A pilot investigation of enamel reduction procedures.
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OBJECTIVE: To test and describe the use of various combinations of mechanical and chemical techniques for enamel reduction to obtain a smooth surface. METHODS: Bovine teeth (2 surfaces on each of 32 teeth) were used. The teeth were mounted in blocks of dental plaster, which were then mounted in a vise. The mesiodistal enamel contact areas were reduced by various combinations of mechanical and chemical aids. The mesiodistal width of each tooth was measured with a digital caliper after initial reduction of the enamel surface and again after polishing. The teeth were subsequently prepared and mounted for scanning electron microscopy. RESULTS: All combinations yielded statistically significant enamel reduction (p < 0.05). The use of acid stripping in conjunction with mechanical procedures produced especially smooth enamel surfaces. CONCLUSIONS: Steps must be taken to ensure that a smooth enamel surface remains after enamel reduction and polishing. It is recommended that conventional enamel etchants be added to the polishing procedure. Enamel reduction can increase available space, but the quantity of enamel that can be removed without adverse consequences should be carefully evaluated. (+info)
Evaluation of an articulated measuring apparatus for use in the oral cavity.
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The aim of this study was to evaluate the trial Teaching Robot for the development of a contact-type measuring apparatus for using directly in the oral cavity. A standard model was used to mimic the dentition by placing an arrangement of three bearing balls. The diameters of the balls were measured. A practical dentition model was used. The coordinates were measured on the top of the buccal cusp of the right and left first premolars and the distal contact points of the right and left first molars and the mesial contact point of the right incisor. The arch width and length were calculated. The diameters of the bearing balls and the widths and lengths of the dental arches were not significantly different from the results of the XYZAX G-800D. Therefore, we suggest that the trial Teaching Robot has superior efficiency for measurements in oral cavity. (+info)
Genetic basis of adaptive shape differences in the cichlid head.
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East African cichlids exhibit an extraordinary level of morphological diversity. Key to their success has been a dramatic radiation in trophic biology, which has occurred rapidly and repeatedly in different lakes. In this report we take the first step in understanding the genetic basis of differences in cichlid oral jaw design. We estimate the effective number of genetic factors that control differences in the cichlid head through a comprehensive morphological assessment of two Lake Malawi cichlid species and their F(1) and F(2) hybrid progeny. We estimate that between one and 11 factors underlie shape difference of individual bony elements. We show that many of the skeletal differences in the head and oral jaw apparatus are inherited together, suggesting a degree of pleiotropy in the genetic architecture of this character complex. Moreover, we find that cosegregation of shape differences in different elements corresponds to developmental, rather than functional, units. (+info)
Three dimensional shape measurement of teeth (2). CAD to produce crown considering occlusion.
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Use of a CAD program to design the shape of a crown, restoration of 6 molar was studied. Stone models of 5 to 7 molars with 6 prepared die for crown and a complete 6 crown which was applied for restoration were measured. The 6 crown data were adapted on the 6 die, and adjusted with 5 and 7 proximal teeth. The coordinates of the data of 6 were then transferred to that of the 6 die. The ends of the adapted crown data were linked with the margin of 6 die. Further the occlusal condition with antagonistic tooth was adjusted by applying the FGP (functionally generated path) technique. FGP was recorded on bite wax and measured. Comparing FGP record and adapted crown, modulation of the occlusal surface was accomplished. (+info)
Orthodontic treatment outcome: the relationship between anterior dental relations and anterior inter-arch tooth size discrepancy.
