Effects of combined orthodontic-orthognathic treatment for class II and III correction on posterior airway space : Comparison of mono- and bignathic osteotomies.

Objectives: Comparison of treatment effects on the posterior airway space (PAS) in patients treated with combined orthodontic-orthognathic surgical treatment.

Methods: Pre- and postsurgical lateral cephalograms of 53 (34 females, 19 males) Caucasian patients were analyzed using a customized set of measurements. According to malocclusion (Class II or III) and surgical approach (either monognathic or bignathic), patients were allocated into four groups. PAS was assessed from cranial to caudal at six levels (P1-P6). Paired t tests were used for intragroup and t tests for independent samples for intergroup comparisons. Results were considered statistically significant at p < 0.05.

Results: In patients treated for Class II malocclusion, PAS retropalatally (P1 level) almost remained unchanged, whereas measurements at levels P2-P6 showed a mean increase ranging from approximately 2-5.5 mm. Significant changes were most pronounced in monognathic Class II patients (group 1) at levels P2-P4 with mean values ranging from approximately 3.7-5.5 mm. In patients treated for Class III malocclusion (groups 3 and 4), measurements at the P1 level almost remained unchanged in patients who underwent mandibular setback surgery (group 3), whereas the same measurements exhibited significant increase (>6 mm) in patients treated with bignathic surgery (group 4).

Conclusions: Bignathic surgery led to smaller changes of pharyngeal depth in Class II and III patients than monognathic surgery. Alterations of the PAS due to orthognathic surgery should be considered during orthodontic and presurgical treatment planning.