Evaluation of Molar Buccolingual Inclination on Digital Models in Untreated Subjects with Near-Normal Occlusion

Objectives: To evaluate the buccolingual inclination of maxillary and mandibular first molars using 3D digital models in adolescents and adults with near-normal occlusion. Material and Methods: Forty-one untreated adults (mean: 41.7 years) and sixteen adolescents (mean: 15.2 years) with near-normal occlusion were selected. Each subject's 3D digital models were imported into Dolphin Imaging software. The coronal cross-section was attained in no more than a 1.2 mm slice, using a section that best included both right and left first molars while both arches were in occlusion. The long axis of each molar was determined by drawing a line from the midpoint between the buccal and lingual cusp tips to the midpoint of the buccolingual width at the cervical region. The inclination angle of each first molar was then measured. Results: Adolescents and adults showed a similar directional trend in maxillary buccal inclination and mandibular lingual inclination of the first molars. The mean buccal inclination for the maxillary molar in adolescents was 9.0° and 9.1° in adults. The mean lingual inclination for the mandibular first molar in adolescents was 14.5° and 15.6° in adults. Conclusions: (1) In near-normal occlusion, measured from 3D digital models, maxillary first molars showed approximately 9° buccal inclination, and the mandibular first molars showed about 15° lingual inclination. (2) Within the limitations of the present sample and measurement protocol, 3D digital models provided reproducible crown-based measurements of first molar buccolingual inclination, with values similar to those previously reported in CBCT-based studies. Direct validation against CBCT measurements in the same subjects and evaluation in patients with transverse discrepancies or post-treatment records are needed before broader diagnostic or outcome-related claims can be made.