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

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.

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

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).

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.

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.

No harms were observed.

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