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Human Enamel (human + enamel)
Selected AbstractsWear of human enamel and nano-filled composite resin denture teeth under different loading forcesJOURNAL OF ORAL REHABILITATION, Issue 1 2009M. GHAZAL Summary, To evaluate and correlate the two-body wear of human enamel and nano-filled composite resin teeth with the loading forces used in a dual-axis chewing simulator. Three groups of human enamel and three of nano-filled composite resin teeth were tested in a chewing simulator. Zirconia ceramic balls were used as antagonists. The teeth were tested with three different loading forces (20, 49 and 78 N). Wear was analysed by measuring the volume and vertical substance loss using a laser scanner after 300000 chewing cycles. Data were statistically analysed using two-way anova followed by the Scheffé test (P , 0·05). Spearman correlation test was used to determine whether there was a relationship between the loading force and the degree to which the human enamel and composite resin had worn. An increase in the loading force significantly increased the wear of composite resin and of human enamel. The effect of the loading force on the wear was statistically significant at the 0·001 level. Human enamel showed a lower volume and vertical substance loss than composite resin under loading forces of 20 and 49 N and lower vertical loss under loading force of 78 N. The correlation between the volume loss and loading force was statistically significant (r = 0·616, P < 0·001). Nano-filled composite resin and human enamel exhibited different amount of wear under different loading forces. In general, human enamel showed less vertical substance loss than nano-filled composite resin. [source] Human enamel dissolution in citric acid as a function of pH in the range 2.30,pH,6.30 , a nanoindentation studyEUROPEAN JOURNAL OF ORAL SCIENCES, Issue 3 2003Michele E. Barbour The objective of this study was to investigate the dissolution of human enamel in citric acid solutions over a wide range of pH. The in vitro conditions are considered to be relevant to soft drink-induced enamel erosion. Nanoindentation was used to investigate changes in the nanomechanical properties of polished enamel surfaces after exposure to citric acid solutions. Solutions used had 38.1 mmol l,1 citric acid and pH greater than 2.3 but less than 6.3 (2.30 pH 6.30). Samples were exposed to rapidly stirred, constant composition solutions for 120 s. Statistically significant changes in enamel hardness and reduced elastic modulus were observed after exposure to all solutions. There was an approximately linear dependence of enamel hardness on solution pH for 2.90 pH 6.30. Below pH 2.90, enamel is thought to have reached the lowest possible hardness value. The reduction in enamel dissolution caused by an increase in pH of a soft drink is likely to be small. Product modification to reduce the erosive potential of drinks may require additional methods such as addition of calcium salts. [source] Residential mobility and resource use in the Chiribaya polity of southern Peru: strontium isotope analysis of archaeological tooth enamel and boneINTERNATIONAL JOURNAL OF OSTEOARCHAEOLOGY, Issue 6 2007K. J. Knudson Abstract The Chiribaya were a complex polity during the Andean Late Intermediate Period (c. AD 1000,1300) in the Ilo and Moquegua Valleys of southern Peru. Recent research has demonstrated that the Chiribaya polity was a señorío, a confederacy of economically specialised parcialidades. Here we test hypotheses regarding the movement of individuals and resources among the Chiribaya-affiliated sites of Chiribaya Alta, Chiribaya Baja, San Gerónimo and El Yaral, as well as from outside of the Ilo and Moquegua Valleys. Although archaeological human enamel and bone strontium isotope ratios from Chiribaya Baja and San Gerónimo cluster closely, there is a wider variety of strontium isotope ratios observed at Chiribaya Alta and El Yaral. This indicates that individuals buried in cemeteries at these sites had access to a wider variety of resources, and probably moved between different geological zones throughout their lifetimes. Copyright © 2007 John Wiley & Sons, Ltd. [source] Wear of human enamel and nano-filled composite resin denture teeth under different loading forcesJOURNAL OF ORAL REHABILITATION, Issue 1 2009M. GHAZAL Summary, To evaluate and correlate the two-body wear of human enamel and nano-filled composite resin teeth with the loading forces used in a dual-axis chewing simulator. Three groups of human enamel and three of nano-filled composite resin teeth were tested in a chewing simulator. Zirconia ceramic balls were used as antagonists. The teeth were tested with three different loading forces (20, 49 and 78 N). Wear was analysed by measuring the volume and vertical substance loss using a laser scanner after 300000 chewing cycles. Data were statistically analysed using two-way anova followed by the Scheffé test (P , 0·05). Spearman correlation test was used to determine whether there was a relationship between the loading force and the degree to which the human enamel and composite resin had worn. An increase in the loading force significantly increased the