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

Abstract

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<0.05).Results:No significant changes in microhardness, degree of conversion, or water solubility were observed between any of the groups. However, the water sorption of the non-expired dental composite was higher than that of the three-year expired group after 28 d. Further, the water sorption/solubility of all of the expired and non-expired materials changed over time between 1 and 28 d.Conclusion:Thus, the non-expired, two-year expired, and three-year expired dental composites exhibited similar microhardness, conversion degree, and water solubility characteristics. However, the degradation of dental composites is a complex process, and dentists are advised to adhere to expiration dates.

Keywords

• aging
• composite resin
• dental restoration
• dentistry
• hardness