Patterning of the human dentition: implications for forensic odontology.

Forensic identification may be required for a number of reasons. The identification process relies on the comparison of information gathered from known records with information from the unknown. Different scientific methods may be employed, but a primary identifier is a comparison of data concerning the status of the teeth. Conclusions regarding identity range from possible to positive identification. The presence of dental treatments or pathological conditions usually adds to the weighting of forensic identification. The availability of dental radiographs also strengthens the opinion where ante-mortem and post-mortem image comparisons can be made. This combination of dental treatments provides a reasonable choice for statistical modelling; however, such forms of variability are on the decline in populations with better oral health. It is well established that teeth are derived and affected by a complex interplay of genetic, epigenetic and environmental factors, giving rise to significant natural variation in the arrangement, size, and shape of teeth that is generally stable through time. Modelling such variation should provide a useful mechanism for identification in cases where dental treatments are not present in the dentition. Arguments on the issue of individualisation have highlighted an obvious obstacle when tackling this issue as it is impossible to study each and every individual in the world. The aim of the current project is to display the value of focussing on these normal variations rather than the ‘problems’. The focus is on the measurement and comparison of dental crown size and dental arch size and shape within and between six human populations. This information provides the foundation for future development of a more robust probabilistic model focussing on the normal morphological status of dentition. Observations were made in six different ethnic groups including Australian Aboriginals, Europeans, and four major ethnic groups in Malaysia; Malays, Indians, Chinese and a Malaysian Indigenous group (Orang Asli). Measurements of these variations using both 2D and 3D imaging systems displayed reliable and repeatable methods to measure patterning of the human dentition using the normal morphology of teeth and dental arches. By using standardised eigenvalues derived from metric measurements, a probabilistic model was postulated to assess random match probabilities. The findings from this current research add to our understanding of the variability of the human dentition and should improve the acceptance of using dental morphology as a means of identification. The results have shown that despite absence of dental treatments, the nature and extent of normal morphological variation in the human dentition can be quantified reliably and then applied in forensic and anthropological situations for identification purposes.Thesis (Ph.D.) -- University of Adelaide, School of Dentistry, 201