Similarity and match rates of the human dentition in three dimensions: relevance to bitemark analysis

Evaluation of Bitemark Analysis's Potential Application in Forensic Identification: A Systematic Review

Bitemark analysis involves the examination of both patterned injuries and contextual circumstances, combining morphological and positional data. Considering the uniqueness of human dentition, bitemarks caused by teeth on skin or impressions on flexible surfaces could assist in human identification.

AIMS

to investigate the available literature systematically and evaluate the scientific evidence published over the past decade concerning the potential application of bitemark analysis in forensic identification.

METHODS

Two researchers meticulously searched electronic databases from January 2012 to December 2023, including Scopus, PubMed, Web of Science, and the Cochrane Library. Adhering to the PRISMA statement guidelines, this review employed appropriate medical subject headings (MeSHs) and free-text synonyms. Strict inclusion and exclusion criteria were applied during article retrieval.

RESULTS

The findings yielded controversial outcomes. Approximately two-thirds of the articles concluded that bitemark analysis is useful in forensic identification, while the remaining articles did not report statistically significant outcomes and cautioned against relying solely on bitemark analysis for identification.

CONCLUSIONS

The authors assert that bitemark analysis can be a reliable and complementary method for forensic identification, contingent upon the establishment and adoption of a universally accepted global protocol for data collection, processing, and interpretation. Undoubtedly, recent years have witnessed a notable increase in research focused on bitemark identification, driven by the goal of achieving quantitative, objective, reproducible, and accurate results.

Virtual reality and integrated crime scene scanning for immersive and heterogeneous crime scene reconstruction

Crime scene reconstruction plays a significant role in crime solving by helping to determine the course of events. Non-invasive, high-resolution measurement and increased insight are always the goal of forensic crime scene documentation. However, entire crime scenes cannot be effectively reconstructed with traditional methods. In this study, we present a portable system that consists of a laser scanner, two hand-held structured light scanners and a low-cost virtual reality (VR) headset with a mobile power supply to conduct multi-angle and omnidirectional three-dimensional spatial data collection of crime scenes. To demonstrate practical use, a real case has been analysed to verify the feasibility and effectiveness of the system. The system accurately obtains information on decedent injuries, possible injury-inflicting tools and on-site traces. Various types of evidence from the crime scene can be jointly studied by three-dimensional visualization to develop a cohesive story. The data are presented via immersive VR rather than displayed on computer screens. The relationship between evidence chains enables us to achieve a complete crime scene reconstruction, using the specialized knowledge of experts and computer-aided forensic tools to analyse the causes of damage and identify suspects. The use of three- dimensional imaging techniques allows a more insightful survey and several useful analyses, such as accurate measurement, relative blood source location determination and injury-inflicting tool comparison.

An Automated Two-dimensional Pairwise form Registration Method for Pair-matching of Fragmented Skeletal Remains

This study introduces an automated pairwise method for osteological pair-matching of fragmented skeletal remains using two-dimensional fragmented outlines extracted from photographs. The form data are used in pairwise iterative closest point registrations with rigid transformations. A modified version of the average Hausdorff distance is calculated to remove any coordinate correspondences with outline fracture margins, which allow the distance analysis of fragmented outlines. A dilation modification to the Hausdorff distance is proposed creating a greater separation between true- and false-pairs. The sample consists of 122 calcanei (61 pairs) from the UI-Stanford collection. Performance statistics are provided for simulated fragmented and complete assemblages. Results indicate up to 98% accuracy for fragmented and complete assemblages. The dilated Hausdorff distance performed similarly across assemblages, but showed a slight decrease in performance for the complete assemblage. This approach provides a useful short listing tool to reduce the number of visual comparisons required in large commingled assemblages.

Three-dimensional analysis of the uniqueness of the anterior dentition in orthodontically treated patients and twins

Dental uniqueness can be proven if no perfect match in pair-wise morphological comparisons of human dentitions is detected. Establishing these comparisons in a worldwide random population is practically unfeasible due to the need for a large and representative sample size. Sample stratification is an option to reduce sample size. The present study investigated the uniqueness of the human dentition in randomly selected subjects (Group 1), orthodontically treated patients (Group 2), twins (Group 3), and orthodontically treated twins (Group 4) in comparison with a threshold control sample of identical dentitions (Group 5). The samples consisted of digital cast files (DCF) obtained through extraoral 3D scanning. A total of 2.013 pair-wise morphological comparisons were performed (Group 1 n=110, Group 2 n=1.711, Group 3 n=172, Group 4 n=10, Group 5 n=10) with Geomagic Studio^® (3D Systems^®, Rock Hill, SC, USA) software package. Comparisons within groups were performed quantifying the morphological differences between DCF in Euclidean distances. Comparisons between groups were established applying One-way ANOVA. To ensure fair comparisons a post-hoc Power Analysis was performed. ROC analysis was applied to distinguish unique from non-unique dentures. Identical DCF were not detected within the experimental groups (from 1 to 4). The most similar DCF had Euclidian distance of 5.19mm in Group 1, 2.06mm in Group 2, 2.03mm in Group 3, and 1.88mm in Group 4. Groups 2 and 3 were statistically different from Group 5 (p<0.05). Statistically significant difference between Group 4 and 5 revealed to be possible including more pair-wise comparisons in both groups. The ROC analysis revealed sensitivity rate of 80% and specificity between 66.7% and 81.6%. Evidence to sustain the uniqueness of the human dentition in random and stratified populations was observed in the present study. Further studies testing the influence of the quantity of tooth material on morphological difference between dentitions and its impact on uniqueness remain necessary.

