The evaluation of the nasal morphologic changes after bimaxillary surgery in skeletal class III maloccusion by using the superimposition of cone-beam computed tomography (CBCT) volumes

Abstract

Background: The purpose of this study was to evaluate nasal morphologic and maxillary skeletal changes occurring after bimaxillary surgery in skeletal class III patients, using a new method entailing superimposition of cone-beam computed tomography (CBCT) volumes.

Materials & methods: The subjects consisted of 30 adults (15 males and 15 females) who had presented with skeletal class III deformities. The subjects underwent Le Fort I advancement and impaction osteotomy and mandibular setback surgery. For closure of the maxillary vestibular incision, alar cinch suture and V-Y closure were performed. The pre- and post-operative CBCT data were superimposed and evaluated by voxel-by-voxel registration.

Results: After surgery, the nasolabial angle, nasal tip angle, nasal tip inclination and columellar angle showed significant increases (P < 0.01). The nasal tip protrusion and nasal height, meanwhile, had significantly decreased (P < 0.01), and the alar base width had increased (P < 0.01). The columellar length and nostril axis angle also had decreased, but the nostril area did not show any significant change.

Conclusions: After surgery, as the maxilla had been moved upward and forward, the nasal tip was shifted antero-superiorly and the alar base width and nostrils were widened. CBCT superimposition, enabling 3D assessment of nasal morphologic changes, can be an effective tool for simultaneous measurement of skeletal and soft-tissue changes.