Comparison of skeletal and dentoalveolar effects of mini-implant-supported twin block versus conventional twin block in treating growing patients with Class II Division 1 malocclusion: a two-arm randomized controlled clinical trial.

BACKGROUND

This randomized controlled trial aimed to evaluate the skeletal and dentoalveolar changes resulting from the functional treatment with mini-implant supported Twin Block (MITB) appliance compared to the conventional Twin Block (TB) appliance in treating skeletal Class II Division 1 malocclusion.

METHODS

A two-arm, parallel-group RCT was conducted at X University from March to September 2021. Forty-four patients with Class II Division 1 malocclusion (ANB 5°-9°, SNB 72°-77°, overjet 5-8 mm) were randomized to receive either MITB (n = 22, experimental group) or TB (n = 22, control group). Randomization was computer-generated, and outcome assessors were blinded. Skeletal and dentoalveolar changes were assessed using lateral cephalometric radiographs before treatment (T0) and at the end of the active treatment phase (T1). Data were analyzed using the Mann-Whitney U test, paired t-test, and independent t-test.

RESULTS

Of the 44 participants randomized, 41 completed the study (23 males, 18 females; mean age 12.05 ± 1.02 years). Both groups showed reduction in maxillary position (SNA) with no significant differences between or within groups. Mandibular advancement (SNB) and skeletal relationship (ANB) improved significantly in both groups, with greater changes in the MITB group (SNB: 3.35° vs. 2.17°, P = 0.004; ANB: -3.76° vs. -2.41°, P = 0.003; Cohen's d = 0.91 vs. Cohen's d = 0.97). The MITB group also showed significantly greater increases in mandibular corpus length (3.47 mm vs. 2.23 mm; P = 0.016; Cohen's d = 0.83), total mandibular length (4.48 mm vs. 3.26 mm; P = 0.049; Cohen's d = 0.66), and mandibular base position (4.01 mm vs. 2.7 mm; P = 0.004; Cohen's d = 0.95). Skeletal discrepancy decreased more in the MITB group (3.71 mm vs. 2.29 mm; P = 0.005; Cohen's d = 0.93). The MITB group also exhibited less lower incisor protrusion (0.73° vs. 3.81°; P < 0.001; Cohen's d = 2.62) and mesial positioning of the mandibular molar (0.13 mm vs. 1.33 mm P < 0.001; Cohen's d = 1.81). Pancherz's analysis revealed 74% skeletal correction of overjet and 82% skeletal correction of molar relationship in the MITB group.

HARMS: Four orthodontic mini-implants out of 42 (9.5%) failed in two patients.

CONCLUSIONS

The mini-implant supported Twin-Block appliance produced greater skeletal correction and reduced dentoalveolar side effects compared to the conventional Twin Block. These results support the use of mini-implants supported Twin Block as a treatment option for Class II Division 1 malocclusion.

TRIAL REGISTRATION: ClinicalTrials.gov, Clinical Trials ID: NCT06403033.