Effects of chincup or facemask therapies on the orofacial airway and hyoid position in Class III subjects.

OBJECTIVE: The purpose of this work was to evaluate orofacial airway dimensions and the position of the hyoid bone related to changes induced by facemask therapy (combined with rapid palatal expansion) or by chincup therapy as compared to an untreated Class III control group.

METHODS: In all, 67 patients with skeletal Class III malocclusion were divided into a facemask group (n = 25; 15 girls and 10 boys), a chincup group (n = 15; 16 girls and 9 boys), and a control group (n=17; 9 girls and 8 boys). Hard- and soft-tissue parameters were analyzed on lateral cephalograms, which were available for all patients and included a baseline radiograph (T1) obtained before treatment and a follow-up radiograph (T2) taken upon completion of active treatment or, in the control group, after a 6-month interval. Statistical analysis was performed at the p ≤ 0.05 level and included a paired-sample t-test, a generalized linear mixed model (GLMM), and a post hoc Tukey test.

RESULTS: In the chincup group, significant changes in the perpendicular distance from the hyoid (H) to the C3-Me line were found compared to the control group (p < 0.05). The facemask group, by contrast, showed significant anteroposterior width increases of the pharynx--as measured at the level of the soft palate (p < 0.001)--as well as significant area increases of the nasopharynx based on its anterior portion (p < 0.001) and on its total area (p < 0.001). Both the chincup and the facemask (combined with rapid palatal expansion) therapies were found to induce clockwise rotational effects on the mandible.

CONCLUSION: Orofacial airway dimensions were enlarged significantly by facemask treatment in comparison with both chincup treatment and with the control group.