Evaluation of the dentoalveolar effects of extra alveolar mini screw assisted mandibular arch distalization in class III maloclusions

Aim: The aim of this study was to evaluate the dentoalveoler effects of mandibular total arch distalization with the help of force applied from buccal shelf screws and changes in the mandibular incisor alveoler bone tissue caused by this force with lateral cephalometric films and CBCT (Cone Beam Computed Tomography) in class III non-growing patients. Materials and Methods: The sample included 22 subjects (15 females and 7 males) with Angle Class III malocclusion who admited to Ege University Faculty of Dentistry, Department of Orthodontics. Our study consists of a single group and Empower 2 (American Orthodontics, California, USA) self-ligating brackets were applied to all individuals. 0,014 HANT, 0,016 HANT, 0,016x0,025 HANT, 0,019x0,025 HANT, 0,019x0,025 stainless steel wires were applied to the individuals respectively. Mini screws were placed at the appointment which 0,019x0,025 stainless steel wire was applied and the distalization force was activated by thermoset elastomeric power chains. Lateral cephalometric films and CBCT images were obtained at the session which the distalization force was initiated (T0) and the session which the distalization force was terminated (T1). Skeletal and soft tissue analyzes on lateral cephalometric images were performed using the Dolphin Imaging Software Version 11.95.08.50 (Dolphin Imaging, California, USA). CBCT recordings were visualized using CS 3D Imaging (Carestream Dental LLC, Atalanta, USA). These images were transferred to Adobe Photoshop CC 2019 20.0.6 (Adobe Inc., California, USA) and measurements were made. Independent sample t-test and Saphiro-Wilk tests were used for statistical analysis. Results: In the skeletal analysis measurements performed on cephalometric film, the only statistically significant value between T0 and T1 periods was Witts appraisal (3,34, p <0,05). In dental measurements, IMPA (10,72°, p <0,05), L1-NB angle (10,41°, p <0,05), L1-NB distance (3,10, p <0,05), Md1-MdOP (6,41°, p <0,05), Md1-Sn (3,75°, p <0,05) values were found to be statistically significant in T0 and T1 periods. Also, palatal plane-occlusal plane angle decreased by 3,54°, mandibular plane-occlusal plane angle increased by 2,78° at the end of treatment and these two changes were statistically significant (p <0,05). In soft tissue analysis, Li-E value decreased by 2,27 mm and Li-S value decreased by 2,03 mm and was found to be statistically significant (p <0,05). According to the CBCT datas taken from the area between the mesial surfaces of the right and left canine teeth of the lower jaw, the bone area was reduced 4,1 ± 5,19 mm2 and this was found to be statistically significant (p <0,05). According to measurements of the length of the lower incisors' root surface contact with the alveolar bone, the length of the contact surface of the each tooth was significantly reduced. (p <0,05). Conclusion: In this study, which examined the dentoalveolar effects of total distalization of the lower dental arch, the inclinations of the lower incisors decreased and the lower occlusal plane was rotated counterclockwise. Treatment mechanics used in this study, were found to be insufficient to prevent the reduction of alveolar bone support surrounding lower incisors. Further comprehensive studies are needed.