Background and aim: First permanent molars with poor prognosis may be candidate for timely extraction and replacement by second permanent molars. The presence of third molars should be considered in this treatment plan. The aim of the present study was to evaluate the critical developmental stages of permanent second molar and the status of third molar bud in an Iranian population.

Materials and methods: Four hundred panoramic radiographs of 7 to 11-year-old children were evaluated in this descriptive study. Data were collected from patients’ files and through phone interview with parents. The stage of tooth development in each age group was determined according to the modified Demirjian method. Statistical analysis was performed using Wilcoxon signed Rank test and Chi-Square test.

Results: Stage E (beginning of root formation) in permanent second molars had the highest prevalence among 8 and 9-year-olds in the mandible, and among 9 and 10-year-olds in the maxilla. The predominant stage of development in third molar buds was stage 0 (no evidence of bud formation) in the corresponding age groups. There was no significant difference between boys and girls in terms of developmental stages. Mandibular second and third molars were more advanced than maxillary molars in terms of development, with no gender predilection.

Conclusion: The beginning of calcification in the furcation area of permanent second molar (Stage E, between 8 to 10 years of age) is the most proper stage to coincide with first molar extraction. However, during this time period, the signs of third molar bud formation are not detectable in many individuals, especially in the maxillary arch.