Digitilized Radiographic Analysis of Coronal Pulp for Age Estimation in Adults using Tooth Coronal Index Method – A Pilot Study

Background: Teeth have become a valuable index to estimate age of an individual in forensic odontology. Although various methods have been reported in forensic literature for age estimation, radiographic methods are simple and require less expertise. Digitalization of panoramic radiographs and intraoral periapical radiographs helps in obtaining the more precise images and accurate measurements. Secondary dentin continuously gets deposited on pulpal surface throughout the life thus reducing the size of the pulp cavity. The Tooth Coronal Index (TCI) method is the indirect assessment of secondary dentin deposition for age estimation. Aim: This study aims to estimate the Tooth Coronal Index of mandibular first molar and its correlation with chronological age to derive a regression equation. Materials


Introduction
Identification of deceased or living individuals is utmost important for any forensic investigation or medico legal cases. In forensic dentistry or odontology, dental tissues are used for estimation of chronological age of individuals [1][2][3] . Although various skeletal remains could be used to estimate age, teeth are more reliable indicators because teeth are more resistant to thermal, chemical or mechanical stimuli and could be preserved for longer time even after death than other skeletal tissues of the body 4-6 .
Various morphologic, histological and biochemical methods have been reported in forensic literature for age estimation with the help of teeth but these methods require tooth extraction and are invasive for living individuals 7,8 . To overcome this limitation, noninvasive radiographic methods have been developed that are simple and require less expertise. The advent of digital radiography has various advantages over the conventional radiographs such as instant image viewing, decrease in radiation exposure, better quality of images, less duration of time, storage and accuracy of measurements. Digitalization of panoramic radiographs and intraoral periapical Vol 13 (1) | April 2021 | https://jfds.org/index.php/jfds Sailaja Joparti, Madala Jaya Kiran, Guttikonda Venkateswara Rao, Yeluri Sivaranjani, Moni Thakur and Katakam Pradeepthi radiographs helps in obtaining more precise images and accurate measurements [9][10][11] .
Progressive modification of the coronal pulp cavity throughout life occurs due to continuous deposition of the secondary dentin 12,13 . Ikeda et al. 14

in 1985 developed
Tooth Coronal Index (TCI) method based on secondary dentin deposition for age estimation from radiographs taken for extracted teeth. The Tooth Coronal Index method is the indirect assessment of secondary dentin deposition, in which the Coronal Pulp Cavity Height (CPCH) was considered as parameter for age estimation.
The present study was conducted with an aim to assess the accuracy of age estimation from TCI of mandibular first molar using digital intraoral periapical radiographs and its correlation with chronological age to derive a regression equation.

Materials and Methods
A total of 50 adults above 20 years of age were selected from the outpatient department of our college. The research protocol was reviewed and approved by the committee of our institution. All the subjects were informed about the purpose and objectives of the study and an informed consent was obtained from all the subjects prior to their inclusion.

Inclusion Criteria
• Subjects above 20 years of age irrespective of sex were included. • Fully erupted mandibular first molar with no defects were included in the study.

Exclusion Criteria:
• Subjects with systemic diseases.

Radiographic Measurements
Detailed case history and date of birth was obtained from enrolled subjects and were sent for RVG examination. Digital intraoral radiographs of mandibular first molar were taken by Kodak RVG 5100 with paralleling angle technique at 70 kVp, 8 mA and exposure time of 0.4 s. The image obtained was analyzed and the measurements were calculated by using Sidexis software. All the measurements were recorded in millimeters.

Statistical Analysis
The data obtained was statistically analyzed for the mean values, Standard Deviation (SD) and p value using statistical package software system (SPSS version 20). Age groups and mean TCI were compared by one way ANOVA. Karl Pearson correlation was done to detect the association between the age and TCI. Simple linear regression was carried out by regressing the TCI score against age. Comparison of chronological age with estimated age was done by student paired t test and P < 0.05 was considered as statistically significant.

