The Three Finite Element Analysis Of The Mandibular First Molar Restoration With Two Implants Support One Crown

Objective: The defect of mandibular first molar is commonly seen in prosthetic dentistry. According to the condition of the residual periodontal tissues, it is important for the dentists to design a reasonable restored method. Until now there are two different ways(one implant support a crown versus two implants support a crown) to restore the mandibular first molar defection. There is no further study for the degree of polymerization of the two implants with a crown restored. Only the length and the width is considered in the research of the three finite element analysis(FEA) of two implants, lacking of comprehensive understanding the stess state of the periodontal tissues of the implants. By CT scaning,the contour of the mandibular jaws and periodontal tissues were obtained and four 3-D reconstructions were accomplished. So the objective of this study was to perform 3-D reconstruction and establish FEA models of the two implants with different degree of polymerization which had a crown restored with the assistance of computer. The auther compared the stress state of the periodontal tissues of the two implants with different degree of polymerization amoung all the 3-D reconstructions under the sress loading to find the better one. The results could provide the theoretical basis of clinical study.Materials and Methods: At the platform of algor/solid, the datas of the jaw and dentition scanned by CT were used to reconstruct 3-D reconstruction models. Four 3-D reconstruction models were made in the base of the cloud atlas which were accomplished by the computer software.Then the models of the mandibular first molar defection were made just as the natural condition with the help of geometric modeling. The software of reconstruction was applied to establish the 3-D finite element models which contained the jaw ,dention, the implants with different degree of polymerization, the periodontal tissues of the implants and a crown above the two implants. And then under the tress loading, the datas of the stress state of the periodontal tissue of the implants were compared to find which degree of polymerization was the best amoung them.Results: The FEM models which included dentition dentures, two implants support a crown and the mandibular jaw bone were obtained. The defection of the mandibular first molar was replaced by two implants. At the load of 100N, the results showed: the the neck of the implants was the stress concentration area and so was the cortical bone. Among the implants with different degree of polymerization, the stess state of implants with 10 degree of polymerization showed better.Conclusion: According to the experiment above, the two implants with degree of polymerization(5 degree and 10 degree) showed better of stress state than the ones with 0 degree of polymerization. It established that the degree of polymerization(10 degree) approximated the root separate angle showed well under the stress load of 100N. The 10 degree of polymerization approximated the root separate angle best. So the two implants with degree of polymerization(10 degree) approximated the root separate angle of natural molar could be a good choice of the first mandibular molar defection restoration.