Comparison of angular changes of third molars in first/second premolar extraction/non extraction orthodontic tretments

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. 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. 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). 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.