Clinical effectiveness of cantilever arms in the protraction of mandibular molars with clear aligners: a prospective controlled study.

Abstract

Introduction: Clear aligner technique has been revolutionizing the paradigm of contemporary orthodontic practice. However, protraction of mandibular molars is deemed as one of the most challenging tooth movements with clear aligners. This study aimed to evaluate the clinical effectiveness of cantilever arms in protracting mandibular molars with clear aligners.

Materials and methods: A total of 37 orthodontic aligner patients requiring molar protraction (>4 mm) were enrolled in this prospective study. These participants were allocated into either the control group (N = 19) or the cantilever group (N = 18), resulting in 25 mandibular molars in the control group and 22 molars in the cantilever group. Superimposition of pre- and post-treatment data was performed based on cone-beam computed tomography and intraoral scanning. The differences between the predicted and achieved tooth movements (mesiodistal angulation, buccolingual inclination, and molar protraction distance) were compared. The discrepancies between the predicted and achieved tooth movements (DPA) were determined.

Results: Predicted and achieved tooth movements (mesiodistal angulation, buccolingual inclination and protraction distance) were significantly different for both groups (all P < 0.001), and DPAs of mesiodistal angulation (11.7 ± 4.5 vs. 19.9 ± 4.7; P < 0.0001), buccolingual inclination (21.0 ± 7.2 vs. 33.9 ± 8.9; P < 0.0001) and molar protraction distance (0.8 ± 0.4 vs. 3.6 ± 1.5; P < 0.0001) were significantly smaller in the cantilever group than in the control group. The predictability of molar protraction was significantly higher in the cantilever group (87%) than in the control group (43%) (P < 0.0001).

Conclusions: Integrating the cantilever system into clear aligners can mitigate mesial and lingual tipping of mandibular molars and enhance the predictability of mandibular molar protraction.