Evaluation of the stress distribution of the bone implant connection (BIC) against applied forces to fixed partial restorations supported by two implants with different lengths using finite element analysis

The early lose of teeth due to periodontal problems (especially in youth) can cause a set of functional esthetic and phonetics problems. At the same time the elderly patient whoes not suitable to fixed prothesis or patients whoes not favorable for movable prothesis due to resorption of the alveolar bone gave rise for the need of implant treatment. The anatomic limitations is associated with surgical risks which directed the researchers for the research of using a shorter implants. The aim of our study, in the fixed osseointegrated implant prosthesis, the length of the pontics in fixed prosthesis which is biomechanically important and the length of the implant body; the effect of the implant on the surrounding bone tissue will be investigated by three dimensional finite element stress analysis method. In our study, vertical and oblique forces on three and four-unit implant-supported fixed prosthetic restorations, supported with 6 mm and 12 mm length, 4.2 mm diameter implants were evaluated by using ANSYS 2019R2 finite element package program. The maximum and minimum principal stress values for cortical and cancellous bones and the Von Mises stress values of all structures were compared. In four-unit implant supported fixed prosthesis models, higher stress values occured in all structures compared to three-unit restorations. The stress values for the implant body were the highest in the short implant (6 mm). Greater stress value was occured in the surrounding cortical bone of the model supported with a short and a standart length implant, but it was not more than the short implant. This value was in the connection screw in standart implants. It was concluded that oblique forces should be avoided for both three and four-unit implant supported fixed restorations.