance genus of topologically slice knots

    OpenAIRE

    Hom, Jennifer

    2012-01-01

    The concordance genus of a knot K is the minimum Seifert genus of all knots smoothly concordant to K. Concordance genus is bounded below by the 4-ball genus and above by the Seifert genus. We give a lower bound for the concordance genus of K coming from the knot Floer complex of K. As an application, we prove that there are topologically slice knots with 4-ball genus equal to one and arbitrarily large concordance genus.

  3. Defectos del esmalte, caries en dentición primaria, fuentes de fluoruro y su relación con caries en dientes permanentes Enamel defects, caries in primary dentition and fluoride sources: relationship with caries in permanent teeth

    Directory of Open Access Journals (Sweden)

    Ana Alicia Vallejos-Sánchez

    2007-06-01

    Full Text Available Objetivo: Explorar la relación entre la presencia de defectos del esmalte (DE, la experiencia de caries en la dentición temporal, y la exposición a diversas fuentes de fluoruros, con la presencia de caries en la dentición permanente de niños con dentición mixta. Material y métodos: Se realizó un estudio transversal en 713 sujetos de 6-9 años de edad de 4 escuelas de Campeche, México, mediante un cuestionario dirigido a las madres, y un examen clínico bucal a los niños. La variable dependiente fue la prevalencia de caries en la dentición permanente. Resultados: El promedio de dientes temporales cariados, extraídos y obturados (ceod y dientes permanentes cariados, perdidos y obturados (CPOD fue de 2,48 (2,82 (ceod > 0 = 58,9% y 0,40 (0,98 (CPOD > 0 = 18,2%, respectivamente. El índice SiC (índice de caries significativa, calculado en la dentición temporal fue de 5,85 para los niños de 6 años de edad. En el análisis de regresión logística multivariado permanecieron significativas, después de ajustar por variables de exposición a fluoruros, la mayor edad (odds ratio [OR] = 2,99, el ceod > 0 (OR = 5,46, la menor escolaridad de la madre (OR = 1,57 y una interacción entre sexo y defectos del esmalte. Conclusiones: Las caries en la dentición temporal y permanente fueron relativamente menores que las observaciones publicadas por otros estudios en México. Los resultados confirmaron que la caries en la dentición temporal se asoció fuertemente con la caries en la dentición permanente. No hubo una relación significativa entre las fuentes de fluoruro y la caries dental en la dentición permanente.Objective: To examine the relationship between the presence of enamel defects, dental caries in primary teeth, and exposure to various fluoride technologies and the presence of dental caries in permanent teeth in children with mixed dentition. Materials and methods: A cross-sectional study was conducted in 713 children aged 6-9 years old

  4. Knotcraft the practical and entertaining art of tying knots

    CERN Document Server

    Macfarlan, Allan and Paulette

    1983-01-01

    Comprehensive reference work explains how to tie hundreds of practical (and decorative) knots in clear illustrations and precisely worded written instructions. Ideal for boaters and campers. Also covers knots in history, knot mystery and magic, and games, stunts and tricks with rope. Introduction. Index. 166 black-and-white illustrations.

  5. Fluoride varnishes and enamel caries

    NARCIS (Netherlands)

    Bruyn, Hugo de

    1987-01-01

    Topical fluoride applications have the aim of increasing the fluoride uptake in enamel and consequently reducing caries. In the early ‘60s fluoride varnishes were introduced because they had a long contact period with the enamel which resulted in a higher fluoride uptake than from other topical

  6. Silicate enamel for alloyed steel

    International Nuclear Information System (INIS)

    Ket'ko, K.K.

    1976-01-01

    The use of silicate enamels in the metallurgical industry is discussed. Presented are the composition and the physico-chemical properties of the silicate enamel developed at the factory 'Krasnyj Oktyabr'. This enamel can be used in the working conditions both in the liquid and the solid state. In so doing the enamel is melted at 1250 to 1300 deg C, granulated and then reduced to a fraction of 0.3 to 0.5 mm. The greatest homogeneity is afforded by a granulated enamel. The trials have shown that the conversion of the test ingots melted under a layer of enamel leads to the smaller number of the ingots rejected for surface defect reasons and the lower metal consumption for slab cleaning. The cost of the silicate enamel is somewhat higher than that of synthetic slags but its application to the melting of stainless steels is still economically beneficial and technologically reasonable. Preliminary calculations only for steel EhI4IEh have revealed that the use of this enamel saves annually over 360000 roubles [ru

  7. Morphology and fracture of enamel.

    Science.gov (United States)

    Myoung, Sangwon; Lee, James; Constantino, Paul; Lucas, Peter; Chai, Herzl; Lawn, Brian

    2009-08-25

    This study examines the inter-relation between enamel morphology and crack resistance by sectioning extracted human molars after loading to fracture. Cracks appear to initiate from tufts, hypocalcified defects at the enamel-dentin junction, and grow longitudinally around the enamel coat to produce failure. Microindentation corner cracks placed next to the tufts in the sections deflect along the tuft interfaces and occasionally penetrate into the adjacent enamel. Although they constitute weak interfaces, the tufts are nevertheless filled with organic matter, and appear to be stabilized against easy extension by self-healing, as well as by mutual stress-shielding and decussation, accounting at least in part for the capacity of tooth enamel to survive high functional forces.

  8. Mechanical characterization of enamel coated steel bars.

    Science.gov (United States)

    2012-12-01

    In this study, the corrosion process of enamel-coated deformed rebar completely immersed in 3.5 wt.% NaCl solution was evaluated : over a period of 84 days by EIS testing. Three types of enamel coating were investigated: pure enamel, 50/50 enamel coa...

  9. Four-manifolds, geometries and knots

    CERN Document Server

    Hillman, Jonathan A

    2007-01-01

    The goal of this book is to characterize algebraically the closed 4-manifolds that fibre nontrivially or admit geometries in the sense of Thurston, or which are obtained by surgery on 2-knots, and to provide a reference for the topology of such manifolds and knots. The first chapter is purely algebraic. The rest of the book may be divided into three parts: general results on homotopy and surgery (Chapters 2-6), geometries and geometric decompositions (Chapters 7-13), and 2-knots (Chapters 14-18). In many cases the Euler characteristic, fundamental group and Stiefel-Whitney classes together form a complete system of invariants for the homotopy type of such manifolds, and the possible values of the invariants can be described explicitly. The strongest results are characterizations of manifolds which fibre homotopically over S^1 or an aspherical surface (up to homotopy equivalence) and infrasolvmanifolds (up to homeomorphism). As a consequence 2-knots whose groups are poly-Z are determined up to Gluck reconstruc...

  10. The Ileosigmoid Knot: A Case Report

    African Journals Online (AJOL)

    because the clinical signs are difficult to define and the ... describe a case of ileosigmoid knotting in a 40 year old male and .... Prompt relief of obstruction by an emergency laparatomy is a ... the bowel leading to perforation, fecal peritonitis and.

  11. Refined large N duality for knots

    DEFF Research Database (Denmark)

    Kameyama, Masaya; Nawata, Satoshi

    We formulate large N duality of U(N) refined Chern-Simons theory with a torus knot/link in S³. By studying refined BPS states in M-theory, we provide the explicit form of low-energy effective actions of Type IIA string theory with D4-branes on the Ω-background. This form enables us to relate...

  12. Minimal knotted polygons in cubic lattices

    International Nuclear Information System (INIS)

    Van Rensburg, E J Janse; Rechnitzer, A

    2011-01-01

    In this paper we examine numerically the properties of minimal length knotted lattice polygons in the simple cubic, face-centered cubic, and body-centered cubic lattices by sieving minimal length polygons from a data stream of a Monte Carlo algorithm, implemented as described in Aragão de Carvalho and Caracciolo (1983 Phys. Rev. B 27 1635), Aragão de Carvalho et al (1983 Nucl. Phys. B 215 209) and Berg and Foester (1981 Phys. Lett. B 106 323). The entropy, mean writhe, and mean curvature of minimal length polygons are computed (in some cases exactly). While the minimal length and mean curvature are found to be lattice dependent, the mean writhe is found to be only weakly dependent on the lattice type. Comparison of our results to numerical results for the writhe obtained elsewhere (see Janse van Rensburg et al 1999 Contributed to Ideal Knots (Series on Knots and Everything vol 19) ed Stasiak, Katritch and Kauffman (Singapore: World Scientific), Portillo et al 2011 J. Phys. A: Math. Theor. 44 275004) shows that the mean writhe is also insensitive to the length of a knotted polygon. Thus, while these results for the mean writhe and mean absolute writhe at minimal length are not universal, our results demonstrate that these values are quite close the those of long polygons regardless of the underlying lattice and length

  13. Virtual knotting in proteins and other open curves

    Science.gov (United States)

    Alexander, Keith; Taylor, Alexander; Dennis, Mark

    Long filaments naturally knot, from string to long-chain molecules. Knotting in a filament affects its properties, and may be very stable or disappear under slight manipulation. Knotting has been identified in protein backbones for which these mechanical constraints are of fundamental importance to their function, although they are open curves in which knots are not mathematically well defined; knotting can only be identified by closing the ends of the chain. We introduce a new method for resolving knotting in open curves using virtual knots, a wider class of topological objects that do not use a classical closure, capturing the topological ambiguity of open curves. Having analysed all proteins in the Protein Data Bank by this new scheme, we recover and extend previous knotting results, and identify topological interest in some new cases. The statistics of virtual knots in proteins are compared with those of Hamiltonian subchains on cubic lattices, identifying a regime of open curves in which the virtual knotting description is likely to be important. This work was supported by the Leverhulme Trust Programme Grant ``Scientific Properties of Complex Knots'' and the EPSRC.

  14. Three-dimensional primate molar enamel thickness.

    Science.gov (United States)

    Olejniczak, Anthony J; Tafforeau, Paul; Feeney, Robin N M; Martin, Lawrence B

    2008-02-01

    Molar enamel thickness has played an important role in the taxonomic, phylogenetic, and dietary assessments of fossil primate teeth for nearly 90 years. Despite the frequency with which enamel thickness is discussed in paleoanthropological discourse, methods used to attain information about enamel thickness are destructive and record information from only a single plane of section. Such semidestructive planar methods limit sample sizes and ignore dimensional data that may be culled from the entire length of a tooth. In light of recently developed techniques to investigate enamel thickness in 3D and the frequent use of enamel thickness in dietary and phylogenetic interpretations of living and fossil primates, the study presented here aims to produce and make available to other researchers a database of 3D enamel thickness measurements of primate molars (n=182 molars). The 3D enamel thickness measurements reported here generally agree with 2D studies. Hominoids show a broad range of relative enamel thicknesses, and cercopithecoids have relatively thicker enamel than ceboids, which in turn have relatively thicker enamel than strepsirrhine primates, on average. Past studies performed using 2D sections appear to have accurately diagnosed the 3D relative enamel thickness condition in great apes and humans: Gorilla has the relatively thinnest enamel, Pan has relatively thinner enamel than Pongo, and Homo has the relatively thickest enamel. Although the data set presented here has some taxonomic gaps, it may serve as a useful reference for researchers investigating enamel thickness in fossil taxa and studies of primate gnathic biology.

  15. Studies of direct electroinsulating enamels

    International Nuclear Information System (INIS)

    Siwulski, S.; Gruszka, B.; Nocun, M.

    1998-01-01

    The results of studies on the influence of chemical composition of direct electroinsulating enamel on its properties were presented. The influence of alkaline Li 2 O, Na 2 O, K 2 O and adhesion promoting oxides CoO, NiO, CuO, MoO 3 on the frits properties were estimated. The characteristic temperature T g and T m as well as flowability were measured. The dielectric properties of frits and prepared enamels were also measured. Enamel substrates were prepared and tested for application in thick hybrid circuit technology. (author)

  16. Carriers with functional null mutations in LAMA3 have localized enamel abnormalities due to haploinsufficiency

    NARCIS (Netherlands)

    Gostynska, Katarzyna B.; Yuen, Wing Yan; Pasmooij, Anna Maria Gerdina; Stellingsma, Cornelius; Pas, Hendri H.; Lemmink, Henny; Jonkman, Marcel F.

    2017-01-01

    The hereditary blistering disease junctional epidermolysis bullosa (JEB) is always accompanied by structural enamel abnormalities of primary and secondary dentition, characterized as amelogenesis imperfecta. Autosomal recessive mutations in LAMA3, LAMB3 and LAMC2 encoding the heterotrimer laminin

  17. Surface-knots in 4-space an introduction

    CERN Document Server

    Kamada, Seiichi

    2017-01-01

    This introductory volume provides the basics of surface-knots and related topics, not only for researchers in these areas but also for graduate students and researchers who are not familiar with the field. Knot theory is one of the most active research fields in modern mathematics. Knots and links are closed curves (one-dimensional manifolds) in Euclidean 3-space, and they are related to braids and 3-manifolds. These notions are generalized into higher dimensions. Surface-knots or surface-links are closed surfaces (two-dimensional manifolds) in Euclidean 4-space, which are related to two-dimensional braids and 4-manifolds. Surface-knot theory treats not only closed surfaces but also surfaces with boundaries in 4-manifolds. For example, knot concordance and knot cobordism, which are also important objects in knot theory, are surfaces in the product space of the 3-sphere and the interval. Included in this book are basics of surface-knots and the related topics of classical knots, the motion picture method, surf...

  18. Knot invariants and higher representation theory

    CERN Document Server

    Webster, Ben

    2018-01-01

    The author constructs knot invariants categorifying the quantum knot variants for all representations of quantum groups. He shows that these invariants coincide with previous invariants defined by Khovanov for \\mathfrak{sl}_2 and \\mathfrak{sl}_3 and by Mazorchuk-Stroppel and Sussan for \\mathfrak{sl}_n. The author's technique is to study 2-representations of 2-quantum groups (in the sense of Rouquier and Khovanov-Lauda) categorifying tensor products of irreducible representations. These are the representation categories of certain finite dimensional algebras with an explicit diagrammatic presentation, generalizing the cyclotomic quotient of the KLR algebra. When the Lie algebra under consideration is \\mathfrak{sl}_n, the author shows that these categories agree with certain subcategories of parabolic category \\mathcal{O} for \\mathfrak{gl}_k.

  19. Towards effective topological field theory for knots

    Directory of Open Access Journals (Sweden)

    A. Mironov

    2015-10-01

    Full Text Available Construction of (colored knot polynomials for double-fat graphs is further generalized to the case when “fingers” and “propagators” are substituting R-matrices in arbitrary closed braids with m-strands. Original version of [25] corresponds to the case m=2, and our generalization sheds additional light on the structure of those mysterious formulas. Explicit expressions are now combined from Racah matrices of the type R⊗R⊗R¯⟶R¯ and mixing matrices in the sectors R⊗3⟶Q. Further extension is provided by composition rules, allowing to glue two blocks, connected by an m-strand braid (they generalize the product formula for ordinary composite knots with m=1.

  20. A state enumeration of the foil knot

    OpenAIRE

    Ramaharo, Franck; Rakotondrajao, Fanja

    2017-01-01

    We split the crossings of the foil knot and enumerate the resulting states with a generating polynomial. Unexpectedly, the number of such states which consist of two components are given by the lazy caterer's sequence. This sequence describes the maximum number of planar regions that is obtained with a given number of straight lines. We then establish a bijection between this partition of the plane and the concerned foil splits sequence.

  1. Computation of Hyperbolic Structures in Knot Theory

    OpenAIRE

    Weeks, Jeffrey R.

    2003-01-01

    This chapter from the upcoming Handbook of Knot Theory (eds. Menasco and Thistlethwaite) shows how to construct hyperbolic structures on link complements and perform hyperbolic Dehn filling. Along with a new elementary exposition of the standard ideas from Thurston's work, the article includes never-before-published explanations of SnapPea's algorithms for triangulating a link complement efficiently and for converging quickly to the hyperbolic structure while avoiding singularities in the par...

  2. Induction effects of torus knots and unknots

    Science.gov (United States)

    Oberti, Chiara; Ricca, Renzo L.

    2017-09-01

    Geometric and topological aspects associated with induction effects of field lines in the shape of torus knots/unknots are examined and discussed in detail. Knots are assumed to lie on a mathematical torus of circular cross-section and are parametrized by standard equations. The induced field is computed by direct integration of the Biot-Savart law. Field line patterns of the induced field are obtained and several properties are examined for a large family of knots/unknots up to 51 crossings. The intensity of the induced field at the origin of the reference system (center of the torus) is found to depend linearly on the number of toroidal coils and reaches maximum values near the boundary of the mathematical torus. New analytical estimates and bounds on energy and helicity are established in terms of winding number and minimum crossing number. These results find useful applications in several contexts when the source field is either vorticity, electric current or magnetic field, from vortex dynamics to astrophysics and plasma physics, where highly braided magnetic fields and currents are present.

  3. An association of external and internal enamel pearls.

    OpenAIRE

    Mahajan S; Charan C

    2005-01-01

    We report a rare case of an association of external enamel pearl with internal enamel pearl on the root of a molar. To the best of our knowledge, association of external and internal enamel pearls has not been previously reported. We discussed the histogenesis of enamel pearls and proposed that internal enamel pearl formation may be a continuation of formation of external enamel pearl.

  4. Motion of Knots in DNA Stretched by Elongational Fields

    Science.gov (United States)

    Klotz, Alexander R.; Soh, Beatrice W.; Doyle, Patrick S.

    2018-05-01

    Knots in DNA occur in biological systems, serve as a model system for polymer entanglement, and affect the efficacy of modern genomics technologies. We study the motion of complex knots in DNA by stretching molecules with a divergent electric field that provides an elongational force. We demonstrate that the motion of knots is nonisotropic and driven towards the closest end of the molecule. We show for the first time experimentally that knots can go from a mobile to a jammed state by varying an applied strain rate, and that this jamming is reversible. We measure the mobility of knots as a function of strain rate, demonstrating the conditions under which knots can be driven towards the ends of the molecule and untied.

  5. Modeling the Effects of Knots in Structural Timber

    DEFF Research Database (Denmark)

    Foley, Christina

    The main purpose of the pursued research presented in this thesis is to increase knowledge of the effects of knots in structural timber so that characteristics of weaker timber may be determined and applied to improve current grading techniques. In the process, a three-dimensional fiber paradigm...... are given to Shigo's knot formation theory, and thus predicts two separate patterns of fiber direction within annual growth layers related to live knots. In order to determine the possibility to practically and non destructively predict local material directions in structural timber with the three...... was established, which describes variations of radial growth direction and fiber orientation related to knots in timber. The adaptability of the paradigm allows practically any softwood knot and its effect on surrounding wood material to be modeled with an accuracy that is limited only by input data. The knot...

  6. Sampling large random knots in a confined space

    International Nuclear Information System (INIS)

    Arsuaga, J; Blackstone, T; Diao, Y; Hinson, K; Karadayi, E; Saito, M

    2007-01-01

    DNA knots formed under extreme conditions of condensation, as in bacteriophage P4, are difficult to analyze experimentally and theoretically. In this paper, we propose to use the uniform random polygon model as a supplementary method to the existing methods for generating random knots in confinement. The uniform random polygon model allows us to sample knots with large crossing numbers and also to generate large diagrammatically prime knot diagrams. We show numerically that uniform random polygons sample knots with large minimum crossing numbers and certain complicated knot invariants (as those observed experimentally). We do this in terms of the knot determinants or colorings. Our numerical results suggest that the average determinant of a uniform random polygon of n vertices grows faster than O(e n 2 )). We also investigate the complexity of prime knot diagrams. We show rigorously that the probability that a randomly selected 2D uniform random polygon of n vertices is almost diagrammatically prime goes to 1 as n goes to infinity. Furthermore, the average number of crossings in such a diagram is at the order of O(n 2 ). Therefore, the two-dimensional uniform random polygons offer an effective way in sampling large (prime) knots, which can be useful in various applications

  7. Sampling large random knots in a confined space

    Science.gov (United States)

    Arsuaga, J.; Blackstone, T.; Diao, Y.; Hinson, K.; Karadayi, E.; Saito, M.

    2007-09-01

    DNA knots formed under extreme conditions of condensation, as in bacteriophage P4, are difficult to analyze experimentally and theoretically. In this paper, we propose to use the uniform random polygon model as a supplementary method to the existing methods for generating random knots in confinement. The uniform random polygon model allows us to sample knots with large crossing numbers and also to generate large diagrammatically prime knot diagrams. We show numerically that uniform random polygons sample knots with large minimum crossing numbers and certain complicated knot invariants (as those observed experimentally). We do this in terms of the knot determinants or colorings. Our numerical results suggest that the average determinant of a uniform random polygon of n vertices grows faster than O(e^{n^2}) . We also investigate the complexity of prime knot diagrams. We show rigorously that the probability that a randomly selected 2D uniform random polygon of n vertices is almost diagrammatically prime goes to 1 as n goes to infinity. Furthermore, the average number of crossings in such a diagram is at the order of O(n2). Therefore, the two-dimensional uniform random polygons offer an effective way in sampling large (prime) knots, which can be useful in various applications.

  8. Sampling large random knots in a confined space

    Energy Technology Data Exchange (ETDEWEB)

    Arsuaga, J [Department of Mathematics, San Francisco State University, 1600 Holloway Ave, San Francisco, CA 94132 (United States); Blackstone, T [Department of Computer Science, San Francisco State University, 1600 Holloway Ave., San Francisco, CA 94132 (United States); Diao, Y [Department of Mathematics and Statistics, University of North Carolina at Charlotte, Charlotte, NC 28223 (United States); Hinson, K [Department of Mathematics and Statistics, University of North Carolina at Charlotte, Charlotte, NC 28223 (United States); Karadayi, E [Department of Mathematics, University of South Florida, 4202 E Fowler Avenue, Tampa, FL 33620 (United States); Saito, M [Department of Mathematics, University of South Florida, 4202 E Fowler Avenue, Tampa, FL 33620 (United States)

    2007-09-28

    DNA knots formed under extreme conditions of condensation, as in bacteriophage P4, are difficult to analyze experimentally and theoretically. In this paper, we propose to use the uniform random polygon model as a supplementary method to the existing methods for generating random knots in confinement. The uniform random polygon model allows us to sample knots with large crossing numbers and also to generate large diagrammatically prime knot diagrams. We show numerically that uniform random polygons sample knots with large minimum crossing numbers and certain complicated knot invariants (as those observed experimentally). We do this in terms of the knot determinants or colorings. Our numerical results suggest that the average determinant of a uniform random polygon of n vertices grows faster than O(e{sup n{sup 2}}). We also investigate the complexity of prime knot diagrams. We show rigorously that the probability that a randomly selected 2D uniform random polygon of n vertices is almost diagrammatically prime goes to 1 as n goes to infinity. Furthermore, the average number of crossings in such a diagram is at the order of O(n{sup 2}). Therefore, the two-dimensional uniform random polygons offer an effective way in sampling large (prime) knots, which can be useful in various applications.

  9. Dental Enamel Defects and Celiac Disease

    Science.gov (United States)

    ... Digestive System & How it Works Zollinger-Ellison Syndrome Dental Enamel Defects and Celiac Disease Celiac disease manifestations ... affecting any organ or body system. One manifestation—dental enamel defects—can help dentists and other health ...

  10. Properties of hot rolled steels for enamelling

    International Nuclear Information System (INIS)

    Gavrilovski, Dragica; Gavrilovski, Milorad

    2003-01-01

    The results of an investigation of the structure and properties of experimental produced hot rolled steels suitable for enamelling are presented in the paper. Hot rolled steels for enamelling represent a special group of the steels for conventional enamelling. Their quality has to be adapted to the method and conditions of enamelling. Therefore, these steels should meet some specific requirements. In addition to usual investigation of the chemical composition and mechanical properties, microstructure and quality of the steel surface also were investigated. The basic aim was to examine steels capability for enamelling, i. e. steels resistance to the fish scales phenomena, by trial enamelling, as well as quality of the steel - enamel contact surface, to evaluate the binding. Also, the changes of the mechanical properties, especially the yield point, during thermal treatment, as a very specific requirement, were investigated, by simplified method. Good results were obtained confirming the steels capability for enamelling. (Original)

  11. The fracture behaviour of dental enamel

    OpenAIRE

    Bechtle, Sabine; Habelitz, Stefan; Klocke, Arndt; Fett, Theo; Schneider, Gerold A.

    2009-01-01

    Abstract Enamel is the hardest tissue in the human body covering the crowns of teeth. Whereas the underlying dental material dentin is very well characterised in terms of mechanical and fracture properties, available data for enamel are quite limited and are apart from the most recent investigation mainly based on indentation studies. Within the current study, stable crack-growth experiments in bovine enamel have been performed, to measure fracture resistance curves for enamel. Single edge...

  12. The development of enamel tubules during the formation of enamel in the marsupial Monodelphis domestica.

    OpenAIRE

    Sasagawa, I; Ferguson, M W

    1991-01-01

    In Monodelphis domestica, although both processes from odontoblasts and projections from ameloblasts were found in developing enamel, the majority of the contents of enamel tubules were probably processes that originated from odontoblasts. Processes from odontoblasts penetrating into enamel touched part of the ameloblasts in the stage of enamel formation. No specialised cell junctions were seen at the adherence between the two. There were no enamel tubules in the aprismatic and pseudoprismati...

  13. Enamel renal syndrome: A rare case report

    Directory of Open Access Journals (Sweden)

    S V Kala Vani

    2012-01-01

    Full Text Available Enamel renal syndrome is a very rare disorder associating amelogenesis imperfecta with nephrocalcinosis. It is known by various synonyms such as amelogenesis imperfecta nephrocalcinosis syndrome, MacGibbon syndrome, Lubinsky syndrome, and Lubinsky-MacGibbon syndrome. It is characterized by enamel agenesis and medullary nephrocalcinosis. This paper describes enamel renal syndrome in a female patient born in a consanguineous family.

  14. Optical knots and contact geometry II. From Ranada dyons to transverse and cosmetic knots

    Energy Technology Data Exchange (ETDEWEB)

    Kholodenko, Arkady L., E-mail: string@clemson.edu

    2016-08-15

    Some time ago Ranada (1989) obtained new nontrivial solutions of the Maxwellian gauge fields without sources. These were reinterpreted in Kholodenko (2015) [10] (part I) as particle-like (monopoles, dyons, etc.). They were obtained by the method of Abelian reduction of the non-Abelian Yang–Mills functional. The developed method uses instanton-type calculations normally employed for the non-Abelian gauge fields. By invoking the electric–magnetic duality it then becomes possible to replace all known charges/masses by the particle-like solutions of the source-free Abelian gauge fields. To employ these results in high energy physics, it is essential to extend Ranada’s results by carefully analyzing and classifying all dynamically generated knotted/linked structures in gauge fields, including those discovered by Ranada. This task is completed in this work. The study is facilitated by the recent progress made in solving the Moffatt conjecture. Its essence is stated as follows: in steady incompressible Euler-type fluids the streamlines could have knots/links of all types. By employing the correspondence between the ideal hydrodynamics and electrodynamics discussed in part I and by superimposing it with the already mentioned method of Abelian reduction, it is demonstrated that in the absence of boundaries only the iterated torus knots and links could be dynamically generated. Obtained results allow to develop further particle-knot/link correspondence studied in Kholodenko (2015) [13].

  15. Analysis of the tractive force pattern on a knot by force measurement during laparoscopic knot tying.

    Science.gov (United States)

    Takayasu, Kenta; Yoshida, Kenji; Kinoshita, Hidefumi; Yoshimoto, Syunsuke; Oshiro, Osamu; Matsuda, Tadashi

    2017-07-19

    Quantifying surgical skills assists novice surgeons when learning operative techniques. We measured the interaction force at a ligation point and clarified the features of the force pattern among surgeons with different skill levels during laparoscopic knot tying. Forty-four surgeons were divided into three groups based on experience: 13 novice (0-5 years), 16 intermediate (6-15 years), and 15 expert (16-30 years). To assess the tractive force direction and volume during knot tying, we used a sensor that measures six force-torque values (x-axis: Fx, y-axis: Fy, z-axis: Fz, and xy-axis: Fxy) attached to a slit Penrose drain. All participants completed one double knot and five single knot sequences. We recorded completion time, force volume (FV), maximum force (MF), time over 1.5 N, duration of non-zero force, and percentage time when vertical force exceeded horizontal force (PTz). There was a significant difference between groups for completion time (p = 0.007); FV (total: p = 0.002; Fx: p = 0.004, Fy: p = 0.007, Fxy: p = 0.004, Fz: p force (p = 0.029); and PTz (p force pattern at the ligation point during suturing by surgeons with three levels of experience using a force measurement system. We revealed that both force volume and force direction differed depending on surgeons' skill level during knot tying. Copyright © 2017. Published by Elsevier Inc.

  16. Great Knot Calidris tenuirostris at Lutembe Bay, Uganda

    African Journals Online (AJOL)

    Unfortunately it became nervous and flew to another island and we were unable to pursue it before darkness fell. I was, however, able to take some record shots. I circulated the best of four poor photographs to a few birding colleagues for their opinion, and the general consensus favoured Red Knot rather than Great Knot.

  17. Ileosigmoid knotting in pregnancy: A case report from Zimbabwe ...

    African Journals Online (AJOL)

    Ileosigmoid knotting (ISK), also known as compound volvulus, is a rare cause of intestinal obstruction wherein the ileum wraps around the base of the sigmoid colon and forms a knot with rapid progression to gangrene. The worldwide incidence of ISK ranges from 1 in 1500 to 1 in 66,431. ISK is particularly rare in pregnancy ...

  18. Relative symplectic caps, 4-genus and fibered knots

    Indian Academy of Sciences (India)

    We prove relative versions of the symplectic capping theorem and sufficiency of Giroux's criterion for Stein fillability and use these to study the 4-genus of knots. More precisely, suppose we have a symplectic 4-manifold with convex boundary and a symplectic surface in such that is a transverse knot in .

  19. Factorization of differential expansion for antiparallel double-braid knots

    Science.gov (United States)

    Morozov, A.

    2016-09-01

    Continuing the quest for exclusive Racah matrices, which are needed for evaluation of colored arborescent-knot polynomials in Chern-Simons theory, we suggest to extract them from a new kind of a double-evolution — that of the antiparallel double-braids, which is a simple two-parametric family of two-bridge knots, generalizing the one-parametric family of twist knots. In the case of rectangular representations R = [ r s ] we found an evidence that the corresponding differential expansion miraculously factorizes and can be obtained from that for the twist knots. This reduces the problem of rectangular exclusive Racah to constructing the answers for just a few twist knots. We develop a recent conjecture on the structure of differential expansion for the simplest members of this family (the trefoil and the figure-eight knot) and provide the exhaustive answer for the first unknown case of R = [33]. The answer includes HOMFLY of arbitrary twist and double-braid knots and Racah matrices overline{S} and S — what allows to calculate [33]-colored polynomials for arbitrary arborescent (double-fat) knots. For generic rectangular representations fully described are only the contributions of the single-floor pyramids. One step still remains to be done.

  20. True Umbilical Cord Knot Leading to Fetal Demise | Ikechebelu ...

    African Journals Online (AJOL)

    The incidence of true knot of the umbilical cord is not only very low but it is often undiagnosed antenatally when present despite the availability of prenatal ultrasonography. When the true knot remains tight, it may impede the circulation of the fetus and may result to fetal death in utero especially in labor. We report a very ...

  1. Borromean Triangles and Prime Knots in an Ancient Temple

    Indian Academy of Sciences (India)

    a computer mouse with cable which forms the logo of the Topo- logical Quantum .... theory of knots stayed on and was developed into a beautiful. Figure 3. A prime knot ... ematics to build bridges with the inner worlds that these temples seek to ...

  2. Mechanism of Action of TiF4 on Dental Enamel Surface: SEM/EDX, KOH-Soluble F, and X-Ray Diffraction Analysis.

    Science.gov (United States)

    Comar, Lívia P; Souza, Beatriz M; Al-Ahj, Luana P; Martins, Jessica; Grizzo, Larissa T; Piasentim, Isabelle S; Rios, Daniela; Buzalaf, Marília Afonso Rabelo; Magalhães, Ana Carolina

    2017-10-12

    This in vitro study aimed to evaluate the action of TiF4 on sound and carious bovine and human enamel. Sound (S) and pre-demineralised (DE) bovine and human (primary and permanent) enamel samples were treated with TiF4 (pH 1.0) or NaF varnishes (pH 5.0), containing 0.95, 1.95, or 2.45% F for 12 h. The enamel surfaces were analysed using SEM-EDX (scanning electron microscopy/energy-dispersive X-ray spectroscopy) (n = 10, 5 S and 5 DE) and KOH-soluble fluoride was quantified (n = 20, 10 S and 10 DE). Hydroxyapatite powder produced by precipitation method was treated with the corresponding fluoride solutions for 1 min (n = 2). The formed compounds were detected using X-ray diffraction (XRD). All TiF4 varnishes produced a coating layer rich in Ti and F on all types of enamel surface, with micro-cracks in its extension. TiF4 (1.95 and 2.45% F) provided higher fluoride deposition than NaF, especially for bovine enamel (p enamel. The Ti content was higher for bovine and human primary enamel than human permanent enamel, with some differences between S and DE. The XRD analysis showed that TiF4 induced the formation of new compounds such as CaF2, TiO2, and Ti(HPO4)2·H2O. In conclusion, TiF4 (>0.95% F) interacts better, when compared to NaF, with bovine and human primary enamel than with human permanent enamel. TiF4 provoked higher F deposition compared to NaF. Carious enamel showed higher F uptake than sound enamel by TiF4 application, while Ti uptake was dependent on the enamel condition and origin. © 2017 S. Karger AG, Basel.

  3. Atmospheres of polygons and knotted polygons

    International Nuclear Information System (INIS)

    Janse Rensburg, E J Janse; Rechnitzer, A

    2008-01-01

    In this paper we define two statistics a + (ω) and a - (ω), the positive and negative atmospheres of a lattice polygon ω of fixed length n. These statistics have the property that (a + (ω))/(a - (ω)) = p n+2 /p n , where p n is the number of polygons of length n, counted modulo translations. We use the pivot algorithm to sample polygons and to compute the corresponding average atmospheres. Using these data, we directly estimate the growth constants of polygons in two and three dimensions. We find that μ=2.63805±0.00012 in two dimensions and μ=4.683980±0.000042±0.000067 in three dimensions, where the error bars are 67% confidence intervals, and the second error bar in the three-dimensional estimate of μ is an estimated systematic error. We also compute atmospheres of polygons of fixed knot type K sampled by the BFACF algorithm. We discuss the implications of our results and show that different knot types have atmospheres which behave dramatically differently at small values of n

  4. The mean squared writhe of alternating random knot diagrams

    Energy Technology Data Exchange (ETDEWEB)

    Diao, Y; Hinson, K [Department of Mathematics and Statistics University of North Carolina at Charlotte, NC 28223 (United States); Ernst, C; Ziegler, U, E-mail: ydiao@uncc.ed [Department of Mathematics and Computer Science, Western Kentucky University, Bowling Green, KY 42101 (United States)

    2010-12-10

    The writhe of a knot diagram is a simple geometric measure of the complexity of the knot diagram. It plays an important role not only in knot theory itself, but also in various applications of knot theory to fields such as molecular biology and polymer physics. The mean squared writhe of any sample of knot diagrams with n crossings is n when for each diagram at each crossing one of the two strands is chosen as the overpass at random with probability one-half. However, such a diagram is usually not minimal. If we restrict ourselves to a minimal knot diagram, then the choice of which strand is the over- or under-strand at each crossing is no longer independent of the neighboring crossings and a larger mean squared writhe is expected for minimal diagrams. This paper explores the effect on the correlation between the mean squared writhe and the diagrams imposed by the condition that diagrams are minimal by studying the writhe of classes of reduced, alternating knot diagrams. We demonstrate that the behavior of the mean squared writhe heavily depends on the underlying space of diagram templates. In particular this is true when the sample space contains only diagrams of a special structure. When the sample space is large enough to contain not only diagrams of a special type, then the mean squared writhe for n crossing diagrams tends to grow linearly with n, but at a faster rate than n, indicating an intrinsic property of alternating knot diagrams. Studying the mean squared writhe of alternating random knot diagrams also provides some insight into the properties of the diagram generating methods used, which is an important area of study in the applications of random knot theory.

  5. Prevalence of enamel defects and association with dental caries in preschool children.

    Science.gov (United States)

    Massignan, C; Ximenes, M; da Silva Pereira, C; Dias, L; Bolan, M; Cardoso, M

    2016-12-01

    This was to evaluate the prevalence of the developmental defects of enamel (DDE) in primary teeth and its association with dental caries. A cross-sectional study with a randomised representative sample was carried out with 1101 children aged 2-5 years enrolled in public preschools (50% prevalence of DDE in primary teeth, a standard error of 3%, and a confidence level of 95%). Three calibrated dentists (K > 0.62) performed clinical examination. Data collected were: sex, age, DDE (Modified DDE Index) and dental caries (WHO). Descriptive analysis, Chi-square test and multinomial logistic regression were applied for data analysis. Among children, 565 (51.3%) were boys; mean age was 3.7 (±0.9 years). The prevalence of enamel defect was 39.1%; the prevalence of diffuse opacities, demarcated opacities and enamel hypoplasia was 25.3, 19.1 and 6.1%, respectively. The prevalence of dental caries was 31.0%, with mean def-t 1.14 (±2.44). Primary teeth with enamel hypoplasia had three times the odds of having dental caries than those with absence of enamel defects (OR = 3.10; 95% CI: 1.91, 5.01). The presence of enamel defects was moderate and associated with dental caries.

  6. Store-operated Ca2+ Entry Modulates the Expression of Enamel Genes.

    Science.gov (United States)

    Nurbaeva, M K; Eckstein, M; Snead, M L; Feske, S; Lacruz, R S

    2015-10-01

    Dental enamel formation is an intricate process tightly regulated by ameloblast cells. The correct spatiotemporal patterning of enamel matrix protein (EMP) expression is fundamental to orchestrate the formation of enamel crystals, which depend on a robust supply of Ca2+. In the extracellular milieu, Ca2+ -EMP interactions occur at different levels. Despite its recognized role in enamel development, the molecular machinery involved in Ca2+ homeostasis in ameloblasts remains poorly understood. A common mechanism for Ca2+ influx is store-operated Ca2+ entry (SOCE). We evaluated the possibility that Ca2+ influx in enamel cells might be mediated by SOCE and the Ca2+ release-activated Ca2+ (CRAC) channel, the prototypical SOCE channel. Using ameloblast-like LS8 cells, we demonstrate that these cells express Ca2+ -handling molecules and mediate Ca2+ influx through SOCE. As a rise in the cytosolic Ca2+ concentration is a versatile signal that can modulate gene expression, we assessed whether SOCE in enamel cells had any effect on the expression of EMPs. Our results demonstrate that stimulating LS8 cells or murine primary enamel organ cells with thapsigargin to activate SOCE leads to increased expression of Amelx, Ambn, Enam, Mmp20. This effect is reversed when cells are treated with a CRAC channel inhibitor. These data indicate that Ca2+ influx in LS8 cells and enamel organ cells is mediated by CRAC channels and that Ca2+ signals enhance the expression of EMPs. Ca2+ plays an important role not only in mineralizing dental enamel but also in regulating the expression of EMPs. © International & American Associations for Dental Research 2015.

  7. Multimedia article. The keys to the new laparoscopic world Thumbs up! knot and Tornado knot.

    Science.gov (United States)

    Uchida, K; Haruta, N; Okajima, M; Matsuda, M; Yamamoto, M

    2005-06-01

    Most laparoscopic surgeons feel some anxiety when performing intracorporeal knotting with conventional techniques [1, 2]. Two factors contribute to this anxiety. The first is the necessity of recognizing three dimensions on a two-dimensional monitor. The conventional intracorporeal knotting techniques make loops by twisting the thread with a second pair of forceps. This necessitates cooperative movement of both hands, with the added difficulties of depth perception. Regular touch confirmations reduce problems with depth perception. However, touch confirmation is more complicated in laparoscopic surgery than in laparotomy. The second problem is that tied loops can come loose and escape the instruments, especially with hard thread. This is not only stressful but also increases operation time.

  8. On the groundstate energy spectrum of magnetic knots and links

    International Nuclear Information System (INIS)

    Ricca, Renzo L; Maggioni, Francesca

    2014-01-01

    By using analytical results for the constrained minimum energy of magnetic knots we determine the influence of internal twist on the minimum magnetic energy levels of knots and links, and by using ropelength data from the RIDGERUNNER tightening algorithm (Ashton et al 2011 Exp. Math. 20 57–90) we obtain the groundstate energy spectra of the first 250 prime knots and 130 prime links. The two spectra are found to follow an almost identical logarithmic law. By assuming that the number of knot types grows exponentially with the topological crossing number, we show that this generic behavior can be justified by a general relationship between ropelength and crossing number, which is in good agreement with former analytical estimates (Buck and Simon 1999 Topol. Appl. 91 245–57, Diao 2003 J. Knot Theory Ramifications 12 1–16). Moreover, by considering the ropelength averaged over a given knot family, we establish a new connection between the averaged ropelength and the topological crossing number of magnetic knots. (paper)

  9. Knotting probability of self-avoiding polygons under a topological constraint

    Science.gov (United States)

    Uehara, Erica; Deguchi, Tetsuo

    2017-09-01

    We define the knotting probability of a knot K by the probability for a random polygon or self-avoiding polygon (SAP) of N segments having the knot type K. We show fundamental and generic properties of the knotting probability particularly its dependence on the excluded volume. We investigate them for the SAP consisting of hard cylindrical segments of unit length and radius rex. For various prime and composite knots, we numerically show that a compact formula describes the knotting probabilities for the cylindrical SAP as a function of segment number N and radius rex. It connects the small-N to the large-N behavior and even to lattice knots in the case of large values of radius. As the excluded volume increases, the maximum of the knotting probability decreases for prime knots except for the trefoil knot. If it is large, the trefoil knot and its descendants are dominant among the nontrivial knots in the SAP. From the factorization property of the knotting probability, we derive a sum rule among the estimates of a fitting parameter for all prime knots, which suggests the local knot picture and the dominance of the trefoil knot in the case of large excluded volumes. Here we remark that the cylindrical SAP gives a model of circular DNA which is negatively charged and semiflexible, where radius rex corresponds to the screening length.

  10. Knotting probability of self-avoiding polygons under a topological constraint.

    Science.gov (United States)

    Uehara, Erica; Deguchi, Tetsuo

    2017-09-07

    We define the knotting probability of a knot K by the probability for a random polygon or self-avoiding polygon (SAP) of N segments having the knot type K. We show fundamental and generic properties of the knotting probability particularly its dependence on the excluded volume. We investigate them for the SAP consisting of hard cylindrical segments of unit length and radius r ex . For various prime and composite knots, we numerically show that a compact formula describes the knotting probabilities for the cylindrical SAP as a function of segment number N and radius r ex . It connects the small-N to the large-N behavior and even to lattice knots in the case of large values of radius. As the excluded volume increases, the maximum of the knotting probability decreases for prime knots except for the trefoil knot. If it is large, the trefoil knot and its descendants are dominant among the nontrivial knots in the SAP. From the factorization property of the knotting probability, we derive a sum rule among the estimates of a fitting parameter for all prime knots, which suggests the local knot picture and the dominance of the trefoil knot in the case of large excluded volumes. Here we remark that the cylindrical SAP gives a model of circular DNA which is negatively charged and semiflexible, where radius r ex corresponds to the screening length.

  11. Development Enamel Defects in Children Prenatally Exposed to Anti-Epileptic Drugs

    DEFF Research Database (Denmark)

    Jacobsen, Pernille Endrup; Henriksen, Tine Brink; Haubek, Dorte

    2013-01-01

    Objective Some anti-epileptic drugs (AED) have well-known teratogenic effects. The aim of the present study was to elucidate the effect of prenatal exposure to AED and the risk of enamel defects in the primary and permanent dentition. Methods A total of 38 exposed and 129 non-exposed children, 6......–10 years of age, were recruited from the Aarhus Birth Cohort and the Department of Neurology, Viborg Regional Hospital, Denmark. Medication during pregnancy was confirmed by the Danish Prescription Database. All children had their teeth examined and outcomes in terms of enamel opacities and enamel...... hypoplasia were recorded. Results Children prenatally exposed to AED have an increased prevalence of enamel hypoplasia (11% vs. 4%, odds ratio (OR) = 3.6 [95% confidence interval (CI): 0.9 to 15.4]), diffuse opacities (18% vs. 7%, OR = 3.0; [95% CI: 1.0 to 8.7, p3) white opacities (18...

  12. Intracorporeal knotting of a femoral nerve catheter

    Directory of Open Access Journals (Sweden)

    Ghanem, Mohamed

    2015-01-01

    Full Text Available Peripheral nerve catheters are effective and well-established tools to provide postoperative analgesia to patients undergoing orthopedic surgery. The performance of these techniques is usually considered safe. However, placement of nerve catheters may be associated with a considerable number of side effects and major complications have repeatedly been published. In this work, we report on a patient who underwent total knee replacement with spinal anesthesia and preoperative insertion of femoral and sciatic nerve catheters for postoperative analgesia. During insertion of the femoral catheter, significant resistance was encountered upon retracting the catheter. This occurred due to knotting of the catheter. The catheter had to be removed by operative intervention which has to be considered a major complication. The postoperative course was uneventful. The principles for removal of entrapped peripheral catheters are not well established, may differ from those for neuroaxial catheters, and range from cautious manipulation up to surgical intervention.

  13. Motion of charged particles in a knotted electromagnetic field

    International Nuclear Information System (INIS)

    Arrayas, M; Trueba, J L

    2010-01-01

    In this paper we consider the classical relativistic motion of charged particles in a knotted electromagnetic field. After reviewing how to construct electromagnetic knots from maps between the three-sphere and the two-sphere, we introduce a mean quadratic radius of the energy density distribution in order to study some properties of this field. We study the classical relativistic motion of electrons in the electromagnetic field of the Hopf map, and compute their trajectories. It is observed that these electrons initially at rest are strongly accelerated by the electromagnetic force, becoming ultrarelativistic in a period of time that depends on the knot energy and size.

  14. Motion of charged particles in a knotted electromagnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Arrayas, M; Trueba, J L, E-mail: joseluis.trueba@urjc.e [Area de Electromagnetismo, Universidad Rey Juan Carlos, Camino del Molino s/n, 28943 Fuenlabrada, Madrid (Spain)

    2010-06-11

    In this paper we consider the classical relativistic motion of charged particles in a knotted electromagnetic field. After reviewing how to construct electromagnetic knots from maps between the three-sphere and the two-sphere, we introduce a mean quadratic radius of the energy density distribution in order to study some properties of this field. We study the classical relativistic motion of electrons in the electromagnetic field of the Hopf map, and compute their trajectories. It is observed that these electrons initially at rest are strongly accelerated by the electromagnetic force, becoming ultrarelativistic in a period of time that depends on the knot energy and size.

  15. Pinus pinaster Knot: A Source of Polyphenols against Plasmopara viticola.

    Science.gov (United States)

    Gabaston, Julien; Richard, Tristan; Cluzet, Stéphanie; Palos Pinto, Antonio; Dufour, Marie-Cécile; Corio-Costet, Marie-France; Mérillon, Jean-Michel

    2017-10-11

    Pine knot extract from Pinus pinaster byproducts was characterized by UHPLC-DAD-MS and NMR. Fourteen polyphenols divided into four classes were identified as follows: lignans (nortrachelogenin, pinoresinol, matairesinol, isolariciresinol, secoisolariciresinol), flavonoids (pinocembrin, pinobanksin, dihydrokaempferol, taxifolin), stilbenes (pinosylvin, pinosylvin monomethyl ether, pterostilbene), and phenolic acids (caffeic acid, ferulic acid). The antifungal potential of pine knot extract, as well as the main compounds, was tested in vitro against Plasmopara viticola. The ethanolic extract showed a strong antimildew activity. In addition, pinosylvins and pinocembrin demonstrated significant inhibition of zoospore mobility and mildew development. These findings strongly suggest that pine knot is a potential biomass that could be used as a natural antifungal product.

  16. Teaching and Learning of Knot Theory in School Mathematics

    CERN Document Server

    Kawauchi, Akio

    2012-01-01

    This book is the result of a joint venture between Professor Akio Kawauchi, Osaka City University, well-known for his research in knot theory, and the Osaka study group of mathematics education, founded by Professor Hirokazu Okamori and now chaired by his successor Professor Tomoko Yanagimoto, Osaka Kyoiku University. The seven chapters address the teaching and learning of knot theory from several perspectives. Readers will find an extremely clear and concise introduction to the fundamentals of knot theory, an overview of curricular developments in Japan, and in particular a series of teaching

  17. Quandles an introduction to the algebra of knots

    CERN Document Server

    Elhamdadi, Mohamed

    2015-01-01

    From prehistory to the present, knots have been used for purposes both artistic and practical. The modern science of Knot Theory has ramifications for biochemistry and mathematical physics and is a rich source of research projects for undergraduate and graduate students and professionals alike. Quandles are essentially knots translated into algebra. This book provides an accessible introduction to quandle theory for readers with a background in linear algebra. Important concepts from topology and abstract algebra motivated by quandle theory are introduced along the way. With elementary self-co

  18. Enamel proteins mitigate mechanical and structural degradations in mature human enamel during acid attack

    Science.gov (United States)

    Lubarsky, Gennady V.; Lemoine, Patrick; Meenan, Brian J.; Deb, Sanjukta; Mutreja, Isha; Carolan, Patrick; Petkov, Nikolay

    2014-04-01

    A hydrazine deproteination process was used to investigate the role of enamel proteins in the acid erosion of mature human dental enamel. Bright field high resolution transmission electron micrographs and x-ray diffraction analysis show no crystallographic changes after the hydrazine treatment with similar nanoscale hydroxyapatite crystallite size and orientation for sound and de-proteinated enamel. However, the presence of enamel proteins reduces the erosion depth, the loss of hardness and the loss of structural order in enamel, following exposure to citric acid. Nanoindentation creep is larger for sound enamel than for deproteinated enamel but it reduces in sound enamel after acid attack. These novel results are consistent with calcium ion-mediated visco-elasticty in enamel matrix proteins as described previously for nacre, bone and dental proteins. They are also in good agreement with a previous double layer force spectroscopy study by the authors which found that the proteins electrochemically buffer enamel against acid attack. Finally, this suggests that acid attack, and more specifically dental erosion, is influenced by ionic permeation through the enamel layer and that it is mitigated by the enamel protein matrix.

  19. Enamel proteins mitigate mechanical and structural degradations in mature human enamel during acid attack

    International Nuclear Information System (INIS)

    Lubarsky, Gennady V; Lemoine, Patrick; Meenan, Brian J; Deb, Sanjukta; Mutreja, Isha; Carolan, Patrick; Petkov, Nikolay

    2014-01-01

    A hydrazine deproteination process was used to investigate the role of enamel proteins in the acid erosion of mature human dental enamel. Bright field high resolution transmission electron micrographs and x-ray diffraction analysis show no crystallographic changes after the hydrazine treatment with similar nanoscale hydroxyapatite crystallite size and orientation for sound and de-proteinated enamel. However, the presence of enamel proteins reduces the erosion depth, the loss of hardness and the loss of structural order in enamel, following exposure to citric acid. Nanoindentation creep is larger for sound enamel than for deproteinated enamel but it reduces in sound enamel after acid attack. These novel results are consistent with calcium ion-mediated visco-elasticty in enamel matrix proteins as described previously for nacre, bone and dental proteins. They are also in good agreement with a previous double layer force spectroscopy study by the authors which found that the proteins electrochemically buffer enamel against acid attack. Finally, this suggests that acid attack, and more specifically dental erosion, is influenced by ionic permeation through the enamel layer and that it is mitigated by the enamel protein matrix. (papers)

  20. Effects of knot type in the folding of topologically complex lattice proteins

    Science.gov (United States)

    Soler, Miguel A.; Nunes, Ana; Faísca, Patrícia F. N.

    2014-07-01

    The folding properties of a protein whose native structure contains a 52 knot are investigated by means of extensive Monte Carlo simulations of a simple lattice model and compared with those of a 31 knot. A 52 knot embedded in the native structure enhances the kinetic stability of the carrier lattice protein in a way that is clearly more pronounced than in the case of the 31 knot. However, this happens at the expense of a severe loss in folding efficiency, an observation that is consistent with the relative abundance of 31 and 52 knots in the Protein Data Bank. The folding mechanism of the 52 knot shares with that of the 31 knot the occurrence of a threading movement of the chain terminus that lays closer to the knotted core. However, co-concomitant knotting and folding in the 52 knot occurs with negligible probability, in sharp contrast to what is observed for the 31 knot. The study of several single point mutations highlights the importance in the folding of knotted proteins of the so-called structural mutations (i.e., energetic perturbations of native interactions between residues that are critical for knotting but not for folding). On the other hand, the present study predicts that mutations that perturb the folding transition state may significantly enhance the kinetic stability of knotted proteins provided they involve residues located within the knotted core.

  1. evaluation of tomato genotypes for resistance to root-knot

    African Journals Online (AJOL)

    Prof. Adipala Ekwamu

    Tomato production in Ghana is threatened by plant parasitic nematodes, especially the root knot ... to be highly resistant to Meloidogyne spp. and also recorded the lowest reproductive factors of 0.71 and 0.53, respectively. ..... VII International.

