Evaluation of bone field in the posterior region for mandibular molar distalization in class I and class III patients with different vertical facial dimensions

Aim: Aim of this study is to investigate the bone area in the posterior region, which is important for mandibular molar distalization in skeletal class I and class III individuals with normodivergent and hyperdivergent vertical growth patterns. Material and Method: In this study, cone-beam computed tomography scans of 120 individuals divided into 4 groups as class I normodivergent (Group I), class I hyperdivergent (Group II), class III normodivergent (Group III) and class III hyperdivergent (Group IV). Retromolar space at crown level measurements were performed on CBCT-derived panoramic radiographs and axial slices. Retromolar space at the root level was measured 2mm, 4mm, 6mm, 8mm and 10mm apical to cemento-enamel junction at CBCT axial slices. Results: In all groups, retromolar space at root level was significantly less than the crown level (p<0.05). Retromolar space decreased towards the root apex in all groups and smallest retromolar space was level of MSS10mm in all groups. At any root level, the distal root of the mandibular second molar tooth was in contact with the mandibular inner or outer lingual cortex; 50% in Group I, 46.7% in Group II, 7% in Group III and 7% in Group IV. Conclusion: Retromolar space was in greater class III normodivergent individuals than in class I normodivergent in almost every root level. Retromolar space was greater in class III hyperdivergent individuals than class I hyperdivergent only at MSS10mm level. Panoramic images didn't provide reliable information about contact between root and cortex so CBCT is recommended in severe mandibular molar distalization cases. Key Words: Class III malocclusion, cone beam computed tomography, mandibular molar distalization, retromolar space