|Year : 2016 | Volume
| Issue : 1 | Page : 31-35
Bitemarks - A review
Dhanya S Rao1, IM Ali2, Rajeshwari G Annigeri2
1 Department of Oral Medicine and Radiology, A. J. Institute of Dental Sciences, Davangere, Karnataka, India
2 Department of Oral Medicine and Radiology, College of Dental Sciences, Davangere, Karnataka, India
|Date of Web Publication||12-Apr-2016|
Dhanya S Rao
Department of Oral Medicine and Radiology, A. J. Institute of Dental Sciences, Davangere, Karnataka
Source of Support: None, Conflict of Interest: None
Teeth have been used as tools and weapons since the advent of time. Bite marks inflicted by them during violent interactions, form the basis for one of the most intriguing, broad and sometimes controversial encounters in forensic dentistry. Bite mark evidence validates the involvement of the alleged biter in the crime, assuming that the person who made the bite was the one who committed the crime. Forensic odontologist has to determine that the pattern injury is a bite mark record and it represents a human bite and has to make a decision as to its evidentiary value. This recognition and examination of the bite marks and their subsequent comparison with suspects, may lead to criminal identification thereby resolving the crime. This article aims at providing complete review on formation, collection and identification of bitemarks.
Keywords: Bite mark, forensic odontology, teeth
|How to cite this article:|
Rao DS, Ali I M, Annigeri RG. Bitemarks - A review. J Dent Res Rev 2016;3:31-5
| Introduction|| |
Recent world shows changes in social, economic, educational, and developmental technologies. As there are newer advances, man is getting more and more selfish in his demands. The advent of new thinking has involved all fields, and the field of crime is no exception. As the saying by Winston Churchill goes, "The victim shapes and molds the criminal" newer advances in other fields especially medicine and dentistry is essential in solving the mysteries of death due to crime. Each dentition, including the number of teeth, their position, occlusion, and the restorations are unique for each individual. This makes forensic odontology play a key role in identifying the deceased. A bite mark may be defined as having occurred as a result of either a physical alteration in a medium caused by the contact of the teeth, or a representative pattern left in an object or tissue by the dental structures of an animal or human. 
| History|| |
Although the field of forensic odontology appears to be a new one, it is probably as old as Human kind itself as supported by the Bible which says, Eve persuaded Adam to put a "bite mark" in an apple.  The first incident of bite mark identification occurred in 1692 which is termed Salem Witch Trials. , A piece of cheese in the scene of robbery registered with a bite mark played a role in revealing the thief's identity and thereby solving the case in America.  The most highly publicized bite mark case which paved the path for bite mark evidence to be used in courts was the case involving serial killer Theodore (Ted) Bundy, who was convicted based on bite-mark analysis by the US judicial system. 
A classical human bite mark is circular or oval patterned injury consisting of two opposing symmetrical, U-shaped arches separated at their bases by open spaces.  The periphery of the arches can have abrasions, contusions, lacerations, etc., indicative of distinctiveness of the occlusal surfaces of the biting dentition.  Usually, mandibular anterior teeth are detected more obviously than the maxillary teeth in bite marks, which is owed to mandibular jaw movement during bite inﬂiction.  The bite mark is produced due to teeth pressure and starts with mandibular closure, followed by suction on the skin (as a negative pressure). Tongue thrusts can accompany the opposite action of mandible which are seen as tongue projections on teeth incisor and lingual surfaces. , About 11 kg pressure is exerted from the incisors and along with the tongue, it may reach up to 8 lb/square inch. Suction may produce a negative pressure of 20 mmHg. 
