Microhardness, Degree of Conversion, and Water Sorption/Solubility of Non-expired and Expired (Two and Three Years) Dental Composites

Objective:The aim of this study was to compare the microhardness, degree of conversion, and water sorption/solubility of two- and three-year expired dental composites (Filtek Ultimate Universal) with the non-expired equivalent.Methods:The prepared specimens (diameter =8 mm; thickness =2 mm) were subjected to Vickers hardness testing on the top and the bottom surfaces, and the degree of conversion was calculated based on the bottom/top hardness ratio. Further, water sorption and solubility were measured after immersion in distilled water for 1, 7, and 28 d. For statistical analysis, Shapiro-Wilk test, one-way analysis of variance, Kruskal-Wallis test, repeated analysis of variance and Friedman test were used (p