Correlation between chronological age and developmental status of third molars (A radiographic evaluation)

Determining chronological age of individuals is an investigation key in legal medicine. The aim of this study was radiographic evaluation of correlation between chronological age of Iranian people and developmental status of third molar tooth based on Demirjian staging method. This cross-sectional and diagnostic study was accomplished in Radiology department, Dental School, Shahid Beheshti University of Medical Sciences in Tehran (2004-2005). 350 young adults, 15-25 year-old, attended the study. ID cards and radiographic evaluation were used for data collection. The radiographs were studied by a legal medicine resident and an oral and maxillofacial radiologist. Determining the developmental stages of third molar teeth was based on Demirjian method. Statistical calculations were carried out by Levene, t, Wilcoxon's signed rank, Mann-Whitney, Friedman tests and Kendal correlation coefficients (tau-b). The distribution of different development stages of Demirjian method increased by development of third molars. There was a significant statistical discrepancy between boys and girls for the lower left third molar tooth (P<0.001) males were in a higher development rank. According to Calton system, the relation between Demirjian method and age was average in maxillary third molar teeth and was strong in mandibular third molar teeth. The maxillary third molars were generally in a higher development rank compared to mandibular third molar teeth (Friedman test, X2 = 44.214, P<0.001). Among four molar teeth, only developmental stage of lower left third molar was diagnosed to be effective (R= 0.714, R2 = 0.51, adjusted R2 = 0.507, F = 209.047, P< 0.001). Only stage (H) of Demirjian method that the distal canal is closed can be predicted with %99 precision whether the person will be 18 or above 18 years old.