Finite Element Analysis Of Mandible Incisor Defect Restored By Telescopic Crowns Retainers

Periodontal disease is one of chiefly reasons of dentition defect. The left teeth with periodontal disease characterize the defect. After restoration, periodontal maintenance and therapy of abutments and left teeth is vital to controlling periodontal disease and longevity of service of restorations. Periodontal disease always causes mandibular incisors and canines defect. Fixed PFM bridge is usually used to restore mandibular incisor defect, but this way is not convenient to clean and check the abutments and adjacent teeth. An another way-PFM bridge fixed by telescopic crowns retainers-can change this. There are plenty of studies about telescope denture as an removable denture. But, compared with fixed denture, how the stress analysis of periodontal tissues is is not clear. This research is to compare the stress analysis of periodontal tissues of different restorations, and give a theoretical support of application of PFM bridge fixed by telescopic crowns retainers.Objective: Establish 3-D finite element models of mandibular incisor defect restored by PFM bridge fixed by telescopic crowns retainers and fixed bridge with different periodontal conditions. Analyze and compare the stress of abutments'periodontal tissues, give a theoretical support of application of PFM bridge fixed by telescopic crowns retainers.Methods: Scan a normal man's lower mandibular field by helical CT, choose proper CT images and get them into BMP format. Input the images of BMP format into medical images reconstruction software to obtain a 3-D figure of the model, use RE software to get the material object. Use finite software to establish 3-D finite element model of mandibular incisor defect restored by fixed denture and three types of PFM bridge fixed by telescopic crowns. Imitate Classâ… alveolar bone loss by decreasing height of alveolar bone and periodontal membrane. Analyze stress distribution of the model with and without periodontal diseases, compare and analyze stress value of abutments'periodontal tissues of PFM bridge fixed by telescopic crowns retainers and fixed bridge.Results:1. Establish 3-D finite element model of mandibular incisor defect restored by fixed denture and three types of PFM bridge fixed by telescopic crowns, which are a. non-buffer-telescopic crowns retainers without friction between first crown and coping crown, b. non-buffer-telescopic crowns retainers with friction between first crown and coping crown, c. buffer-telescopic crowns retainers, and works with Classâ… alveolar bone loss. The models past stress tests, matched the stress distribution of actual situation and proved effective.2. Under vertical stresses, stress value of abutments'periodontal tissues restored by PFM bridge fixed by telescopic crowns retainers is lower than the one restored by fixed PFM bridge.3. Under vertical stresses, stress value of abutments'periodontal tissues restored by PFM bridge fixed by buffer-telescopic crowns retainers is the lowest, the stress of non-buffer-telescopic crowns retainers with friction between first crown and coping crown is lower than the one without friction between first crown and coping crown.4. When Classâ… alveolar bone defect, the abutments'stress become higher, but the increase is different between different restoration methods. The increase of fixed denture model is a little bigger than the telescopic crowns models.Conclusion: 1. When establishing 3-D finite element model of telescopic crowns, different types of connection between first crown and coping crown cause different stress value. It is important and feasible to create friction connection between first crown and coping crown, because it does affect the stress value of abutments'periodontal tissues.2. To restore mandibular incisor defect caused by periodontal disease, it is better to use telescopic crowns retainers than fixed bridge, in both convenience of periodontal care and protection of periodontal tissues. This research gives a theoretical support of application of PFM bridge fixed by telescopic crowns retainers.