Bite mark is unique
The scientific foundation of bite mark analysis is entrenched in the idea of the distinctiveness of the human dentition, the conviction that no two humans have identical dentition. The unique characteristic of a suspected individual's dentition is compared with the pattern observed over the bitten skin, and two simultaneous and opposite paths develop: 
- The inclusive path where the suspected biter's dentition can be positively identified due to strong and consistent tooth and arch comparison with the pattern recorded
- The exclusion path where the suspected biter's dentition does not match with the patterns recorded in the bite mark injury and the suspect can be excluded as being the cause for the bite mark. Exclusion is usually accomplished more frequently than the inclusion.
| Variations in Bite Mark|| |
- A central ecchymotic area or "suck mark" surrounded by radiating linear abrasions resembling a "sunburst" found usually after sexually oriented crime.  The central ecchymosis is due to the negative pressure during biting, leading to leakage or rupture of the small vessels and capillaries and linear abrasions caused by the movement of the teeth. Imprint of the inner surface of teeth against the skin is called lingual marking or drag marking 
- The second type closely resembles a "tooth mark" pattern. This is an "attack" or "defense" bite mark seen most often in "batteral" child homicide. 
Furthermore, double bite can be seen when two bites are done quickly in the same location on the skin whereas partial bite marks can be seen in situations when the victim moved during the bite. 
| Classifications of Bite Marks|| |
Camerons classification: 
- The agents that produced the mark
- The materials and substances that have exhibited the marks.
- Tooth pressure marks: By incisal edges of anterior teeth - stable with minimal distortion
- Tongue pressure marks: Tongue pressure on palatal surfaces of the teeth, cingulae or palatal rugae causes distortion of marks
- Tooth scrape marks: Caused due to irregularities in teeth due to fractures, restorations, etc.
- Complex marks: Combination of above marks.
- Type I: Bites in chocolate which fracture easily with limited depth of penetration. Most prominent are incisal edges of upper and lower anterior teeth
- Type II: Good grip of material obtained by teeth and then bitten piece is fractured from main material. For example, Apple; The outline of labial aspect of upper and lower incisors are recorded
- Type III: Bite mark produced by biting through cheese. Here, an advantage is that it indicates relative position of upper and lower incisors in centric occlusion.
| Bite Variables Affecting Bite Marks|| |
Patterns of distribution of bite marks are based on the type of crime involved and the age,sex and site mentioned in [Table 1].
Terms used to describe bitemarks are:
- Unique: Here, the bite mark is distinctive and unusual in such a way that no other individual could have made an identical pattern with their dentition
- Distinctive: Highly specific and individualized, varies from normal, i.e., unusual or infrequent
- A definite (positive) bite mark is termed when there is no doubt that the mark was caused by teeth, and other conditions have been considered and eliminated
- Highly probable suggests with virtual certainty of the mark being a bite mark, but there is room for possibility of another cause, although this is highly unlikely
- Possible/similar to/consistent with/conceivable/maybe/ cannot be ruled out/cannot be excluded: These terms imply that the bite mark could be produced by teeth or could be created by something similar which produces marking that looks like a bite mark
- Unlikely/inconsistent - used when it is unlikely that the injury pattern is bite mark
- Incompatible/excluded/impossible implies that it is not a bite mark but something else
- Indeterminable/should not be used/insufficient. The pattern is such that it could be related to teeth or a tooth as a cause of injury.
Terms describing the injury are: Point (match point or a consistent point): Used for comparison or evaluation. This term does not imply any degree of specificity but represents a focus in comparison.
A concordant point (also called as matching point/unit of uncertainty) is a point of comparison seen in both the bite mark and the suspect's exemplariness. It could also represent on an area that can be linked to a particular tooth and an area of injury which could have caused the bite mark.
The area of comparison is a specific region to be compared. It may also represent a group of features, that impart themselves to exact or merely exact correlation.
Match or positive match is a nonspecific term suggesting some degree of similarity between a single feature, groups of characteristics or a majority of the entire case, but there is no degree of known specificity.
The term consistent with means that there is a "match" between two or more things in a bite mark, but there is no degree of presences implied in the use of the term.
