Simulation Of Orthodontic Process Of Maxillary Impacted Canine Based On Nanoindentation Test

Impacted maxillary canine is one of the most common malocclusion,influence the function establishment and the beauty of buccal cavity.Previous researches on orthodontic treatment of embedded tooth are mostly focused on orthodontic treatment method.The biomechanical mechanism of periodontal ligament that plays a decisive role in the process of tooth movement is not clear.Currently,there is no individualized treatment plan for different position form maxillary impacted canines in orthodontic treatment.In this thesis,reverse engineering modeling,experimental research,construction of constitutive models,and finite element simulation are combined to provide a theoretical basis for optimizing the clinical treatment of maxillary impacted canines.The Nano-indentation Test is conducted to study the material model of periodontal ligament,the stress response of maxillary impacted canines under different orthodontic forces are analyzed.The specific work is as follows:(1)The CT data of the two cases of maxillary impacted canine labial side and two cases on the palatal side are selected.Through MIMICS and CATIA reverse engineering software,establishing a three-dimensional model for simulation to provide a model support for subsequent finite element simulation of maxillary impacted canine with different shapes,positions and directions.(2)Based on the Nano-indentation Test,the biomechanical properties of periodontal ligament are discussed.A canine sliced specimen of the same middle-aged man is used to go on three groups of Nano-indentation Test.The force and displacement curves of periodontal ligament under loading,holding and unloading conditions are obtained.Through the analysis of the test data in unloading condition,it has found that periodontal membranes show obvious non-linear hyper elastic material properties,according with the Ogden's third-order hyperelastic model.Through the analysis of the test data in holding condition,it has found that periodontal membrane has obvious viscoelastic properties,according with the Zener viscoelastic model.(3)Using the finite element simulation software,the stress responses of maxillary embedded canines in different shapes,positions and directions are compared in periodontal tissues under clinical traction.The simulation results of the four sets of finite element models are compared.Under the action of orthodontic force,the internal and external surfaces of periodontal ligament all have stress changes,and the stress is concentrated on the buccal alveolar ridge area of periodontal ligament.The size of the impacted canines in the labial or palatal side is independent of the left and right positions during the orthodontic treatment.Whether the left side or the right side is embedded in the canine,the labial embedded ambush has smaller equivalent stress value than the palatine ambushed canine,and the load that can be borne is large.