Angular and positional changes of the maxillary third molars after orthodontic treatment with different premolar extraction patterns

Objectives: To evaluate the angular and positional changes of the maxillary second (M2) and third molars (M3) after orthodontic premolar extraction treatment according to patient skeletal classification and growth pattern. Materials and Methods: Panoramic radiographs of patients treated with extraction of the first or second premolars (n = 116) and patients treated without extraction (n = 92), taken before orthodontic treatment (T0) and after completion of multibracket appliance therapy (T1) were analyzed. Angle classification, growth pattern, crowding, and incisor inclination were recorded. The palatal (PP) and interorbital planes (IOP) were used as reference lines. Changes in the M3 angulation relative to PP and IOP (T0-T1) within the same group were evaluated with paired t-tests. One-way analysis of variance (ANOVA) and Kruskal-Wallis tests were used for comparisons between the groups. Accordingly, pairwise comparisons were performed with Mann-Whitney U-tests or independent t-tests (P < .05). Results: The M3 angulation related to the PP and the IOP did not differ significantly between the extraction and nonextraction groups. The M2 angulation improved in the premolar extraction group between T0 and T1 (M2/PP, P < .001). According to Archer's classification, the change in the vertical position of M3 differed significantly between the extraction and nonextraction groups (P < .001). Conclusions: The angulation of M3 improved over time regardless of the extraction decision. The vertical eruption pattern of M3 was positively influenced only in the extraction group. M2 became significantly more upright in the orthodontic extraction treatment groups.