Midline correction by asymmetric reciprocal torque: a pilot study.

OBJECTIVE: Can we correct dental midline discrepancies by systematic torque bends on all canines and premolars without extraction and mesiodistal tooth movement?

PATIENTS AND METHODS: Eight orthodontic patients (4 males, 4 emales, mean age 31 years) presented a dental midline discrepancy of 2-4 mm, moderate deviation of the chin, no skeletal asymmetry, and a horizontal orientation of the occlusal plane in the frontal aspect. On the side where the mandible was shifted medially, asymmetric torque bends moved the antagonist canine and both premolar crowns buccally, while palatal crown torque was used on the maxillary canine and premolars on the other side. Lingual crown torque corrected the medially shifted canine and premolars in the mandibular dental arch, and buccal crown torque the laterally shifted lower canine and premolars.

RESULTS: On average, torque effects altered the canine guidance by 6.5 ± 4.7°, the first premolar guidance by 7 ± 4.1°, and the second premolar guidance by 6.3 ± 3.7°. Correction of the dental midline shift averaged 1.6 ± 0.8 mm after the torque, and eliminated the midline discrepancy completely (n = 2) or partly (n = 6).

CONCLUSION: In this pilot study, asymmetric reciprocal torque represented a treatment option for midline corrections of approximately 2-4 mm and improvement in the chin position without mesiodistal tooth movement or extraction.