Stress Distribution Comparison of Bone-Borne and Tooth-Borne Devices in SARME

Objectives: To compare the different stress distribution of craniofacial complex between bone-borne and tooth-borne devices in surgical assisted rapid maxillary expansion (SARME). Methods: A line frame model of a 22-year-old normal volunteer's craniofacial complex was created by Surfacer software 10.0 (SDRC Inc., USA) using data from spiral computed tomographic scanning and was imported into ANSYS MULTIPHYSICS 10.0 (ANSYS, USA) to create three-dimensional finite element model (FEM) which consisted of 143,656 elements, 233261 nodes. Two different FEMs of the craniofacial complex using bone-borne (Model 1) and tooth-borne devices (Model 2) were generated separately. Le Fort I and midpalatal osteotomies were performed on both models. In each FEM model, von-Mises stresses were measured and analyzed at 20 different anatomical structures of the craniofacial complex with the 0.5mm transversal maxillary expansion (TME). Results: The maximum stresses of Model 1 located at bilateral palatal sides of the alveolar bones in the premolar and molar regions. The maximum stresses of Model 2 appeared in the dental cervix of two anchored teeth , the first premolar and the first molar and their corresponding periodontal tissues. By the comparison of the stresses in upper and middle face between the two models, the results clearly showed that the stress level induced by the bone-borne device was much higher than that of the tooth-borne device. Conclusions: It is suggested that the bone-borne device might be used for SARME instead of the tooth-borne device in the patients having compromised condition in the anchored teeth and their periodontal tissues to avoid various kinds of dental complications caused by the tooth-borne device. However, the bone-borne device could produce higher stress in the upper and middle face compared with the tooth-borne device to which should be paid attention by the clinicians.