The evaluation of the relationship with root resorption in tooth-borne or tissue borne appliances and different screw activation protocols after maxillary expansion via micro computed tomography

The aim of this study is to evaluate the root resorption on upper first premolars after maxillary expansion with different design of appliances and different expansion protocols using micro computed tomography. The study consists of fifty patient who required maxillary expansion and extraction of upper first premolars. Patients were divided into 4 main groups; Hyrax (15 individuals), acrylic bonded (15 individuals), modified acrylic bonded (15 individuals) and mini-implant supported hybrid appliances (5 subjects) were used. Hyrax, acrylic bonded and modified acrylic bonded appliances group were divided into 3 subgroups; the expansion screw activated for Group 1 one activation per day, Group 2 two activation per day and Group 3 two activation per day for one week and followed by one activation per for every other day. For hybrid group, one activation per day was implemented. After expansion was completed, the appliances were stabilizated 12 weeks for retention period. The upper first premolars were extracted. The teeth were scanned with Micro-CT (SkyScan 1172, Belgium) and resorption craters were analyzed by special software (CTAn) for direct volumetric measurements. The hybrid expansion appliances had the lowest volume of root resorption and number of craters (p˂0,001). No significant difference was found among the other group in terms of total root resorption (p˃0,05). It was detected that resorption craters were concentrated on the buccal surface. As a conclusion, all expansion appliances and screw activation protocols that used cause root resortion. However, mini screw supported hybrid appliances leads minimal root resorption after rapid maxillary expansion.