Finite element stress analysis of the effect of short implant usage in place of cantilever extensions in mandibular posterior edentulism

Although the destructive effect of cantilevered implant supported fixed partial prosthesis is well known, in some cases usage of cantilever extension seems to be inevitable for many clinicians. The purpose of this study was to evaluate the effect of additional placement of a shorter implant in place of a cantilever extension on stress distribution compared with cantilevered fixed prosthesis in mandibular posterior edentulism. A mandibular Kennedy II finite element model was constructed. Six different implant supported fixed partial prosthesis were designed according to two main configurations; anterior and posterior cantilever extensions compared with the placement of additional shorter implant configurations. An oblique occlusal load of 400 N was applied. Tensile and compressive stress values in the cortical bone surrounding the cervical regions of implants and Von Misses stress values in the implants were evaluated. Significant lower stress values were recorded at the shorter implant placement configurations compared with the cantilevered prosthesis. Posterior cantilever extension performed higher stress values than the anterior counterpart. in clinical applications where cantilevered fixed partial prosthesis seems to be inevitable because of anatomical restrictions and/or complications such as loss of implant, an additional placement of a shorter implant should be considered.