SELECTED PHYSIOCHEMICAL PROPERTIES OF DIMETACRYLATE RESIN BLEND MODIFIED WITH LIQUID RUBBER

In the oral cavity environment, light-cured dental composites are susceptible to water sorption. This process can have a detrimental effect on the polymer network over a longer period, thereby causing deterioration of the material properties. This study aims to evaluate the impact of modifying a dimethacrylate resin mixture with liquid rubber on water sorption and the water contact angle. The resin mixture contained BisGMA (20 wt.%), BisEMA (30 wt.%), UDMA (30 wt.%) and TEGDMA (20 wt.%). Liquid rubber Hypro 2000X168LC VTB was used as a modifier in quantities of 5 %, 10 %, 15 %, and 20 % by weight relative to the resin. Water sorption studies were conducted following the ISO 4049 standard, and water contact angle tests were carried out as well. The percentage change in the water sorption weight after 7 days was approximately 1.6 % for the sample containing 5 wt.% liquid rubber, while for the sample with the 20 wt.% liquid rubber content, this value was approximately 1.9 %. The addition of 5 wt.% liquid rubber caused the contact angle value to increase by 16.34 % after 30 days compared to the first day. In the case of the other samples, such significant differences were not observed. Microscopy was employed to assess the miscibility and morphology of the liquid rubber domains. The study results show that modification with liquid rubber significantly limits water sorption and contributes to increasing the hydrophobicity of the surface, which is significant from a clinical standpoint. In the range of rubber concentrations studied, its solubility in the resin was not found, and for the 5 wt.% content, the most uniform distribution of domains was observed. With a larger share of liquid rubber, an increment in the number of domains and their sizes was noted, both before and after polymerization.