Home About us Contact
|
Home About us Contact | ||
|
|
||
Enamel Junction (enamel + junction)
Selected AbstractsEarliest Miocene hominoid from Southeast AsiaAMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY, Issue 2 2004Yutaka Kunimatsu Abstract A new hominoid fossil site, Chiang Muan in northern Thailand, yielded the first finding of a large-bodied Miocene hominoid in Southeast Asia. This specimen (CMu6-1,00) was preliminarily reported by Kunimatsu et al. ([2000a] Primate Res. 16:299). Later, Chaimanee et al. ([ 2003] Nature 422:61,65) reported additional hominoid teeth from the same site, but all of them were collected from younger deposits (the Upper Lignite Member, in Nagaoka and Suganuma [ 2002] Primate Res 18:159,164). The specimen described here (CMu6-1,00) was recovered from the Lower Lignite Member (Nagaoka and Suganuma [ 2002] Primate Res 18:159,164), which is probably several hundred thousand years older than the Upper Lignite Member (Suganuma et al. [ 2002] Primate Res. 18:165,173). This article provides a detailed description of this hominoid specimen and paleontological/geological data of the fossil site at Chiang Muan. The hominoid specimen (CMu6-1,00) is an isolated upper molar (right M1 or M2), similar in size to modern orangutans (Pongo pygmaeus). This upper molar has low and voluminous cusps, relatively thick enamel, and relatively low relief of the dentine/enamel junction, with only a faint remnant of the lingual cingulum. The age of Chiang Muan is estimated to be the latest Middle Miocene (ca. 11,12 Ma), based on the mammalian fossils (Nakaya et al. [ 2002] Primate Res. 18:131,141) and paleomagnetic study (Suganuma et al. [ 2002] Primate Res. 18:165,173). This suggests that the Chiang Muan Hominoid in the present study is an earlier member of Eastern Eurasian Miocene hominoids. Am J Phys Anthropol, 2003. © 2003 Wiley-Liss, Inc. [source] Oral bacterial adhesion forces to biomaterial surfaces constituting the bracket,adhesive,enamel junction in orthodontic treatmentEUROPEAN JOURNAL OF ORAL SCIENCES, Issue 4 2009Li Mei Bacterial adhesion to biomaterial surfaces constituting the bracket,adhesive,enamel junction represents a growing problem in orthodontics, because bacteria can adversely affect treatment by causing demineralization of the enamel surface around the brackets. It is important to know the forces with which bacteria adhere to the surfaces of these junction materials, as the strength of these forces will determine how easy it will be to remove the bacteria. We compared the adhesion forces of five initially colonizing and four cariogenic strains of bacteria to an orthodontic adhesive, stainless steel, and enamel, with and without a salivary conditioning film. Adhesion forces were determined using atomic force microscopy and a bacterial probe. In the absence of a salivary conditioning film, the strongest bacterial adhesion forces occurred to the adhesive surface (,2.9 to ,6.9 nN), while adhesion forces to the enamel surfaces were lowest (,0.8 to ,2.7 nN). In the presence of a salivary conditioning film, adhesion forces were reduced strongly, to less than 1 nN, and the differences between the various materials were reduced. Generally, however, initial colonizers of dental hard surfaces presented stronger adhesion forces to the different materials (,4.7 and ,0.6 nN in the absence and presence of a salivary conditioning film, respectively) than cariogenic strains (,1.8 and ,0.5 nN). [source] Ex vivo evaluation of the accuracy and coefficient of repeatability of three electronic apex locators using a simple mounting model: a preliminary reportINTERNATIONAL ENDODONTIC JOURNAL, Issue 4 2010F. L. C. D'Assunção D'Assunção FLC, Albuquerque DS, Salazar-Silva JR, Dos Santos VC, Sousa JCN.Ex vivo evaluation of the accuracy and coefficient of repeatability of three electronic apex locators using a simple mounting model: a preliminary report. International Endodontic Journal, 43, 269,274, 2010. Abstract Aim, To compare ex vivo the accuracy and coefficient of repeatability of three electronic apex locators in locating the apical constriction. Methodology, Thirty-one single-rooted teeth were used. The teeth were sectioned at the cement,-enamel junction. A mounting model was used for the measurement of electronic length (EL). The Root ZX-II, the Mini Apex Locator and the Novapex were used for electronic measurements. Each electronic measurement was obtained and repeated. After the last measurement, the file was cemented in place, and the apical 4 mm of each root canal was exposed. The distance from the tip of the file to the apical constriction was determined by three investigators and compared with the corresponding ELs. Results, The coefficient of repeatability of all devices was acceptable: Root ZX-II, 0.04 mm; Mini Apex Locator, 0.10 mm; and Novapex, 0.08 mm. There was little variation in inter-examiner agreement; the ,C (Lin) correlation coefficient was 0.83 for examiners 1 and 2, 0.88 for examiners 1 and 3 and 0.99 for examiners 2 and 3. Using the Root ZX-II, 13 of 31 electronic measurements were located at the apical constriction (42%). Otherwise, the tip of the file was not located at the apical constriction in any of the electronic measurements with the other two devices. The Wilcoxon signed rank test did not reveal any statistical difference between the Root ZX-II measurements and the actual length (P = 0.628), but there was a statistical difference between the Mini Apex Locator and Novapex measurements and the actual length position (P < 0.05). Conclusions, The devices tested in this study had a high coefficient of repeatability. The Root ZX-II was accurate, but the Mini Apex Locator and Novapex were not accurate in locating the apical constriction. [source] Influence of tooth age and root section on root dentine dye penetrationINTERNATIONAL ENDODONTIC JOURNAL, Issue 12 2008A. Thaler Abstract Aim, To investigate dye permeability of root dentine according to patients' age, root section and dye penetration time. Methodology, A total of 96 extracted human single-rooted teeth, assigned to four age groups (<30, 30,45, 45,60 and >60 years) were separated at the cemento,enamel junction and root canals were enlarged. The root surfaces were coated with