ABSTRACT
Age estimation of the children usually is assessed using tooth developmental stages in radiographs. The Demirjian's method is one of them. This study was done with the aim of assessment of the Demirjian's developmental age stages of the permanent mandibular teeth in panoramic radiographs of 6-13 years old patients attended to Radiology Department of Mashhad dental school. In this descriptive cross-sectional study, a sample of 310 orthopantomographs taken from 169 girls and 141 boys between 6 and 13 years old referred to Mashgshad dental school was selected. The chronological age of each child was calculated by subtracting her or his birth date from the date on which the radiograph had been obtained and the developmetal stages of each of the seven left mandibular permanent teeth were recorded using the Demirjian method. Independent-sample t test was applied for comparison of the mean age of different developmental stages in both genders. The mean chronological age of stage G of teeth 32 and 33, stage F of tooth 34 and stages D and F of tooth 35 was different between the two genders [P<0.05]. The mean chronological age of teeth 31, 36 and 37 in both sexes and in different developmental stages showed no statistically significant difference [P>0.05]. The mean ages of different developmental stages of permanent mandibular teeth using the Demirjian method were similar to former studies. Also, the stage of mandibular teeth development was higher in girls than boys with similar chornological ages