Current Concepts and Trends in Forensic Odontology: An Overview

Introduction

The word ‘forensic’ is derived from the Roman word ‘forum- the home of the law courts’ which means “relating to the law”.¹ Forensic odontology is a challenging and interesting branch of forensic science that involves the application of science and technology for the identification and investigation of crimes and the administration of justice. It has garnered attention throughout the world as an empowering field for applying science to legal formalities.²

The methods used in identification include dental comparisons, finger, palm, or footprints’ deoxyribonucleic acid (DNA) identification, and radiographic superimpositions.³ Dental identification plays an important role in cases where postmortem alterations occur to such an extent that the body is mutilated that fingerprints cannot be recorded.⁴

In this advanced era of genomics and proteomics, the field of forensic odontology has been evolving and expanding its ability to be more potent with the help of proteins and DNA as unique identifying techniques. The technique uses genomic and mitochondrial DNA from various structures of teeth and associated cells that include cells from pulp, dentin, or cementum, and desquamated cells that are present in saliva.⁵ In the practice of dentistry, dentists encounter various non-accidental injuries that require attention.⁶ Forensic odontologists’ active engagement in all steps of human identification, as well as their ability to respond to new issues with identification procedures, may make forensic odontology a humanitarian tool.

As the world is evolving, newer technologies and scientific methods have made progress. However, the role of forensic odontology remains an integral part of forensic medicine as it supports and helps in various sections of forensic science. This review is focused to explain various evolutionary changes, concepts, and trends that have happened over the past few decades in the field of forensic dentistry.

Various Aspects of Forensic Odontology

Dental Identification

The availability, sufficiency, and accuracy of antemortem dental records are important factors in forensic dental identification. Dental records are a vital component that provides a source of information for dentists and patients for medicolegal, administrative, and forensic purposes. Comparative dental analysis, like fingerprints and DNA analysis, plays a vital role in identifying people.⁷

Dental identification can be performed by examining the previous dental records of the deceased person to identify the similarities and confirm the same.^8,9

Dental profiling, as established by Acharya et al., is another important aspect of forensic dentistry that helps in the identification of a person by determining his/her race, gender, and age.₁₀ Metric features of teeth such as buccolingual and mesiodistal dimensions, and canine and molar morphology can also be utilized to determine gender.¹¹

According to the American Board of Forensic Odontology, dental identification methods can be divided into:¹²

• Positive identification: The antemortem and postmortem data match and thus it can be established that it is from the same individual.

• Possible identification: Although there are similarities between the equivalent items in the antemortem and postmortem databases, neither source contains enough information to allow for definitive identification.

• Insufficient identification evidence: Although there is insufficient supporting evidence for comparison and definite identification, the decedent’s presumed identity cannot be ruled out. After then, the identification is judged inconclusive.

• Exclusion: In the antemortem and postmortem databases, there are unexplained variations between comparable items. Sometimes there are explainable differences, like alterations in restorations over a while, tooth avulsion owing to trauma at death, or subsequent treatment by a second party that is not recorded in the antemortem record. The differences in all of these examples can be explained and identification can still be established.

Bite Mark Analysis

In forensic sciences, odontology evidence is the third most accurate technique of fingerprint and DNA analysis identification. According to a study by Pretty and Turnbull, the bite mark analysis is based on the factor that human dentition is unique and its uniqueness is rendered during biting that aids in the identification.¹³ Bite marks can deform because of the flexibility and elasticity of the skin. The amount of pressure exerted while biting, along with the body posture and the angle of the maxilla and mandible during the bite, can all determine the appearance of a bite mark .¹⁴

Literature reveals different methods for bite mark analysis like manual, radiographic, and computedassisted techniques. According to the studies of Van der Velden et al.,¹⁵ and Osman et al.,¹⁶ indirect methods for bite mark analysis using computed-assisted techniques were more accurate.

The American Board of Forensic Odontology (ABFO) guidelines state that the evidence should be gathered from both the victim and the suspect and a proper basis for evidence collection should be instituted. Any variations from these recommendations and guidelines should be questioned.¹⁷

DNA Analysis

It is a novel tool employed in forensic investigations due to its ability to overcome the effects of traumatism, heat, and autolytic processes. In addition, it allows investigators to perform DNA typing with minimal resources. ¹⁸ DNA is found in various parts of the teeth, such as the pulp tissue, the cement, and the alveolar bone. In forensic cases, DNA can be extracted using a variety of methods.7 Genomic DNA and mitochondrial (mt) DNA are used in forensic investigations.

