Şeffaf Plak Tekniğinde Ramus Plağı veya Bukkal Shelf Mini Vidası Kullanımının Mandibular Molar Distalizasyonuna Etkisinin FEM ile İncelenmesi

Abstract

ŞANLI, Burak. Investigation of the Effects of Ramus Plate or Buccal Shelf Miniscrew Use on Mandibular Molar Distalization with Clear Aligners Using FEM. Hacettepe University Faculty of Dentistry, Department of Orthodontics, Specialization Thesis, Ankara, 2026. This study compared the initial biomechanical responses of ramus plate, buccal shelf miniscrew, and Class III elastic mechanics combined with metal buttons or precision cuts during mandibular total arch distalization with clear aligners. Six finite element models were generated from the CBCT data of a Class III patient suitable for camouflage treatment. Forces of 300 gf and 170.1 gf were applied in the skeletal anchorage and Class III elastic models, respectively. Tooth displacements, periodontal ligament and clear aligner stresses, aligner deformation, anchorage responses, and surrounding bone stresses were evaluated. In all models, mandibular crowns displaced posteriorly and root apices anteriorly; distal tipping occurred in posterior teeth and lingual crown tipping in incisors. Molar posterior displacement was greatest in the ramus plate models, lower in the buccal shelf miniscrew models, and lowest in the Class III elastic models. In all models, total displacement was concentrated in the canine–first premolar region and decreased posteriorly. In the skeletal anchorage models, precision cuts reduced canine periodontal ligament stress, shifted the maximum stress to the first premolar, and increased clear aligner stress and deformation in the canine region. In the ramus plate models, stress increased toward the fixation region and displacement toward the free end, whereas peak stress in the buccal shelf miniscrew models occurred at the screw head–threaded body transition. Principal stresses around the anchorage components were greater in cortical than trabecular bone. The findings indicate that the initial biomechanics are influenced by the anchorage system, force magnitude and direction, and force-transfer method.