مقایسه تغییرات زاویه مولر سوم مندیبل در درمان‌های ارتودنسی با و یا بدون کشیدن پرمولر اول یا دوم

Objective: Extraction of premolars is believed to affect the eruption of third molars. This comparative study aimed to assess the change in angulation of third molars following first/second premolar extraction versus non-extraction orthodontic treatments. Methods: This historical cohort study was conducted on patients assigned to three treatment groups: extraction of mandibular first premolars (group A), extraction of mandibular second premolars (group B) and non-extraction orthodontic treatment (group C). Each group included 30 third molars. Patients were in the age range of 11-19 years and the third molars were in Nolla’s6-8 stage of tooth development. Pre- and post-treatment panoramic radiographs were analyzed. Results: The angle between the long axis of the mandibular third molar and mandibular plane increased by 7±2.2° in group A and 5.2°in group B and the increase in both groups was statistically significant (P<0.05). Angular changes in group C were not statistically significant (P>0.05). The angle between the long axes of mandibular first and third molars decreased by 6.83±0.3° in group A. This reduction was statistically significant (P<0.05). Conclusion: In extraction orthodontic treatments (versus non-extraction treatments), mandibular third molars tend to straighten up and become upright so the risk of their impaction may be decreased.