Rapid maxillary expansion treatment increases mid-facial depth in early mixed dentition

OBJECTIVE: To evaluate the effects of rapid maxillary expansion (RME) on mid-facial depth in early mixed dentition and to investigate the relationship between change in mid-facial depth and maxillary sinus and nasal cavity. METHODS: A total of 35 patients with mixed dentition treated with a Haas expander were included in this retrospective study. All patients underwent a cone-beam computed tomography scan before and after rapid maxillary expansion. The Wilcoxon signed-rank test was performed to evaluate the changes in maxillary width, facial depth, maxillary sinus, and nasal cavity volume before and after expansion. Multiple linear regression analysis was applied to evaluate the correlations among them. RESULTS: The hard and soft tissue facial depth in the middle third increased significantly (P < 0.001). The gain on the outer sagittal plane (1.04–1.52 mm) was slightly bigger than that on the inner sagittal plane (0.91–1.30 mm). Maxillary width and nasal cavity width increased 3.42 ± 0.93 mm (P < 0.001) and 2.25 ± 0.77 mm (P < 0.001), respectively, after treatment. A gain was also achieved in both nasal cavity volume (2,236.15 mm(3), P < 0.001) and maxillary sinus volume (1,227.33 mm(3), P < 0.001). Multiple linear regression analysis showed that with the increase in maxillary sinus volume, the facial depth increased as well (B = 0.455–0.683, P < 0.05). Also, statistically significant correlations were found between nasal width and nasal cavity volume (B = 0.384, P < 0.05). CONCLUSION: The depth of the middle third face increased significantly. The facial depth increase was related to the enlargement of maxillary sinus volume, while the nasal cavity volume gain was related to the nasal width increase. This indicated that RME might enhance the fullness of the mid-face and facilitate the patency of nose breathing.