ORIGINAL ARTICLE Year : 2019  Volume : 8  Issue : 3  Page : 192197 Age estimation using pulp/tooth area ratio of permanent mandibular first premolar Shravya Ravipati^{1}, Venkateswar Rao Guttikonda^{2}, ^{1} Oral Pathology and Microbiology, Sri Balaji Dental College, Hyderabad, Telangana, India ^{2} Oral Pathology and Microbiology, Mamata Dental College and Hospital, Khammam, Telangana, India Correspondence Address: Background and Objectives: This study was done to estimate age using pulp/tooth area ratio (PTR) of permanent left mandibular first premolar on digital orthopantamograph (OPG) with a commercially available software. The estimated age was compared with chronological age of all subjects in different age groups and also in male and female subjects. Materials and Methods: 200 patients of differing ages visiting the outpatient department of our dental hospital were included as study subjects. The digital OPGs were imported to AutoCAD, commercial (Computer Aided Design) software program developed by Autodesk and then the PTR was derived. The estimated age was calculated using linear regression equation and then compared statistically. Results: Age was calculated using linear regression analysis. The results revealed decreased PTR with an increase in age. Application of this formula gave a standard error of 8.586 years. The effect of gender showed low correlation between PTR and age. Analysis of variance test was used to compare chronological and estimated ages in all three age groups and it was found to be closely related to each other. Interpretation and Conclusion: This study confirms a superior age estimation ability of the formula developed, inferring that customized formulas developed for the local population are better suited for age estimation.
Introduction Age estimation of an individual whether living or dead is an intimidating task in forensic investigations. It helps in both civil and criminal cases and most importantly establishes a profile of a dead person. Dental age estimation is based on morphological, histological, biochemical, and radiological assessment of teeth.[1] Teeth are the hardest structures of human body as they are resistant to external influences as well as mechanical, chemical, and thermal insults, and hence less susceptible to nutritional, hormonal, and pathological changes. Dental age prediction in adults is usually accomplished using a number of methods but most notable are the noninvasive, nondestructive methods.[2] Subsequently, a number of studies were put forward in an attempt to either refine the technique or propose new ones, for example, Johanson[3] modified Gustafson's method. Dental findings assessed by radiography are an important source of information in forensic odontological age determination as they are simple, nondestructive, and reliable method, and most importantly can be used in dead persons and in skeletal remains. Traditionally, radiographic films were used for age estimation, but application of digital radiography in forensic odontology has a number of advantages such as reduced radiation exposure, ability to use image analysis tools and software, transmit images electronically, and a higher shelf life.[4] Cameriere et al. put forth a method for age estimation which measured the tooth in two dimensions specifically the tooth area and pulp area.[2] Hence, the purpose of this study is to evaluate a human age estimation method based on pulp/tooth area ratio (PTR) of permanent mandibular left first premolar using digital orthopantamographs (OPGs). Materials and Methods A total of 200 patients of Indian origin (114 males and 86 females) who had visited the outpatient department of our dental hospital for consultation and diagnosis were included as study subjects [Table 1]. Subject's ages ranged from 10 to 70 years, and they were equally distributed across three different age groups with an interval of 20 years. Digital OPGs taken using ORTHOPHOS XG 5 (Sirona Dental Company, Germany) of 200 patients during a span of 8 months were collected from the past records. The tooth selected for the study was permanent mandibular left first premolar as these teeth are less readily damaged by direct heat or traumatic force, since they are covered by soft tissue of the cheek. In addition, they are less likely than the posterior teeth to suffer wear as a result of particular work and are not easily lost in dry skull material as molar tends to be. Most importantly, they are single rooted teeth with a large pulp area, and hence easy for analysis [Figure 1] and [Figure 2]. Permanent mandibular left first premolars which are fully erupted into the oral cavity and with fully formed roots visual on the OPGs were included in the study.{Table 1}{Figure 1}{Figure 2} Teeth with any pathology such as caries, periodontitis, or periapical lesions which would alter the surface area of the tooth, malaligned, rotated teeth, or premolars with any prosthetic fittings did not facilitate the selection procedure. The radiographic images were saved as highresolution JPEG files on desktop computer and imported to Adobe Photoshop CS2 editing software program (2008; Adobe Systems Inc., Mountain View, CA, USA). A minimum of 10 horizontal lines were marked on the tooth using Photoshop's inbuilt line tool. The lines were marked at the cusp tip at two levels corresponding to the maximum curvature of crown on the mesial side, distal side, and the cementoenamel junction. The resultant images were opened in AutoCAD software program (Autodesk Inc., San Rafael, CA, USA; 2008 version) and the morphological variables were derived, that is, the PTR [Figure 3].{Figure 3} Statistical analysis Age was calculated using the linear regression analysis for permanent mandibular left first premolar using (SPSS 10.0 version; SPSS Inc., Chicago, IL, USA). The regression equation was then applied to the sample (n = 200) to ascertain whether the populationspecific formula enhanced age prediction, and the radiographs were then decoded and the actual age was ascertained. The mean absolute error (MAE) was calculated which depicts the average magnitude of error in age prediction. Results Morphological variables for all 114 males and 86 females in different age groups showed all the variables to be significantly correlated with age. PTR ranged from 0.018 to 0.20. Comparing the chronological age with a PTR with R2 value of 0.635, respectively, showed decreased PTR with the increase in age [Figure 4]. The regression coefficients of all morphological variables were highly significant (P = 0.000).