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Objective: This study aimed to provide insight into the relative contributions of genetic and environmental factors to palatal morphology variation in a cohort of Australian twins., Methods: Healthy Australian twins, aged 12-15 years (45 monozygotic, 46 same sex dizygotic, and 32 opposite-sex dizygotic) were included in the study groups. A scanner was used to obtain three-dimensional data of the maxillary arch. Palatal depth was defined by a line to the deepest point measured from the reference plane at the mid-point of the inter-pre-molar or inter-molar line. This line was then divided into 10 equal sections in order to created 10 different depths for each palatal width. Each palatal width was divided into anterior and posterior areas. Univariate genetic analysis, using the OpenMx structural equation modelling package in R, was carried out on the quantitative data using the normal assumptions of a twin model., Results: Heritability estimates for anterior palatal width ranged from 0.75 to 0.80, and from 0.78 to 0.86 for posterior palatal width. Estimates for anterior and posterior palatal depth were 0.72 and 0.86, respectively., Conclusions: Palatal morphology tends to have a moderate to relatively high genetic contribution overall. Palate height has a higher genetic contribution posteriorly than anteriorly. The width of the deep palate is under marginally less stringent genetic regulation than the width of the shallow palate., Competing Interests: Declaration of Competing Interest The recruitment phase of this study was supported financially by the National Health and Medical Research Council of Australia. The remainder of the research did not receive any specific grant funding from agencies in the public, commercial, or not-for-profit sectors., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

The aim of this study was to quantify the relative contributions of genetic and environmental factors to variations in dental arch breadth, length and palatal height in a sample of Australian twins, and to estimate heritabilities using modern model-fitting methods. Dental casts of 20 male and 24 female monozygous (MZ) twin pairs, 17 male and 8 female dizygous (DZ) twin pairs, and 9 opposite-sexed DZ twin pairs were selected from the collection of records of twins housed at the Adelaide Dental School. The mean ages of subjects were 15.8 +/- 3.5 years (MZ) and 17.0 +/- 4.7 years (DZ). Dental casts were scanned using a contact-type 3D scanner, PICZA interfaced to a personal computer running 3D-Rugle3 software. Data were subjected to univariate genetic analysis with the structural equation modelling package, Mx, using the normal assumptions of the twin model. A model incorporating additive genetic (A) and unique environmental (E) variation was found to be the most parsimonious for dental arch breadth and length, and palatal height. Estimates of heritability for dental arch breadth ranged from 0.49 to 0.92, those for arch length from 0.86 to 0.94, and those for palatal height were 0.80 and 0.81, respectively. These results indicate a high genetic contribution to the variation in dental arch dimensions in mainly teenage twins.

The purpose of this study was to provide information about arch shape variations among South Pacific populations. The application of Fourier transforms, Y(phi i) = ao/2 + sigma (aicos phi i + bisin phi i) was used to separate two components of variation; size and shape. Dental arch size can be described by one coefficient (ao), while the shape can be summarized by the first three harmonics (amp1-3) in the Fourier series. The materials used in this study were dental casts of South Pacific populations (Fiji, Western Samoa and Kiribati), Australian Aboriginals and Japanese. Fijians, Western Samoans and Kiribati people have larger upper and lower dental arches than that of Japanese. These populations were separated by the arch size and first Fourier amplitudes which showed the arch depth/width ratio. The Fijian upper and lower dental arches were significantly larger than those found in other populations and was characterized by a wide posterior arch breadth. The Western Samoan and Kiribati arch shape was more similar to the Japanese arch shape than the Fijian. Distribution patterns of arch shape characteristics in these populations showed the same tendencies in the upper and lower arches.

A metric study of 71 Japanese and 106 Australian aboriginal precontemporary crania was undertaken using direct measurements and cephalograms. Compared with Australian aboriginals, the Japanese are characterized by smaller cranial length, cranial base length, nasal floor length, palatal length, mandibular dimensions (except symphysis height), facial depth, posterior face height, and facial profile angle and larger cranial breadth and height, maxillary breadth, palatal breadth, anterior face height, and occlusal and mandibular plane angles. These differences confirm the previously described brachycephalic tendency in aboriginals and the dolichocephalic form in the Japanese. The differences are also consistent with the expected functional differences between the Australian aboriginal hunter-gatherer group masticating more resistant food with larger, more anteriorly located, more powerful masseter muscles and the Japanese group masticating less resistant food with correspondingly less robust masticatory musculature. The results highlight the differences in craniofacial morphology between groups with different genetic backgrounds subjected to significantly different environmental influences.