Knoop Hardness of GIC with Three Different Insertion Techniques

Objectives: The aim of this study was to assess the Knoop hardness of a hand-mixed glass-ionomer cement (Ketac Molar Easy Mix – 3M ESPE), inserted in three different ways: G1 – with a conventional applier, G2 – with a commercial syringe (CentrixTM), and G3 – with a low cost syringe. Methods: The glass-ionomer cement was mixed according to the manufacturer's instructions and 10 specimens of each group were prepared in PVC molds, at room temperature, following one of the insertion techniques. The cylindrical molds were slightly overfilled and covered with milar strips and pressed flat with a glass plate. After 10 minutes, the specimens were stored in lubricant (Paraffin highly liquid, Merck) at 37ºC, for 24 hours. The surfaces were wet polished with 1200 grit paper (Buheler), till the excess was removed. The micro hardness was determined a HM-124 hardness tester (Mitutoyo, Japan), with 25 g load and 30 s dwell time. On each specimen five indentations were made and repeated after 1 and 2 weeks while stored under the same conditions. Results: The mean Knoop hardness (and SD) of each group was: G1 – 92,0 (22,2); G2 – 96,0 (33,9) and G3 – 81,92 (34,3). There was no statistically significant difference between the ways of insertion (ANOVA, p>0,05). The hardness after 1 and 2 weeks was significantly higher in all groups (ANOVA and Tukey, p<0,01).There was no difference between the measurements after 1 and 2 weeks. Conclusion: The different insertion techniques had no influence on the glass ionomer cement hardness.