Results
Out of 50 subjects, males represented 54%, whereas females represented 46%, with a mean age of 39.12 ± 11.62 years [ Table 1]. Mean TCI was found to be 24.77 ± 6.24 and statistically significant difference was observed when TCI was compared with age (P = 0.001*) [ Table 2]. Statistically insignificant difference was observed when TCI was compared with gender (P = 0.3059) [ Table 3]. A negative correlation exists between TCI of mandibular first molar and age in all studied subjects (r = -0.9976, p = 0.0001*) [ Table 4]. Regression analysis was used for TCI to determine the age (Y) [ Table 5]. The standard error of mean between actual age and estimated age was 0.8050 with statistically insignificant difference (P = 0.9989) [ Table 6]. Scatter plot shows strong correlation between the age and TCI [ Figure 2]. The regression equation for the determination of age (Y) using the TCI score is:

Discussion
Identification of a person is first basis for any forensic investigation or medico legal cases. Age estimation is considered as one of the important parameters for persons identification 2 . According to Edwin Saunders, teeth are more reliable maturity indicators for age estimation than other skeletal tissues because they show low variability from environmental factors, nutritional or endocrine diseases 15 . Secondary dentin continuously get deposited on pulpal cavity throughout the life thus reducing the size of pulp cavity. In 1925, Bodecker reported the relation between secondary dentin deposition and chronological age 16 . Since then, several studies have suggested that dental pulp size decreases with increasing age as a result of continuous secondary dentin deposition, thus indicating that assessment of secondary dentin deposition with the help of pulp tooth volume is the best method to estimate the dental age [17][18][19] . Secondary dentin deposition is not uniform all over the pulpal cavity, i.e., in case of molars, it is more over the roof and floor than walls of the pulpal cavity, thus reducing the height rather than the width of the pulpal cavity 7,15 .
Although various methods have been reported in forensic literature for age estimation, radiographic methods are simple, require less expertise and produce more accurate and precise images [20][21][22] . Gustafson made an earlier attempt to estimate the age based on secondary dentin apposition on periapical radiographs 23 . Later, Kvaal et al. 24 and Cameriere et al. 25 estimated the age on radiographs by measuring pulp/tooth ratio and they observed negative correlation with the chronological age.
Jain S et al. 26 estimated the age of an individual from mandibular premolar and molar by using Tooth Coronal Index method on digital intraoral radiographs. They observed a negative correlation between the real age and TCI. Sharma and Srivastava 11 estimated the age by measuring pulp size of six selected teeth by Kvaal's method on digital intraoral radiographs and they found significant correlation between decreasing pulp size with age 24 .
In the present study, digital intraoral radiographic images were used to determine the age of 50 subjects by calculating the TCI of mandibular first molar. The results showed a statistically significant difference between TCI and age (p < 0.05). A negative correlation exists between TCI and age in all subjects with statistically significant difference (r = -0.9976, p<0.05*). These results are in accordance with the studies done by Veera et al., 7 Drusini et al., 12 Zadzinska et al., 17 Igbigbi et al. 18 and Talabani et al. 19 , thus emphasizing that the TCI values decrease with advancing age.
Further, the present study revealed that there was a statistically insignificant difference when TCI was compared with gender (p > 0.05). Hence, gender specific formula is not needed for age estimation. Agemastu et al. 27 and Igbigbi et al. 18 demonstrated that gender has significant influence on TCI values. They elucidated, that the gender significant difference may be due to influence of estrogen on the formation of secondary dentin 28,29 . According to Hietala et al. 30 and Silvana et al. 31 , the existence of an estrogen receptor in odontoblast of human pulp tissue may be the reason for gender influence on secondary dentin deposition.
Moreover the present study showed that the standard error of mean was 0.8050 with statistically insignificant difference between the actual age and estimated age (p > 0.05). These results were in accordance with the studies done by Veera et al. 7 and Igbibi et al. 18 thus indicating that the TCI of mandibular first molar is more reliable indicator for age estimation. The present study further recommend that forensic odontologists should address applicability of TCI method using digital intraoral periapical radiographs on different teeth and conduct similar studies with larger population.

Conclusion
The Tooth Coronal Index provides more accurate estimation of age and it is a simple, noninvasive, less timeconsuming, reproducible and cost-effective method that could be easily applied without any highly specialized equipment. The results concluded that the TCI values concurrently decreased with progression of age and gender has no influence on TCI values.