Evaluation of wear and hardness of zirconia with different surface treatment protocols a systematic review

Abstract

Objective: The objective of this systematic review is to assess the wear and hardness of surface treated zirconia. Methods: Two automated databases were investigated till July 2015 with no limits. The scientific terms: "Dental enamel", "Yttria stabilized tetragonal zirconia", "Tooth wear", "Enamel wear", "Hardness", "Translucent zirconia' and "Dental restoration wear" were used in this study. Initially screening was performed for the retrieved articles through title and abstract after that, full-text assessment was done to those articles that fulfilled the inclusion criteria. Findings: Sixty-nine potentially eligible studies were retrieved from the data base search; after duplicate removal the studies became sixty-three. Full-text assessment was performed for all titles and abstracts that met the inclusion criteria. Finally, seventeen studies met the inclusion criteria, and so their references were also screened. Applications/Improvements: Although studies applied different wear testing methodologies; wear testing devices, number of cycles, magnitude of force, number of samples, sample preparation for zirconia and enamel antagonist surface, as well as hardness measurement protocol, full contoured polished zirconia and human enamel (as antagonist) showed high resistance to wear. It was also concluded that zirconia showed high hardness as a surface property. It is recommended to polish the surface of restorations made of full-contour zirconia because this polishing favours the surface properties (wear and hardness) to opposing enamel.