Three-Dimensional Comparative Analysis of Bitemarks

Tri-dimensional pattern analysis of foodstuff bitemarks - A pilot study of tomographic database

The analysis of bitemarks has been mostly done through analogical methods. The advent of current technologies brings new and more reliable tools for analyzing evidence. Bitemarks can now be turned into more consistent evidence by using a digital tridimensional (3D) analysis. The aim of this study is to propose a reliable, accurate and monitorized approach of 3D bitemark analysis. 12 cranium Cone Beam Computed Tomographic (CBCT) files were randomly selected from a clinical database (Coimbra Hospital and University Center/Faculty of Medicine of the University of Coimbra). The individuals were recalled to bite an apple (golden delicious 65/80) immediately subjected to a CBCT scan. The 3D rendering of every bitemark was compared with the 3D upper dental arches obtained from the CBCT cranium scans of the simulated suspects. The research team was composed by 5 elements. The matching process consists of corresponding landmark points, in both the bitemark and the suspects' dentition (upper dental arch). 144 comparisons were obtained. The Kappa statistics analysis was performed. Cohen's Kappa values were obtained between 0,690 and 0,910. Fleiss Kappa obtained a value of 0,767. The Friedman's test was performed and the normality assumption was not verified (p>0,05). A non-destructive protocol of bitemark study by 3D analysis of tomographic volumes was presented. The statistic analysis supports its accuracy and reliability. This experimental study opens doors to a future where bitemark analysis could be done through software that searches for matching dentitions in a CBCT database.

Procedure for the systematic orientation of digitised cranial models. Design and validation

Comparison of bony pieces requires that they are oriented systematically to ensure that homologous regions are compared. Few orientation methods are highly accurate; this is particularly true for methods applied to three-dimensional models obtained by surface scanning, a technique whose special features make it a powerful tool in forensic contexts. The aim of this study was to develop and evaluate a systematic, assisted orientation method for aligning three-dimensional cranial models relative to the Frankfurt Plane, which would be produce accurate orientations independent of operator and anthropological expertise. The study sample comprised four crania of known age and sex. All the crania were scanned and reconstructed using an Eva Artec™ portable 3D surface scanner and subsequently, the position of certain characteristic landmarks were determined by three different operators using the Rhinoceros 3D surface modelling software. Intra-observer analysis showed a tendency for orientation to be more accurate when using the assisted method than when using conventional manual orientation. Inter-observer analysis showed that experienced evaluators achieve results at least as accurate if not more accurate using the assisted method than those obtained using manual orientation; while inexperienced evaluators achieved more accurate orientation using the assisted method. The method tested is a an innovative system capable of providing very precise, systematic and automatised spatial orientations of virtual cranial models relative to standardised anatomical planes independent of the operator and operator experience.

A simple safe, reliable and reproducible mechanism for producing experimental bite marks

With improving technology it should be possible to develop an objective, reliable and valid method that can be undertaken by most forensic Odontologists without recourse to expensive or bulky equipment. One of the main factors that affect the physical appearance of bitemark is the amount of force applied during biting. There is little evidence relating the appearance of a bite mark to the amount of force applied and how that force relates to the biters maximal biteforce. This paper describes simple apparatus that can be used to inflict experimental bites on living subjects reproducibly and with minimal risk. The aims of this study are to report on the development of a mechanical apparatus that produces experimental bitemarks on living human subjects with a known force in a safe, reliable and reproducible manner and to relate the force applied during production of the experimental bitemark to the maximum bite force of the biter. Maximum bite force of one of the authors was determined as 324 N. Experimental bitemarks were inflicted on living subjects with known weights. Weights of up to 10 kg were well tolerated by the subjects. The relation between forces used to inflict bites and the maximum bite force of the author is reported, with 10 kg being approximately one third of the maximum bite force. The apparatus was well tolerated and the results were reliable and reproducible. The results from this study could help in determining the severity of bitemarks. This apparatus could help researchers in developing objective based bitemark analysis techniques.

Is current bite mark analysis a misnomer?

Four human-to-human bite mark cases in which forensic odontological opinion was found to be in error, or at best deeply divided between experts, are described. These are used to illustrate that there is a growing awareness on the part of the legal profession that bite mark opinions by experts may often be little more than that and that these opinions often cannot be substantiated given the paucity of rigorous scientific evaluation, and will therefore be increasingly challenged. This may not best serve justice and so it is argued that forensic odontology needs to bring more scientific rigour to the evaluation of bite marks. This may threaten to disenfranchise some of the current practitioners and there may be some resistance to change. Forensic odontology is not the only identification science facing such problems, but nevertheless a paradigm shift is predicted in the way bite mark evidence will have to be gathered and evaluated in the future. Some new scientific approaches are described that strive to unravel some of the most basic problems confronting our profession when we attempt to make morphometric comparisons between injuries and the dentition of the biter. A need to capture the actions and consequences of biting in 3D dimensions and simultaneously in real-time is proposed as a path of investigation highly likely to bring some clarity to a confused situation. There is also an urgent need for the ongoing controversy between some of our eminent peers relating to the assumed uniqueness, or otherwise, of the human anterior dentition to be resolved.