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Passos SP, Torrealba Y et al. J Prosthodont 2014; 23: 593–601

Selected terms were used to identify 142 potentially, eligible studies. The search was restricted to monolithic zirconia restorations. Twenty-five papers were examined of which seven met inclusion criteria. All studies were carried out in the laboratory. A meta-analysis was not possible because of methodological heterogeneity. For example, 1) some studies failed to use a wear method with a sufficient large slide (for example 0.7 mm), 2) other studies used enamel specimens with no cusps, and 3) the testing regimen did not employ at least 200,000 cycles although this number is somewhat empirical. The key observation was the 'glazed specimens presented more antagonist wear than the polished specimens' when the zirconia was polished with 1,200-grit abrasive paper. But then there is low temperature degradation (LTD) of yttriastabilized ceramic. In the presence of water, LTD results in in loss of strength of the material, surface degradation that in turn may effect wear characteristics. None of the studies examined LTD.