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OBJECTIVE: This study investigated the pre- (T1) and post-treatment (T2) relationship between anterior (canine to canine inclusive) inter-arch tooth size ratio and various dental and skeletal variables. DESIGN: Retrospective longitudinal clinical study. SETTING: Swedish Health Board Clinic 2000. SUBJECTS: Random selection of T1 and T2 orthodontic records of 137 Swedish patients (56 male and 81 female). The sample included non-extraction (77), and four premolar extraction (60) cases across a range of dental and skeletal malrelationships. MAIN OUTCOME MEASURES: Dental cast and lateral cephalogram measurements were recorded. Exploratory modelling investigated whether a significant relationship existed between the anterior inter-arch tooth size ratio and these measurements. RESULTS: Data was normally distributed with no statistically significant differences between males and females (P = 0.88) and extraction and non-extraction (P = 0.52) treatment modalities with respect to the anterior ratio. T1 bivariate regression analysis failed to show a relationship (p < 0.05) between variables. T2 bivariate analysis showed a statistically significant relation between three variables and anterior tooth size ratio. Multiple regression analysis led to a final model where maxillary inter-canine width (P = 0.002) and upper arch crowding (0.001) were statistically significantly related to the anterior inter-arch ratio. The coefficient of determination was however uniformly low (R(2) < 0.2) for all variables. CONCLUSION: The anterior inter-arch tooth size ratio was not associated with any common pre- or post-treatment variables in the population studied, therefore measurement of an anterior tooth size ratio pre-treatment was not clinically beneficial for determining anterior dental relations post-treatment. (+info)
Tooth size in dentitions with buccal canine ectopia.
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Much interest has been expressed in recent years regarding various features common to dentitions with palatally displaced canines (PDC), particularly in relation to delayed dental development and reduced tooth size. The aims of the present study were to determine whether dentitions with buccally displaced canines (BDC) have features in common, which may be specific for the condition, when compared with PDC dentitions and those with normally erupting canines. Mesiodistal and buccolingual tooth dimensions were determined for 41 subjects with BDC (21 females and 20 males) aged between 11 and 15 years, who formed the experimental sample. The PDC sample was made up of 58 individuals (37 females and 21 males) and the control group comprised 40 age-matched and consecutively treated subjects (20 males and 20 females), exhibiting normally erupted and undisplaced maxillary canines. The results revealed marked sexual dimorphism. Larger-than-average teeth were present in BDC females, whereas the teeth in BDC males were normally sized. Unilaterally affected females had smaller teeth than bilaterally affected females. Tooth size in BDC was consistently larger than in PDC subjects, although the reason was different between the sexes. In females the PDC teeth were normally sized versus large BDC teeth, whereas in the males, the PDC teeth were small and the BDC teeth normal. It is concluded that combining male and female subjects into an overall BDC group obscures important differences that exist between the two sexes. (+info)
Endodontic treatment of bilaterally occurring 4-rooted maxillary second molars: case report.
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The presence of 4-rooted maxillary second molars has been described in only a limited number of case reports. Studies of anatomical features have demonstrated substantial variation in the number of roots and root canals in different teeth. The maxillary second molar usually has 1, 2, or 3 roots and generally 3 or 4 root canals. This case describes the presence of 4 roots occurring bilaterally in maxillary second molars in one patient. (+info)
Evidence for reproductive isolation between cave bear populations.
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The European cave bear (Ursus spelaeus), which became extinct around 15,000 years ago, had several morphologically different forms. Most conspicuous of these were small Alpine cave bears found at elevations of 1,600 to 2,800 m. Whereas some paleontologists have considered these bears a distinct form, or even a distinct species, others have disputed this. By a combination of morphological and genetic methods, we have analyzed a population of small cave bears from Ramesch Cave (2,000 m altitude) and one of larger cave bears from Gamssulzen Cave (1,300 m), situated approximately 10 km apart in the Austrian Alps (Figure 1A). We find no evidence of mitochondrial gene flow between these caves during the 15,000 years when they were both occupied by cave bears, although mitochondrial DNA sequences identical to those from Gamssulzen Cave could be recovered from a site located about 200 km to the south in Croatia. We also find no evidence that the morphology of the bears in the two caves changed to become more similar over time. We suggest that the two cave bear forms may have represented two reproductively isolated subspecies or species. (+info)