cyanocrylate to prevent external dye penetration and centrifuged in distilled water to eliminate air. For dye penetration the root canals were filled with methylene blue 5%. After 1, 30 and 60 days eight roots per age group were cross-sectioned in 1 mm slices. Dye penetrated areas and the complete dentine areas were digitized and measured. Differences between groups were judged with anova and LSD, P < 0.05 or P < 0.01. Results, The root section, the patients' age and the penetration time influenced significantly the penetrated areas (P < 0.05). After 1 and 30 days significant differences could be found only in the apical root sections between all age groups (P < 0.05). Dye penetration areas systematically decreased with increasing age and also from coronal to apical (P < 0.01). Conclusions, Age influenced dye penetration significantly. Dye penetration also depended on the location (coronal, middle and apical) within the root canal. These findings indicate that there may be a correlation between the tooth age and permeability of root dentine, which may influence the distribution and effectiveness of drugs used for root canal disinfection. [source] Spatial patterns and evolutionary processes in southern South America: A study of dental morphometric variationAMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY, Issue 1 2010Valeria Bernal Abstract The purpose of this article is to examine the patterns of evolutionary relationships between human populations from the later Late Holocene (1,500,100 years BP) of southern South America on the basis of dental morphometric data. We tested the hypotheses that the variation observed in this region would be explained by the existence of populations with different phylogenetic origin or differential action of gene flow and genetic drift. In this study, we analyzed permanent teeth from 17 samples of male and female adult individuals from throughout southern South America. We measured mesiodistal and buccolingual diameters at the base of the crown, along the cement,enamel junction. The results of multiple regression analysis and a mantel correlogram indicate the existence of spatial structure in dental shape variation, as the D2 Mahalanobis distance between samples increases with increasing geographical distance between them. In addition, the correlation test results show a trend toward reduction of the internal variation of samples with increasing latitude. The detected pattern of dental variation agrees with the one expected as an outcome of founder serial effects related to an expansion of range during the initial occupation of southern South America. Am J Phys Anthropol, 2010. © 2009 Wiley-Liss, Inc. [source] Comparison of bonding efficacy of an all-in-one adhesive with a self-etching primer systemEUROPEAN JOURNAL OF ORAL SCIENCES, Issue 3 2004Tomoko Abo The aim of this study was to compare the bonding efficacy of an all-in-one adhesive with that of a self-etching primer system by measuring microleakage after thermocycling and the microtensile bond strength (,TBS) to enamel and dentin. Circular class V cavities along cement,enamel junctions were prepared in 20 extracted human premolars. Each 10 teeth were bonded with either AD Bond (AD) or Clearfil SE Bond (SE), and filled with a resin composite (Charisma). After thermocycling and staining with 0.5% basic fuchsin, the microleakage at the coronal and apical walls was evaluated using longitudinal sections. In addition 20 premolars were used to measure ,TBS at 24 h after bonding for these adhesives to enamel and dentin that corresponded to the coronal and apical walls of the class V cavities. AD showed more microleakage than SE in the coronal walls, but there was less microleakage in the apical walls and no difference in apical leakage between the two adhesives. ,TBS (SD) in MPa to enamel and dentin were 25.2 (7.3) and 68.3 (9.4) for AD, and 35.8 (7.4) and 76.4 (7.8) for SE, respectively. AD gave a lower ,TBS to enamel than did SE. The results suggested that the poor adaptation at the coronal wall in AD might be caused by the lower bond strength to enamel. [source] Dental wear, wear rate, and dental disease in the African apesAMERICAN JOURNAL OF PRIMATOLOGY, Issue 6 2010Alison A. Elgart Abstract The African apes possess thinner enamel than do other hominoids, and a certain amount of dentin exposure may be advantageous in the processing of tough diets eaten by Gorilla. Dental wear (attrition plus abrasion) that erodes the enamel exposes the underlying dentin and creates additional cutting edges at the dentin-enamel junction. Hypothetically, efficiency of food processing increases with junction formation until an optimal amount is reached, but excessive wear hinders efficient food processing and may lead to sickness, reduced fecundity, and death. Occlusal surfaces of molars and incisors in three populations each of Gorilla and Pan were videotaped and digitized. The quantity of incisal and molar occlusal dental wear and the lengths of dentin,enamel junctions were measured in 220 adult and 31 juvenile gorilla and chimpanzee skulls. Rates of dental wear were calculated in juveniles by scoring the degree of wear between adjacent molars M1 and M2. Differences were compared by principal (major) axis analysis. ANOVAs compared means of wear amounts. Pearson correlation coefficients were calculated to compare the relationship between molar wear and incidence of dental disease. Results indicate that quantities of wear are significantly greater in permanent incisors and molars and juvenile molars of gorillas compared to chimpanzees. The lengths of dentin,enamel junctions were predominantly suboptimal. Western lowland gorillas have the highest quantities of wear and the most molars with suboptimal wear. The highest rates of wear are seen in Pan paniscus and Pan t. troglodytes, and the lowest rates are found in P.t. schweinfurthii and G. g. graueri. Among gorillas, G. b. beringei have the highest rates but low amounts of wear. Coefficients between wear and dental disease were low, but significant when all teeth were combined. Gorilla teeth are durable, and wear does not lead to mechanical senescence in this sample. Am. J. Primatol. 72:481,491, 2010. © 2010 Wiley-Liss, Inc. [source] | |||||||||||||