Forensic odontology

DEFINITION: Scientific use of dentition patterns to identify individuals, living or dead, and to evaluate malpractice claims involving dental care and repair.

SIGNIFICANCE: Examination of dental patterns can be useful in the identification of crime and accident victims as well as skeletal remains, and in assault cases the analysis of bite marks can help investigators identify suspects. In civil cases, forensic odontologists provide testimony when claims are made concerning malpractice involving dental care.

The science of forensic odontology, also known as forensic dentistry, is based on the premise that dentition patterns differ across individuals in size, shape, pattern, wear, and repair. Differences are found even in identical twins, who have identical dentition patterns but have different histories of dental repair work. Forensic odontology is especially useful for identification if the dental records of the person of interest are available for comparison or a dentition sample can be obtained.

Practitioners of forensic odontology are highly trained and board-certified dental specialists who are tasked primarily with judicial cases in which dentition provides supporting or, in some cases, primary and also with identification of remains. Forensic odontologists typically have advanced education in dental anatomy, dental abnormalities, pathology, and the history and current uses of types and applications of dental materials, including crowns, bridges, and fillings. These specialists are also familiar with the dental treatment shorthand used in written dental records.

Identification of Remains

Dentition has been used for centuries to establish identities from human remains. Perhaps one of the most famous uses of forensic odontology was in the positive identification of the remains of Adolf Hitler and Eva Braun, but the science has gained worldwide attention in more recent years as a means of identifying remains following mass natural or human-made disasters, such as the 2004 tsunami in Thailand or the 2001 terrorist attack on the World Trade Center in New York City. Forensic odontology is also used in cases involving searches for missing persons. Because tooth enamel is one of the hardest and most enduring substances in nature, teeth often survive under conditions that destroy all other body tissues. For example, fire, motor vehicle accidents, and other tragedies may disfigure bodies so badly that nothing remains but teeth or portions of dental crowns.

Forensic odontology is particularly important for the identification of remains in cases where neither the victims’ fingerprints nor their DNA profiles are available in existing databases. Identification is facilitated when the deceased have had restorative dental treatments—such as fillings, crowns, root canal therapy, and bridges—and information about these treatments is preserved in dental records.

In identifying an individual based on remains, the first task of the forensic odontologist is to compile a postmortem dental record by taking X-rays (radiographs) and detailing the dental structures of the remains. The completed record of dental remains is then compared with the antemortem (before death) dental records of the person suspected to be the deceased to confirm or preclude identification. A positive or nearly positive identification can be established on the basis of a strong correlation between dental records and remains. Conversely, inconsistent comparisons may preclude or exclude identification for judicial use.

Generally, no recognized minimum number of concordant features is required to establish a positive identification. In some cases overall dental patterns may be sufficient to establish identity, whereas in other cases teeth that exhibit highly specific repairs can be used to identify remains positively with confidence. This variability in what constitutes confirmation of identity is one reason the evidentiary value of forensic odontology is treated cautiously. This means that forensic odontologists must be prepared to defend their conclusions in court proceedings.

In cases that lack antemortem dental records, forensic odontologists are confronted with a much more difficult task in determining identity. In such a case, the forensic odontologist prepares a hypothetical profile of the unknown person based on the dental remains; this profile may include approximate age, ancestry, sex, socioeconomic status, dietary habits, smoking habits, history of substance abuse, and health at the time of death. Age determination is based on the Gustafson method, which measures six signs of wear, or the Lamendin method, which evaluates degree of root transparency. Dental remains of older individuals can yield clues on the basis of types of fillings, materials in fillings, crown replacement techniques, and other repairs, all of which have changed over time as newer dental techniques have been developed. If sufficient material is available, DNA analysis can show the presence or absence of the male Y chromosome. The hypothetical profile and observed characteristics are then compared with the characteristics of known missing persons or entered into a database for future comparisons.

Analysis of Bite Marks

Forensic odontologists are also tasked with the assessment of bite-mark injuries, which are frequently present in violent crimes. Bite marks include those inflicted on the victim, those that the victim inflicted on the attacker, and bite marks found on any food or other objects at the crime scene. Bite marks often occur in cases of sexual assault as well as cases.