DNA profile tests are widely used for determining a person’s physical characteristics. They can provide vital information such as ethnicity, sexual orientation, and place of origin of a person.¹⁹ Few of the newer methods used in DNA profiling are restriction fragment length polymorphism (RFLP) typing, short tandem repeat (STR) analysis, Y chromosome analysis, single chromosome polymorphism analysis, and DNA methylation analysis.²⁰

In 1991, Schwartz et al. extracted high molecular weight (HMW) proteins from the teeth under a variety of circumstances, including pH, humidity, temperature, and storage. The capacity to extract HMW human DNA from tooth pulp was shown to be unaffected by the environmental conditions studied.²¹

In 1992 Potsch et al. used the biotinylated repetitive DNA probe pH Y 2.1 to perform genomic dot blot hybridization for the identification of sex, and sex was properly categorized in all cases using 50–100 ng target DNA from the pulp.²² Sweet and Sweet presented a noteworthy report of the many cases of DNA isolation from teeth mentioned in the literature. A preserved, unerupted third molar was used to extract 1.35 g DNA from the tooth pulp in this case of human remains identification.²³ Comparative dental identification, reconstructive postmortem, dental profiling, and DNA profiling are the four types of personal identification situations that use teeth, jaw, and orofacial traits.²⁴

Age Estimation

Physical examinations such as anthropometric measurements, skeletal maturation, dental age estimation, and a combination of dental development aid in the process of identification of human beings.²⁵ Due to the low variability of dental markers and false age assertions by live adults, dental maturity plays an essential role in assessing the chronological age of individuals.

According to Gordon et al., the analysis of teeth can provide a pretty accurate estimate of age between infancy and childhood.²⁶ According to Gonzales et al., teeth analysis can provide a valuable source of information during childhood and adolescence. However, beyond adulthood, the changes are too unpredictable to be useful.²⁷

According to Scot, if the third molars have fully erupted, the person is above 17 years; if the root growth is incomplete on X-ray, the person is probably under 25 years.²⁸ The tooth germs appearance, the earliest trace of mineralization that can be detected, the degree of completion of the unerupted tooth, the rate of enamel formation and neonatal line formation, attrition of crown, and root dentin transparency are the several factors used for age determination using the dentition.²⁹

Cheiloscopy

Cheiloscopy is a forensic procedure that uses human lip traces for identification. It is commonly used to compare the results of an autopsy and a patient’s postmortem examinations.³⁰ Unlike other methods, lip prints are unique and do not change during the lifetime of a person. They provide forensic investigators with sufficient information to perform their investigations.³¹

The lip print pattern is determined by the mouth being open or closed. The lip has well-defined grooves when the mouth is in a closed position, whereas the grooves in the open-mouth posture are ill-defined and difficult to understand. Changes in lip prints can also be caused by missing anterior teeth leading to support loss in that area. Lip print recording can be hampered by debris or moisture on the surface of the lip, a dense lipstick layer, or overstretching of cellophane tape.³²

Rugoscopy

In mammals, the presence, number, and arrangement of palatal rugae vary by species.³³ They are asymmetrical in humans, which is a unique trait of humans.^34,35 Palatal rugae can be utilized as a complement in edentulous mouths where postmortem identification of dental status is not possible. Many academics are concerned about the prospect of palatal rugae pattern alterations with aging and other external stimuli. Orthodontic tooth movement, neighboring tooth extractions, surgery of cleft palate, periodontal surgical procedures, and forced eruption of impacted canines are a few of the issues that need to be addressed.³⁶

Determination of Sex

Sex determination is a crucial subset of forensic odontology that aids in an unknown person’s identification following natural calamities, as well as chemical and nuclear bombing situations. There are four ways to do it:³⁷

1. Dimension and morphology of the craniofacial complex: The mastoid, supraorbital ridge, skull size and architecture, zygomatic extensions, nasal aperture, and mandible gonial angle, as well as the pattern established by these traits, are all taken into consideration.