  2. Knot theory and a physical state of quantum gravity

    International Nuclear Information System (INIS)

    Liko, Tomas; Kauffman, Louis H

    2006-01-01

    We discuss the theory of knots, and describe how knot invariants arise naturally in gravitational physics. The focus of this review is to delineate the relationship between knot theory and the loop representation of non-perturbative canonical quantum general relativity (loop quantum gravity). This leads naturally to a discussion of the Kodama wavefunction, a state which is conjectured to be the ground state of the gravitational field with positive cosmological constant. This review can serve as a self-contained introduction to loop quantum gravity and related areas. Our intent is to make the paper accessible to a wider audience that may include topologists, knot theorists, and other persons innocent of the physical background to this approach to quantum gravity. (topical review)

  3. Integrated management of root-knot nematode (Meloidogyne ...

    African Journals Online (AJOL)

    Integrated management of root-knot nematode (Meloidogyne incognita) for tomato production and productivity. Bayuh Belay1* ... important food and cash crop of the farmers and is ...... some part of the research budget without any reservation.

  4. Knots, splices and rope-work an illustrated handbook

    CERN Document Server

    Verrill, A Hyatt

    2006-01-01

    This treasury of practical and ornamental knots ranges from easy half-hitches and bow-lines to intricate rope-work projects, such as rope buckles and cask slings. Detailed instructions accompany the 148 drawings.

  5. Khovanov homology for virtual knots with arbitrary coefficients

    International Nuclear Information System (INIS)

    Manturov, Vassily O

    2007-01-01

    The Khovanov homology theory over an arbitrary coefficient ring is extended to the case of virtual knots. We introduce a complex which is well-defined in the virtual case and is homotopy equivalent to the original Khovanov complex in the classical case. Unlike Khovanov's original construction, our definition of the complex does not use any additional prescription of signs to the edges of a cube. Moreover, our method enables us to construct a Khovanov homology theory for 'twisted virtual knots' in the sense of Bourgoin and Viro (including knots in three-dimensional projective space). We generalize a number of results of Khovanov homology theory (the Wehrli complex, minimality problems, Frobenius extensions) to virtual knots with non-orientable atoms

  6. Appendicular knot causing closed-loop obstruction, volvulus and ...

    African Journals Online (AJOL)

    Keywords: appendix, appendicular tie/knot syndrome, intestinal obstruction, volvulus, strangulation .... possible contrast reaction and high cost) and its unavailability in some ... morbidity and mortality rise significantly with delay. In. Fevang's ...

  7. Topological effects on the mechanical properties of polymer knots

    Science.gov (United States)

    Zhao, Yani; Ferrari, Franco

    2017-11-01

    The mechanical properties of knotted polymer rings under stretching in a bad or good solvent are investigated by applying a force F to a point of the knot while keeping another point fixed. The Monte Carlo sampling of the polymer conformations is performed on a simple cubic lattice using the Wang-Landau algorithm. The specific energy, specific heat capacity, gyration radius and the force-elongation curves are computed for several knot topologies with lengths up to 120 lattice units. The common features of the mechanical and thermal behavior of stretched short polymer rings forming knots of a given topological type are analyzed as well as the differences arising due to topology and size effects. It is found that these systems admit three different phases depending on the values of the tensile force F and the temperature T. The transitions from one phase to the other are well characterized by the peaks of the specific heat capacity and by the data of the gyration radius and specific energy. At very low temperatures the force-elongation curves show that the stretching of a knot is a stepwise process, which becomes smooth at higher temperatures. Criteria for distinguishing topological and size effects are provided. It turns out from our study that the behavior of short polymer rings is strongly influenced by topological effects. In particular, the swelling and the swelling rate of knots are severely limited by the topological constraints. Several other properties that are affected by topology, like the decay of the specific energy at high tensile forces, are discussed. The fading out of the influences of topological origin with increasing knot lengths has been verified. Some anomalies detected in the plots of the specific heat capacity of very short and complex knots have been explained by the limitations in the number of accessible energy states due to the topological constraints.

  8. Hybrid Threat Center of Gravity Analysis: Cutting the Gordian Knot

    Science.gov (United States)

    2016-04-04

    19b. TELEPHONE NUMBER (Include area code) 04/04/2016 Master’s Thesis 22-7-2015 to 04-04-2016 HYBRID THREAT CENTER OF GRAVITY ANALYSIS: CUTTING THE...CENTER OF GRAVITY ANALYSIS: CUTTING THE GORDIAN KNOT By Michael D. Reilly LtCol, USMC Intentionally left blank...HYBRID THREAT CENTER OF GRAVITY ANALYSIS: CUTTING THE GORDIAN KNOT By Michael D. Reilly LtCol, USMC A paper submitted to the Faculty of the Joint Advanced

  9. Femtosecond laser ablation of enamel

    Science.gov (United States)

    Le, Quang-Tri; Bertrand, Caroline; Vilar, Rui

    2016-06-01

    The surface topographical, compositional, and structural modifications induced in human enamel by femtosecond laser ablation is studied. The laser treatments were performed using a Yb:KYW chirped-pulse-regenerative amplification laser system (560 fs and 1030 nm) and fluences up to 14 J/cm2. The ablation surfaces were studied by scanning electron microscopy, grazing incidence x-ray diffraction, and micro-Raman spectroscopy. Regardless of the fluence, the ablation surfaces were covered by a layer of resolidified material, indicating that ablation is accompanied by melting of hydroxyapatite. This layer presented pores and exploded gas bubbles, created by the release of gaseous decomposition products of hydroxyapatite (CO2 and H2O) within the liquid phase. In the specimen treated with 1-kHz repetition frequency and 14 J/cm2, thickness of the resolidified material is in the range of 300 to 900 nm. The micro-Raman analysis revealed that the resolidified material contains amorphous calcium phosphate, while grazing incidence x-ray diffraction analysis allowed detecting traces of a calcium phosphate other than hydroxyapatite, probably β-tricalcium phosphate Ca3), at the surface of this specimen. The present results show that the ablation of enamel involves melting of enamel's hydroxyapatite, but the thickness of the altered layer is very small and thermal damage of the remaining material is negligible.

  10. Knack knots you need step-by-step instructions for more than 100 of the best sailing, fishing, climbing, camping and decorative knots

    CERN Document Server

    Tilton, Buck

    2008-01-01

    Untie the mystery of knot-making with this clever and handy guide. This new compendium presents all the knots you need to know, with brightly colored photographs enabling you to easily follow the instructions. In addition, the book includes copious information on using knots in most popular activities. With its clear step-by-step instructions and friendly tone, this is the one volume you can count on to guide you toward quick success in knot-making.

  11. Probe Knots and Hopf Insulators with Ultracold Atoms

    Science.gov (United States)

    Deng, Dong-Ling; Wang, Sheng-Tao; Sun, Kai; Duan, L.-M.

    2018-01-01

    Knots and links are fascinating and intricate topological objects. Their influence spans from DNA and molecular chemistry to vortices in superfluid helium, defects in liquid crystals and cosmic strings in the early universe. Here we find that knotted structures also exist in a peculiar class of three-dimensional topological insulators—the Hopf insulators. In particular, we demonstrate that the momentum-space spin textures of Hopf insulators are twisted in a nontrivial way, which implies the presence of various knot and link structures. We further illustrate that the knots and nontrivial spin textures can be probed via standard time-of-flight images in cold atoms as preimage contours of spin orientations in stereographic coordinates. The extracted Hopf invariants, knots, and links are validated to be robust to typical experimental imperfections. Our work establishes the existence of knotted structures in Hopf insulators, which may have potential applications in spintronics and quantum information processing. D.L.D., S.T.W. and L.M.D. are supported by the ARL, the IARPA LogiQ program, and the AFOSR MURI program, and supported by Tsinghua University for their visits. K.S. acknowledges the support from NSF under Grant No. PHY1402971. D.L.D. is also supported by JQI-NSF-PFC and LPS-MPO-CMTC at the final stage of this paper.

  12. Energy, ropelength, and other physical aspects of equilateral knots

    International Nuclear Information System (INIS)

    Millett, Kenneth C.; Rawdon, Eric J.

    2003-01-01

    Closed macromolecular chains may form physically knotted conformations whose relative occurrence and spatial measurements provide insight into their properties and the mechanisms acting upon them. Under the assumption of a degree of structural homogeneity, equilateral spatial polygons are a productive context within which to create mathematical models of these knots and to study their mathematical and physical properties. The ensembles, or spaces, of these knots are models of the settings within which the knots evolve in ways determined by a physical model. In this paper we describe the mathematical foundation of such models as well as such spatial, geometric, statistical, and physical properties of the configurations as mathematical energies, thickness and ropelength, average crossing number, average writhe, and volumes and surfaces areas of standard bodies enclosing the knots. We present methods with which the energy and ropelength are optimized within the families of spatially equivalent equilateral configurations. Numerical results from our implementation of these methods are shown to illustrate connections between the physical measurements and spatial characteristics of the optimized knot configurations. In addition, these data suggest potentially new connections involving their spatial properties

  13. Quantitative study of fluoride transport during subsurface dissolution of dental enamel

    International Nuclear Information System (INIS)

    Chu, J.S.; Fox, J.L.; Higuchi, W.I.

    1989-01-01

    Previous studies using bovine dental enamel as a model have shown that surface and subsurface dissolution of enamel may be governed by micro-environmental solution conditions. We have now investigated the demineralization phenomenon more rigorously with the primary objective of developing a method for deducing solution species concentration profiles as a function of time from appropriate experimental data. More specifically, in this report, a model-independent method is described for determination of the pore solution fluoride gradients in bovine enamel during subsurface demineralization. Microradiography was used to determine the mineral density profiles, and an electron microprobe technique to determine total fluoride (F) profiles associated with the enamel. In each case, matched sections of bovine enamel were exposed to partially saturated acetate buffers at pH = 4.5 containing 0.5 ppm F for various periods of time (from six to 24 hours). The treated enamel was found to have an intact surface layer and subsurface demineralization. The extent of the demineralization and the depths of the lesions increased with time in all cases. The data were first used to calculate (a) the total F gradients in the enamel at various times, and (b) the local uptake rate of F as a function of time and position. Then, by manipulation of the equations describing the uptake and transport of F, we calculated the pore diffusion rate of F and the micro-environmental solution F concentration in the aqueous pores as a function of time and of distance from the enamel surface. It was also possible to calculate an intrinsic F diffusion coefficient in the pores, which was about 1.0 X 10(-5) cm2/sec, in good agreement with reported values

  14. Knots Untie: Molecular Determinants Involved in Knot Formation Induced by Pseudomonas savastanoi in Woody Hosts

    Directory of Open Access Journals (Sweden)

    Eloy Caballo-Ponce

    2017-06-01

    Full Text Available The study of the molecular basis of tree diseases is lately receiving a renewed attention, especially with the emerging perception that pathogens require specific pathogenicity and virulence factors to successfully colonize woody hosts. Pathosystems involving woody plants are notoriously difficult to study, although the use of model bacterial strains together with genetically homogeneous micropropagated plant material is providing a significant impetus to our understanding of the molecular determinants leading to disease. The gammaproteobacterium Pseudomonas savastanoi belongs to the intensively studied Pseudomonas syringae complex, and includes three pathogenic lineages causing tumorous overgrowths (knots in diverse economically relevant trees and shrubs. As it occurs with many other bacteria, pathogenicity of P. savastanoi is dependent on a type III secretion system, which is accompanied by a core set of at least 20 effector genes shared among strains isolated from olive, oleander, and ash. The induction of knots of wild-type size requires that the pathogen maintains adequate levels of diverse metabolites, including the phytohormones indole-3-acetic acid and cytokinins, as well as cyclic-di-GMP, some of which can also regulate the expression of other pathogenicity and virulence genes and participate in bacterial competitiveness. In a remarkable example of social networking, quorum sensing molecules allow for the communication among P. savastanoi and other members of the knot microbiome, while at the same time are essential for tumor formation. Additionally, a distinguishing feature of bacteria from the P. syringae complex isolated from woody organs is the possession of a 15 kb genomic island (WHOP carrying four operons and three other genes involved in degradation of phenolic compounds. Two of these operons mediate the catabolism of anthranilate and catechol and, together with another operon, are required for the induction of full-size tumors

  15. Role of Bending Energy and Knot Chirality in Knot Distribution and Their Effective Interaction along Stretched Semiflexible Polymers

    Directory of Open Access Journals (Sweden)

    Saeed Najafi

    2016-09-01

    Full Text Available Knots appear frequently in semiflexible (biopolymers, including double-stranded DNA, and their presence can affect the polymer’s physical and functional properties. In particular, it is possible and indeed often the case that multiple knots appear on a single chain, with effects which have only come under scrutiny in the last few years. In this manuscript, we study the interaction of two knots on a stretched semiflexible polymer, expanding some recent results on the topic. Specifically, we consider an idealization of a typical optical tweezers experiment and show how the bending rigidity of the chain—And consequently its persistence length—Influences the distribution of the entanglements; possibly more importantly, we observe and report how the relative chirality of the otherwise identical knots substantially modifies their interaction. We analyze the free energy of the chain and extract the effective interactions between embedded knots, rationalizing some of their pertinent features by means of simple effective models. We believe the salient aspect of the knot–knot interactions emerging from our study will be present in a large number of semiflexible polymers under tension, with important consequences for the characterization and manipulation of these systems—Be they artificial or biologica in origin—And for their technological application.

  16. Trapping a Knot into Tight Conformations by Intra-Chain Repulsions

    Directory of Open Access Journals (Sweden)

    Liang Dai

    2017-02-01

    Full Text Available Knots can occur in biopolymers such as DNA and peptides. In our previous study, we systematically investigated the effects of intra-chain interactions on knots and found that long-range repulsions can surprisingly tighten knots. Here, we use this knowledge to trap a knot into tight conformations in Langevin dynamics simulations. By trapping, we mean that the free energy landscape with respect to the knot size exhibits a potential well around a small knot size in the presence of long-range repulsions, and this potential can well lead to long-lived tight knots when its depth is comparable to or larger than thermal energy. We tune the strength of intra-chain repulsion such that a knot is weakly trapped. Driven by thermal fluctuations, the knot can escape from the trap and is then re-trapped. We find that the knot switches between tight and loose conformations—referred to as “knot breathing”. We use a Yukawa potential to model screened electrostatic interactions to explore the relevance of knot trapping and breathing in charged biopolymers. We determine the minimal screened length and the minimal strength of repulsion for knot trapping. We find that Coulomb-induced knot trapping is possible to occur in single-stranded DNA and peptides for normal ionic strengths.

  17. Knots, topology and quantum field theories

    International Nuclear Information System (INIS)

    Lusanna, L.

    1989-01-01

    The title of the workshop, Knots, Topology and Quantum Field Theory, accurate reflected the topics discussed. There have been important developments in mathematical and quantum field theory in the past few years, which had a large impact on physicist thinking. It is historically unusual and pleasing that these developments are taking place as a result of an intense interaction between mathematical physicists and mathematician. On the one hand, topological concepts and methods are playing an increasingly important lead to novel mathematical concepts: for instance, the study of quantum groups open a new chapter in the deformation theory of Lie algebras. These developments at present will lead to new insights into the theory of elementary particles and their interactions. In essence, the talks dealt with three, broadly defined areas of theoretical physics. One was topological quantum field theories, the other the problem of quantum groups and the third one certain aspects of more traditional field theories, such as, for instance, quantum gravity. These topics, however, are interrelated and the general theme of the workshop defies rigid classification; this was evident from the cross references to be found in almo all the talks

  18. Type IIB Ileosigmoid knotting: a case report

    Directory of Open Access Journals (Sweden)

    Ajak Makor

    2018-02-01

    Full Text Available Ileosigmoid knotting is a rare cause of acute intestinal obstruction. It is more common in Africans and Asians than in white populations and it is more prevalent in males than in females with a ratio of 14:1. It is classified into four types (I, II, III and IV with further extra two subtypes of A and B where type A is the most common presentation. Preoperative diagnosis is a challenge to the frontline doctors in the accidents and emergency departments; especially with limited diagnostic tools. Ultrasonography may be misleading in most of the cases due to the similarity of the disease with other causes of acute abdomen, especially acute appendicitis. Clinical presentation of an unprecedented intestinal obstruction with constant upper to mid-abdominal quadrant pain associated with mild to moderate abdominal distension contrary to the severe abdominal distension in sigmoid volvulus are the hallmarks that can help the surgical team to reach an accurate and early diagnosis preoperatively to avoid the devastating ischemia and gangrene in case of delay.

  19. Enamel Regeneration - Current Progress and Challenges

    Science.gov (United States)

    Baswaraj; H.K, Navin; K.B, Prasanna

    2014-01-01

    Dental Enamel is the outermost covering of teeth. It is hardest mineralized tissue present in the human body. Enamel faces the challenge of maintaining its integrity in a constant demineralization and remineralization within the oral environment and it is vulnerable to wear, damage, and decay. It cannot regenerate itself, because it is formed by a layer of cells that are lost after the tooth eruption. Conventional treatment relies on synthetic materials to restore lost enamel that cannot mimic natural enamel. With advances in material science and understanding of basic principles of organic matrix mediated mineralization paves a way for formation of synthetic enamel. The knowledge of enamel formation and understanding of protein interactions and their gene products function along with the isolation of postnatal stem cells from various sources in the oral cavity, and the development of smart materials for cell and growth factor delivery, makes possibility for biological based enamel regeneration. This article will review the recent endeavor on biomimetic synthesis and cell based strategies for enamel regeneration. PMID:25386548

  20. Comparison Of Bond Strength Of Orthodontic Molar Tubes Using Different Enamel Etching Techniques And Their Effect On Enamel

    International Nuclear Information System (INIS)

    Abd el Rahman, H.Y.

    2013-01-01

    In fixed orthodontic treatment, brackets and tubes are used for transferring orthodontic forces to the teeth. Those attachments were welded to cemented bands. Fifty years ago, direct bonding of brackets and other attachments has become a common technique in fixed orthodontic treatment. Orthodontists used to band teeth, especially molars and second premolars, to avoid the need for re bonding accessories in these regions of heavy masticatory forces. However, it is a known fact that direct bonding saves chair time as it does not require prior band selection and fitting, has the ability to maintain good oral hygiene, improve esthetics and make easier attachment to crowded and partially erupted teeth. Moreover, when the banding procedure is not performed with utmost care it can damage periodontal and/or dental tissues. Molar tubes bonding decreases the chance of decalcification caused by leakage beneath the bands. Since molar teeth are subjected to higher masticatory impact, especially lower molars, it would be convenient to devise methods capable of increasing the efficiency of their traditional bonding. These methods may include variation in bond able molar tube material, design, bonding materials and etching techniques. For achieving successful bonding, the bonding agent must penetrate the enamel surface; have easy clinical use, dimensional stability and enough bond strength. Different etching techniques were introduced in literature to increase the bond strength which includes: conventional acid etching, sandblasting and laser etching techniques. The process of conventional acid etching technique was invented In (1955) as the surface of enamel has great potential for bonding by micromechanical retention, to form ‘the mechanical lock‘. The primary effect of enamel etching is to increase the surface area. However, this roughens the enamel microscopically and results in a greater surface area on which to bond. By dissolving minerals in enamel, etchants remove the

  1. Accelerated enamel mineralization in Dspp mutant mice

    Science.gov (United States)

    Verdelis, Kostas; Szabo-Rogers, Heather L.; Xu, Yang; Chong, Rong; Kang, Ryan; Cusack, Brian J.; Jani, Priyam; Boskey, Adele L.; Qin, Chunlin; Beniash, Elia

    2016-01-01

    Dentin sialophosphoprotein (DSPP) is one of the major non-collagenous proteins present in dentin, cementum and alveolar bone; it is also transiently expressed by ameloblasts. In humans many mutations have been found in DSPP and are associated with two autosomal-dominant genetic diseases — dentinogenesis imperfecta II (DGI-II) and dentin dysplasia (DD). Both disorders result in the development of hypomineralized and mechanically compromised teeth. The erupted mature molars of Dspp–/– mice have a severe hypomineralized dentin phenotype. Since dentin and enamel formations are interdependent, we decided to investigate the process of enamel onset mineralization in young Dspp–/– animals. We focused our analysis on the constantly erupting mouse incisor, to capture all of the stages of odontogenesis in one tooth, and the unerupted first molars. Using high-resolution microCT, we revealed that the onset of enamel matrix deposition occurs closer to the cervical loop and both secretion and maturation of enamel are accelerated in Dspp–/– incisors compared to the Dspp+/– control. Importantly, these differences did not translate into major phenotypic differences in mature enamel in terms of the structural organization, mineral density or hardness. The only observable difference was the reduction in thickness of the outer enamel layer, while the total enamel thickness remained unchanged. We also observed a compromised dentin-enamel junction, leading to delamination between the dentin and enamel layers. The odontoblast processes were widened and lacked branching near the DEJ. Finally, for the first time we demonstrate expression of Dspp mRNA in secretory ameloblasts. In summary, our data show that DSPP is important for normal mineralization of both dentin and enamel. PMID:26780724

  2. In vitro wear of four ceramic materials and human enamel on enamel antagonist.

    Science.gov (United States)

    Nakashima, Jun; Taira, Yohsuke; Sawase, Takashi

    2016-06-01

    The purpose of the present study was to evaluate the wear of four different ceramics and human enamel. The ceramics used were lithium disilicate glass (e.max Press), leucite-reinforced glass (GN-Ceram), yttria-stabilized zirconia (Aadva Zr), and feldspathic porcelain (Porcelain AAA). Hemispherical styli were fabricated with these ceramics and with tooth enamel. Flattened enamel was used for antagonistic specimens. After 100,000 wear cycles of a two-body wear test, the height and volume losses of the styli and enamel antagonists were determined. The mean and standard deviation for eight specimens were calculated and statistically analyzed using a non-parametric (Steel-Dwass) test (α = 0.05). GN-Ceram exhibited greater stylus height and volume losses than did Porcelain AAA. E.max Press, Porcelain AAA, and enamel styli showed no significant differences, and Aadva Zr exhibited the smallest stylus height and volume losses. The wear of the enamel antagonist was not significantly different among GN-Ceram, e.max Press, Porcelain AAA, and enamel styli. Aadva Zr resulted in significantly lower wear values of the enamel antagonist than did GN-Ceram, Porcelain AAA, and enamel styli. In conclusion, leucite-reinforced glass, lithium disilicate glass, and feldspathic porcelain showed wear values closer to those for human enamel than did yttria-stabilized zirconia. © 2016 Eur J Oral Sci.

  3. Comparison of Enamel Morphologic Characteristics after Conditioning with Various Combinations of Acid Etchant and Er:YAG Laser in Bonding and Rebonding Procedures: A SEM Analysis

    Directory of Open Access Journals (Sweden)

    Mohammad Sadegh Ahmad Akhoundi

    2017-10-01

    Full Text Available Objectives: Many studies have evaluated re-etched enamel by using scanning electron microscopy (SEM; however, there is no evidence regarding the use of Erbium-doped yttrium aluminium garnet (Er:YAG laser at primary and secondary bonding instead of acid etching with regards to enamel surface changes. The purpose of the present study was to determine that whether or not the methods of primary and secondary enamel preparation affect enamel characteristics after rebonding, by using SEM analysis.Materials and Methods: Twelve freshly extracted premolars were divided into 4 groups. The samples in each group were conditioned by acid etchant or Er:YAG laser at primary conditioning, according to the instructions. Afterwards, they were bonded with orthodontic brackets. After debonding, the samples were prepared for second conditioning. Also, two samples were conditioned only once with acid etchant or laser, to compare enamel morphology changes with those after re-etching. Finally, buccal enamel surfaces were evaluated using SEM.Results: Enamel etching patterns were observed in the samples which had been acid-conditioned at first or at both conditionings. The samples irradiated by Er:YAG laser showed amorphous and irregular surfaces, with no signs of typical etching patterns. A large deep gap was seen in one of the samples irradiated with laser at primary and secondary conditionings, which might have penetrated the underling layers of enamel and dentin.Conclusions: Enamel surface preparation with Er:YAG laser produces irregular and indistinct morphologic changes, completely different from those produced after acid etching at both conditioning and reconditioning. Therefore, it is recommended to use this laser with caution to avoid permanent enamel damage.

  4. ON THE R-CURVE BEHAVIOR OF HUMAN TOOTH ENAMEL

    OpenAIRE

    Bajaj, Devendra; Arola, Dwayne

    2009-01-01

    In this study the crack growth resistance behavior and fracture toughness of human tooth enamel were quantified using incremental crack growth measures and conventional fracture mechanics. Results showed that enamel undergoes an increase in crack growth resistance (i.e. rising R-curve) with crack extension from the outer to the inner enamel, and that the rise in toughness is function of distance from the Dentin Enamel Junction (DEJ). The outer enamel exhibited the lowest apparent toughness (0...

  5. Regulation of Dental Enamel Shape and Hardness

    Science.gov (United States)

    Simmer, J.P.; Papagerakis, P.; Smith, C.E.; Fisher, D.C.; Rountrey, A.N.; Zheng, L.; Hu, J.C.-C.

    2010-01-01

    Epithelial-mesenchymal interactions guide tooth development through its early stages and establish the morphology of the dentin surface upon which enamel will be deposited. Starting with the onset of amelogenesis beneath the future cusp tips, the shape of the enamel layer covering the crown is determined by five growth parameters: the (1) appositional growth rate, (2) duration of appositional growth (at the cusp tip), (3) ameloblast extension rate, (4) duration of ameloblast extension, and (5) spreading rate of appositional termination. Appositional growth occurs at a mineralization front along the ameloblast distal membrane in which amorphous calcium phosphate (ACP) ribbons form and lengthen. The ACP ribbons convert into hydroxyapatite crystallites as the ribbons elongate. Appositional growth involves a secretory cycle that is reflected in a series of incremental lines. A potentially important function of enamel proteins is to ensure alignment of successive mineral increments on the tips of enamel ribbons deposited in the previous cycle, causing the crystallites to lengthen with each cycle. Enamel hardens in a maturation process that involves mineral deposition onto the sides of existing crystallites until they interlock with adjacent crystallites. Neutralization of acidity generated by hydroxyapatite formation is a key part of the mechanism. Here we review the growth parameters that determine the shape of the enamel crown as well as the mechanisms of enamel appositional growth and maturation. PMID:20675598

  6. Sectional meeting on Numerical Methods, Calculations and Simulations in Knot Theory and its Applications

    CERN Document Server

    Millett, Kenneth C; Rawdon, Eric J; Stasiak, Andrzej; Physical and Numerical Models in Knot theory: including Applications to the Life Sciences; Conference on Knots, Random Walks and Biomolecules

    2005-01-01

    The physical properties of knotted and linked configurations in space have long been of interest to mathematicians. More recently, these properties have become significant to biologists, physicists, and engineers among others. Their depth of importance and breadth of application are now widely appreciated and valuable progress continues to be made each year. This volume presents several contributions from researchers using computers to study problems that would otherwise be intractable. While computations have long been used to analyze problems, formulate conjectures, and search for special structures in knot theory, increased computational power has made them a staple in many facets of the field. The volume also includes contributions concentrating on models researchers use to understand knotting, linking, and entanglement in physical and biological systems. Topics include properties of knot invariants, knot tabulation, studies of hyperbolic structures, knot energies, the exploration of spaces of knots, knot...

  7. Classification of knotted tori in 2-metastable dimension

    KAUST Repository

    Cencelj, Matija

    2012-11-30

    This paper is devoted to the classical Knotting Problem: for a given manifold N and number m describe the set of isotopy classes of embeddings N → Sm. We study the specific case of knotted tori, that is, the embeddings Sp × Sq → Sm. The classification of knotted tori up to isotopy in the metastable dimension range m > p + 3 2 q + 2, p 6 q, was given by Haefliger, Zeeman and A. Skopenkov. We consider the dimensions below the metastable range and give an explicit criterion for the finiteness of this set of isotopy classes in the 2-metastable dimension: Theorem. Assume that p+ 4 3 q +2 < mp+ 3 2 q +2 and m > 2p+q +2. Then the set of isotopy classes of smooth embeddings Sp × Sq → Sm is infinite if and only if either q + 1 or p + q + 1 is divisible by 4. © 2012 RAS(DoM) and LMS.

  8. Classification of knotted tori in 2-metastable dimension

    KAUST Repository

    Cencelj, Matija; Repovš, Dušan; Skopenkov, Mikhail

    2012-01-01

    This paper is devoted to the classical Knotting Problem: for a given manifold N and number m describe the set of isotopy classes of embeddings N → Sm. We study the specific case of knotted tori, that is, the embeddings Sp × Sq → Sm. The classification of knotted tori up to isotopy in the metastable dimension range m > p + 3 2 q + 2, p 6 q, was given by Haefliger, Zeeman and A. Skopenkov. We consider the dimensions below the metastable range and give an explicit criterion for the finiteness of this set of isotopy classes in the 2-metastable dimension: Theorem. Assume that p+ 4 3 q +2 < mp+ 3 2 q +2 and m > 2p+q +2. Then the set of isotopy classes of smooth embeddings Sp × Sq → Sm is infinite if and only if either q + 1 or p + q + 1 is divisible by 4. © 2012 RAS(DoM) and LMS.

  9. Weaker dental enamel explains dental decay.

    Science.gov (United States)

    Vieira, Alexandre R; Gibson, Carolyn W; Deeley, Kathleen; Xue, Hui; Li, Yong

    2015-01-01

    Dental caries continues to be the most prevalent bacteria-mediated non-contagious disease of humankind. Dental professionals assert the disease can be explained by poor oral hygiene and a diet rich in sugars but this does not account for caries free individuals exposed to the same risk factors. In order to test the hypothesis that amount of amelogenin during enamel development can influence caries susceptibility, we generated multiple strains of mice with varying levels of available amelogenin during dental development. Mechanical tests showed that dental enamel developed with less amelogenin is "weaker" while the dental enamel of animals over-expressing amelogenin appears to be more resistant to acid dissolution.

  10. Knots and Random Walks in Vibrated Granular Chains

    International Nuclear Information System (INIS)

    Ben-Naim, E.; Daya, Z. A.; Vorobieff, P.; Ecke, R. E.

    2001-01-01

    We study experimentally statistical properties of the opening times of knots in vertically vibrated granular chains. Our measurements are in good qualitative and quantitative agreement with a theoretical model involving three random walks interacting via hard-core exclusion in one spatial dimension. In particular, the knot survival probability follows a universal scaling function which is independent of the chain length, with a corresponding diffusive characteristic time scale. Both the large-exit-time and the small-exit-time tails of the distribution are suppressed exponentially, and the corresponding decay coefficients are in excellent agreement with theoretical values

  11. MMP20 Promotes a Smooth Enamel Surface, a Strong DEJ, and a Decussating Enamel Rod Pattern

    Science.gov (United States)

    Bartlett, John D.; Skobe, Ziedonis; Nanci, Antonio; Smith, Charles E.

    2012-01-01

    Mutations of the Matrix metalloproteinase-20 (MMP20, enamelysin) gene cause autosomal recessive amelogenesis imperfecta and Mmp20 ablated mice also have malformed dental enamel. Here we show that Mmp20 null mouse secretory stage ameloblasts maintained a columnar shape and were present as a single layer of cells. However, the null maturation stage ameloblasts covered extraneous nodules of ectopic calcified material formed at the enamel surface. Remarkably, nodule formation occurs in null mouse enamel when MMP20 is normally no longer expressed. The malformed enamel in Mmp20 null teeth was loosely attached to the dentin and the entire enamel layer tended to separate from the dentin indicative of a faulty DEJ. The enamel rod pattern was also altered in Mmp20 null mice. Each enamel rod is formed by a single ameloblast and is a mineralized record of the migration path of the ameloblast that formed it. The Mmp20 null mouse enamel rods were grossly malformed or were absent indicating that the ameloblasts do not migrate properly when backing away from the DEJ. Thus, MMP20 is required for ameloblast cell movement necessary to form the decussating enamel rod patterns, for the prevention of ectopic mineral formation, and to maintain a functional DEJ. PMID:22243247

  12. An investigation on the crack growth resistance of human tooth enamel: Anisotropy, microstructure and toughening

    Science.gov (United States)

    Yahyazadehfar, Mobin

    The enamel of human teeth is generally regarded as a brittle material with low fracture toughness. Consequently, the contributions of this tissue in resisting tooth fracture and the importance of its complex microstructure have been largely overlooked. The primary objective of this dissertation is to characterize the role of enamel's microstructure and degree of decussation on the fracture behavior of human enamel. The importance of the protein content and aging on the fracture toughness of enamel were also explored. Incremental crack growth in sections of human enamel was achieved using a special inset Compact Tension (CT) specimen configuration. Crack extension was achieved in two orthogonal directions, i.e. longitudinal and transverse to the prism axes. Fracture surfaces and the path of crack growth path were evaluated using scanning electron microscopy (SEM) to understand the fundamental mechanisms of crack growth extension. Furthermore, a hybrid approach was adopted to quantify the contribution of toughening mechanisms to the overall toughness. Results of this investigations showed that human enamel exhibits rising R-curve for both directions of crack extension. Cracks extending transverse to the rods in the outer enamel achieved lower rise in toughness with crack extension, and significantly lower toughness (1.23 +/- 0.20 MPa·m 0.5) than in the inner enamel (1.96 +/- 0.28 MPa· 0.5) and in the longitudinal direction (2.01 +/- 0.21 MPa· 0.5). The crack growth resistance exhibited both anisotropy and inhomogeneity, which arise from the complex hierarchical microstructure and the decussated prism structure. Decussation causes deflection of cracks extending from the enamel surface inwards, and facilitates a continuation of transverse crack extension within the outer enamel. This process dissipates fracture energy and averts cracks from extending toward the dentin and vital pulp. This study is the first to investigate the importance of proteins and the effect of

  13. Successful Treatment of Stent Knot in the Proximal Ureter Using Ureteroscopy and Holmium Laser

    Directory of Open Access Journals (Sweden)

    Masters M. Richards

    2011-01-01

    Full Text Available Knotted ureteral stent is rare yet tedious complication that might represent a treatment challenge to the endourologist. Only twelve cases of knotted stent have been reported. Different management options have been reported, including simple traction, ureteroscopy, percutaneous removal, and open surgery. In this paper, we present the successful untying of the knot using ureteroscopy with holmium laser.

  14. Caries prevalence and enamel defects in 5- and 10-year-old children with cleft lip and/or palate

    DEFF Research Database (Denmark)

    Sundell, Anna Lena; Nilsson, Anna-Karin; Ullbro, Christer

    2016-01-01

    OBJECTIVE: To determine the prevalence of dental caries and enamel defects in 5- and 10-year-old Swedish children with cleft lip and/or palate (CL(P)) in comparison to non-cleft controls. MATERIALS AND METHODS: The study group consisted of 139 children with CL(P) (80 subjects aged 5 years and 59...... aged 10 years) and 313 age-matched non-cleft controls. All children were examined by one of two calibrated examiners. Caries was scored according to the International Caries Detection and Assessment System (ICDAS-II) and enamel defects as presence and frequency of hypoplasia and hypomineralization...... prevalence of enamel defects was found in CL(P) children of both age groups and anterior permanent teeth were most commonly affected. CONCLUSIONS: Preschool children with cleft lip and/or palate seem to have more caries in the primary dentition than age-matched non-cleft controls. Enamel defects were more...

  15. Oral aspects in celiac disease children: clinical and dental enamel chemical evaluation.

    Science.gov (United States)

    de Carvalho, Fabrício Kitazono; de Queiroz, Alexandra Mussolino; Bezerra da Silva, Raquel Assed; Sawamura, Regina; Bachmann, Luciano; Bezerra da Silva, Léa Assed; Nelson-Filho, Paulo

    2015-06-01

    The aim of this study was to evaluate the oral manifestations of celiac disease (CD), the chemical composition of dental enamel, and the occurrence of CD in children with dental enamel defects (DEDs). In the study, 52 children with CD and 52 controls were examined for DEDs, recurrent aphthous stomatitis (RAS), dental caries experience, and salivary parameters. In addition, 10 exfoliated primary enamel molars from each group were analyzed by energy dispersive x-ray spectroscopy and Fourier transform infrared spectroscopy. Fifty children with DEDs were submitted to CD diagnosis. Among the children with CD, a higher prevalence of DEDs (P = .00001) and RAS (P = .0052), lower caries experience (P = .0024), and reduction of salivary flow (P = .0060) were observed. Dental enamel from the children with CD demonstrated a lower calcium-to-phosphorus ratio (P = .0136), but no difference in the carbonate-to-phosphate ratio (P = .5862) was observed. In the multivariate analysis, CD was a protective factor for caries (OR = 0.74) and a risk factor for RAS (OR3.23). The children with CD presented with more RAS, DEDs, reduction of salivary flow, and chemical alterations in the enamel. Copyright © 2015 Elsevier Inc. All rights reserved.

  16. Dental enamel, fluorosis and amoxicillin

    Directory of Open Access Journals (Sweden)

    I. Ciarrocchi

    2012-06-01

    Full Text Available Introduction: Amoxicillin is one of the most used antibiotics among pediatric patients for the treatment of upper respiratory tract infections and specially for acute otitis media (AOM, a common diseases of infants and childhood. It has been speculated that the use of amoxicillin during early childhood could be associated with dental enamel fluorosis, also described in literature with the term Molar Incisor Hypomineralization (MIH, because they are generally situated in one or more 1st permanent molars and less frequently in the incisors. The effect of Amoxicillin seems to be independent of other risk factors such as fluoride intake, prematurity, hypoxia, hypocalcaemia, exposure to dioxins, chikenpox, otitis media, high fever and could have a significant impact on oral health for the wide use of this drug in that period of life. Objective: The aim of this work was to review the current literature about the association between amoxicillin and fluorosis. Methods and Results: A literature survey was done by applying the Medline database (Entrez PubMed; the Cochrane Library database of the Cochrane Collaboration (CENTRAL. The databases were searched using the following strategy and keywords: amoxicillin* AND (dental fluorosis* OR dental enamel* AND MIH*. After selecting the studies, only three relevant articles published between 1966 and 2011 were included in the review. Conclusion: The presence of several methodological issues does not allow to draw any evidence-based conclusions. No evidence of association was detected, therefore, there is a need of further well-designed studies to assess the scientific evidence of the relationship between amoxicillin and fluorosis and to restrict the prescription of this drug for recurrent upper respiratory tract infections especially acute otitis media (AOM during the first two years of life. When it is possible can be opportune to use an alternative antibiotic treatment.

  17. Enamel micromorphology of the tribosphenic molar

    OpenAIRE

    Hanousková, Pavla

    2014-01-01

    The tribosphenic molar is an ancestral type of mammalian teeth and a phy- lotypic stage of the mammalian dental evolution. Yet, in contrast to derived teeth types, its enamel microarchitecture attracted only little attention and the information on that subject is often restricted to statements suggesting a simple homogenous arrangement of a primitive radial prismatic enamel. The present paper tests this prediction with aid of comparative study of eight model species representing the orders Ch...

  18. EPR dosimetry with tooth enamel: A review

    International Nuclear Information System (INIS)

    Fattibene, Paola; Callens, Freddy

    2010-01-01

    When tooth enamel is exposed to ionizing radiation, radicals are formed, which can be detected using electron paramagnetic resonance (EPR) techniques. EPR dosimetry using tooth enamel is based on the (presumed) correlation between the intensity or amplitude of some of the radiation-induced signals with the dose absorbed in the enamel. In the present paper a critical review is given of this widely applied dosimetric method. The first part of the paper is fairly fundamental and deals with the main properties of tooth enamel and some of its model systems (e.g., synthetic apatites). Considerable attention is also paid to the numerous radiation-induced and native EPR signals and the radicals responsible for them. The relevant methods for EPR detection, identification and spectrum analyzing are reviewed from a general point of view. Finally, the needs for solid-state modelling and studies of the linearity of the dose response are investigated. The second part is devoted to the practical implementation of EPR dosimetry using enamel. It concerns specific problems of preparation of samples, their irradiation and spectrum acquisition. It also describes how the dosimetric signal intensity and dose can be retrieved from the EPR spectra. Special attention is paid to the energy dependence of the EPR response and to sources of uncertainties. Results of and problems encountered in international intercomparisons and epidemiological studies are also dealt with. In the final section the future of EPR dosimetry with tooth enamel is analyzed.

  19. Measurement of opalescence of tooth enamel.

    Science.gov (United States)

    Lee, Yong-Keun; Yu, Bin

    2007-08-01

    Opalescent dental esthetic restoratives look natural and esthetic in any light, react to light in the same manner as the natural tooth and show improved masking effect. The objective of this study was to determine the opalescence of tooth enamel with reflection spectrophotometers. Color of intact bovine and human enamel was measured in the reflectance and transmittance modes. Two kinds of spectrophotometers were used for bovine and one kind was used for human enamel. The opalescence parameter (OP) was calculated as the difference in yellow-blue color coordinate (CIE Deltab(*)) and red-green color coordinate (CIE Deltaa(*)) between the reflected and transmitted colors. Mean OP value of bovine enamel was 10.6 (+/-1.4) to 19.0 (+/-2.1), and varied by the configuration of spectrophotometers. Mean OP value of human enamel was 22.9 (+/-1.9). Opalescence varied by the configuration of measuring spectrophotometer and the species of enamel. These values could be used in the development of esthetic restorative materials.

  20. True Umbilical Cord Knot Leading to Fetal Demise

    African Journals Online (AJOL)

    weight was 140 kg, height 1.69 m, blood pressure 120 mmHg. The booking ... The fetal heart tones were monitored using Doppler sonicaid. They remained normal throughout .... true knot, seemingly because the umbilical cord vessels can be compressed ... Therefore, the Wharton's jelly surrounding the fetal vessels has the ...

  1. The multivariable Alexander polynomial and modern knot theory

    International Nuclear Information System (INIS)

    Saleur, H.; Yale Univ., New Haven, CT

    1991-01-01

    This note is a summary of several recent works (by the author and collaborators) that study the Conway Alexander link invariant in the light of quantum groups and topological quantum field theories. Their purpose is to understand connections between ''modern'' knot theory and more classical topological concepts. (author)

  2. The multivariable Alexander polynomial and modern knot theory

    International Nuclear Information System (INIS)

    Saleur, H.

    1992-01-01

    This paper is a summary of several recent works (by the author and collaborators) that study the Conway-Alexander link invariant in the light of quantum groups and topological quantum field theories. Their purpose is to understand connections between modern knot theory and more classical topological concepts

  3. The unique cysteine knot regulates the pleotropic hormone leptin.

    Directory of Open Access Journals (Sweden)

    Ellinor Haglund

    Full Text Available Leptin plays a key role in regulating energy intake/expenditure, metabolism and hypertension. It folds into a four-helix bundle that binds to the extracellular receptor to initiate signaling. Our work on leptin revealed a hidden complexity in the formation of a previously un-described, cysteine-knotted topology in leptin. We hypothesized that this unique topology could offer new mechanisms in regulating the protein activity. A combination of in silico simulation and in vitro experiments was used to probe the role of the knotted topology introduced by the disulphide-bridge on leptin folding and function. Our results surprisingly show that the free energy landscape is conserved between knotted and unknotted protein, however the additional complexity added by the knot formation is structurally important. Native state analyses led to the discovery that the disulphide-bond plays an important role in receptor binding and thus mediate biological activity by local motions on distal receptor-binding sites, far removed from the disulphide-bridge. Thus, the disulphide-bridge appears to function as a point of tension that allows dissipation of stress at a distance in leptin.

  4. Spontaneous knot; a rare cause of ventriculoperitoneal shunt blockage.

    LENUS (Irish Health Repository)

    Mohammed, Wail

    2011-02-01

    A 14-year old X linked congenital hydrocephalus presented with unexplained headaches and vomiting. He had external ventricular drain and intracranial pressure monitoring (ICP). Subsequently, he underwent exploration and removal of previously inserted ventriculoperitoneal (VP) shunts. On retrieval of peritoneal catheters a double knot was noted between his two distal catheters. This case illustrates a rare cause of ventriculoperitoneal shunt malfunction.

  5. Spontaneous knot; a rare cause of ventriculoperitoneal shunt blockage.

    LENUS (Irish Health Repository)

    Mohammed, Wail

    2012-02-01

    A 14-year old X linked congenital hydrocephalus presented with unexplained headaches and vomiting. He had external ventricular drain and intracranial pressure monitoring (ICP). Subsequently, he underwent exploration and removal of previously inserted ventriculoperitoneal (VP) shunts. On retrieval of peritoneal catheters a double knot was noted between his two distal catheters. This case illustrates a rare cause of ventriculoperitoneal shunt malfunction.

  6. Braid group, knot theory and statistical mechanics II

    CERN Document Server

    Yang Chen Ning

    1994-01-01

    The present volume is an updated version of the book edited by C N Yang and M L Ge on the topics of braid groups and knot theory, which are related to statistical mechanics. This book is based on the 1989 volume but has new material included and new contributors.

  7. Prevalence, incidence and molecular identification of root-knot ...

    African Journals Online (AJOL)

    Tomato is a widely grown vegetable in Pakistan. However, its production is severely constrained by root knot nematodes (RKNs). Accurate identification of RKNs is essential for an appropriate control program. The current study evaluated the prevalence, incidence and diversity of RKNs of tomato crops grown in the Khyber ...

  8. Sealing ability and bond strength of four contemporary adhesives to enamel and to dentine.

    Science.gov (United States)

    Atash, R; Vanden Abbeele, A

    2005-12-01

    To compare the shear bond strength and microleakage of four adhesive systems to the enamel and dentine of primary bovine teeth. 120 bovine primary mandibular incisors were collected and stored in an aqueous 1% chloramine solution at room temperature for no longer than 3 months after extraction (80 for shear bond testing and 40 for microleakage evaluation). The adhesives tested were Clearfil SE bond (SE), Adper Prompt L Pop (LP), Xeno III (XE), and Prime and Bond NT (PB). For shear bond strength testing the specimens were wet ground to 600 grit SiC paper to expose a flat enamel or dentine surface. After bonding and restoration with Dyract AP (DAP), the teeth were subjected to shear stress using a universal testing machine. For microleakage evaluation, facial class V cavities were prepared half in enamel and half in cementum. All cavities were restored with DAP. After thermocycling and immersion in 2% methylene blue, the dye penetration was evaluated under a stereomicroscope. All data were analysed by Chi-square tests or Fisher's tests when adapted in order to determine the significant differences between groups. Results were considered as significant for p enamel 11.06 to 5.34, in decreasing order SE, LP, XE and PB and on dentine 10.47 to 4.74, in decreasing order SE, XE, LP and PB. Differences in bond strengths between the four systems on enamel and dentine were all statistically significant, excepted for XE vs LP (shear bond at dentine). No significant differences were recorded in the microleakage degree between the four adhesive systems on enamel and on dentine (p > 0.0.5). The highest shear bond strength was achieved by Clearfil SE bond and the lowest by Prime and Bond NT. There was no significant difference concerning the sealing ability of the four adhesive systems.

  9. Filtration of the classical knot concordance group and Casson-Gordon invariants

    OpenAIRE

    Kim, Taehee

    2002-01-01

    It is known that if any prime power branched cyclic cover of a knot in the 3-sphere is a homology sphere, then the knot has vanishing Casson-Gordon invariants. We construct infinitely many examples of (topologically) non-slice knots in the 3-sphere whose prime power branched cyclic covers are homology spheres. We show that these knots generate an infinite rank subgroup of F_(1.0)/F_(1.5) for which Casson-Gordon invariants vanish in Cochran-Orr-Teichner's filtration of the classical knot conco...

  10. Comparative evaluation of enamel abrasivity of different commercially available dentifrices – An In vitro Study

    Directory of Open Access Journals (Sweden)

    Rupali Athawale

    2018-01-01

    Full Text Available Background: Toothbrushing with toothpaste is a major contributor to dental abrasion. A number of factors such as abrasivity and concentration of the toothpaste, brushing frequency, brushing duration, force of brushing, and toothbrush bristle stiffness have a potential impact on the abrasion process of dental hard tissue. However, the abrasivity of the toothpaste is the most important parameter that affects the abrasion process of dental hard tissue. Aims: This study aims to evaluate the maximum and mean enamel abrasivity of commercially available dentifrices such as Colgate total®, Pepsodent whitening®, Vicco vajradanti®, Dabur red® in primary and permanent teeth. Materials and Methods: Human extracted 60 primary and 60 permanent teeth were randomly selected based on the inclusion criteria. Teeth were sectioned at cementoenamel junction using diamond disc and mounted in an acrylic resin blocks. Baseline profilometric measurements were recorded for all the samples. Four commonly used dentifrices were selected and labeled as Group A (Colgate Total®, B (Pepsodent Whitening®, C (Vicco Vajradanti®, and D (Dabur Red®. Toothpaste slurry was prepared. Tooth specimens were brushed in vitro using a customized brushing machine. After toothbrushing, profilometric measurements were obtained, and the differences in readings served as proxy measure to assess surface abrasion. Data were collected and analyzed using student t-test and ANOVA test. Student t-test was used to compare the enamel abrasivity prebrushing and postbrushing, and ANOVA was used to compare the enamel abrasivity among the four different commercially available toothpastes. Results: In permanent teeth, all the toothpastes were found to cause significant enamel abrasion (P = 0.000 and a significant variation was observed when maximum (P = 0.008 and mean (P = 0.036 enamel abrasivity of these toothpastes were compared. In primary teeth also, all the toothpastes caused significant abrasion

  11. Type IIB Ileosigmoid knotting: a case report

    African Journals Online (AJOL)

    2016-06-03

    Jun 3, 2016 ... peritonitis [4,6,7]; hence early diagnosis and operative ... clinical and radiological presentation of type II ileosigmoid volvulus ... Emergency laparotomy with possible resection and primary anastomosis in type I or resection and ...

  12. Scaling behavior of knotted random polygons and self-avoiding polygons: Topological swelling with enhanced exponent.

    Science.gov (United States)

    Uehara, Erica; Deguchi, Tetsuo

    2017-12-07

    We show that the average size of self-avoiding polygons (SAPs) with a fixed knot is much larger than that of no topological constraint if the excluded volume is small and the number of segments is large. We call it topological swelling. We argue an "enhancement" of the scaling exponent for random polygons with a fixed knot. We study them systematically through SAP consisting of hard cylindrical segments with various different values of the radius of segments. Here we mean by the average size the mean-square radius of gyration. Furthermore, we show numerically that the topological balance length of a composite knot is given by the sum of those of all constituent prime knots. Here we define the topological balance length of a knot by such a number of segments that topological entropic repulsions are balanced with the knot complexity in the average size. The additivity suggests the local knot picture.

  13. An in vitro investigation of human enamel wear by restorative dental materials

    International Nuclear Information System (INIS)

    Adachi, L.K.; Saiki, M.; De Campos, T.N.

    2001-01-01

    A radiometric method was applied to asses enamel wear by another enamel and by restorative materials. The radioactive enamel was submitted to wear in a machine which allows sliding motion of an antagonistic surface in contact with the radioactive enamel. The enamel wear was evaluated by measuring the beta-activity of 32 P transferred to water from this irradiated tooth. Results obtained indicated that dental porcelains cause pronounced enamel wear when compared with that provoked by another natural enamel or by resin materials. Resin materials caused less enamel wear than another natural enamel. Vickers microhardness data obtained for antagonistic materials showed a correlation with the wear caused to the enamel. (author)

  14. Dental enamel defect diagnosis through different technology-based devices.

    Science.gov (United States)

    Kobayashi, Tatiana Yuriko; Vitor, Luciana Lourenço Ribeiro; Carrara, Cleide Felício Carvalho; Silva, Thiago Cruvinel; Rios, Daniela; Machado, Maria Aparecida Andrade Moreira; Oliveira, Thais Marchini

    2018-06-01

    Dental enamel defects (DEDs) are faulty or deficient enamel formations of primary and permanent teeth. Changes during tooth development result in hypoplasia (a quantitative defect) and/or hypomineralisation (a qualitative defect). To compare technology-based diagnostic methods for detecting DEDs. Two-hundred and nine dental surfaces of anterior permanent teeth were selected in patients, 6-11 years of age, with cleft lip with/without cleft palate. First, a conventional clinical examination was conducted according to the modified Developmental Defects of Enamel Index (DDE Index). Dental surfaces were evaluated using an operating microscope and a fluorescence-based device. Interexaminer reproducibility was determined using the kappa test. To compare groups, McNemar's test was used. Cramer's V test was used for comparing the distribution of index codes obtained after classification of all dental surfaces. Cramer's V test revealed statistically significant differences (P < .0001) in the distribution of index codes obtained using the different methods; the coefficients were 0.365 for conventional clinical examination versus fluorescence, 0.961 for conventional clinical examination versus operating microscope and 0.358 for operating microscope versus fluorescence. The sensitivity of the operating microscope and fluorescence method was statistically significant (P = .008 and P < .0001, respectively). Otherwise, the results did not show statistically significant differences in accuracy and specificity for either the operating microscope or the fluorescence methods. This study suggests that the operating microscope performed better than the fluorescence-based device and could be an auxiliary method for the detection of DEDs. © 2017 FDI World Dental Federation.

  15. Diffusion of fluoride in bovine enamel

    International Nuclear Information System (INIS)

    Flim, G.J.; Arends, J.; Kolar, Z.

