Clear aligner treatment in adult patients with class III malocclusion: lower distalization and class III elastics vs class III elastics alone - a RCT.

Objectives: to analyze the effects of clear aligner treatment in adult patients with moderate Class III malocclusion, comparing the lower molar distalization and Class III elastics protocol with the application of Class III elastics alone.

Null hypothesis: There is no significant difference between lower molar distalization and the use of Class III elastics alone in the correction of Class III disharmony.

Trial design: Two-arm, parallel-group, randomized controlled trial with a 1:1 allocation ratio.

Participants: 31 adult patients with moderate Class III malocclusion were blindly assigned into two groups.

Interventions: Group 1 (7 f, 8 m; 19.1 ± 1.7 y) was treated with lower molar distalization combined with Class III elastics and dento-alveolar expansion. In Group 2 (9 f, 6 m; 19.7 ± 0.1.3 y) all subjects underwent Class III elastics and dento-alveolar expansion.

Primary objective: to evaluate changes in the position of the lower first molars and of the lower incisors at the end of both treatment protocols (i.e. lower molar distalization and Class III elastics vs Class III elastics).

Secondary objectives: to compare sagittal and vertical skeletal changes obtained at the end of treatment with both protocols.

Outcome assessment: a customized cephalometric analysis, including 16 dento-skeletal variables, was performed before (T0) and at the end of treatment (T1) with an average time interval of about 24 +/- 6 months.

Randomization: randomization sequence was generated with a 1:1 allocation ratio.

Blinding: cephalometric analysis and statistical comparisons were conducted by blinded operators.

Results: 30 patients completed treatment and were included in the final analysis (1 drop-out in Group 2). Group 1 revealed a significant improvement in vertical and sagittal position of both molars and incisors compared to Group 2 (respectively L6-MP, -2.8 mm and -0.6 mm; L6^MP, -0.7° and -2.5°, L6 crown-CoGo, -1.4 mm and -0.2 mm; L6 apex-CoGo, -3.3 mm and -1.5 mm; L1 crown-CoGo, -2.9 mm and + 1.9 mm; L1 apex- CoGo -1.7 mm and + 2.6 mm). Both groups showed a significant increase in upper incisor inclination (Group 1, + 2°; Group 2, + 2.7°), overjet (Group 1, + 1.6 mm; Group 2; + 1.3 mm), and overbite (Group 1, + 1.3 mm; Group 2; + 1.1 mm).

Conclusions: The lower molar distalization protocol combined with Class III elastics allowed a more significant improvement in occlusal relationships in the treatment of Class III malocclusion in adult patients, compared to a protocol that involves the use of intermaxillary elastics alone.

Trial registration number: ClinicalTrials.gov NCT06859606.