Evaluation of the stresses on the implant and the surrounding bone; from the different inclunacitions on the implant fixed prosthesis and the different infrastructure materials, for mandibular posterior region tooth deficiency: A three-dimensional finite element analysis

Purpose: The aim of this study is to evaluate the stress caused by the fixed prosthesis under oblique forces around dental implants and bone by using different infrastructure materials and different inclusions. Material and methods: The implants were selected from the Nobel Active company. The anterior and posterior implants were 10 mm in length and 4.3 mm in diameter. The anterior implant was placed in parallel in each model. Posterior implant designed to make (mesial 17°, distal 17°, buccal 17°, lingual 17° ) inclination. In our study; implant-supported fixed restorations will be divided into 3 main groups according to infrastructure materials. Chrome-cobalt, zirconia, PEEK. In each model, a total of 500 N oblique force was applied from the buccal tubercle crests to the buccolingual direction at an angle of 30 degrees to the long axis of the tooth.The highest Maximum Principal stress and Minimum Principal stress values in the models were taken. In addition, Maximum von Misses stress values were obtained from implants and infrastructures. Results: When the stress findings occurring in all structures during oblique loading were evaluated, it was found that the stresses in cortical bone were higher than the stresses in the trabecular bone. It was seen that the highest stress values occurred in implants. When the stress values formed in the infrastructures were examined, it was seen that lower stress values occurred in the PEEK infrastructure models. When the stress values in posterior implants were examined, it was seen that higher stress values occurred in PEEK models. Conclusions: In our study, the highest cortical shrinkage values were observed in the PEEK buccal group inclined 17 degrees, and the lowest cortical shrinkage values were observed in the PEEK lingual inclined group 17 degrees. The highest values observed in the buccal may be due to the application of oblique forces from the buccal direction. PEEK; since it has a lower Poisson's ratio than Cr-Co and zirconia, it could not fully transmit the force and accumulated on itself. When we look at the von Mises stress values in the infrastructures, the highest values of Cr-Co, zirconia and PEEK were found in the groups inclined at 17 degrees. The lowest values were also found in groups inclined at 17 degrees to the lingual. When the stress distributions in Cr-Co and zirconia infrastructure models were examined, it was observed that the highest stress values occurred in the connector region, while the highest stress values in PEEK infrastructure models were found to occur around the area close to the gingiva of the support crowns. When we look at the von Mises stress values in the implants, the highest values were found in the groups inclined at 17 degrees in the buccal. The lowest values were also found in groups inclined at 17 degrees to the lingual. It was determined that the highest stress values in all models were concentrated in the neck region of the posterior implant. It was observed that the highest stress values in implants occurred in Peek models throughout the study. It was observed that the highest and lowest von Mises stress values in Cr-Co and zirconia substructured implant models were similar.