Abstract: Objective: To evaluate the stress analysis of the surrounding bone tissue caused by the change of implant angle under different bone types in the case of insufficient bone mass in the maxillary posterior region by using three dimensional finite element analysis. Methods: SolidWorks 2015 software was used to establish the models of maxillary, implant, abutment, and dental crown. The maxillary model was defined as two bone types, D2 and D3. Each type of maxillary was classified into three categories according to the angle of implant placement, including vertical implant, 30 degree tilted implant, and 45 degree tilted implant. In the vertical implant, artificial bones were built under the maxillary model to simulate sinus floor elevation. The assembly was established, a force of 150N was applied at the top of the dental crown, with an angle of 45 degrees to the center. The stress distribution of surrounding bone tissue was analyzed. Results: The stress in D3 bone model was higher than that in D2 bone model. In the cortical bone, the stress in the vertical implant model was the minimum, followed by the 45 degree tilted model, and the maximum stress was in the 30 degree tilted model. Conclusion: In the maxillary posterior region with insufficient bone mass, the stress of tilted implant on surrounding bone tissue was higher than that of vertical implant. Sinus floor elevation and implant vertical implantation surgery was the preferred treatment. The 45 degree tilted implant was more advantageous than 30 degree one when tilted implant was undertaken

Key words: insufficient bone mass, tilted implant, bone type , sinus floor elevation, three dimensional, finite element analysis