    1976-01-01

    The uptake of 18 F and the penetration of both F and 18 F in bovine enamel was investigated. Sodium fluoride solutions buffered at pH 7 were employed. The uptake of 18 F was measured by a method described by R. Duckworth and M. Braden, Archs. Oral. Biol., 12(1967), pp. 217-230. The penetration concentration profiles of fluoride (F, 18 F) in the enamel were measured by a sectioning technique. The 18 F uptake in enamel was proportional to approximately tsup(3/4); t being the uptake time. The 18 F concentration as a function of the position in the enamel can be described by: c*(x,t) = c 0 *(t)exp[-α*(t)x]. After correction for the initial fluoride concentration in enamel, for unlabelled fluoride the same dependency is obtained. A model based on simultaneous diffusion and chemical reaction in the pores and diffusion into the hydroxyapatite crystallites will be presented. The results show that diffusion coefficients of the pores are approximately equal to 10 -10 cm 2 s -1 and in the apatite crystallites approximately equal to 10 -17 cm 2 s -1 . The limitations and the approximations of the model are discussed

  16. The fracture behaviour of dental enamel.

    Science.gov (United States)

    Bechtle, Sabine; Habelitz, Stefan; Klocke, Arndt; Fett, Theo; Schneider, Gerold A

    2010-01-01

    Enamel is the hardest tissue in the human body covering the crowns of teeth. Whereas the underlying dental material dentin is very well characterized in terms of mechanical and fracture properties, available data for enamel are quite limited and are apart from the most recent investigation mainly based on indentation studies. Within the current study, stable crack-growth experiments in bovine enamel have been performed, to measure fracture resistance curves for enamel. Single edge notched bending specimens (SENB) prepared out of bovine incisors were tested in 3-point bending and subsequently analysed using optical and environmental scanning electron microscopy. Cracks propagated primarily within the protein-rich rod sheaths and crack propagation occurred under an inclined angle to initial notch direction not only due to enamel rod and hydroxyapatite crystallite orientation but potentially also due to protein shearing. Determined mode I fracture resistance curves ranged from 0.8-1.5 MPa*m(1/2) at the beginning of crack propagation up to 4.4 MPa*m(1/2) at 500 microm crack extension; corresponding mode II values ranged from 0.3 to 1.5 MPa*m(1/2).

  17. Trace Elements in Human Tooth Enamel

    Energy Technology Data Exchange (ETDEWEB)

    Nixon, G. S. [Turner Dental School, University Of Manchester, Manchester (United Kingdom); Smith, H.; Livingston, H. D. [Department of Forensic Medicine, University Of Glasgow, Glasgow (United Kingdom)

    1967-10-15

    The trace elements are considered to play a role in the resistance of teeth to dental caries. The exact mechanism by which they act has not yet been fully established. Estimations of trace elements have been undertaken in sound human teeth. By means of activation analysis it has been possible to determine trace element concentrations in different layers of enamel in the same tooth. The concentrations of the following elements have been determined: arsenic, antimony, copper, zinc, manganese, mercury, molybdenum and vanadium. The distribution of trace elements in enamel varies from those with a narrow range, such as manganese, to those with a broad range, such as antimony. The elements present in the broad range are considered to be non-essential and their presence is thought to result from a chance incorporation into the enamel. Those in the narrow range appear to be essential trace elements and are present in amounts which do not vary unduly from other body tissues. Only manganese and zinc were found in higher concentrations in the surface layer of enamel compared with the inner layers. The importance of the concentration of trace elements on this surface layer of enamel is emphasized as this layer is the site of the first attack by the carious process. (author)

  18. Morphology of the cemento-enamel junction in premolar teeth.

    Science.gov (United States)

    Arambawatta, Kapila; Peiris, Roshan; Nanayakkara, Deepthi

    2009-12-01

    The present study attempted to describe the distribution of the mineralized tissues that compose the cemento-enamel junction, with respect to both the different types of permanent premolars of males and females and the various surfaces of individual teeth. The cervical region of ground sections of 67 premolars that had been extracted for orthodontic reasons were analyzed using transmitted light microscopy to identify which of the following tissue interrelationships was present at the cemento-enamel junction: cementum overlapping enamel; enamel overlapping cementum; edge-to-edge relationship between cementum and enamel; or the presence of gaps between the enamel and cementum with exposed dentin. An edge-to-edge interrelation between root cementum and enamel was predominant (55.1%). In approximately one-third of the sample, gaps between cementum and enamel with exposed dentin were observed. Cementum overlapping enamel was less prevalent than previously reported, and enamel overlapping cementum was seen in a very small proportion of the sample. In any one tooth, the distribution of mineralized tissues at the cemento-enamel junction was irregular and unpredictable. The frequency of gaps between enamel and cementum with exposure of dentin was higher than previously reported, which suggests that this region is fragile and strongly predisposed to pathological changes. Hence, this region should be protected and carefully managed during routine clinical procedures such as dental bleaching, orthodontic treatment, and placement of restorative materials.

  19. Finite element analysis of the cyclic indentation of bilayer enamel

    International Nuclear Information System (INIS)

    Jia, Yunfei; Xuan, Fu-zhen; Chen, Xiaoping; Yang, Fuqian

    2014-01-01

    Tooth enamel is often subjected to repeated contact and often experiences contact deformation in daily life. The mechanical strength of the enamel determines the biofunctionality of the tooth. Considering the variation of the rod arrangement in outer and inner enamel, we approximate enamel as a bilayer structure and perform finite element analysis of the cyclic indentation of the bilayer structure, to mimic the repeated contact of enamel during mastication. The dynamic deformation behaviour of both the inner enamel and the bilayer enamel is examined. The material parameters of the inner and outer enamel used in the analysis are obtained by fitting the finite element results with the experimental nanoindentation results. The penetration depth per cycle at the quasi-steady state is used to describe the depth propagation speed, which exhibits a two-stage power-law dependence on the maximum indentation load and the amplitude of the cyclic load, respectively. The continuous penetration of the indenter reflects the propagation of the plastic zone during cyclic indentation, which is related to the energy dissipation. The outer enamel serves as a protective layer due to its great resistance to contact deformation in comparison to the inner enamel. The larger equivalent plastic strain and lower stresses in the inner enamel during cyclic indentation, as calculated from the finite element analysis, indicate better crack/fracture resistance of the inner enamel. (paper)

  20. Finite element analysis of the cyclic indentation of bilayer enamel

    Science.gov (United States)

    Jia, Yunfei; Xuan, Fu-zhen; Chen, Xiaoping; Yang, Fuqian

    2014-04-01

    Tooth enamel is often subjected to repeated contact and often experiences contact deformation in daily life. The mechanical strength of the enamel determines the biofunctionality of the tooth. Considering the variation of the rod arrangement in outer and inner enamel, we approximate enamel as a bilayer structure and perform finite element analysis of the cyclic indentation of the bilayer structure, to mimic the repeated contact of enamel during mastication. The dynamic deformation behaviour of both the inner enamel and the bilayer enamel is examined. The material parameters of the inner and outer enamel used in the analysis are obtained by fitting the finite element results with the experimental nanoindentation results. The penetration depth per cycle at the quasi-steady state is used to describe the depth propagation speed, which exhibits a two-stage power-law dependence on the maximum indentation load and the amplitude of the cyclic load, respectively. The continuous penetration of the indenter reflects the propagation of the plastic zone during cyclic indentation, which is related to the energy dissipation. The outer enamel serves as a protective layer due to its great resistance to contact deformation in comparison to the inner enamel. The larger equivalent plastic strain and lower stresses in the inner enamel during cyclic indentation, as calculated from the finite element analysis, indicate better crack/fracture resistance of the inner enamel.

  1. Design and performance of the APPLE-Knot undulator

    International Nuclear Information System (INIS)

    Ji, Fuhao; Chang, Rui; Zhou, Qiaogen; Zhang, Wei; Ye, Mao; Sasaki, Shigemi; Qiao, Shan

    2015-01-01

    The design and performance of the Apple-Knot undulator which can generate photons with arbitrary polarization and low on-axis heat load are presented. Along with the development of accelerator technology, synchrotron emittance has continuously decreased. This results in increased brightness, but also causes a heavy heat load on beamline optics. Recently, optical surfaces with 0.1 nm micro-roughness and 0.05 µrad slope error (r.m.s.) have become commercially available and surface distortions due to heat load have become a key factor in determining beamline performance, and heat load has become a serious problem at modern synchrotron radiation facilities. Here, APPLE-Knot undulators which can generate photons with arbitrary polarization, with low on-axis heat load, are reported

  2. Design and performance of the APPLE-Knot undulator

    Energy Technology Data Exchange (ETDEWEB)

    Ji, Fuhao [Department of Physics, State Key Laboratory of Surface Physics, and Laboratory of Advanced Materials, Fudan University, 2005 Songhu Road, Shanghai 200438, People’s Republic of (China); Chang, Rui [State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, 865 Changning Road, Shanghai 200050, People’s Republic of (China); Zhou, Qiaogen; Zhang, Wei [Shanghai Synchrotron Radiation Facility, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, 239 Zhangheng Road, Shanghai 201204, People’s Republic of (China); Ye, Mao [State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, 865 Changning Road, Shanghai 200050, People’s Republic of (China); Sasaki, Shigemi [Hiroshima Synchrotron Radiation Center, Hiroshima University, 2-313 Kagamiyama, Hiroshima 739-0046 (Japan); Qiao, Shan, E-mail: qiaoshan@mail.sim.ac.cn [State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, 865 Changning Road, Shanghai 200050, People’s Republic of (China); School of Physical Science and Technology, ShanghaiTech University, 319 Yueyang Road, Shanghai 200031, People’s Republic of (China)

    2015-06-09

    The design and performance of the Apple-Knot undulator which can generate photons with arbitrary polarization and low on-axis heat load are presented. Along with the development of accelerator technology, synchrotron emittance has continuously decreased. This results in increased brightness, but also causes a heavy heat load on beamline optics. Recently, optical surfaces with 0.1 nm micro-roughness and 0.05 µrad slope error (r.m.s.) have become commercially available and surface distortions due to heat load have become a key factor in determining beamline performance, and heat load has become a serious problem at modern synchrotron radiation facilities. Here, APPLE-Knot undulators which can generate photons with arbitrary polarization, with low on-axis heat load, are reported.

  3. BPS counting for knots and combinatorics on words

    Energy Technology Data Exchange (ETDEWEB)

    Kucharski, Piotr [Faculty of Physics, University of Warsaw,ul. Pasteura 5, 02-093 Warsaw (Poland); Sułkowski, Piotr [Faculty of Physics, University of Warsaw,ul. Pasteura 5, 02-093 Warsaw (Poland); Walter Burke Institute for Theoretical Physics, California Institute of Technology,Pasadena, CA 91125 (United States)

    2016-11-21

    We discuss relations between quantum BPS invariants defined in terms of a product decomposition of certain series, and difference equations (quantum A-polynomials) that annihilate such series. We construct combinatorial models whose structure is encoded in the form of such difference equations, and whose generating functions (Hilbert-Poincaré series) are solutions to those equations and reproduce generating series that encode BPS invariants. Furthermore, BPS invariants in question are expressed in terms of Lyndon words in an appropriate language, thereby relating counting of BPS states to the branch of mathematics referred to as combinatorics on words. We illustrate these results in the framework of colored extremal knot polynomials: among others we determine dual quantum extremal A-polynomials for various knots, present associated combinatorial models, find corresponding BPS invariants (extremal Labastida-Mariño-Ooguri-Vafa invariants) and discuss their integrality.

  4. Gordian Knots of Prevision: The lessons of history

    Science.gov (United States)

    Fleming, J. R.

    2017-12-01

    Atmospheric researchers have long attempted to untie the Gordian Knot of meteorology—that intractable and intertwined tangle of observational imprecision, theoretical uncertainties, and non-linear influences—that, if unraveled, would provide perfect prevision of the weather for ten days, of seasonal conditions for the year, and of climatic conditions for a decade, a century, a millennium, or longer. This presentation, based on Inventing Atmospheric Science (M.I.T. Press, 2016), examines the work of four interconnected generations of scientists (Vilhelm Bjerknes, C.-G. Rossby, Harry Wexler, Ed Lorenz) and the influence of four transformative technologies (radio, nuclear, computation, aerospace) from the dawn of applied fluid dynamics to the emergence of the interdisciplinary atmospheric sciences and the new Gordian Knot of chaos.

  5. Energy and helicity of magnetic torus knots and braids

    Science.gov (United States)

    Oberti, Chiara; Ricca, Renzo L.

    2018-02-01

    By considering steady magnetic fields in the shape of torus knots and unknots in ideal magnetohydrodynamics, we compute some fundamental geometric and physical properties to provide estimates for magnetic energy and helicity. By making use of an appropriate parametrization, we show that knots with dominant toroidal coils that are a good model for solar coronal loops have negligible total torsion contribution to magnetic helicity while writhing number provides a good proxy. Hence, by the algebraic definition of writhe based on crossing numbers, we show that the estimated values of writhe based on image analysis provide reliable information for the exact values of helicity. We also show that magnetic energy is linearly related to helicity, and the effect of the confinement of magnetic field can be expressed in terms of geometric information. These results can find useful application in solar and plasma physics, where braided structures are often present.

  6. BPS counting for knots and combinatorics on words

    Science.gov (United States)

    Kucharski, Piotr; Sułkowski, Piotr

    2016-11-01

    We discuss relations between quantum BPS invariants defined in terms of a product decomposition of certain series, and difference equations (quantum A-polynomials) that annihilate such series. We construct combinatorial models whose structure is encoded in the form of such difference equations, and whose generating functions (Hilbert-Poincaré series) are solutions to those equations and reproduce generating series that encode BPS invariants. Furthermore, BPS invariants in question are expressed in terms of Lyndon words in an appropriate language, thereby relating counting of BPS states to the branch of mathematics referred to as combinatorics on words. We illustrate these results in the framework of colored extremal knot polynomials: among others we determine dual quantum extremal A-polynomials for various knots, present associated combinatorial models, find corresponding BPS invariants (extremal Labastida-Mariño-Ooguri-Vafa invariants) and discuss their integrality.

  7. Polynomial invariants for torus knots and topological strings

    International Nuclear Information System (INIS)

    Labastida, J.M.F.

    2001-01-01

    We make a precision test of a recently proposed conjecture relating Chern-Simons gauge theory to topological string theory on the resolution of the conifold. First, we develop a systematic procedure to extract string amplitudes from vacuum expectation values (vevs) of Wilson loops in Chern-Simons gauge theory, and then we evaluate these vevs in arbitrary irreducible representations of SU(N) for torus knots. We find complete agreement with the predictions derived from the target space interpretation of the string amplitudes. We also show that the structure of the free energy of topological open string theory gives further constraints on the Chern-Simons vevs. Our work provides strong evidence towards an interpretation of knot polynomial invariants as generating functions associated to enumerative problems. (orig.)

  8. New Ways to Cut through Ethical Gordian Knots.

    Science.gov (United States)

    Howe, Edmund G

    2017-01-01

    Clinicians and ethicists routinely encounter complex ethical dilemmas that seem intractable, which have been described as ethical Gordian knots. How can they best assist patients and surrogate decision makers who are entangled in struggles around the capacity to make life-or-death treatment decisions? In this article I describe unconventional and unorthodox approaches to help slice through these dilemmas. Copyright 2017 The Journal of Clinical Ethics. All rights reserved.

  9. Southward migration and fuel deposition of Red Knots Calidris canutus

    OpenAIRE

    Helseth, Anders; Lindström, Åke; Stervander, Martin

    2005-01-01

    We compared the differences between spring and autumn in migration speed, fuelling rates and fuel loads of migrating Red Knots Calidris canutus. As a basis we used ringing data from Ottenby Bird Observatory, southeastern Sweden, collected 1948–2003, with morphometrical data from 1990–2003. Numbers ringed varied between 0 and 301 per year (average 56). Morphometrics, recoveries and recaptures of ringed birds indicated that most birds belonged to the Afro-Siberian subspecies C. c. canutus, poss...

  10. The Knot Spectrum of Confined Random Equilateral Polygons

    Directory of Open Access Journals (Sweden)

    Diao Y.

    2014-01-01

    Full Text Available It is well known that genomic materials (long DNA chains of living organisms are often packed compactly under extreme confining conditions using macromolecular self-assembly processes but the general DNA packing mechanism remains an unsolved problem. It has been proposed that the topology of the packed DNA may be used to study the DNA packing mechanism. For example, in the case of (mutant bacteriophage P4, DNA molecules packed inside the bacteriophage head are considered to be circular since the two sticky ends of the DNA are close to each other. The DNAs extracted from the capsid without separating the two ends can thus preserve the topology of the (circular DNAs. It turns out that the circular DNAs extracted from bacteriophage P4 are non-trivially knotted with very high probability and with a bias toward chiral knots. In order to study this problem using a systematic approach based on mathematical modeling, one needs to introduce a DNA packing model under extreme volume confinement condition and test whether such a model can produce the kind of knot spectrum observed in the experiments. In this paper we introduce and study a model of equilateral random polygons con_ned in a sphere. This model is not meant to generate polygons that model DNA packed in a virus head directly. Instead, the average topological characteristics of this model may serve as benchmark data for totally randomly packed circular DNAs. The difference between the biologically observed topological characteristics and our benchmark data might reveal the bias of DNA packed in the viral capsids and possibly lead to a better understanding of the DNA packing mechanism, at least for the bacteriophage DNA. The purpose of this paper is to provide information about the knot spectrum of equilateral random polygons under such a spherical confinement with length and confinement ratios in a range comparable to circular DNAs packed inside bacteriophage heads.

  11. Knot invariants and M-theory: Proofs and derivations

    Science.gov (United States)

    Errasti Díez, Verónica

    2018-01-01

    We construct two distinct yet related M-theory models that provide suitable frameworks for the study of knot invariants. We then focus on the four-dimensional gauge theory that follows from appropriately compactifying one of these M-theory models. We show that this theory has indeed all required properties to host knots. Our analysis provides a unifying picture of the various recent works that attempt an understanding of knot invariants using techniques of four-dimensional physics. This is a companion paper to K. Dasgupta, V. Errasti Díez, P. Ramadevi, and R. Tatar, Phys. Rev. D 95, 026010 (2017), 10.1103/PhysRevD.95.026010, covering all but Sec. III C. It presents a detailed mathematical derivation of the main results there, as well as additional material. Among the new insights, those related to supersymmetry and the topological twist are highlighted. This paper offers an alternative, complementary formulation of the contents in the first paper, but is self-contained and can be read independently.

  12. Rectangular superpolynomials for the figure-eight knot 41

    Science.gov (United States)

    Kononov, Ya. A.; Morozov, A. Yu.

    2017-11-01

    We rewrite the recently proposed differential expansion formula for HOMFLY polynomials of the knot 41 in an arbitrary rectangular representation R = [rs] as a sum over all Young subdiagrams λ of R with surprisingly simple coefficients of the Z factors. Intriguingly, these coefficients are constructed from the quantum dimensions of symmetric representations of the groups SL(r) and SL(s) and restrict the summation to diagrams with no more than s rows and r columns. Moreover, the β-deformation to Macdonald dimensions yields polynomials with positive integer coefficients, which are plausible candidates for the role of superpolynomials for rectangular representations. Both the polynomiality and the positivity of the coefficients are nonobvious, nevertheless true. This generalizes the previously known formulas for symmetric representations to arbitrary rectangular representations. The differential expansion allows introducing additional gradings. For the trefoil knot 31, to which our results for the knot 41 are immediately extended, we obtain the so-called fourth grading of hyperpolynomials. The property of factorization in roots of unity is preserved even in the five-graded case.

  13. Enamel alteration following tooth bleaching and remineralization.

    Science.gov (United States)

    Coceska, Emilija; Gjorgievska, Elizabeta; Coleman, Nichola J; Gabric, Dragana; Slipper, Ian J; Stevanovic, Marija; Nicholson, John W

    2016-06-01

    The purpose of this study was to compare the effects of professional tooth whitening agents containing highly concentrated hydrogen peroxide (with and without laser activation), on the enamel surface; and the potential of four different toothpastes to remineralize any alterations. The study was performed on 50 human molars, divided in two groups: treated with Opalescence(®) Boost and Mirawhite(®) Laser Bleaching. Furthermore, each group was divided into five subgroups, a control one and 4 subgroups remineralized with: Mirasensitive(®) hap+, Mirawhite(®) Gelleѐ, GC Tooth Mousse™ and Mirafluor(®) C. The samples were analysed by SEM/3D-SEM-micrographs, SEM/EDX-qualitative analysis and SEM/EDX-semiquantitative analysis. The microphotographs show that both types of bleaching cause alterations: emphasized perikymata, erosions, loss of interprizmatic substance; the laser treatment is more aggressive and loss of integrity of the enamel is determined by shearing off the enamel rods. In all samples undergoing remineralization deposits were observed, those of toothpastes based on calcium phosphate technologies seem to merge with each other and cover almost the entire surface of the enamel. Loss of integrity and minerals were detected only in the line-scans of the sample remineralized with GC Tooth Mousse™. The semiquantitative EDX analysis of individual elements in the surface layer of the enamel indicates that during tooth-bleaching with HP statistically significant loss of Na and Mg occurs, whereas the bleaching in combination with a laser leads to statistically significant loss of Ca and P. The results undoubtedly confirm that teeth whitening procedures lead to enamel alterations. In this context, it must be noted that laser bleaching is more aggressive for dental substances. However, these changes are reversible and can be repaired by application of remineralization toothpastes. © 2015 The Authors Journal of Microscopy © 2015 Royal Microscopical Society.

  14. Thermal induced EPR signals in tooth enamel

    International Nuclear Information System (INIS)

    Fattibene, P.; Aragno, D.; Onori, S.; Pressello, M.C.

    2000-01-01

    Electron paramagnetic resonance (EPR) spectroscopy was used to detect the effects of temperature on powdered human tooth enamel, not irradiated in the laboratory. Samples were heated at temperature between 350 and 450, at 600 and at 1000 deg. C, for different heating times, between 6 min and 39 h. Changes in the EPR spectra were detected, with the formation of new signals. Possible correlation between the changes in EPR spectra and modifications in the enamel and in the mineral phase of bone detected with other techniques is discussed. The implications for dosimetric applications of signals induced by overheating due to mechanical friction during sample preparation are underlined

  15. Tightening slip knots in raw and degummed silk to increase toughness without losing strength

    OpenAIRE

    Pantano, Maria; Berardo, Alice; Pugno, Nicola

    2016-01-01

    Knots are fascinating topological elements, which can be found in both natural and artificial systems. While in most of the cases, knots cannot be loosened without breaking the strand where they are tightened, herein, attention is focused on slip or running knots, which on the contrary can be unfastened without compromising the structural integrity of their hosting material. Two different topologies are considered, involving opposite unfastening mechanisms, and their influence on the mechanic...

  16. Retrospective individual dosimetry using EPR of tooth enamel

    International Nuclear Information System (INIS)

    Skvortzo, V.; Ivannikov, A.; Stepanenko, V.; Wieser, A.; Bougai, A.; Brick, A.; Chumak, V.; Radchuk, V.; Repin, V.; Kirilov, V.

    1996-01-01

    The results of joint investigations (in the framework of ECP-10 program) aimed on the improvement of the sensitivity and accuracy of the procedure of dose measurement using tooth enamel EPR spectroscopy are presented. It is shown, what the sensitivity of method may be increased using special physical-chemical procedure of the enamel samples treatment, which leads to the reducing of EPR signal of organic components in enamel. Tooth diseases may have an effect on radiation sensitivity of enamel. On the basis of statistical analysis of the results of more then 2000 tooth enamel samples measurements it was shown, what tooth enamel EPR spectroscopy gives opportunity to register contribution into total dose, which is caused by natural environmental radiation and by radioactive contamination. EPR response of enamel to ultraviolet exposure is investigated and possible influences to EPR dosimetry is discussed. The correction factors for EPR dosimetry in real radiation fields are estimated

  17. Size dependent elastic modulus and mechanical resilience of dental enamel.

    Science.gov (United States)

    O'Brien, Simona; Shaw, Jeremy; Zhao, Xiaoli; Abbott, Paul V; Munroe, Paul; Xu, Jiang; Habibi, Daryoush; Xie, Zonghan

    2014-03-21

    Human tooth enamel exhibits a unique microstructure able to sustain repeated mechanical loading during dental function. Although notable advances have been made towards understanding the mechanical characteristics of enamel, challenges remain in the testing and interpretation of its mechanical properties. For example, enamel was often tested under dry conditions, significantly different from its native environment. In addition, constant load, rather than indentation depth, has been used when mapping the mechanical properties of enamel. In this work, tooth specimens are prepared under hydrated conditions and their stiffnesses are measured by depth control across the thickness of enamel. Crystal arrangement is postulated, among other factors, to be responsible for the size dependent indentation modulus of enamel. Supported by a simple structure model, effective crystal orientation angle is calculated and found to facilitate shear sliding in enamel under mechanical contact. In doing so, the stress build-up is eased and structural integrity is maintained. Copyright © 2014 Elsevier Ltd. All rights reserved.

  18. Targeted p120-catenin ablation disrupts dental enamel development

    DEFF Research Database (Denmark)

    Bartlett, John D; Dobeck, Justine M; Tye, Coralee E

    2010-01-01

    Dental enamel development occurs in stages. The ameloblast cell layer is adjacent to, and is responsible for, enamel formation. When rodent pre-ameloblasts become tall columnar secretory-stage ameloblasts, they secrete enamel matrix proteins, and the ameloblasts start moving in rows that slide...... by one another. This movement is necessary to form the characteristic decussating enamel prism pattern. Thus, a dynamic system of intercellular interactions is required for proper enamel development. Cadherins are components of the adherens junction (AJ), and they span the cell membrane to mediate...... attachment to adjacent cells. p120 stabilizes cadherins by preventing their internalization and degradation. So, we asked if p120-mediated cadherin stability is important for dental enamel formation. Targeted p120 ablation in the mouse enamel organ had a striking effect. Secretory stage ameloblasts detached...

  19. Ceramic-like wear behaviour of human dental enamel.

    Science.gov (United States)

    Arsecularatne, J A; Hoffman, M

    2012-04-01

    This paper reports a transmission electron microscopy (TEM) analysis of subsurfaces of enamel specimens following in vitro reciprocating wear tests with an enamel cusp sliding on a flat enamel specimen under hydrated conditions. The obtained results show that crack formation occurred in the wear scar subsurface. The path followed by these cracks seems to be dictated either by the histological structure of enamel or by the contact stress field. Moreover, the analysis of a set of enamel wear results obtained from the literature and application of fracture-based models, originally developed for ceramics, correlate well, confirming the similar wear processes taking place in these materials. This analysis also reveals a marked influence of coefficient of friction on the enamel wear rate: for a higher coefficient of friction value, enamel wear can be severe even under forces generated during normal operation of teeth. Copyright © 2011 Elsevier Ltd. All rights reserved.

  20. Regulated fracture in tooth enamel: a nanotechnological strategy from nature.

    Science.gov (United States)

    Ghadimi, Elnaz; Eimar, Hazem; Song, Jun; Marelli, Benedetto; Ciobanu, Ovidiu; Abdallah, Mohamed-Nur; Stähli, Christoph; Nazhat, Showan N; Vali, Hojatollah; Tamimi, Faleh

    2014-07-18

    Tooth enamel is a very brittle material; however it has the ability to sustain cracks without suffering catastrophic failure throughout the lifetime of mechanical function. We propose that the nanostructure of enamel can play a significant role in defining its unique mechanical properties. Accordingly we analyzed the nanostructure and chemical composition of a group of teeth, and correlated it with the crack resistance of the same teeth. Here we show how the dimensions of apatite nanocrystals in enamel can affect its resistance to crack propagation. We conclude that the aspect ratio of apatite nanocrystals in enamel determines its resistance to crack propagation. According to this finding, we proposed a new model based on the Hall-Petch theory that accurately predicts crack propagation in enamel. Our new biomechanical model of enamel is the first model that can successfully explain the observed variations in the behavior of crack propagation of tooth enamel among different humans. Copyright © 2014 Elsevier Ltd. All rights reserved.

  1. Towards enamel biomimetics: Structure, mechanical properties and biomineralization of dental enamel

    Science.gov (United States)

    Fong, Hanson Kwok

    Dental enamel is the most mineralized tissue in the human body. This bioceramic, composed largely of hydroxyapatite (HAp), is also one of the most durable tissues despite a lifetime of masticatory loading and bacterial attack. The biosynthesis of enamel, which occurs in physiological conditions is a complex orchestration of protein assembly and mineral formation. The resulting product is the hardest tissue in the vertebrate body with the longest and most organized arrangement of hydroxyapatite crystals known to biomineralizing systems. Detail understanding of the structure of enamel in relationship to its mechanical function and the biomineralization process will provide a framework for enamel regeneration as well as potential lessons in the design of engineering materials. The objective of this study, therefore, is twofold: (1) establish the structure-function relationship of enamel as well as the dentine-enamel junction (DEJ) and (2) determine the effect of proteins on the enamel biomineralization process. A hierarchy in the enamel structure was established by means of various microscopy techniques (e.g. SEM, TEM, AFM). Mechanical properties (hardness and elastic modulus) associated with the microstructural features were also determined by nanoindentation. Furthermore, the DEJ was found to have a width in the range of micrometers to 10s of micrometers with continuous change in structure and mechanical properties. Indentation tests and contact fatigue tests using a spherical indenter have revealed that the structural features in the enamel and the DEJ played important roles in containing crack propagation emanating from the enamel tissue. To further understand the effect of this protein on the biominerailzation process, we have studied genetically engineered animals that express altered amelogenin which lack the known self-assembly properties. This in vivo study has revealed that, without the proper self-assembly of the amelogenin protein as demonstrated by the

  2. Helium ion microscopy of enamel crystallites and extracellular tooth enamel matrix.

    Science.gov (United States)

    Bidlack, Felicitas B; Huynh, Chuong; Marshman, Jeffrey; Goetze, Bernhard

    2014-01-01

    An unresolved problem in tooth enamel studies has been to analyze simultaneously and with sufficient spatial resolution both mineral and organic phases in their three dimensional (3D) organization in a given specimen. This study aims to address this need using high-resolution imaging to analyze the 3D structural organization of the enamel matrix, especially amelogenin, in relation to forming enamel crystals. Chemically fixed hemi-mandibles from wild type mice were embedded in LR White acrylic resin, polished and briefly etched to expose the organic matrix in developing tooth enamel. Full-length amelogenin was labeled with specific antibodies and 10 nm immuno-gold. This allowed us to use and compare two different high-resolution imaging techniques for the analysis of uncoated samples. Helium ion microscopy (HIM) was applied to study the spatial organization of organic and mineral structures, while field emission scanning electron microscopy (FE-SEM) in various modes, including backscattered electron detection, allowed us to discern the gold-labeled proteins. Wild type enamel in late secretory to early maturation stage reveals adjacent to ameloblasts a lengthwise parallel alignment of the enamel matrix proteins, including full-length amelogenin proteins, which then transitions into a more heterogeneous appearance with increasing distance from the mineralization front. The matrix adjacent to crystal bundles forms a smooth and lacey sheath, whereas between enamel prisms it is organized into spherical components that are interspersed with rod-shaped protein. These findings highlight first, that the heterogeneous organization of the enamel matrix can be visualized in mineralized en bloc samples. Second, our results illustrate that the combination of these techniques is a powerful approach to elucidate the 3D structural organization of organic matrix molecules in mineralizing tissue in nanometer resolution.

  3. Helium ion microscopy of enamel crystallites and extracellular tooth enamel matrix

    Directory of Open Access Journals (Sweden)

    Felicitas B Bidlack

    2014-10-01

    Full Text Available An unresolved problem in tooth enamel studies has been to analyze simultaneously and with sufficient spatial resolution both mineral and organic phases in their three dimensional (3D organization in a given specimen. This study aims to address this need using high-resolution imaging to analyze the 3D structural organization of the enamel matrix, especially amelogenin, in relation to forming enamel crystals. Chemically fixed hemi-mandibles from wild type mice were embedded in LR White acrylic resin, polished and briefly etched to expose the organic matrix in developing tooth enamel. Full-length amelogenin was labeled with specific antibodies and 10 nm immuno-gold. This allowed us to use and compare two different high-resolution imaging techniques for the analysis of uncoated samples. Helium ion microscopy (HIM was applied to study the spatial organization of organic and mineral structures, while field emission scanning electron microscopy (FE-SEM in various modes, including backscattered electron detection, allowed us to discern the gold-labeled proteins. Wild type enamel in late secretory to early maturation stage reveals adjacent to ameloblasts a lengthwise parallel alignment of the enamel matrix proteins, including full-length amelogenin proteins, which then transitions into a more heterogeneous appearance with increasing distance from the mineralization front. The matrix adjacent to crystal bundles forms a smooth and lacey sheath, whereas between enamel prisms it is organized into spherical components that are interspersed with rod-shaped protein. These findings highlight first, that the heterogeneous organization of the enamel matrix can be visualized in mineralized en bloc samples. Second, our results illustrate that the combination of these techniques is a powerful approach to elucidate the 3D structural organization of organic matrix molecules in mineralizing tissue in nanometer resolution.

  4. Knotting dynamics of DNA chains of different length confined in nanochannels

    International Nuclear Information System (INIS)

    Suma, Antonio; Micheletti, Cristian; Orlandini, Enzo

    2015-01-01

    Langevin dynamics simulations are used to characterize the typical mechanisms governing the spontaneous tying, untying and the dynamical evolution of knots in coarse-grained models of DNA chains confined in nanochannels. In particular we focus on how these mechanisms depend on the chain contour length, L c , at a fixed channel width D = 56 nm corresponding to the onset of the Odijk scaling regime where chain backfoldings and hence knots are disfavoured but not suppressed altogether. We find that the lifetime of knots grows significantly with L c , while that of unknots varies to a lesser extent. The underlying kinetic mechanisms are clarified by analysing the evolution of the knot position along the chain. At the considered confinement, in fact, knots are typically tied by local backfoldings of the chain termini where they are eventually untied after a stochastic motion along the chain. Consequently, the lifetime of unknots is mostly controlled by backfoldings events at the chain ends, which is largely independent of L c . The lifetime of knots, instead, increases significantly with L c because knots can, on average, travel farther along the chain before being untied. The observed interplay of knots and unknots lifetimes underpins the growth of the equilibrium knotting probability of longer and longer chains at fixed channel confinement. (paper)

  5. Enamel subsurface damage due to tooth preparation with diamonds.

    Science.gov (United States)

    Xu, H H; Kelly, J R; Jahanmir, S; Thompson, V P; Rekow, E D

    1997-10-01

    In clinical tooth preparation with diamond burs, sharp diamond particles indent and scratch the enamel, causing material removal. Such operations may produce subsurface damage in enamel. However, little information is available on the mechanisms and the extent of subsurface damage in enamel produced during clinical tooth preparation. The aim of this study, therefore, was to investigate the mechanisms of subsurface damage produced in enamel during tooth preparation by means of diamond burs, and to examine the dependence of such damage on enamel rod orientation, diamond particle size, and removal rate. Subsurface damage was evaluated by a bonded-interface technique. Tooth preparation was carried out on two enamel rod orientations, with four clinical diamond burs (coarse, medium, fine, and superfine) used in a dental handpiece. The results of this study showed that subsurface damage in enamel took the form of median-type cracks and distributed microcracks, extending preferentially along the boundaries between the enamel rods. Microcracks within individual enamel rods were also observed. The median-type cracks were significantly longer in the direction parallel to the enamel rods than perpendicular to the rods. Preparation with the coarse diamond bur produced cracks as deep as 84 +/- 30 microns in enamel. Finishing with fine diamond burs was effective in crack removal. The crack lengths in enamel were not significantly different when the removal rate was varied. Based on these results, it is concluded that subsurface damage in enamel induced by tooth preparation takes the form of median-type cracks as well as inter- and intra-rod microcracks, and that the lengths of these cracks are sensitive to diamond particle size and enamel rod orientation, but insensitive to removal rate.

  6. Deformation behavior of human enamel and dentin-enamel junction under compression.

    Science.gov (United States)

    Zaytsev, Dmitry; Panfilov, Peter

    2014-01-01

    Deformation behavior under uniaxial compression of human enamel and dentin-enamel junction (DEJ) is considered in comparison with human dentin. This deformation scheme allows estimating the total response from all levels of the hierarchical composite material in contrast with the indentation, which are limited by the mesoscopic and microscopic scales. It was shown for the first time that dental enamel is the strength (up to 1850MPa) hard tissue, which is able to consider some elastic (up to 8%) and plastic (up to 5%) deformation under compression. In so doing, it is almost undeformable substance under the creep condition. Mechanical properties of human enamel depend on the geometry of sample. Human dentin exhibits the similar deformation behavior under compression, but the values of its elasticity (up to 40%) and plasticity (up to 18%) are much more, while its strength (up to 800MPa) is less in two times. Despite the difference in mechanical properties, human enamel is able to suppress the cracking alike dentin. Deformation behavior under the compression of the samples contained DEJ as the same to dentin. This feature allows a tooth to be elastic-plastic (as dentin) and wear resistible (as enamel), simultaneously. © 2013 Elsevier B.V. All rights reserved.

  7. Enamel surface remineralization: Using synthetic nanohydroxyapatite

    Directory of Open Access Journals (Sweden)

    J Shanti Swarup

    2012-01-01

    Full Text Available Objective: The purpose of this study was to evaluate the effects of synthetically processed hydroxyapatite particles in remineralization of the early enamel lesions in comparison with 2% sodium fluoride. Materials and Methods: Thirty sound human premolars were divided into nanohydroxyapatite group (n0 = 15 and the sodium fluoride group (n = 15. The specimens were subjected to demineralization before being coated with 10% aqueous slurry of 20 nm nanohydroxyapatite or 2% sodium fluoride. The remineralizing efficacy of the materials was evaluated using surface microhardness (SMH measurements, scanning microscopic analysis and analysis of the Ca/P ratio of the surface enamel. Data analysis was carried out using paired t-test and independent t-test. Results: The results showed that the nanohydroxyapatite group produced a surface morphology close to the biologic enamel, the increase in mineral content (Ca/P ratio was more significant in the nanohydroxyapatite group ( P 0.05. Conclusion: The use of biomimetic nanohydroxyapatite as a remineralizing agent holds promise as a new synthetic enamel biocompatible material to repair early carious lesions.

  8. Nanoindentation creep behavior of human enamel.

    Science.gov (United States)

    He, Li-Hong; Swain, Michael V

    2009-11-01

    In this study, the indentation creep behavior of human enamel was investigated with a nanoindentation system and a Berkovich indenter at a force of 250 mN with one-step loading and unloading method. A constant hold period of 900 s was incorporated into each test at the maximum load as well at 5 mN minimum load during unloading. The indentation creep at the maximum load and creep recovery at the minimum load was described with a double exponential function and compared with other classic viscoelastic models (Debye/Maxwell and Kohlrausch-Williams-Watts). Indentation creep rate sensitivity, m, of human enamel was measured for the first time with a value of approximately 0.012. Enamel displayed both viscoelastic and viscoplastic behavior similar to that of bone. These results indicate that, associated with entrapment of particulates between teeth under functional loading and sliding wear conditions, the enamel may inelastically deform but recover upon its release. This behavior may be important in explaining the excellent wear resistance, antifatigue, and crack resistant abilities of natural tooth structure. (c) 2008 Wiley Periodicals, Inc.

  9. Tooth enamel hypoplasia in PHACE syndrome.

    Science.gov (United States)

    Chiu, Yvonne E; Siegel, Dawn H; Drolet, Beth A; Hodgson, Brian D

    2014-01-01

    Individuals with PHACE syndrome (posterior fossa malformations, hemangiomas, arterial anomalies, cardiac defects, eye abnormalities, sternal cleft, and supraumbilical raphe syndrome) have reported dental abnormalities to their healthcare providers and in online forums, but dental involvement has not been comprehensively studied. A study was conducted at the third PHACE Family Conference, held in Milwaukee, Wisconsin, in July 2012. A pediatric dentist examined subjects at enrollment. Eighteen subjects were enrolled. The median age was 4.2 years (range 9 mos-9 yrs; 14 girls, 4 boys). Eleven of 18 patients had intraoral hemangiomas and five of these (50%) had hypomature enamel hypoplasia. None of the seven patients without intraoral hemangiomas had enamel hypoplasia. No other dental abnormalities were seen. Enamel hypoplasia may be a feature of PHACE syndrome when an intraoral hemangioma is present. Enamel hypoplasia increases the risk of caries, and clinicians should refer children with PHACE syndrome to a pediatric dentist by 1 year of age. © 2014 Wiley Periodicals, Inc.

  10. Microtensile bond strength of enamel after bleaching.

    Science.gov (United States)

    Lago, Andrea Dias Neves; Garone-Netto, Narciso

    2013-01-01

    To evaluate the bond strength of a composite resin to the bovine enamel bleached with 35% hydrogen peroxide. It was used an etching-and-rinse adhesive system employed immediately, 7 and 14 days after the bleaching. Twenty bovine teeth were randomly distributed into 4 groups (n = 5), 3 experimental and 1 control. G1: Unbleached + restoration 14 days after storage in artificial saliva (control); G2: Bleached + restoration immediately after bleaching; G3: Bleached + restoration 7 days after bleaching; G4: Bleached + restoration 14 days after bleaching. Their buccal enamel surfaces were flattened, and a 25 mm² (5 × 5 mm) area from each one of these regions was outlined so as to standardize the experimental region. Universal hybrid composite resin Filtek™Z350 was inserted into four layers of 1 mm each and photo-activated. The bond strength was quantitatively evaluated by a microtensile test (1.0 mm/min) 24 h after the restorative procedures. The failure mode was assessed through scanning electron microscopy (SEM). There was a significant reduction in the bond strength of the restored teeth immediately after the bleaching (G2). There were no significant differences in enamel bond strength between groups G1, G3, and G4. There was a predominance of adhesive and mixed (cohesive + adhesive) failure in all groups. The 7-day-period after the end of the bleaching with 35% hydrogen peroxide was enough to achieve the appropriate values of bond strength to the enamel.

  11. A 'FIREWORK' OF H2 KNOTS IN THE PLANETARY NEBULA NGC 7293 (THE HELIX NEBULA)

    International Nuclear Information System (INIS)

    Matsuura, M.; Speck, A. K.; McHunu, B. M.; Tanaka, I.; Wright, N. J.; Viti, S.; Wesson, R.; Smith, M. D.; Zijlstra, A. A.

    2009-01-01

    We present a deep and wide field-of-view (4' x 7') image of the planetary nebula (PN) NGC 7293 (the Helix Nebula) in the 2.12 μm H 2 v = 1 → 0 S(1) line. The excellent seeing (0.''4) at the Subaru Telescope, allows the details of cometary knots to be examined. The knots are found at distances of 2.'2-6.'4 from the central star (CS). At the inner edge and in the inner ring (up to 4.'5 from the CS), the knot often show a 'tadpole' shape, an elliptical head with a bright crescent inside and a long tail opposite to the CS. In detail, there are variations in the tadpole shapes, such as narrowing tails, widening tails, meandering tails, or multipeaks within a tail. In the outer ring (4.'5-6.'4 from the CS), the shapes are more fractured, and the tails do not collimate into a single direction. The transition in knot morphology from the inner edge to the outer ring is clearly seen. The number density of knots governs the H 2 surface brightness in the inner ring: H 2 exists only within the knots. Possible mechanisms which contribute to the shaping of the knots are discussed, including photoionization and streaming motions. A plausible interpretation of our images is that inner knots are being overrun by a faster wind, but that this has not (yet) reached the outer knots. Based on H 2 formation and destruction rates, H 2 gas can survive in knots from formation during the late asymptotic giant branch phase throughout the PN phase. These observations provide new constraints on the formation and evolution of knots, and on the physics of molecular gas embedded within ionized gas.

  12. A "Firework" of H2 Knots in the Planetary Nebula NGC 7293 (The Helix Nebula)

    Science.gov (United States)

    Matsuura, M.; Speck, A. K.; McHunu, B. M.; Tanaka, I.; Wright, N. J.; Smith, M. D.; Zijlstra, A. A.; Viti, S.; Wesson, R.

    2009-08-01

    We present a deep and wide field-of-view (4' × 7') image of the planetary nebula (PN) NGC 7293 (the Helix Nebula) in the 2.12 μm H2 v = 1 → 0 S(1) line. The excellent seeing (0farcs4) at the Subaru Telescope, allows the details of cometary knots to be examined. The knots are found at distances of 2farcm2-6farcm4 from the central star (CS). At the inner edge and in the inner ring (up to 4farcm5 from the CS), the knot often show a "tadpole" shape, an elliptical head with a bright crescent inside and a long tail opposite to the CS. In detail, there are variations in the tadpole shapes, such as narrowing tails, widening tails, meandering tails, or multipeaks within a tail. In the outer ring (4farcm5-6farcm4 from the CS), the shapes are more fractured, and the tails do not collimate into a single direction. The transition in knot morphology from the inner edge to the outer ring is clearly seen. The number density of knots governs the H2 surface brightness in the inner ring: H2 exists only within the knots. Possible mechanisms which contribute to the shaping of the knots are discussed, including photoionization and streaming motions. A plausible interpretation of our images is that inner knots are being overrun by a faster wind, but that this has not (yet) reached the outer knots. Based on H2 formation and destruction rates, H2 gas can survive in knots from formation during the late asymptotic giant branch phase throughout the PN phase. These observations provide new constraints on the formation and evolution of knots, and on the physics of molecular gas embedded within ionized gas. Based on data taken with the Subaru Telescope, National Astronomical Observatory of Japan (proposal ID S07B-054).

  13. Ectopic expression of dentin sialoprotein during amelogenesis hardens bulk enamel.

    Science.gov (United States)

    White, Shane N; Paine, Michael L; Ngan, Amanda Y W; Miklus, Vetea G; Luo, Wen; Wang, HongJun; Snead, Malcolm L

    2007-02-23

    Dentin sialophosphpoprotein (Dspp) is transiently expressed in the early stage of secretory ameloblasts. The secretion of ameloblast-derived Dspp is short-lived, correlates to the establishment of the dentinoenamel junction (DEJ), and is consistent with Dspp having a role in producing the specialized first-formed harder enamel adjacent to the DEJ. Crack diffusion by branching and dissipation within this specialized first-formed enamel close to the DEJ prevents catastrophic interfacial damage and tooth failure. Once Dspp is secreted, it is subjected to proteolytic cleavage that results in two distinct proteins referred to as dentin sialoprotein (Dsp) and dentin phosphoprotein (Dpp). The purpose of this study was to investigate the biological and mechanical contribution of Dsp and Dpp to enamel formation. Transgenic mice were engineered to overexpress either Dsp or Dpp in their enamel organs. The mechanical properties (hardness and toughness) of the mature enamel of transgenic mice were compared with genetically matched and age-matched nontransgenic animals. Dsp and Dpp contributions to enamel formation greatly differed. The inclusion of Dsp in bulk enamel significantly and uniformly increased enamel hardness (20%), whereas the inclusion of Dpp weakened the bulk enamel. Thus, Dsp appears to make a unique contribution to the physical properties of the DEJ. Dsp transgenic animals have been engineered with superior enamel mechanical properties.

  14. The molecular basis of hereditary enamel defects in humans.

    Science.gov (United States)

    Wright, J T; Carrion, I A; Morris, C

    2015-01-01

    The formation of human enamel is highly regulated at the molecular level and involves thousands of genes. Requisites for development of this highly mineralized tissue include cell differentiation; production of a unique extracellular matrix; processing of the extracellular matrix; altering of cell function during different stages of enamel formation; cell movement and attachment; regulation of ion and protein movement; and regulation of hydration, pH, and other conditions of the microenvironment, to name just a few. Not surprising, there is a plethora of hereditary conditions with an enamel phenotype. The objective of this review was to identify the hereditary conditions listed on Online Mendelian Inheritance in Man (OMIM) that have an associated enamel phenotype and whether a causative gene has been identified. The OMIM database was searched with the terms amelogenesis, enamel, dental, and tooth, and all results were screened by 2 individuals to determine if an enamel phenotype was identified. Gene and gene product function was reviewed on OMIM and from publications identified in PubMed. The search strategy revealed 91 conditions listed in OMIM as having an enamel phenotype, and of those, 71 have a known molecular etiology or linked genetic loci. The purported protein function of those conditions with a known genetic basis included enzymes, regulatory proteins, extracellular matrix proteins, transcription factors, and transmembrane proteins. The most common enamel phenotype was a deficient amount of enamel, or enamel hypoplasia, with hypomineralization defects being reported less frequently. Knowing these molecular defects allows an initial cataloging of molecular pathways that lead to hereditary enamel defects in humans. This knowledge provides insight into the diverse molecular pathways involved in enamel formation and can be useful when searching for the genetic etiology of hereditary conditions that involve enamel. © International & American Associations for

  15. The Molecular Basis of Hereditary Enamel Defects in Humans

    Science.gov (United States)

    Carrion, I.A.; Morris, C.

    2015-01-01

    The formation of human enamel is highly regulated at the molecular level and involves thousands of genes. Requisites for development of this highly mineralized tissue include cell differentiation; production of a unique extracellular matrix; processing of the extracellular matrix; altering of cell function during different stages of enamel formation; cell movement and attachment; regulation of ion and protein movement; and regulation of hydration, pH, and other conditions of the microenvironment, to name just a few. Not surprising, there is a plethora of hereditary conditions with an enamel phenotype. The objective of this review was to identify the hereditary conditions listed on Online Mendelian Inheritance in Man (OMIM) that have an associated enamel phenotype and whether a causative gene has been identified. The OMIM database was searched with the terms amelogenesis, enamel, dental, and tooth, and all results were screened by 2 individuals to determine if an enamel phenotype was identified. Gene and gene product function was reviewed on OMIM and from publications identified in PubMed. The search strategy revealed 91 conditions listed in OMIM as having an enamel phenotype, and of those, 71 have a known molecular etiology or linked genetic loci. The purported protein function of those conditions with a known genetic basis included enzymes, regulatory proteins, extracellular matrix proteins, transcription factors, and transmembrane proteins. The most common enamel phenotype was a deficient amount of enamel, or enamel hypoplasia, with hypomineralization defects being reported less frequently. Knowing these molecular defects allows an initial cataloging of molecular pathways that lead to hereditary enamel defects in humans. This knowledge provides insight into the diverse molecular pathways involved in enamel formation and can be useful when searching for the genetic etiology of hereditary conditions that involve enamel. PMID:25389004

  16. Effects of ultrasonic instrumentation on enamel surfaces with various defects.

    Science.gov (United States)

    Kim, S-Y; Kang, M-K; Kang, S-M; Kim, H-E

    2018-05-01

    The aim of this study was to analyse the enamel damage caused by ultrasonic scaling of teeth with various enamel conditions that are difficult to identify by visual inspection, such as enamel cracks, early caries and resin restorations. In total, 120 tooth surfaces were divided into 4 experimental groups using a quantitative light-induced fluorescence-digital system: sound enamel group, enamel cracks group, early caries group and resin restoration group. A skilled dental hygienist performed ultrasonic scaling under a standardized set of conditions: a ≤ 15° angle between the scaler tip and tooth surface and 40-80 g of lateral pressure at the rate of 12 times/10 s. Following scaling, the depth of enamel damage was measured using a surface profilometer and observed using scanning electron microscopy (SEM). The damage depth was the greatest in the enamel cracks group (37.63 ± 34.42 μm), followed by the early caries group (26.81 ± 8.67 μm), resin restoration group (19.63 ± 6.73 μm) and the sound enamel group (17.00 ± 5.66 μm). The damage depth was significantly deeper in the enamel cracks and early caries groups than in the sound enamel group (P enamel loss in the enamel cracks, early caries and resin restoration groups. The results of this study suggest that ultrasonic scaling can cause further damage to teeth with enamel cracks, early caries and resin restorations. Therefore, accurate identification of tooth conditions and calculus before the initiation of ultrasonic scaling is necessary to minimize damage. © 2018 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  17. Near-UV laser treatment of extrinsic dental enamel stains.

    Science.gov (United States)

    Schoenly, J E; Seka, W; Featherstone, J D B; Rechmann, P

    2012-04-01

    The selective ablation of extrinsic dental enamel stains using a 400-nm laser is evaluated at several fluences for completely removing stains with minimal damage to the underlying enamel. A frequency-doubled Ti:sapphire laser (400-nm wavelength, 60-nanosecond pulse duration, 10-Hz repetition rate) was used to treat 10 extracted human teeth with extrinsic enamel staining. Each tooth was irradiated perpendicular to the surface in a back-and-forth motion over a 1-mm length using an ∼300-µm-diam 10th-order super-Gaussian beam with fluences ranging from 0.8 to 6.4 J/cm(2) . Laser triangulation determined stain depth and volume removed by measuring 3D surface images before and after irradiation. Scanning electron microscopy evaluated the surface roughness of enamel following stain removal. Fluorescence spectroscopy measured spectra of unbleached and photobleached stains in the spectral range of 600-800 nm. Extrinsic enamel stains are removed with laser fluences between 0.8 and 6.4 J/cm(2) . Stains removed on sound enamel leave behind a smooth enamel surface. Stain removal in areas with signs of earlier cariogenic acid attacks resulted in isolated and randomly located laser-induced, 50-µm-diam enamel pits. These pits contain 0.5-µm diam, smooth craters indicative of heat transfer from the stain to the enamel and subsequent melting and water droplet ejection. Ablation stalling of enamel stains is typically observed at low fluences (Laser ablation of extrinsic enamel stains at 400 nm is observed to be most efficient above 3 J/cm(2) with minimal damage to the underlying enamel. Unsound underlying enamel is also observed to be selectively removed after irradiation. Copyright © 2012 Wiley Periodicals, Inc.

