Bitemarks: distortion and covariation of the maxillary and mandibular dentition as impressed in human skin.

In bitemark analysis the extent of distortion of both maxillary and mandibular arches and how one affects the other has not been studied. A single dentition was used to create 49 bites on unembalmed cadavers. Landmarks were placed on digital images of the bitemarks and scanned images of the biting dentition. A sample of 297 randomly acquired dental models was used for comparison purposes. Geometric morphometric techniques were utilized to statistically describe size and shape change, as well as the correlation between the two arches. Results indicate that the predominant distortion seen was in arch width, at 7-28 times as large as measurement error in the biting dentition and roughly 50% of the variation seen in the random population of dentitions. The correlation of arch width distortion between arches was very low (∼0.03). However, the principal patterns of all shape variation did co-vary in the bitemarks produced by the maxillary and mandibular dentition, an effect indicating independence of size and shape distortion. In conclusion, bitemark analysis should be approached with caution when the principal difference between suspects is arch width.