Three-Dimensional Finite Element Analysis of the Effect of 1-Piece Superstructure on Mandibular Flexure

Purpose: Mandibular flexure may affect the stress distribution in the implant-supported fixed partial dentures, yet the phenomenon has received little attention infinite element analysis studies. The purpose of this study was to evaluate the restraining effects imposed by 1-piece cross-arch superstructure on mandibular flexure and implant stresses. Material: Mandibular deformation and stress distribution in an implant-supported prosthesis (5 implants and 1-piece superstructure with 165 mm bilateral distal cantilevers) were analyzed by a 3-dimensionalfinite element model of a human edentulous mandible. To determine the effect of 1-piece cross-arch superstructure on mandibular flexure restriction, incisal clenching was simulated. During incisal clenching, maximum contraction of dental arch occurs. For this purpose, 9 pairs of masticatory muscles were simulated by multiple force vectors over areas of attachment. Results: A significant amount of stress (262 MPa) at the cortical bone surrounding the neck of the implant located at the symphysis assumed as a consequence of mandibular flexure. At the same area, maximum strain value of 1680 microstrain was detected. Moreover, maximum deformation of 0.35 mm was observed at the mandibular angle. Conclusions: One-piece implant-supported superstructure restricted mandibular deformation to almost half of the amount observed in unrestricted mandibular models of previous studies. This phenomenon must be considered in finite element analysis studies. (Implant Dent 2005;18:428-437)