Use of the WALA ridge to evaluate mandibular molar inclination measured to American Board of Orthodontics standards

Abstract

ObjectiveEvaluation of mandibular molar inclination provides valuable information to the orthodontist when evaluating posterior functional occlusal relationships, diagnosing and treating transverse skeletal and dental relationships, and assessing the quality of orthodontic treatment finishing. Traditional evaluation methods rely on radiographs or diagnostic dental models. Identification of a clinical anatomic landmark that can be evaluated chairside and reliably produces desired treatment results would prove valuable to the clinician. Materials and MethodsPlaster dental casts of 60 posttreatment patients were evaluated for mandibular molar inclination by American Board of Orthodontics (ABO) Cast-Radiograph evaluation standards and compared with the mandibular anatomic landmark the WALA ridge. ResultsMandibular first molars conforming to ABO standards with a vertical difference in buccal and lingual cusp heights ≤1.0 mm had an average horizontal WALA-facial axis (FA) distance of 2.56 mm, which was significantly smaller than the 3.11 mm found when molars were ABO nonconforming with vertical cusp height differences of >1.0 mm to ≤2.0 mm (P < 0.001). Mandibular first molars with WALA-FA distances of ≤2.5 mm were not significantly more likely to be ABO conforming than those with WALA-FA distances of >2.5 mm. ConclusionsMandibular molars with vertical differences in buccal and lingual cusp heights meeting the ABO standards for inclination have significantly smaller horizontal tooth to mandibular bone distances (WALA-FA).