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The dimensional factors of the cervical undercut of the human teeth were measured. The facial and lingual undercuts showed considerable deviations in depth, width, and inclination to the crown axis and the food stream. The proximal undercuts showed a uniform depth of 1 +/- 0.3 mm with some deviations in width and inclination.
With the use of an infrared thermographic camera; temperature patterns over the crowns of teeth were recorded. The temperature of upper incisor teeth decreased from gingival margin to incisal edge by approximately 2.5 degrees C. Vital and nonvital teeth were the same temperature at rest, but after cooling with cold air, nonvital teeth were slower to rewarm than vital teeth. The infrared thermographic camera could provide a method of testing tooth vitality based on blood supply rather than nerve supply.
A case of spontaneous repair of the fractured crown of an upper central incisor is reported, a brief account of the treatment is given, and the possible mechanism of repair is discussed.
In rodents, the position of a fetus in utero is associated with the expression of sexually dimorphic traits. This phenomenon has been explained by prenatal diffusion of sex hormones among litter mates. To test for such effects in humans, female-male twin pairs provide a natural experiment. The size of dental crowns is a sexually dimorphic trait which can be measured with a high degree of reliability. Thus, two crown diameters of 28 permanent teeth were recorded for 56 opposite-sexed (OS) and 242 same-sexed (SS) twin pairs, and 150 singletons. Comparisons of OS twins with SS twins and singletons within each sex reveal that OS females have consistently larger teeth (on average) than other females, while there is no consistent difference between OS and SS twin males. It is proposed that diffusion of sex hormones from male to female co-twins in utero may account for the increased tooth size in OS females. This study is one of the first to report such an effect on a morphological variable in humans. The finding that the maxillary canine, one of the most sexually dimorphic teeth, exhibits the least effect in OS female twins, suggests that prenatal sex hormone levels may have less impact on sexual dimorphism in the maxillary canines than in other permanent teeth. Am. J. Hum. Biol. 11:577-586, 1999. Copyright 1999 Wiley-Liss, Inc.
Juveniles and adults from a prehistoric Amerindian skeletal series from Tennessee are compared for differences in the means and variances of the buccolingual dimensions of their permanent teeth. While there are no significant differences in variance, it is found that juveniles exhibit significantly smaller mandibular canines, first premolars, and first molars. The results are similar to those of a previous examination of an Amerindian skeletal collection from South Dakota. There is evidence to suggest that teeth may fail to develop to their maximum genetic size potential when there is interference from exogenous chronic stressors such as malnutrition or disease. Archaeological and biological evidence demonstrates that both the Tennessee and South Dakota series represent groups that suffered considerably from environmental stressors. It is suggested that those persons who suffered most were more likely to die prematurely, thus explaining why juvenile skeletons tend to have smaller teeth. The conclusion is that the examination of age variation in crown size can be a useful supplement to other osteological indicators of stress in skeletal collections. The factor of sex ratio and the implications of the results for other kinds of dental metric studies are discussed.
In this paper, the sexual differences between mesio-distal and bucco-lingual diameters of deciduous and permanent teeth of an Early Bronze Age population from Franzhausen are presented. Data from a total of 172 (85 male and 87 female) subadult individuals was collected. The presumptive sex determination needed for this investigation could be achieved because of specific burial rites that characterize the Unterwölbling culture south of the Danube. The averages of both the deciduous and permanent teeth show that female individuals possess altogether teeth of smaller dimensions. The differences are, for a few permanent teeth, statistically highly significant. Using these to calculate discriminant analyses based on differing variable sets, a correct sex assignment was achieved in 81% to 75% of all cases. For the purposes of sexual diagnosis, a function combining only three measurements (MD and BL diameters of upper canine and BL diameter of the first upper molar) was 80% successful.
Enamel thickness of the maxillary permanent central incisors and canines in seven Finnish 47,XXX females, their first-degree male and female relatives, and control males and females from the general population were determined from radiographs. The results showed that enamel in teeth of 47,XXX females was clearly thicker than that of normal controls. On the other hand, the thickness of "dentin" (distance between mesial and distal dentinoenamel junctions) in 47,XXX females' teeth was about the same as that in normal control females, but clearly reduced as compared with that in control males. It is therefore obvious that in the triple-X chromosome complement the extra X chromosome is active in amelogenesis, whereas it has practically no influence on the growth of dentin. The calculations based on present and previous results in 45,X females and 47,XYY males indicate that the X chromosome increases metric enamel growth somewhat more effectively than the Y chromosome. Possibly, halfway states exist between active and repressed enamel genes on the X chromosome. The Y chromosome seems to promote dental growth in a holistic fashion.
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To understand why the crown lengthening may be desirable, a review of periodontal anatomy is in order. The odontologists know, but often underestimate importance of periodontal tissues health to restoration of defected teeth or dental arches. In order to avoid pathological changes, to predict treatment results more precisely, it is necessary to keep gingival biological width unaltered during teeth restoration. If there are less than 2 mm from restoration's margin to marginal bone clinical crown lengthening possibility should be considered in dental treatment plan. The choice depends on relationship of crown-root-alveolar bone and esthetical expectations. In order to keep margins of restoration supragingivally the distance from marginal bone to margins of restoration should not be less than 3 mm. Ideally the margins of restoration should be supragingivally or in the same level as marginal gingiva. When the margins of restoration are prepared subgingivally, the distance from marginal gingiva to margins of restoration should not be more than 0.7 mm. To continue dental treatment in operated area is recommended not earlier than in 4 weeks, and making restorations in esthetical area--not earlier than in 6 weeks.
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