Effect of different biocompatible implant materials on the mechanical stability of dental implants under excessive oblique load

Background: Metallic implants such as titanium are much harder than the neighboring bone. This high difference may generate larger stress at the bone-implant interface during load transfer which leads to implant failure. The use of biocompatible polymer such as CRF-polyether ether ketone (PEEK) with strength comparable with the bone might lead to lower and better stress distribution to the supporting periimplant bone. Purpose: The aim of this study is to investigate the effect of using carbon reinforced PEEK composite material for fixture/abutment on stress distribution in periimplant bone. Materials and Methods: Three-dimensional (3D) model of dental implant placed in the first mandibular molar is constructed from computed tomography scan. Five distinct models using a combination of titanium, CRF-PEEK, lithium disilicate for implant/abutment materials are studied. 3D finite element analysis (FEA) is used to evaluate the stress distribution at implant-bone interface under excessive oblique load. The physical interaction between several contacting bodies is numerically investigated. The effect of friction coefficients between the indenter and occlusal surface and between the implant and peri-implant bone is determined. Results: FEA results show that there is no significant difference in the distribution pattern of stress at implant-bone interface among the different material models studied. The highest maximum and lowest minimum principal stresses were always located in the cortical bone and never in the cancellous bone which is consistent with the existing literature. Off-axis loading can result in unfavorable forces on the implant, jeopardizing the long-term success because of excessive lateral loads. Current FEA results agree with previously published work. Conclusion: Substitution of titanium implant by PEEK implant does not provide any advantages in regards to better stress distribution to the peri-implant bone. The strain thresholds of Frost's mechanostat theory that are suitable for long bone could not be applied for alveolar bone.