{Figure 4} Derived formula: age = 55.465 200.537 × PTR where PTR is the pulp/tooth area ratio. Application of this formula yielded a standard error of ±8.586 years of chronological age. The R2 value between the two variables, that is, chronological and estimated ages, was 0.635 according to analysis of variance (ANOVA) test which indicated that the two variables are linearly related to each other producing “acceptable” age estimates (error ttest (twotail) was done to compare the chronological and estimated ages in all three age groups and was found to be closely related to each other and statistically significant in the age groups of 10–30 years and >50 years of age as shown in [Table 4] and [Figure 6].{Table 2}{Figure 5}{Table 3}{Table 4}{Figure 6} Discussion Age estimation forms an important aspect in establishing a profile in forensic investigations.[5] Assessment of PTR, an indirect quantification of secondary dentine deposition,[2],[6] has proved to be a robust age indicator and can be used as age indicator in forensic applications.[1] Various linear measurement ratios, area ratios, and even volume ratios of pulp and tooth have been successfully used to estimate age by many authors. Cameriere et al.[4] have demonstrated a radiographic method of age estimation which uses the ratio of pulp area in relation to tooth area from periapical radiographs of canines, and they revealed a linear regression between age and area ratio in canines.[2],[7],[8],[9] Similar methods using PTR in the region of interest on the radiographs have been reported by Itoho[10] and Shinozaki[11] Brkic et al.[12] found that teeth of both jaws are reliable for dental age estimation.[9] Willems et al.[13] suggested that it might be worthwhile to produce a calibrated digital image on the radiograph to be able to perform digital linear measurements which might produce the most accurate measurements.[14] Digital OPGs have advantages which include first and foremost minimal time and ease of repeatability as the image is seen immediately on the computer when compared with traditional radiographs which require developing Xrays.[5] Thus, we endeavoured to use this method in our study which overcomes the need for scanning and digitization of radiographs. Lower left first premolar is less readily damaged by direct heat/traumatic force, than incisors or canines and not as easily lost in dry skull material. Simpler and less diverse root morphology than that exhibited by molar teeth led us to conclude that premolar teeth should have a high potential as a forensic sample for age estimation.[9] The sample size of 200 OPGs was selected in an attempt to increase reliability of the study. The mean values of the PTR by age groups indicated a general inverse relationship between age and the ratio and a steep reduction in older subjects. Regression analysis was done, and the equation was applied to all the three age groups of our 200 samples and the estimated age was derived which was followed by statistical analysis. The correlation between age and PTR of lower first left premolar in our study was found to be statistically significant with a P value of <0.001 and R2 value of 0.635, which means there is not much difference between the estimated age and chronological age. These results are in agreement with studies conducted by Bosmans et al.[15] who used radiographs of maxillary and mandibular incisors dimensions and found that all correlations were significant which are also in line with Fan Yang et al.[16] using conebeam computed tomography for a group of Belgian population.[6] This confirms that estimating the age using PTR is relatively accurate. In a previous study conducted by Cameriere et al.[4] in canines using intraoral periapical Xrays, age estimates were within ±10 years of estimated age with that of chronological age compared with their result. Our study on lower premolar gave an error of ± 8.586 years. On comparing the chronological age and estimated age between male and female subjects, it produced an error of P value < 0.005 revealing not much significant difference between the chronological and estimated ages concluding that gender had no influence on age parallel to Cameriere et al.[17] In comparison between the three age groups, the age could be predicted better in the 10–30 and 51–70 year age groups with high statistical significance. Contrary to our study results, Jeevan et al.[5] and Singaraju and Sharada[7] have reported that age estimation is more accurate in the middle age group (20–45 years). Interpreting the above tables and graphs, a different degree of accuracy can be observed as this study investigated the relationship between age and agerelated changes in PTR and found good correlation between the chronological age and PTR. In the due course of our study, we found that this method of age estimation had certain limitations. It is difficult to obtain accurate measurements in multirooted teeth. Similarly, the curved arch of the jaw projecting onto a flat film contributes to a certain amount of distortion.[7] Although the OPGs are superior to smaller intraoral periapical films, it is generally accepted that a radiographic image of a finite site found on an OPG is less clear than that shown by an intraoral periapical film.[1] Hence, it is quite clear that accuracy and precision are important in assessing age referring to the closeness of a computed value to its true value; any difference found can be attributed to many variables including precision of the method, age distribution of the sample, sample size, and statistical approach used.[14] However, it could be prudent to further increase the number of subjects and derive formulas on a still larger sample and make the age estimation more robust and reliable. As accuracy of age prediction is the closeness of estimated and chronological age consequently, this study showed promising results for dental age estimation in a noninvasive manner using a digital OPG from mandibular premolar to aid the forensic odontologist. It is recommended that populationspecific formulas are more precise and stable age estimates provided the selection criteria are respected and good quality OPGs with clear images are used. Further research modifying the present technique together with expected further improvements in periapical radiography by direct digital radiography may provide an easy and optimized dental age estimation technique. To conclude, even the most powerful modeling technique for forensic age estimation is not accurate enough because of the high variability in the formation of teeth in individuals. Further genetic and ethnic factors must be considered as elements affecting the development of teeth. Declaration of patient consent The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest. References


