Microhardness of restorative composites after exposure in physiological solution
Krzysztof Pałka, Jarosław Bieniaś, Agata Niewczas, Małgorzata Muzyka
Quarterly No. 1, 2009 pages 49-52
DOI:
keywords: restorative composite materials, micro and nano fillers, Vickers microhardness, storage
abstract Restorative materials used in dentistry are required to have long-term durability in the oral cavity. In some cases the interaction of these materials with oral fluids may involve dissolution or degradation of surface layers. Such a fluid absorption may affect the mechanical properties of the materials and inflict damaging dimensional changes. This study was conducted to compare the effect of 4-week storage period in physiological solution on the surface microhardness measured in Vickers units, between materials with micro- and nano-fillers. Vickers microhardness was assessed in two nano-filler materials: Filtek Supreme and Grandio and two of micro filler materials: Filtek Silorane and Gradia stored in physiological solution at 37°C for 4 weeks. Measurements were taken at 1st, 14th and 28th day. The statistical evaluation was done by one-way analysis of variance. Materials with nanofiller showed a higher microhardness at the beginning of the study as compared with the materials with microfillers. The microhardness of Filtek Supreme significantly diminished in the final stage of the study, whereas that of Grandio showed decreasing tendency but without significant difference. Similar changes were observed for Gradia, however, they exhibit a much lower microhardness throughout the study period. Filtek Silorane based on the new silorane resin manifested different changes of microhardness as compared with other materials tested. Microhardness of Filtek Silorane increased to 65.6 HV0,02 at 14 days of storage, then slightly decreased to 61.56 HV0.02 at the end of the test period. The results suggest that the amount of filler did not appear to improve the surface microhardness of materials. Restorative materials based on Bis-GMA matrix showed influence of storage time in physiological solution on microhardness value. Results obtained for Filtek Silorane showed the lack of microhardness reduction caused by stability of silorane resin matrix in water environment.