Analysis of the effect of maxillary transverse deficiencies on permanent maxillary first molar rotations using 3D digital models

AIM: The aim of this study was to evaluate the permanent maxillary first molar rotation (PMMR) angles in cases of maxillary transverse skeletal deficiency (MTSD) and to compare them with a control group. MATERIALS AND METHODS: In this study, which included a total of 88 patients (50 females, 38 males, with a mean age of 14.98 ± 2.14 years), consisting of 66 patients with MTSD and 22 patients in the control group, four groups were divided: Group 1 (MTSD without molar crossbite), Group 2 (MTSD with bilateral molar crossbite), Group 3 (MTSD with unilateral (right-sided) molar crossbite), and Group 4 (Control Group). Skeletal deficiencies were evaluated by measuring the interjugular, jugale right (JR), and jugale left (JL) distances on posteroanterior cephalograms (PACs), while occlusal relationships were assessed using 3-dimensional (3D) intraoral models. PMMR angles were measured using the 3D Slicer software on 3D intraoral models with the Ricketts Molar-Cusp Reference Line and the midsagittal reference plane. Statistical significance was set at p < 0.05. RESULTS: The PMMR angles and JR and JL distances of Group 2 were significantly higher, while the interjugular distance was found to be the lowest (p < 0.05). There was no significant difference in the PMMR angles between the Control group and Group 1 (p > 0.05), while the JR and JL distances were significantly smaller in the Control group (p < 0.05). In Group 3, on the crossbite side, both the PMMR and the JR and JL distances were significantly higher than on the non-crossbite side (p < 0.05). A significant positive correlation was found between PMMR angles and JR and JL distances (p < 0.05). CONCLUSION: It was concluded that (i) mesiopalatal PMMRs are observed in the MTSDs with molar crossbite, (ii) molars with normal molar occlusal relationships have normal PMMR angles even in the presence of MTSDs, and (iii) early detection of MTSD enables timely interventions, preventing treatment delays and improving occlusal outcomes, particularly in developing patients, thereby optimizing long-term orthodontic results. CLINICAL RELEVANCE: Considering the differences in PMMR angles between MTSD patients with and without molar crossbite, these findings should be taken into account when designing expansion appliances to achieve molar derotation in these patients.