Implant design and interface force transfer - A photoelastic and strain-gauge analysis

Objectives: To compare stress and strain magnitudes of butt-joint and internal-cone oral implants in a bone simulant. Material and methods: Photoelastic and strain-gauged models of solitary Branemark((R)), ITI(R) and Astra Tech((R)) implants were obtained. Vertical and 20degrees oblique forces of 100 and 150 N were applied on the abutments in separate load cases. Isochromatic fringe patterns around implants were observed and photographed in the field of a polariscope. Strain-gauge measurements were performed and principal strains induced around implants were calculated. Results: Isochromatic fringe orders of all designs were similar under both loading conditions (P>0.05). Strains around Branemark((R)) implants were lower than around Astra Tech((R)) and ITI(R) implants, particularly under vertical loads. The latter implants had similar strain magnitudes (P>0.05), although strains around the conical Astra Tech((R)) implant were lower under vertical load. Conclusions: Butt-joint and internal-cone oral implants have similar force distribution characteristics. The implant-abutment mating design is not a decisive factor affecting stress and strain magnitudes in a bone simulant.