Three-dimensional Finite Element Analysis Of Short Root Teeth In Different Ways Of Movement

Objectives:The maxillary central incisors with different ratios of crown-to-root ratio were used to compare the stress distribution of the root and periodontal ligament of the maxillary central incisors with different crown-to-root ratio under the same load.The maxillary central incisors with short root abnormalities were compared and analyzed.The stress distribution of the root and periodontal ligament under three different movement modes,the specificity of the root and periodontal membrane stress distribution of the short root abnormal tooth is obtained,so as to provide a theoretical basis and scientific guidance for the clinical application of orthodontics.Methods: The newly diagnosed patients who started treatment in the orthodontics department of Lanzhou University Stomatological Hospital in October 2017 were 18-30 years old.The anatomy of the maxillary central incisor was basically normal,no history of trauma,no sputum,no root canal treatment.History,no history of orthodontics,periodontal tissue health.According to the modified Lind method,the crown-root ratio of the maxillary central incisor was initially determined by measuring the radiograph;the crown-to-root ratio was 1:1.6,1:1.3,1: The maxillary central incisors of 1,1:0.7 were scanned by CT respectively to obtain a three-dimensional reconstruction model.The different crown roots were introduced into the ABAQUS than the maxillary central incisor model.The periodontal membrane was obtained by Boolean operation.The average thickness of the periodontal membrane was 0.25 mm attached to the root surface.At the same time,the cylindrical alveolar bone was established and assembled to include different crown roots.A three-dimensional finite element model of the maxillary central incisor,periodontal ligament,and alveolar bone.The overall movement,tilting movement and indentation movement were simulated.The stress distribution of the root and periodontal ligament of the maxillary central incisors with different crown-to-root ratios under different loads was compared and analyzed.Results: 1.The stress distribution of the root and periodontal ligament of the maxillary central incisors with different crown-to-root ratios was similar under the same load,but the ratio of crown to root was 1:0.7.The periodontal membrane stress of the incisors was higher than other.test group.2.When the maxillary central incisors of the same crown-to-root ratio are moved in threedifferent ways,the stress and distribution of the root and periodontal ligament are different,and the periodontal ligament and root stress distribution are uniform during the whole movement,while tilting movement The periodontal membrane stress is concentrated at the alveolar crest and the contralateral apex.The stress distribution is similar to the oblique movement when the depression is moving,and is distributed on the lateral side of the root lip.The stress of the periodontal membrane and the root is the largest when the three movement modes are inclined.3.When the 1N orthodontic force is applied to the incisors in the 1:0.7 short root group for three kinds of movement,the periodontal membrane stress distribution and the maximum stress value are within the normal range.Conclusions:Under the same load,the periodontal membrane stress of the short root teeth is larger than that of the normal root,and the tooth neck and apical area are the stress concentration areas.Under the light force,the stress distribution of the short root teeth is not too concentrated,and the maximum stress value is In the normal range.It is indicated that short root teeth are not contraindications for orthodontic treatment.Reducing the value of orthodontic force can reduce stress concentration and reduce the risk of root resorption.