Significance of Recording Dental Morphological Features: An Aid in Personal Identification

Introduction

Tooth being the hardest tissue of the human body is known to survive devastating environmental circumstances.^1,2 Hence, Forensic Odontology utilizes the individualistic dental features as the highly reliable parameter to help in detection of human remains.¹ These characteristics gives every individual a unique identity³ and a positive match established by recognition of dental features is well accepted.³ For forensic evaluation and legal implication, the usefulness of unique dental features and their morphological variations is well acknowledged.^4,5 Thus preserving a record of these dental features is of paramount importance.^1,2 The low frequencies of such dental characteristics make them suitable to aid in personal identification cases.⁶ However, only few studies and reports are available that discuss the forensic value of these dental characteristics that can potentially guide to a positive identification.^1,2,6-9 Literature also reveals that such findings are most frequently overlooked by dental professionals.^2,5 Moreover, in contrast to maintenance of every student’s medical record during the admission process, dental findings are not maintained or documented. Hence, the current survey aimed to record these dental morphological features among the professional students of our medical campus and use it as database for human recognition.

Methodology

After obtaining approval from the Institutional ethical committee, the present prospective survey included Medical, Dental and Nursing students of Bharati Vidyapeeth Deemed University Medical Campus, Sangli aged between 18-25 years. Written informed consent was obtained from every participant.

A detailed examination of the oral cavity was done to detect the dental anomalies affecting size, shape, number, position of tooth and non-metric dental crown traits (like cusp of Carabelli, parastyle, protostylid, cusp 6, cusp 7 and five-cusped lower second molar) using mouth mirror and probe. Radiographs were taken and dental cast models were prepared when needed. Subjects with orthodontic treatment, history of syndromes, cleft lip & palate, dental anomalies affecting the structure were excluded from the study. The obtained data was entered in Microsoft excel and descriptive statistics were employed.

Results

A total of 720 students from medical, dental and nursing colleges of our medical campus were included, among which 309 (42.91%) were males and 411 (57.08%) were females. Overall, 13.7% (n=97) of subjects had selected dental traits. Eighty (11.1%) subjects had at least one dental feature examined and 17 (2.36%) presented with additional dental features. Talon’s cusp and cusp of Carabelli were frequently detected traits followed by hyperdontia, cusp 7, peg shaped laterals, hypodontia, microdontia, 5 cusped lower 2^nd molar and macrodontia. The various features observed are shown in figure 1 and 2. The least frequently observed features included parastyle, protostylid, cusp 6 and fusion. The genderwise distribution of various dental features is depicted in table 1. Cusp of Carabelli showed frequent bilateral presence than unilateral (Table 2).

Discussion

The dentition of humans is revolutionizing in form, number, size and the wide variation in these morphological characteristics may not undergo alterations easily.⁸ Hence, the peculiar dental feature may be of major significance in forensic and anthropological context. Every tooth possesses unique characteristics that operate as the basis for identification.^2,10 However, the ignorance by dentists and legal professionals regarding the significance of dental data of these peculiar tooth features in the recognition of deceased in forensics is a matter of concern.

In this survey, 97 (13.47%) subjects presented with some dental feature, while 17 (2.36%) also presented with additional features. The occurrence of the features in Indian population ranged from 1.73% - 36.7%.^11-13 This disparity can be attributed to the variations in the study design, type of population studied, sampling techniques, form of dental traits included and the result of local environment.

Dental anomalies: Being an important category of dental morphological variations, the dental anomalies are a result of interruption in the stages of odontogenesis.¹³ Local as well as systemic factors contribute to these anomalies.¹¹ These anomalies are manifested in relation to the size, number, shape of tooth in the jaws.⁶ Apart from significantly altering the treatment modalities, their presence has a pivotal role in forensics.^3,10

Abnormalities of tooth size mainly includes macrodontia and microdontia, that refers to larger or smaller dentition than normal (outside the usual limit of variation).¹⁴ Localized macrodontia involving few teeth is a frequent observation than diffuse, which is a feature of pineal hyperplasia and pituitary gigantism.¹⁵ We found macrodontia involving maxillary central incisors in four subjects. Upper third molars and lateral incisors frequently show microdontia and its prevalence ranges from 0.8% to 8.4%.¹⁵ A type of microdontia called as peg shaped incisors refers to reduced mesiodistal diameter with convergence towards incisal edge.^11,15 Microdontia accounted for 2.5% (n=18), with a large number of them being peg shaped laterals. The observations of previous studies and the present study signify microdontia to be common than macrodontia indicating the evolutionary reduction of size of the teeth.

