Genetic aspects of variation in tooth width based on asymmetry and twin studies

Analysis of crown size and morphology, and gingival shape in the maxillary anterior dentition in Korean young adults

PURPOSE

The aim of this investigation was to analyze the dimensions of clinical crowns and to classify the crown and the gingival type in the anterior teeth in Korean young adults.

MATERIALS AND METHODS

Casts were obtained from 50 subjects ranging in age from 24 to 32. Measurements of length and width were made on the casts using a pair of digital calipers on the entire dentition. Crown thickness and papilla height were also measured and MDW/CL (mesiodistal width to clinical length) and CW/CL (cervical width to clinical length) ratios of the maxillary anterior teeth were calculated. The K-clustering method was used for CW/CL to classify the anterior tooth shape into three groups (tapered, ovoid, and square), and one-way analysis of variance and Duncan's post-hoc comparison were used to evaluate statistical significance between the groups. Pearson's correlation analysis was performed between tooth shape and papillary height (PH) to demonstrate the correlation between tooth shape and gingival morphological characteristics.

RESULTS

The average length of the maxillary central incisors was 9.89 mm; the mesio-distal width was 8.54 mm; and the ratio of width/length was 0.86 in Korean young adults. The average bucco-palatal thickness of the central incisor was 3.14 mm at the incisal 1/3 aspect. Ovoid type was the most common tooth shape (48%), followed by square type (29%) and taper type (23%) in the central incisors of Korean young adults. Tooth shape and gingival type were correlated with each other.

CONCLUSION

New reference data were established for tooth size in Korean young adults and the data show several patterns of tooth shape and gingival type. Clinicians should diagnose and treat based on these characteristics for better results in the Korean population.

Variation in size and form between left and right maxillary central incisor teeth

The evaluation of the collated results demonstrated that 86% to 90% of the subjects examined did not have identical dimensions or form of the left and right maxillary central incisors. In over 60% of these subjects the differences were quite substantial.

Odontometric microdifferentiation of transplanted Mexican indian populations: Cuanalan and Saltillo

This study documents odontometric variation in four populations of related genetic background. It is found that the transplanted populations of Cuanalan and Saltillo have undergone significant microdifferentiation in tooth size relative to the two home valley populations. The extent and direction of this microdifferentiation is seen as reflecting differential amounts of admixture from African and European sources in demographic subunits of the two transplanted populations. The dental variables found to discriminate significantly between populations are the same variables predicted to be evolutionarily labile by Butler's Field Theory. Principal component analysis confirms the presence of morphological fields in these data and supports the position that each class has a stable tooth, with stability decreasing with increasing distance from the key tooth. The importance of hybridization in determining which variables significantly discriminate between populations is confounded by the effects of development of the dentition in morphogenetic fields. These data suggest that odontometric data provide an adequate, if somewhat conservative, base from which to evaluate microdifferentiation of human populations.