Objective:To compare the angular changes in the developing mandibular third molars in both first premolar extraction and nonextraction cases and to determine whether premolar extraction results in a more mesial movement of the mandibular buccal segment and causes favorable rotational changes in the mandibular third molar tilt, which can enhance later eruption of the third molars. Materials and Methods: Pretreatment (T1) and posttreatment (T2) panoramic radiographs were taken of 25 subjects who had been treated by the extraction of all the first premolars and 25 subjects who had been treated with nonextraction. The horizontal reference plane was used to measure 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 Ϯ 5.4 degrees on the left side and 6.3 Ϯ 6.5 degrees on the right side following treatment (T2 Ϫ T1). For the nonextraction group the mean difference was 1.3 Ϯ 4.3 degrees on the left side and 1.7 Ϯ 5.4 degrees on the right side. There was a statistically significant difference between the groups (P ϭ .012 on the right side and P Ͻ .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.

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