Effect Of Stress Of Alveolar Bone Loss Of Double Abutments Of Rigid Fixed Bridge In Deletion Of The First And Second Molar

Objective: The aim of this paper is to provide reasonable theory basis of rigid fixed bridge in deletion of the first and second molar, through establishing the three-dimensional finite element models(FEMs), exploring the stress changes of periodontal membrane of different level horizontal absorption of premolars alveolar bone in vertical and oblique load.Methods: To establish the FEMs by collecting the original CT data through scanning the coincident young woman volunteer and using the three-dimensional reconstruction software of Mimics 8.1 and Ansys 11.0. To simulate the different degree horizontal absorption of abutments alveolar bone and apply vertical and oblique load to the built models, observing the stress changes of the periodontal membrane before and after the absorption.Results: (1) A few of accurate rigid fixed bridge of the lack of first and second molar FEMs with three abutments and the vary degree of absorption of the premolars alveolar bone FEMs were established. (2) After the absorption of the premolars alveolar bone, the stress distribution of periodontal membrane was almost the same with the rough, while the von Mises and the first principal stress were increasing. When the second premolar alveolar bone was absorbed, with the absorption degree increasing, the stress of the first premolar periodontal membrane was larger than the second premolar and the third molar. The stress of the second premolar periodontal membrane was decreasing. The stress of the third molar periodontal membrane was decreasing in vertical load and increasing in oblique load. When the two premolars alveolar bone was absorbed at the same time, with the absorption degree increasing, the stress of premolar periodontal membrane was increasing under the vertical load and decreasing under the oblique load. The stress of the second premolar periodontal membrane was decreasing. The stress of the third molar periodontal membrane were decreasing under the vertical load and increasing under the oblique load. The stress of periodontal membrane under the oblique load was 1 to 6 times than the vertical load. (3) The maximum stress of the first and second premolars concentrated on the mesio-distal neck of periodontal membrane and the maximum stress of the third molar was not obvious under the vertical load. The maximum stress of the first and second premolars concentrated on the buccal and lingual neck of the periodontal membrane and the maximum stress of the third molar concentrated on the neck and apex of the periodontal membrane.Conclusion: The different degrees absorption of the second premolar alveolar bone with the lack of the first and second molar, the stress distribution of periodontal membrane was reasonable and the rigid fixed bridge could be used for a long time with the two premolars and the third molar as abutments. The stress concentrated on abutments periodontal membrane was obvious and the premolars should be chose as abutments carefully when the first premolar was also absorbed. The oblique load had a greater impact on the periodontal membrane of abutments and could change the value and distribution of the stress, which prompted that the tilt force was not good for the rigid fixed bridge and should avoid to be produced.