Uniqueness of the anterior dentition three-dimensionally assessed for forensic bitemark analysis

The uniqueness of the human dentition (UHD) is an important concept in the comparative process in bitemark analysis. During this analysis, the incisal edges of the suspects' teeth are matched with the bitemarks collected from the victim's body or crime scenes. Despite playing an essential part to exclude suspects, the UHD contained in the involved incisal tooth edges remains an assumption on bitemark level. The present study was aimed, first, to investigate three-dimensionally (3D) the UHD within different quantities of dental material from the incisal edges; second, to test these outcomes in a bidimensional (2D) simulation. Four-hundred forty-five dental casts were collected to compose 4 study groups: I - randomly-selected subjects, II - orthodontically treated subjects, III - twins and IV - orthodontically treated twins. Additionally, 20 dental casts were included to create threshold groups on subjects from whom the dental impressions were taken at 2 different moments (Group V). All the dental casts were digitalized with an automated motion device (XCAD 3D^® (XCADCAM Technology^®, São Paulo, SP, Brazil). The digital cast files (DCF) were integrated in Geomagic Studio^® (3D Systems^®, Rock Hill, SC, USA) software package (GS) for cropping, automated superimposition and pair-wise comparisons. All the DCF were cropped remaining 3 mm (part 1), 2 mm (part 2) and 1 mm (part 3) from the incisal edges of the anterior teeth. For a 2D validation, slices of 1 mm, not including incisal edges (part 4), were also cropped. These procedures were repeated in Group V, creating specific thresholds for each of the study parts. The 4 study groups were compared with its respective threshold using ANOVA test with statistical significance of 5%. Groups I, II and III did not differ from the corresponding threshold (Group V) in all study parts (p > 0.05). Scientific evidence to support the UHD was not observed in the current study. Bitemark analysis should not be disregarded but considered carefully when the suspects present similar dental alignment and morphology, such as in orthodontically treated subjects and twins, respectively.

Three-dimensional validation of the impact of the quantity of teeth or tooth parts on the morphological difference between twin dentitions

BACKGROUND

The number of teeth involved in cases of bite-mark analysis is generally fewer in comparison to the number of teeth available for cases of dental identification. This decreases the amount of information available and can hamper the distinction between bite suspects. The opposite is true in cases of dental identification and the assumption is that more teeth contribute to a higher degree of specificity and the possibility of identification in these cases. Despite being broadly accepted in forensic dentistry, this hypothesis has never been scientifically tested.

OBJECTIVE

The present study aims to assess the impact of the quantity of teeth or tooth parts on morphological differences in twin dentitions.

MATERIAL AND METHODS

A sample of 344 dental casts collected from 86 pairs of twins was used. The dental casts were digitized using an automated motion device (XCAD 3D® (XCADCAM Technology®, São Paulo, SP, Brazil) and were imported as three-dimensional dental model images (3D-DMI) in Geomagic Studio® (3D Systems®, Rock Hill, SC, USA) software package. Sub samples were established based on the quantity of teeth and tooth parts studied. Pair wise morphological comparisons between the corresponding twin siblings were established and quantified.

RESULTS

Increasing the quantity of teeth and tooth parts resulted in an increase of morphological difference between twin dentitions. More evident differences were observed comparing anterior vs. entire dentitions (p < 0.05) and complete vs. partial anterior dentitions (p < 0.05).

CONCLUSION

Dental identifications and bite-mark analysis must include all the possibly related dental information to reach optimal comparison outcomes.

The uniqueness of the human dentition as forensic evidence: a systematic review on the technological methodology

The uniqueness of human dentition is routinely approached as identification evidence in forensic odontology. Specifically in bitemark and human identification cases, positive identifications are obtained under the hypothesis that two individuals do not have the same dental features. The present study compiles methodological information from articles on the uniqueness of human dentition to support investigations into the mentioned hypothesis. In April 2014, three electronic library databases (SciELO®, MEDLINE®/PubMed®, and LILACS®) were systematically searched. In parallel, reference lists of relevant studies were also screened. From the obtained articles (n = 1235), 13 full-text articles were considered eligible. They were examined according to the studied parameters: the sample size, the number of examined teeth, the registration technique for data collection, the methods for data analysis, and the study outcomes. Six combinations of studied data were detected: (1) dental shape, size, angulation, and position (n = 1); (2) dental shape, size, and angulation (n = 4); (3) dental shape and size (n = 5); (4) dental angulation and position (n = 2); (5) dental shape and angulation (n = 1); and (6) dental shape (n = 1). The sample size ranged between 10 and 1099 human dentitions. Ten articles examined the six anterior teeth, while three articles examined more teeth. Four articles exclusively addressed three-dimensional (3D) data registration, while six articles used two-dimensional (2D) imaging. In three articles, both imaging registrations were combined. Most articles (n = 9) explored the data using landmark placement. The other articles (n = 4) comprised digital comparison of superimposed dental contours. Although there were large methodological variations within the investigated articles, the uniqueness of human dentition remains unproved.

