EFFECT OF RESIN-MODIFIED GLASS IONOMER CEMENT ON TOOTH MICROHARDNESS UNDER TREATED CARIES

Dental caries are the most common oral disease. Resin-modified glass ionomer cement (GIC) is used to treat caries by promoting remineralization of these caries. However, the microhardness of teeth under these caries treated with GIC has been little studied. We conducted an in vitro study to evaluate the microhardness of teeth under caries treated with GIC in order to determine if it is improved with treatment and to what extent. The teeth used in this study were 20 bovine incisors. Knoop indentations were made on each studied tooth with a load of 50 grams for 15 seconds and then caries were produced on the labial surface of each tooth by immersing the tooth in demineralizing solution for 120 hours at 37 degrees C. The 20 study teeth were divided into two groups of 10 teeth each group: Group 1 (control group) received no treatment; in Group 2 resin-modified GIC was applied to the center of the labial surface of each sample tooth in the treatment group. Both groups were immersed for 7 days at 37 degrees C in artificial saliva. After 7 days, all the teeth were labio-lingually sectioned in sagittal plane through the middle of the tooth. The enamel microhardness was measured at 6 locations on each tooth 50 mu m apart in a vertical direction: 50, 100, 150, 200, 250, 300 mu m from the enamel surface where the caries were created in both the control and treatment teeth. The mean microhardnesses were calculated at each depth for both the treatment and control groups and compared using an independent t-test and a one-way ANOVA test followed by a Tukey's HSD multiple comparison test with a 95% confidence interval. There were significant (p<0.05) differences between the control and treatment groups at 50, 100 and 150 mu m from the enamel surface but not at 200, 250, 300 mu m from the surface (p>0.05). In the control group, the mean [+/- standard deviation (SD)] microhardness at 50 mu m from the enamel surface was the lowest [145.4 +/- 17.4 Knoop Hardness Number (KHN)] and significantly (p<0.05) less hard than all the other depths. In the treatment group, the mean (+/- SD) microhardness at 50 pm (208.9 +/- 15.4 KHN) and 100 mu m (206.1 20.8 KHN) were significantly (p<0.05) greater than at 300 m (180.9 +/- 13.6 KHN). In conclusion, the resin-modified GIC treatment significantly increased the microhardness of the enamel under the treated caries in bovine teeth down to a depth of 150 mu m.