2. Sex difference in dimension of tooth: The most reliable approach for sex determination is to measure the mesiodistal and buccolingual dimensions. In males, both dimensions are larger than in females.

3. Tooth morphology: The male canine has a more prominent distal accessory ridge than the female. In females, the mandibular first molar has fewer cusps. These characteristics may be due to an evolutionary reduction in the size of the female lower jaw.

4. DNA analysis for sex determination: According to Das and his colleagues’ investigation, sex determination might be acquired up to four weeks after death by examining the X and Y-chromosomes.

Tongue Prints

The tongue like any other organ has its share of skeletal muscles, blood vessels, and nerve supply. In addition, it is bestowed with papillae and taste buds.³⁸ Tongue print has numerous advantages over biometric systems that use fingerprints, voice checks, and retinal scans. The form and surface textures of the tongue are unique to each individual. It can be easily exposed for investigation because it is an internal organ, and the exposed surface has the necessary information. The texture and shape of the human body remain unchanged. It is highly shielded from the outside world and hence is unaffected by external influences. It also serves as a dependable indicator of life.³⁹

The left lateral, right lateral, and profile view can all be used to create a tongue biometric template. For analysis of the texture, a normalized histogram with Scale Invariant Feature Transform is applied, while the extraction of tongue algorithm of collecting points provides a good template for the tongue shape. Matching is accomplished by integrating the templates from both extraction procedures.

Recent Trends In Forensic Odontology

Facial Reconstruction:

Forensic facial reconstruction is a quick, non-invasive, and effective approach for identifying people from skeletal remains. This forensic tool combines scientific approaches with artistic abilities.⁴⁰ There are two sorts of reconstruction techniques: two-dimensional (2D) and three-dimensional (3D).⁴¹

In the case of 2D face reconstruction, the method focuses to re-create the face from the skull using estimates of soft tissue depth based on the antemortem photographs.⁴² In the case of 3D manual reconstruction, a recreation of the face is performed by using clay, plastic, or wax directly on the skull of the victim which is to be identified. This method employs tissue depth markers of particular lengths to specify various depths of soft tissue.⁴³

Various methods for manual 3D reconstruction include :

• Tissue Depth Method: This technique was developed by Krogman in 1946. In this method, fine measurements were determined using needles, X-rays, or ultrasound where soft tissue depth data is collected with the support of highly trained proffesionals.⁴⁴

• Anatomical Russian Method: This technique of facial reconstruction was developed by Gerasimov in 1971 where facial muscles were used in anatomical position layer by layer over the skull rather than soft tissue depth data.⁴⁵

• Manchester/British Procedure: The most widely utilized method, introduced by Neave in 1977, uses both soft tissue thickness and facial muscle for facial restoration. The depth of facial tissue is calculated by the age and gender of the individual, build, and other factors.⁴⁶

• Computerized 3D Forensic Facial Reconstruction: With the newer advances in 3D technology, the computer-aided forensic facial reconstruction method was developed using the manual clay model technique to model the face onto the skull.⁴⁷

Denture Identification Methods

Denture marking systems are beneficial because they aid in identifying patients following natural and mass catastrophes, identification of prostheses in elderly institutions, regeneration of dental records in emergencies such as accidents, diagnosis, and decision assistance in medico-legal cases.⁴⁸

Furthermore, identifying dentures simplifies the recording and preservation of patient information on easily accessible systems. Denture labeling methods can be classified under two categories: the surface marking method and the inclusion method. The surface marking method is relatively inexpensive and easy to apply. There is no requirement for skilled personnel, but the disadvantage is that they wear off quickly. The inclusion method is relatively more permanent and provides a more predictable result, but it could create porosity, thus leading to the weakening of the denture. Another disadvantage is that it is more expensive and is usually made by trained personnel in dental laboratories.⁴⁹

Conclusion

Forensic odontology is a discipline of forensic medicine that is now considered to be an essential and indispensable specialty and is regarded as one of the most reliable and cost-effective scientific approaches for successful victim identification when used in conjunction with other methodologies. The various methods of data collection along with other supplementary methods used in forensic dental identification have gone through considerable changes in the past decade. With the advancement of newer technologies in DNA analysis and face reconstruction, forensic odontology can reach new heights in the near future.

Conflict of interest

None