A quantitative method for comparing human dentition with tooth marks using three-dimensional technology and geometric morphometric analysis

OBJECTIVE

To develop a quantitative method to compare 3D overlays from dental casts with experimental bitemarks by using geometric morphometric analysis.

MATERIALS AND METHODS

Thirteen upper and lower dental casts and corresponding simulated bitemarks were 3D-scanned to generate comparison overlays with DentalPrint software(©). This study considered the inter-canine distance and four incisal angles. A matrix was created to compare all possible combinations of matches and non-matches between models and bites, i.e. 169 combinations (13 models × 13 bites), of which 13 were true matches. For each combination, the percentage difference was calculated between the variables in the model and the same variables in the bitemark. Logistic regression was used to obtain a predictive model (algorithm) for a match, calculating the discriminative values (area under the ROC curve, sensitivity and specificity) for each measure and for the logistic model.

RESULTS

Statistically significant discriminative power was found for all single (angle or distance) and combined (logistic model) variables, with lower 95% CI limits > 0.50 for areas under the ROC curves and sensitivity/specificity values > 50% in both maxilla and mandible.

CONCLUSIONS

This quantitative method has sufficient discriminative power to be utilized in forensic cases.

Shape model of the maxillary dental arch using Fourier descriptors with an application in the rehabilitation for edentulous patient

The knowledge of teeth positions on the maxillary arch is useful in the rehabilitation of the edentulous patient. A combination of angular (θ), and linear (l) variables representing position of four teeth were initially proposed as the shape descriptor of the maxillary dental arch. Three categories of shape were established, each having a multivariate normal distribution. It may be argued that 4 selected teeth on the standardized digital images of the dental casts could be considered as insufficient with respect to representing shape. However, increasing the number of points would create problems with dimensions and proof of existence of the multivariate normal distribution is extremely difficult. This study investigates the ability of Fourier descriptors (FD) using all maxillary teeth to find alternative shape models. Eight FD terms were sufficient to represent 21 points on the arch. Using these 8 FD terms as an alternative shape descriptor, three categories of shape were verified, each category having the complex normal distribution.

Patterns of variation and match rates of the anterior biting dentition: characteristics of a database of 3D-scanned dentitions

An understanding of the variability of the anterior human dentition is essential in bitemark analysis. A collection of 1099 3D laser scans of paired maxillary and mandibular arches were studied using geometric morphometric methods. Analyses were performed without scale (shape only) and with scale (shape and size). Specimens differing by no more than experimentally obtained measurement error were counted as matches, or as indistinguishable. A total of 487 maxillary (396 size preserved), 131 mandibular (83 size preserved), and one paired dentition (two size preserved) matches were found. Principal component analysis and partial least squares revealed interpretable patterns of variation and covariation in dental shape, principally dominated by variation in dental arch width. The sensitivity of match rate to assumed degree of measurement error was also determined showing rapid increases in match rate as measurement error increased. In conclusion, the concept of dental uniqueness with regard to bitemark analysis should be approached with caution.

The examination and identification of bite marks in foods using 3D scanning and 3D comparison methods

Bite mark analysis offers the opportunity to identify the biter based on the individual characteristics of the dentitions. Normally, the main focus is on analysing bite mark injuries on human bodies, but also, bite marks in food may play an important role in the forensic investigation of a crime. This study presents a comparison of simulated bite marks in different kinds of food with the dentitions of the presumed biter. Bite marks were produced by six adults in slices of buttered bread, apples, different kinds of Swiss chocolate and Swiss cheese. The time-lapse influence of the bite mark in food, under room temperature conditions, was also examined. For the documentation of the bite marks and the dentitions of the biters, 3D optical surface scanning technology was used. The comparison was performed using two different software packages: the ATOS modelling and analysing software and the 3D studio max animation software. The ATOS software enables an automatic computation of the deviation between the two meshes. In the present study, the bite marks and the dentitions were compared, as well as the meshes of each bite mark which were recorded in the different stages of time lapse. In the 3D studio max software, the act of biting was animated to compare the dentitions with the bite mark. The examined food recorded the individual characteristics of the dentitions very well. In all cases, the biter could be identified, and the dentitions of the other presumed biters could be excluded. The influence of the time lapse on the food depends on the kind of food and is shown on the diagrams. However, the identification of the biter could still be performed after a period of time, based on the recorded individual characteristics of the dentitions.