Purpose: The purpose of this meta-analysis was to evaluate how the thickness variations in ceramic restorations of lithium disilicate and the use of different photopolymerizers influence the degree of conversion of the resin cements.
Methods: This study was performed according to the PRISMA checklist. The bibliographic research was performed to identify in vitro studies until December 2017 in the databases MEDLINE via PubMed, Web of Science, and Scopus. The selected studies were submitted to bias risk assessment. In the meta-analysis the data were evaluated using Review Manager Software v.5.3, with random-effect model at a 5% significance level.
Results: The meta-analysis in this study showed that despite the translucency of lithium disilicate, significant reduction of light was observed when activated through the ceramic. The degree of conversion was higher in the control groups in which the resin cement was photopolymerized without the interposition of the ceramic material.
Conclusions: The thinner the ceramic material, the higher the degree of conversion. A thickness greater than 1.0 mm drastically reduces the degree of conversion of dual-curing or light-curing resins. The curing unit with irradiance of 3200 to 3505 mW/cm2 showed improvements in conversion values.
Keywords: Ceramics; degree of conversion; lithium disilicate; resin cements.
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