  18. Knots and surfaces a guide to discovering mathematics

    CERN Document Server

    Farmer, David W

    1995-01-01

    In most mathematics textbooks, the most exciting part of mathematics-the process of invention and discovery-is completely hidden from the reader. The aim of Knots and Surfaces is to change all that. By means of a series of carefully selected tasks, this book leads readers to discover some real mathematics. There are no formulas to memorize; no procedures to follow. The book is a guide: its job is to start you in the right direction and to bring you back if you stray too far. Discovery is left to you. Suitable for a one-semester course at the beginning undergraduate level, there are no prerequi

  19. Explorations in topology map coloring, surfaces and knots

    CERN Document Server

    Gay, David

    2013-01-01

    Explorations in Topology, Second Edition, provides students a rich experience with low-dimensional topology (map coloring, surfaces, and knots), enhances their geometrical and topological intuition, empowers them with new approaches to solving problems, and provides them with experiences that will help them make sense of future, more formal topology courses. The book's innovative story-line style models the problem-solving process, presents the development of concepts in a natural way, and engages students in meaningful encounters with the material. The updated end-of-chapter investigation

  20. Alginate hydrogel enriched with enamel matrix derivative to target osteogenic cell differentiation in TiO2 scaffolds

    Directory of Open Access Journals (Sweden)

    Helen Pullisaar

    2015-03-01

    Full Text Available The purpose of bone tissue engineering is to employ scaffolds, cells, and growth factors to facilitate healing of bone defects. The aim of this study was to assess the viability and osteogenic differentiation of primary human osteoblasts and adipose tissue–derived mesenchymal stem cells from various donors on titanium dioxide (TiO2 scaffolds coated with an alginate hydrogel enriched with enamel matrix derivative. Cells were harvested for quantitative reverse transcription polymerase chain reaction on days 14 and 21, and medium was collected on days 2, 14, and 21 for protein analyses. Neither coating with alginate hydrogel nor alginate hydrogel enriched with enamel matrix derivative induced a cytotoxic response. Enamel matrix derivative–enriched alginate hydrogel significantly increased the expression of osteoblast markers COL1A1, TNFRSF11B, and BGLAP and secretion of osteopontin in human osteoblasts, whereas osteogenic differentiation of human adipose tissue–derived mesenchymal stem cells seemed unaffected by enamel matrix derivative. The alginate hydrogel coating procedure may have potential for local delivery of enamel matrix derivative and other stimulatory factors for use in bone tissue engineering.

  1. Dental enamel defects, caries experience and oral health-related quality of life: a cohort study.

    Science.gov (United States)

    Arrow, P

    2017-06-01

    The impact of enamel defects of the first permanent molars on caries experience and child oral health-related quality of life was evaluated in a cohort study. Children who participated in a study of enamel defects of the first permanent molars 8 years earlier were invited for a follow-up assessment. Consenting children completed the Child Perception Questionnaire and the faces Modified Child Dental Anxiety Scale, and were examined by two calibrated examiners. ANOVA, Kruskal-Wallis, negative binomial and logistic regression were used for data analyses. One hundred and eleven children returned a completed questionnaire and 91 were clinically examined. Negative binomial regression found that oral health impacts were associated with gender (boys, risk ratio (RR) = 0.73, P = 0.03) and decayed, missing or filled permanent teeth (DMFT) (RR = 1.1, P = 0.04). The mean DMFT of children were sound (0.9, standard deviation (SD) = 1.4), diffuse defects (0.8, SD = 1.7), demarcated defects (1.5, SD = 1.4) and pit defects (1.3, SD = 2.3) (Kruskal-Wallis, P = 0.05). Logistic regression of first permanent molar caries found higher odds of caries experience with baseline primary tooth caries experience (odds ratio (OR) = 1.5, P = 0.01), the number of teeth affected by enamel defects (OR = 1.9, P = 0.05) and lower odds with the presence of diffuse enamel defects (OR = 0.1, P = 0.04). The presence of diffuse enamel defects was associated with lower odds of caries experience. © 2016 Australian Dental Association.

  2. Production of highly knotted DNA by means of cosmid circularization inside phage capsids

    Directory of Open Access Journals (Sweden)

    Trigueros Sonia

    2007-12-01

    Full Text Available Abstract Background The formation of DNA knots is common during biological transactions. Yet, functional implications of knotted DNA are not fully understood. Moreover, potential applications of DNA molecules condensed by means of knotting remain to be explored. A convenient method to produce abundant highly knotted DNA would be highly valuable for these studies. Results We had previously shown that circularization of the 11.2 kb linear DNA of phage P4 inside its viral capsid generates complex knots by the effect of confinement. We demonstrate here that this mechanism is not restricted to the viral genome. We constructed DNA cosmids as small as 5 kb and introduced them inside P4 capsids. Such cosmids were then recovered as a complex mixture of highly knotted DNA circles. Over 250 μg of knotted cosmid were typically obtained from 1 liter of bacterial culture. Conclusion With this biological system, DNA molecules of varying length and sequence can be shaped into very complex and heterogeneous knotted forms. These molecules can be produced in preparative amounts suitable for systematic studies and applications.

  3. A summary of modulus of elasticity and knot size surveys for laminating grades of lumber

    Science.gov (United States)

    R. W. Wolfe; R. C. Moody

    1981-01-01

    A summary of modulus of elasticity (MOE) and knot data is presented for grades of lumber commonly used to manufacture glued-laminated (glulam) timber by the laminating Industry. Tabulated values represent 30 different studies covering a time span of over 16 years. Statistical estimates of average and near-maximum knot sizes as well as mean and coefficient of variation...

  4. The volume conjecture, perturbative knot invariants, and recursion relations for topological strings

    NARCIS (Netherlands)

    Dijkgraaf, R.; Fuji, H.; Manabe, M.

    2011-01-01

    We study the relation between perturbative knot invariants and the free energies defined by topological string theory on the character variety of the knot. Such a correspondence between SL(2;C) Chern-Simons gauge theory and the topological open string theory was proposed earlier on the basis of the

  5. First report of the root-knot nematode Meloidogyne ethiopica on tomato in Slovenia

    NARCIS (Netherlands)

    Sirca, S.; Urek, G.; Karssen, G.

    2004-01-01

    The root-knot nematode Meloidogyne ethiopica Whitehead originally described from Tanzania is also distributed in South Africa, Zimbabwe, and Ethiopia (3). Although this species is a relatively unknown root-knot nematode, M. ethiopica parasitizes several economical important crops, such as tomato,

  6. Use of gadolinium chloride as a contrast agent for imaging spruce knots by magnetic resonance

    Science.gov (United States)

    Thomas L. Eberhardt; Chi-Leung So; Amy H. Herlihy; Po-Wah So

    2006-01-01

    Treatments of knot-containing spruce wood blocks with a paramagnetic salt, gadolinium (III) chloride, in combination with solvent pretreatments, were evaluated as strategies to enhance the visualization of wood features by magnetic resonance imaging (MRI). Initial experiments with clear wood and excised knot samples showed differences in moisture uptake after...

  7. Characterization of the psoRPM1 gene for resistance to root-knot ...

    African Journals Online (AJOL)

    Several root-knot nematode (Meloidogyne spp.) resistance genes have been discovered in different stone fruit crops. However, none of them has yet been cloned and they were only located on the chromosomes. In this study, a candidate root-knot nematode resistance gene (designated as psoRPM1) was isolated from the ...

  8. Proteomic Mapping of Dental Enamel Matrix from Inbred Mouse Strains: Unraveling Potential New Players in Enamel.

    Science.gov (United States)

    Lima Leite, Aline; Silva Fernandes, Mileni; Charone, Senda; Whitford, Gary Milton; Everett, Eric T; Buzalaf, Marília Afonso Rabelo

    2018-01-01

    Enamel formation is a complex 2-step process by which proteins are secreted to form an extracellular matrix, followed by massive protein degradation and subsequent mineralization. Excessive systemic exposure to fluoride can disrupt this process and lead to a condition known as dental fluorosis. The genetic background influences the responses of mineralized tissues to fluoride, such as dental fluorosis, observed in A/J and 129P3/J mice. The aim of the present study was to map the protein profile of enamel matrix from A/J and 129P3/J strains. Enamel matrix samples were obtained from A/J and 129P3/J mice and analyzed by 2-dimensional electrophoresis and liquid chromatography coupled with mass spectrometry. A total of 120 proteins were identified, and 7 of them were classified as putative uncharacterized proteins and analyzed in silico for structural and functional characterization. An interesting finding was the possibility of the uncharacterized sequence Q8BIS2 being an enzyme involved in the degradation of matrix proteins. Thus, the results provide a comprehensive view of the structure and function for putative uncharacterized proteins found in the enamel matrix that could help to elucidate the mechanisms involved in enamel biomineralization and genetic susceptibility to dental fluorosis. © 2018 S. Karger AG, Basel.

  9. Knot detection in X-ray images of wood planks using dictionary learning

    DEFF Research Database (Denmark)

    Hansson, Nils Mattias; Enescu, Alexandru; Brandt, Sami Sebastian

    2015-01-01

    This paper considers a novel application of x-ray imaging of planks, for the purpose of detecting knots in high quality furniture wood. X-ray imaging allows the detection of knots invisible from the surface to conventional cameras. Our approach is based on texture analysis, or more specifically, ......, discriminative dictionary learning. Experiments show that the knot detection and segmentation can be accurately performed by our approach. This is a promising result and can be directly applied in industrial processing of furniture wood.......This paper considers a novel application of x-ray imaging of planks, for the purpose of detecting knots in high quality furniture wood. X-ray imaging allows the detection of knots invisible from the surface to conventional cameras. Our approach is based on texture analysis, or more specifically...

  10. Filtration of the classical knot concordance group and Casson-Gordon invariants

    Science.gov (United States)

    Kim, Taehee

    2004-09-01

    It is known that if every prime power branched cyclic cover of a knot in S(3) is a homology sphere, then the knot has vanishing Casson-Gordon invariants. We construct infinitely many examples of (topologically) non-slice knots in S(3) whose prime power branched cyclic covers are homology spheres. We show that these knots generate an infinite rank subgroup of scrf_{(1.0)}/scrf_{(1.5)} for which Casson-Gordon invariants vanish in Cochran-Orr-Teichner's filtration of the classical knot concordance group. As a corollary, it follows that Casson-Gordon invariants are not a complete set of obstructions to a second layer of Whitney disks.

  11. Knots on a Torus: A Model of the Elementary Particles

    Directory of Open Access Journals (Sweden)

    Jack S. Avrin

    2012-02-01

    Full Text Available Two knots; just two rudimentary knots, the unknot and the trefoil. That’s all we need to build a model of the elementary particles of physics, one with fermions and bosons, hadrons and leptons, interactions weak and strong and the attributes of spin, isospin, mass, charge, CPT invariance and more. There are no quarks to provide fractional charge, no gluons to sequester them within nucleons and no “colors” to avoid violating Pauli’s principle. Nor do we require the importation of an enigmatic Higgs boson to confer mass upon the particles of our world. All the requisite attributes emerge simply (and relativistically invariant as a result of particle conformation and occupation in and of spacetime itself, a spacetime endowed with the imprimature of general relativity. Also emerging are some novel tools for systemizing the particle taxonomy as governed by the gauge group SU(2 and the details of particle degeneracy as well as connections to Hopf algebra, Dirac theory, string theory, topological quantum field theory and dark matter. One exception: it is found necessary to invoke the munificent geometry of the icosahedron in order to provide, as per the group “flavor” SU(3, a scaffold upon which to organize the well-known three generations—no more, no less—of the particle family tree.

  12. Theobromine Effects on Enamel Surface Microhardness: In Vitro

    OpenAIRE

    Grace Syafira; Rina Permatasari; Nina Wardani

    2013-01-01

    Dental caries is still a dental health problem in Indonesia. Fluoride, one of the dental caries prevention material, but its safety and the danger of fluorosis is still debated. Theobromine is an alkaloid compound contained in cocoa beans. Theobromine is believed to increase enamel microhardness with mineral changes in the enamel superficial layer. Objectives: To determine the influence of theobromine on the enamel surface microhardness. Methods: This study used 40 premolar tooth crown pieces...

  13. Enamelin is critical for ameloblast integrity and enamel ultrastructure formation.

    Directory of Open Access Journals (Sweden)

    Jan C-C Hu

    Full Text Available Mutations in the human enamelin gene cause autosomal dominant hypoplastic amelogenesis imperfecta in which the affected enamel is thin or absent. Study of enamelin knockout NLS-lacZ knockin mice revealed that mineralization along the distal membrane of ameloblast is deficient, resulting in no true enamel formation. To determine the function of enamelin during enamel formation, we characterized the developing teeth of the Enam-/- mice, generated amelogenin-driven enamelin transgenic mouse models, and then introduced enamelin transgenes into the Enam-/- mice to rescue enamel defects. Mice at specific stages of development were subjected to morphologic and structural analysis using β-galactosidase staining, immunohistochemistry, and transmission and scanning electron microscopy. Enamelin expression was ameloblast-specific. In the absence of enamelin, ameloblasts pathology became evident at the onset of the secretory stage. Although the aggregated ameloblasts generated matrix-containing amelogenin, they were not able to create a well-defined enamel space or produce normal enamel crystals. When enamelin is present at half of the normal quantity, enamel was thinner with enamel rods not as tightly arranged as in wild type suggesting that a specific quantity of enamelin is critical for normal enamel formation. Enamelin dosage effect was further demonstrated in transgenic mouse lines over expressing enamelin. Introducing enamelin transgene at various expression levels into the Enam-/- background did not fully recover enamel formation while a medium expresser in the Enam+/- background did. Too much or too little enamelin abolishes the production of enamel crystals and prism structure. Enamelin is essential for ameloblast integrity and enamel formation.

  14. Enamelin Is Critical for Ameloblast Integrity and Enamel Ultrastructure Formation

    Science.gov (United States)

    Hu, Jan C.-C.; Hu, Yuanyuan; Lu, Yuhe; Smith, Charles E.; Lertlam, Rangsiyakorn; Wright, John Timothy; Suggs, Cynthia; McKee, Marc D.; Beniash, Elia; Kabir, M. Enamul; Simmer, James P.

    2014-01-01

    Mutations in the human enamelin gene cause autosomal dominant hypoplastic amelogenesis imperfecta in which the affected enamel is thin or absent. Study of enamelin knockout NLS-lacZ knockin mice revealed that mineralization along the distal membrane of ameloblast is deficient, resulting in no true enamel formation. To determine the function of enamelin during enamel formation, we characterized the developing teeth of the Enam−/− mice, generated amelogenin-driven enamelin transgenic mouse models, and then introduced enamelin transgenes into the Enam−/− mice to rescue enamel defects. Mice at specific stages of development were subjected to morphologic and structural analysis using β-galactosidase staining, immunohistochemistry, and transmission and scanning electron microscopy. Enamelin expression was ameloblast-specific. In the absence of enamelin, ameloblasts pathology became evident at the onset of the secretory stage. Although the aggregated ameloblasts generated matrix-containing amelogenin, they were not able to create a well-defined enamel space or produce normal enamel crystals. When enamelin is present at half of the normal quantity, enamel was thinner with enamel rods not as tightly arranged as in wild type suggesting that a specific quantity of enamelin is critical for normal enamel formation. Enamelin dosage effect was further demonstrated in transgenic mouse lines over expressing enamelin. Introducing enamelin transgene at various expression levels into the Enam−/− background did not fully recover enamel formation while a medium expresser in the Enam+/− background did. Too much or too little enamelin abolishes the production of enamel crystals and prism structure. Enamelin is essential for ameloblast integrity and enamel formation. PMID:24603688

  15. Indentation Damage and Crack Repair in Human Enamel*

    OpenAIRE

    Rivera, C.; Arola, D.; Ossa, A.

    2013-01-01

    Tooth enamel is the hardest and most highly mineralized tissue in the human body. While there have been a number of studies aimed at understanding the hardness and crack growth resistance behavior of this tissue, no study has evaluated if cracks in this tissue undergo repair. In this investigation the crack repair characteristics of young human enamel were evaluated as a function of patient gender and as a function of the distance from the Dentin Enamel Junction (DEJ). Cracks were introduced ...

  16. Special Frits for Direct-On Enamelling of Pipelines

    International Nuclear Information System (INIS)

    Berdzenishvili, I.; Siradze, M.; Erokhin, V.; Kldiashvili, R.

    2010-01-01

    The compositions of low-melting zirconium-strontium frits have been developed for direct-on enamelling of pipes. Owing to the given combination of active cations, toxic fluorine and expensive nickel and lithium were eliminated from glass frit compositions. The enamels were subjected to firing by the induction method. In the synthesized enamels, the optimal complex of properties combining high corrosion-resistant and thermo-mechanic indices, adhesive strength and required specifications was realized. These enamels are recommended for testing on pipelines. (author)

  17. Tooth enamel sample preparation using alkaline treatment in ESR dosimetry

    International Nuclear Information System (INIS)

    Yongzeng, Zhou; Jiadong, Wang; Xiaomei, Jia; Ke, Wu; Jianbo, Cong

    2002-01-01

    Tooth enamel sample preparation using alkaline treatment was studied and compared with traditional mechanical method in this paper. 20 adult teeth were used. Samples were placed into NaOH solution. This method requires 4-5 weeks and the enamel was separated from dentin. Experimental results show that 8M NaOH was appropriate for separating enamel from dentin and that there is no difference in background signal relative intensity between samples prepared by mechanical and by chemical methods. There is also no difference in radiosensitivity between samples prepared by two methods mentioned above. Dose response curve for tooth enamel samples isolated by 8M NaOH solution was obtained

  18. Fluoride uptake from restorative dental materials by human enamel

    International Nuclear Information System (INIS)

    Forsten, L.; Rytoemaa, I.; Anttila, A.; Keinonen, J.

    1976-01-01

    The purpose of the study was to determine the uptake in vitro of fluoride from restorative materials by tooth enamel and whether prior etching of the enamel causes a change of uptake. The outermost layer of the labial surface of extracted canines was removed by grinding and the enamel was covered with five different fluoride-containing materials ; a silicate, a composite resin, an amalgam, a silicophosphate, and a polycarboxylate luting cement. The material was either removed immediately or after storing the tooth in distilled water. The fluoride content was determined using a sensitive physical method based on the 19 F (p, αγ) 16 O reaction. In addition, the fluoride content of enamel after etching for different periods of time and of etched enamel which had been in contact with silicate cement was determined. The mean fluoride content of uncovered interior enamel was 226 parts 10 6 . All materials, except the composite, increased clearly the fluoride content of the underlying enamel. Etching of interior enamel also increased the fluoride values. No difference could be shown in fluoride uptake from silicate and composite resin between etched and unetched enamel. (author)

  19. On the R-curve behavior of human tooth enamel.

    Science.gov (United States)

    Bajaj, Devendra; Arola, Dwayne D

    2009-08-01

    In this study the crack growth resistance behavior and fracture toughness of human tooth enamel were quantified using incremental crack growth measures and conventional fracture mechanics. Results showed that enamel undergoes an increase in crack growth resistance (i.e. rising R-curve) with crack extension from the outer to the inner enamel, and that the rise in toughness is a function of distance from the dentin enamel junction (DEJ). The outer enamel exhibited the lowest apparent toughness (0.67+/-0.12 MPam(0.5)), and the inner enamel exhibited a rise in the growth toughness from 1.13 MPam(0.5)/mm to 3.93 MPam(0.5)/mm. The maximum crack growth resistance at fracture (i.e. fracture toughness (K(c))) ranged from 1.79 to 2.37 MPam(0.5). Crack growth in the inner enamel was accompanied by a host of mechanisms operating from the micro- to the nano-scale. Decussation in the inner enamel promoted crack deflection and twist, resulting in a reduction of the local stress intensity at the crack tip. In addition, extrinsic mechanisms such as bridging by unbroken ligaments of the tissue and the organic matrix promoted crack closure. Microcracking due to loosening of prisms was also identified as an active source of energy dissipation. In summary, the unique microstructure of enamel in the decussated region promotes crack growth toughness that is approximately three times that of dentin and over ten times that of bone.

  20. Mineral composition of enamel from two South African population groups

    Energy Technology Data Exchange (ETDEWEB)

    Retief, D H [University of the Witwatersrand, Johannesburg (South Africa). Dental Research Unit; Turkstra, J [University of Fort Hare, Alice (South Africa). Department of Chemistry; Cleaton-Jones, P E; Biddlecombe, F [Atomic Energy Board, Pelindaba, Pretoria (South Africa). Chemistry Div.

    1979-10-01

    The mineral composition of pooled bulk enamel from Black and White South Africans respectively, resident in the Johannesburg area, was determined by neutron activation analysis and high resolution gamma spectromety. The differences between the concentrations of Ca, Cl, Mg, Na, Br and Co in the enamel of the two population groups were apparently not significant. There was a trend for the concentrations of Al, Ag, Au, Fe, Sb, and Zn to be higher in the enamel from the White subjects and for the concentrations of Mn, Se and Sr to be higher in the enamel from the Black subjects.

  1. Enamel alteration following tooth bleaching and remineralization

    OpenAIRE

    Coceska, Emilija; Gjorgievska, Elizabeta; Coleman, Nichola; Gabric, Dragana; Slipper, Ian J.; Stevanovic, Marija; Nicholson, John

    2015-01-01

    The purpose of this study was to compare the effects of professional tooth whitening agents containing highly concentrated hydrogen peroxide (with and without laser activation), on the enamel surface; and the potential of four different toothpastes to remineralize any alterations.\\ud \\ud The study was performed on 50 human molars, divided in two groups: treated with Opalescence® Boost and Mirawhite® Laser Bleaching. Furthermore, each group was divided into five subgroups, a control one and 4 ...

  2. Microtensile bond strength of enamel after bleaching

    Directory of Open Access Journals (Sweden)

    Andréa Dias Neves Lago

    2013-01-01

    Full Text Available Objective: To evaluate the bond strength of a composite resin to the bovine enamel bleached with 35% hydrogen peroxide. It was used an etching-and-rinse adhesive system employed immediately, 7 and 14 days after the bleaching. Materials and Methods: Twenty bovine teeth were randomly distributed into 4 groups (n = 5, 3 experimental and 1 control. G1: Unbleached + restoration 14 days after storage in artificial saliva (control; G2: Bleached + restoration immediately after bleaching; G3: Bleached + restoration 7 days after bleaching; G4: Bleached + restoration 14 days after bleaching. Their buccal enamel surfaces were flattened, and a 25 mm² (5 × 5 mm area from each one of these regions was outlined so as to standardize the experimental region. Universal hybrid composite resin Filtek™Z350 was inserted into four layers of 1 mm each and photo-activated. The bond strength was quantitatively evaluated by a microtensile test (1.0 mm/min 24 h after the restorative procedures. The failure mode was assessed through scanning electron microscopy (SEM. Results: There was a significant reduction in the bond strength of the restored teeth immediately after the bleaching (G2. There were no significant differences in enamel bond strength between groups G1, G3, and G4. There was a predominance of adhesive and mixed (cohesive + adhesive failure in all groups. Conclusion: The 7-day-period after the end of the bleaching with 35% hydrogen peroxide was enough to achieve the appropriate values of bond strength to the enamel.

  3. Investigation of EPR signals on tooth enamel

    Energy Technology Data Exchange (ETDEWEB)

    Pavlenko, A; Mironova-Ulmane, N; Polakov, M; Riekstina, D [Institute of Solid State Physics, University of Latvia, Riga (Latvia)

    2007-12-15

    Calcified tissues are involved in continues metabolic process in human organism exchanging a number of chemical elements with environment. The rate of biochemical reactions is tissue dependent and the slowest one at the tooth enamel, the most mineralized tissue of human organism. The long time stability and unique chemical composition make tooth enamel suitable for number of application. The assessment of individual radiation dose by Electron Paramagnetic Resonance (EPR) and evaluations of elemental composition by Instrumentation Neutron Activation Analysis (INAA) are the well known procedures where properties of tooth enamel intensively used. The current work is focused on investigation of EPR signals and determination of chemical composition on several teeth samples having different origin. The EPR spectra and INAA element content of milk tooth, caries tooth, and paradantose tooth have been compared to each other. The results showed that the intensity of EPR signal is much higher for the caries tooth than the for paradantose tooth that is in agreement with depleted Ca content.

  4. A comparative study on component volumes from outer to inner dental enamel in relation to enamel tufts.

    Science.gov (United States)

    Setally Azevedo Macena, Marcus; de Alencar e Silva Leite, Maria Luísa; de Lima Gouveia, Cíntia; de Lima, Tamires Alcoforado Sena; Athayde, Priscilla Alves Aguiar; de Sousa, Frederico Barbosa

    2014-06-01

    Dental enamel presents marked mechanical properties gradients from outer to inner enamel, a region lacking component volumes profiles. Tufts, structures of inner enamel, have been shown to play a role in enamel resilience. We aimed at comparing component volumes from inner to outer enamel in relation to enamel tufts. Transversal ground sections from the cervical half of unerupted human third molars (n=10) were prepared and histological points were selected along transversal lines (extending from innermost to outer enamel) traced across tufts and adjacent control areas without tufts. Component volumes were measured at each histological point. Component volumes ranges were: 70.6-98.5% (mineral), 0.02-20.78% (organic), 3.8-9.8% (total water), 3-9% (firmly bound water), and 0.02-3.3% (loosely bound water). Inner enamel presented the lowest mineral volumes and the highest non-mineral volumes. Mineral, water and organic contents differed as a function of the distance from innermost enamel but not between the tuft and control lines. Tufts presented opaqueness in polarizing microscopy (feature of fracture lines). Organic volume gradient correlated with a relatively flat profile of loosely bound water. Inner, but not outer enamel, rehydrated after air-dried enamel was heated to 50°C and re-exposed to room conditions, as predicted by the organic/water gradient profiles. Component volumes vary markedly from outer to inner enamel, but not between areas with or without tufts (that behave like fracture lines under polarizing microscopy). Copyright © 2014 Elsevier Ltd. All rights reserved.

  5. Pseudomonas savastanoi pv. savastanoi: some like it knot.

    Science.gov (United States)

    Ramos, Cayo; Matas, Isabel M; Bardaji, Leire; Aragón, Isabel M; Murillo, Jesús

    2012-12-01

    Pseudomonas savastanoi pv. savastanoi is the causal agent of olive (Olea europaea) knot disease and an unorthodox member of the P. syringae complex, causing aerial tumours instead of the foliar necroses and cankers characteristic of most members of this complex. Olive knot is present wherever olive is grown; although losses are difficult to assess, it is assumed that olive knot is one of the most important diseases of the olive crop. The last century witnessed a large number of scientific articles describing the biology, epidemiology and control of this pathogen. However, most P. savastanoi pv. savastanoi strains are highly recalcitrant to genetic manipulation, which has effectively prevented the pathogen from benefitting from the scientific progress in molecular biology that has elevated the foliar pathogens of the P. syringae complex to supermodels. A number of studies in recent years have made significant advances in the biology, ecology and genetics of P. savastanoi pv. savastanoi, paving the way for the molecular dissection of its interaction with other nonpathogenic bacteria and their woody hosts. The selection of a genetically pliable model strain was soon followed by the development of rapid methods for virulence assessment with micropropagated olive plants and the analysis of cellular interactions with the plant host. The generation of a draft genome of strain NCPPB 3335 and the closed sequence of its three native plasmids has allowed for functional and comparative genomic analyses for the identification of its pathogenicity gene complement. This includes 34 putative type III effector genes and genomic regions, shared with other pathogens of woody hosts, which encode metabolic pathways associated with the degradation of lignin-derived compounds. Now, the time is right to explore the molecular basis of the P. savastanoi pv. savastanoi-olive interaction and to obtain insights into why some pathovars like it necrotic and why some like it knot

  6. Antagonistic Activities of Streptomyces against Root Knot Nematode of Kiwifruit

    Directory of Open Access Journals (Sweden)

    S. Bashiri

    2016-02-01

    Full Text Available Introduction: Iran is among the world leading kiwifruit producers with 2.816 ha cultivated and 31.567 tones production. Plant parasitic nematodes cause damages to a variety of agricultural crops throughout the world. Interest in biological control of nematodes has increased because of the need for alternative methods to fumigant and non-fumigant nematicides and overall improvement of IPM programs. Bacterial species with nematicidal activity have also been used with some success for controlling root-knot diseases, including Streptomyces spp., Serratia spp., Bacillus spp. and Pseudomonas spp. The goal of the current study was to isolate, identify and investigate the potential of local Streptomyces bacteria for controlling and reducing root-knot nematode population in the north of Iran. Materials and Methods: In order to evaluate the effect of antagonistic bacteria on control of root-knot nematode of Kiwifruit, 100 isolates of bacteria were collected from Kiwifruit rhizosphere in the north of Iran and screened for pigmented microorganisms especially Streptomyces by applying standard serial dilution plate technique, using starch casein nitrate agar and glycerol asparagine agar. Morphological characterizations were achieved by the microscopic method. The microscopic characterization was done by cover slip culture method. The mycelium structure, color and arrangement of conidiospore and arthrospore on the mycelium were observed through the oil immersion (100X. The observed structure was compared with Bergey’s Manual of Determinative Bacteriology and the organism was identified. Various biochemical tests performed for the identification of the potent isolates are as follows: casein hydrolysis, starch hydrolysis, urea hydrolysis, esculin hydrolysis, acid production from sugar, NaCl resistance, temperature tolerance. Soil samples (100g were collected, and then processed for nematode egg and larvae extraction Hussey method. The suspension was pipetted

  7. An Indwelling Urethral Catheter Knotted Around a Double-J Ureteral Stent: An Unusual Complication after Kidney Transplantation

    Directory of Open Access Journals (Sweden)

    E. G. Warmerdam

    2011-01-01

    Full Text Available Urethral catheterization is a common procedure with a relatively low complication rate. Knotting of an indwelling urethral catheter is a very rare complication, and there are only a few case reports on knotted catheters, most of them concerning children. We report an especially rare case where a urethral catheter formed a knot around a double-J ureteral stent after a kidney transplantation. We will discuss the various risk factors for knotting of a catheter and the methods to untangle a knot.

  8. Child oral health-related quality of life (COHQoL), enamel defects of the first permanent molars and caries experience among children in Western Australia.

    Science.gov (United States)

    Arrow, P

    2013-09-01

    Published reports suggest that children with enamel defects, especially where enamel is missing or breaking down, experience considerable discomfort and are generally more fearful of dental treatment. However, children's oral health-related quality of life in relation to enamel defects has not been reported. The aim of this study was to examine the association between oral health-related quality of life among children (COHQoL) with enamel defects of the first permanent molars and deciduous caries experience. Children attending pre-primary schools in metropolitan Perth, Western Australia, were recruited and classified for enamel defects using the modified Developmental Defects of Enamel index. Caries experience of deciduous molars and canines was also recorded. Parents completed a child oral health-related quality of life questionnaire. Data were analysed using Kruskal-Wallis, Spearman's rank correlation, chi-square, multiple linear regression and ordered logistic regression to test the factors for their influence on the COHQoL. From the 550 children assessed (mean age 7.2 years) 522 COHQoL questionnaires were returned. Mean COHQoL score was 8.9 (sd 8.8). Bivariate tests showed no association of COHQoL with enamel defect status of the first permanent molars. COHQoL was associated with dmft (mean dmft 1.96, sd 2.62). Higher caries experience children had poorer reported oral health-related quality of life. The presence of enamel defects in the first permanent molars did not affect the children's oral health-related quality of life.

  9. Targeted p120-catenin ablation disrupts dental enamel development.

    Science.gov (United States)

    Bartlett, John D; Dobeck, Justine M; Tye, Coralee E; Perez-Moreno, Mirna; Stokes, Nicole; Reynolds, Albert B; Fuchs, Elaine; Skobe, Ziedonis

    2010-09-16

    Dental enamel development occurs in stages. The ameloblast cell layer is adjacent to, and is responsible for, enamel formation. When rodent pre-ameloblasts become tall columnar secretory-stage ameloblasts, they secrete enamel matrix proteins, and the ameloblasts start moving in rows that slide by one another. This movement is necessary to form the characteristic decussating enamel prism pattern. Thus, a dynamic system of intercellular interactions is required for proper enamel development. Cadherins are components of the adherens junction (AJ), and they span the cell membrane to mediate attachment to adjacent cells. p120 stabilizes cadherins by preventing their internalization and degradation. So, we asked if p120-mediated cadherin stability is important for dental enamel formation. Targeted p120 ablation in the mouse enamel organ had a striking effect. Secretory stage ameloblasts detached from surrounding tissues, lost polarity, flattened, and ameloblast E- and N-cadherin expression became undetectable by immunostaining. The enamel itself was poorly mineralized and appeared to be composed of a thin layer of merged spheres that abraded from the tooth. Significantly, p120 mosaic mouse teeth were capable of forming normal enamel demonstrating that the enamel defects were not a secondary effect of p120 ablation. Surprisingly, blood-filled sinusoids developed in random locations around the developing teeth. This has not been observed in other p120-ablated tissues and may be due to altered p120-mediated cell signaling. These data reveal a critical role for p120 in tooth and dental enamel development and are consistent with p120 directing the attachment and detachment of the secretory stage ameloblasts as they move in rows.

  10. Numerical simulation of the knotted nylon netting panel

    Directory of Open Access Journals (Sweden)

    Li Yuwei

    2016-01-01

    Full Text Available A piece of netting, consists of the 8 8 meshes, fixed on a square frame, was simulated and the tensions and their distribution, the positions of knots and netting shape were calculated by means of MATLAB in computer. The dynamic mathematic model was developed based on lumped mass method, the netting was treated as spring-mass system, the Runge-Kutta fifth-order and sixth-order method was used to solve the differential equations for every step, then the displacement and tension of each mass point were obtained. For verify this model, the tests have been carried out in a flume tank. The results of the numerical simulation fully agreed with the experiments.

  11. Disciplinary Knots and Learning Problems in Waves Physics

    Science.gov (United States)

    Di Renzone, Simone; Frati, Serena; Montalbano, Vera

    An investigation on student understanding of waves is performed during an optional laboratory realized in informal extracurricular way with few, interested and talented pupils. The background and smart intuitions of students rendered the learning path very dynamic and ambitious. The activities started by investigating the basic properties of waves by means of a Shive wave machine. In order to make quantitative observed phenomena, the students used a camcorder and series of measures were obtained from the captured images. By checking the resulting data, it arose some learning difficulties especially in activities related to the laboratory. This experience was the starting point for a further analysis on disciplinary knots and learning problems in the physics of waves in order to elaborate a teaching-learning proposal on this topic.

  12. New knotted solutions of Maxwell's equations

    International Nuclear Information System (INIS)

    Hoyos, Carlos; Sircar, Nilanjan; Sonnenschein, Jacob

    2015-01-01

    In this paper we have further developed the study of topologically non-trivial solutions of vacuum electrodynamics. We have discovered a novel method of generating such solutions by applying conformal transformations with complex parameters on known solutions expressed in terms of Bateman's variables. This has enabled us to obtain a wide class of solutions from the basic configuration, such as constant electromagnetic fields and plane-waves. We have introduced a covariant formulation of Bateman's construction and discussed the conserved charges associated with the conformal group as well as a set of four types of conserved helicities. We have also given a formulation in terms of quaternions. This led to a simple map between the electromagnetic knotted and linked solutions into flat connections of SU(2) gauge theory. We have computed the corresponding Chern–Simons charge in a class of solutions and the charge takes integer values. (paper)

  13. Average size of random polygons with fixed knot topology.

    Science.gov (United States)

    Matsuda, Hiroshi; Yao, Akihisa; Tsukahara, Hiroshi; Deguchi, Tetsuo; Furuta, Ko; Inami, Takeo

    2003-07-01

    We have evaluated by numerical simulation the average size R(K) of random polygons of fixed knot topology K=,3(1),3(1) musical sharp 4(1), and we have confirmed the scaling law R(2)(K) approximately N(2nu(K)) for the number N of polygonal nodes in a wide range; N=100-2200. The best fit gives 2nu(K) approximately 1.11-1.16 with good fitting curves in the whole range of N. The estimate of 2nu(K) is consistent with the exponent of self-avoiding polygons. In a limited range of N (N greater, similar 600), however, we have another fit with 2nu(K) approximately 1.01-1.07, which is close to the exponent of random polygons.

  14. Quantum invariants of knots and 3-manifolds. 2. rev. ed.

    International Nuclear Information System (INIS)

    Turaev, Vladimir G.

    2010-01-01

    Due to the strong appeal and wide use of this monograph, it is now available in its second revised edition. The monograph gives a systematic treatment of 3-dimensional topological quantum field theories (TQFTs) based on the work of the author with N. Reshetikhin and O. Viro. This subject was inspired by the discovery of the Jones polynomial of knots and the Witten-Chern-Simons field theory. On the algebraic side, the study of 3-dimensional TQFTs has been influenced by the theory of braided categories and the theory of quantum groups. The book is divided into three parts. Part I presents a construction of 3-dimensional TQFTs and 2-dimensional modular functors from so-called modular categories. This gives a vast class of knot invariants and 3-manifold invariants as well as a class of linear representations of the mapping class groups of surfaces. In Part II the technique of 6j-symbols is used to define state sum invariants of 3-manifolds. Their relation to the TQFTs constructed in Part I is established via the theory of shadows. Part III provides constructions of modular categories, based on quantum groups and skein modules of tangles in the 3-space. This fundamental contribution to topological quantum field theory is accessible to graduate students in mathematics and physics with knowledge of basic algebra and topology. It is an indispensable source for everyone who wishes to enter the forefront of this fascinating area at the borderline of mathematics and physics. From the contents: - Invariants of graphs in Euclidean 3-space and of closed 3-manifolds - Foundations of topological quantum field theory - Three-dimensional topological quantum field theory - Two-dimensional modular functors - 6j-symbols - Simplicial state sums on 3-manifolds - Shadows of manifolds and state sums on shadows - Constructions of modular categories. (orig.)

  15. HOMFLYPT polynomial is the best quantifier for topological cascades of vortex knots

    Science.gov (United States)

    Ricca, Renzo L.; Liu, Xin

    2018-02-01

    In this paper we derive and compare numerical sequences obtained by adapted polynomials such as HOMFLYPT, Jones and Alexander-Conway for the topological cascade of vortex torus knots and links that progressively untie by a single reconnection event at a time. Two cases are considered: the alternate sequence of knots and co-oriented links (with positive crossings) and the sequence of two-component links with oppositely oriented components (negative crossings). New recurrence equations are derived and sequences of numerical values are computed. In all cases the adapted HOMFLYPT polynomial proves to be the best quantifier for the topological cascade of torus knots and links.

  16. Optical coherence tomography use in the diagnosis of enamel defects

    Science.gov (United States)

    Al-Azri, Khalifa; Melita, Lucia N.; Strange, Adam P.; Festy, Frederic; Al-Jawad, Maisoon; Cook, Richard; Parekh, Susan; Bozec, Laurent

    2016-03-01

    Molar incisor hypomineralization (MIH) affects the permanent incisors and molars, whose undermineralized matrix is evidenced by lesions ranging from white to yellow/brown opacities to crumbling enamel lesions incapable of withstanding normal occlusal forces and function. Diagnosing the condition involves clinical and radiographic examination of these teeth, with known limitations in determining the depth extent of the enamel defects in particular. Optical coherence tomography (OCT) is an emerging hard and soft tissue imaging technique, which was investigated as a new potential diagnostic method in dentistry. A comparison between the diagnostic potential of the conventional methods and OCT was conducted. Compared to conventional imaging methods, OCT gave more information on the structure of the enamel defects as well as the depth extent of the defects into the enamel structure. Different types of enamel defects were compared, each type presenting a unique identifiable pattern when imaged using OCT. Additionally, advanced methods of OCT image analysis including backscattered light intensity profile analysis and enface reconstruction were performed. Both methods confirmed the potential of OCT in enamel defects diagnosis. In conclusion, OCT imaging enabled the identification of the type of enamel defect and the determination of the extent of the enamel defects in MIH with the advantage of being a radiation free diagnostic technique.

  17. Dental enamel defects in children with coeliac disease

    NARCIS (Netherlands)

    Werink, Claar D.; van Diermen, Denise E.; Aartman, Irene H. A.; Heymans, Hugo S. A.

    2007-01-01

    OBJECTIVE: The aim of this study was to investigate whether Dutch children with proven coeliac disease show specific dental enamel defects, and to asses whether children with the same gastrointestinal complaints, but proved no-coeliac disease, lack these specific dental enamel defects. MATERIALS AND

  18. Brief communication: Enamel thickness and durophagy in mangabeys revisited.

    Science.gov (United States)

    McGraw, W Scott; Pampush, James D; Daegling, David J

    2012-02-01

    The documentation of enamel thickness variation across primates is important because enamel thickness has both taxonomic and functional relevance. The Old World monkeys commonly referred to as mangabeys have figured prominently in investigations of feeding ecology and enamel thickness. In this article, we report enamel thickness values for four mangabey taxa (Cercocebus atys, Cercocebus torquatus, Lophocebus aterrimus, and Lophocebus albigena), offer revised interpretation of the significance of thick enamel in papionin evolution, and place our new data in a broader comparative framework. Our data indicate that all mangabeys have thick enamel and that the values obtained for Cercocebus and Lophocebus equal or exceed those published for most extant non-human primates. In addition, new field data combined with a current reading of the dietary literature indicate that hard foods make up a portion of the diet of every mangabey species sampled to date. Clarification on the relationship between diet and enamel thickness among mangabeys is important not only because of recognition that mangabeys are not a natural group but also because of recent arguments that explain thick enamel as an evolved response to the seasonal consumption of hard foods. Copyright © 2011 Wiley Periodicals, Inc.

  19. Human enamel structure studied by high resolution electron microscopy

    International Nuclear Information System (INIS)

    Wen, S.L.

    1989-01-01

    Human enamel structural features are characterized by high resolution electron microscopy. The human enamel consists of polycrystals with a structure similar to Ca10(PO4)6(OH)2. This article describes the structural features of human enamel crystal at atomic and nanometer level. Besides the structural description, a great number of high resolution images are included. Research into the carious process in human enamel is very important for human beings. This article firstly describes the initiation of caries in enamel crystal at atomic and unit-cell level and secondly describes the further steps of caries with structural and chemical demineralization. The demineralization in fact, is the origin of caries in human enamel. The remineralization of carious areas in human enamel has drawn more and more attention as its potential application is realized. This process has been revealed by high resolution electron microscopy in detail in this article. On the other hand, the radiation effects on the structure of human enamel are also characterized by high resolution electron microscopy. In order to reveal this phenomenon clearly, a great number of electron micrographs have been shown, and a physical mechanism is proposed. 26 references

  20. Targeted overexpression of amelotin disrupts the microstructure of dental enamel.

    Science.gov (United States)

    Lacruz, Rodrigo S; Nakayama, Yohei; Holcroft, James; Nguyen, Van; Somogyi-Ganss, Eszter; Snead, Malcolm L; White, Shane N; Paine, Michael L; Ganss, Bernhard

    2012-01-01

    We have previously identified amelotin (AMTN) as a novel protein expressed predominantly during the late stages of dental enamel formation, but its role during amelogenesis remains to be determined. In this study we generated transgenic mice that produce AMTN under the amelogenin (Amel) gene promoter to study the effect of AMTN overexpression on enamel formation in vivo. The specific overexpression of AMTN in secretory stage ameloblasts was confirmed by Western blot and immunohistochemistry. The gross histological appearance of ameloblasts or supporting cellular structures as well as the expression of the enamel proteins amelogenin (AMEL) and ameloblastin (AMBN) was not altered by AMTN overexpression, suggesting that protein production, processing and secretion occurred normally in transgenic mice. The expression of Odontogenic, Ameloblast-Associated (ODAM) was slightly increased in secretory stage ameloblasts of transgenic animals. The enamel in AMTN-overexpressing mice was much thinner and displayed a highly irregular surface structure compared to wild type littermates. Teeth of transgenic animals underwent rapid attrition due to the brittleness of the enamel layer. The microstructure of enamel, normally a highly ordered arrangement of hydroxyapatite crystals, was completely disorganized. Tomes' process, the hallmark of secretory stage ameloblasts, did not form in transgenic mice. Collectively our data demonstrate that the overexpression of amelotin has a profound effect on enamel structure by disrupting the formation of Tomes' process and the orderly growth of enamel prisms.

  1. Role of crystal arrangement on the mechanical performance of enamel.

    Science.gov (United States)

    An, Bingbing; Wang, Raorao; Zhang, Dongsheng

    2012-10-01

    The superior mechanical properties of enamel, such as excellent penetration and crack resistance, are believed to be related to the unique microscopic structure. In this study, the effects of hydroxyapatite (HAP) crystallite orientation on the mechanical behavior of enamel have been investigated through a series of multiscale numerical simulations. A micromechanical model, which considers the HAP crystal arrangement in enamel prisms, the hierarchical structure of HAP crystals and the inelastic mechanical behavior of protein, has been developed. Numerical simulations revealed that, under compressive loading, plastic deformation progression took place in enamel prisms, which is responsible for the experimentally observed post-yield strain hardening. By comparing the mechanical responses for the uniform and non-uniform arrangement of HAP crystals within enamel prisms, it was found that the stiffness for the two cases was identical, while much greater energy dissipation was observed in the enamel with the non-uniform arrangement. Based on these results, we propose an important mechanism whereby the non-uniform arrangement of crystals in enamel rods enhances energy dissipation while maintaining sufficient stiffness to promote fracture toughness, mitigation of fracture and resistance to penetration deformation. Further simulations indicated that the non-uniform arrangement of the HAP crystals is a key factor responsible for the unique mechanical behavior of enamel, while the change in the nanostructure of nanocomposites could dictate the Young's modulus and yield strength of the biocomposite. Copyright © 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  2. Triad 'Metal – Enamel – Glass'

    International Nuclear Information System (INIS)

    Mukhina, T; Petrova, S; Toporova, V; Fedyaeva, T

    2014-01-01

    This article shows how to change the color of metal and glass. Both these materials are self–sufficient, but sometimes used together. For example, enameling. In this case, the adhesion between metal substrate and stekloobraznae enamel layer, which was conducted on a stretching and a bend, was tested

  3. Targeted overexpression of amelotin disrupts the microstructure of dental enamel.

    Directory of Open Access Journals (Sweden)

    Rodrigo S Lacruz

    Full Text Available We have previously identified amelotin (AMTN as a novel protein expressed predominantly during the late stages of dental enamel formation, but its role during amelogenesis remains to be determined. In this study we generated transgenic mice that produce AMTN under the amelogenin (Amel gene promoter to study the effect of AMTN overexpression on enamel formation in vivo. The specific overexpression of AMTN in secretory stage ameloblasts was confirmed by Western blot and immunohistochemistry. The gross histological appearance of ameloblasts or supporting cellular structures as well as the expression of the enamel proteins amelogenin (AMEL and ameloblastin (AMBN was not altered by AMTN overexpression, suggesting that protein production, processing and secretion occurred normally in transgenic mice. The expression of Odontogenic, Ameloblast-Associated (ODAM was slightly increased in secretory stage ameloblasts of transgenic animals. The enamel in AMTN-overexpressing mice was much thinner and displayed a highly irregular surface structure compared to wild type littermates. Teeth of transgenic animals underwent rapid attrition due to the brittleness of the enamel layer. The microstructure of enamel, normally a highly ordered arrangement of hydroxyapatite crystals, was completely disorganized. Tomes' process, the hallmark of secretory stage ameloblasts, did not form in transgenic mice. Collectively our data demonstrate that the overexpression of amelotin has a profound effect on enamel structure by disrupting the formation of Tomes' process and the orderly growth of enamel prisms.

  4. Chymotrypsin C (Caldecrin) Is Associated with Enamel Development

    Science.gov (United States)

    Lacruz, R.S.; Smith, C.E.; Smith, S.M.; Hu, P.; Bringas, P.; Sahin-Tóth, M.; Moradian-Oldak, J.; Paine, M.L.

    2011-01-01

    Two main proteases cleave enamel extracellular matrix proteins during amelogenesis. Matrix metalloprotease-20 (Mmp20) is the predominant enzyme expressed during the secretory stage, while kallikrein-related peptidase-4 (Klk4) is predominantly expressed during maturation. Mutations to both Mmp20 and Klk4 result in abnormal enamel phenotypes. During a recent whole-genome microarray analysis of rat incisor enamel organ cells derived from the secretory and maturation stages of amelogenesis, the serine protease chymotrypsin C (caldecrin, Ctrc) was identified as significantly up-regulated (> 11-fold) during enamel maturation. Prior reports indicate that Ctrc expression is pancreas-specific, albeit low levels were also noted in brain. We here report on the expression of Ctrc in the enamel organ. Quantitative PCR (qPCR) and Western blot analysis were used to confirm the expression of Ctrc in the developing enamel organ. The expression profile of Ctrc is similar to that of Klk4, increasing markedly during the maturation stage relative to the secretory stage, although levels of Ctrc mRNA are lower than for Klk4. The discovery of a new serine protease possibly involved in enamel development has important implications for our understanding of the factors that regulate enamel biomineralization. PMID:21828354

  5. ONLINE TECHNOLOGICAL MONITORING OF INSULATION DEFECTS IN ENAMELED WIRES

    Directory of Open Access Journals (Sweden)

    V. M. Zolotaryov

    2017-08-01

    Full Text Available In this paper the authors used non-destructive technological monitoring of defects insulation enameled wire with poliimid polymer. The paper is devoted to the statistical method for processing, comparison and analysis of results of measurements of parameters of insulation of enameled wire because of mathematical model of trend for application in active technological monitoring is developed; the recommendations for parameters of such monitoring are used. It is theoretically justified and the possibility of determination of dependence of the error on the velocity of movement of a wire for want of quantifying of defects in enameled insulation by non-destructive tests by high voltage. The dependence of average value of amount of defects for enameled wire with two-sheeted poliimid insulation in a range of nominal diameter 0.56 mm is experimentally determined. The technological monitoring purpose is to reduce the quantifying defects of enameled insulation.

  6. Effect of various tooth-whitening products on enamel microhardness.

    Science.gov (United States)

    Grobler, S R; Majeed, A; Moola, M H

    2009-11-01

    The purpose of this in vitro study was to evaluate the effect of various tooth-whitening products containing carbamide peroxide (CP) or hydrogen peroxide (HP), on enamel microhardness. Enamel blocks were exposed to: Nite White ACP 10% CP (Group 2, n=10); Yotuel Patient 10% CP (Group 3, n=10); Opalescence PF 10% CP (Group 4, n=10); Opalescence PF 20% CP (Group 5, n=10); Opalescence Treswhite Supreme 10% HP (Group 6, n=10); Yotuel 10 Minutes 30% CP (Group 7, n=10); Opalescence Quick 45% CP (Group 8, n=10), Yotuel Special 35% HP (Group 9, n=10), Opalescence Boost 38% HP (Group 10, n=10) according to the instructions of the manufacturers. The control (Group 1, n=10) was enamel blocks kept in artificial saliva at 37 degrees C without any treatment. The microhardness values were obtained before exposure and after a 14-day treatment period. Specimens were kept in artificial saliva at 37 degrees C between treatments. Data were analysed using Kruskal-Wallis one-way ANOVA and Tukey-Kramer Multiple Comparison Test. Indent marks on the enamel blocks were also examined under the Scanning Electron Microscope. All whitening products decreased enamel microhardness except group 10 but only Groups 2, 3, 4, 5 and 7 showed significant decrease in enamel microhardness as compared to the control group (p enamel. All products tested in this study decreased enamel microhardness except Opalescence Boost 38% HP. The products containing carbamide peroxide were more damaging to enamel because of the longer application times. Nite White ACP 10% CP showed the highest reduction in enamel microhardness as compared to other products tested.

  7. Keratins as components of the enamel organic matrix

    Science.gov (United States)

    Duverger, Olivier; Beniash, Elia; Morasso, Maria I.

    2016-01-01

    Dental enamel is a hardest tissue in the human body, and although it starts as a tissue rich in proteins, by the time of eruption of the tooth in the oral cavity only a small fraction of the protein remains. While this organic matrix of enamel represents less than 1% by weight it plays essential roles in improving both toughness and resilience to chemical attacks. Despite the fact that the first studies of the enamel matrix began in the 19th century its exact composition and mechanisms of its function remain poorly understood. It was proposed that keratin or a keratin-like primitive epithelial component exists in mature enamel, however due to the extreme insolubility of its organic matrix the presence of keratins there was never clearly established. We have recently identified expression of a number of hair keratins in ameloblasts, the enamel secreting cells, and demonstrated their incorporation into mature enamel. Mutation in epithelial hair keratin KRT75 leads to a skin condition called pseudofollicularis barbae. Carriers of this mutation have an altered enamel structure and mechanical properties. Importantly, these individuals have a much higher prevalence of caries. To the best of our knowledge, this is the first study showing a direct link between a mutation in a protein-coding region of a gene and increased caries rates. In this paper we present an overview of the evidence of keratin-like material in enamel that has accumulated over the last 150 years. Furthermore, we propose potential mechanisms of action of KTR75 in enamel and highlight the clinical implications of the link between mutations in KRT75 and caries. Finally, we discuss the potential use of keratins for enamel repair. PMID:26709044

  8. Indentation damage and mechanical properties of human enamel and dentin.

    Science.gov (United States)

    Xu, H H; Smith, D T; Jahanmir, S; Romberg, E; Kelly, J R; Thompson, V P; Rekow, E D

    1998-03-01

    Understanding the mechanical properties of human teeth is important to clinical tooth preparation and to the development of "tooth-like" restorative materials. Previous studies have focused on the macroscopic fracture behavior of enamel and dentin. In the present study, we performed indentation studies to understand the microfracture and deformation and the microcrack-microstructure interactions of teeth. It was hypothesized that crack propagation would be influenced by enamel rods and the dentino-enamel junction (DEJ), and the mechanical properties would be influenced by enamel rod orientation and tooth-to-tooth variation. Twenty-eight human third molars were used for the measurement of hardness, fracture toughness, elastic modulus, and energy absorbed during indentation. We examined the effect of enamel rod orientation by propagating cracks in the occlusal surface, and in the axial section in directions parallel and perpendicular to the occlusal surface. The results showed that the cracks in the enamel axial section were significantly longer in the direction perpendicular to the occlusal surface than parallel. The cracks propagating toward the DEJ were always arrested and unable to penetrate dentin. The fracture toughness of enamel was not single-valued but varied by a factor of three as a function of enamel rod orientation. The elastic modulus of enamel showed a significant difference between the occlusal surface and the axial section. It is concluded that the cracks strongly interact with the DEJ and the enamel rods, and that the mechanical properties of teeth are functions of microstructural orientations; hence, single values of properties (e.g., a single toughness value or a single modulus value) should not be used without information on microstructural orientation.