wear of composite resin and of human enamel. The effect of the loading force on the wear was statistically significant at the 0·001 level. Human enamel showed a lower volume and vertical substance loss than composite resin under loading forces of 20 and 49 N and lower vertical loss under loading force of 78 N. The correlation between the volume loss and loading force was statistically significant (r = 0·616, P < 0·001). Nano-filled composite resin and human enamel exhibited different amount of wear under different loading forces. In general, human enamel showed less vertical substance loss than nano-filled composite resin. [source] Bending strength and depth of cure of light-cured composite resins irradiated using filters that simulate enamelJOURNAL OF ORAL REHABILITATION, Issue 1 2004H. Arikawa summary, This study evaluates the light-attenuating effects of enamel on the properties of light-cured restorative resins using simple experimental filters. Three filters were designed to replicate the light transmittance characteristics of 0·5, 1·0 and 1·5 mm thick human enamel. The bending strength, depth of cure, and levels of residual monomer for 12 shades of three commercial light-cured composite resins were examined. These resins were cured either using direct irradiation from a light source or irradiation through one of the filters. For all materials, the bending strength and depth of cure of specimens irradiated through a filter were lower and the levels of residual monomer were higher than those found in specimens irradiated directly. The results indicate that the light-attenuating effect of enamel reduces the polymerization efficiency, resulting in poorer mechanical properties of light-cured composite resins. [source] An in vitro wear study of posterior denture tooth materials on human enamelJOURNAL OF ORAL REHABILITATION, Issue 5 2001Y. Abe This in vitro study evaluated the wear effects of five posterior denture tooth materials on human enamel. The tooth specimen was cusp shaped and enamel specimen was formed as a 10 Ç 10 Ç 5 mm plate. All material-enamel combinations were tested using a machine designed to produce sliding contact 20 Ç 104 times at 60 cycles min,1 and a 4-mm sliding distance per stroke in the bucco-lingual direction under a load of 1 kg. Wear analysis was measured as the total height loss of each combination. In addition, the surface roughness (Ra) of each worn specimen was also evaluated. The least total height loss occurred with poly (methyl methacrylate) (PMMA) enamel pair, and the greatest did with porcelain (Po)-enamel pair. The lowest compound Ra value was measured in high-strength resin (HR)-enamel pair, and the highest in Po-enamel pair. These findings suggest that the best combination is PMMA-enamel, and the poorest combination is Po-enamel. [source] Solubility properties of human tooth mineral and pathogenesis of dental cariesORAL DISEASES, Issue 5 2004T Aoba Dental research over the last century has advanced our understanding of the etiology and pathogenesis of caries lesions. Increasing knowledge of the dynamic demineralization/remineralization processes has led to the current consensus that bacteria-mediated tooth destruction can be arrested or even to some degree reversed by adopting fluoride and other preventive measures without using restorative materials. Our experimental approach provided new insight into the stoichiometries and solubility properties of human enamel and dentin mineral. The determination of the solubility product constant on the basis of the stoichiometric model (Ca)5·x(Mg)q(Na)u(HPO4)v(CO3)w(PO4)3·y(OH,F)1·z, verifies the difference in their solubility properties, supporting the phase transformation between tooth mineral and calcium phosphates in a wide range of fluid compositions as found in the oral environment. Further refinement of the stoichiometry and solubility parameters is essential to assess quantitatively the driving force for de- and remineralization of enamel and dentin in the oral fluid environment. Prediction of the effects of a combination of inhibitors and accelerator(s) on remineralization kinetics is also required. In order to develop devices efficient for optimizing remineralization in the lesion body, it is a critical question how, and to what extent, fluoride can compensate for the activity of any inhibitors in the mineralizing media. [source] Structured review of enamel erosion literature (1980,1998): a critical appraisal of experimental, clinical and review publicationsORAL DISEASES, Issue 4 2000G. Maupome OBJECTIVE: To attain an objective account of the methods to measure enamel erosion used in 1980,1998 publications, a structured review of the literature was undertaken. METHODS: Inclusion and exclusion criteria were applied to 731 clinical/experimental research and review reportS. Eighty-five included papers were subsequently rated according to ,hierarchy of evidence' guidelines to assess the strength of the report's design and the relevance of the evidence to replicating enamel erosion in vivo in humanS. Scores were assigned to rate each aspect in the guidelines. RESULTS: A total of 16 clinical, 13 review and 56 experimental papers were assessed; 36.4% were published