Comparative Finite Element Analysis of Short Implants with Different Treatment Approaches in the Atrophic Mandible

Purpose: This three-dimensional finite element analysis study aimed to compare the stresses transmitted to short, tilted, and vertical implants used in different configurations and to the surrounding peri-implant bone in the atrophic mandible. Materials and Methods: A three-dimensional model of an atrophic mandible was made using customized computer software. Four models including short, tilted, and vertical implants were constructed with and without cantilever extension. Four or six implants in different configurations were placed into the models and mounted with the same fixed prosthesis. An oblique force of 200 N was bilaterally applied to the most distal part of the fixed denture. Von Mises stress values on implants and minimum and maximum principal stress values transmitted to peri-implant bone were analyzed. Results: The highest stress values recorded in the tilted implants (von Mises: 129 MPa), in the peri-implant bone around the tilted implants (minimum principal stress: –40 MPa), and overall stress values were found to be higher in the model including tilted implants with cantilever extensions. Distally placed short implants, with consequent elimination of the cantilevers, resulted in decreased stress values for all of the treatment variabilities of an atrophic mandible. Von Mises stress values were found as 129 MPa in tilted (model I), 48 MPa in short (model II), 47 MPa in short (model III), and 57 MPa in vertical (model IV) at the most distal implant location. Lower compressive stress values were noted in the bone around straight and short implants compared with the tilted implants in all models (model I, tilted: –40 MPa; model II, short: –34 MPa; model III, short: –33 MPa; model IV, vertical: –25 MPa). Conclusion: Distally placed short implants contributed to the reduction of stress values of the implants and the surrounding bone. The combination of two short and four straight implants without cantilevers may be a beneficial design in the rehabilitation of posteriorly atrophic mandibles. Keywords: atrophic mandible, bone, finite element analysis, short implant, stress, tilted implant