  9. Enamel microstructure and microstrain in the fracture of human and pig molar cusps.

    Science.gov (United States)

    Popowics, T E; Rensberger, J M; Herring, S W

    2004-08-01

    The role of microstructure in enamel strain and breakage was investigated in human molar cusps and those of the pig, Sus scrofa. Rosette strain gauges were affixed to cusp surfaces (buccal human M3, n=15, and lingual pig M1, n=13), and a compressive load was applied to individual cusps using an MTS materials testing machine. Load and strain data were recorded simultaneously until cusp fracture, and these data were used to estimate enamel stresses, principal strains, and stiffness. Fractured and polished enamel fragments were examined in multiple planes using scanning electron microscopy (SEM). Human cusp enamel showed greater stiffness than pig enamel (P=0.02), and tensile stress at yield was higher (17.9 N/mm2 in humans versus 8.9 N/mm2 in pigs, P=0.06). SEM revealed enamel rod decussation in both human and pig enamel; however, only pig enamel showed a decussation plane between rod and inter-rod crystallites. Human inter-rod enamel was densely packed between rods, whereas in pig enamel, inter-rod enamel formed partitions between rows of enamel rods. Overall, human enamel structure enabled molar cusps to withstand horizontal tensile stress during both elastic and plastic phases of compressive loading. In contrast, pig cusp enamel was less resistant to horizontal tensile stresses, but appeared to fortify the enamel against crack propagation in multiple directions. These structural and biomechanical differences in cusp enamel are likely to reflect species-level differences in occlusal function.

  10. Gold Enamel Choumps – A Case report

    Directory of Open Access Journals (Sweden)

    Sargam D. Kotecha

    2016-09-01

    Full Text Available Tooth jewellery has been practiced since time immemorial and has become an increasingly popular trend. This case report provides a brief insight into a kind of tooth adornment/a tooth tattoo on the enamel prevalent in parts of western Uttar Pradesh, India locally known as a ‘Choump’. A tooth tattooed with ‘Choumps’ has extremely low incidence and could be used as an identification trait. Tooth adornment with ‘Choumps’ has been reported in adults however, this is the first reported case of ‘Choumps’ in children.

  11. Comparison of shear bond strength between unfilled resin to dry enamel and dentin bonding to moist and dry enamel

    Directory of Open Access Journals (Sweden)

    Yasini E.

    2005-05-01

    Full Text Available Statement of Problem: The use of dentine bondings on enamel and dentin in total etch protocols has recently become popular. Unfilled resin is hydrophobic and dentin bonding is hydrophilic in nature. This chemical difference could be effective in enamel bonding process. Purpose: The aim of this study was to compare the shear bond strength of unfilled resin to dry enamel and dentin bonding to dry and moist enamel. Materials and Methods: In this experimental study, a total of 30 incisor teeth were used. The specimens were randomly assigned to three groups of 10. 37% phosphoric acid etchant was applied to the enamel surfaces in each group for 15 seconds, rinsed with water for 20 seconds and dried for 20 seconds with compressed air in groups one and two. After conditioning, group 1 received unfilled resin (Margin Bond, Colten and group 2 received dentin bonding (Single Bond, 3M and in group 3 after conditioning and rinsing with water, a layer of dentin bonding (Single Bond was applied on wet enamel. The enamel and dentin bonding were light cured for 20 seconds. A ring mold 3.5 mm in diameter and 2 mm height was placed over the specimens to receive the composite filling material (Z100, 3M. The composite was cured for 40 seconds. The specimens were thermocycled and shear bond strengths were determined using an Instron Universal Testing Machine. The findings were analyzed by ANOVA One-Way and Tukey HSD tests. Results: Shear bond strength of dentin bonding to dry enamel was significantly less than unfilled resin to dry enamel (P<0.05. There was no significant difference between the bond strength of dentin bonding to moist and dry enamel. In addition bond strength of dentin bonding to wet enamel was not significantly different from unfilled resin to dry enamel. Conclusion: Based on the findings of this study, it is suggested that enamel surface should remain slightly moist after etching before bonding with single bond but when using unfilled resin, the

  12. Knot numbers used as labels for identifying subject matter of a khipu

    Directory of Open Access Journals (Sweden)

    Alberto Saez-Rodriguez

    2013-03-01

    Full Text Available This investigation presents a new way to look at the numerical khipu, a knotted-string recording device from Pachacamac (Peru, and the types of information it contains. In addition to celestial coordinates, khipu knots apparently pertain to an early form of double-entry accounting. This study hypothesizes that the khipu sample has the recording capacity needed to register double-entry-like accounts. After the identification of its subject matter, the khipu sample was studied in an attempt to ascertain whether the knot values could represent instructions from the Inca state administration to a local accounting center. The results indicate that the numerical information in the pairing quadrants (determined by the distribution of S- and Z-knots should be read from top to bottom along the full length of the string and can then provide certain complementary details regarding the projected corn stocks of the Inca stat

  13. Explicit Gaussian quadrature rules for C^1 cubic splines with symmetrically stretched knot sequence

    KAUST Repository

    Ait-Haddou, Rachid; Barton, Michael; Calo, Victor M.

    2015-01-01

    We provide explicit expressions for quadrature rules on the space of C^1 cubic splines with non-uniform, symmetrically stretched knot sequences. The quadrature nodes and weights are derived via an explicit recursion that avoids an intervention

  14. Effect of soil solarization using plastic mulch in controlling root-knot ...

    African Journals Online (AJOL)

    PRECIOUS

    2009-12-15

    Dec 15, 2009 ... effect of soil solarization using plastic mulch in controlling root-knot nematode infestation and yield of ... addition to their increased toxic effects in the soil over the .... thereby promoting conducive environment for the utiliza- ...

  15. Knotted solutions for linear and nonlinear theories: Electromagnetism and fluid dynamics

    Directory of Open Access Journals (Sweden)

    Daniel W.F. Alves

    2017-10-01

    Full Text Available We examine knotted solutions, the most simple of which is the “Hopfion”, from the point of view of relations between electromagnetism and ideal fluid dynamics. A map between fluid dynamics and electromagnetism works for initial conditions or for linear perturbations, allowing us to find new knotted fluid solutions. Knotted solutions are also found to be solutions of nonlinear generalizations of electromagnetism, and of quantum-corrected actions for electromagnetism coupled to other modes. For null configurations, electromagnetism can be described as a null pressureless fluid, for which we can find solutions from the knotted solutions of electromagnetism. We also map them to solutions of Euler's equations, obtained from a type of nonrelativistic reduction of the relativistic fluid equations.

  16. PRESENCE OF RED KNOT (CALIDRIS CANUTUS) IN ITE WETLANDS, TACNA, PERU

    OpenAIRE

    Jhonson K. Vizcarra

    2012-01-01

    The presence of Red Knot (Calidris canutus, Linnaeus 1758) in Ite Wetlands, Tacna, Peru is documented. Two individuals were observed in October 2011. This species had only one occurrence without details in this area.

  17. Splitting, linking, knotting, and solitonic escape of topological defects in nematic drops with handles.

    Science.gov (United States)

    Tasinkevych, Mykola; Campbell, Michael G; Smalyukh, Ivan I

    2014-11-18

    Topologically nontrivial field excitations, including solitonic, linked, and knotted structures, play important roles in physical systems ranging from classical fluids and liquid crystals, to electromagnetism, classic, and quantum field theories. These excitations can appear spontaneously during symmetry-breaking phase transitions. For example, in cosmological theories, cosmic strings may have formed knotted configurations influencing the Early Universe development, whereas in liquid crystals transient tangled defect lines were observed during isotropic-nematic transitions, eventually relaxing to defect-free states. Knotted and solitonic fields and defects were also obtained using optical manipulation, complex-shaped colloids, and frustrated cholesterics. Here we use confinement of nematic liquid crystal by closed surfaces with varied genus and perpendicular boundary conditions for a robust control of appearance and stability of such field excitations. Theoretical modeling and experiments reveal structure of defect lines as a function of the surface topology and material and geometric parameters, establishing a robust means of controlling solitonic, knotted, linked, and other field excitations.

  18. Potential of Tissue Culture for Breeding Root-Knot Nematode Resistance into Vegetables

    OpenAIRE

    Fassuliotis, G.; Bhatt, D. P.

    1982-01-01

    Plant protoplast technology is being investigated as a means of transferring root-knot nematode resistance factors from Solanum sisymbriifolium into the susceptible S. melongena. Solanum sisymbriifolium plants regenerated from callus lost resistance to Meloidogyne javanica but retained resistance to M. incognita. Tomato plants cloned from leaf discs of the root-knot nematode resistant 'Patriot' were completely susceptible to M. incognita, while sections of stems and leaves rooted in sand in t...

  19. Control of Root-Knot Nematodes on Tomato by the Endoparasitic Fungus Meria coniospora

    OpenAIRE

    Jansson, Hans-Börje; Jeyaprakash, A.; Zuckerman, Bert M.

    1985-01-01

    The endoparasitic nematophagous fungus Meria coniospora reduced root-knot nematode galling on tomatoes in greenhouse pot trials. The fungus was introduced to pots by addition of conidia at several inoculum levels directly to the soil or addition of nematodes infected with M. coniospora to the soil; both methods reduced root galling by root-knot nematodes. These studies represent a part of a recently initiated effort to evaluate the potential of endoparasitic nematophagous fungi for biocontrol...

  20. Knots: attractive places with high path tortuosity in mouse open field exploration.

    Directory of Open Access Journals (Sweden)

    Anna Dvorkin

    2010-01-01

    Full Text Available When introduced into a novel environment, mammals establish in it a preferred place marked by the highest number of visits and highest cumulative time spent in it. Examination of exploratory behavior in reference to this "home base" highlights important features of its organization. It might therefore be fruitful to search for other types of marked places in mouse exploratory behavior and examine their influence on overall behavior.Examination of path curvatures of mice exploring a large empty arena revealed the presence of circumscribed locales marked by the performance of tortuous paths full of twists and turns. We term these places knots, and the behavior performed in them-knot-scribbling. There is typically no more than one knot per session; it has distinct boundaries and it is maintained both within and across sessions. Knots are mostly situated in the place of introduction into the arena, here away from walls. Knots are not characterized by the features of a home base, except for a high speed during inbound and a low speed during outbound paths. The establishment of knots is enhanced by injecting the mouse with saline and placing it in an exposed portion of the arena, suggesting that stress and the arousal associated with it consolidate a long-term contingency between a particular locale and knot-scribbling.In an environment devoid of proximal cues mice mark a locale associated with arousal by twisting and turning in it. This creates a self-generated, often centrally located landmark. The tortuosity of the path traced during the behavior implies almost concurrent multiple views of the environment. Knot-scribbling could therefore function as a way to obtain an overview of the entire environment, allowing re-calibration of the mouse's locale map and compass directions. The rich vestibular input generated by scribbling could improve the interpretation of the visual scene.

  1. Structural color changes in permanent enamel of patients with cleft lip and palate: a case-control study.

    Science.gov (United States)

    Kulas, Antje; Illge, Christina; Bekes, Katrin; Eckert, Alexander W; Fuhrmann, Robert A W; Hirsch, Christian

    2016-01-01

    White spots are more common in patients with cleft lip and palate (CLP) than in the normal population. Whether these are due to the cleft itself or concomitant circumstances (e.g., surgical procedures, orthodontic treatments, systemic fluoridation, increased caries risk) remains unclear. This case-control study evaluated both their prevalence in CLP patients versus control subjects and associated risk factors. A total of 73 CLP patients (average age 8.7 years, range 6-18 years, 42 % male) and a control group of 73 age- and gender-matched non-CLP patients were included. Enamel color changes, subsuming mineralization defects (DDE index), mild dental fluorosis (Dean's index), and initial caries (ICDAS score 2), were recorded. Caries index (dmf-t/DMF-T) scores were also recorded to distinguish between high or low caries risk as defined by the Deutsche Arbeitsgemeinschaft für Jugendzahnpflege criteria. Histories of systemic fluoridation, trauma to primary teeth, surgery, and orthodontic treatment were obtained using a questionnaire. Statistical analysis included t test, χ (2) test, and multivariable logistic regression. Enamel color changes were observed three times more often in the CLP group than in the control group (39.7 vs. 12.3 %; p enamel color changes was associated with CLP itself [OR (odds ratio) 3.6; 95 % confidence interval (CI) 1.3-9.9] and table salt plus tablets combined for systemic fluoridation (OR 2.7, 95 % CI 1.1-6.9). No increased risks were identified for increased caries risk, history of primary-tooth trauma, or history of orthodontic treatment. The higher prevalence of enamel color changes in the CLP group (more than threefold compared to the control group) was not related to previous orthodontic treatments; however, systemic fluoridation (table salt and tablets) constituted a risk factor for the enamel color changes seen in the CLP patients.

  2. Testing functional and morphological interpretations of enamel thickness along the deciduous tooth row in human children.

    OpenAIRE

    Mahoney, Patrick

    2013-01-01

    The significance of a gradient in enamel thickness along the human permanent molar row has been debated in the literature. Some attribute increased enamel thickness from first to third molars to greater bite force during chewing. Others argue that thicker third molar enamel relates to a smaller crown size facilitated by a reduced dentin component. Thus, differences in morphology, not function, explains enamel thickness. This study draws on these different interpretive models to assess enamel ...

  3. Role of Prism Decussation on Fatigue Crack Growth and Fracture of Human Enamel

    OpenAIRE

    Bajaj, Devendra; Arola, Dwayne

    2009-01-01

    The role of prism decussation on the crack growth resistance of human enamel is evaluated. Miniature inset Compact Tension (CT) specimens embodying a section of cuspal enamel were subjected to Mode I cyclic or monotonic loads. Cracks were grown in either the forward (from outer enamel inwards) or reverse (from inner enamel outwards) direction and the responses were compared quantitatively. Results showed that the outer enamel exhibits lower resistance to the inception and growth of cracks. Re...

  4. Knotting and unknotting proteins in the chaperonin cage: Effects of the excluded volume.

    Directory of Open Access Journals (Sweden)

    Szymon Niewieczerzal

    Full Text Available Molecular dynamics simulations are used to explore the effects of chaperonin-like cages on knotted proteins with very low sequence similarity, different depths of a knot but with a similar fold, and the same type of topology. The investigated proteins are VirC2, DndE and MJ0366 with two depths of a knot. A comprehensive picture how encapsulation influences folding rates is provided based on the analysis of different cage sizes and temperature conditions. Neither of these two effects with regard to knotted proteins has been studied by means of molecular dynamics simulations with coarse-grained structure-based models before. We show that encapsulation in a chaperonin is sufficient to self-tie and untie small knotted proteins (VirC2, DndE, for which the equilibrium process is not accessible in the bulk solvent. Furthermore, we find that encapsulation reduces backtracking that arises from the destabilisation of nucleation sites, smoothing the free energy landscape. However, this effect can also be coupled with temperature rise. Encapsulation facilitates knotting at the early stage of folding and can enhance an alternative folding route. Comparison to unknotted proteins with the same fold shows directly how encapsulation influences the free energy landscape. In addition, we find that as the size of the cage decreases, folding times increase almost exponentially in a certain range of cage sizes, in accordance with confinement theory and experimental data for unknotted proteins.

  5. A DECADE-BASELINE STUDY OF THE PLASMA STATES OF EJECTA KNOTS IN CASSIOPEIA A

    Energy Technology Data Exchange (ETDEWEB)

    Rutherford, John; Dewey, Daniel; Figueroa-Feliciano, Enectali; Heine, Sarah N. T.; Canizares, C. R.; Bastien, Fabienne A.; Sato, Kosuke, E-mail: enectali@mit.edu, E-mail: jmrv@mit.edu [Department of Physics and Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States)

    2013-05-20

    We present the analysis of 21 bright X-ray knots in the Cassiopeia A supernova remnant from observations spanning 10 yr. We performed a comprehensive set of measurements to reveal the kinematic and thermal state of the plasma in each knot, using a combined analysis of two high energy resolution High Energy Transmission Grating (HETG) and four medium energy resolution Advanced CCD Imaging Spectrometer (ACIS) sets of spectra. The ACIS electron temperature estimates agree with the HETG-derived values for approximately half of the knots studied, yielding one of the first comparisons between high resolution temperature estimates and ACIS-derived temperatures. We did not observe the expected spectral evolution-predicted from the ionization age and density estimates for each knot-in all but three of the knots studied. The incompatibility of these measurements with our assumptions has led us to propose a dissociated ejecta model, with the metals unmixed inside the knots, which could place strong constraints on supernova mixing models.

  6. Confirming the nature of the knot near the pulsar B1951+32

    Science.gov (United States)

    Zyuzin, D. A.; Shibanov, Yu A.; Pavlov, G. G.; Danilenko, A. A.

    2017-12-01

    The energetic and fast-moving radio and γ-ray pulsar B1951+32 is associated with the supernova remnant CTB 80. It powers a complex pulsar wind nebula detected in the radio, Hα and X-rays (Moon et al 2004 ApJ 610 L33). A puzzling optical knot was detected about 0″.5 from the pulsar in the optical and near-IR (Moon et al 2004 ApJ 610 L33; Hester 2000 Bulletin of the AAS 32 1542). It is reminiscent of the unique “inner optical knot” located 0″.6 from the Crab pulsar. Until now there has been no evidence that B1951+32 knot is indeed associated with the pulsar. We observed the pulsar field with the Gemini-North telescope in 2016 to check the association. We performed first near-IR high spatial resolution imaging in the K s band using the NIRI+Altair instrument and deep optical imaging in the gr bands using the GMOS instrument. Our observations showed that the current knot position is shifted by ≈ 0″.6 from the position measured with the HST in 1997. This is consistent with the known pulsar proper motion and is direct evidence of the pulsar-knot connection. We compared the spectral energy distribution of the knot emission with that of the Crab knot. Possible implications of the results are discussed.

  7. Total curvature and total torsion of knotted random polygons in confinement

    Science.gov (United States)

    Diao, Yuanan; Ernst, Claus; Rawdon, Eric J.; Ziegler, Uta

    2018-04-01

    Knots in nature are typically confined spatially. The confinement affects the possible configurations, which in turn affects the spectrum of possible knot types as well as the geometry of the configurations within each knot type. The goal of this paper is to determine how confinement, length, and knotting affect the total curvature and total torsion of random polygons. Previously published papers have investigated these effects in the unconstrained case. In particular, we analyze how the total curvature and total torsion are affected by (1) varying the length of polygons within a fixed confinement radius and (2) varying the confinement radius of polygons with a fixed length. We also compare the total curvature and total torsion of groups of knots with similar complexity (measured as crossing number). While some of our results fall in line with what has been observed in the studies of the unconfined random polygons, a few surprising results emerge from our study, showing some properties that are unique due to the effect of knotting in confinement.

  8. Freely Expanding Knots of X-Ray-emitting Ejecta in Kepler’s Supernova Remnant

    Science.gov (United States)

    Sato, Toshiki; Hughes, John P.

    2017-08-01

    We report measurements of proper motion, radial velocity, and elemental composition for 14 compact X-ray-bright knots in Kepler’s supernova remnant (SNR) using archival Chandra data. The knots with the highest speed show both large proper motions (μ ˜ 0.″11-0.″14 yr-1) and high radial velocities (v ˜ 8700-10,020 km s-1). For these knots the estimated space velocities (9100 km s-1 ≲ v 3D ≲ 10,400 km s-1) are similar to the typical Si velocity seen in supernovae (SNe) Ia near maximum light. High-speed ejecta knots appear only in specific locations and are morphologically and kinematically distinct from the rest of the ejecta. The proper motions of five knots extrapolate back over the age of Kepler’s SNR to a consistent central position. This new kinematic center agrees well with previous determinations, but is less subject to systematic errors and denotes a location about which several prominent structures in the remnant display a high degree of symmetry. These five knots are expanding at close to the free expansion rate (expansion indices of 0.75 ≲ m ≲ 1.0), which we argue indicates either that they were formed in the explosion with a high density contrast (more than 100 times the ambient density) or that they have propagated through regions of relatively low density (n H ruled out.

  9. Molecular Basis of Human Enamel Defects

    Directory of Open Access Journals (Sweden)

    Chatzopoulos Georgios

    2014-03-01

    Full Text Available During eruption of teeth in the oral cavity, the effect of gene variations and environmental factors can result in morphological and structural changes in teeth. Amelogenesis imperfecta is a failure which is detected on the enamel of the teeth and clinical picture varies by the severity and type of the disease. Classification of the types of amelogenesis imperfecta is determined by histological, genetic, clinical and radiographic criteria. Specifically, there are 4 types of amelogenesis imperfecta (according to Witkop: hypoplastic form, hypo-maturation form, hypo-calcified form, and hypo-maturation/hypoplasia form with taurodontism and 14 subcategories. The diagnosis and classification of amelogenesis imperfecta has traditionally been based on clinical presentation or phenotype and the inheritance pattern. Several genes can be mutated and cause the disease. Millions of genes, possibly more than 10,000 genes produce proteins that regulate synthesis of enamel. Some of the genes and gene products that are likely associated with amelogenesis imperfecta are: amelogenin (AMELX, AMELY genes, ameloblastin (AMBN gene, enamelin (ENAM gene, enamelysin (MMP20 gene, kalikryn 4 (KLK 4 gene, tuftelins (Tuftelin gene, FAM83H (FAM83H gene and WDR72 (WDR72 gene. Particular attention should be given by the dentist in recognition and correlation of phenotypes with genotypes, in order to diagnose quickly and accurately such a possible disease and to prevent or treat it easily and quickly. Modern dentistry should restore these lesions in order to guarantee aesthetics and functionality, usually in collaboration with a group of dentists.

  10. Evaluation of the effect of food and beverages on enamel and restorative materials by SEM and Fourier transform infrared spectroscopy.

    Science.gov (United States)

    Sari, Mustafa Erhan; Erturk, Aliye Gediz; Koyuturk, Alp Erdin; Bekdemir, Yunus

    2014-01-01

    To examine different types of restorative materials used in children as well as primary and permanent teeth enamel when affected by erosive foods. Buttermilk, fruit yoghurt, Coca-cola, fruit juice, Filtek Z-250, Dyract Extra, Fuji II LC, and Fuji IX and tooth enamel were used. Measurements were performed on 1-day, 1-week, 1-month, 3-month, 6-month time periods by using ATR-FTIR technique and surface of the specimens were examined with SEM. Permanent tooth showed the least change among human tooth samples when compared to restorative materials. Among filler materials, the most change was observed in Fuji IX. In terms of beverages the most changes on absorption peaks obtained from spectra were seen on the samples held in Coca-Cola and orange-juice. The exposure of human enamel and restorative materials to acidic drinks may accelerate the degradation process and so reduce the life time of filler materials at equivalent integral exposure times longer than three months. Clinical Relevance Erosive foods and drinks having acidic potential destroy not only tooth enamel but also restorative materials. Copyright © 2013 Wiley Periodicals, Inc.

  11. Enamel Defects Reflect Perinatal Exposure to Bisphenol A

    Science.gov (United States)

    Jedeon, Katia; De la Dure-Molla, Muriel; Brookes, Steven J.; Loiodice, Sophia; Marciano, Clémence; Kirkham, Jennifer; Canivenc-Lavier, Marie-Chantal; Boudalia, Sofiane; Bergès, Raymond; Harada, Hidemitsu; Berdal, Ariane; Babajko, Sylvie

    2014-01-01

    Endocrine-disrupting chemicals (EDCs), including bisphenol A (BPA), are environmental ubiquitous pollutants and associated with a growing health concern. Anecdotally, molar incisor hypomineralization (MIH) is increasing concurrently with EDC-related conditions, which has led us to investigate the effect of BPA on amelogenesis. Rats were exposed daily to BPA from conception until day 30 or 100. At day 30, BPA-affected enamel exhibited hypomineralization similar to human MIH. Scanning electron microscopy and elemental analysis revealed an abnormal accumulation of organic material in erupted enamel. BPA-affected enamel had an abnormal accumulation of exogenous albumin in the maturation stage. Quantitative real-timePCR, Western blotting, and luciferase reporter assays revealed increased expression of enamelin but decreased expression of kallikrein 4 (protease essential for removing enamel proteins) via transcriptional regulation. Data suggest that BPA exerts its effects on amelogenesis by disrupting normal protein removal from the enamel matrix. Interestingly, in 100-day-old rats, erupting incisor enamel was normal, suggesting amelogenesis is only sensitive to MIH-causing agents during a specific time window during development (as reported for human MIH). The present work documents the first experimental model that replicates MIH and presents BPA as a potential causative agent of MIH. Because human enamel defects are irreversible, MIH may provide an easily accessible marker for reporting early EDC exposure in humans. PMID:23764278

  12. Enamel microabrasion: An overview of clinical and scientific considerations

    Science.gov (United States)

    Pini, Núbia Inocencya Pavesi; Sundfeld-Neto, Daniel; Aguiar, Flavio Henrique Baggio; Sundfeld, Renato Herman; Martins, Luis Roberto Marcondes; Lovadino, José Roberto; Lima, Débora Alves Nunes Leite

    2015-01-01

    Superficial stains and irregularities of the enamel are generally what prompt patients to seek dental intervention to improve their smile. These stains or defects may be due to hypoplasia, amelogenesis imperfecta, mineralized white spots, or fluorosis, for which enamel microabrasion is primarily indicated. Enamel microabrasion involves the use of acidic and abrasive agents, such as with 37% phosphoric acid and pumice or 6% hydrochloric acid and silica, applied to the altered enamel surface with mechanical pressure from a rubber cup coupled to a rotatory mandrel of a low-rotation micromotor. If necessary, this treatment can be safely combined with bleaching for better esthetic results. Recent studies show that microabrasion is a conservative treatment when the enamel wear is minimal and clinically imperceptible. The most important factor contributing to the success of enamel microabrasion is the depth of the defect, as deeper, opaque stains, such as those resulting from hypoplasia, cannot be resolved with microabrasion, and require a restorative approach. Surface enamel alterations that result from microabrasion, such as roughness and microhardness, are easily restored by saliva. Clinical studies support the efficacy and longevity of this safe and minimally invasive treatment. The present article presents the clinical and scientific aspects concerning the microabrasion technique, and discusses the indications for and effects of the treatment, including recent works describing microscopic and clinical evaluations. PMID:25610848

  13. DESIGN AND APPLICATION OF TRANSPARENT AND TRANSLUCENT ENAMELS ON ALUMINUM

    Directory of Open Access Journals (Sweden)

    H. AHMADI MOGHADDAM

    2012-09-01

    Full Text Available Transparent and opaque glass enamels for aluminum plates were designed with a minimum or with no heavy atom oxides such as lead and bismuth oxides. The thermal properties of the enamels were studied by DTA and their stability as measured by the difference of glass transition and crystallization onset temperatures was determined. Bending and rapid deformation (impact tests indicated the interfacial adhesion. The enamel/aluminum interfacial qualities were viewed and examined by scanning electron microscopy (SEM. A large amount of NaF and P2O5 in their formulation created opaque enamels. The three methods of melt dipping, pouring, and sintering were used to apply layers of enamels on aluminum plates. The novelty of the pouring and spreading method and its advantages over other methods, were in the use of lower stability and higher melting point enamels, without thermally/mechanically damaging the aluminum. Observations suggested that the interfacial contact and adhesion properties were good, particularly with the transparent or glassy state enamels.

  14. Development of fluorapatite cement for dental enamel defects repair.

    Science.gov (United States)

    Wei, Jie; Wang, Jiecheng; Shan, Wenpeng; Liu, Xiaochen; Ma, Jian; Liu, Changsheng; Fang, Jing; Wei, Shicheng

    2011-06-01

    In order to restore the badly carious lesion of human dental enamel, a crystalline paste of fluoride substituted apatite cement was synthesized by using the mixture of tetracalcium phosphate (TTCP), dicalcium phosphate anhydrous (DCPA) and ammonium fluoride. The apatite cement paste could be directly filled into the enamel defects (cavities) to repair damaged dental enamel. The results indicated that the hardened cement was fluorapatite [Ca(10)(PO(4))(6)F(2), FA] with calcium to phosphorus atom molar ratio (Ca/P) of 1.67 and Ca/F ratio of 5. The solubility of FA cement in Tris-HCl solution (pH = 5) was slightly lower than the natural enamel, indicating the FA cement was much insensitive to the weakly acidic solutions. The FA cement was tightly combined with the enamel surface, and there was no obvious difference of the hardness between the FA cement and natural enamel. The extracts of FA cement caused no cytotoxicity on L929 cells, which satisfied the relevant criterion on dental biomaterials, revealing good cytocompatibility. In addition, the results showed that the FA cement had good mechanical strength, hydrophilicity, and anti-bacterial adhesion properties. The study suggested that using FA cement was simple and promising approach to effectively and conveniently restore enamel defects.

  15. Spatial distribution of the human enamel fracture toughness with aging.

    Science.gov (United States)

    Zheng, Qinghua; Xu, Haiping; Song, Fan; Zhang, Lan; Zhou, Xuedong; Shao, Yingfeng; Huang, Dingming

    2013-10-01

    A better understanding of the fracture toughness (KIC) of human enamel and the changes induced by aging is important for the clinical treatment of teeth cracks and fractures. We conducted microindentation tests and chemical content measurements on molar teeth from "young" (18 ≤ age ≤ 25) and "old" (55 ≤ age) patients. The KIC and the mineral contents (calcium and phosphorus) in the outer, the middle, and the inner enamel layers within the cuspal and the intercuspal regions of the crown were measured through the Vickers toughness test and Energy Dispersive X-Ray Spectroscopy (EDS), respectively. The elastic modulus used for the KIC calculation was measured through atomic force microscope (AFM)-based nanoindentation tests. In the outer enamel layer, two direction-specific values of the KIC were calculated separately (direction I, crack running parallel to the occlusal surface; direction II, perpendicular to direction I). The mean KIC of the outer enamel layer was lower than that of the internal layers (penamel layer, old enamel has a lower KIC, II and higher mineral contents than young enamel (penamel surface becomes more prone to cracks with aging partly due to the reduction in the interprismatic organic matrix observed with the maturation of enamel. Copyright © 2013 Elsevier Ltd. All rights reserved.

  16. Microstructure and hardness of bovine enamel in roselle extract solution

    Science.gov (United States)

    Dame, M. T.; Noerdin, A.; Indrani, D. J.

    2017-08-01

    The aim of this study was to analyze the effect of roselle extract solution on the microstructure and hardness of bovine enamel. Ten bovine teeth and a 5% concentration of roselle extract solution were prepared. Immersions of each bovine tooth in roselle extract solution were conducted up to 60 minutes. The bovine enamel surface was characterized in hardness and microscopy. It was apparent that the initial hardness was 328 KHN, and after immersion in 15 and 60 min, the values decrease to 57.4 KHN and 11 KHN, respectively. Scanning electron microscopy (SEM) revealed changes in enamel rods after immersion in the roselle extract solution.

  17. Chromatographic separation of alkaline phosphatase from dental enamel

    DEFF Research Database (Denmark)

    Moe, D; Kirkeby, S; Salling, E

    1989-01-01

    Alkaline phosphatase (AP) was prepared from partly mineralized bovine enamel by extraction in phosphate buffer, centrifugation and various chromatographic techniques. Chromatofocusing showed that the enamel enzyme possessed five isoelectric points at the acid pH level ranging from pH 5.7 to pH 4.......4. Three enzyme peaks were eluted using low pressure chromatography with a Bio-gel column. With a HPLC gel filtration column the separation of the enamel extract resulted in only one peak with AP activity. The fractions of this peak were used to produce an antibody against bovine AP....

  18. Natural enamel caries in polarized light microscopy: differences in histopathological features derived from a qualitative versus a quantitative approach to interpret enamel birefringence.

    Science.gov (United States)

    De Medeiros, R C G; Soares, J D; De Sousa, F B

    2012-05-01

    Lesion area measurement of enamel caries using polarized light microscopy (PLM) is currently performed in a large number of studies, but measurements are based mainly on a mislead qualitative interpretation of enamel birefringence in a single immersion medium. Here, five natural enamel caries lesions are analysed by microradiography and in PLM, and the differences in their histopathological features derived from a qualitative versus a quantitative interpretation of enamel birefringence are described. Enamel birefringence in different immersion media (air, water and quinoline) is interpreted by both qualitative and quantitative approaches, the former leading to an underestimation of the depth of enamel caries mainly when the criterion of validating sound enamel as a negatively birefringent area in immersion in water is used (a current common practice in dental research). Procedures to avoid the shortcomings of a qualitative interpretation of enamel birefringence are presented and discussed. © 2012 The Authors Journal of Microscopy © 2012 Royal Microscopical Society.

  19. In vitro study of hydroxy apatite and enamel powder fused in human enamel by Nd:YAG laser

    International Nuclear Information System (INIS)

    Ferrreira, Marcus Vinicius Lucas

    2000-01-01

    The aim of this study was to evaluate the effects of pulsed Nd:YAG (1064 nm) laser irradiation on hydroxyapatite and enamel powder fusion. This laser beam is not well absorbed by this two compounds for this reason they were mixed with vegetal coal to increase the absorption of the laser beam. Fifteen enamel flat surfaces and six occlusal enamel surfaces were prepared with three different substances: hydroxyapatite mixed with vegetal coal (3:1 in weigh); enamel powder mixed with vegetal coal (3:1 in weigh); vegetal coal. The occlusal surfaces were utilized to determine if the compounds could seal pits and fissures. Flat surfaces were utilized to determine fusion of hydroxyapatite and enamel powder. All samples were irradiated with Nd:YAG laser with the parameters: 80 mJ, 15 Hz, 1,2 W, 100 μs pulse-width, 131,1 J/cm 2 . Laser beam was delivered to the samples with a 300 μm diameter fiber optic. Morphology of the irradiated surfaces were examined by scanning electron microscopy (SEM). The compounds with hydroxyapatite and enamel powder were fused to enamel surfaces. Only partial pits and fissures sealing could be observed. (author)

  20. The magnetic resonance appearance of surfers' knots: a case report

    Directory of Open Access Journals (Sweden)

    Luke J. McManus, BMBS, PhD

    2016-09-01

    Full Text Available Athletes are at increased risk of developing soft-tissue lesions of the lower limbs. Although the majority of these will be benign, the differential diagnosis is broad and increasingly, doctors are turning to magnetic resonance imaging (MRI as a first-line investigation when presented with these sorts of lesions, both to narrow the differential diagnosis and exclude malignancy. We report the case of a 28-year-old Caucasian man who presented with 2 soft-tissue lesions of the right foot. History and examination of the nodules fitted with a diagnosis of surfers' knots, an unusual form of acquired, benign, connective tissue nodule that may appear over the tibial tuberosities, dorsum of the feet, and occasionally on the chest of surfers in association with repetitive microtrauma during surfing. MRI findings were consistent with this diagnosis with both lesions exhibiting T1 hypointensity and speckled T2 hypointensity with no significant blooming artifact on gradient echo imaging. When imaged with gadolinium, they demonstrated only mild contrast enhancement. MRI is a valuable tool when investigating athletes with soft-tissue lesions over the lower limbs where the possibility of malignancy must be addressed. In selected cases, MRI may be sufficient to permit a conservative approach to the management of these patients.

  1. Quandles and topological pairs symmetry, knots, and cohomology

    CERN Document Server

    Nosaka, Takefumi

    2017-01-01

    This book surveys quandle theory, starting from basic motivations and going on to introduce recent developments of quandles with topological applications and related topics. The book is written from topological aspects, but it illustrates how esteemed quandle theory is in mathematics, and it constitutes a crash course for studying quandles. More precisely, this work emphasizes the fresh perspective that quandle theory can be useful for the study of low-dimensional topology (e.g., knot theory) and relative objects with symmetry. The direction of research is summarized as “We shall thoroughly (re)interpret the previous studies of relative symmetry in terms of the quandle”. The perspectives contained herein can be summarized by the following topics. The first is on relative objects G/H, where G and H are groups, e.g., polyhedrons, reflection, and symmetric spaces. Next, central extensions of groups are discussed, e.g., spin structures, K2 groups, and some geometric anomalies. The third topic is a method to s...

  2. OH+ emission from cometary knots in planetary nebulae

    Science.gov (United States)

    Priestley, F. D.; Barlow, M. J.

    2018-05-01

    We model the molecular emission from cometary knots in planetary nebulae (PNe) using a combination of photoionization and photodissociation region (PDR) codes, for a range of central star properties and gas densities. Without the inclusion of ionizing extreme ultraviolet (EUV) radiation, our models require central star temperatures T* to be near the upper limit of the range investigated in order to match observed H2 and OH+ surface brightnesses consistent with observations - with the addition of EUV flux, our models reproduce observed OH+ surface brightnesses for T* ≥ 100 kK. For T* non-detection of this molecule in PNe with such central star temperatures. Our predicted level of H2 emission is somewhat weaker than commonly observed in PNe, which may be resolved by the inclusion of shock heating or fluorescence due to UV photons. Some of our models also predict ArH+ and HeH+ rotational line emission above detection thresholds, despite neither molecule having been detected in PNe, although the inclusion of photodissociation by EUV photons, which is neglected by our models, would be expected to reduce their detectability.

  3. Feedback in clinical education: untying the Gordian knot.

    Science.gov (United States)

    Weinstein, Debra F

    2015-05-01

    Feedback is essential to clinical education, especially in the era of competencies, milestones, and entrustable professional activities. It is, however, an area where medical educators often fall short. Although educational leaders and faculty supervisors provide feedback in a variety of clinical settings, surveys show important gaps in medical student and resident satisfaction with the feedback received, suggesting lost opportunities to identify performance problems as well as to help each learner reach his or her greatest potential.In this issue of Academic Medicine, Telio and colleagues extend the empirically validated concept of a "therapeutic alliance" to propose the "educational alliance" as a framework for enhancing feedback in medical education. They highlight the importance of source credibility, which depends on the teacher-learner relationship and alignment of values, the teacher's understanding of the learner's role and goals, the teacher's direct observation of the learner, and the learner's perception of the teacher's good intentions. The author of this Commentary suggests that the educational alliance framework should prompt medical educators to reconsider feedback and explore opportunities for optimizing it. Most medical schools and graduate medical education programs are not designed in a way that supports the education alliance model, but the Commentary author offers suggestions for cultivating educational alliances, including rethinking supervisor selection criteria. Such interventions should be combined with ongoing faculty development and efforts to improve coaching and mentoring for students, residents, and fellows. Untying the Gordian knot of effective feedback will require innovative approaches, exchange of successful strategies, and continued research.

  4. Novel Inhibitor Cystine Knot Peptides from Momordica charantia

    Science.gov (United States)

    Clark, Richard J.; Tang, Jun; Zeng, Guang-Zhi; Franco, Octavio L.; Cantacessi, Cinzia; Craik, David J.; Daly, Norelle L.; Tan, Ning-Hua

    2013-01-01

    Two new peptides, MCh-1 and MCh-2, along with three known trypsin inhibitors (MCTI-I, MCTI-II and MCTI-III), were isolated from the seeds of the tropical vine Momordica charantia. The sequences of the peptides were determined using mass spectrometry and NMR spectroscopy. Using a strategy involving partial reduction and stepwise alkylation of the peptides, followed by enzymatic digestion and tandem mass spectrometry sequencing, the disulfide connectivity of MCh-1 was elucidated to be CysI-CysIV, CysII-CysV and CysIII-CysVI. The three-dimensional structures of MCh-1 and MCh-2 were determined using NMR spectroscopy and found to contain the inhibitor cystine knot (ICK) motif. The sequences of the novel peptides differ significantly from peptides previously isolated from this plant. Therefore, this study expands the known peptide diversity in M. charantia and the range of sequences that can be accommodated by the ICK motif. Furthermore, we show that a stable two-disulfide intermediate is involved in the oxidative folding of MCh-1. This disulfide intermediate is structurally homologous to the proposed ancestral fold of ICK peptides, and provides a possible pathway for the evolution of this structural motif, which is highly prevalent in nature. PMID:24116036

  5. Novel inhibitor cystine knot peptides from Momordica charantia.

    Directory of Open Access Journals (Sweden)

    Wen-Jun He

    Full Text Available Two new peptides, MCh-1 and MCh-2, along with three known trypsin inhibitors (MCTI-I, MCTI-II and MCTI-III, were isolated from the seeds of the tropical vine Momordica charantia. The sequences of the peptides were determined using mass spectrometry and NMR spectroscopy. Using a strategy involving partial reduction and stepwise alkylation of the peptides, followed by enzymatic digestion and tandem mass spectrometry sequencing, the disulfide connectivity of MCh-1 was elucidated to be CysI-CysIV, CysII-CysV and CysIII-CysVI. The three-dimensional structures of MCh-1 and MCh-2 were determined using NMR spectroscopy and found to contain the inhibitor cystine knot (ICK motif. The sequences of the novel peptides differ significantly from peptides previously isolated from this plant. Therefore, this study expands the known peptide diversity in M. charantia and the range of sequences that can be accommodated by the ICK motif. Furthermore, we show that a stable two-disulfide intermediate is involved in the oxidative folding of MCh-1. This disulfide intermediate is structurally homologous to the proposed ancestral fold of ICK peptides, and provides a possible pathway for the evolution of this structural motif, which is highly prevalent in nature.

  6. Microtensile Bond Strength of Polyacid-modified Composite Resin to Irradiated Primary Molars.

    Science.gov (United States)

    Keles, Sultan; Yilmaz, Yucel; Sezen, Orhan

    2018-02-01

    This study evaluated the influence of various doses of radiotherapy on the microtensile bond strength (pTBS) of compomer resin to dentin and enamel in primary molars. Thirty-five intact primary molars were collected and divided into seven groups. Teeth were irradiated with doses from 10 to 60 Gy, except for the control group. Compomer restorations were performed, and enamel-compomer resin beams and dentin-compomer resin beams were tested at a crosshead speed of 1 mm/min. No statistically significant difference was found between the irradiated tooth enamel and the control group (F = 1.1468; p = 0.194). However, statistically significant differences were evident among the dentin groups (F = 11.050; p pTBS of compomer resin to primary tooth enamel, but appears to dose dependently decrease its bond strength to primary tooth dentin. Radiotherapy may affect the success rate of compomer fillings in primary teeth, especially in deeper cavities with exposed dentin.

  7. Type VII Collagen is Enriched in the Enamel Organic Matrix Associated with the Dentin-Enamel Junction of Mature Human Teeth

    OpenAIRE

    McGuire, Jacob D.; Walker, Mary P.; Mousa, Ahmad; Wang, Yong; Gorski, Jeff P.

    2014-01-01

    The inner enamel region of erupted teeth is known to exhibit higher fracture toughness and crack growth resistance than bulk phase enamel. However, an explanation for this behavior has been hampered by the lack of compositional information for the residual enamel organic matrix. Since enamel-forming ameloblasts are known to express type VII collagen and type VII collagen null mice display abnormal amelogenesis, the aim of this study was to determine whether type VII collagen is a component of...

  8. Impact of nanohydroxyapatite on enamel surface roughness and color change after orthodontic debonding

    OpenAIRE

    Shabnam Ajami; Hamid Reza Pakshir; Neda Babanouri

    2016-01-01

    Abstract Background The aim of this prospective in vitro study was to evaluate the effect of nanohydroxyapatite (nanoHAP) serum on the enamel surface roughness and tooth color stability after orthodontic debonding procedure. Methods The crowns of 30 premolars were embedded in acrylic blocks with a 4 mm × 5-mm-sized window on the middle third of buccal surfaces. Primary roughness values were evaluated by an atomic force microscope (AFM). After bracket debonding, and polishing procedures, the s...

  9. Bounds for the minimum step number of knots confined to slabs in the simple cubic lattice

    International Nuclear Information System (INIS)

    Ishihara, K; Shimokawa, K; Scharein, R; Arsuaga, J; Vazquez, M; Diao, Y

    2012-01-01

    Volume confinement is a key determinant of the topology and geometry of a polymer. However, the direct relationship between the two is not fully understood. For instance, recent experimental studies have constructed P4 cosmids, i.e. P4 bacteriophages whose genome sequence and length have been artificially engineered and have shown that upon extraction their DNA knot distribution differs from that of wild-type bacteriophage P4. In particular, it was observed that the complexity of the knots decreases sharply with the length of the packed genome. This problem is the motivation of this paper. Here, a polymer is modeled as a self-avoiding polygon on the simple cubic lattice and the confining condition is such that the polygon is bounded between two parallel planes (i.e. bounded within a slab). We estimate the minimum length required for such a polygon to realize a knot type. Our numerical simulations show that in order to realize a prime knot (with up to ten crossings) in a 1-slab (i.e. a slab of height 1), one needs a polygon of length strictly longer than the minimum length needed to realize the same knot when there is no confining condition. In the case of the trefoil knot, we can in fact establish this result analytically by proving that the minimum length required to tie a trefoil in the 1-slab is 26, which is greater than 24, the known minimum length required to tie a trefoil without a confinement condition. Additionally, we find that in the 1-slab not all geometrical realizations of a given knot type are equivalent under BFACF moves. This suggests that in certain confined volumes, knowing the topology of a polymer is not enough to describe all its states. (paper)

  10. Functions of KLK4 and MMP-20 in dental enamel formation

    Science.gov (United States)

    Lu, Yuhe; Papagerakis, Petros; Yamakoshi, Yasuo; Hu, Jan C-C.; Bartlett, John D.; Simmer, James P.

    2009-01-01

    Two proteases are secreted into the enamel matrix of developing teeth. The early protease is enamelysin (MMP-20). The late protease is kallikrein 4 (KLK4). Mutations in MMP20 and KLK4 both cause autosomal recessive amelogenesis imperfecta, a condition featuring soft, porous enamel containing residual protein. MMP-20 is secreted along with enamel proteins by secretory stage ameloblasts. Enamel protein cleavage products accumulate in the space between the crystal ribbons, helping to support them. MMP-20 steadily cleaves accumulated enamel proteins, so their concentration decreases with depth. Kallikrein 4 is secreted by transition and maturation stage ameloblasts. KLK4 aggressively degrades the retained organic matrix following the termination of enamel protein secretion. The principle functions of MMP-20 and KLK4 in dental enamel formation are to facilitate the orderly replacement of organic matrix with mineral, generating an enamel layer that is harder, less porous, and unstained by retained enamel proteins. PMID:18627287

  11. Glass enamel and glass-ceramic coatings for chemical apparatus

    International Nuclear Information System (INIS)

    Es'kov, A.S.; Oleinik, M.I.; Shabrova, E.A.

    1984-01-01

    Among the known anticorrosion coatings used in chemical engineering, glass enamel base coatings are distinguished by such advantages as a high degree of continuity and chemical resistance. The paper describes basic principles for the creation of acid and alkali resistant glass enamel and ceramic coatings for chemical apparatus. As the result of investgations, glass enamel coatings with increased electrical conductivity and also experimental production compositions of chemical, temperature and radiation resistant coatings for protection of chemical equipment of 12Kh18N10T stainless steel have been developed. The coatings have successfully passed testing under service conditions. A new type of coating is short-term glass enamel, which may be recommended for use in chemical machinery manufacturing and other branches of industry in oxidation-free heating and forming of stainless steels

  12. Abrasive wear of enamel by bioactive glass-based toothpastes.

    Science.gov (United States)

    Mahmood, Asad; Mneimne, Mohammed; Zou, Li Fong; Hill, Robert G; Gillam, David G

    2014-10-01

    To determine the abrasivity of a 45S5 bioactive glass based toothpaste on enamel as a function of the particle size and shape of the glass. 45S5 glass was synthesized ground and sieved to give various particle sized fractions toothpastes and their tooth brush abrasivity measured according to BS EN ISO11609 methodology. Enamel loss increased with increasing particle size. The percussion milled powder exhibited particles that had sharp edges and the pastes were significantly more abrasive than the pastes made with round ball milled powders. One interesting observation made during the present study was that there was preferential wear of the enamel at the dentin-enamel junction (DEJ), particularly with the coarse particle sized pastes.

  13. Geographic Variations in the EPR Spectrum of Tooth Enamel

    International Nuclear Information System (INIS)

    Romanyukha, A.A.; Hayes, R.B.; Haskell, E.H.; Kenner, G.H.

    1999-01-01

    The presence of stable radiation-induced radicals in the mineral component of tooth enamel allows use of this material as a biological dosemeter. Estimation of the dose absorbed in tooth enamel can be done by EPR. Generally, for the purpose of dose reconstruction, the EPR spectrum of tooth enamel is interpreted in terms of two main components. The first is a broad background signal often called the native signal centered at a g value of 2.0045. The origin of this signal is not precisely known. The second main component in the tooth enamel spectrum is purely radiation induced and can be used for retrospective dosimetry. Internal structure of the native signal and variations of its amplitude and linewidth were investigated for the samples prepared from modern teeth obtained from different geographic locations (USA and Russia). Possible reasons for the variations observed are discussed as are the potential effects of the variations on the reliability of dose estimation. (author)

  14. Protection of enamel surfaces in the oral cavity

    DEFF Research Database (Denmark)

    Lazovic, Maja Bruvo

    The two main diseases that can affect the tooth enamel are dental caries and dental erosion, which both are caused by exposure of the enamel surfaces to acids. In the case of dental caries, acids from bacterial metabolism cause chemical dissolution of the tooth surface, whereas acids from drinks...... and foodstuffs or gastric juice can cause dental erosion. During a lifetime the enamel surface is also exposed to fluids that can have protective effects against dental caries and erosion such as saliva, various foodstuffs, drinking water and many types of drinks. However, little is still known about simple...... inorganic interactions between different fluids and dental caries and little is also known about which saliva proteins are able to protect the enamel surface against dental erosion. Therefore, the overall aim of this thesis was to examine simple inorganic and protein related protective effects with dental...

  15. In phantom dosimetric response of tooth enamel to neutrons

    International Nuclear Information System (INIS)

    Fattibene, P.; Angelone, M.; Pillon, M.; De Coste, V.

    2004-01-01

    Electron Paramagnetic Resonance dosimetry based on tooth enamel has one important application in dose reconstruction of nuclear plant workers, where the contribution of neutrons to individual dose is often important. Evaluation of tooth enamel response to neutrons is thus an important goal. A few experimental data at thermal and fast neutron energies are available. A first evaluation of the tooth enamel relative response to 60 Co in monoenergetic neutron flux of 2.8 and of 14 MeV, published elsewhere, has provided results apparently non-consistent with the results obtained at lower and higher energies. A comparison of those results in the 2.8 and 14 MeV beams with those available in the literature for other beams is reported and possible reasons for incongruities are discussed. Dose conversion factors of enamel to the water and air are also calculated and reported. (authors)

  16. Femtosecond laser etching of dental enamel for bracket bonding.

    Science.gov (United States)

    Kabas, Ayse Sena; Ersoy, Tansu; Gülsoy, Murat; Akturk, Selcuk

    2013-09-01

    The aim is to investigate femtosecond laser ablation as an alternative method for enamel etching used before bonding orthodontic brackets. A focused laser beam is scanned over enamel within the area of bonding in a saw tooth pattern with a varying number of lines. After patterning, ceramic brackets are bonded and bonding quality of the proposed technique is measured by a universal testing machine. The results are compared to the conventional acid etching method. Results show that bonding strength is a function of laser average power and the density of the ablated lines. Intrapulpal temperature changes are also recorded and observed minimal effects are observed. Enamel surface of the samples is investigated microscopically and no signs of damage or cracking are observed. In conclusion, femtosecond laser exposure on enamel surface yields controllable patterns that provide efficient bonding strength with less removal of dental tissue than conventional acid-etching technique.

  17. Large scale study of tooth enamel

    International Nuclear Information System (INIS)

    Bodart, F.; Deconninck, G.; Martin, M.T.

    Human tooth enamel contains traces of foreign elements. The presence of these elements is related to the history and the environment of the human body and can be considered as the signature of perturbations which occur during the growth of a tooth. A map of the distribution of these traces on a large scale sample of the population will constitute a reference for further investigations of environmental effects. On hundred eighty samples of teeth were first analyzed using PIXE, backscattering and nuclear reaction techniques. The results were analyzed using statistical methods. Correlations between O, F, Na, P, Ca, Mn, Fe, Cu, Zn, Pb and Sr were observed and cluster analysis was in progress. The techniques described in the present work have been developed in order to establish a method for the exploration of very large samples of the Belgian population. (author)

  18. Relationship between enamel bond fatigue durability and surface free-energy characteristics with universal adhesives.

