Influence of first premolar extraction on mandibular third molar angulation

Objective: To compare the angular changes in the developing mandibular third molars in bothfirst premolar extraction and nonextraction cases and to determine whether premolar extractionresults in a more mesial movement of the mandibular buccal segment and causes favorablerotational changes in the mandibular third molar tilt, which can enhance later eruption of the thirdmolars. Materials and Methods: Pretreatment (T1) and posttreatment (T2) panoramic radiographs weretaken of 25 subjects who had been treated by the extraction of all the first premolars and 25subjects who had been treated with nonextraction. The horizontal reference plane was used tomeasure and compare the changes in the angles of the developing mandibular third molars. Results: The mean uprighting of the mandibular third molars seen in the extraction group was 8.2± 5.4 degrees on the left side and 6.3± 6.5 degrees on the right side following treatment(T2 - T1). For the nonextraction group the mean difference was 1.3± 4.3 degrees on the leftside and 1.7± 5.4 degrees on the right side. There was a statistically significant differencebetween the groups (P = .012 on the right side and P < .001 on the left side). Conclusions: Premolar extractions had a positive influence on the developing third molar angulations. Nonextraction therapy did not have any adverse effects. (Angle Orthod. 2009;79:1143-1148).