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 in finite 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 16.5 mm bilateral distal cantilevers) were analyzed by a 3-dimensional finite 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 (26.2 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.