Aging Effects of Dental Restorative Materials upon Surface Hardness
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Date
2009
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JOURNAL OF POLYMER MATERIALS
Abstract
This study was conducted to compare the effect of one-year storage of one indigenously developed and seven commercially available dental restorative materials on surface microhardness (VHN) and the use of hardness value as an indirect measure of degree of conversion and degradation in aqueous medium. Four composite pastes (Spectrum- TPH, Z-100, P -60 and indigenously developed Ormo 48, one compomer (F- 2000) and three glass ionomers (Fuji II LC, Fuji II CC and Ketac Molar) were either self or light cured and stored in distilled water at 37 +/- 1 degrees C and Vickers microhardness was measured at intervals of 1 hour, 1 and 7 days, 1, 3, 6, 9 and 12 months. A minimum of 6 measurements was carried out on both surfaces. Mean and standard deviations were calculated. Statistical evaluation was done by means of one-way analysis of variance (ANOVA). Degradation and monomer conversion were correlated with the support of Fourier Transform Raman spectra of cured and uncured paste. A significant difference in hardness was noticed for each material over storage time. Among the materials tested, composites exhibited the highest hardness values throughout the study. The values reached a maximum after 24 hours and showed a significant decline over a period of 1 year. Compomer had the maximum hardness after seven days. However in case of FUJI glass ionomers, no significant change in hardness was noticed even after 1 year whereas Ketac Molar showed a significant increase in hardness with time. FT Raman spectra of photo cured organically modified ceramics composite showed residual unsaturation (1610 cm(-1) peak). The results indicate that composites and compomers show significant decrease in hardness with time whereas glass ionomers tend to show either significant (P< 0.05) increase or no change on storage.
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Polymer Science
Citation
26 ,2;207-214