Third Molar Tooth Bud Development Using Historical Panoramic Radiographs

Objectives: To assess the development of third molars in 3 to 18 year olds via panoramic radiographs. To compare development by age, arch and gender.
Methods: With IRB approval, patients ages 3 to 18 years old with panoramic radiographs were selected from dental school digital records. All 3 to 6 year old patients were selected due to the limited numbers. A sample of every 5^th or 10^th patient based on treatment age for 7 to 18 year olds were selected. 499 patients were evaluated. A modified Demirjian’s classification of the stages of third molar development was used: 0 = no tooth structure evident; 1 = crypt visible; 2 = early signs of enamel formation; 3= clear signs of enamel formation with cusp tips prominent but not connected; 4 = considerable enamel formation with cusp tips connected into a thin shell; 5 = solid crown formation present with no root formation evident; 6 = solid crown formation with root formation evident. Data was analyzed via descriptive and inferential statistics (ANOVA) at p<0.05.
Results: The ANOVA showed the developmental stages of third molars were similar in males and females. Arch was significant, p<0.0001. Age was significant, p<0.0001. Crypt evidence and calcification in mandibular arches was evident on average earlier than the maxillary teeth. This can be attributed to the difficulty in detecting the developing tooth crypt in the maxillary arch in the youngest patients included in the study. The average age of the initial crypt formation was 8.2 years with a standard deviation of 1.3. The average age of the initial mineralization was 9.1 years with a standard deviation of 1.1. The average age of the initial root formation was 16.1 years with a standard deviation of 2.2.
Conclusions: Third molar tooth development is highly variable and best determined using radiographs.