Effect of horizontal dimensional malocclusions on smile changes in frontal, lateral, and oblique views before and after orthodontic treatment.

BACKGROUND/PURPOSE: Smile esthetics are an important aspect of orthodontic treatment; however, most studies have focused on frontal views. This study examines how horizontal skeletal and dental changes impact smiles from frontal, lateral, and oblique views before and after treatment. MATERIALS AND METHODS: This retrospective study analyzed lateral cephalometric X-rays from orthodontic patients grouped by ANB (I: ≤0°, II: 0-4°, III: ≥4°) and overjet (A: ≤0 mm, B: 0-4 mm, C: 4 ≥ mm). A total of 20, 22, and 22 smile parameters were measured in frontal, lateral, and oblique images. ANOVA and Scheffé tests assessed associations between ANB, OJ, and smile parameters. AI machine learning ranked influencing factors. RESULTS: After treatment, group A showed the greatest maxillary incisor display increase in the frontal view. In the oblique view, only smile length and visible maxillary dental length significantly differed among ANB groups. Smile changes were most prominent in the lateral view. In group I, upper lip landmarks moved upward; in group III, they moved downward. AI machine learning ranked upper maxillary incisor display as the key factor in the frontal view and visible maxillary dental length in lateral and oblique views. CONCLUSION: Lateral views show the most smile changes post-orthodontic treatment. ANB influences smile changes more than OJ in lateral and oblique views, while OJ dominates in the frontal view. Class III cases show the most significant changes. Upper incisor display is key in the frontal view, while maxillary dental length dominates laterally and obliquely. Including lateral and oblique data can enhance orthodontic diagnosis accuracy.