    Science.gov (United States)

    Nagura, Yuko; Tsujimoto, Akimasa; Barkmeier, Wayne W; Watanabe, Hidehiko; Johnson, William W; Takamizawa, Toshiki; Latta, Mark A; Miyazaki, Masashi

    2018-04-01

    The relationship between enamel bond fatigue durability and surface free-energy characteristics with universal adhesives was investigated. The initial shear bond strengths and shear fatigue strengths of five universal adhesives to enamel were determined with and without phosphoric acid pre-etching. The surface free-energy characteristics of adhesive-treated enamel with and without pre-etching were also determined. The initial shear bond strength and shear fatigue strength of universal adhesive to pre-etched enamel were higher than those to ground enamel. The initial shear bond strength and shear fatigue strength of universal adhesive to pre-etched enamel were material dependent, unlike those to ground enamel. The surface free-energy of the solid (γ S ) and the hydrogen-bonding force (γSh) of universal adhesive-treated enamel were different depending on the adhesive, regardless of the presence or absence of pre-etching. The bond fatigue durability of universal adhesives was higher to pre-etched enamel than to ground enamel. In addition, the bond fatigue durability to pre-etched enamel was material dependent, unlike that to ground enamel. The surface free-energy characteristics of universal adhesive-treated enamel were influenced by the adhesive type, regardless of the presence or absence of pre-etching. The surface free-energy characteristics of universal adhesive-treated enamel were related to the results of the bond fatigue durability. © 2018 Eur J Oral Sci.

  19. Microabrasion as treatment of enamel fluorosis

    Directory of Open Access Journals (Sweden)

    Ana Caroline Brito

    2008-01-01

    Full Text Available There is currently a trend in favor of using fluoride as a coadjuvant in reducing caries indexes, as much in underdeveloped as in developedcountries. However, simultaneously the indexes of dental fluorosis seem to grow in an inverse proportion. This is brought about by chronic ingestion of fluoride for a prolonged length of time or in high concentration. Enamel microabrasion is an effective method to remove superficial stains caused by this condition, which affects esthetics of that tissue. The use of 18% hydrochloric acid in association with pumice, despite being a simple and low cost method, has been gradually replaced due to its potential of causing damage to periodontal tissues. Thus, this article reports the treatment of a fluorosis clinical case solved with microabrasion using phosphoric acid 37%, because its costbenefit is supposedly better than with chloridric acid. The deliberate ingestion of toothpaste was the probable cause of the tooth stains. Due to the location of the teeth and to the patient’s smile, only the six upper anterior teeth were selected to receive the proposed treatment. Four clinical sessions, with a seven days interval between each other, were carried out using 37% phosphoric acid and pumice. Under rubber dam isolation, the two first sessions consisted of rubbing the acid-pumice mix on enamel surface using a rubber cup on slow speed, and abrasive paper strips on the interproximal tooth surfaces. On the two final sessions, only finishing touches were performed using a wooden spatula to manually rub the acid-pumice paste.

  20. Influence of Surfactants and Fluoride against Enamel Erosion.

    Science.gov (United States)

    Zanatta, Rayssa Ferreira; Ávila, Daniele Mara da Silva; Miyamoto, Karen Mayumi; Torres, Carlos Rocha Gomes; Borges, Alessandra Bühler

    2018-06-06

    This study investigated the effect of surfactants associated with sodium fluoride (NaF) on enamel erosion prevention, using an erosion-remineralization in vitro model. Sodium lauryl sulfate (SLS), polysorbate 20 (P20), and cocoamidopropyl betaine (CAPB) were tested, at concentrations of 1.0 and 1.5%, and associated or not with NaF (275 ppm). The control groups were distilled water and the NaF solution. Bovine enamel samples (n = 12) were prepared and submitted to a 5-day cycling model: acid challenge (0.3% citric acid, pH 2.6, 4×/day), human saliva (2 h, 4×/day), and the treatment solutions (2 min, 2×/day). The protective potential of the agents against initial erosion was assessed by microhardness and the surface loss by profilometry. Enamel surface wettability was determined by goniometry, protein adsorption was measured by spectroscopy (FTIR), and the KOH-soluble fluoride was quantified. Goniometry showed that SLS and CAPB increased enamel wettability. No differences were found among the surfactants regarding protein adsorption. Microhardness showed that SLS reduced NaF protection. P20 (1 and 1.5%) and CAPB 1.5% presented a protective effect, but lower than the NaF solution. Profilometry showed that CAPB protected enamel, but no agent associated with NaF promoted a higher protection than the NaF solution alone. KOH-soluble fluoride analysis showed that all surfactants reduced the fluoride adsorption on the enamel surface. Therefore, the surfactants tested (except for P20) changed the enamel surface energy. The SLS decreased the protective potential of NaF on initial erosion, but no tested agent interfered with the protective effect of NaF on enamel erosive wear. © 2018 S. Karger AG, Basel.

  1. Enamel: From brittle to ductile like tribological response.

    Science.gov (United States)

    Guidoni, G; Swain, M; Jäger, I

    2008-10-01

    To identify the intrinsic nano-scale wear mechanisms of enamel by comparing it with that of highly brittle glass, and highly ductile copper and silver monocrystals. A sharp cube corner indenter tip (20-50 nm radius) was used to abrade glass, enamel as well as copper and silver monocrystals. Square abraded areas (5 microm x 5 microm, 10 microm x 10 microm) were generated with loads of 50 microN for enamel and 100 microN for the remaining materials (2D abrasion). The normal load and displacement data were utilized in a complementary manner to support the comparison. In addition normal and lateral forces were simultaneously measured along 10 microm single scratched lines (1D abrasion). Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were also used to characterise the worn areas and debris. The sharp tip cuts into and ploughs the specimens creating a wedge or ridge of material ahead of itself which eventually detaches, for the ductile materials and at high loads in enamel. For glass and enamel at low loads, the indenter tip ploughs into the material and the removed material is redistributed and pressed back into the abraded area. The wear behaviour of enamel at the nano-level resembles that obtained with glass at low loads (50 microN) and that obtained with metal mono-crystals at high load (100 microN). The role of the microstructural heterogeneity in the wear behaviour of enamel is considered in the discussion. The relevance to clinical wear of enamel is also considered.

  2. DENTAL ENAMEL FORMATION AND IMPLICATIONS FOR ORAL HEALTH AND DISEASE.

    Science.gov (United States)

    Lacruz, Rodrigo S; Habelitz, Stefan; Wright, J Timothy; Paine, Michael L

    2017-07-01

    Dental enamel is the hardest and most mineralized tissue in extinct and extant vertebrate species and provides maximum durability that allows teeth to function as weapons and/or tools as well as for food processing. Enamel development and mineralization is an intricate process tightly regulated by cells of the enamel organ called ameloblasts. These heavily polarized cells form a monolayer around the developing enamel tissue and move as a single forming front in specified directions as they lay down a proteinaceous matrix that serves as a template for crystal growth. Ameloblasts maintain intercellular connections creating a semi-permeable barrier that at one end (basal/proximal) receives nutrients and ions from blood vessels, and at the opposite end (secretory/apical/distal) forms extracellular crystals within specified pH conditions. In this unique environment, ameloblasts orchestrate crystal growth via multiple cellular activities including modulating the transport of minerals and ions, pH regulation, proteolysis, and endocytosis. In many vertebrates, the bulk of the enamel tissue volume is first formed and subsequently mineralized by these same cells as they retransform their morphology and function. Cell death by apoptosis and regression are the fates of many ameloblasts following enamel maturation, and what cells remain of the enamel organ are shed during tooth eruption, or are incorporated into the tooth's epithelial attachment to the oral gingiva. In this review, we examine key aspects of dental enamel formation, from its developmental genesis to the ever-increasing wealth of data on the mechanisms mediating ionic transport, as well as the clinical outcomes resulting from abnormal ameloblast function. Copyright © 2017 the American Physiological Society.

  3. Indirect veneer treatment of anterior maxillary teeth with enamel hypoplasia

    OpenAIRE

    Juniarti, Devi Eka

    2010-01-01

    Background: Nowadays, aesthetic rehabilitation becomes a necessity. It is affected by patient’s background, especially career, social and economic status. The aesthetic abnormality of anterior teeth i.e discoloration, malposition and malformation can affect patient’s appearance, especially during smile. These dental abnormalities, as a result, can decrease patient’s performance. Dental malformation, for instance, can be caused by developmental tooth defect, such as enamel hypoplasia. Enamel h...

  4. Refining enamel thickness measurements from B-mode ultrasound images.

    Science.gov (United States)

    Hua, Jeremy; Chen, Ssu-Kuang; Kim, Yongmin

    2009-01-01

    Dental erosion has been growing increasingly prevalent with the rise in consumption of heavy starches, sugars, coffee, and acidic beverages. In addition, various disorders, such as Gastroenterological Reflux Disease (GERD), have symptoms of rapid rates of tooth erosion. The measurement of enamel thickness would be important for dentists to assess the progression of enamel loss from all forms of erosion, attrition, and abrasion. Characterizing enamel loss is currently done with various subjective indexes that can be interpreted in different ways by different dentists. Ultrasound has been utilized since the 1960s to determine internal tooth structure, but with mixed results. Via image processing and enhancement, we were able to refine B-mode dental ultrasound images for more accurate enamel thickness measurements. The mean difference between the measured thickness of the occlusal enamel from ultrasound images and corresponding gold standard CT images improved from 0.55 mm to 0.32 mm with image processing (p = 0.033). The difference also improved from 0.62 to 0.53 mm at the buccal/lingual enamel surfaces, but not significantly (p = 0.38).

  5. Separate whitening effects on enamel and dentin after fourteen days.

    Science.gov (United States)

    Kugel, Gerard; Petkevis, Jason; Gurgan, Sevil; Doherty, Eileen

    2007-01-01

    The purpose of this study was to investigate the mechanism of action of a bleaching agent, as it relates to enamel and dentin. Twenty-six extracted human molar teeth were sectioned at the cemento-enamel junction and were randomly assigned to two groups. L*a*b* readings were taken with a spectrophotometer: on buccal surfaces of the crown, at enamel and dentin. The teeth were exposed to carbamide peroxide or placebo gel and L*a*b* scores were again recorded to determine color changes. Treatments were compared using ancova test with baseline color as the covariate. Relative to placebo, buccal surfaces exhibited the greatest Deltab* and DeltaL* color change. On buccal surfaces, the adjusted mean (SE) treatment differences were -7.8 (1.00) for Deltab* and 5.7 (0.97) for DeltaL, with groups differing significantly (p enamel surfaces, treatment differences were -3.6 (0.61) for Deltab* and 4.6 (0.80) for DeltaL* (p tooth crowns exposed to carbamide peroxide 15% was because of the color change in enamel. As compared to enamel, dentin was less affected after 14 days.

  6. Anisotropic properties of the enamel organic extracellular matrix.

    Science.gov (United States)

    do Espírito Santo, Alexandre R; Novaes, Pedro D; Line, Sérgio R P

    2006-05-01

    Enamel biosynthesis is initiated by the secretion, processing, and self-assembly of a complex mixture of proteins. This supramolecular ensemble controls the nucleation of the crystalline mineral phase. The detection of anisotropic properties by polarizing microscopy has been extensively used to detect macromolecular organizations in ordinary histological sections. The aim of this work was to study the birefringence of enamel organic matrix during the development of rat molar and incisor teeth. Incisor and molar teeth of rats were fixed in 2% paraformaldehyde/0.5% glutaraldehyde in 0.2 M phosphate-buffered saline (PBS), pH 7.2, and decalcified in 5% nitric acid/4% formaldehyde. After paraffin embedding, 5-microm-thick sections were obtained, treated with xylene, and hydrated. Form birefringence curves were obtained after measuring optical retardations in imbibing media, with different refractive indices. Our observations showed that enamel organic matrix of rat incisor and molar teeth is strongly birefringent, presenting an ordered supramolecular structure. The birefringence starts during the early secretion phase and disappears at the maturation phase. The analysis of enamel organic matrix birefringence may be used to detect the effects of genetic and environmental factors on the supramolecular orientation of enamel matrix and their effects on the structure of mature enamel.

  7. Theobromine Effects on Enamel Surface Microhardness: In Vitro

    Directory of Open Access Journals (Sweden)

    Grace Syafira

    2013-07-01

    Full Text Available Dental caries is still a dental health problem in Indonesia. Fluoride, one of the dental caries prevention material, but its safety and the danger of fluorosis is still debated. Theobromine is an alkaloid compound contained in cocoa beans. Theobromine is believed to increase enamel microhardness with mineral changes in the enamel superficial layer. Objectives: To determine the influence of theobromine on the enamel surface microhardness. Methods: This study used 40 premolar tooth crown pieces that were embedded in epoxy resin. Furthermore specimens were randomly divided into 4 groups, which were control (distilled water, theobromine 100 mg/L (T100, theobromine 500 mg/L (T500 and theobromine 1000 mg/L (T1000. Specimens were immersed for 15 minutes and microhardness test was performed using Knoop microhardness tester. Results: Increasing enamel microhardness was observed after treatment with four different theobromine concentrations. The highest icreased of enamel microhardness was shown in T1000 group and difference compared to other groups were statistically significant (p<0.05. Conclusion: theobromine is a potential dental caries prevention material due to its effect in improving the microhardness of tooth enamel.

  8. Ca2+ transport and signalling in enamel cells

    Science.gov (United States)

    Nurbaeva, Meerim K.; Eckstein, Miriam; Feske, Stefan

    2016-01-01

    Abstract Dental enamel is one of the most remarkable examples of matrix‐mediated biomineralization. Enamel crystals form de novo in a rich extracellular environment in a stage‐dependent manner producing complex microstructural patterns that are visually stunning. This process is orchestrated by specialized epithelial cells known as ameloblasts which themselves undergo striking morphological changes, switching function from a secretory role to a cell primarily engaged in ionic transport. Ameloblasts are supported by a host of cell types which combined represent the enamel organ. Fully mineralized enamel is the hardest tissue found in vertebrates owing its properties partly to the unique mixture of ionic species represented and their highly organized assembly in the crystal lattice. Among the main elements found in enamel, Ca2+ is the most abundant ion, yet how ameloblasts modulate Ca2+ dynamics remains poorly known. This review describes previously proposed models for passive and active Ca2+ transport, the intracellular Ca2+ buffering systems expressed in ameloblasts and provides an up‐dated view of current models concerning Ca2+ influx and extrusion mechanisms, where most of the recent advances have been made. We also advance a new model for Ca2+ transport by the enamel organ. PMID:27510811

  9. Enamel dose calculation by electron paramagnetic resonance spectral simulation technique

    International Nuclear Information System (INIS)

    Dong Guofu; Cong Jianbo; Guo Linchao; Ning Jing; Xian Hong; Wang Changzhen; Wu Ke

    2011-01-01

    Objective: To optimize the enamel electron paramagnetic resonance (EPR) spectral processing by using the EPR spectral simulation method to improve the accuracy of enamel EPR dosimetry and reduce artificial error. Methods: The multi-component superimposed EPR powder spectral simulation software was developed to simulate EPR spectrum models of the background signal (BS) and the radiation- induced signal (RS) of irradiated enamel respectively. RS was extracted from the multi-component superimposed spectrum of irradiated enamel and its amplitude was calculated. The dose-response curve was then established for calculating the doses of a group of enamel samples. The result of estimated dose was compared with that calculated by traditional method. Results: BS was simulated as a powder spectrum of gaussian line shape with the following spectrum parameters: g=2.00 35 and Hpp=0.65-1.1 mT, RS signal was also simulated as a powder spectrum but with axi-symmetric spectrum characteristics. The spectrum parameters of RS were: g ⊥ =2.0018, g ‖ =1.9965, Hpp=0.335-0.4 mT. The amplitude of RS had a linear response to radiation dose with the regression equation as y=240.74x + 76 724 (R 2 =0.9947). The expectation of relative error of dose estimation was 0.13. Conclusions: EPR simulation method has improved somehow the accuracy and reliability of enamel EPR dose estimation. (authors)

  10. Enamel lesions in development, classification in Costa Rican families

    International Nuclear Information System (INIS)

    Murillo Knudsen, Gina; Berrocal Salazar, Cristina

    2013-01-01

    Enamel lesions in development were identified and classified in patients of Llano Grande de Cartago, examined at the Facultad de Odontologia of the Universidad de Costa Rica. A guide is provided over the topic. 15 children and 2 Costa Rican adults were selected. Clinical examinations, radiographs and clinical photographs were used as data collection method. Dental defects of the enamel were classified according to the possible genetic causes and without genetic causes. Imperfect Amelogenesis (IA) was diagnosed in 10 of patients. Hypoplastic IA was determined in 3 siblings with autosomal recessive inheritance, for 16% of the total sample. Hypomineralized IA was identified in an adult and two of his sons, with autosomal dominant inheritance. The remaining 4 cases of IA have been sporadic. Lesions of dental fluorosis were determined in the Horowitz index in 4 individuals, from 2 unrelated families. Other defects unspecified of the enamel or hypoplasias were found in 3 individuals. Enamel lesions in development should be classified with precision, for the purpose to inform to patients affected about their condition, origin, prognosis and appropriate treatment. The basis are established to implement reliability in the construction of family genealogy, identification and classification of enamel lesions, as well as the probabilities of future generations to express the lesions in the enamel of temporary or permanent dentition [es

  11. Enamel and dentin bond strength following gaseous ozone application.

    Science.gov (United States)

    Cadenaro, Milena; Delise, Chiara; Antoniollo, Francesca; Navarra, Ottavia Chiara; Di Lenarda, Roberto; Breschi, Lorenzo

    2009-08-01

    To evaluate the effects of gaseous ozone application on enamel and dentin bond strength produced by two self-etching adhesive systems. The shear bond strength test was conducted to assess adhesion on enamel (protocol 1), while the microtensile bond strength test was performed on dentin (protocol 2). Protocol 1: 96 bovine incisors were randomly divided into 4 groups, and enamel surfaces were bonded in accordance with the following treatments: (1E) ozone + Clearfil Protect Bond; (2E) Clearfil Protect Bond (control); (3E) ozone + Xeno III; (4E) Xeno III (control). Ozone gas was applied for 80 s. Shear bond strength was measured with a universal testing machine. Protocol 2: 40 noncarious human molars were selected. Middle/deep dentin was exposed and bonded in accordance with the following treatments: (1D) ozone+Clearfil Protect Bond; (2D) Clearfil Protect Bond (control); (3D) ozone+Xeno III (4D) Xeno III (control). Four-mm-thick buildups were built on the adhesives, then specimens were sectioned in accordance with the nontrimming technique. Specimens were stressed until failure occurred, and failure modes were analyzed. Shear bond and microtensile bond strength data were analyzed using two-way ANOVA and Tukey's post-hoc test. No statistical differences were found between ozone treated specimens and controls, neither on enamel nor on dentin irrespective of the tested adhesive. Clearfil Protect Bond showed higher bond strength to enamel than Xeno III, irrespective of the ozone treatment (p enamel and dentin bond strength.

  12. Freely Expanding Knots of X-Ray-emitting Ejecta in Kepler’s Supernova Remnant

    Energy Technology Data Exchange (ETDEWEB)

    Sato, Toshiki [Department of Physics, Tokyo Metropolitan University, 1-1 Minami-Osawa, Hachioji, Tokyo 192-0397 (Japan); Hughes, John P., E-mail: toshiki@astro.isas.jaxa.jp, E-mail: jph@physics.rutgers.edu [Department of Physics and Astronomy, Rutgers University, 136 Frelinghuysen Road, Piscataway, NJ 08854-8019 (United States)

    2017-08-20

    We report measurements of proper motion, radial velocity, and elemental composition for 14 compact X-ray-bright knots in Kepler’s supernova remnant (SNR) using archival Chandra data. The knots with the highest speed show both large proper motions ( μ ∼ 0.″11–0.″14 yr{sup −1}) and high radial velocities ( v ∼ 8700–10,020 km s{sup −1}). For these knots the estimated space velocities (9100 km s{sup −1} ≲ v {sub 3D} ≲ 10,400 km s{sup −1}) are similar to the typical Si velocity seen in supernovae (SNe) Ia near maximum light. High-speed ejecta knots appear only in specific locations and are morphologically and kinematically distinct from the rest of the ejecta. The proper motions of five knots extrapolate back over the age of Kepler’s SNR to a consistent central position. This new kinematic center agrees well with previous determinations, but is less subject to systematic errors and denotes a location about which several prominent structures in the remnant display a high degree of symmetry. These five knots are expanding at close to the free expansion rate (expansion indices of 0.75 ≲ m ≲ 1.0), which we argue indicates either that they were formed in the explosion with a high density contrast (more than 100 times the ambient density) or that they have propagated through regions of relatively low density ( n {sub H} < 0.1 cm{sup −3}) in the ambient medium. X-ray spectral analysis shows that the undecelerated knots have high Si and S abundances, a lower Fe abundance, and very low O abundance, pointing to an origin in the partial Si-burning zone, which occurs in the outer layer of the exploding white dwarf for models of SNe Ia. Other knots show lower speeds and expansion indices consistent with decelerated ejecta knots or features in the ambient medium overrun by the forward shock. Our new accurate location for the explosion site has well-defined positional uncertainties, allowing for a great reduction in the area to be searched for faint

  13. Long-slit spectrophotometry of the multiple knots of the polar ring galaxy IIZw71

    Science.gov (United States)

    Pérez-Montero, E.; García-Benito, R.; Díaz, A. I.; Pérez, E.; Kehrig, C.

    2009-04-01

    Aims: The blue compact dwarf galaxy IIZw71 is catalogued as a probable polar-ring galaxy, and along its long axis it has several very luminous knots showing recent episodes of star formation. Our main aim is to study the physical properties, the stellar content, and the kinematics in the brightest knots of the polar ring. Methods: We carried out long-slit spectroscopic observations of the polar ring in the spectral range 3500-10 000 Å taken with the William Herschel Telescope (WHT). The spectroscopic observations complemented by the available photometry of the galaxy in narrow Hα filters. Results: We measured the rotation curve of the ring, from which we infer a ratio M/LB ≈ 3.9 inside the star-forming ring. We measured the auroral [Oiii] line in the two brightest knots, allowing us to measure oxygen, sulphur, nitrogen, argon, and neon chemical abundances following the direct method. Different empirical calibrators were used to estimate the oxygen abundance in the two faintest knots where the temperature sensitive lines could not be measured. The metallicities obtained are very similar for all the knots, but lower than previously reported in the literature from integrated spectra. The N/O abundance, as derived from the N2O2 parameter (the ratio of the [Nii] and [Oii] intensities), is remarkably constant over the ring, indicating that local polution processes are not conspicuous. Using synthetic stellar populations (SSPs) calculated with the code STARLIGHT, we studied the age distribution of the stellar populations in each knot, finding that in all of them there is a combination of a very young population with less than 10 Myr, responsible for the ionisation of the gas, with other populations older than 100 Myr, probably responsible for the chemical evolution of the knots. The small differences in metallicity and the age distributions among the different knots are indicative of a common chemical evolution, probably related to the process of interaction with the

  14. 360° virtual reality video for the acquisition of knot tying skills: A randomised controlled trial.

    Science.gov (United States)

    Yoganathan, S; Finch, D A; Parkin, E; Pollard, J

    2018-04-10

    360° virtual reality (VR) video is an exciting and evolving field. Current technology promotes a totally immersive, 3-dimensional (3D), 360° experience anywhere in the world using simply a smart phone and virtual reality headset. The potential for its application in the field of surgical education is enormous. The aim of this study was to determine knot tying skills taught with a 360-degree VR video compared to conventional 2D video teaching. This trial was a prospective, randomised controlled study. 40 foundation year doctors (first year postgraduate) were randomised to either the 360-degree VR video (n = 20) or 2D video teaching (n = 20). Participants were given 15 min to watch their allocated video. Ability to tie a single handed reef knot was then assessed against a marking criteria developed for the Royal College of Surgeons, England, (RCSeng) Basic Surgical Skills (BSS) course, by a blinded assessor competent in knot tying. Each candidate then underwent further teaching using Peyton's four step model. Knot tying technique was then re-assessed. Knot tying scores were significantly better in the VR video teaching arm when compared with conventional (median knot score 5.0 vs 4.0 p = 0.04). When used in combination with face to face skills teaching this difference persisted (median knot score 9.5 vs 9.0 p = 0.01). More people in the VR arm constructed a complete reef knot than in the 2D arm following face to face teaching (17/20 vs 12/20). No difference between the groups existed in the time taken to construct a reef knot following video and teaching (median time 31.0s vs 30.5s p = 0.89). This study shows there is significant merit in the application of 360-degree VR video technology in surgical training, both as an independent teaching aid and when used as an adjunct to traditional face to face teaching. Copyright © 2018 IJS Publishing Group Ltd. Published by Elsevier Ltd. All rights reserved.

  15. Combination effect of fluoride dentifrices and varnish on deciduous enamel demineralization

    Directory of Open Access Journals (Sweden)

    Alessandra Gatti

    2011-10-01

    Full Text Available The aim of this study was to evaluate the anticaries potential of 500 or 1100 ppm F dentifrices combined with fluoride varnish using a pH-cycling regimen. Seventy primary canines were covered with nail polish, leaving a 4×4 mm window on their buccal surface, and randomly assigned into 7 groups (n = 10: S: sound enamel not submitted to the pH-cycling regimen or treatment; N: negative control, submitted to the pH-cycling regimen without any treatment; D1 and D2: subjected to the pH-cycling regimen and treated twice daily with 1100 or 500 ppm F dentifrice, respectively; VF: fluoride varnish (subjected to F-varnish before and in the middle of the pH-cycling regimen; and VF+D1 and VF+D2. After 10 days, the teeth were sectioned, and enamel demineralization was assessed by cross-sectional hardness at different distances from the dental surface. Data were analyzed using a two-way ANOVA followed by Tukey's test. Dentifrice with 1100 ppm F and the combination of F-varnish with the dentifrices significantly reduced enamel demineralization compared with the negative control (p 0.05. The effect of combining F-varnish with the dentifrices was not greater than the effect of the dentifrices alone (p < 0.05. The data suggest that the combination of F-varnish with dentifrices containing 500 and 1100 ppm F is not more effective in reducing demineralization in primary teeth than the isolated effect of dentifrice containing 1100 ppm F.

  16. A novel knot selection method for the error-bounded B-spline curve fitting of sampling points in the measuring process

    International Nuclear Information System (INIS)

    Liang, Fusheng; Zhao, Ji; Ji, Shijun; Zhang, Bing; Fan, Cheng

    2017-01-01

    The B-spline curve has been widely used in the reconstruction of measurement data. The error-bounded sampling points reconstruction can be achieved by the knot addition method (KAM) based B-spline curve fitting. In KAM, the selection pattern of initial knot vector has been associated with the ultimate necessary number of knots. This paper provides a novel initial knots selection method to condense the knot vector required for the error-bounded B-spline curve fitting. The initial knots are determined by the distribution of features which include the chord length (arc length) and bending degree (curvature) contained in the discrete sampling points. Firstly, the sampling points are fitted into an approximate B-spline curve Gs with intensively uniform knot vector to substitute the description of the feature of the sampling points. The feature integral of Gs is built as a monotone increasing function in an analytic form. Then, the initial knots are selected according to the constant increment of the feature integral. After that, an iterative knot insertion (IKI) process starting from the initial knots is introduced to improve the fitting precision, and the ultimate knot vector for the error-bounded B-spline curve fitting is achieved. Lastly, two simulations and the measurement experiment are provided, and the results indicate that the proposed knot selection method can reduce the number of ultimate knots available. (paper)

  17. Metabolism in tooth enamel and reliability of retrospective EPR dosimetry connected with Chernobyl accident

    International Nuclear Information System (INIS)

    Brik, A.; Radchuk, V.; Scherbina, O.; Matyash, M.; Gaver, O.

    1996-01-01

    It is shown that the results of retrospective EPR dosimetry by tooth enamel are essentially determined by the fact that tooth enamel is the mineral of biological origin. The structure of tooth enamel, properties of radiation defects and the role of metabolism in tooth enamel are discussed. It is shown that at deep metamorphic modifications tooth enamel don't save information about its radiation history. The reliability and accuracy of retrospective EPR dosimetry are discussed. Because after Chernobyl accident have passed 10 years the application of tooth enamel for reconstruction of doses which are connected with Chernobyl accident need care and additional investigations

  18. [Differential diagnosis of dental enamel focal demineralization and fluorosis by means of spectrophotometry].

    Science.gov (United States)

    Makarova, N E; Vinnichenko, Yu A

    2018-01-01

    The article presents the results of spectrophotometric tooth enamel scanning for differential diagnosis of focal enamel demineralization and fluorosis. Research was conducted in vivo on teeth affected by these diseases. VITA EasyShade spectrophotometer measurements were made on the affected area and on the visually healthy part of enamel. The lightness appeared as the only one differential significant optical characteristics of tooth enamel. Lightness metrics were higher in the case of initial caries than on the healthy part of enamel when these metrics were lower in the case of fluorosis than on the healthy part of enamel.

  19. Prediction of the optimal set of contacts to fold the smallest knotted protein

    Science.gov (United States)

    Dabrowski-Tumanski, P.; Jarmolinska, A. I.; Sulkowska, J. I.

    2015-09-01

    Knotted protein chains represent a new motif in protein folds. They have been linked to various diseases, and recent extensive analysis of the Protein Data Bank shows that they constitute 1.5% of all deposited protein structures. Despite thorough theoretical and experimental investigations, the role of knots in proteins still remains elusive. Nonetheless, it is believed that knots play an important role in mechanical and thermal stability of proteins. Here, we perform a comprehensive analysis of native, shadow-specific and non-native interactions which describe free energy landscape of the smallest knotted protein (PDB id 2efv). We show that the addition of shadow-specific contacts in the loop region greatly enhances folding kinetics, while the addition of shadow-specific contacts along the C-terminal region (H3 or H4) results in a new folding route with slower kinetics. By means of direct coupling analysis (DCA) we predict non-native contacts which also can accelerate kinetics. Next, we show that the length of the C-terminal knot tail is responsible for the shape of the free energy barrier, while the influence of the elongation of the N-terminus is not significant. Finally, we develop a concept of a minimal contact map sufficient for 2efv protein to fold and analyze properties of this protein using this map.

  20. Prediction of the optimal set of contacts to fold the smallest knotted protein

    International Nuclear Information System (INIS)

    Dabrowski-Tumanski, P; Jarmolinska, A I; Sulkowska, J I

    2015-01-01

    Knotted protein chains represent a new motif in protein folds. They have been linked to various diseases, and recent extensive analysis of the Protein Data Bank shows that they constitute 1.5% of all deposited protein structures. Despite thorough theoretical and experimental investigations, the role of knots in proteins still remains elusive. Nonetheless, it is believed that knots play an important role in mechanical and thermal stability of proteins. Here, we perform a comprehensive analysis of native, shadow-specific and non-native interactions which describe free energy landscape of the smallest knotted protein (PDB id 2efv). We show that the addition of shadow-specific contacts in the loop region greatly enhances folding kinetics, while the addition of shadow-specific contacts along the C-terminal region (H3 or H4) results in a new folding route with slower kinetics. By means of direct coupling analysis (DCA) we predict non-native contacts which also can accelerate kinetics. Next, we show that the length of the C-terminal knot tail is responsible for the shape of the free energy barrier, while the influence of the elongation of the N-terminus is not significant. Finally, we develop a concept of a minimal contact map sufficient for 2efv protein to fold and analyze properties of this protein using this map. (paper)

  1. Particle on a torus knot: Constrained dynamics and semi-classical quantization in a magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Das, Praloy, E-mail: praloydasdurgapur@gmail.com; Pramanik, Souvik, E-mail: souvick.in@gmail.com; Ghosh, Subir, E-mail: subirghosh20@gmail.com

    2016-11-15

    Kinematics and dynamics of a particle moving on a torus knot poses an interesting problem as a constrained system. In the first part of the paper we have derived the modified symplectic structure or Dirac brackets of the above model in Dirac’s Hamiltonian framework, both in toroidal and Cartesian coordinate systems. This algebra has been used to study the dynamics, in particular small fluctuations in motion around a specific torus. The spatial symmetries of the system have also been studied. In the second part of the paper we have considered the quantum theory of a charge moving in a torus knot in the presence of a uniform magnetic field along the axis of the torus in a semiclassical quantization framework. We exploit the Einstein–Brillouin–Keller (EBK) scheme of quantization that is appropriate for multidimensional systems. Embedding of the knot on a specific torus is inherently two dimensional that gives rise to two quantization conditions. This shows that although the system, after imposing the knot condition reduces to a one dimensional system, even then it has manifested non-planar features which shows up again in the study of fractional angular momentum. Finally we compare the results obtained from EBK (multi-dimensional) and Bohr–Sommerfeld (single dimensional) schemes. The energy levels and fractional spin depend on the torus knot parameters that specifies its non-planar features. Interestingly, we show that there can be non-planar corrections to the planar anyon-like fractional spin.

  2. Intra-vesical knot of bladder catheter in an extremely low birthweight neonate: A case report

    Directory of Open Access Journals (Sweden)

    Paula M.Y. Tang

    2015-07-01

    Full Text Available Premature and extremely low birth weight (ELBW neonates are at high risk of developing multiple co-morbidities and often require urinary catheterization for various medical indications. Intra-vesical knotting of bladder catheter is a known but uncommon complication of this procedure. We report a case of an ELBW baby boy with a knotted bladder catheter requiring surgical retrieval. After an elective operation for the closure of patent ductus arteriosus, a 4 French urinary catheter was inserted into an ELBW baby boy for urine output monitoring and left in-situ. Resistance was encountered in attempt to remove the urinary catheter. Abdominal X Ray confirmed intra-vesical knotting of the tube. Knot unravelling by interventional radiology was attempted but was unsuccessful. Open extra-peritoneal bladder exploration was performed for the retrieval of the tightly knotted catheter. A 6 French transurethral Foley catheter was inserted for bladder drainage. Upon removal of the Foley's catheter on day 5 post op, the baby was able to void spontaneously. With literature review, we postulated the potential risk factors resulting in this potentially avoidable iatrogenic unusual complication. Recommendations were suggested to avoid further incidences.

  3. Indirect veneer treatment of anterior maxillary teeth with enamel hypoplasia

    Directory of Open Access Journals (Sweden)

    Devi Eka Juniarti

    2010-09-01

    Full Text Available Background: Nowadays, aesthetic rehabilitation becomes a necessity. It is affected by patient’s background, especially career, social and economic status. The aesthetic abnormality of anterior teeth i.e discoloration, malposition and malformation can affect patient’s appearance, especially during smile. These dental abnormalities, as a result, can decrease patient’s performance. Dental malformation, for instance, can be caused by developmental tooth defect, such as enamel hypoplasia. Enamel hypoplasia is a developmental defect caused by the lack of matrix amount which leads to thin and porous enamel. Enamel hypoplasia can also be caused by matrix calcification disturbance starting from the formation and development of enamel matrix causing defect and permanent changes which can occur on one or more tooth. Purpose: The aim of the study is to improve dental discoloration and tooth surface texture on anterior maxillary teeth with enamel hypoplasia by using indirect veneer with porcelain material. Case: A 20 years-old woman with enamel hypoplasia came to the Dental Hospital, Faculty of Dentistry Airlangga University. The patient wanted to improve her anterior maxillary teeth. It is clinically known that there were some opaque white spots (chalky spotted and porous on anterior teeth’s surface. Case management: Indirect veneer with porcelain material had been chosen as a restoration treatment which has excellent aesthetics and strength, and did not cause gingival irritation. As a result, the treatment could improve the confidence of the patient, and could also make their function normal. Conclusion: Indirect veneer is an effective treatment, which can improve patient’s appearance and self confidence.Latar belakang: Saat ini perbaikan estetik menjadi suatu kebutuhan. Kebutuhan akan estetik dipengaruhi latar belakang penderita, terutama karir, status sosial dan ekonomi. Hal ini disebabkan, kelainan estetik seperti diskolorasi, malposisi

  4. Further morphological evidence on South African earliest Homo lower postcanine dentition: Enamel thickness and enamel dentine junction.

    Science.gov (United States)

    Pan, Lei; Dumoncel, Jean; de Beer, Frikkie; Hoffman, Jakobus; Thackeray, John Francis; Duployer, Benjamin; Tenailleau, Christophe; Braga, José

    2016-07-01

    The appearance of the earliest members of the genus Homo in South Africa represents a key event in human evolution. Although enamel thickness and enamel dentine junction (EDJ) morphology preserve important information about hominin systematics and dietary adaptation, these features have not been sufficiently studied with regard to early Homo. We used micro-CT to compare enamel thickness and EDJ morphology among the mandibular postcanine dentitions of South African early hominins (N = 30) and extant Homo sapiens (N = 26), with special reference to early members of the genus Homo. We found that South African early Homo shows a similar enamel thickness distribution pattern to modern humans, although three-dimensional average and relative enamel thicknesses do not distinguish australopiths, early Homo, and modern humans particularly well. Based on enamel thickness distributions, our study suggests that a dietary shift occurred between australopiths and the origin of the Homo lineage. We also observed that South African early Homo postcanine EDJ combined primitive traits seen in australopith molars with derived features observed in modern human premolars. Our results confirm that some dental morphological patterns in later Homo actually occurred early in the Homo lineage, and highlight the taxonomic value of premolar EDJ morphology in hominin species. Copyright © 2016 Elsevier Ltd. All rights reserved.

  5. Wear of human enamel: a quantitative in vitro assessment.

    Science.gov (United States)

    Kaidonis, J A; Richards, L C; Townsend, G C; Tansley, G D

    1998-12-01

    Many factors influence the extent and rate at which enamel wears. Clinical studies in humans are limited by difficulties in the accurate quantification of intra-oral wear and by a lack of control over the oral environment. The purpose of this study was to determine the wear characteristics of human dental enamel under controlled experimental conditions. An electro-mechanical tooth wear machine, in which opposing enamel surfaces of sectioned, extracted teeth were worn under various conditions, was used to simulate tooth grinding or bruxism. Enamel surface wear was quantified by weight to an accuracy of 0.1 mg, with water uptake and loss controlled. The variables considered included the structure and hardness of enamel, facet area, duration of tooth contact, relative speed of opposing surfaces, temperature, load, pH, and the nature of the lubricant. Enamel wear under non-lubricated conditions increased with increasing load over the range of 1.7 to 16.2 kg. The addition of a liquid lubricant (pH = 7) reduced enamel wear up to 6.7 kg, but when the load increased above this threshold, the rate of wear increased dramatically. With the viscosity of the lubricant constant and pH = 3, the rate of wear was further reduced to less than 10% of the non-lubricated rate at 9.95 kg, after which the rate again increased substantially. Under more extreme conditions (pH = 1.2, simulating gastric acids), the wear was excessive under all experimental loads. When saliva was used as a lubricant, the amount of wear was relatively low at 9.95 kg, but rapid wear occurred at 14.2 kg and above. These results indicate that under non-lubricated conditions, enamel wear remains low at high loads due to the dry-lubricating capabilities of fine enamel powder. Under lubricated conditions, low loads with an acidic lubricant lead to little enamel wear, whereas very low pH results in a high rate of wear under all loads.

  6. A quantitative light microscopic study of the odontoblast and subodontoblastic reactions to active and arrested enamel caries without cavitation

    DEFF Research Database (Denmark)

    Bjørndal, L.; Darvann, T.A.; Thylstrup, Anders

    1998-01-01

    Carious lesions, Computerized histomorphology, Dental pulp, Dentine, Enamel, Microradiography, Odontoblast......Carious lesions, Computerized histomorphology, Dental pulp, Dentine, Enamel, Microradiography, Odontoblast...

  7. "Nara" knot for suturing of cleft lip in children to make removal easy

    Directory of Open Access Journals (Sweden)

    Obaidullah

    2006-01-01

    Full Text Available Cleft patients usually go through a lifetime of repeated hospital admissions and multiple procedures. Suture removal at a tender age and on a sensitive area like the lip becomes a challenge for the nursing staff. It is also emotionally demanding on the part of the parents. Hence, in most centres these patients are at least sedated if not anaesthetised. We have been using a simple knot and running prolene material so that undoing of the knot becomes easy and suture removal more or less atraumatic. We would like to share our experience with readers through this article. An analysis of 53 cleft lip repairs has shown that this knot is safe and easily removable.

  8. Sensitivity of root-knot nematodes to gamma irradiation, salinity and plant growth regulator, cycocel

    Energy Technology Data Exchange (ETDEWEB)

    Sweelam, M E [Econ. Entomology Dept., Fac. Agric. Menoufia University Shebin El-Kom, (Egypt)

    1995-10-01

    The experiment was carried out at the experimental station of the faculty of agriculture, Menoufia Univ. To determine the sensitivity of root-knot nematode, Meloidogyne Javanica infecting tomato plants exposed to different doses of gamma irradiation 0,20,40,60,80 Gy, salinity levels 0. 1000, 2000, 4000 ppm and the plant growth regulator cycocel 0,200 ppm. Treated seeds were planted clay pots and salinity levels and cycocel concentrations were applied. Fresh weights and nematode populations were computed 3 months after application. Results indicated that 20 Gy, 1000 ppm salinity and cycocel gave the highest fresh weight of shoots and roots. The developmental stages and egg-laying females of nematode decreased by the increasing of irradiation dose and salinity levels. Root-knot galls decreased with 40 and 60 Gy, while significant increase was observed with 0 and 80 Gy, salinity levels decreased root galls. Cycocel decreased nematode population, egg-lying females and root-knot galls.

  9. Sensitivity of root-knot nematodes to gamma irradiation, salinity and plant growth regulator, cycocel

    International Nuclear Information System (INIS)

    Sweelam, M.E.

    1995-01-01

    The experiment was carried out at the experimental station of the faculty of agriculture, Menoufia Univ. To determine the sensitivity of root-knot nematode, Meloidogyne Javanica infecting tomato plants exposed to different doses of gamma irradiation 0,20,40,60,80 Gy, salinity levels 0. 1000, 2000, 4000 ppm and the plant growth regulator cycocel 0,200 ppm. Treated seeds were planted clay pots and salinity levels and cycocel concentrations were applied. Fresh weights and nematode populations were computed 3 months after application. Results indicated that 20 Gy, 1000 ppm salinity and cycocel gave the highest fresh weight of shoots and roots. The developmental stages and egg-laying females of nematode decreased by the increasing of irradiation dose and salinity levels. Root-knot galls decreased with 40 and 60 Gy, while significant increase was observed with 0 and 80 Gy, salinity levels decreased root galls. Cycocel decreased nematode population, egg-lying females and root-knot galls

  10. Avian influenza virus antibodies in Pacific Coast Red Knots (Calidris canutus rufa)

    Science.gov (United States)

    Johnson, James A.; DeCicco, Lucas H.; Ruthrauff, Daniel R.; Krauss, Scott; Hall, Jeffrey S.

    2014-01-01

    Prevalence of avian influenza virus (AIV) antibodies in the western Atlantic subspecies of Red Knot (Calidris canutus rufa) is among the highest for any shorebird. To assess whether the frequency of detection of AIV antibodies is high for the species in general or restricted only to C. c. rufa, we sampled the northeastern Pacific Coast subspecies of Red Knot (Calidris canutus roselaari) breeding in northwestern Alaska. Antibodies were detected in 90% of adults and none of the chicks sampled. Viral shedding was not detected in adults or chicks. These results suggest a predisposition of Red Knots to AIV infection. High antibody titers to subtypes H3 and H4 were detected, whereas low to intermediate antibody levels were found for subtypes H10 and H11. These four subtypes have previously been detected in shorebirds at Delaware Bay (at the border of New Jersey and Delaware) and in waterfowl along the Pacific Coast of North America.

  11. Food, feeding, and refuelling of Red Knots during northward migration at San Antonio Oeste, Rio Negro, Argentina

    NARCIS (Netherlands)

    Gonzalez, PM; Piersma, T; Verkuil, Y; González, Patricia M.

    1996-01-01

    We studied the food and feeding ecology of Red Knots Calidris canutus rufa on an area of rocky flat, or restinga, near San Antonio Oeste in the northwest of Golfo San Matias, Provincia de Rio Negro, Argentina in March 1992. These Red Knots are on their way north, from ''wintering'' areas in Tierra

  12. Red Knots (Calidris canutus piersmai and C. c. rogersi) depend on a small threatened staging area in Bohai Bay, China

    NARCIS (Netherlands)

    Rogers, Danny I.; Yang, Hong-Yan; Hassell, Chris J.; Boyle, Adrian N.; Rogers, Ken G.; Chen, Bing; Zhang, Zheng-Wang; Piersma, Theunis

    2010-01-01

    We monitored numbers of Red Knots (Calidris canutus) staging in Bohai Bay, China (39 degrees 02'N, 118 degrees 15'E) on northward migration. Knots were identified to subspecies, and we systematically searched for colour-banded birds from the non-breeding grounds. We modelled migratory turnover, and

  13. Being at the right time at the right place: interpreting the annual life cycle of Afro-Siberian red knots

    NARCIS (Netherlands)

    Leyrer, J.

    2011-01-01

    This thesis describes the possible selection pressures acting on survival and, indirectly, on reproduction of Afro-Siberian red knots Calidris canutus canutus while wintering and migrating. Afro-Siberian red knots are long-distance migrants. They travel between the West African wintering areas and

  14. Gaussian quadrature rules for C 1 quintic splines with uniform knot vectors

    KAUST Repository

    Barton, Michael; Ait-Haddou, Rachid; Calo, Victor Manuel

    2017-01-01

    We provide explicit quadrature rules for spaces of C1C1 quintic splines with uniform knot sequences over finite domains. The quadrature nodes and weights are derived via an explicit recursion that avoids numerical solvers. Each rule is optimal, that is, requires the minimal number of nodes, for a given function space. For each of nn subintervals, generically, only two nodes are required which reduces the evaluation cost by 2/32/3 when compared to the classical Gaussian quadrature for polynomials over each knot span. Numerical experiments show fast convergence, as nn grows, to the “two-third” quadrature rule of Hughes et al. (2010) for infinite domains.

  15. Post-breeding migration and connectivity of red knots in the Western Atlantic

    Science.gov (United States)

    Lyons, James E.; Winn, Bradford; Keyes, Timothy; Kalasz, Kevin S.

    2018-01-01

    Red knots (Calidris canutus rufa) have 3 distinct nonbreeding regions: 1 in the southeastern United States and Caribbean, another on the northeast coast of Brazil in the Maranhão region, and a third along the Patagonian coasts of Chile and Argentina. Effective conservation and recovery of this threatened long-distance migrant will require knowledge of population structure, migration ecology, and abundance and distribution throughout the annual cycle. We conducted a stopover population and biogeographic assessment of knots at the Altamaha River Delta, Georgia, an important stopover area in the southeastern United States. We estimated stopover population size and stopover duration during post-breeding migration in 2011 at the Altamaha study area using mark-resight data, and we inferred nonbreeding regions for this stopover population using stable isotope ratios of carbon and nitrogen in feathers, and observations (sightings and captures) during boreal winter from across the hemisphere. With an integrated Bayesian analysis of all these data, we also estimated the number of birds in the southeastern United States and northern Brazil during boreal winter. For mark-resight analyses in Georgia, we made observations of marked individuals during 14 weeks from early August to early November 2011 and detected 814 individually marked birds. We used the Jolly-Seber mark-recapture model and estimated the southbound passage population at approximately 23,400 red knots. In ongoing studies elsewhere, isotope samples were collected from 175 (21%) of the 814 birds detected in our study, and ≥1 sighting or capture record during boreal winter was located in data repositories for 659 birds (81%). Isotopic signatures and boreal winter records indicate that the majority (82–96%) of the birds that stopped at the Altamaha Delta spend the boreal winter in the northern part of the nonbreeding range (southeast USA, Caribbean, and northern Brazil). Knots migrating to the southeastern

  16. Intraurethral knot in a very-low-birth-weight infant: radiological recognition, surgical management and prevention

    International Nuclear Information System (INIS)

    Lodha, Abhay; Ly, Linh; McNamara, Patrick J.; Brindle, Mary; Daneman, Alan

    2005-01-01

    We report a case where a knot developed in a urinary catheter and became lodged within the urethra of a very-low-birth-weight (VLBW) preterm infant. The catheter was removed with the assistance of a urologist. We recommend using caution when placing urinary catheters in VLBW infants and question the appropriateness of feeding tubes as catheters. Recognition on radiographs of malpositioned bladder catheters is vital to the care of these patients. All staff involved in the insertion, maintenance or removal of these catheters should be suitably trained to minimize the risk of knots and related complications. (orig.)

  17. Gaussian quadrature rules for C 1 quintic splines with uniform knot vectors

    KAUST Repository

    Bartoň, Michael

    2017-03-21

    We provide explicit quadrature rules for spaces of C1C1 quintic splines with uniform knot sequences over finite domains. The quadrature nodes and weights are derived via an explicit recursion that avoids numerical solvers. Each rule is optimal, that is, requires the minimal number of nodes, for a given function space. For each of nn subintervals, generically, only two nodes are required which reduces the evaluation cost by 2/32/3 when compared to the classical Gaussian quadrature for polynomials over each knot span. Numerical experiments show fast convergence, as nn grows, to the “two-third” quadrature rule of Hughes et al. (2010) for infinite domains.

  18. DIRECT DETECTION OF THE HELICAL MAGNETIC FIELD GEOMETRY FROM 3D RECONSTRUCTION OF PROMINENCE KNOT TRAJECTORIES

    Energy Technology Data Exchange (ETDEWEB)

    Zapiór, Maciej; Martinez-Gómez, David, E-mail: zapior.maciek@gmail.com [Physics Department, University of the Balearic Islands, Cra. de Valldemossa, km 7.5. Palma (Illes Balears), E-07122 (Spain)

    2016-02-01

    Based on the data collected by the Vacuum Tower Telescope located in the Teide Observatory in the Canary Islands, we analyzed the three-dimensional (3D) motion of so-called knots in a solar prominence of 2014 June 9. Trajectories of seven knots were reconstructed, giving information of the 3D geometry of the magnetic field. Helical motion was detected. From the equipartition principle, we estimated the lower limit of the magnetic field in the prominence to ≈1–3 G and from the Ampère’s law the lower limit of the electric current to ≈1.2 × 10{sup 9} A.

  19. Direct Detection of the Helical Magnetic Field Geometry from 3D Reconstruction of Prominence Knot Trajectories

    Science.gov (United States)

    Zapiór, Maciej; Martínez-Gómez, David

    2016-02-01

    Based on the data collected by the Vacuum Tower Telescope located in the Teide Observatory in the Canary Islands, we analyzed the three-dimensional (3D) motion of so-called knots in a solar prominence of 2014 June 9. Trajectories of seven knots were reconstructed, giving information of the 3D geometry of the magnetic field. Helical motion was detected. From the equipartition principle, we estimated the lower limit of the magnetic field in the prominence to ≈1-3 G and from the Ampère’s law the lower limit of the electric current to ≈1.2 × 109 A.

  20. Knotting probabilities after a local strand passage in unknotted self-avoiding polygons

    International Nuclear Information System (INIS)

    Szafron, M L; Soteros, C E

    2011-01-01

    We investigate, both theoretically and numerically, the knotting probabilities after a local strand passage is performed in an unknotted self-avoiding polygon (SAP) on the simple cubic lattice. In the polygons studied, it is assumed that two polygon segments have already been brought close together for the purpose of performing a strand passage. This restricts the polygons considered to those that contain a specific pattern called Θ at a fixed location; an unknotted polygon containing Θ is called a Θ-SAP. It is proved that the number of n-edge Θ-SAPs grows exponentially (with n) at the same rate as the total number of n-edge unknotted SAPs (those with no prespecified strand passage structure). Furthermore, it is proved that the same holds for subsets of n-edge Θ-SAPs that yield a specific after-strand-passage knot-type. Thus, the probability of a given after-strand-passage knot-type does not grow (or decay) exponentially with n. Instead, it is conjectured that these after-strand-passage knot probabilities approach, as n goes to infinity, knot-type dependent amplitude ratios lying strictly between 0 and 1. This conjecture is supported by numerical evidence from Monte Carlo data generated using a composite (aka multiple) Markov chain Monte Carlo BFACF algorithm developed to study Θ-SAPs. A new maximum likelihood method is used to estimate the critical exponents relevant to this conjecture. We also obtain strong numerical evidence that the after-strand-passage knotting probability depends on the local structure around the strand-passage site. If the local structure and the crossing sign at the strand-passage site are considered, then we observe that the more 'compact' the local structure, the less likely the after-strand-passage polygon is to be knotted. This trend for compactness versus knotting probability is consistent with results obtained for other strand-passage models; however, we are the first to note the influence of the crossing-sign information. We

  1. Developmental Defects of Enamel : an increasing reality in the everyday practice

    Directory of Open Access Journals (Sweden)

    Fabrizio Guerra

    2014-09-01

    Full Text Available Developmental defects of enamel (DDE are daily encountered in clinical practice. DDE are alteration in quality and quantity of the enamel, caused by disruption and/or damage to the enamel organ during the amelogenesis process. Several clinical indices have been developed to categorize enamel defects based on their nature, appearance, microscopic features or their cause. The aetiology of DDE is not completely clear. Enamel fluorosis is a hypo-mineralization of enamel characterised by subsurface porosity as a result of excess fluoride intake during the period of enamel formation. Several types of treatment have been reported, related to the degree of enamel defect. Correct diagnosis according to lesion depth and prognosis of the technique are fundamental factors in the treatment decision-making process.

