The effect of fixed orthodontic treatment with first premolar extraction on mandibular third molars angulation and retromolar space

Introduction: In most orthodontic patients, mandibular 3rd molars are in early stages of calcification, and prediction of eruption status would be difficult during the course of orthodontic treatment. The aim of this study was to evaluate the effect of first premolar extraction with moderate anchorage on angular changes of third mandibular molar after orthodontic treatment. Materials & Methods: Panoramic radiographs of 50 skeletal class I patients with normal facial height were selected. The patients were divided into two groups of extraction and non-extraction treatments. The angle between 2nd and 3rd molars and 3rd molar angle to mandibular plane were evaluated. Space for eruption of 3rd molar and 3rd molar position relative to ramus were evaluated with regard to Pell and Gregory classification. Paired T-test was used to compare the changes after treatments. Results: In both groups, 3rd molar angle relative to mandibular plane was increased after the treatment but the difference was not significant. M2-M3 angle changed during the treatments but it was not significant (P>0.05). The retromolar space had significantly higher amounts in extraction groups after the treatment (P<0.001). In non-extraction group, there was significant increase in stage I of Pell and Gregory classification (P<0.001). In extraction group, counts of patients with no space for eruption of M3M were decreased and the difference was significant (P<0.001). Conclusion: Extraction of premolars did not have any significant positive effect on mandibular 3rd molar angulation but it can increase the posterior space for eruption of wisdom teeth.