Short-term and long-term effects of rapid maxillary expansion on the nasal soft and hard tissue: A cone beam computed tomography study

Objectives: To evaluate nasal soft and hard tissue changes immediately post-rapid maxillary expansion (RME) and to assess the stability of these changes using cone beam computed tomography (CBCT). Materials and Methods: A total of 35 treatment group (TG) patients (18 girls, 17 boys; 9.39 +/- 1.4) had a pre-RME CBCT and a post-RME CBCT approximately 66 days after expansion, and 25 patients had a follow-up CBCT 2.84 years later. A total of 28 control group (CG; no RME) patients (16 girls, 12 boys; 8.81 +/- 1.6) had an initial CBCT and a CBCT an average of 2.25 years later. Soft and hard tissue nasal landmarks were measured in transverse, sagittal, and coronal planes of space on CBCT scans. Differences within the same group were evaluated by paired t-tests or Wilcoxon signed-rank tests. Long-term comparisons between TG and CG were evaluated by independent-sample t-tests or Wilcoxon rank-sum tests. Results: Immediately post-RME, there were statistically significant mean increases of 1.6 mm of alar base width, 1.77 mm of pyriform height, and 3.57 mm of pyriform width (P < .05). CG showed the significant increases over 2.25 years (P < .001). Compared with CG, the long-term evaluation of TG demonstrated only pyriform height and pyriform width showed a statistically significant difference (P < .01). Conclusions: Although RME produced some significant increase on the nasal soft tissue immediately after expansion, it regressed to the mean of normal growth and development over time. However, long-term evaluation of TG compared with CG showed only pyriform height and pyriform width to be affected by RME.