Improved understanding of the factors influencing occlusal development from the primary, through mixed, to the permanent dentition should help inform preventive and treatment approaches to dental malocclusion. The aim of this study is to describe the nature and extent of occlusal variation over time in Australian twins and to quantify the contributions of genetic, epigenetic and environmental influences to observed variation.
Dental records of Australian twins were collected during 1990s and early part of the 21st century, including serial models of the primary (mean age 6.2 yrs; min 4.1, max 9.0), mixed (9.7; 8.2, 12.0) and permanent (14.4; 10.0, 17.0) dentitions. Altogether 111 twin pairs, including monozygotic (n=50) and dizygotic (n=61) pairs, met the inclusion criteria with a range of skeletal and dental relationships able to be recorded. A sliding digital calliper was used to obtain direct measurements from the dental models, with the teeth occluded in maximum intercuspation. We measured overjet, overbite, midline deviation and diastema, molar and canine relationship, cross/scissors-bite, rotation, displacement and spacing in primary, mixed and permanent dentition. Ranges of some measured variables are shown in the Table. Preliminary power studies have confirmed that the sample sizes are adequate for the intended analyses. Continuous parameters will provide more accurate data for this longitudinal study with an emphasis on describing the full extent of occlusal variation. Improved understanding of factors will help to predict and guide occlusal development and be valuable for clinical purposes.
Supported by the NHMRC of Australia and the Finnish Dental Association.