Changes in the third palatal rugae after rapid maxillary expansion: pilot study

To evaluate and compare transversal changes in third palatal rugae after rapid maxillary expansion with tooth-borne and hybrid (tooth-bone) borne appliances. The study sample consisted of 18 subjects (median age 12.6 [9.3 – 16.0], 11 females, 7 males) with transverse maxillary constriction, treated with tooth-borne (Group 1) and hybrid (Group 2) rapid maxillary expansion device. Intraoral scans were taken before and after expansion (median 7.2 months [5.3-9.1]). Distances between medial and lateral aspects of left and right third palatal rugae were measured on the intraoral dental scans. There were a statistically significant increases in the inter-medial and inter-lateral distances of the third palatal rugae after expansion in both groups (p = 0.008). Median values in Group 1 before expansion - inter-medial distance 2.6 mm [interquartile range 1.4], inter-lateral 19.61 mm [4.4], after – inter-medial 3.8 mm [1.4] and inter-lateral 25.3 mm [5.2]. For Group 2 before expansion – inter-medial 3.6 mm [1.4], inter-lateral 19.8 mm [4.5] and after expansion inter-medial 5.8 [2.3], inter-lateral 25.1 mm [3.5]. There were no statistically significant differences between the groups. There was a moderate correlation (r = 0.531, p = 0.023) between the increase in the inter-medial and inter-lateral distances. Intraoral measurements showed similar increases in the inter- medial and inter-lateral distances of the third palatal rugae after maxillary expansion with both expansion appliances.