Nasolabial morphological changes following anterior vs. subapical maxillary segmental osteotomy: a comparative study.

Abstract

Objective: To compare the effects of subapical anterior maxillary segmental osteotomy (SAMSO) and anterior maxillary segmental osteotomy (AMSO) on nasolabial morphology using three-dimensional (3D) cephalometric method.

Materials and methods: A total of forty-five cases of maxillary protrusion who underwent AMSO or SAMSO from January 2019 to December 2023 were retrospectively included. Cone-beam computed tomography (CBCT) was taken before and ≥ 1 year after surgery. Eleven distances (nasal height, upper lip protrusion, length of philtrum, etc.) and four angles (nasolabial angle, nasal tip angle, inclination of nasal tip, etc.) were measured on the lateral view, and four distances (width of alae nasi, width of alae nasi, nostril width, etc.) and one angle (alar nasi break angle) were measured on the frontal view. Changes in the anterior maxillary hard-tissue and nasolabial soft-tissue before and after surgery were analyzed. Correlations between hard-tissue movements and nasolabial soft-tissue changes were also evaluated.

Results: Both AMSO and SAMSO achieved significant horizontal posterior displacement of point A and U1, with definite efficacy in correcting maxillary prognathism. Compared with SAMSO, AMSO presented a more obvious vertical impaction of U1, with a vertical decrease of 1.9 ± 1.13 mm (P = 0.002). Both groups exhibited significant retraction of upper lip protrusion, and the retraction amplitude was larger in the AMSO group (5.10 mm vs. 0.05 mm, P = 0.002). The AMSO group showed significant widening of the alar base width and width of the alae nasi, with increases of 2.57 ± 1.95 mm (P < 0.001) and 1.29 ± 1.64 mm (P = 0.01), respectively. In contrast, the SAMSO group showed a significant increase in nasal height and nasal tip angle, with increases of 5.65 ± 6.28 mm (P = 0.04) and 12.63 ± 6.89°(P = 0.001), respectively. Although posterior changes and lingual inclination of the maxillary anterior teeth strongly correlated with posterior changes of the upper lip in both groups, there was a significant correlation between changes of vertical position of the anterior maxilla and changes of width of alar base in the AMSO group.

Conclusion: AMSO and SAMSO can assist patients with maxillary prognathism in reducing upper lip protrusion and enhancing their profiles. AMSO has a more pronounced effect on the sagittal and frontal views of nasal soft tissues, while SAMSO predominantly affects the sagittal view of nasal soft tissue, with less impact on the frontal view.

Clinical trial number: Not applicable.