Effect of irradiance from curing units on the microhardness of composite - a systematic review

Purpose The systematic review aims to evaluate the effect of light irradiance from light-curing units on microhardness of composite.Materials and methods The protocol was registered in PROSPERO following which primary search was carried out via MedLine, Scopus and Cochrane Library. A customised tool was used to assess the risk of bias. Among the 303 records retrieved from the databases, only ten articles qualified for qualitative synthesis after meeting all the requirements of the eligibility criteria. Covidence software was used to record the decisions. The studies published until 31 March 2021 were taken up for the review. The articles showed a low-to-moderate risk of bias.Results From a total of 303 articles, ten articles were reviewed for full text. Ten in vitro studies were included for qualitative analysis. There was heterogeneity in sample size, curing time and outcome measured. Therefore, meta-analysis was not performed. Out of ten studies, seven studies reported higher microhardness value for higher intensity than lower intensity of light.Conclusion Despite the fact that the findings of the evaluated studies are quite variable, significant scientific evidence revealed that high light intensity can enhance the hardness of resin composites.