The effect of various acidic beverages on microhardness and surface roughness of a nanohybrid composite resin and a high viscosity conventional glass ionomer

The aim of this in vitro study was to evaluate the effect of various acidic beverages on microhardness and surface roughness of a nanohybrid composite resin (Kalore; GC) and a high viscosity conventional glass ionomer (Fuji IX GP Extra; GC).In this study, 120 disc ( 5 mm in diameter and 2 mm in depth) were prepared from the restorative materials (Kalore, Fuji IX GP Extra). Stainless stell mold was used to fabricate the samples which were all A2 colour according to the vita scale. First, all samples were divided into 2 main groups (composite groups n: 60, glass ionomer groups n: 60) then they further divided into 6 subgroups, 10 samples each. The top and bottom surfaces of discs were ground with 1200 grit silicon carbid paper under running water. The initial microhardness measurements of samples were obtained on top surfaces and the roughness measurements were obtained on the bottom surfaces. Control groups of the two main group (Group CK, KK) were stored in distilled water without subjecting to any acidic cycling. For experimental groups, the samples were immersed in coke in Group 1, in coke diluted with water in Group 2, in Nestea peach in Group 3, in Nestea lemon drink in Group 4 and in orange juice in Group 5. The samples were immersed in beverages for a total of 12 hour which is equivalent in time to 2 min daily use of beverages for 1 year. The experimental groups stored in beverages for the entire experimental period to stimulate alterations produced on restorative materials in a moist in vivo environment. The samples were stored in beverages for 3 days, 4 hours per day. During the remaining period the specimens were stored in 37 °C in a dessicator. After the immersion period was completed, microhardness and surface roughness measurements were reevaluated. The microhardness measurements were performed with Vickers test and for each sample the Vickers hardness number was determined on the basis of five indentation measurements on different areas of the specimen. Surface roughness (Ra) was measured and 4 measurements were recorded for each specimen and mean Ra value was determined.The statistical analysis of the results were performed by `? Oneway ANOVA ??, `? Tukey HDS `?, `? Student t `? and `? Paired sample t `? tests.In conclusion, there were statistically significant differences in the average reduction of hardness values of composite groups after the immersion in acidic beverages than initial values of the experiments. The reduction of hardness values in the control composite group (KK) was lower than other composite groups (K3, K4 and K5). The reduction of hardness value of K3 was significantly higher than K1 and K2. There were statistically significant differences in the increase of surface roughness values of composite groups after the immersion in acidic beverages than the initial values.In glass ionomer groups, there were significant differences in the average reduction of hardness values after the immersion in acidic beverages than the initial values. The reduction of hardness values in C3 and C4 glass ionomer groups were higher than other glass ionomer groups (C1, C2, C5 and CK). There were significant differences in average increase on surface roughness of glass ionomer after the immersion in acidic beverages than the initial values. The increase of roughness values in the control glass ionomer group (CK) was lower than other glass ionomer groups (C3, C4 and C5).As a result; it was determined that beverages affected the surface roughness and microhardness of restorative materials (Fuji IX GP Extra; GC, Kalore; GC) regardless of their pH.Key words: nano-hybrid composite, glass ionomer cement, microhardness, surface roughness, acidic beverage.