A Finite Element Analysis to Study the Stress Distribution on Distal Implants in All-on-Six Treatment Concepts as Affected Tilted and Short Implant.

The number of implants and their respective configurations for implant-supported treatment modalities have been studied for 4 implant-supported prostheses; however, it is not yet clear whether the use of tilting or short implants in rehabilitation would result in substantially improved bone/implant/prosthesis biomechanics in all-on-six concepts. This study compared the biomechanical behavior of tilted long implants and axially short implants to support fixed prostheses in an atrophic maxilla with all-on-six treatment concepts. Three different implant configurations were planned, and six models were obtained with posterior maxilla D3 and D4 bone densities in this study. Implants proper for the all-on-four concept were placed in all models. In models 1 and 2, the short implant was placed; in models 3 and 4, 30°, the mesial-angled implant was placed; and in models 5 and 6, 45°, the mesial-angled implant was placed to the molar region. In the models created, 200 N vertical and 150 N oblique (45° angled buccopalatal direction) forces were implemented to the bilateral tooth regions 4-5-6 on the rigid titanium-supported fixed hybrid prosthesis made on these models. When the stress values in the models were investigated, the oblique forces had higher stress values than the vertical forces did. When the stresses created by oblique forces were assessed, the highest values were observed in the models created with short implants, and the lowest stress values were observed in the models made with 30° angle to mesial. When bone densities were assessed, more stress values were noted in models with D4 bone density. It has been shown that mesial tilted long implants placed in the posterior molar region, in addition to all four implant treatment concepts, create less stress against undesirable oblique forces compared with short implants.