| Introduction: Morphology of the pharynx affects the volume of airflow and facial growth patterns, the risk of sleep apnea, and swallowing patterns. Since the pharynx is housed in the facial structures, there may well be an association between the two. Evidence to date implies that the type and severity of Class II malocclusion affects the size and shape of the pharynx. Various researchers have classified Class II malocclusions into groups based on size and positioning of the maxilla and mandible, and these groups may exhibit different pharyngeal characteristics. Purpose: This study compares the pharyngeal sizes of Class II, division 1 orthodontic patients with those of Class I patients. This study also mimics Class II malocclusion groups to see whether different Class II types stand out as having distinct pharyngeal dimensions. Methods: This retrospective, cross-sectional study of 131 routine orthodontic patients (71 Class II, 60 Class I; aged 9 to 13) quantified volume and midsagittal area of the pharynx, defined as (A) the nasopharynx (dorsal and cranial to the posterior nasal spine), and (B) the oropharynx (the airway between PNS and the epiglottis), plus (C) the combined dimensions of these two regions. CBCTs were analyzed using Dolphin3D ©. ANCOVA and general linear models were used to test for sex, age, and skeletal class changes. Additionally, Class II patients were separated into groups using cluster analysis based on the following criteria: (1) 11 pharyngeal variables, (2) 15 cephalometric variables, and (3) 4 Class II variables. Results: Airway size and volume increase significantly within each sex with increased age, but growth is significantly faster in boys. There is no statistically significant difference in the size of the oropharynx between Class I and Class II patients. By the time the 71 Class II patients were separated into groups using cluster analysis, the group sample sizes were too small to find any clinically relevant differences in airway size. The minimum oropharyngeal constriction occurs inferior to the soft palate in 76% of Class II patients and in 68% of Class I patients. Conclusions: With due caution for the cross- sectional nature of the study, these results show that pharyngeal growth occurs at a linear pace during the key orthodontic ages. Rather than being tubular, the pharynx is broader mediolaterally, which cephalometric studies cannot capture. Generally speaking, there is no difference in size of airway between Class I and Class II patients. |
