Periodontal ligament stress analysis on the anterior teeth during the distal displacement of the upper dentition in using micro-screw

Abstract

Objective \nTo investigate the stress distribution in the periodontal ligament during upper dentition distalization in the use of micro-screw, and provide guidances for the application of retraction hook and rackety chair archwire. \n \n \nMethods \nA 3D finite element model was established by CT, MIMICS and ANSYS workbench software, and the distribution and changing regulation of periodontal ligament stress of anterior teeth in different height (2, 5, 8, 10 mm) of retraction hook and different curvature of rackety chair archwire ( 0, 10, 15, 20 degrees) was studied, in the condition of 2 N orthodontic retraction loading. \n \n \nResults \nThe stress of the periodontal ligament of the upper anterior teeth increased with the increase of the height of the traction hook and the curvature of the rocking chair.When the height of the traction hook was more than 5 mm and the curvature of the rocking chair was more than 15 degrees, the maximum periodontal ligament stress of the upper anterior teeth might be more than 15 kPa, exceeding the safety interval. \n \n \nConclusions \nIn order to avoid increasing the probability of root resorption, the traction hook with height less than 5 mm and the arch wire with curvature less than 15 degrees in rocking chair should be used as far as possible in the clinical orthodontic process. \n \n \nKey words: \nMicro-screw;\xa0Orthodontic;\xa0Three-dimensional finite element;\xa0Periodontal ligament stress