Evaluation of molar to WALA ridge distance and its relationship with vertical facial type in untreated subjects with normal occlusion.

INTRODUCTION: The objective of this study was to evaluate the relationship between mandibular first molar inclination, Andrews' WALA-facial axis (FA) distance, and vertical skeletal pattern in adolescent and adult samples using cone-beam computed tomography and 3-dimensional intraoral scan data. METHODS: Cone-beam computed tomography and 3-dimensional model data from untreated adolescents (n = 20; mean age, 15.32 years) and adults (n = 50; mean age, 41.13 years) with near-normal occlusion were analyzed. Measurements included WALA-FA distance, buccolingual inclination of the mandibular first molars, and the Frankfort-mandibular plane angle. Statistical tests included t tests and correlation analyses. RESULTS: Adolescents had a significantly greater mean WALA-FA distance (2.85 mm) than adults (2.28 mm; P <0.0001). A significant positive correlation existed between molar inclination and WALA-FA distance in both groups. In adolescents only, a significant negative correlation was found between molar inclination and the Frankfort-mandibular plane angle. Molar inclination (approximately 15° lingual) did not differ significantly between the groups. CONCLUSIONS: In subjects with normal occlusion, WALA-FA distances for the mandibular first molars are not constant; adults have smaller WALA-FA distances than adolescents, and mandibular first molars have a lingual inclination of approximately 15° in both adults and adolescents. Clinicians should consider the natural buccolingual inclination of the teeth and alveolar bone and apply individualized WALA-FA guidelines to support long-term stability and function.