Evaluation of different implant configuration and bone density effects in atrophic maxilla by finite element analysis

Implant rehabilitation in atrophic maxilla has been considered a surgical and prosthetic challenge due to the small quantity and low quality of bone. The use of bone grafting and sinus elevation has been an alternative technique for improving the implant placement location. Bone grafting and sinus lifting pocedures are known as invasive tecniques that has complication risks. The use of tilted or short implants has been demonstrated to be alternatives for these invasive tecniques. The aim of this study is to compare the biomechanical behavior of tilted long implant, vertical short/long implants to support fixed hybrid prosthesis in an atrophic maxila by FEM. An atrophic maxilla with a moderate sinus pneumatization was modeled by 'Solid Works 3D CAD' software. Twenty six groups were arranged and they were divided into two groups as D2 and D3 bone density groups. Type D2 bone was designed by trabecular bone that is coated by 1.5 mm cortical bone and the type D3 bone was designed as trabecular bone that is coated by 0.75 mm cortical bone. On the atrophic maxilla models implants were modified by different number, length, distaly tilting degree. Hybrid phrosthesis were arranged on each model. For simulating the biting force, a 150 N force was applied bilaterally and axially on the first premolar, second premolar and first molar. The stress around the implants was calculated by using Solid Works programme and the results were compared for each group. The results showed that the increase in implant length has positive effect on stress distribution on models. The use of tilted implant distally in atrophic maxilla increases the stress values in bone according to vertical implants. It was detected that optimal implant number is 7 for completely edentulous atrophic maxilla.