Surgically assisted versus nonsurgical skeletally anchored maxillary expansion: a retrospective comparative study of dentoalveolar effects using 3D digital models

Background Skeletally anchored maxillary expansion may be performed with or without surgical assistance in adults. However, the effect of surgical assistance on the geometric pattern of arch expansion and dentoalveolar side effects remains uncertain. This study compared surgically assisted and nonsurgical maxillary expansion using the MICRO-4 appliance. Methods 90 patients were included, 45 treated with surgically assisted skeletally anchored maxillary expansion and 45 with nonsurgical skeletally anchored maxillary expansion. Pre- and post-treatment intraoral scans were digitally analysed. The primary outcome was the V-shaped arch opening in the horizontal plane; the secondary outcome was buccal rolling of the upper premolars and molars. Statistical analyses included the Shapiro–Wilk test, Welch’s t-test, and Mann–Whitney U test, with \:α\:=0.05 . Results No statistically significant between-group differences were observed in V-value (Welch’s t -test, p = 0.785), premolar buccal rolling (Mann–Whitney U -test, p = 0.815), or molar buccal rolling (Mann–Whitney U -test, p = 0.145). Both groups showed a fan-shaped expansion pattern with minimal buccal rolling. Conclusions Surgically assisted and nonsurgical expansion showed no statistically significant difference in arch expansion geometry or measured dental side effects in this population. Further investigations including post-expansion treatment and long-term follow-up are needed to validate these findings. Trial registration clinicaltrials.gov, NCT07383376, Retrospectively registered on 26 January 2026.