Effect of Conventional Glass-Ionomer Cement with Zinc Oxide in Inhibiting Dentin Demineralization In Vitro

The aim of this study was to enhance the demineralization-inhibiting effect in dentin using a mixture of zinc oxide and conventional glass-ionomer cement (GIC). In the experimental group. cavities in bovine dentin were filled with GIC mixed with zinc oxide (GIC-Z group). In the control group, cavities were filled with GIC alone (GIC group). Specimens were immersed in acidic solution at 37°C for 0, 3, 6 or 9 days. Dentin was then observed under contact microradiography (CMR) for demineralization. For day 9 specimens, mineral loss was measured and specimens were observed under scanning electron microscopy (SEM). In addition, ordinary dentin samples were also observed for normal dentinal tubules. Electron probe microanalysis (EPMA) was used to investigate zinc infiltration into day 9 specimens in the GIC-Z group. Concentrations of Mg2+, Ca2+ and F- in the acidic solution were measured with day 9 specimens in both GIC-Z and GIC groups. Mechanical properties of compressive strength and disintegration rate were compared between the GIC-Z and GIC cements. On CMR images, subsurface demineralized lesions were observed in days 3, 6 and 9 specimens. Total mineral loss did not differ substantially between day 3 and day 6 specimens. Mineral loss was slightly reduced with the day 9 specimen in the GIC-Z group. Scanning electron micrograph of the polished surface before acid treatment showed that all dentinal tubules were open. In micrograph of day 9 specimen in the GIC group, many dentinal tubules were closed. In micrograph of day 9 specimen in the GIC-Z group, most dentinal tubules were closed. By EPMA analysis, intensity of Zn was highest at the dentin face in the GIC-Z group. Concentrations of Mg2+ and Ca2+ in the acidic solution were significantly lower in the GIC-Z group than in the GIC group. No difference in F- concentration was found between the two groups. Mechanical properties were not significantly different between the two groups. In conclusion, addition of zinc oxide to GIC contributes to inhibit dentin demineralization without major changes in mechanical properties compared to GIC.