Objective: In recent years, immediate loading implant treatment has been widely recognized as an effective solution for edentulous patients. Risk factors of disintegration associated with immediate loading include excessive occlusal force such as bruxism, and relating to the technical complication, the fracture of temporary restoration has been pointed out. The fracture of temporary restoration can be considered to increase the micro movement around implant, and lead to fail osseointegration. A large numbers of stress analysis for implant prosthesis has been reported by 3D FEA and mechanical tests, but it has not been clarified the cause of fracture of the temporary restoration in multidimensional analysis. In this study, we analyzed the stress concentration in patient models by 3D FEA and the cyclic fatigue test in materials for temporary restoration, and tried out the combination stress analysis. 

Subjects and Methods: The strength to be possessed as a temporary prosthesis was examined by 1) the stress test, 2) the three-point bending test and 3) the three-dimensional finite element analysis (FEA). 1) For the 100000 cyclic fatigue test, a test piece of 25 mm in length × 10 mm in width × 2 mm in thickness cut out from a resin disc for CAD/CAM (Aadva PMMA disc, GC Co.) was used. 2) For the three-point bending test, a similar test piece to the one used in the stress test was used. 3) For the FEA, the results of the three-point bending test was reproduced and analyzed. Test pieces were similar condition. 4) To recognize the clinical situation, another FEA was done with the immediate load patient model. These models were maxillary edentulous patients before implant placement. To assume immediate load, the inter-face between the bone and the implant was set as a “contact state” (frictional coefficient = 0.33). The physical property values of the bone were calculated from the CT values and set for each element, and the physical property values of other elements were set based on the known values. The load condition was set based on the occlusal force data recorded from a patient with bruxism, and the constraint condition was set as the maxillary sinus upper margin. This study was approved by the ethics committee of our school of dentistry and the data was used with the patient’s consent.


Results: From the 105 cyclic fatigue test, it is revealed that the PMMA piece was fractured over 115 N load. In the three-point bending test, the average maximum tensile stress in the test piece was 80.3 MPa at 115 N load, that of FEA analysis was 75.5 MPa at the same condition. In the FEA patient models, the maximum tensile stress over 75.5 MPa was found at the PMMA material around temporary cylinder, and maximum value were 247.7 MPa, 258.8 MPa and 290.8MPa for each patient.

Discussion and Conclusion: The fracture of temporary restoration in immediate loading treatment is estimated to occur around temporary cylinders. It is necessary to consider temporary restoration designs or reinforcement not to exceed the maximum tensile stress in real clinical situation. From the results of this study, it is suggested that the effective possibility of combination stress analysis in real material and FEA model.

EAO SEPES 2017