Intra-jaw versus inter-jaw mini-implant anchored total maxillary arch distalization compared with extraction-based en-masse retraction in adult class II division 1 malocclusion patients: A randomized controlled trial

BACKGROUND: This study aimed to compare the efficacy of intra-jaw and inter-jaw mini-implant-anchored total-maxillary-arch distalization (TMAD) versus premolar extraction for treating Class II Division 1 malocclusion. METHODS: This randomized parallel-group controlled trial included Forty-one patients with Class II Division 1 malocclusion aged between 16 and 30 years were randomly assigned in a 1:1:1 allocation ratio to three groups: intra-jaw TMAD (buccal TADs between U5 and U6; mean age±SD: 22.0±3.7 years), inter-jaw TMAD (skeletally anchored Class II elastics with TADs between L6 and L7; mean age±SD: 19.0±2.6 years), and a control group (premolar extraction with alveolar TADs between U5 and U6; mean age±SD: 21.4±2.7 years). Dentoalveolar, skeletal, and soft-tissue changes were evaluated using dental casts and cephalograms before treatment (T0), at the end of the alignment and levelling phase (T1), and at the end of active treatment (achieving Class I canine relationship with normal overjet; T2. Block randomization and outcome assessor blinding were employed. Statistical analysis was performed using SPSS software. Comparisons between groups and within groups were performed using ANOVA or non-parametric equivalents, followed by appropriate post-hoc tests with Bonferroni correction when required. RESULTS: Forty-one patients completed the study. Intra-Jaw TMAD, Inter-Jaw TMAD, and extraction treatments showed significant overjet reduction (4.1±0.6, 4.1±0.7, 4.6±1 respectively) and canine correction (3.7±0.9, 3.5±1.1, 4±0.8 respectively) with no significant intergroup differences. However, palatal incisor tipping was significantly lower in the intra-jaw group (5.2̊±1.8) compared to the inter-jaw (8̊±2.6) and control (11̊±2.8) groups. Skeletally, TMAD groups exhibited slight mandibular downward rotation, while the control group showed minor forward rotation. The maxillary-mandibular plane angle (MM) increased in intra-jaw and inter-jaw TMAD groups (1̊±0.7, 1.5̊±0.7 with P-values of 0.001,<0.001, respectively) but decreased in the control (1̊±0.8, P=0.04). The control group showed a more pronounced nasolabial angle increase (12.5̊±3.8) compared to intra-jaw and inter-jaw TMAD groups (8.5̊±2.6, 10̊±1.6, with P-values<0.001). CONCLUSIONS: Both TMAD methods are effective alternatives to extraction-based treatment. Intra-jaw TMAD better preserved anterior torque and occlusal plane stability. While extraction treatment produced greater soft tissue changes and reduced intermolar width, TMAD increased width and induced distobuccal molar rotation. TRIAL REGISTRATION: Clinical Trials.gov (Identifier: NCT04814173). Registered on the 20th of May 2022.