  2. Innovative Approaches to Regenerate Enamel and Dentin

    Directory of Open Access Journals (Sweden)

    Xanthippi Chatzistavrou

    2012-01-01

    Full Text Available The process of tooth mineralization and the role of molecular control of cellular behavior during embryonic tooth development have attracted much attention the last few years. The knowledge gained from the research in these fields has improved the general understanding about the formation of dental tissues and the entire tooth and set the basis for teeth regeneration. Tissue engineering using scaffold and cell aggregate methods has been considered to produce bioengineered dental tissues, while dental stem/progenitor cells, which can differentiate into dental cell lineages, have been also introduced into the field of tooth mineralization and regeneration. Some of the main strategies for making enamel, dentin, and complex tooth-like structures are presented in this paper. However, there are still significant barriers that obstruct such strategies to move into the regular clinic practice, and these should be overcome in order to have the regenerative dentistry as the important mean that can treat the consequences of tooth-related diseases.

  3. Bonding strategies for MIH-affected enamel and dentin.

    Science.gov (United States)

    Krämer, Norbert; Bui Khac, Ngoc-Han Nana; Lücker, Susanne; Stachniss, Vitus; Frankenberger, Roland

    2018-02-01

    Aim of the present study was to evaluate resin composite adhesion to dental hard tissues affected by molar incisor hypomineralisation (MIH). 94 freshly extracted human molars and incisors (53 suffering MIH) were used. 68 teeth (35 with MIH) were used for μ-TBS tests in enamel and dentin, 26 (18 with MIH) for qualitative evaluation. Specimens were bonded with Clearfil SE Bond, Scotchbond Universal, and OptiBond FL. For MIH affected enamel, additional OptiBond FL groups with NaOCl and NaOCl+Icon were investigated. Beside fractographic analysis, also qualitative evaluations were performed using SEM at different magnifications as well as histological sectioning. Highest μ-TBS values were recorded with dentin specimens (ANOVA, mod. LSD, p0.05). Pre-test failures did not occur in dentin specimens. Sound enamel specimens exhibited significantly higher μ-TBS values than MIH enamel (p0.05), however, it caused less pre-test failures (pMIH enamel is the limiting factor in adhesion to MIH teeth. MIH-affected dentin may be bonded conventionally. Copyright © 2017 The Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  4. Year of birth determination using radiocarbon dating of dental enamel.

    Science.gov (United States)

    Buchholz, B A; Spalding, K L

    2010-05-01

    Radiocarbon dating is typically an archaeological tool rather than a forensic one. Recently however, we have shown that the amount of radiocarbon present in tooth enamel, as a result of nuclear bomb testing during the cold war, is a remarkably accurate indicator of when a person is born. Enamel isolated from human teeth is processed to form graphite and carbon-14 ((14)C) levels are measured using accelerator mass spectrometry. Since there is no turnover of enamel after it is formed, (14)C levels in the enamel represent (14)C levels in the atmosphere at the time of its formation. In this paper we describe the strategy used to determine the date of birth of an individual based on radiocarbon levels in tooth enamel, focusing on the methodology of this strategy. Year of birth information can significantly assist police investigators when the identity of a deceased individual is unknown. In such cases police will try to match particulars of the unidentified individual (which is often only gender and/or an estimate of age), with particulars from missing persons lists.

  5. EFFECT OF SURFACE CONDTIONINGON BOND STRENGTH TO ENAMEL AND DENTIN

    Directory of Open Access Journals (Sweden)

    M MOUSAVINASAB

    2002-09-01

    Full Text Available Introduction. Compoglass is a trade mark of dental compomers and because of its partially resinus structure, surface conditioning of dental surfaces is needed for a better bonding process. In this study, the effect of enamel and dentin conditioning procedure on shear bond strength (SBS of compoglass to tooth surfaces was studied. Methods. four groups each one including 11 sound premolars were chosen and their surfaces were prepared as following groups: group1, unconitioned dentin; group 2, dentin conditioning with phosphoric acid 35%; group 3, dentin conditioning with polyacrylic acid 20% group 4, unconditioning enamel; group 5, enamel conditioning with phosphoric acid 35%; and group 6, enamel conditioning with polyacrylic acid 20%. Compoglass was bonded to prepared surfaces and after fixation of the samples in acrylic molds, all samples were tested under shear force of instron testing machine at a rate of 1 mm/min speed. Results. The mean SBS obtained in these 6 groups were 6.207, 8.057, 10.146, 25.939 and 11.827 mpa. the mode of fracture also studied using a streomicroscope. Statistical analysis of the results showed that the maximum SBS obtained in group 5 and the lowest SBS about 6.207 mpa obtained in group 1. Despite increase in SBS group 2 and 3, there was no statistical differncies between group 1, 2 and 3. Discussion. Based on results of this study, conditioning of enamel and dentin surface due to improve SBS is recommeneded.

  6. Enzyme replacement prevents enamel defects in hypophosphatasia mice

    Science.gov (United States)

    Yadav, Manisha C.; de Oliveira, Rodrigo Cardoso; Foster, Brian L.; Fong, Hanson; Cory, Esther; Narisawa, Sonoko; Sah, Robert L.; Somerman, Martha; Whyte, Michael P.; Millán, José Luis

    2012-01-01

    Hypophosphatasia (HPP) is the inborn error of metabolism characterized by deficiency of alkaline phosphatase activity leading to rickets or osteomalacia and to dental defects. HPP occurs from loss-of-function mutations within the gene that encodes the tissue-nonspecific isozyme of alkaline phosphatase (TNAP). TNAP knockout (Alpl−/−, a.k.a. Akp2−/−) mice closely phenocopy infantile HPP, including the rickets, vitamin B6-responsive seizures, improper dentin mineralization, and lack of acellular cementum. Here, we report that lack of TNAP in Alpl−/− mice also causes severe enamel defects, which are preventable by enzyme replacement with mineral-targeted TNAP (ENB-0040). Immunohistochemistry was used to map the spatiotemporal expression of TNAP in the tissues of the developing enamel organ of healthy mouse molars and incisors. We found strong, stage-specific expression of TNAP in ameloblasts. In the Alpl−/− mice, histological, μCT, and scanning electron microscopy analysis showed reduced mineralization and disrupted organization of the rods and inter-rod structures in enamel of both the molars and incisors. All of these abnormalities were prevented in mice receiving from birth daily subcutaneous injections of mineral-targeting, human TNAP (sALP-FcD10, a.k.a. ENB-0040) at 8.2 mg/kg/day for up to 44 days. These data reveal an important role for TNAP in enamel mineralization, and demonstrate the efficacy of mineral-targeted TNAP to prevent enamel defects in HPP. PMID:22461224

  7. Solubility and diffusivity of hydrogen in enameling steel

    Energy Technology Data Exchange (ETDEWEB)

    De Gregorio, P.; Valentini, R.; Solina, A.; Gastaldo, F. (Centro Sviluppo Materiali, Rome (Italy) Pisa Univ. (Italy). Dip. di Ingegneria Chimica, Chimica Industriale e Scienza dei Materiali)

    1991-06-01

    In recent years, continuous casting has almost expelled conventional ingot casting from the steel-making process by its much higher productivity. However, enameling steel sheets doesn't give the steel sufficient resistance to fishscale, as that which is achieved by the inclusions in case of ingot capped steel. Fishscales are caused by hydrogen gas building up pressure at the interface between enamel and steel, resulting in the rupture of enamel. Object of this study, was not only to correlate fishscale susceptibility with metallurgical parameters, but to define the effect of reversible and irreversible traps on hydrogen solubility and diffusivity in enameling steel. Hydrogen permeation was studied, in low carbon enameling steel, with an electrochemical technique developed by Devanathan and co-workers. This method was used to calculate concentrations of irreversibly adsorbed hydrogen and evaluate hydrogen diffusion coefficients. The results on reversible traps correlated with micro-voids formations around the carbide precipitate, while the irreversible traps correlated with inclusions and precipitate content.

  8. Enamel formation and growth in non-mammalian cynodonts

    Science.gov (United States)

    Dirks, Wendy; Martinelli, Agustín G.

    2018-01-01

    The early evolution of mammals is associated with the linked evolutionary origin of diphyodont tooth replacement, rapid juvenile growth and determinate adult growth. However, specific relationships among these characters during non-mammalian cynodont evolution require further exploration. Here, polarized light microscopy revealed incremental lines, resembling daily laminations of extant mammals, in histological sections of enamel in eight non-mammalian cynodont species. In the more basal non-probainognathian group, enamel extends extremely rapidly from cusp to cervix. By contrast, the enamel of mammaliamorphs is gradually accreted, with slow rates of crown extension, more typical of the majority of non-hypsodont crown mammals. These results are consistent with the reduction in dental replacement rate across the non-mammalian cynodont lineage, with greater rates of crown extension required in most non-probainognathians, and slower crown extension rates permitted in mammaliamorphs, which have reduced patterns of dental replacement in comparison with many non-probainognathians. The evolution of mammal-like growth patterns, with faster juvenile growth and more abruptly terminating adult growth, is linked with this reduction in dental replacement rates and may provide an additional explanation for the observed pattern in enamel growth rates. It is possible that the reduction in enamel extension rates in mammaliamorphs reflects an underlying reduction in skeletal growth rates at the time of postcanine formation, due to a more abruptly terminating pattern of adult growth in these more mammal-like, crownward species. PMID:29892415

  9. Amelogenesis Imperfect, Enamel Hypoplasia and Fluorosis Dental - Literature Review

    Directory of Open Access Journals (Sweden)

    Flávia Magnani Bevilacqua

    2015-12-01

    Full Text Available The developmental disorders of enamel are abnormalities of structure which can affect both dentitions. These abnormalities include amelogenesis imperfecta, enamel hypoplasia and dental fluorosis. The amelogenesis imperfecta is a hereditary change and enamel hypoplasia is a quantitative defect of enamel that occurs as a result of systemic problems, local and also inherited factors, or even the combination of them. Dental fluorosis is a hypoplasia caused by the chronic ingestion of fluoride during odontogenesis. All these anomalies have similar clinical characteristics, and it is necessary to be careful in their assessment. It is extremely important to know these abnormalities to establish a differential diagnosis and, consequently, a treatment plan, which can be set for each situation. Therefore, the purpose of this study was to review the literature regarding these three anomalies: amelogenesis imperfecta, enamel hypoplasia and dental fluorosis. It was concluded that to establish the differential diagnosis of these abnormalities as well as a proper treatment plan, it is indispensable the professional knowledge associated with the clinical examination. The examination has to consist of medical history and physical examination, and in some cases, x-ray examination.

  10. Indentation damage and crack repair in human enamel.

    Science.gov (United States)

    Rivera, C; Arola, D; Ossa, A

    2013-05-01

    Tooth enamel is the hardest and most highly mineralized tissue in the human body. While there have been a number of studies aimed at understanding the hardness and crack growth resistance behavior of this tissue, no study has evaluated if cracks in this tissue undergo repair. In this investigation the crack repair characteristics of young human enamel were evaluated as a function of patient gender and as a function of the distance from the Dentin Enamel Junction (DEJ). Cracks were introduced via microindentation along the prism direction and evaluated as a function of time after the indentation. Microscopic observations indicated that the repair of cracks began immediately after crack initiation and reaches saturation after approximately 48 h. During this process he crack length decreased up to 10% of the initial length, and the largest degree of reduction occurred in the deep enamel, nearest the DEJ. In addition, it was found that the degree of repair was significantly greater in the enamel of female patients. Copyright © 2013 Elsevier Ltd. All rights reserved.

  11. Indentation Damage and Crack Repair in Human Enamel*

    Science.gov (United States)

    Rivera, C.; Arola, D.; Ossa, A.

    2013-01-01

    Tooth enamel is the hardest and most highly mineralized tissue in the human body. While there have been a number of studies aimed at understanding the hardness and crack growth resistance behavior of this tissue, no study has evaluated if cracks in this tissue undergo repair. In this investigation the crack repair characteristics of young human enamel were evaluated as a function of patient gender and as a function of the distance from the Dentin Enamel Junction (DEJ). Cracks were introduced via microindentation along the prism direction and evaluated as a function of time after the indentation. Microscopic observations indicated that the repair of cracks began immediately after crack initiation and reaches saturation after approximately 48 hours. During this process he crack length decreased up to 10% of the initial length, and the largest degree of reduction occurred in the deep enamel, nearest the DEJ. In addition, it was found that the degree of repair was significantly greater in the enamel of female patients. PMID:23541701

  12. Year of Birth Determination Using Radiocarbon Dating of Dental Enamel

    Energy Technology Data Exchange (ETDEWEB)

    Buchholz, B A; Spalding, K L

    2009-03-10

    Radiocarbon dating is typically an archaeological tool rather than a forensic one. Recently however, we have shown that the amount of radiocarbon present in tooth enamel, as a result of nuclear bomb testing during the cold war, is a remarkably accurate indicator of when a person is born. Enamel isolated from human teeth is processed to form graphite and carbon-14 ({sup 14}C) levels are measured using accelerator mass spectrometry. Since there is no turnover of enamel after it is formed, {sup 14}C levels in the enamel represent {sup 14}C levels in the atmosphere at the time of its formation. In this paper we describe the strategy used to determine the date of birth of an individual based on radiocarbon levels in tooth enamel, focusing on the methodology of this strategy. Year of birth information can significantly assist police investigators when the identity of a deceased individual is unknown. In such cases police will try to match particulars of the unidentified individual (which is often only gender and/or an estimate of age), with particulars from missing persons lists.

  13. PRIMARY CARIES: AN OVERVIEW

    Directory of Open Access Journals (Sweden)

    Gaurav Solanki

    2012-01-01

    Full Text Available Primary caries is an initial lesions produced by direct extension from an external surface. Dental caries is called as tooth decay or a cavity is a disease in which bacterial processes changes carbohydrate to acid which than dematerializes the hard tooth structure like enamel, dentin and cementum. Streptococcus mutans and Lactobacillus are the bacteria responsible for the dental caries by acid production. This article throws light on the dental caries disease, its sign and symptoms, treatment and prevention of it. A review of some patents on dental caries is also provided that summarizes the recent technical advancements taken place in this area.

  14. The impact of fluoride on ameloblasts and the mechanisms of enamel fluorosis

    NARCIS (Netherlands)

    Bronckers, A.L.J.J.; Lyaruu, D.M.; Denbesten, P.K.

    2009-01-01

    Intake of excess amounts of fluoride during tooth development cause enamel fluorosis, a developmental disturbance that makes enamel more porous. In mild fluorosis, there are white opaque striations across the enamel surface, whereas in more severe cases, the porous regions increase in size, with

  15. Study of the arrangement of crystallites in γ-irradiated human enamel by electron paramagnetic resonance

    International Nuclear Information System (INIS)

    Cevc, P.; Schara, M.; Ravnik, C.; Skaleric, U.

    1976-01-01

    The arrangement of tooth enamel microcrystals has been studied on CO 3 3- bound electrons by paramagnetic resonance. It was found that noncarious human maxillary central incisors have a greater degree of alignment of tooth enamel microcrystals than the carious ones. The outermost surface layer of enamel showed a greater crystallite degree of alignment than other parts

  16. Type VII collagen is enriched in the enamel organic matrix associated with the dentin-enamel junction of mature human teeth.

    Science.gov (United States)

    McGuire, Jacob D; Walker, Mary P; Mousa, Ahmad; Wang, Yong; Gorski, Jeff P

    2014-06-01

    The inner enamel region of erupted teeth is known to exhibit higher fracture toughness and crack growth resistance than bulk phase enamel. However, an explanation for this behavior has been hampered by the lack of compositional information for the residual enamel organic matrix. Since enamel-forming ameloblasts are known to express type VII collagen and type VII collagen null mice display abnormal amelogenesis, the aim of this study was to determine whether type VII collagen is a component of the enamel organic matrix at the dentin-enamel junction (DEJ) of mature human teeth. Immunofluorescent confocal microscopy of demineralized tooth sections localized type VII collagen to the organic matrix surrounding individual enamel rods near the DEJ. Morphologically, immunoreactive type VII collagen helical-bundles resembled the gnarled-pattern of enamel rods detected by Coomassie Blue staining. Western blotting of whole crown or enamel matrix extracts also identified characteristic Mr=280 and 230 kDa type VII dimeric forms, which resolved into 75 and 25 kDa bands upon reduction. As expected, the collagenous domain of type VII collagen was resistant to pepsin digestion, but was susceptible to purified bacterial collagenase. These results demonstrate the inner enamel organic matrix in mature teeth contains macromolecular type VII collagen. Based on its physical association with the DEJ and its well-appreciated capacity to complex with other collagens, we hypothesize that enamel embedded type VII collagen fibrils may contribute not only to the structural resilience of enamel, but may also play a role in bonding enamel to dentin. Copyright © 2014 Elsevier Inc. All rights reserved.

  17. Pb enamel biomarker: Deposition of pre- and postnatal Pb isotope injection in reconstructed time points along rat enamel transect

    International Nuclear Information System (INIS)

    Rinderknecht, A.L.; Kleinman, M.T.; Ericson, J.E.

    2005-01-01

    Exposure to lead (Pb) as well as other heavy metals in the environment is still a matter of public health concern. The development of the enamel biomarker for heavy metal exposure assessment is designed to improve studies of dose-effect relationships to developmental anomalies, particularly embryonic dysfunctions, and to provide a time-specific recount of past exposures. The work presented in this paper demonstrates maternal transfer across the placental barrier of the enriched isotope 206 Pb tracer to the enamel of the rat pup. Likewise, injections of 204 Pb-enriched tracer in the neonate rat resulted in deposition of the tracer in the enamel histology as measured by secondary ion microprobe spectrometry. Through enamel, we were able to observe biological removal and assimilation of prenatal and postnatal tracers, respectively. This research demonstrates that enamel can be used as a biomarker of exposure to Pb and may illustrate the toxicokinetics of incorporating Pb into fetal and neonatal steady-state system processes. The biomarker technique, when completely developed, may be applied to cross-sectional and longitudinal epidemiological research

  18. The Chernobyl accident: EPR dosimetry on dental enamel of children

    International Nuclear Information System (INIS)

    Gualtieri, G.; Colacicchi, S.; Sgattoni, R.; Giannoni, M.

    2001-01-01

    The radiation dose on tooth enamel of children living close to Chernobyl has been evaluated by EPR. The sample preparation was reduced to a minimum of mechanical steps to remove a piece of enamel. A standard X-ray tube at low energy was used for additive irradiation. The filtration effect of facial soft tissue was taken into account. The radiation dose for a group of teeth slightly exceeds the annual dose, whereas for another group the dose very much exceeds the annual dose. Since the higher dose is found in teeth whose enamel have much lower EPR sensitivity to the radiation, it can be suggested that for these teeth the native signal could alter the evaluation of the smaller radiation signal

  19. Evaluation of the bleached human enamel by Scanning Electron Microscopy

    DEFF Research Database (Denmark)

    Miranda, Carolina Baptista; Pagani, Clovis; Benetti, Ana Raquel

    2005-01-01

    Since bleaching has become a popular procedure, the effect of peroxides on dental hard tissues is of great interest in research. Purpose: The aim of this in vitro study was to perform a qualitative analysis of the human enamel after the application of in-office bleaching agents, using Scanning......: 2h); G3- four 2-hour exposures to 35% carbamide peroxide (total exposure: 8h); G4- two applications of 35% hydrogen peroxide, which was light-activated with halogen lamp at 700mW/cm² during 7min and remained in contact with enamel for 20min (total exposure: 40min). All bleaching treatments adopted...... analysis performing gold sputter coating under vacuum and were examined using 15kV at 500x and 2000x magnification. Results: Morphological alterations on the enamel surface were similarly detected after bleaching with either 35% carbamide peroxide or 35% hydrogen peroxide. Surface porosities were...

  20. Evaluation of potential bio-control agents on root-knot nematode ...

    African Journals Online (AJOL)

    Indigenous strains of Trichoderma viride (ITCC No. 6889), Pseudomonas fluorescens (ITCC No. B0034) and Purpureocillium lilacinum (ITCC No.6887) were isolated from undisturbed forest eco-system of Southern India. These three bio-mediators were evaluated for their antagonism towards root knot nematode, ...

  1. A new class of magnetic confinement device in the shape of a knot

    Energy Technology Data Exchange (ETDEWEB)

    Hudson, S. R., E-mail: shudson@pppl.gov; Startsev, E.; Feibush, E. [Princeton Plasma Physics Laboratory, PO Box 451, Princeton, New Jersey 08543 (United States)

    2014-01-15

    We describe a new class of magnetic confinement device, with the magnetic axis in the shape of a knot. We call such devices “knotatrons.” An example is given that has a large volume filled with magnetic surfaces, with significant rotational-transform, and with the magnetic field produced entirely by external circular coils.

  2. The mutual attraction of magnetic knots. [solar hydromagnetic instability in sunspot regions

    Science.gov (United States)

    Parker, E. N.

    1978-01-01

    It is observed that the magnetic knots associated with active regions on the sun have an attraction for each other during the formative period of the active regions, when new magnetic flux is coming to the surface. The attraction disappears when new flux ceases to rise through the surface. Then the magnetic spots and knots tend to come apart, leading to disintegration of the sunspots previously formed. The dissolution of the fields is to be expected, as a consequence of the magnetic repulsion of knots of like polarity and as a consequence of the hydromagnetic exchange instability. The purpose of this paper is to show that the mutual attraction of knots during the formative stages of a sunspot region may be understood as the mutual hydrodynamic attraction of the rising flux tubes. Two rising tubes attract each other, as a consequence of the wake of the leading tube when one is moving behind the other, and as a consequence of the Bernoulli effect when rising side by side.

  3. First report of the root-knot nematode Meloidogyne minor on turfgrass in Belgium

    NARCIS (Netherlands)

    Viaene, N.; Wiseborn, D.B.; Karssen, G.

    2007-01-01

    The root-knot nematode, Meloidogyne minor, was described during 2004 after it was found on potato roots in a field in the Netherlands and in golf courses in England, Wales, and Ireland (2). Since it is associated with yellow patch disease in turf grass and causes deformation of potato tubers (2), it

  4. Modelling phenotypic flexibility : an optimality analysis of gizzard size in Red Knots Calidris canutus

    NARCIS (Netherlands)

    van Gils, Jan A.; Piersma, Theunis; Dekinga, Anne; Battley, Phil F.

    2006-01-01

    Reversible phenotypic changes, such as those observed in nutritional organs of long-distance migrants, increasingly receive the attention of ornithologists. In this paper we review the cost-benefit studies that have been performed on the flexible gizzard of Red Knots Calidris cunutus. By varying the

  5. Modelling phenotypic flexibility: an optimality analysis of gizzard size in Red Knots (Calidris canutus)

    NARCIS (Netherlands)

    Van Gils, J.A.; Piersma, T.; Dekinga, A.; Battley, P.F.

    2006-01-01

    Reversible phenotypic changes, such as those observed in nutritional organs of long-distance migrants, increasingly receive the attention of ornithologists. In this paper we review the cost-benefit studies that have been performed on the flexible gizzard of Red Knots Calidris canutus. By varying the

  6. Quiet eye training improves surgical knot tying more than traditional technical training: a randomized controlled study.

    Science.gov (United States)

    Causer, Joe; Harvey, Adrian; Snelgrove, Ryan; Arsenault, Gina; Vickers, Joan N

    2014-08-01

    We examined the effectiveness of technical training (TT) and quiet eye training (QE) on the performance of one-handed square knot tying in surgical residents. Twenty surgical residents were randomly assigned to the 2 groups and completed pretest, training, retention, and transfer tests. Participants wore a mobile eye tracker that simultaneously recorded their gaze and hand movements. Dependent variables were knot tying performance (%), QE duration (%), number of fixations, total movement time (s), and hand movement phase time (s). The QE training group had significantly higher performance scores, a longer QE duration, fewer fixations, faster total knot tying times, and faster movement phase times compared with the TT group. The QE group maintained performance in the transfer test, whereas the TT group significantly decreased performance from retention to transfer. QE training significantly improved learning, retention, and transfer of surgical knot tying compared with a traditional technical approach. Both performance effectiveness (performance outcome) and movement efficiency (hand movement times) were improved using QE modeling, instruction, and feedback. Copyright © 2014 Elsevier Inc. All rights reserved.

  7. Day and night feeding habitat of Red Knots in Patagonia : Profitability versus safety?

    NARCIS (Netherlands)

    Sitters, HP; Gonzalez, PM; Piersma, T; Baker, AJ; Price, DJ; Sitters, Humphrey P.; González, Patricia M.; Baker, Allan J.; Price, David J.

    2001-01-01

    By radio-tracking and recording the movements of flocks. the distribution of feeding Red Knots (Calidris canutus rufa) was studied day and night at a migration stopover site near San Antonio Oeste, Rio Negro, Argentina in March and April 1998. By day, the birds fed in dense flocks of 500-4000 on an

  8. Azadirachtin powder for control of root-knot nematodes in tomato

    Science.gov (United States)

    USDA ARS Daniel K. Inouye U.S. Pacific Basin Agricultural Research Center, 64 Nowelo St., Hilo, HI 96720. Root-knot nematodes cause root galling and yield reductions in many vegetable crops, including tomato. Three organic treatments to improve root growth and reduce nematode infestation were eval...

  9. Fuzzy knot theory interpretation of Yang-Mills instantons and Witten's 5-Brane model

    International Nuclear Information System (INIS)

    El Naschie, M.S.

    2008-01-01

    A knot theory interpretation of 'tHooft's instanton based on hyperbolic volume, crossing numbers and exceptional Lie symmetry groups is given. Subsequently it is shown that although instantons and particle-like states of Heterotic super strings may appear to be different concepts, on a very deep fuzzy level they are not

  10. Percutaneous untying of a knot in a retained Swan-Ganz catheter

    International Nuclear Information System (INIS)

    Bhatti, Waqar A.; Sinha, Sankar; Rowlands, Peter

    2000-01-01

    A patient was referred to us with a tightly knotted Swan-Ganz catheter. The catheter could not be removed by conventional simple methods. We describe a minimally invasive means of removal of the catheter using an Amplatz gooseneck snare and an angioplasty balloon. This allowed the Catheter to be removed without trauma.

  11. Dissecting host plant manipulation by cyst and root-knot nematodes

    NARCIS (Netherlands)

    Karczmarek, A.

    2006-01-01

    Cyst ( Globodera spp. and Heterodera spp.) and root-knot nematodes ( Meloidogyne spp.), one of the most damaging crop pests, are a perfect example of highly adapted, sophisticated root parasites. These nematodes induces specialized feeding structures (cyst

  12. Effect of soil solarization using plastic mulch in controlling root-knot ...

    African Journals Online (AJOL)

    A field experiment was conducted from February to May, 2004 and 2005 planting seasons at the Vegetable Evaluation and Research Station Farm located at Anse Boileau, Seychelles to evaluate the effect of soil solarization using plastic mulch in controlling root-knot nematode infestation and yield of lettuce.

  13. Basal metabolic rate declines during long-distance migratory flight in great knots

    NARCIS (Netherlands)

    Battley, PF; Dekinga, A; Dietz, MW; Piersma, T; Tang, SX; Hulsman, K; Battley, Phil F.; Tang, Sixian

    2001-01-01

    Great Knots (Calidris tenuirostris) make one of the longest migratory flights in the avian world, flying almost 5500 km from Australia to China during northward migration. We measured basal metabolic rate (BMR) and body composition in birds before and after this flight and found that BMR decreased

  14. Endogenous circannual rhythmicity in body mass, molt, and plumage of Great Knots (Calidris tenuirostris)

    NARCIS (Netherlands)

    Piersma, Theunis; Brugge, Maarten; Spaans, Bernard; Battley, Phil F.; Handel, C.M.

    Four Great Knots (Calidris tenuirostris) were kept for six years in a constant-temperature indoor aviary. For two of those six years, they were kept under photoperiodic conditions that mimicked natural changes in daylength for wild birds, followed by four years under a constant photoperiod

  15. Hanseniaspora nodinigri, a new yeast species found in black knots (Dibotryon morbosum) of Prunus virginiana.

    Science.gov (United States)

    Lachance, M A

    1981-07-01

    The new yeast species Hanseniaspora nodinigri is described to accommodate members of the genus Hanseniaspora that are unable to assimilate glucono-sigma-lactone and isolated from stromatal tissue of black knots (Dobotryon morbosum) of chokecherry, Prunus virginiana. The newly described taxon shows much resemblance, by other criteria, to H. vineae van der Walt et Tscheuschner and H. osmophila (Niehaus) Phaff, Miller et Shifrine.

  16. Interference from adults forces young red knots to forage for longer and in dangerous places

    NARCIS (Netherlands)

    van den Hout, P.J.; van Gils, J.A.; Robin, F.; van der Geest, M.; Dekinga, A.; Piersma, T.

    2014-01-01

    In birds and mammals, juvenile and adult foragers are often found apart from each other. In this study, we found this is also true for red knots, Calidris canutus canutus, wintering on the intertidal flats of Banc d'Arguin, Mauritania. Not only did juveniles feed separately from adults, they also

  17. Evaluation of edible ginger and turmeric cultivars for root-knot nematode resistance

    Science.gov (United States)

    Edible ginger and turmeric roots are important agricultural commodities for the State of Hawaii. Bacterial wilt, Ralstonia solanacearum, and root-knot nematodes, Meloidogyne spp. are major factors hindering optimum production. An evaluation of tolerance and resistance to M. incognita was undertake...

  18. Tolerance of a knotted near infrared fluorescent protein to random circular permutation

    Science.gov (United States)

    Pandey, Naresh; Kuypers, Brianna E.; Nassif, Barbara; Thomas, Emily E.; Alnahhas, Razan N.; Segatori, Laura; Silberg, Jonathan J.

    2016-01-01

    Bacteriophytochrome photoreceptors (BphP) are knotted proteins that have been developed as near-infrared fluorescent protein (iRFP) reporters of gene expression. To explore how rearrangements in the peptides that interlace into the knot within the BphP photosensory core affect folding, we subjected iRFP to random circular permutation using an improved transposase mutagenesis strategy and screened for variants that fluoresce. We identified twenty seven circularly permuted iRFP that display biliverdin-dependent fluorescence in Escherichia coli. The variants with the brightest whole cell fluorescence initiated translation at residues near the domain linker and knot tails, although fluorescent variants were discovered that initiated translation within the PAS and GAF domains. Circularly permuted iRFP retained sufficient cofactor affinity to fluoresce in tissue culture without the addition of biliverdin, and one variant displayed enhanced fluorescence when expressed in bacteria and tissue culture. This variant displayed a similar quantum yield as iRFP, but exhibited increased resistance to chemical denaturation, suggesting that the observed signal increase arose from more efficient protein maturation. These results show how the contact order of a knotted BphP can be altered without disrupting chromophore binding and fluorescence, an important step towards the creation of near-infrared biosensors with expanded chemical-sensing functions for in vivo imaging. PMID:27304983

  19. Tolerance of a Knotted Near-Infrared Fluorescent Protein to Random Circular Permutation.

    Science.gov (United States)

    Pandey, Naresh; Kuypers, Brianna E; Nassif, Barbara; Thomas, Emily E; Alnahhas, Razan N; Segatori, Laura; Silberg, Jonathan J

    2016-07-12

    Bacteriophytochrome photoreceptors (BphP) are knotted proteins that have been developed as near-infrared fluorescent protein (iRFP) reporters of gene expression. To explore how rearrangements in the peptides that interlace into the knot within the BphP photosensory core affect folding, we subjected iRFPs to random circular permutation using an improved transposase mutagenesis strategy and screened for variants that fluoresce. We identified 27 circularly permuted iRFPs that display biliverdin-dependent fluorescence in Escherichia coli. The variants with the brightest whole cell fluorescence initiated translation at residues near the domain linker and knot tails, although fluorescent variants that initiated translation within the PAS and GAF domains were discovered. Circularly permuted iRFPs retained sufficient cofactor affinity to fluoresce in tissue culture without the addition of biliverdin, and one variant displayed enhanced fluorescence when expressed in bacteria and tissue culture. This variant displayed a quantum yield similar to that of iRFPs but exhibited increased resistance to chemical denaturation, suggesting that the observed increase in the magnitude of the signal arose from more efficient protein maturation. These results show how the contact order of a knotted BphP can be altered without disrupting chromophore binding and fluorescence, an important step toward the creation of near-infrared biosensors with expanded chemical sensing functions for in vivo imaging.

  20. First report of the root-knot nematode Meloidogyne marylandi on Turfgrasses in Israel

    NARCIS (Netherlands)

    Oka, Y.; Karssen, G.; Mor, M.

    2004-01-01

    In a turfgrass nursery in Arava, Israel, a population of root-knot nematodes was isolated from poorly growing Zoysiagrass (Zoysia japonica Steud.) with symptoms of foliar chlorosis and roots with very small, smooth galls and protruding egg masses. The isolated population (genus Meloidogyne) included

  1. Evaluation of tomato genotypes for resistance to root-knot nematodes

    African Journals Online (AJOL)

    Tomato (Solanum lycopersicum) is one of the most popular vegetable crops worldwide, owing to its high nutritive value and diversified use. Tomato production in Ghana is threatened by plant parasitic nematodes, especially the root knot nematodes (Meloidogyne spp.), which are responsible for huge economic yield losses.

  2. Intravesical knotting of feeding tube used as urinary catheter in an infant

    Directory of Open Access Journals (Sweden)

    Mamatha Basavaraju

    2016-09-01

    Full Text Available Infant feeding tube is commonly used to temporarily drain the bladder in pediatric population. A case is described where the tube got knotted inside the bladder probably due to over insertion or bladder spasm caused by irritation of catheter.

  3. Hydrodynamic characteristics of knotted and knotless purse seine netting panels as determined in a flume tank.

    Science.gov (United States)

    Tang, Hao; Xu, Liuxiong; Hu, Fuxiang

    2018-01-01

    Nylon (PA) netting is widely used in purse seines and other fishing gears due to its high strength and good sinking performance. However, hydrodynamic properties of nylon netting of different characteristics are poorly understood. This study investigated hydrodynamic characteristics of nylon netting of different knot types and solidity ratios under different attack angles and flow velocities. It was found that the hydrodynamic coefficient of netting panels was related to Reynolds number, solidity ratio, attack angle, knot type and twine construction. The solidity ratio was found to positively correlate with drag coefficient when the netting was normal to the flow (CD90), but not the case when the netting was parallel to the flow (CD0). For netting panels inclined to the flow, the inclined drag coefficient had a negative relationship with the solidity ratio for attack angles between 0° and 50°, but a positive relationship for attack angles between 50° and 90°. The lift coefficient increased with the attack angle, reaching the culminating point at an attack angle of 50°, before subsequent decline. We found that the drag generated by knot accounted for 15-25% of total drag, and the knotted netting with higher solidity ratio exhibited a greater CD0, but it was not the case for the knotless netting. Compared to knotless polyethylene (PE) netting, the drag coefficients of knotless PA netting were dominant at higher Reynolds number (Re>2200).

  4. Hydrodynamic characteristics of knotted and knotless purse seine netting panels as determined in a flume tank.

    Directory of Open Access Journals (Sweden)

    Hao Tang

    Full Text Available Nylon (PA netting is widely used in purse seines and other fishing gears due to its high strength and good sinking performance. However, hydrodynamic properties of nylon netting of different characteristics are poorly understood. This study investigated hydrodynamic characteristics of nylon netting of different knot types and solidity ratios under different attack angles and flow velocities. It was found that the hydrodynamic coefficient of netting panels was related to Reynolds number, solidity ratio, attack angle, knot type and twine construction. The solidity ratio was found to positively correlate with drag coefficient when the netting was normal to the flow (CD90, but not the case when the netting was parallel to the flow (CD0. For netting panels inclined to the flow, the inclined drag coefficient had a negative relationship with the solidity ratio for attack angles between 0° and 50°, but a positive relationship for attack angles between 50° and 90°. The lift coefficient increased with the attack angle, reaching the culminating point at an attack angle of 50°, before subsequent decline. We found that the drag generated by knot accounted for 15-25% of total drag, and the knotted netting with higher solidity ratio exhibited a greater CD0, but it was not the case for the knotless netting. Compared to knotless polyethylene (PE netting, the drag coefficients of knotless PA netting were dominant at higher Reynolds number (Re>2200.

  5. Enamel thickness after preparation of tooth for porcelain laminate.

    Science.gov (United States)

    Pahlevan, Ayoub; Mirzaee, Mansoreh; Yassine, Esmaeil; Ranjbar Omrany, Ladan; Hasani Tabatabaee, Masumeh; Kermanshah, Hamid; Arami, Sakineh; Abbasi, Mehdy

    2014-07-01

    In this investigation the thickness of enamel in the gingival, middle, and incisal thirds of the labial surface of the anterior teeth were measured regarding preparation of the teeth for porcelain laminate veneers. Part one, 20 extracted intact human maxillary central and lateral incisors ten of each were selected. The teeth were imbedded in autopolimerize acrylic resin. Cross section was preformed through the midline of the incisal, middle and cervical one-third of the labial surface of the teeth. The samples were observed under reflected stereomicroscope and the thickness of enamel was recorded. Part II, the effect of different types of preparation on dentin exposure was evaluated. Thirty maxillary central incisor teeth were randomly divided into two groups: A: Knife-edge preparation. B: Chamfer preparation. All samples were embedded in autopolimerize acrylic resin using a silicon mold. The samples were cut through the midline of the teeth. The surface of the samples were polished and enamel and dentin were observed under the stereomicroscope. Data were analyzed by ANOVA-one way test. The results of this study showed that the least enamel thickness in the central incisor was 345 and in lateral incisor is 235 μ this thickness is related to the one-third labial cervical area. Maximum thickness in maxillary central and lateral incisors in the one-third labial incisal surface was 1260 μ and 1220μ, respectively. In the second part of the study, the tendency of dentinal exposure was shown with the chamfer preparation, but no dentinal exposure was found in the knife-edge preparation. The differences between groups were significant (p<0.05). The knowledge of enamel thickness in different part of labial surface is very important. The thickness of enamel in the gingival area does not permit a chamfer preparation. The knife edge preparation is preferable in gingival area.

  6. Enamel thickness after preparation of tooth for porcelain laminate.

    Directory of Open Access Journals (Sweden)

    Ayoub Pahlevan

    2014-08-01

    Full Text Available In this investigation the thickness of enamel in the gingival, middle, and incisal thirds of the labial surface of the anterior teeth were measured regarding preparation of the teeth for porcelain laminate veneers.Part one, 20 extracted intact human maxillary central and lateral incisors ten of each were selected. The teeth were imbedded in autopolimerize acrylic resin. Cross section was preformed through the midline of the incisal, middle and cervical one-third of the labial surface of the teeth. The samples were observed under reflected stereomicroscope and the thickness of enamel was recorded. Part II, the effect of different types of preparation on dentin exposure was evaluated. Thirty maxillary central incisor teeth were randomly divided into two groups: A: Knife-edge preparation. B: Chamfer preparation. All samples were embedded in autopolimerize acrylic resin using a silicon mold. The samples were cut through the midline of the teeth. The surface of the samples were polished and enamel and dentin were observed under the stereomicroscope.Data were analyzed by ANOVA-one way test. The results of this study showed that the least enamel thickness in the central incisor was 345 and in lateral incisor is 235 μ this thickness is related to the one-third labial cervical area. Maximum thickness in maxillary central and lateral incisors in the one-third labial incisal surface was 1260 μ and 1220μ, respectively. In the second part of the study, the tendency of dentinal exposure was shown with the chamfer preparation, but no dentinal exposure was found in the knife-edge preparation. The differences between groups were significant (p<0.05.The knowledge of enamel thickness in different part of labial surface is very important. The thickness of enamel in the gingival area does not permit a chamfer preparation. The knife edge preparation is preferable in gingival area.

  7. Quantitative analysis of enamel on debonded orthodontic brackets.

    Science.gov (United States)

    Cochrane, Nathan J; Lo, Thomas W G; Adams, Geoffrey G; Schneider, Paul M

    2017-09-01

    Iatrogenic damage to the tooth surface in the form of enamel tearouts can occur during removal of fixed orthodontic appliances. The aim of this study was to assess debonded metal and ceramic brackets attached with a variety of bonding materials to determine how frequently this type of damage occurs. Eighty-one patients close to finishing fixed orthodontic treatment were recruited. They had metal brackets bonded with composite resin and a 2-step etch-and-bond technique or ceramic brackets bonded with composite resin and a 2-step etch-and- bond technique, and composite resin with a self-etching primer or resin-modified glass ionomer cement. Debonded brackets were examined by backscattered scanning electron microscopy with energy dispersive x-ray spectroscopy to determine the presence and area of enamel on the base pad. Of the 486 brackets collected, 26.1% exhibited enamel on the bonding material on the bracket base pad. The incidences of enamel tearouts for each group were metal brackets, 13.3%; ceramic brackets, 30.2%; composite resin with self-etching primer, 38.2%; and resin-modified glass ionomer cement, 21.2%. The percentage of the bracket base pad covered in enamel was highly variable, ranging from 0% to 46.1%. Enamel damage regularly occurred during the debonding process with the degree of damage being highly variable. Damage occurred more frequently when ceramic brackets were used (31.9%) compared with metal brackets (13.3%). Removal of ceramic brackets bonded with resin-modified glass ionomer cement resulted in less damage compared with the resin bonding systems. Copyright © 2017 American Association of Orthodontists. Published by Elsevier Inc. All rights reserved.

  8. Recovery of crystallographic texture in remineralized dental enamel.

    Science.gov (United States)

    Siddiqui, Samera; Anderson, Paul; Al-Jawad, Maisoon

    2014-01-01

    Dental caries is the most prevalent disease encountered by people of all ages around the world. Chemical changes occurring in the oral environment during the caries process alter the crystallography and microstructure of dental enamel resulting in loss of mechanical function. Little is known about the crystallographic effects of demineralization and remineralization. The motivation for this study was to develop understanding of the caries process at the crystallographic level in order to contribute towards a long term solution. In this study synchrotron X-ray diffraction combined with scanning electron microscopy and scanning microradiography have been used to correlate enamel crystallography, microstructure and mineral concentration respectively in enamel affected by natural caries and following artificial demineralization and remineralization regimes. In particular, the extent of destruction and re-formation of this complex structure has been measured. 2D diffraction patterns collected at the European Synchrotron Radiation Facility were used to quantify changes in the preferred orientation (crystallographic texture) and position of the (002) Bragg reflection within selected regions of interest in each tooth slice, and then correlated with the microstructure and local mineral mass. The results revealed that caries and artificial demineralization cause a large reduction in crystallographic texture which is coupled with the loss of mineral mass. Remineralization restores the texture to the original level seen in healthy enamel and restores mineral density. The results also showed that remineralization promotes ordered formation of new crystallites and growth of pre-existing crystallites which match the preferred orientation of healthy enamel. Combining microstructural and crystallographic characterization aids the understanding of caries and erosion processes and assists in the progress towards developing therapeutic treatments to allow affected enamel to regain

  9. Electron paramagnetic resonance biophysical radiation dosimetry with tooth enamel

    International Nuclear Information System (INIS)

    Khan, Rao F.H.

    2003-01-01

    This thesis deals with the advancements made in the field of Electron Paramagnetic Resonance (EPR) for biophysical dosimetry with tooth enamel for accident, emergency, and retrospective radiation dose reconstruction. A methodology has been developed to measure retrospective radiation exposures in human tooth enamel. This entails novel sample preparation procedures with minimum mechanical treatment to reduce the preparation induced uncertainties, establish optimum measurement conditions inside the EPR cavity, post-process the measured spectrum with functional simulation of dosimetric and other interfering signals, and reconstruct dose. By using this technique, retrospective gamma exposures as low as 80±30 mGy have been successfully deciphered. The notion of dose modifier was introduced in EPR biodosimetry for low dose measurements. It has been demonstrated that by using the modified zero added dose (MZAD) technique for low radiation exposures, doses in 100 mGy ranges can be easily reconstructed in teeth that were previously thought useless for EPR dosimetry. Also, the use of a dose modifier makes robust dose reconstruction possible for higher radiation exposures. The EPR dosimetry technique was also developed for tooth samples extracted from rodents, which represent small tooth sizing. EPR doses in the molars, extracted from the mice irradiated with whole body exposures, were reassessed and shown to be correct within the experimental uncertainty. The sensitivity of human tooth enamel for neutron irradiation, obtained from the 3 MV McMaster K.N. Van de Graaff accelerator, was also studied. For the first time this work has shown that the neutron sensitivity of the tooth enamel is approximately 1/10th of the equivalent gamma sensitivity. Parametric studies for neutron dose rate and neutron energy within the available range of the accelerator, showed no impact on the sensitivity of the tooth enamel. Therefore, tooth enamel can be used as a dosimeter for both neutrons

  10. Enamel ultrastructure in fossil cetaceans (Cetacea: Archaeoceti and Odontoceti.

    Directory of Open Access Journals (Sweden)

    Carolina Loch

    Full Text Available The transition from terrestrial ancestry to a fully pelagic life profoundly altered the body systems of cetaceans, with extreme morphological changes in the skull and feeding apparatus. The Oligocene Epoch was a crucial time in the evolution of cetaceans when the ancestors of modern whales and dolphins (Neoceti underwent major diversification, but details of dental structure and evolution are poorly known for the archaeocete-neocete transition. We report the morphology of teeth and ultrastructure of enamel in archaeocetes, and fossil platanistoids and delphinoids, ranging from late Oligocene (Waitaki Valley, New Zealand to Pliocene (Caldera, Chile. Teeth were embedded in epoxy resin, sectioned in cross and longitudinal planes, polished, etched, and coated with gold palladium for scanning electron microscopy (SEM observation. SEM images showed that in archaeocetes, squalodontids and Prosqualodon (taxa with heterodont and nonpolydont/limited polydont teeth, the inner enamel was organized in Hunter-Schreger bands (HSB with an outer layer of radial enamel. This is a common pattern in most large-bodied mammals and it is regarded as a biomechanical adaptation related to food processing and crack resistance. Fossil Otekaikea sp. and delphinoids, which were polydont and homodont, showed a simpler structure, with inner radial and outer prismless enamel. Radial enamel is regarded as more wear-resistant and has been retained in several mammalian taxa in which opposing tooth surfaces slide over each other. These observations suggest that the transition from a heterodont and nonpolydont/limited polydont dentition in archaeocetes and early odontocetes, to homodont and polydont teeth in crownward odontocetes, was also linked to a marked simplification in the enamel Schmelzmuster. These patterns probably reflect functional shifts in food processing from shear-and-mastication in archaeocetes and early odontocetes, to pierce-and-grasp occlusion in crownward

  11. Enamel ultrastructure in fossil cetaceans (Cetacea: Archaeoceti and Odontoceti).

    Science.gov (United States)

    Loch, Carolina; Kieser, Jules A; Fordyce, R Ewan

    2015-01-01

    The transition from terrestrial ancestry to a fully pelagic life profoundly altered the body systems of cetaceans, with extreme morphological changes in the skull and feeding apparatus. The Oligocene Epoch was a crucial time in the evolution of cetaceans when the ancestors of modern whales and dolphins (Neoceti) underwent major diversification, but details of dental structure and evolution are poorly known for the archaeocete-neocete transition. We report the morphology of teeth and ultrastructure of enamel in archaeocetes, and fossil platanistoids and delphinoids, ranging from late Oligocene (Waitaki Valley, New Zealand) to Pliocene (Caldera, Chile). Teeth were embedded in epoxy resin, sectioned in cross and longitudinal planes, polished, etched, and coated with gold palladium for scanning electron microscopy (SEM) observation. SEM images showed that in archaeocetes, squalodontids and Prosqualodon (taxa with heterodont and nonpolydont/limited polydont teeth), the inner enamel was organized in Hunter-Schreger bands (HSB) with an outer layer of radial enamel. This is a common pattern in most large-bodied mammals and it is regarded as a biomechanical adaptation related to food processing and crack resistance. Fossil Otekaikea sp. and delphinoids, which were polydont and homodont, showed a simpler structure, with inner radial and outer prismless enamel. Radial enamel is regarded as more wear-resistant and has been retained in several mammalian taxa in which opposing tooth surfaces slide over each other. These observations suggest that the transition from a heterodont and nonpolydont/limited polydont dentition in archaeocetes and early odontocetes, to homodont and polydont teeth in crownward odontocetes, was also linked to a marked simplification in the enamel Schmelzmuster. These patterns probably reflect functional shifts in food processing from shear-and-mastication in archaeocetes and early odontocetes, to pierce-and-grasp occlusion in crownward odontocetes, with

  12. A model for predicting wear rates in tooth enamel.

    Science.gov (United States)

    Borrero-Lopez, Oscar; Pajares, Antonia; Constantino, Paul J; Lawn, Brian R

    2014-09-01

    It is hypothesized that wear of enamel is sensitive to the presence of sharp particulates in oral fluids and masticated foods. To this end, a generic model for predicting wear rates in brittle materials is developed, with specific application to tooth enamel. Wear is assumed to result from an accumulation of elastic-plastic micro-asperity events. Integration over all such events leads to a wear rate relation analogous to Archard׳s law, but with allowance for variation in asperity angle and compliance. The coefficient K in this relation quantifies the wear severity, with an arbitrary distinction between 'mild' wear (low K) and 'severe' wear (high K). Data from the literature and in-house wear-test experiments on enamel specimens in lubricant media (water, oil) with and without sharp third-body particulates (silica, diamond) are used to validate the model. Measured wear rates can vary over several orders of magnitude, depending on contact asperity conditions, accounting for the occurrence of severe enamel removal in some human patients (bruxing). Expressions for the depth removal rate and number of cycles to wear down occlusal enamel in the low-crowned tooth forms of some mammals are derived, with tooth size and enamel thickness as key variables. The role of 'hard' versus 'soft' food diets in determining evolutionary paths in different hominin species is briefly considered. A feature of the model is that it does not require recourse to specific material removal mechanisms, although processes involving microplastic extrusion and microcrack coalescence are indicated. Published by Elsevier Ltd.

  13. Recovery of crystallographic texture in remineralized dental enamel.

    Directory of Open Access Journals (Sweden)

    Samera Siddiqui

    Full Text Available Dental caries is the most prevalent disease encountered by people of all ages around the world. Chemical changes occurring in the oral environment during the caries process alter the crystallography and microstructure of dental enamel resulting in loss of mechanical function. Little is known about the crystallographic effects of demineralization and remineralization. The motivation for this study was to develop understanding of the caries process at the crystallographic level in order to contribute towards a long term solution. In this study synchrotron X-ray diffraction combined with scanning electron microscopy and scanning microradiography have been used to correlate enamel crystallography, microstructure and mineral concentration respectively in enamel affected by natural caries and following artificial demineralization and remineralization regimes. In particular, the extent of destruction and re-formation of this complex structure has been measured. 2D diffraction patterns collected at the European Synchrotron Radiation Facility were used to quantify changes in the preferred orientation (crystallographic texture and position of the (002 Bragg reflection within selected regions of interest in each tooth slice, and then correlated with the microstructure and local mineral mass. The results revealed that caries and artificial demineralization cause a large reduction in crystallographic texture which is coupled with the loss of mineral mass. Remineralization restores the texture to the original level seen in healthy enamel and restores mineral density. The results also showed that remineralization promotes ordered formation of new crystallites and growth of pre-existing crystallites which match the preferred orientation of healthy enamel. Combining microstructural and crystallographic characterization aids the understanding of caries and erosion processes and assists in the progress towards developing therapeutic treatments to allow affected

  14. Effects of etching time on enamel bond strengths.

    Science.gov (United States)

    Triolo, P T; Swift, E J; Mudgil, A; Levine, A

    1993-12-01

    This study evaluated the effects of etching time on bond strengths of composite to enamel. Proximal surfaces of extracted molars were etched with either a conventional etchant (35% phosphoric acid) or one of two dentin/enamel conditioners, 10% maleic acid (Scotchbond Multi-Purpose Etchant), or a solution of oxalic acid, aluminum nitrate, and glycine (Gluma 1 & 2 Conditioner). Each agent was applied for 15, 30, or 60 seconds. Specimens etched with 35% phosphoric acid had the highest mean bond strengths at each etching time. At the manufacturer's recommended application times, the other two agents gave significantly lower shear bond strengths than phosphoric acid.

  15. Inter-proximal enamel reduction in contemporary orthodontics.

    Science.gov (United States)

    Pindoria, J; Fleming, P S; Sharma, P K

    2016-12-16

    Inter-proximal enamel reduction has gained increasing prominence in recent years being advocated to provide space for orthodontic alignment, to refine contact points and to potentially improve long-term stability. An array of techniques and products are available ranging from hand-held abrasive strips to handpiece mounted burs and discs. The indications for inter-proximal enamel reduction and the importance of formal space analysis, together with the various techniques and armamentarium which may be used to perform it safely in both the labial and buccal segments are outlined.

  16. Mammalian enamel maturation: Crystallographic changes prior to tooth eruption

    Czech Academy of Sciences Publication Activity Database

    Kallistová, Anna; Horáček, I.; Šlouf, Miroslav; Skála, Roman; Fridrichová, Michaela

    2017-01-01

    Roč. 12, č. 2 (2017), č. článku e0171424. E-ISSN 1932-6203 R&D Projects: GA MŠk(CZ) LO1507 Institutional support: RVO:67985831 ; RVO:61389013 Keywords : resolution electron-microscopy * atomic-force microscopy * dental enamel * vertebrate dentition * rat enamel * protein * evolution * crystals * shape * ameloblastin Subject RIV: EH - Ecology, Behaviour; CD - Macromolecular Chemistry (UMCH-V) OBOR OECD: Other biological topics; Polymer science (UMCH-V) Impact factor: 2.806, year: 2016

  17. Surface changes of enamel after brushing with charcoal toothpaste

    Science.gov (United States)

    Pertiwi, U. I.; Eriwati, Y. K.; Irawan, B.

