caption: Image showing radix entomolaris. Credit: Shanmathy Sureshbabu et al.
In the past, to identify a person's sex, origin, and identity, the morphology of the teeth was studied. Non-metric dental traits are traits that can be passed down genetically but exhibit diversity in expression both within and between populations. Inadequate historical records about previous armed conflicts, natural or mass disasters that produced such human remains, severe damage or fragmentation, missing elements, and poor preservation all make the process of forensic anthropological identification of commingled human remains recovered from diverse contexts more difficult and complex.
An essential part of biological anthropology and forensic anthropology, non-metric dental features provide unique insights into the evolutionary history and genetic makeup of the human population. Non-metric attributes, as opposed to traditional metrics, concentrate on the qualitative characteristics of dental morphology, such as accessory cusps, shovel-shaped incisors, and cusp patterns. These features are significant because they are frequent in a specific ethnicity and appear as a pattern in a particular demographic. The occurrence and degree of expression of tooth variants have been shown in numerous studies in dental anthropology to have a coherent congenital relevance and may be indicative of ethnicity, providing crucial information for phylogenetic and/or genetic investigations. Within a certain group, several non-metric dental features are consistent and may be a good indicator of their ancestry. Due to the large mineralized content of the tooth, which makes it steadfast, these non-metric dental qualities have the benefit that their morphological characteristics stay steady unless disturbed by extrinsic factors (particularly dental caries, wasting diseases, trauma, and aesthetic treatments). Therefore, these can be effectively employed in racial identification, which is useful in identifying the person through the antemortem dental record.
The mesiopalatal line angle of the maxillary first molar has a little extra cusp called the cusp of Carabelli. Usually seen on the upper first molar, this additional cusp progressively disappears, most likely in the second and third molars. Some people have a complete absence of this cusp, while others have it in different forms. The lingual surfaces of incisors with a shovel-like form have ridges at the lingual margins. In older research, these characteristics were utilized to distinguish between the Caucasian and Mongoloid people. Few dental features have been examined in worldwide research on dental casts, direct clinical evaluation, radiography, and digital photography. Currently, over 135 dental features have been found in the human dental system. Since non-metric qualities' characteristics are simple to see and document, they give us knowledge about genetic and ethnic variations that happen, enabling us to arrange populations following the process of group-specific evolution. However, it should be mentioned that tooth wear and caries might cause some dental features to disappear.
Few studies have been done to fully understand the universality of all the traits in an ethnic population, even though dental non-morphic trait studies were carried out in the past. These characteristics are useful markers for identifying genetic lineages and comprehending population dynamics since they are mainly heritable and resistant to environmental factors. As far as we are aware, this is the first study to thoroughly examine the South Indian population. Since the majority of current information on dental anatomy comes from European and American studies, indigenous studies are urgently needed because their findings may not apply to the South Indian ethnic population, which has its roots in the Dravidian age. By offering researchers a forensic instrument and a window into the complex web of human variation and lineage, the study of non-metric dental features makes a substantial contribution to understanding the subtle interplay between genetics, adaption, and evolution.
Materials & Methods
Study setting
An observational study was conducted with a total of 500 extracted tooth samples that were collected from the tooth repository of Saveetha Dental College and Hospitals. Cochran's formula was used to determine the sample size. A descriptive analysis was performed for the present study.
Statistical analysis
The data was entered into Microsoft Excel, and descriptive analysis was conducted using IBM SPSS Statistics for Windows, Version 17.0 (Released 2008; IBM Corp., Armonk, New York, United States).
Inclusion and exclusion criteria
The extracted teeth were selected based on a few requirements such as non-carious, non-fractured, non-attrited, and non-eroded. Teeth with restorations and dental crowns were also excluded from the study. Twenty non-metric dental traits were considered.
To rule out bias, two observers examined the samples, and for maintenance of record, photographs were taken if any trait was observed (kappa value=100%). The frequency of the trait was also analyzed.
Results
Out of the 20 defined non-morphic dental traits that were assessed in the present study, 14 were found common in the South Indian population. In the present study, 500 teeth were examined. On the examination, the traits observed were cusp of Carabelli (52%), shoveled incisor (8.2%), peg-shaped lateral incisor (7.4%), parastyle (0.8%), multiple parastyle (0.2%), Bushman's canine (0.4%), interruption groove (2.2%), tuberculum intermedium (0.6%), radix entomolaris (39.6%), fusion (2.8%), radiculous premolar (0.2%), dilaceration (58.2%), dens evaginatus (1.2%), and enamel pearl (0.8%).
Conclusions
The present study concludes that three non-morphic dental traits, namely, the cusp of Carabelli, radix entomolaris, and dilaceration, are common in the population observed. There was a moderate to significant positive correlation between the incidence of a few dental traits/anomalies. This data indicates that the majority of the ethnic South Indian population possesses these characteristics, suggesting that they could serve as a useful tool for human identification. This study also exhibits the importance of maintaining antemortem dental records, such that it can help us in human identification of mass fatality, road traffic accidents, and catastrophes.
Republished courtesy of Cureus Journal of Medical Science.