Shock absorption capacity of restorative materials for dental implant prostheses: an in vitro study.

Aims: The aim of the present in vitro investigation was to measure the vertical occlusal forces transmitted through crowns made of different restorative materials onto the simulated peri-implant bone. Methods: The study was conducted using a masticatory robot that is able to reproduce the mandibular movements and the forces exerted during mastication. During the robot mastication, the forces transmitted onto the simulated peri-implant bone were recorded, using 9 different restorative materials for the simulated single crown: zirconia, two glass ceramics, a gold alloy, three resin composites and two acrylic resins. Three identical sample crowns for each material were used. Each crown was put under 100 masticatory cycles, occluding with the flat upper surface of the robot in order to evaluate the vertical forces transmitted. Two-way analysis of variance (ANOVA) was used. Alpha was set at .05. Results: The statistical evaluation of the force peaks recorded on the vertical z-axis showed mean values of 641.8 N for zirconia, 484.5 N and 344.5 N for glass ceramics, 344.8 N for gold alloy, 293.6 N, 236 N and 187.4 N respectively for the three composite resins, and 39.3 N and 28.3 N for acrylic resins. Significant differences were found between materials (p-value < .0001) except the comparison between gold alloy and one of the glass ceramics. Conclusion: Composite and above all acrylic resin crowns were more able to absorb shock from occlusal forces than crowns made of zirconia, ceramic material or gold alloy.