3D Evaluation of Torque Expression in Maxillary Incisors: Influence of Crown Shape and Collum Angle

Aim: To evaluate the influence of crown morphology and collum angle of maxillary incisors on torque expression at common bracket-bonding landmarks using cone-beam computed tomography (CBCT). Methods: Twenty CBCT scans of individuals aged 18–27 years were analyzed. For each central and lateral incisor, the height of maximum labial contour (HMC), height of the labial anatomic (LA) point, collum angle (CA), and alpha angle at both HMC (αc) and LA (αLA) were measured. Stone casts confirmed LA points. Independent and paired t-tests assessed inter- and intra-tooth differences (α = 0.05). Results: The HMC was located 2.6 ± 0.3 mm (centrals) and 1.3 ± 0.5 mm (laterals) incisal to the LA point (p < 0.001). LA-point bracket placement reduced torque by 6.9° (centrals) and 5.7° (laterals). Conclusion: The LA point underestimates the true height of contour, potentially compromising torque delivery. CBCT-guided crown morphology analysis may improve bracket positioning in fixed and aligner treatments.