Morphological characteristics and soft tissue analysis of the naso-oropharyngeal airway in young adults with skeletal Class II anterior open bite: a CBCT retrospective study

OBJECTIVE: To evaluate the naso-oropharyngeal airway morphology and soft tissue characteristics in adult patients with skeletal Class II anterior open bite (AOB) through cone-beam computed tomography (CBCT) measurements, and to compare these findings with those of patients with skeletal Class II malocclusion and normal overbite. METHODS: One hundred subjects with skeletal Class II malocclusion were divided into two groups: the AOB group (n = 50) with an anterior overbite of less than - 3 mm, and the control group (n = 50) with a normal anterior overbite. The age and sex distributions were matched between the two groups. Three-dimensional reconstruction was performed based on the CBCT data of the patients, and the naso-oropharyngeal airway model was segmented into three parts for volume measurement. Measurements included the cross-sectional area at three anatomical levels, the minimum cross-sectional area, and the transverse and sagittal diameters of the airway at two levels. The height of the pharyngeal airway was also measured. The positions of the hyoid bone and tongue body were evaluated. The length, thickness, and area of the soft palate and tongue body were measured in the mid-sagittal plane. Statistical analyses were conducted using independent samples t-tests, Mann-Whitney U tests, chi-square tests, and multiple linear regression, with P < 0.05 indicating statistically significant differences. RESULTS: Compared to the control group, skeletal Class II AOB patients exhibited narrower nasopharyngeal and oropharyngeal airway spaces and lower minimum cross-sectional area. The cross-section at the inferior border of the tongue base showed a more horizontally elongated elliptical shape in AOB patients. Additionally, the AOB group showed significantly greater tongue length, thickness, and area than the control group. The naso-oropharyngeal airway morphology was significantly influenced by several factors, including sex, soft palate area, tongue area, palatoglossal space volume, and H-C3v. CONCLUSION: In skeletal Class II patients, AOB is associated with a narrower oropharyngeal airway compared to normal overbites. An enlarged soft palate and tongue, alongside abnormal tongue posture, may be the primary causes. Clinically, incorporating airway and soft-tissue assessments into treatment planning is advisable.