Stereophotogrammetry facial changes following hyrax-type and differential maxillary expanders: a randomized clinical trial.

Abstract

Background: Rapid maxillary expansion (RME) is a common orthopedic intervention in mixed dentition. Evaluating facial soft tissue changes is important to understand its functional and esthetic implications.

Objective: To compare facial soft tissue changes following RME using the Expander with Differential Opening (EDO) and the Hyrax-type (HT).

Materials and methods: This single- center, two-arm parallel randomized clinical involved twenty-two patients aged 6-11 years with posterior crossbites, who were randomly assigned to two treatment groups. In the EDO group, anterior and posterior screws were activated ½ turn twice a day reaching 10.4 and 7.2 mm, respectively. In the HT group, conventional Hyrax was activated ½ turn twice daily until reaching 7.2 mm. Both appliances were maintained for 6 months. The primary outcome was the change in the nasal base width. Secondary outcomes included five additional facial measurements. Stereophotogrammetry was performed at pre-expansion (T1), immediately post-expansion (T2), and 6 months post-expansion (T3) for both treatment groups. Randomization used a computer-generated 1:1 allocation with sealed opaque envelopes. Although double blinding was not possible, image analyses were blinded to timepoints. Intergroup and interphase changes were analyzed using two-way ANOVA with repeated measures. The comparison of RME groups and the control group was performed using ANOVA and Tukey tests (P < 0.05).

Results: The EDO group consisted of 11 patients (3 males, 8 females), with a mean age of 9.45 years. The HT group included 11 patients (4 males, 7 females) with a mean age of 9.35 years. Both type of expanders increased the nasal base width, with no significant difference between groups. A partial relapse of nasal width was observed during retention in the EDO group. The EDO group showed an increase in intercanthal width after RME. Both expanders showed a similar increase in labial intercommissural width and facial heights after expansion, with stability in the retention period.

Conclusions: Both expanders increased the nasal base width and the labial intercommissural width. The EDO showed a partial relapse of nasal base width during retention. Soft tissues changes after RME in children were negligible with both types of expanders.

Harms: No harms were observed.

Trial registration: This trial protocol was registered by the Brazilian Clinical Trials Registry (ReBEC) under the number: RBR-2pd4s4q.