Finite element analysis of C-expanders with different vertical vectors of anchor screws

Introduction: C-expanders are tissue-and bone-borne maxillary expanders that are anchored by 6 orthodontic miniscrews, 3 on each side of the palate. The purpose of the study was to investigate the effect of C-expanders on the circummaxillary sutures and bucco-palatal axis of teeth in 3-dimensional finite element analyses when anchor screw vectors are different. Methods: Five expansion models were studied on the basis of the vertical positions of anchor screws on the palate. Anchor screws for models A, B, and C were placed symmetrically at 4 mm, 7 mm, and 15 mm below the cementoenamel junction (CEJ), respectively. Anchor screws for models D and E were placed asymmetrically at 4 mm and 15 mm below CEJ and 7 mm and 15 mm below CEJ, respec-tively. Stress, displacement, and angular changes of the bone and teeth were measured in elastoplastic behavior models using a static-nonlinear simulation in an implicit method. Results: Symmetrical and asymmetrical anchor screw placement with different vertical vectors were compared using finite element analyses on 5 models. Conclusions: Using different vectors of anchor screws for C-expanders does change the pattern of palatal expansion (null hypothesis was rejected). The current investigation presents a promising future of controlled asymmetric skeletal maxillary expansion when asymmetric maxillary architecture needs to be corrected for suc-cessful orthodontic outcomes without involving orthognathic surgeries.