A randomized clinical trial comparing mandibular incisor proclination produced by fixed labial appliances and clear aligners

Objective: To compare the mandibular incisor proclination produced by fixed labial appliances and third generation clear aligners. Materials and Methods: Patients underwent a course of orthodontic treatment using either fixed labial appliances or clear aligners (Invisalign). Mandibular incisor proclination was measured by comparing pretreatment and near-end treatment lateral cephalograms. Eligibility criteria included adult patients with mild mandibular incisor crowding (<4 mm) and Class I skeletal bases (ANB, 14). The main outcome was the cephalometric change in mandibular incisor inclination to the mandibular plane at the end of treatment. Eligible patients picking a sealed opaque envelope, which indicated their group allocation, was used to achieve randomization. Data was analyzed using a Welch two-sample t-test. Results: Forty-four patients (mean age, 26.4 +/- 7.7 years) were randomized in a 1:1 ratio to either the fixed labial appliance or the clear aligner group. Baseline characteristics were similar for both groups: Fixed appliance mean crowding was 2.1 +/- 1.3 mm vs clear aligner mean crowding, 2.5 +/- 1.3 mm; pretreatment mean mandibular incisor inclination for the fixed appliance group was 90.8.1 +/- 5.4 degrees vs 91.6 +/- 6.4 degrees for the clear aligner group. Fixed appliances produced 5.3 +/- 4.3 degrees of mandibular incisor proclination. Clear aligners proclined the mandibular incisors by 3.4 +/- 3.2 degrees. The difference between the two groups was not statistically significant (P >.05). Conclusion: There was no difference in the amount of mandibular incisor proclination produced by clear aligners and fixed labial appliances in mild crowding cases.