Influence of maxillary cortical bone thickness, implant design and implant diameter on stress around implants: A three-dimensional finite element analysis

There is no clear evidence of the factors that could improve implant biomechanics in the posterior maxilla. Thus, a finite element analysis was performed to investigate the effect of maxillary cortical bone thickness, implant design and diameter on stress around implants. A total of 12 models of the posterior maxilla with implant were computer-simulated by varying the thickness of the alveolar cortical bone (1.5, 1.0, 0.5 or 0 mm) and implant characteristics (cylindrical implant of 4.1-mm diameter, screw-type implants of 4.1-mm or 4.8-mm outer diameters). On top of each implant, forces were separately applied axially (100 N) and buccolingually (50 N), and the von Mises stresses were calculated. Regardless of load direction, implant design and diameter, cortical and cancellous bone stresses increased with the decrease of crestal cortical bone thickness. In the absence of crestal cortical bone, cancellous bone stresses were highest and, under axial load, were transferred to the sinus floor. Implant design and diameter influenced stress to a less extent, especially under buccolingual load and in the presence of crestal cortical bone. From a biomechanical viewpoint, to improve implant success odds in the posterior maxilla, rather than implant selection, careful preoperative evaluation of the cortical bone at the planned implant site is recommended. If this cortical bone is very thin or even lacking, implant treatment should be carried on with caution by progressive loading in the range of functional loads.