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| title | chunk | source | category | tags | date_saved | instance |
|---|---|---|---|---|---|---|
| Forensic dentistry | 4/7 | https://en.wikipedia.org/wiki/Forensic_dentistry | reference | science, encyclopedia | 2026-05-05T09:19:59.890392+00:00 | kb-cron |
=== Proposed theoretical basis === Bites can occur on both the victim and the suspect; teeth are used as a weapon by the aggressor and in self-defense by the victim. Although they are only a small portion of most forensic dentists' caseload, bite marks represent the most challenging aspect of the discipline. In addition to the location of the bite mark, the type of severity of the injury may give investigators clues as to the mental state of the offender. Bite marks may be found on the flesh of victims of a violent attack, particularly on the stomach or buttocks. Bite mark evidence may be the only form of physical evidence found on a body. Alternatively, they may be found on the suspect, left by the victim during self-defense. Bite marks can be altered through stretching, movement, or change in environment after the bite. Skin is not ideal for holding the shape of a bite mark as it can become distorted due to the viscoelasticity of the skin. There is also no set standard by which to analyze and compare bite marks. Factors that may affect the accuracy of bite mark identification include time-dependent changes of the bite mark on living bodies, effects of where the bite mark was found, damage on soft tissue, and similarities in dentition among individuals. Other factors include poor photography, impressions, or measurement of dentition characteristics. Most bite mark analysis studies use porcine skin (pigskin), because it is comparable to the skin of a human, and it is considered unethical to bite a human for study in the United States. Limitations to the bite mark studies include differences in properties of pigskin compared to human skin and the technique of using simulated pressures to create bite marks. Although similar histologically, pigskin and human skin behave in dynamically different ways due to differences in elasticity. Furthermore, postmortem bites on nonhuman skin, such as those used in the experiments of Martin-de-las Heras et al., display different patterns to those seen in antemortem bite injuries. In recognition of the limitations of their study, Kouble and Craig suggest using a G-clamp on an articulator in future studies to standardize the amount of pressure used to produce experimental bite marks instead of applying manual pressure to models on pigskin. Future research and technological developments may help reduce the occurrence of such limitations. Kouble and Craig compared direct methods and indirect methods of bite mark analysis. In the past, the direct method compared a model of the suspect's teeth to a life-size photograph of the actual bite mark. In these experiments, direct comparisons were made between dental models and either photographs or "fingerprint powder lift models." The "fingerprint powder lift" technique involves dusting the bitten skin with black fingerprint powder and using fingerprint tape to transfer the bite marks onto a sheet of acetate. Indirect methods involve the use of transparent overlays to record a suspect's biting edges. Transparent overlays are made by free-hand tracing the occlusal surfaces of a dental model onto an acetate sheet. When comparing the “fingerprint powder lift” technique against the photographs, the use of photographs resulted in higher scores determined by a modified version of the ABFO scoring guidelines. The use of transparent overlays is considered subjective and irreproducible because the tracing can be easily manipulated. On the other hand, photocopier-generated overlays where no tracing is used are considered to be the best method in matching the correct bite mark to the correct set of models without the use of computer imaging. While the photocopier-generated technique is sensitive, reliable, and inexpensive, new methods involving digital overlays have proven to be more accurate. Two recent technological developments include the 2D polyline method and the painting method. Both methods use Adobe Photoshop. The use of the 2D polyline method entails drawing straight lines between two fixed points in the arch and between incisal edges to indicate the tooth width. The use of the painting method entails coating the incisal edges of a dental model with red glossy paint and then photographing the model. Adobe Photoshop is then used to make measurements on the image. A total of 13 variables were used in the analysis. Identification for both methods was based on canine-to-canine distance (one variable), incisor width (four variables), and rotational angles of the incisors (eight variables). The 2D polyline method relies heavily on accurate measurements, while the painting method depends on the precise overlaying of the images. Although both methods were reliable, the 2D polyline method gave efficient and more objective results.
=== Criticism of bite mark analysis === Bite mark analysis has been criticized by the President's Council of Advisors on Science and Technology (PCAST). The PCAST has identified that bite mark analysis is an area which lacks clear standards in regards to the features needed to identify a particular set of dentition as having created a particular mark. The analysis of bite marks is subjective and is highly criticized. So called bite mark analysis has been criticized as largely unscientific based on three pillars of critique: