Background and Objective: Radiographic evaluation of the mineralization stages of third molars is a valuable and important criterion for age estimation in forensic medicine. The aim of this study was radiographic evaluation of the developmental stages of mandibular third molars based on the Demirjian method and its association with chronological age.

Materials and Methods: In this analytic study, 200 radiographs were selected from panoramic radiographs belonging to referred patients to a private clinic in Zanjan in 2014. According to the images, developmental stages of the mandibular third molars and their correlation with chronological age were determined by SPSS 20 software and Kruskal Wallis and Mann Whitney tests.

Results: 52.3% of patients were female and 47.7% of them were male. Patient age ranged from 15 to 25 years. According to the Kruskal Wallis test, difference between the average age of patients and calcification stages of mandibular third molar on the right and left sides was statistically significant. In other words the average age in both the right and the left sides of the mandible showed significant increase from stages C to H. The Mann Whitney test showed no significant difference in calcification stages (D, E, F, G and H) on the right and left sides. In other words, in each developmental stage, the average age on the right and the left sides was the same. The linear regression test showed that calcification stages on the right side had a correlation with both age and sex but calcification stages on left side had a correlation only with age and not with sex.

Conclusion: Only H developmental stage (in which the apex of roots closes) indicates that the patient is 18 years old or older with an accuracy of 99%.