Influence of first premolar extraction on mandibular third molar angulation

Objectives: To compare the changes in position of the developing mandibular third molars in both lower first premolar extraction and non extraction cases. Materials and Methods: Pretreatment and post treatment panoramic radiographs were taken of 15 subjects who had been treated by the extraction of the first mandibular premolars and 15 subjects who had been treated with nonextraction. The horizontal reference plane was used to measure and compare the changes in the inclination of the mandibular second molar and the developing third molars. The occlusal plane was used to measure the distance distal to the mandibular second molar. The distances from mesial cusp of mandibular third molar to occlusal plane and from distal cusp to occlusal plane were also measured. Results: The long axes of the mandibular third molar and second molars to horizontal reference plane pre treatment and post treatment had no statistically significant difference between both groups in the values of the angular changes pre and post treatment .The mean differences in the angle values between pre and post treatment for the right side and the left side showed no statistical significance difference between pre and post treatment in the two groups. A significant correlation was found between the two groups regarding the distance distal to the mandibular second molar to the ramus which increased more in the extraction group than in the non extraction group. Conclusion: premolar extractions will not ensure that the third molars will erupt normally or have sufficient space to achieve good alignment.