The term reasonable medical/dental certainty implies that the investigator is extremely confident that the suspect matches the bite. This also implies that any other expert with similar training, experience, and background when evaluating the same evidence would come to the same conclusion and any other opinion would be unreasonable. 
American Board of Forensic Odontostomatology (ABFO) Guidelines for Evidence Collection - The ABFO launched standardized guiding principle in 1986: 
History followed by description of bite marks  including the demographics, location, shape, color, surface, and size of the bite mark should be described.
Photographs - extraoral photographs involving profile and facial views, intraorals including, lateral views and occlusal views of each arch should be taken and preserved. Along the bite mark, a standard scale like ABFO 2 should be used [Figure 1].
|Figure 1: Bite mark measurement using American Board of Forensic Odontostomatology scale|
Click here to view
Extraoral examination - soft tissue and hard tissue factors influencing biting dynamics should be recorded. Maximal opening and any alterations on opening or closing should be measured.
Intraoral examination - salivary swabs needs to be used. The periodontal status should be noted. Tongue position can be recorded. A dental chart should be prepared if possible.
Impressions - using ADA-specified materials two impressions of both arches should be taken. Occlusal relationship needs to be recorded. ABFO guidelines state that "Impression should be taken on the surface of the bite mark evidence, whenever it appears that this may provide useful information." Impression provides the current relationship with reference of curvature. ,
Bite samples - sample bites should be made using a suitable material, simulating the type of bite Study casts - type II stone is used for cast preparation [Figure 2]. Additional casts can be made by duplicating the master casts.
The standard protocol should include photographing the evidence, both in color and black and white, first without scales and then with them and also a location photograph to show where exactly in the body the mark is found.
The size consideration in using the scale is in positioning it relative to the bite mark and to the portion to be depicted, so as to avoid parallel distortion for accuracy. An ABFO no 2 scale is used.  Since a photograph is flat representation of three-dimensional object camera must be oriented for successive photographs to be taken over the curved surfaces with principal object plane parallel to film plane and at right angles to long axis of lens  [Figure 1] and [Figure 2].
Conventional 35 mm photography is usually used, and both color and black and white photos can be taken.  In visible light photography, the slowest speed film is appropriate. (American Society of Anesthesiologists speed ≤100), because greater will be the grain density and sharply detailed photo will be obtained which is not lost even when photo is enlarged to life size.
Other that visible light photography, ultraviolet (UV) light and infrared (IR) light photography can be used. UV light photograph produces greater details of the surface of the injury; the IR light photograph captures the bleeding pattern below the skin of the bite mark.
Epiluminescence microscopy (used for dermatologic evaluation of pigmented skin lesions) also can be used which renders stratum corneum translucent and aids visualization and photographic documentation of bite marks. 
Here, digital camera captures image in charged couple device's that can be transferred to computer for processing and printing. Image softwares like DIMS etc., have to be used.  Bite mark analysis digitized helps in:
- Sharpening out of focus shots
- Correcting poor contrast and brightness value
- Color balance correction
- Cropping of unwanted elements
- Correction of improper photographic reproduction and distortions.
Swabbing of the bite injury is done to recover trace evidence. It is estimated that 0.3 ml of saliva is deposited when making a bite mark and spread over 20 cm 2 Double swab method is followed wherein the first swab is moistened with distilled water and run over the surface after which a dry swab is used to absorb the extra moisture and then air dried.
Bite print recording
Bite mark is brushed with fingerprint lifting powder and then fingerprint lifting tape can be used to record.
In the living individual, a biopsy could be considered if there were sufficient scientific reasons and some contributions to the case could be gained.  In deceased the entire area of bite mark is excised. Whenever possible it should be removed with proper anatomic condition. Excised tissue can be transilluminated by shining light from dermal side or inner aspect of tissue. This aids in the enhanced viewing of bleeding patterns caused by teeth. ,,
Distortions of Bite marks - Sheasby and MacDonald (2001) recommend a classification to emphasize the need of a scientific approach for the interpretation of the types of distortion.
