Purpose: To perform a systematic review of the clinical performance of a low polymerization shrinkage, siloranebased composite (SBC) compared with a methacrylate-based composite (MBC) in posterior restorations.
Materials and methods: Electronic databases were searched: PubMed, Scopus, Bireme, Science Direct, Web of Science, ClinicalTrials.gov and OpenGrey. The search strategy included MeSH terms, synonyms and keywords with no language or date restrictions. Reference lists of eligible studies were cross checked in an attempt to identify additional studies. Based on the PICOS strategy, only randomized clinical trials (RCTs) were included. The risk of bias in the included studies was assessed and classified through the Cochrane Collaboration common scheme for bias. Two meta-analyses were performed using RevMan software, one with all 11 studies and another that included only studies with over 24 months of follow-up, for the main parameters analyzed.
Results: A total of 544 studies were identified. After removing duplicates and examinating titles and abstracts, 17 texts were selected and read in full. Six of them were excluded, so the final sample of this systematic review included 11 studies. Six of the 11 studies were classified as having a "low risk of bias" and five were "unclear". The heterogeneity (I²) in all parameters was not significant. The exclusion of studies with less than 24 months of follow- up did not change the final result of the meta-analysis: both SBC and MBC have satisfactory and statistically similar clinical performances.
Conclusion: Low polymerization shrinkage is not the principal factor that determines the superiority of a resin.