    2017-08-01

    The aim of this study was to determine the surface roughness changes of tooth enamel after brushing with charcoal toothpaste. Thirty specimens were brushed using distilled water (the first group), Strong® Formula toothpaste (the second group), and Charcoal® Formula toothpaste for four minutes and 40 seconds (equivalent to one month) and for 14 minutes (equivalent to three months) using a soft fleece toothbrush with a mass of 150 gr. The roughness was measured using a surface roughness tester, and the results were tested with repeated ANOVA test and one-way ANOVA. The value of the surface roughness of tooth enamel was significantly different (penamel.

  18. Non-specific esterases in partly mineralized bovine enamel

    DEFF Research Database (Denmark)

    Moe, D; Kirkeby, S

    1990-01-01

    Activity for non-specific esterase was demonstrated in the matrix of developing bovine enamel with alpha-naphthyl acetate and 5-bromoindoxyl acetate as the esterase substrates. By use of high-performance liquid chromatography gel filtration, ion-exchange chromatography, and electrophoresis three...... esterases were shown to be present in the enamel matrix. The enzymes showed highest activity at pH 6.5-7.5. In sections a strong reaction was observed in the secretory ameloblasts. The esterases may be proteolytic enzymes that participate in the degradation of the matrix proteins....

  19. Effect of Various Finishing Procedures on the Reflectivity (Shine) of Tooth Enamel - An In-vitro Study.

    Science.gov (United States)

    Patil, Harshal Ashok; Chitko, Shrikant Shrinivas; Kerudi, Veerendra Virupaxappa; Maheshwari, Amit Ratanlal; Patil, Neeraj Suresh; Tekale, Pawankumar Dnyandeo; Gore, Ketan Ashorao; Zope, Amit Ashok

    2016-08-01

    Reflectivity of an object is a good parameter for surface finish. As the patient evaluates finishing as a function of gloss/reflectivity/shine an attempt is made here to evaluate changes in surface finish with custom made reflectometer. The aim of the present study was to study the effect of various procedures during orthodontic treatment on the shine of enamel, using a custom made reflectometer. Sixty one extracted premolars were collected and each tooth was mounted on acrylic block. Reflectivity of the teeth was measured as compared to standard before any procedure. One tooth was kept as standard throughout the study. Sixty teeth were acid etched. Reflectivity was measured on custom made reflectometer and readings recorded. Same procedure was repeated after debonding. Then 60 samples were divided into three groups: Group 1 - Tungsten Carbide, Group 2 - Astropol, Group 3- Sof-Lex disc depending upon the finishing method after debonding and reflectivity was measured. The mean percentage of reflectivity after acid etching was 31.4%, debonding 45.5%, Tungsten carbide bur finishing (Group 1) was 58.3%, Astropol (Group 2) 72.8%, and Sof-Lex disc (Group 3) 84.4% as that to the standard. There was statistically very highly significant (p Group 2> Group 1. The primary goal was to restore the enamel to its original state after orthodontic treatment. The methods tested in this study could not restore the original enamel reflectivity.

  20. Pierced Lasso Bundles are a new class of knot-like motifs.

    Directory of Open Access Journals (Sweden)

    Ellinor Haglund

    2014-06-01

    Full Text Available A four-helix bundle is a well-characterized motif often used as a target for designed pharmaceutical therapeutics and nutritional supplements. Recently, we discovered a new structural complexity within this motif created by a disulphide bridge in the long-chain helical bundle cytokine leptin. When oxidized, leptin contains a disulphide bridge creating a covalent-loop through which part of the polypeptide chain is threaded (as seen in knotted proteins. We explored whether other proteins contain a similar intriguing knot-like structure as in leptin and discovered 11 structurally homologous proteins in the PDB. We call this new helical family class the Pierced Lasso Bundle (PLB and the knot-like threaded structural motif a Pierced Lasso (PL. In the current study, we use structure-based simulation to investigate the threading/folding mechanisms for all the PLBs along with three unthreaded homologs as the covalent loop (or lasso in leptin is important in folding dynamics and activity. We find that the presence of a small covalent loop leads to a mechanism where structural elements slipknot to thread through the covalent loop. Larger loops use a piercing mechanism where the free terminal plugs through the covalent loop. Remarkably, the position of the loop as well as its size influences the native state dynamics, which can impact receptor binding and biological activity. This previously unrecognized complexity of knot-like proteins within the helical bundle family comprises a completely new class within the knot family, and the hidden complexity we unraveled in the PLBs is expected to be found in other protein structures outside the four-helix bundles. The insights gained here provide critical new elements for future investigation of this emerging class of proteins, where function and the energetic landscape can be controlled by hidden topology, and should be take into account in ab initio predictions of newly identified protein targets.

  1. Management of Root Knot Nematode on Tomato through Grafting Root Stock of Solanum sisymbriifolium

    Directory of Open Access Journals (Sweden)

    Suraj Baidya

    2017-05-01

    Full Text Available The root-knot nematodes (Meloidogyne spp are difficult to manage once established in the field because of their wide host range, and soil-borne nature. Thus, the aim of the present study was to examine the use of resistant root stock of wild brinjal (Solanum sisymbriifolium to reduce the loss caused by the nematodes on tomato. For the management of root-knot nematodes, grafted plant with resistant root stock of the wild brinjal was tested under farmers’ field conditions at Hemza of Kaski district. Grafted and non-grafted plants were produced in root-knot nematode-free soil. Around three week-old grafted and non-grafted tomato plants were transplanted in four different plastic tunnels where root-knot nematodes had been reported previously. The plants were planted in diagonal position to each other as a pair plot in 80 × 60 cm2 spacing in an average of 20 × 7 m2 plastic tunnels. Galling Index (GI was recorded three times in five randomly selected plants in each plot at 60 days intervals. The first observation was recorded two months after transplanting. Total fruit yield was recorded from same plants. In the grafted plants, the root system was totally free from gall whereas in an average of 7.5 GI in 0-10 scale was recorded in the non-grafted plants. Fruits were harvested from time to time and cumulated after final harvest to calculate the total fruit yield. It was estimated that on an average tomato fruit yield was significantly (P>0.05 increased by 37 percent in the grafted plants compared with the non-grafted plants. Grafting technology could be used effectively for cultivation of commonly grown varieties, which are susceptible to root-knot nematodes in disease prone areas. This can be used as an alternative technology for reducing the use of hazardous pesticides for enhancing commercial organic tomato production.

  2. Effect of ethanol-wet-bonding technique on resin–enamel bonds

    Directory of Open Access Journals (Sweden)

    Muhammet Kerim Ayar

    2014-03-01

    Conclusion: The ethanol-wet-bonding technique may increase the bond strength of commercial adhesives to enamel. The chemical composition of the adhesives can affect the bond strength of adhesives when bonding to acid-etched enamel, using the ethanol-wet-bonding technique. Some adhesive systems used in the present study may simultaneously be applied to enamel and dentin using ethanol-wet-bonding. Furthermore, deploying ethanol-wet-bonding for the tested commercial adhesives to enamel can increase the adhesion abilities of these adhesives to enamel.

  3. Thermal Transformations of Iron Cations in the System Metal-Vitreous Enamel Coat. Moessbauer Spectroscopic Study

    International Nuclear Information System (INIS)

    Barcova, K.; Mashlan, M.; Zboril, R.; Hrabovska, K.

    2005-01-01

    Vitreous enameling on steel is carried out to provide a protective layer against chemical corrosion from the surrounding environment. The glass bonds with the steel to form a composite material. The Moessbauer spectroscopy was firstly applied to study the vitreous enameling in which the complex of processes, as diffusion of species, adhesion between the glass and the steel, galvanic reactions, plays an important role. The Moessbauer spectroscopy provides unique information about the Fe-phase structure of the vitreous enamel layer and that of the steel-enamel interface. Diffusion of iron from steel surface towards enamel layer and formation of a new Fe2+ phase was proved

  4. An in vitro study of dental enamel wear by restorative materials using radiometric method

    International Nuclear Information System (INIS)

    Adachi, Lena Katekawa

    2000-01-01

    There is an increasing demand and interest to study the dental materials wear as well as about the abrasion effect on antagonistic teeth. Due to the fact that the existent restorative materials have no specifications about their abrasiveness, it is necessary the establishment of degrees of comparison among them to support clinical application. In this work, the radiometric method was applied to study the enamel wear caused by another enamel and by restorative materials (Ceramco II, Noritake and Finesse porcelains, Artglass and Targis). The dental enamel made radioactive by irradiation at the IEA-R1m nuclear research reactor under a thermal neutron flux was submitted to wear in a machine which allows sliding motion of an antagonistic surface in contact with this radioactive enamel. The enamel wear was evaluated by measuring beta activity of 32 P transferred to water from this irradiated tooth. Results obtained indicated that dental porcelains cause pronounced enamel wear when compared with that provoked by another enamel or by resin materials. Resin materials caused less enamel wear than another enamel. Vickers microhardness data obtained for antagonistic materials showed a correlation with the wear caused to the enamel. This study allowed to conclude that the radiometric method proposed can be used satisfactorily in the evaluation of enamel wear by restorative materials. This method presents advantages due to quick responses and ease of analyses There is (author)

  5. On the critical parameters that regulate the deformation behaviour of tooth enamel.

    Science.gov (United States)

    Xie, Zonghan; Swain, Michael; Munroe, Paul; Hoffman, Mark

    2008-06-01

    Tooth enamel is the hardest tissue in the human body with a complex hierarchical structure. Enamel hypomineralisation--a developmental defect--has been reported to cause a marked reduction in the mechanical properties of enamel and loss of dental function. We discover a distinctive difference in the inelastic deformation mechanism between sound and hypomineralised enamels that is apparently controlled by microstructural variation. For sound enamel, when subjected to mechanical forces the controlling deformation mechanism was distributed shearing within nanometre thick protein layer between its constituent mineral crystals; whereas for hypomineralised enamel microcracking and subsequent crack growth were more evident in its less densely packed microstructure. We develop a mechanical model that not only identifies the critical parameters, i.e., the thickness and shear properties of enamels, that regulate the mechanical behaviour of enamel, but also explains the degradation of hypomineralised enamel as manifested by its lower resistance to deformation and propensity for catastrophic failure. With support of experimental data, we conclude that for sound enamel an optimal microstructure has been developed that endows enamel with remarkable structural integrity for durable mechanical function.

  6. Quantitative assessment of the enamel machinability in tooth preparation with dental diamond burs.

    Science.gov (United States)

    Song, Xiao-Fei; Jin, Chen-Xin; Yin, Ling

    2015-01-01

    Enamel cutting using dental handpieces is a critical process in tooth preparation for dental restorations and treatment but the machinability of enamel is poorly understood. This paper reports on the first quantitative assessment of the enamel machinability using computer-assisted numerical control, high-speed data acquisition, and force sensing systems. The enamel machinability in terms of cutting forces, force ratio, cutting torque, cutting speed and specific cutting energy were characterized in relation to enamel surface orientation, specific material removal rate and diamond bur grit size. The results show that enamel surface orientation, specific material removal rate and diamond bur grit size critically affected the enamel cutting capability. Cutting buccal/lingual surfaces resulted in significantly higher tangential and normal forces, torques and specific energy (pmachinability for clinical dental practice. Copyright © 2014 Elsevier Ltd. All rights reserved.

  7. Error in assessing the absorbed dose from the EPR signal from dental enamel

    International Nuclear Information System (INIS)

    Kleshchenko, E.D.; Kushnereva, K.K.

    1997-01-01

    Dose measurements from EPR signals from dental enamel were analyzed in a random sampling of 100 teeth extracted in liquidators of the Chernobyl accident aftermath and the EPR spectra of dental enamel of 80 intact teeth from children studied. The mean square deviation of enamel sensitivity to ionizing radiation in some teeth is approximately 0.3 of the mean sensitivity value. The variability of the nature EPR spectrum of dental enamel limits in principle the lower threshold of EPR-measured 60 mGy doses. When assessing the individual absorbed doses from the EPR signal from dental enamel without additional exposure it is necessary to bear in mind the extra error of approximately 6-% at a confidence probability P=0.95 caused by the variability of enamel sensitivity to radiation in some teeth. This additional error may be ruled out by graduated additional exposure of the examined enamel samples

  8. Sea otter dental enamel is highly resistant to chipping due to its microstructure.

    Science.gov (United States)

    Ziscovici, Charles; Lucas, Peter W; Constantino, Paul J; Bromage, Timothy G; van Casteren, Adam

    2014-10-01

    Dental enamel is prone to damage by chipping with large hard objects at forces that depend on chip size and enamel toughness. Experiments on modern human teeth have suggested that some ante-mortem chips on fossil hominin enamel were produced by bite forces near physiological maxima. Here, we show that equivalent chips in sea otter enamel require even higher forces than human enamel. Increased fracture resistance correlates with more intense enamel prism decussation, often seen also in some fossil hominins. It is possible therefore that enamel chips in such hominins may have formed at even greater forces than currently envisaged. © 2014 The Author(s) Published by the Royal Society. All rights reserved.

  9. Evaluation of the Esthetic Properties of Developmental Defects of Enamel: A Spectrophotometric Clinical Study

    Directory of Open Access Journals (Sweden)

    Fabrizio Guerra

    2015-01-01

    Full Text Available Objectives. Detailed clinical quantification of optical properties of developmental defect of enamel is possible with spectrophotometric evaluation. Developmental defects of enamel (DDE are daily encountered in clinical practice. DDE are an alteration in quality and quantity of the enamel, caused by disruption and/or damage to the enamel organ during amelogenesis. Methods. Several clinical indices have been developed to categorize enamel defects based on their nature, appearance, microscopic features, or cause. A sample of 39 permanent teeth presenting DDE on labial surface was examined using the DDE Modified Index and SpectroShade evaluation. The spectrophotometric approach quantifies L* (luminosity, a* (quantity of green-red, and b* (quantity of blue-yellow of different DDE. Conclusions. SpectroShade evaluation of the optical properties of the enamel defect enhances clinical understanding of severity and extent of the defect and characterizes the enamel alteration in terms of color discrepancy and surface characterization.

  10. Distinguishing between enamel fluorosis and other enamel defects in permanent teeth of children

    Directory of Open Access Journals (Sweden)

    Aira Sabokseir

    2016-02-01

    Full Text Available Background. The inconsistent prevalence of fluorosis for a given level of fluoride in drinking water suggests developmental defects of enamel (DDEs other than fluorosis were being misdiagnosed as fluorosis. The imprecise definition and subjective perception of fluorosis indices could result in misdiagnosis of dental fluorosis. This study was conducted to distinguish genuine fluorosis from fluorosis-resembling defects that could have adverse health-related events as a cause using Early Childhood Events Life-grid method (ECEL. Methods. A study was conducted on 400 9-year-old children from areas with high, optimal and low levels of fluoride in the drinking water of Fars province, Iran. Fluorosis cases were diagnosed on the standardized one view photographs of the anterior teeth using Dean’s and TF (Thylstrup and Fejerskov Indices by calibrated dentists. Agreements between examiners were tested. Early childhood health-related data collected retrospectively by ECEL method were matched with the position of enamel defects. Results. Using both Dean and TF indices three out of four dentists diagnosed that 31.3% (115 children had fluorosis, 58.0%, 29.1%, and 10.0% in high (2.12–2.85 ppm, optimal (0.62–1.22 ppm, and low (0.24–0.29 ppm fluoride areas respectively (p < 0.001. After matching health-related events in the 115 (31.3% of children diagnosed with fluorosis, 31 (8.4% of children had fluorosis which could be matched with their adverse health-related events. This suggests that what was diagnosed as fluorosis were non-fluoride related DDEs that resemble fluorosis. Discussion. The frequently used measures of fluorosis appear to overscore fluorosis. Use of ECEL method to consider health related events relevant to DDEs could help to differentiate between genuine fluorosis and fluorosis-resembling defects.

  11. The efficiency of child formula dentifrices containing different calcium and phosphate compounds on artificial enamel caries.

    Science.gov (United States)

    Rirattanapong, Praphasri; Vongsavan, Kadkao; Saengsirinavin, Chavengkiat; Khumsub, Ploychompoo

    2016-01-01

    Fluoride toothpaste has been extensively used to prevent dental caries. However, the risk of fluorosis is concerning, especially in young children. Calcium phosphate has been an effective remineralizing agent and is present in commercial dental products, with no risk of fluorosis to users. This in vitro study aimed to compare the effects of different calcium phosphate compounds and fluoride-containing dentifrices on artificial caries in primary teeth. Fifty sound primary incisors were coated with nail varnish, leaving two 1 mm 2 windows on the labial surface before immersion in demineralizing solution for 96 hours to produce artificial enamel lesions. Subsequently, one window from each tooth was coated with nail varnish, and all 50 teeth were divided into five groups ( n = 10); group A - deionized water; group B - casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) paste (Tooth Mousse); group C - 500 ppm F (Colgate Spiderman ® ); group D - nonfluoridated toothpaste with triple calcium phosphate (Pureen ® ); and group E - tricalcium phosphate (TCP). Polarized light microscopy and Image-Pro ® Plus software were used to evaluate lesions. After a 7-day pH-cycle, mean lesion depths in groups A, B, C, D, and E had increased by 57.52 ± 10.66%, 33.28 ± 10.16%, 17.04 ± 4.76%, 32.51 ± 8.99%, and 21.76 ± 8.15%, respectively. All data were processed by the Statistical Package for the Social Sciences (version 16.0) software package. Comparison of percentage changes using one-way analysis of variance and Fisher's least squares difference tests at a 95% level of confidence demonstrated that group A was significantly different from the other groups ( P < 0.001). Lesions in groups B and D had a significant lesion progression when compared with groups C and E. All toothpastes in this study had the potential to delay the demineralization progression of artificial enamel caries in primary teeth. The fluoride 500 ppm and TCP toothpastes were equal in the deceleration of

  12. Structural, mechanical and chemical evaluation of molar-incisor hypomineralization-affected enamel: A systematic review.

    Science.gov (United States)

    Elhennawy, Karim; Manton, David John; Crombie, Felicity; Zaslansky, Paul; Radlanski, Ralf J; Jost-Brinkmann, Paul-Georg; Schwendicke, Falk

    2017-11-01

    To systematically assess and contrast reported differences in microstructure, mineral density, mechanical and chemical properties between molar-incisor-hypomineralization-affected (MIH) enamel and unaffected enamel. Studies on extracted human teeth, clinically diagnosed with MIH, reporting on the microstructure, mechanical properties or the chemical composition and comparing them to unaffected enamel were reviewed. Electronic databases (PubMed, Embase and Google Scholar) were screened; hand searches and cross-referencing were also performed. Twenty-two studies were included. Fifteen studies on a total of 201 teeth investigated the structural properties, including ten (141 teeth) on microstructure and seven (60 teeth) on mineral density; six (29 teeth) investigated the mechanical properties and eleven (87 teeth) investigated the chemical properties of MIH-affected enamel and compared them to unaffected enamel. Studies unambiguously found a reduction in mineral quantity and quality (reduced Ca and P content), reduction of hardness and modulus of elasticity (also in the clinically sound-appearing enamel bordering the MIH-lesion), an increase in porosity, carbon/carbonate concentrations and protein content compared to unaffected enamel. were ambiguous with regard to the extent of the lesion through the enamel to the enamel-dentin junction, the Ca/P ratio and the association between clinical appearance and defect severity. There is an understanding of the changes related to MIH-affected enamel. The association of these changes with the clinical appearance and resulting implications for clinical management are unclear. MIH-affected enamel is greatly different from unaffected enamel. This has implications for management strategies. The possibility of correlating the clinical appearance of MIH-affected enamel with the severity of enamel changes and deducing clinical concepts (risk stratification etc.) is limited. Crown Copyright © 2017. Published by Elsevier Ltd. All

  13. Shear bond strength of hydrophilic adhesive systems to enamel.

    Science.gov (United States)

    Hara, A T; Amaral, C M; Pimenta, L A; Sinhoreti, M A

    1999-08-01

    To compare the enamel shear bond strength of four hydrophilic adhesive systems: one multiple-bottle (Scotchbond Multi-Purpose Plus), two one-bottle (Stae, Single Bond) and one self-etching (Etch & Prime). 120 bovine incisor teeth were obtained, embedded in polyester resin, polished to 600 grit to form standardized enamel surfaces, and randomly assigned to four groups (n = 30). Each adhesive system was used on enamel according to the manufacturer's instructions, and resin-based composite (Z100) cylinders with 3 mm diameter and 5 mm height were bonded. Specimens were stored in humid environment for 1 week, and bond strength was determined using a universal testing machine, at a crosshead speed of 0.5 mm/minute. The mean shear bond strength values (MPa +/- SD) were: Single Bond: 24.28 +/- 5.27 (a); Scotchbond Multi-Purpose Plus: 21.18 +/- 4.35 (ab); Stae: 19.56 +/- 4.71 (b); Etch & Prime 3.0: 15.13 +/- 4.92 (c). ANOVA revealed significant difference in means (P < 0.01) and Tukey's test showed the statistical differences that are expressed by different letters for each group. It could be concluded that the self-etching adhesive system did not provide as good a bond to enamel surface, as did the one- and multiple-bottle systems.

  14. Effect of Galla chinensis on enhancing remineralization of enamel crystals

    Energy Technology Data Exchange (ETDEWEB)

    Cheng Lei; Huang Shengbin [State Key Laboratory of Oral Disease, Sichuan University, Chengdu (China); Li Jiyao; Zhou Xuedong, E-mail: stonedentist@yahoo.c [West China College of Stomatology, Sichuan University, Chengdu (China)

    2009-06-15

    The aim of this scanning electron microscopy (SEM) study was to investigate the effect of chemical compounds of Galla chinensis (GCE, gallic acid) on the remineralization of enamel crystals in vitro. Bovine enamel blocks with an in vitro produced initial lesion were used. The lesions were subjected to a pH-cycling regime for 12 days. Each daily cycle included 4 x 1 min applications with one of six treatments: group A: 1000 ppm F aq. (as NaF, positive control); group B: deionized water (DDW, negative control); group C: 4000 ppm crude aqueous extract of GCE; group D: 4000 ppm gallic acid; group E: 4000 ppm GCE with 1000 ppm F; group F: 4000 ppm gallic acid with 1000 ppm F. The surface and vertical section of the enamel lesions were analyzed by SEM. The results indicated that the chemical compounds of G. chinensis could regulate the de-/remineralization balance through influencing the morphology and structure of enamel crystals, and the mechanisms seem to be different for GCE and gallic acid.

  15. Effect of Galla chinensis on enhancing remineralization of enamel crystals

    International Nuclear Information System (INIS)

    Cheng Lei; Huang Shengbin; Li Jiyao; Zhou Xuedong

    2009-01-01

    The aim of this scanning electron microscopy (SEM) study was to investigate the effect of chemical compounds of Galla chinensis (GCE, gallic acid) on the remineralization of enamel crystals in vitro. Bovine enamel blocks with an in vitro produced initial lesion were used. The lesions were subjected to a pH-cycling regime for 12 days. Each daily cycle included 4 x 1 min applications with one of six treatments: group A: 1000 ppm F aq. (as NaF, positive control); group B: deionized water (DDW, negative control); group C: 4000 ppm crude aqueous extract of GCE; group D: 4000 ppm gallic acid; group E: 4000 ppm GCE with 1000 ppm F; group F: 4000 ppm gallic acid with 1000 ppm F. The surface and vertical section of the enamel lesions were analyzed by SEM. The results indicated that the chemical compounds of G. chinensis could regulate the de-/remineralization balance through influencing the morphology and structure of enamel crystals, and the mechanisms seem to be different for GCE and gallic acid.

  16. The remineralisation of enamel: a review of the literature.

    Science.gov (United States)

    Li, Xiaoke; Wang, Jinfang; Joiner, Andrew; Chang, Jiang

    2014-06-01

    The purpose of this paper is to review current knowledge and technologies for tooth remineralisation. The literature was searched using the "Scopus" and "Web of Knowledge" database from the year 1971, with principal key words of *miner*, teeth and enamel. Language was restricted to English. Original studies and reviews were included. Conference papers and posters were excluded. The importance of oral health for patients and consumers has seen a steady increase in the number of tooth remineralisation agents, products and procedures over recent years. Concomitantly, there has been continued publication of both in vivo and in vitro tooth remineralisation and demineralisation studies. It is clear that fluoride treatments are generally effective in helping to protect the dental enamel from demineralisation and enhancing remineralisation. Continued efforts to increase the efficacy of fluoride have been made, in particular, by the addition of calcium salts or calcium containing materials to oral care products which may enhance the delivery and retention of fluoride into the oral cavity. In addition, the calcium salts or materials may act as additional sources of calcium to promote enamel remineralisation or reduce demineralisation processes. Inspired by the concept of bioactive materials for bone repair and regeneration, bioglass and in particular calcium silicate type materials show potential for enamel health benefits and is a growing area of research. © 2014 Elsevier Ltd. All rights reserved.

  17. Quantitative evaluation of the enamel caries which were treated with ...

    African Journals Online (AJOL)

    Objectives: The aim of this in vivo study was to quantitatively evaluate the remineralization of the enamel caries on smooth and occlusal surfaces using DIAGNOdent, after daily application of casein phosphopeptide‑amorphous calcium fluoride phosphate (CPP‑ACFP). Materials and Methods: Thirty volunteers, aged 18–30 ...

  18. Human and bovine enamel erosion under 'single-drink' conditions

    NARCIS (Netherlands)

    White, Andrew J.; Yorath, Celyn; ten Hengel, Valerie; Leary, Sam D.; Huysmans, Marie-Charlotte D. N. J. M.; Barbour, Michele E.

    2010-01-01

    Tooth-surface pH is lowered, during drinking, to a value close to the pH of the drink itself. After the drink is swallowed, the pH rises to baseline values but this process can take several minutes. Few techniques can quantify enamel erosion at timescales representative of single drinks. The

  19. Argon laser induced changes to the carbonate content of enamel

    International Nuclear Information System (INIS)

    Ziglo, M.J.; Nelson, A.E.; Heo, G.; Major, P.W.

    2009-01-01

    Argon laser irradiation can be used to cure orthodontic brackets onto teeth in significantly less time than conventional curing lights. In addition, it has been shown that the argon laser seems to impart a demineralization resistance to the enamel. The purpose of this study was to use surface science techniques to ascertain if this demineralization resistance is possibly a result of a decrease in the carbonate content of enamel. Eleven mandibular third molars previously scheduled for extraction were collected and used in the present study. The teeth were sectioned in two and randomly assigned to either the argon laser (457-502 nm; 250 mW cm -2 ) or the control (no treatment) group. The sections assigned to the argon laser group were cured for 10 s and analyzed. To exaggerate any potential changes the experimental sections were then exposed to a further 110 s of argon laser irradiation. Surface analysis was performed using X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). The results showed no statistically significant change in the carbonate content of enamel after argon laser irradiation (p > 0.05). Thus, it is suggested that any demineralization resistance imparted to the enamel surface by argon laser irradiation is not due to alterations in carbonate content.

  20. Argon laser induced changes to the carbonate content of enamel

    Energy Technology Data Exchange (ETDEWEB)

    Ziglo, M.J. [Orthodontic Graduate Program, Faculty of Medicine and Dentistry, University of Alberta, Private Practice, Regina, Saskatchewan (Canada); Nelson, A.E., E-mail: aenelson@dow.com [Department of Chemical and Materials Engineering, Faculty of Engineering, University of Alberta (Canada); Heo, G.; Major, P.W. [Orthodontic Graduate Program, Faculty of Medicine and Dentistry, University of Alberta (Canada)

    2009-05-15

    Argon laser irradiation can be used to cure orthodontic brackets onto teeth in significantly less time than conventional curing lights. In addition, it has been shown that the argon laser seems to impart a demineralization resistance to the enamel. The purpose of this study was to use surface science techniques to ascertain if this demineralization resistance is possibly a result of a decrease in the carbonate content of enamel. Eleven mandibular third molars previously scheduled for extraction were collected and used in the present study. The teeth were sectioned in two and randomly assigned to either the argon laser (457-502 nm; 250 mW cm{sup -2}) or the control (no treatment) group. The sections assigned to the argon laser group were cured for 10 s and analyzed. To exaggerate any potential changes the experimental sections were then exposed to a further 110 s of argon laser irradiation. Surface analysis was performed using X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). The results showed no statistically significant change in the carbonate content of enamel after argon laser irradiation (p > 0.05). Thus, it is suggested that any demineralization resistance imparted to the enamel surface by argon laser irradiation is not due to alterations in carbonate content.

  1. Argon laser induced changes to the carbonate content of enamel

    Science.gov (United States)

    Ziglo, M. J.; Nelson, A. E.; Heo, G.; Major, P. W.

    2009-05-01

    Argon laser irradiation can be used to cure orthodontic brackets onto teeth in significantly less time than conventional curing lights. In addition, it has been shown that the argon laser seems to impart a demineralization resistance to the enamel. The purpose of this study was to use surface science techniques to ascertain if this demineralization resistance is possibly a result of a decrease in the carbonate content of enamel. Eleven mandibular third molars previously scheduled for extraction were collected and used in the present study. The teeth were sectioned in two and randomly assigned to either the argon laser (457-502 nm; 250 mW cm -2) or the control (no treatment) group. The sections assigned to the argon laser group were cured for 10 s and analyzed. To exaggerate any potential changes the experimental sections were then exposed to a further 110 s of argon laser irradiation. Surface analysis was performed using X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). The results showed no statistically significant change in the carbonate content of enamel after argon laser irradiation ( p > 0.05). Thus, it is suggested that any demineralization resistance imparted to the enamel surface by argon laser irradiation is not due to alterations in carbonate content.

  2. Diffusion of calcium and fluride ions in bovine enamel

    NARCIS (Netherlands)

    Flim, Gerrit Jan

    1976-01-01

    This thesis deals with the diffusion of calcium and fluoride ions in bovine enamel, Special attention was given to the mechanism of this diffusion, The experiments were carried out with radioactive labeled ions. The information obtained is relevant with respect to de- and remineralization processes

  3. Elevated fluoride products enhance remineralization of advanced enamel lesions

    NARCIS (Netherlands)

    ten Cate, J.M.; Buijs, M.J.; Chaussain Miller, C.; Exterkate, R.A.M.

    2008-01-01

    Caries prevention might benefit from the use of toothpastes containing over 1500 ppm F. With few clinical studies available, the aim of this pH-cycling study was to investigate the dose response between 0 and 5000 ppm F of de- and remineralization of advanced (> 150 µm) enamel lesions. Treatments

  4. Microtensile bond strength to enamel affected by hypoplastic amelogenesis imperfecta.

    Science.gov (United States)

    Yaman, Batu Can; Ozer, Fusun; Cabukusta, Cigdem Sozen; Eren, Meltem M; Koray, Fatma; Blatz, Markus B

    2014-02-01

    This study compared the microtensile bond strengths (μTBS) of two different self-etching (SE) and etchand- rinse (ER) adhesive systems to enamel affected by hypoplastic amelogenesis imperfecta (HPAI) and analyzed the enamel etching patterns created by the two adhesive systems using scanning electron microscopy (SEM). Sixteen extracted HPAI-affected molars were used for the bond strength tests and 2 molars were examined under SEM for etching patterns. The control groups consisted of 12 healthy third molars for μTBS tests and two molars for SEM. Mesial and distal surfaces of the teeth were slightly ground flat. The adhesive systems and composite resin were applied to the flat enamel surfaces according to the manufacturers' instructions. The tooth slabs containing composite resin material on their mesial and distal surfaces were cut in the mesio-distal direction with a slow-speed diamond saw. The slabs were cut again to obtain square, 1-mm-thick sticks. Finally, each stick was divided into halves and placed in the μTBS tester. Bond strength tests were performed at a speed of 0.5 mm/min. Data were analyzed with two-way ANOVA and Tukey's tests. There was no significant difference between the bond strength values of ER and SE adhesives (p > 0.05). However, significant differences were found between HPAI and control groups (p systems provide similar bond strengths to HPAI-affected enamel surfaces.

  5. Contact fatigue of human enamel: Experiments, mechanisms and modeling.

    Science.gov (United States)

    Gao, S S; An, B B; Yahyazadehfar, M; Zhang, D; Arola, D D

    2016-07-01

    Cyclic contact between natural tooth structure and engineered ceramics is increasingly common. Fatigue of the enamel due to cyclic contact is rarely considered. The objectives of this investigation were to evaluate the fatigue behavior of human enamel by cyclic contact, and to assess the extent of damage over clinically relevant conditions. Cyclic contact experiments were conducted using the crowns of caries-free molars obtained from young donors. The cuspal locations were polished flat and subjected to cyclic contact with a spherical indenter of alumina at 2Hz. The progression of damage was monitored through the evolution in contact displacement, changes in the contact hysteresis and characteristics of the fracture pattern. The contact fatigue life diagram exhibited a decrease in cycles to failure with increasing cyclic load magnitude. Two distinct trends were identified, which corresponded to the development and propagation of a combination of cylindrical and radial cracks. Under contact loads of less than 400N, enamel rod decussation resisted the growth of subsurface cracks. However, at greater loads the damage progressed rapidly and accelerated fatigue failure. Overall, cyclic contact between ceramic appliances and natural tooth structure causes fatigue of the enamel. The extent of damage is dependent on the magnitude of cyclic stress and the ability of the decussation to arrest the fatigue damage. Copyright © 2016 Elsevier Ltd. All rights reserved.

  6. Micro-indentation fracture behavior of human enamel.

    Science.gov (United States)

    Padmanabhan, Sanosh Kunjalukkal; Balakrishnan, Avinash; Chu, Min-Cheol; Kim, Taik Nam; Cho, Seong Jai

    2010-01-01

    The purpose of this study was to determine the crack resistance behavior (K(R)) of human enamel in relation to its microstructure. Human molar teeth were precision cut, polished and tested using Vickers micro-indentation at different loads ranging from 0.98 to 9.8 N. Five indentation load levels were considered, 20 indentation cracks for each load level were introduced on the surface of the test specimen (10 indentations per tooth) and their variability was evaluated using Weibull statistics and an empirical model. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were used to analyze the crack morphology and propagation mechanisms involved. The results showed that enamel exhibited increasing cracking resistance (K(R)) with increasing load. It was found that the crack propagation mainly depended on the location and the microstructure it encountered. SEM showed the formation of crack bridges and crack deflection near the indentation crack tip. The crack mode was of Palmqvist type even at larger loads of 9.8 N. This was mainly attributed to the large process zone created by the interwoven lamellar rod like microstructure exhibited by the enamel surface. This study shows that there are still considerable prospects for improving dental ceramics and for mimicking the enamel structure developed by nature.

  7. HeNe-laser light scattering by human dental enamel

    NARCIS (Netherlands)

    Zijp, [No Value; tenBosch, JJ; Groenhuis, RAJ

    1995-01-01

    Knowledge of the optical properties of tooth enamel and an understanding of the origin of these properties are necessary for the development of new optical methods for caries diagnosis and the measurement of tooth color. We measured the scattering intensity functions for HeNe-laser light of 80- to

  8. Composition of enamel pellicle from dental erosion patients.

    Science.gov (United States)

    Carpenter, G; Cotroneo, E; Moazzez, R; Rojas-Serrano, M; Donaldson, N; Austin, R; Zaidel, L; Bartlett, D; Proctor, G

    2014-01-01

    Oral health is dependent upon a thin mobile film of saliva on soft and hard tissues. Salivary proteins adhere to teeth to form the acquired enamel pellicle which is believed to protect teeth from acid erosion. This study investigated whether patients suffering diet-induced dental erosion had altered enamel pellicles. Thirty patients suffering erosion were compared to healthy age-matched controls. Subjects wore a maxillary splint holding hydroxyapatite and human enamel blocks for 1 h. The acquired enamel pellicle was removed from the blocks and compared to the natural incisor pellicle. Basic Erosive Wear Examination scores confirmed that dental erosion was present in erosion patients and absent from healthy age-matched controls. Erosion patients had half the amount of proteins (BCA assay) within the acquired pellicle forming on splint blocks compared to normal controls (p erosion patients (p erosion patients and healthy controls. In summary, the formation of new acquired pellicles on surfaces was reduced in erosion patients, which may explain their greater susceptibility to acid erosion of teeth. © 2014 S. Karger AG, Basel.

  9. Spectrally enhanced image resolution of tooth enamel surfaces

    Science.gov (United States)

    Zhang, Liang; Nelson, Leonard Y.; Berg, Joel H.; Seibel, Eric J.

    2012-01-01

    Short-wavelength 405 nm laser illumination of surface dental enamel using an ultrathin scanning fiber endoscope (SFE) produced enhanced detail of dental topography. The surfaces of human extracted teeth and artificial erosions were imaged with 405 nm, 444 nm, 532 nm, or 635 nm illumination lasers. The obtained images were then processed offline to compensate for any differences in the illumination beam diameters between the different lasers. Scattering and absorption coefficients for a Monte Carlo model of light propagation in dental enamel for 405 nm were scaled from published data at 532 nm and 633 nm. The value of the scattering coefficient used in the model was scaled from the coefficients at 532 nm and 633 nm by the inverse third power of wavelength. Simulations showed that the penetration depth of short-wavelength illumination is localized close to the enamel surface, while long-wavelength illumination travels much further and is backscattered from greater depths. Therefore, images obtained using short wavelength laser are not contaminated by the superposition of light reflected from enamel tissue at greater depths. Hence, the SFE with short-wavelength illumination may make it possible to visualize surface manifestations of phenomena such as demineralization, thus better aiding the clinician in the detection of early caries.

  10. The aesthetic and functional properties of enamel coatings on steel

    International Nuclear Information System (INIS)

    Scrinzi, E.; Rossi, S.

    2010-01-01

    In this work, the aesthetic and functional properties of enamelled steel panels were investigated. Enamelling is one of the oldest techniques to protect metallic substrates from corrosive phenomena and to improve the aesthetic aspects. This kind of coating is still up-to-date because of its durability, the possibility of creating different aesthetic effects and the eco-sustainability of the production process. Therefore, these kinds of coatings present a great potential in the field of product design. In this work, the durability and the change in the surface properties of different types of enamels are investigated. Chemical resistance, abrasion resistance and ultraviolet radiation (UV) exposure resistance were studied. To determine the chemical resistance, the samples were immersed in acid and basic solutions. Gloss and colour changes were measured. The falling abrasive test was used to evaluate the abrasion resistance: gloss changes were measured to determine the loss of aesthetic properties, and electrochemical impedance spectroscopy was used to evaluate the loss of protective properties. Gloss and colour changes were measured after 1000 h of UV exposure. Optical microscopy and environmental scanning electron microscopy were used to study the morphology of the damage and correlate it to the gloss and colour changes. All the samples presented good resistance in acid solution and good UV exposure resistance. For the other tests the results varied and were correlated to the characteristics of the enamels in terms of composition, thickness, surface roughness and application technique.

  11. Characterization of glazes, enamels and oxides by XRF

    International Nuclear Information System (INIS)

    Mbarek, Iheb

    2009-01-01

    The purpose of this work is to control the technique of X-ray fluorescence, both in qualitative and quantitative characterization for ceramic glazes, enamels and oxides. it's a recent subject of investigation, its purpose is to discover the presence of toxic substances (Pb, Cd, Sn, As ..) and their quantities if it exists in the manufacturing materials.

  12. Magnesium stable isotope ecology using mammal tooth enamel

    Science.gov (United States)

    Martin, Jeremy E.; Vance, Derek; Balter, Vincent

    2015-01-01

    Geochemical inferences on ancient diet using bone and enamel apatite rely mainly on carbon isotope ratios (δ13C) and to a lesser extent on strontium/calcium (Sr/Ca) and barium/calcium (Ba/Ca) elemental ratios. Recent developments in nontraditional stable isotopes provide an unprecedented opportunity to use additional paleodietary proxies to disentangle complex diets such as omnivory. Of particular relevance for paleodietary reconstruction are metals present in large quantity in bone and enamel apatite, providing that biologically mediated fractionation processes are constrained. Calcium isotope ratios (δ44Ca) meet these criteria but exhibit complex ecological patterning. Stable magnesium isotope ratios (δ26Mg) also meet these criteria but a comprehensive understanding of its variability awaits new isotopic data. Here, 11 extant mammal species of known ecology from a single locality in equatorial Africa were sampled for tooth enamel and, together with vegetation and feces, analyzed for δ26Mg, δ13C, Sr/Ca, and Ba/Ca ratios. The results demonstrate that δ26Mg incorporated in tooth enamel becomes heavier from strict herbivores to omnivores/faunivores. Using data from experimentally raised sheep, we suggest that this 26Mg enrichment up the trophic chain is due to a 26Mg enrichment in muscle relative to bone. Notably, it is possible to distinguish omnivores from herbivores, using δ26Mg coupled to Ba/Ca ratios. The potential effects of metabolic and dietary changes on the enamel δ26Mg composition remain to be explored but, in the future, multiproxy approaches would permit a substantial refinement of dietary behaviors or enable accurate trophic reconstruction despite specimen-limited sampling, as is often the case for fossil assemblages.

  13. Effects of bleaching agents on human enamel light reflectance.

    Science.gov (United States)

    Markovic, Ljubisa; Fotouhi, Kasra; Lorenz, Heribert; Jordan, Rainer A; Gaengler, Peter; Zimmer, Stefan

    2010-01-01

    Tooth whitening has been associated with splitting-up chromogenic molecules by hydrogen peroxides. Though micromorphological alterations are well documented, little is known about optical changes as a function of shifting in wavelengths. Therefore, the aim of the current study was to measure reflectance changes after bleaching in vitro by using a spectrometer. Forty-eight enamel slabs (diameter = 5 mm) were prepared from the sound enamel of extracted human teeth that were: 1) fully impacted, 2) from juveniles ages 10 to 16 years, 3) from adults 35 to 45 years of age and 4) from seniors older than age 65. In all specimens, the baseline total reflectance measurement was performed with a computer-assisted spectrometer (Ocean Optics, Dunedin, FL, USA) within wavelengths (wl) from 430 nm to 800 nm. Four enamel samples of each age group were exposed to either 10% or 15% carbamide peroxide (Illuminé Home, Dentsply, Konstanz, Germany) or 35% hydrogen peroxide (Pola Office, SDI Limited, Victoria, Australia). After surface treatment, all slabs underwent total reflectance measurement again. Statistical analysis was calculated at wl 450, 500 and 750 nm using the Student's paired t-test and one-way variance analysis. Total reflectance significantly increased after bleaching at all enamel maturation stages, irrespective of the bleaching agent concentration, for wl 450 nm (blue) and 500 nm (green) with penamel from adults and seniors (pwhitening of the dental enamel works at different maturation stages, even in impacted teeth. This effect is irrespective of the bleaching protocol used and the bleaching agent concentration.

  14. THE EFFECT OF IRRADIATION ON ENAMEL MICRO-STRUCTURE CHANGES

    Directory of Open Access Journals (Sweden)

    Harun Gunawan

    2015-06-01

    Full Text Available Radiotherapy plays an important role in the management of head and neck carcinoma therapy. The radiation dose ranges from 40 – 70 Gy, depends on the severity and location of the malignancy. Many patients experience an increased dental caries or sensitivity occurrence following radiotherapy. The objective of this study is to analyze the enamel micro-structure changes after irradiation. Nine polished enamel slabs were prepared from impacted 3rd molars. The slabs were flushed in non-ionic distilled water and dried by using air spray and divided into 3 groups, the control, 20 Gy and 40 Gy irradiation group. Irradiations were performed from Co60 using Gammacell-220E, with duration variables to produce the irradiation doses of 20 and 40 Gy. Philips pW370-XRD was used to examine specimen microstructure changes after irradiation. 1-way ANOVA was used for statistics analysis. It was revealed that grain size after 40 Gy irradiation was 66.29±2.7 nm, and after 20 Gy was 51.64±15.8 whilst 43.95±11.1 nm for the control group. The micro-stain deviation of the 40 Gy group was 0.594±0.15 N/m, and 0.45±2.6 N/m for the 20 Gy group, and 0.378±0.27 N/m for control group. Statistic analysis showed significant grain size differences between 40 Gy compared to both 20 Gy and control groups, but not between 20 Gy compared to the control group. Similarly, there were micro-stain differences between 40 Gy compared to 20 Gy and control groups, but not between 20 Gy compared to control group. It was concluded that irradiation with 40 Gy caused elevation of the enamel microstrain and apaite grainsize. Elevation of the enamel microstrain could lead to enamel crack and gave hypersensitive sensation.

  15. Enamel Bond Strength of New Universal Adhesive Bonding Agents.

    Science.gov (United States)

    McLean, D E; Meyers, E J; Guillory, V L; Vandewalle, K S

    2015-01-01

    Universal bonding agents have been introduced for use as self-etch or etch-and-rinse adhesives depending on the dental substrate and clinician's preference. The purpose of this study was to evaluate the shear bond strength (SBS) of composite to enamel using universal adhesives compared to a self-etch adhesive when applied in self-etch and etch-and-rinse modes over time. Extracted human third molars were used to create 120 enamel specimens. The specimens were ground flat and randomly divided into three groups: two universal adhesives and one self-etch adhesive. Each group was then subdivided, with half the specimens bonded in self-etch mode and half in etch-and-rinse mode. The adhesives were applied as per manufacturers' instructions, and composite was bonded using a standardized mold and cured incrementally. The groups were further divided into two subgroups with 10 specimens each. One subgroup was stored for 24 hours and the second for six months in 37°C distilled water and tested in shear. Failure mode was also determined for each specimen. A three-way analysis of variance (ANOVA) found a significant difference between groups based on bonding agent (p0.05). Clearfil SE in etch-and-rinse and self-etch modes had more mixed fractures than either universal adhesive in either mode. Etching enamel significantly increased the SBS of composite to enamel. Clearfil SE had significantly greater bond strength to enamel than either universal adhesive, which were not significantly different from each other.

  16. Preliminary surface analysis of etched, bleached, and normal bovine enamel

    International Nuclear Information System (INIS)

    Ruse, N.D.; Smith, D.C.; Torneck, C.D.; Titley, K.C.

    1990-01-01

    X-ray photoelectron spectroscopic (XPS) and secondary ion-mass spectroscopic (SIMS) analyses were performed on unground un-pumiced, unground pumiced, and ground labial enamel surfaces of young bovine incisors exposed to four different treatments: (1) immersion in 35% H2O2 for 60 min; (2) immersion in 37% H3PO4 for 60 s; (3) immersion in 35% H2O2 for 60 min, in distilled water for two min, and in 37% H3PO4 for 60 s; (4) immersion in 37% H3PO4 for 60 s, in distilled water for two min, and in 35% H2O2 for 60 min. Untreated unground un-pumiced, unground pumiced, and ground enamel surfaces, as well as synthetic hydroxyapatite surfaces, served as controls for intra-tooth evaluations of the effects of different treatments. The analyses indicated that exposure to 35% H2O2 alone, besides increasing the nitrogen content, produced no other significant change in the elemental composition of any of the enamel surfaces investigated. Exposure to 37% H3PO4, however, produced a marked decrease in calcium (Ca) and phosphorus (P) concentrations and an increase in carbon (C) and nitrogen (N) concentrations in unground un-pumiced specimens only, and a decrease in C concentration in ground specimens. These results suggest that the reported decrease in the adhesive bond strength of resin to 35% H2O2-treated enamel is not caused by a change in the elemental composition of treated enamel surfaces. They also suggest that an organic-rich layer, unaffected by acid-etching, may be present on the unground un-pumiced surface of young bovine incisors. This layer can be removed by thorough pumicing or by grinding. An awareness of its presence is important when young bovine teeth are used in a model system for evaluation of resin adhesiveness

  17. A distinct role of pectate lyases in the formation of feeding structures induced by cyst and root-knot nematodes.

    Science.gov (United States)

    Wieczorek, K; Elashry, A; Quentin, M; Grundler, F M W; Favery, B; Seifert, G J; Bohlmann, H

    2014-09-01

    Pectin in the primary plant cell wall is thought to be responsible for its porosity, charge density, and microfibril spacing and is the main component of the middle lamella. Plant-parasitic nematodes secrete cell wall-degrading enzymes that macerate the plant tissue, facilitating the penetration and migration within the roots. In sedentary endoparasitic nematodes, these enzymes are released only during the migration of infective juveniles through the root. Later, nematodes manipulate the expression of host plant genes, including various cell wall enzymes, in order to induce specific feeding sites. In this study, we investigated expression of two Arabidopsis pectate lyase-like genes (PLL), PLL18 (At3g27400) and PLL19 (At4g24780), together with pectic epitopes with different degrees of methylesterification in both syncytia induced by the cyst nematode Heterodera schachtii and giant cells induced by the root-knot nematode Meloidogyne incognita. We confirmed upregulation of PLL18 and PLL19 in both types of feeding sites with quantitative reverse-transcriptase polymerase chain reaction (RT-PCR) and in situ RT-PCR. Furthermore, the functional analysis of mutants demonstrated the important role of both PLL genes in the development and maintenance of syncytia but not giant cells. Our results show that both enzymes play distinct roles in different infected root tissues as well as during parasitism of different nematodes.

  18. Camel molar tooth enamel response to gamma rays using EPR spectroscopy.

    Science.gov (United States)

    El-Faramawy, N A; El-Somany, I; Mansour, A; Maghraby, A M; Eissa, H; Wieser, A

    2018-03-01

    Tooth enamel samples from molar teeth of camel were prepared using a combined procedure of mechanical and chemical tooth treatment. Based on electron paramagnetic resonance (EPR) spectroscopy, the dose response of tooth enamel samples was examined and compared to that of human enamel. The EPR dose response of the tooth enamel samples was obtained through irradiation to gamma doses from 1 Gy up to 100 kGy. It was found that the radiation-induced EPR signal increased linearly with gamma dose for all studied tooth enamel samples, up to about 15 kGy. At higher doses, the dose response curve leveled off. The results revealed that the location of the native signal of camel tooth enamel was similar to that of enamel from human molars at 2.00644, but different from that of enamel from cows and goats. In addition, the peak-to-peak width (ΔH pp ) for human and camel molar teeth was similar. It was also found that the response of camel enamel to gamma radiation was 36% lower than that of human enamel. In conclusion, the results indicate the suitability of camel teeth for retrospective gamma dosimetry.

  19. Synchrotron radiation microbeam X-ray fluorescence analysis of zinc concentration in remineralized enamel in situ.

    Science.gov (United States)

    Matsunaga, Tsunenori; Ishizaki, Hidetaka; Tanabe, Shuji; Hayashi, Yoshihiko

    2009-05-01

    Remineralization is an indispensable phenomenon during the natural healing process of enamel decay. The incorporation of zinc (Zn) into enamel crystal could accelerate this remineralization. The present study was designed to investigate the concentration and distribution of Zn in remineralized enamel after gum chewing. The experiment was performed at the Photon Factory. Synchrotron radiation was monochromatized and X-rays were focused into a small beam spot. The X-ray fluorescence (XRF) from the sample was detected with a silicon (Si) (lithium (Li)) detector. X-ray beam energy was tuned to detect Zn. The examined samples were small enamel fragments remineralized after chewing calcium phosphate-containing gum in situ. The incorporation of Zn atom into hydroxyapatite (OHAP), the main component of enamel, was measured using Zn K-edge extended X-ray absorption fine structure (EXAFS) with fluorescence mode at the SPring-8. A high concentration of Zn was detected in a superficial area 10-microm deep of the sectioned enamel after gum chewing. This concentration increased over that in the intact enamel. The atomic distance between Zn and O in the enamel was calculated using the EXAFS data. The analyzed atomic distances between Zn and O in two sections were 0.237 and 0.240 nm. The present experiments suggest that Zn is effectively incorporated into remineralized enamel through the physiological processes of mineral deposition in the oral cavity through gum-chewing and that Zn substitution probably occurred at the calcium position in enamel hydroxyapatite.

  20. Camel molar tooth enamel response to gamma rays using EPR spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    El-Faramawy, N.A.; El-Somany, I. [Ain Shams University, Physics Department, Faculty of Science, Cairo (Egypt); Mansour, A. [National Center for Radiation Research and Technology, Atomic Energy Authority, Cairo (Egypt); Maghraby, A.M.; Eissa, H. [National Institute of Standards (NIS), Ionizing Radiation Metrology Laboratory, Giza (Egypt); Wieser, A. [Helmholtz Zentrum Muenchen-German Research Center for Environmental Health, Department of Radiation Sciences, Institute of Radiation Protection, Neuherberg (Germany)

    2018-03-15

    Tooth enamel samples from molar teeth of camel were prepared using a combined procedure of mechanical and chemical tooth treatment. Based on electron paramagnetic resonance (EPR) spectroscopy, the dose response of tooth enamel samples was examined and compared to that of human enamel. The EPR dose response of the tooth enamel samples was obtained through irradiation to gamma doses from 1 Gy up to 100 kGy. It was found that the radiation-induced EPR signal increased linearly with gamma dose for all studied tooth enamel samples, up to about 15 kGy. At higher doses, the dose response curve leveled off. The results revealed that the location of the native signal of camel tooth enamel was similar to that of enamel from human molars at 2.00644, but different from that of enamel from cows and goats. In addition, the peak-to-peak width (ΔH{sub pp}) for human and camel molar teeth was similar. It was also found that the response of camel enamel to gamma radiation was 36% lower than that of human enamel. In conclusion, the results indicate the suitability of camel teeth for retrospective gamma dosimetry. (orig.)