Evaluation of the Effect of Nanographene Oxide on Microleakage of Conventional and Resin-Modified Glass Ionomer

Abstract

Objectives: One of the important features of the restorative materials is the ability to seal and prevent the microleakage. Glass ionomer cement (GIC) still exhibits some microleakage despite establishing a chemical bond to the tooth. The aim of this study was to evaluate the effect of nanographene oxide (nGO) on the microleakage of conventional (CGIC) and resin-modified glass ionomer cement (RMGIC).

Methods: Thirty intact extracted molars were used. Class V cavities were prepared on their buccal and lingual surfaces. The samples randomly divided into two main groups of CGIC and RMGIC; each of them was randomly subdivided into three subgroups, including the group without nGO (control), the group with 1% nGO, and the group with 2% nGO. After restoring the cavities, they were subjected to thermocycling (1,000 cycles at 5/55°C). Two percent basic fuchsin solution was used to perform the microleakage test, and then the sectioned samples were examined by a stereomicroscope 40x. Kruskal-Wallis test, Dunn's test, and Mann-Whitney U test were used to analyze the data (P < 0.05).

Results: Group CGIC + 1% nGO at the gingival margin and group RMGIC + 1% nGO at both gingival and occlusal margins had significantly less microleakage than their control groups (P=0.008, P=0.002, P=0.023, respectively). Also, in these two groups, there were no significant differences between the microleakage of the occlusal and gingival margins (P=0.132, P=0.511, respectively), while in all other groups, the gingival microleakage was significantly higher than that of occlusal microleakage.

Conclusions: The addition of 1% nGO significantly reduced the gingival microleakage of CGIC and the occlusal and the gingival microleakage of RMGIC, while the addition of 2% nGO did not cause a significant reduction in microleakage.

Figure 1

Mean and standard deviations of occlusal and gingival microleakage.

Figure 2

The images of the samples under the stereomicroscope with 40x magnification. (a) Dye penetration with the score of 2 at the occlusal margin and the score of 3 at the gingival margin. (b) Dye penetration with the score of 1 at the occlusal margin and the score of 3 at the gingival margin. (c) Dye penetration with the score of 0 at the occlusal margin and the score of 3 at the gingival margin (O, occlusal margin; G, gingival margin; A, axial wall; the scores of dye penetration: 0 = no dye penetration; 1 = dye penetration less than half of the distance between the tooth surface and the axial wall; 2 = dye penetration more than half of the distance between the tooth surface and the axial wall, but no axial wall involvement; 3 = dye penetration involving the axial wall of the cavity).