In assessing bite-mark evidence, the first tasks of the forensic odontologist are to photograph the bite mark, record an impression of the bite mark, and take dental impressions of the suspected source of the bite mark (a practice permitted by law in most states). In establishing bite-mark evidence, the forensic odontologist considers the depth and shape of indentations and resulting pitting, tearing, and other abrasions. Measurements taken include distance between cuspids and other teeth impressions, shape of the mouth arch, width and thickness of the teeth, spacing between teeth, gaps where teeth are missing, curves of biting edges, and unique dentition and wear patterns.

A powerful bite leaves a deep impression, and this information may reveal something about the state of mind of the assailant. In assessing a bite mark, the forensic odontologist looks for hemorrhage, abrasion, contusion, laceration, puncturing, avulsion (removal of part of the skin), and artifact (removal of part of the body). Each of these factors, when present, is next classified into one of four degrees of impression: clearly defined, showing significant pressure; obviously defined, showing first-degree pressure; noticeable, showing violent pressure; or lacerated, in which the skin is violently torn from the body. Amount or degree of bite impression is considered a measure of violence and is typically used in court to identify the assailant’s state of mind, aggravating circumstances, or simply heinous behavior on the part of the assailant.

The use of forensic odontology in assault cases is not without controversy. Critics assert that the use of bite marks as evidence is inevitably subjective because little agreement exists among scientists about the uniqueness of dentition or the behavior of the human skin when bitten. Some individuals bruise easily, others almost not at all. Critics also point out that the rates of healing of bite marks may vary as a function of the health of the victim. Forensic examination of bite marks on dead bodies is further complicated by the rapid skin decay that follows death. Finally, error rates associated with identification of assailants based on bite-mark analysis have not yet been established through rigorous scientific experimentation and analysis. Thus, some argue that bite-mark analysis may be given too much credit as an evidentiary source, especially when it is used in trials to establish the identities of assailants.

The results of bite-mark analysis can provide supportive evidence when considered together with DNA or fingerprint analysis, however. Among the high-profile criminal cases that have included bite-mark evidence are the case against serial murderer Ted Bundy, brought by the state of Florida in 1979, and the New Jersey case against Jesse Timmendequas for the abduction and murder of seven-year-old Megan Kanka (the crime that precipitated the passage of Megan’s Law in 1994). The 1975 California court case People v. Marx helped to establish evidentiary standards for the use of forensic odontology in trials.

In 2022, the National Institute of Standards and Technology (NIST), an agency with the US Commerce Department, released a study that called into question the accuracy of forensic bite-mark analysis. The NIST found that the elasticity of human skin did not allow bite marks to be transferred consistently. Furthermore, the study cast doubt on the uniqueness of individual bite marks and whether they can be used to exclude suspects in an investigation.

Medical Malpractice Claims

To evaluate claims of malpractice involving dental care or repair, forensic odontologists examine dentition and oral tissues to establish the degree of trauma, its possible cause, and its potential impact on ability to chew food properly. Some dental malpractice suits claim that careless or improper dental work has resulted in alterations of the face, jaw, or chin, whereas others focus on unnecessary dental work. In all such cases, forensic odontologists must examine the claimants and present regarding their findings.

Bibliography

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Dinkel, E. H., Jr. “The Use of Bite Mark Evidence as an Investigative Aid.” Journal of Forensic Sciences 19 (July, 1974): 535-542. Print.

Dorion, Robert B. J., ed. Bitemark Evidence. New York: Marcel Dekker, 2005. Print.

"Forensic Bitemark Analysis Not Supported by Sufficient Data, NIST Draft Review Finds." National Institute of Standards and Technology, 11 Oct. 2022, www.nist.gov/news-events/news/2022/10/forensic-bitemark-analysis-not-supported-sufficient-data-nist-draft-review. Accessed 15 Aug. 2024.

Keiser-Nielsen, Søren. “Dental Identification: Certainty v. Probability.” Forensic Science 9, no. 2 (1977): 87-97. Print.

Mohammed, Faraz, Arishiya T. Fairozekhan, Subraya Bhat, and Ritesh G. Menezes. " Forensic Odontology." StatPearls, 14 Aug. 2023, www.ncbi.nlm.nih.gov/books/NBK540984/. Accessed 15 Aug. 2024.

Senn, David R., and Richard A. Weems. Manual of Forensic Odontology. 5th ed. Boca Raton: CRC, 2013. Print.