Frequency of Congenitally Missing of Third Molars and its associated changes in 14-25 Year Old Patients in Mashhad Dental School in 2006

Introduction: Third molars have the highest prevalence of congenital missing. Missing or presence of third molars is one of the key factors that can change the orthodontic, pediatric and surgical graft treatment. The aim of this study was to evaluate the frequency and risk factors of congenitally missing of third molars in 14-25 year old patients in Mashhad dental school. Materials & Methods: In this cross-sectional analytical study, panoramic radiographs of 120 14-25 year old patients evaluated in 2006 and the frequency of congenital missing of third molars and risk factors such as gender, hypodontia and family history was checked. The data were analyzed by Mann-Whitney and Wilcoxon tests. Results: 1. Missing of third molars was 11.2 prevalent. No statistical difference was found between male and female. 2. In patients with third molar agenesis, 60 had agenesis in other permanent teeth and 7.5 had anomaly in permanent teeth. 3. In 23.3 of patients with small size of maxilla, third molar agenesis was detected. 4. No statistical difference was found between maxilla & mandible or right & left sides in third molar agenesis. Conclusion: Frequency of congenitally missing of third molar in our society was similar to other societies and a direct relationship was found between either small size of the maxilla, anomaly or agenesis in other teeth, and agenesis of third molar.