Studies have shown that hyperdontia in different populations ranges from 0.1-3.8%.^11,12 We found hyperdontia in 12 (1.7%) individuals, and paramolar was the most common. This finding was in accordance with the results of Guttal et al¹¹ and in contrast to a study by Patil S et al,¹² who found mesiodens as the most common anomaly. Hypodontia was noticed in 10 (1.4%) study subjects with female predominance. Missing lateral incisors in the upper jaw outnumbered other teeth. Previous studies showed varied findings attributable to factors related to genetics and environment.^11,12

The frequent anomaly affecting the shape of teeth seen in the current work was talon’s cusp of maxillary lateral incisors (n=24/3.3%). Talon’s cusp showed predilection for females than males. However, previous studies revealed more of male predilection for this anomaly.¹¹ Based on the amount of cusp formation and extension, Hattab et al had classified it as Talon, Semi talon and Trace talon.16 We observed both semi talon and Talon types in the present study. The least commonly found anomaly was fusion which was observed in only one case. Its prevalence is reported to be 0.2%.⁶ Other anomalies like dens evaginatus, dens invaginatus, gemination and taurodontism and concrescence were excluded in the current study as they require radiographic diagnosis.

Non-metric dental traits: The non-metric dental feature refers to a particular feature like carabelli’s cusp etc.¹⁷ In contrast to metric features, these non-metric features are not influenced by local environment; thus can be employed in the identification of humans.¹⁷ We studied the non-metric features like Carabelli’s cusp, cusp 6, cusp 7, parastyle, protostylid and 5 cusped lower second molar. Carabelli’s cusp first defined by Carabelli in 1842, refers to the well-developed tubercle on the mesiolingual cusp of the maxillary first molar17 and is rarely seen on second or third molars.⁶

The interaction between enamel knot spacing and the period of crown morphogenesis leading to late-forming enamel-knots results in Carabelli’s cusp expression.⁷ An array of evolutionary and functional perspectives have been postulated for Carabelli’s cusp namely, a) as a primitive structure with a tendency to fade away with reduction in molar size in all hominoid evolutionary lines⁸ b) as an adaptation to increase the buccolingual dimension of first molars crown to compensate the evolutionary decrease in the mesiodistal measurements^6,18 and c) as an arrangement to resist excessive biomechanical stress on molars.^6,18 Understanding its clinical, anthropological and forensic significance is crucial.

Studies have revealed its expression to be high in Caucasians and was used to differentiate Asians from Europeans and Africans.⁶ Carabelli’s cusp, the common non-metric trait in our study accounted for 3.2% of cases. However, compared to other studies, this was low. The high estimates in few studies¹⁸ and low in others⁷ suggest a conflicting result regarding the expression of Carabelli’s cusp. The diagnostic criteria, population studied etc may be attributable to this finding.

The frequent bilateral presentation of Carabelli’s cusp is in concurrence with the study conducted by Kamatham R et al.⁸ Our study revealed a male predominance. This is attributed to the more complex nature of crowns in males and greater crown reduction in females during the evolutionary process.⁸ However, sexual dimorphism was evident in studies by Uthaman et al¹ and Kirthiga et al.¹⁸ Hence, gender difference for Carabelli’s cusp is difficult to conclude.

Low occurrence noted for other non-metric features studied in the present survey were cusp 6 (n=2), cusp 7 ( n=12), parastyle ( n=3) , protostylid (n=2) and 5 cusped lower second molar (n=6). Literature implied these accessory cusps to be common in mongoloids and least in Caucasians.⁶ The presence of extra enamel knots (formed outside the inhibitory zones) are responsible for accessory cusps, thus representing “Patterning Cascade model” of cusp development.¹⁹

In general, owing to the frequent findings of microdontia and cusp of Carabelli among our study participants, a trend in reduction of mesiodistal width of teeth can be noted. This may be due to diminishing jaw sizes. The most negligible features found were cusp 6, parastyle and protostyle. In the wider anthropological sense, these above observations must be emphasized while recognizing an individual in the target population. However, future studies including an array of morphological features conducted in a larger sample are necessary.

Conclusion

The findings of the present study necessitates a probabilistic model containing the peculiar dental characteristics to identify individual from the target population for forensic purposes. Recognising an individual on the basis of a particular dental morphological feature is crucial, thus providing a platform to recognize the human diversity of the target population. Also, curriculum amendment that includes Forensic Dentistry as a subject in dentistry is vital. This would further assist in sensitizing the general dentists, dental science graduates and postgraduates towards these dental features and their forensic value. In addition, recording and maintaining the study models of every student at the institutional level should be practiced for any eventuality.

Conflict of Interest

None.