Influence of graft quality and marginal bone loss on implants placed in maxillary grafted sinus: a finite element study.

The purpose of this study was to investigate the biomechanical effects of graft stiffness and progression of marginal bone loss (MBL) in the bone surrounding an implant placed in a maxillary grafted sinus based on the finite element method. The simulating model of graft stiffness as well as depth of MBL was varied to simulate nine different clinical scenarios. The results showed that the high-level strain distributions in peri-implant tissue increased with the increase in MBL depth when the stiffness of the graft was less than that of the cancellous bone (less stiffness graft models). The strain energy density (SED) value showed that a slight MBL depth (1.3 mm) with medium stiffness of grafted bone can reach the optimal load sharing due to the exhibited similar values of SED in the crestal cortical, cancellous, and grafted bone. With progression of MBL and the decrease in graft quality, maximal displacement of the implant increased considerably. Our results demonstrated that the effects of the two investigated factors (progression of MBL and graft stiffness) on the biomechanical adaptation are likely to be interrelated. The results also reveal that for clinical situations with poor grafted bone quality and progression of MBL, it is critical to consider implant stability.