- Primary distortion is defined by the dynamics of the bite
- Secondary distortions have three categories: Time-related distortion when a bite changes with time elapsed subsequent to the bite being made, posture distortion, and photographic distortion.
Bite mark evaluation
Image sizing, accurate measurement, distortion correction, color isolation, and contrast enhancement can be done using Adobe software.
DNA in bite marks
With the advent of the DNA sequencing in 1977, followed by the development of polymerase chain reaction (PCR) in 1983, DNA technology has an outstanding position in forensic sciences.  Saliva deposited during biting has DNA present which can be an important alternative hub in bite mark analysis. DNA from the cellular material present in the biter's saliva can be differentiated from the DNA of the victim's skin. It has been reported that this evidence is stable on intact skin for at least 60 h following deposition.  David Walsh et al. did the first separation of DNA from saliva and saliva-stained materials in 1992. 
| Bacteria Recovery from Bite Marks|| |
Brown et al. in 1984 gave the concept of utilizing oral bacteria from bite marks for forensic purposes.  Streptococcal DNA is used to match a bite mark to the teeth of the biter based on the streptococcal sequence data.  In a study done based on DNA extraction followed by PCR for Streptococcus salivarius and Streptococcus mutans detection in bite marks, 100% and 90% cases respectively showed their presence.  In another similar study, it was seen that S. salivarius and S. mutans DNA were positive in 83.5% and 67.1% cases respectively and were not detected in other body fluids.  In another study done based on genotypic matching of oral streptococci, the biter was identified among 8 individuals, as none of the bacterial genotypes were shared among the participants. 
| Medicolegal Aspects|| |
Sex-related crimes, domestic abuse, and child abuse are most probable cases for bite mark formation. It is important to realize that all members of the dental team have an exclusive chance and a legal commitment to support the victims. These injuries may be observed during the course of dental treatment. Determination of the evidentiary value of the bite mark involves a cascade of complex and interrelated events beginning with the collection of bite mark evidence from the victim, subsequent analysis of the bite mark and the eventual comparison with dental evidence collected from any potential biter. An analysis was done in the USA to know if dentists were aware of their legal role in cases of child abuse. Among the group of general dentists, oral surgeons, and pediatric dentists including a total of 537 participants, 242 (45%) knew about their role in suspected child abuse, 149 (28%) knew the name of the agency to which to report, 403 (75%) had seen cases of orofacial trauma, and 45 (8%) had suspected cases of child abuse in their practice. However, only four cases (<1%) were actually reported reason being, difficulty to confirm the suspicions. 
Though bite mark analysis remains the most controversial and questioned entity. There is few fundamental tribulations integral in bite mark analysis and interpretation: 
- Scientific evidence for establishing uniqueness of human dentition is not yet published
- The ability to transfer the dentition pattern is not very accurate as distortion, and its effects are not fully understood
- A standard for the number and quality of individual characteristics required to reach validation standards in legal justice system is absent
- Standardized terminology and coverage are not yet there
- Accuracy, reliability, and bias in bite marks are not satisfactorily studied.
| Conclusion|| |
Human bite mark analysis one of the most challenging and intricate part of forensic dentistry. Bite marks can be distorted by the elastic properties of the skin or by the anatomic location. The greatest challenge in Forensic Dentistry is analyzing bite marks found in human skin, because of the distortion presented and the time elapsed between the production and the analysis.  Furthermore, though the individuality of human dentition is observed commonly in practice, there is no database to express quantitatively the uniqueness of the human dentition. There is a demand on the field of bite mark analysis for research to adhere to more stringent scientific regulations in order for it to be more resilient to scientific scrutiny. Hence, bite mark analysis by itself should not be permitted to lead to a guilty decree, but it will proffer the opening to eliminate a suspect from crime when the data do not correspond.
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Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2]