Mineralization in bovine dentin adjacent to glass-ionomer restorations

Objectives: To assess the uptake of fluoride as well as the increase in mineralization by bovine dentin after restoring an experimentally made cavity with conventional glass-ionomer cement or a polyacid resin composite. Methods: Cylindrical cavities were prepared on the labial root surfaces in bovine dentin. The cavities were restored with the test material. The restored teeth were individually suspended in distilled water at 37°C for 30 days. The teeth were sectioned and the superficial dentin cavity walls were analyzed for fluoride, calcium, and phosphorus by an EPMA device. The effects of the different fluoride-releasing materials on the hardness of the dentin were determined by indentation (20-μm intervals below the filled surface into the underlying sound dentin from the surface to a depth of 100 μm). Results: Conventional glass-ionomer cement had a significant effect on fluoride uptake. In addition, the calcium and phosphorus scan revealed the elevation of calcium and phosphorus levels in a deeper zone corresponding to the locations of the fluoride uptake at the surface of axial wall. However, the polyacid resin composite did not exhibit a zone of calcium and phosphorus elevation. The average dentin hardness under conventional glass-ionomer cement in the studied five distances ranged from 84.3 to 61.3 KHN, however, that of the polyacid resin composite ranged from 62.5 to 64.9 KHN. Analysis of variance for these data demonstrated a significant difference in hardness between the 20-μm depth and the other depths (P<0.01, ANOVA Fisherʹs PSLD). Conclusion: The present paper indicates that the fluoride penetrated deeper into the dentin with conventional glass-ionomer cement than the polyacid resin composite. Conventional glass-ionomer cement had a significant effect on fluoride uptake. In addition, hypermineralization occurred within the superficial dentin cavity wall region of conventional glass-ionomer cement.