Biomechanics of implant-tooth supported prostheses: effects of mesiodistal implant angulation and mode of prosthesis connection

Abstract

The purpose of this study was to explore the effects of implant angulation and its possible influence on prosthetic connection as regards implant/tooth strains in a combined implant and natural tooth abutment fixed partial denture. A natural tooth was embedded between vertically-aligned and 17° angulated implants in a polymethyl methacrylate acrylic resin model. Three designs (Group 1: tooth and vertically-aligned implant; Group 2: tooth and 17° angulated implant, Group 3: tooth and vertically-aligned implant having a different prosthetic connection to Group 1) of tooth-implant supported prostheses (n=4) were fabricated. Strain gauges were bonded on the prostheses and on the approximal sides of the natural tooth abutment and implants. Once the test fixed partial dentures were seated, a static load of 150 N was applied to each prosthesis. During testing, strain-gauge signals were digitalized by a data acquisition system and this signal was stored and assessed with corresponding software at a sample rate of 10 KHz. The data were then evaluated using Mann-Whitney U and Kruskal Wallis tests at 95% confidence level. Mesiodistal tilting of implants increased peri-implant strains in implant-tooth supported prostheses during torque-tightening and under load. The mode of prosthesis connection may affect strains within the prosthesis and natural tooth abutments, although its impact under static loading conditions seems negligible. This investigation suggests that mesiodistal tilting of implants may have a biomechanical effect in tooth-implant supported prostheses.