Effect of Maxillomandibular Advancement on Morphology of Velopharyngeal Space

Purpose The objectives of the present study were to assess the changes in upper airway morphology and function in response to advancement of the maxilla and mandible. Patients and Methods Orthognathic surgery was performed. During the surgery, the maxilla and mandible were each advanced as a maxillomandibular advancement simulation. A total of 18 patients with a chief complaint of malocclusion were studied. The distance in jaw advancement and the anteroposterior and left–right diameters of the velopharyngeal space before and after jaw advancement were measured. After the anteroposterior and left–right dilation rates and area enlargement rates were calculated, we compared advancement of the maxilla with that of the mandible. Results Each of the jaw advancements resulted in statistically significant increases in the anteroposterior and left–right diameters of the velopharyngeal space, and the area was significantly enlarged. The anteroposterior dilation rate was significantly greater after advancement of the maxilla, and the left–right dilation rate was significantly greater after advancement of the mandible. The velopharyngeal space area enlargement rate was significantly greater with advancement of the maxilla. Conclusions These data suggest that the mode of dilation of the velopharyngeal space differs between maxillary advancement and mandibular advancement. Jaw advancement affects the soft palate muscles, and the velopharyngeal space is expanded 3-dimensionally by each of those muscles. The difference in the pattern of expansion of the velopharyngeal space was related to differences in the functions of the soft palate muscles.