Toxicity of resin-matrix composites in a dental clinical setting.

The aim of this study was to perform a systematic review to comprehensively explore the factors contributing to the resin-matrix composites' toxicity in patients. A systematic review was performed according to the PRISMA guidelines. The bibliographic review was performed in the following databases: PubMed, Cochrane Central and Web of Science. Inclusion and exclusion criteria were established to retrieve articles published in English over the last 20 years. The research yielded 1261 articles, with 1227 articles remaining after removing duplicates. Following a title and abstract screening, 20 articles underwent full-text review, and 12 in vivo studies were included. Detectable levels of free monomers and potential toxicity exposure were reported in the selected studies on saliva, urine, and blood samples. The selected in vivo studies suggest relatively low local and systemic toxicity although the available methods show technical limitations and therefore further studies are required. Dental operator-dependent factors were also identified. Standard chair-side guidelines on handling of resin-matrix composites placement plays a key role on the properties of the materials. The results reported noticeable changes in samples were not considered significant to affect patient's health, although, manufacturer's instructions must be followed whilst using resin-matrix composites. In fact, adequate light curing parameters maintain a high degree of conversion of the resin-matrix composites  decreasing the release of residual monomers and thus the probability of related  toxicity.