during 1996,1998.Excluding reviews, 16 papers were qualitative and 56 quantitative; 51 used human enamel. Our classification yielded nine groups of methods (five scoring systems and 26 measurement techniques).CTFPHE (Can Med Assoc J 1992; 147: 443) grading of research reports indicated that 2.8% provided evidence grade I; 20.8%, grade IIa; 63.9%, grade III; and 12.5%, grade IV. CONCLUSIONS: There has been a consistent increase in the body of knowledge. The overall quality of publications has not substantially changed over time. Experimental studies were more often quantitative, and quantitative studies had better research designS. No single group of research methods had obviously superior research designs. [source] Variations in the mechanical properties of Alouatta palliata molar enamelAMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY, Issue 1 2010Laura A. Darnell Abstract Teeth have provided insights into many topics including primate diet, paleobiology, and evolution, due to the fact that they are largely composed of inorganic materials and may remain intact long after an animal is deceased. Previous studies have reported that the mechanical properties, chemistry, and microstructure of human enamel vary with location. This study uses nanoindentation to map out the mechanical properties of Alouatta palliata molar enamel on an axial cross-section of an unworn permanent third molar, a worn permanent first molar, and a worn deciduous first molar. Variations were then correlated with changes in microstructure and chemistry using scanning electron microscopy and electron microprobe techniques. The hardness and Young's modulus varied with location throughout the cross-sections from the occlusal surface to the dentin-enamel junction (DEJ), from the buccal to lingual sides, and also from one tooth to another. These changes in mechanical properties correlated with changes in the organic content of the tooth, which was shown to increase from ,6% near the occlusal surface to ,20% just before the DEJ. Compared to human enamel, the Alouatta enamel showed similar microstructures, chemical constituents, and magnitudes of mechanical properties, but showed less variation in hardness and Young's modulus, despite the very different diet of this species. Am J Phys Anthropol 2010. © 2009 Wiley-Liss, Inc. [source] Erosive potential of beverages sold in Australian schoolsAUSTRALIAN DENTAL JOURNAL, Issue 3 2009NJ Cochrane Abstract Background:, Dental erosion is an increasingly prevalent problem in Australia. The aim of this study was to analyse the composition and erosive potential of beverages sold for consumption in Victorian schools. Methods:, Fifteen drinks were selected and analysed to determine their pH, titratable acidity and ionic composition (calcium, fluoride and inorganic phosphate). The erosive potential of the beverages was measured by analysing weight loss, surface loss and the release of calcium ions from human enamel following a 30-minute or 24-hour exposure. The association of the chemical parameters with the measures of erosion was determined using Spearman's rank correlation. Results:, All beverages tested except the milks and the bottled water produced significant dental erosion in vitro. The only chemical parameter that correlated significantly with all measures of erosion was the initial pH of the beverage (p < 0.01). Levels of fluoride similar to those of Australian reticulated water were found in the carbonated beverages. Conclusions:, The majority of the tested beverages sold from school canteens exhibited erosive potential. [source] Laser-activated fluoride treatment of enamel as prevention against erosionAUSTRALIAN DENTAL JOURNAL, Issue 3 2007J. Vlacic Abstract Background: Erosion is the loss of dental hard tissues from an acidic challenge, often resulting in exposure of dentinal tubules and hypersensitivity to environmental stimuli. Laser-activated fluoride (LAF) therapy with 488nm laser energy has been shown previously to increase the resistance of human enamel and dentine to acid dissolution. The aims of this study were to investigate the action spectrum of LAF in protecting tooth enamel from softening in response to an erosive challenge, and to examine for any temperature change with the treatment. Materials and Methods: Buccal and lingual surfaces of extracted sound molar and premolar teeth were used to prepare matched pairs of enamel slabs (N=10 per group). After application of 1.23% neutral sodium fluoride gel (12 300ppm F ion), slab surfaces were lased with 488, 514.5, 532, 633, 670, 830 or 1064nm wavelength (energy density 15J/cm2; spot size 5mm), then exposed to an erosive challenge (1.0M HCl for five minutes). The Vicker's hardness number (VHN) was recorded before fluoride gel application and again following the acid challenge. Negative controls did not receive laser exposure. Results: All wavelengths of laser light examined provided a protective LAF effect against softening, compared with the negative control surfaces. Conclusion: From these findings, we conclude that the action spectrum of the LAF effect extends across the visible spectrum, providing protection to dental enamel from an erosive challenge. [source] | ||||||||||