Response of oral mucosal cells to glass ionomer cements

Although glass ionomer cements are generally considered to be tissue-compatible, it has been suggested that unreacted components or setting reaction by-products can affect cell metabolism. The current study examined the effects of constituents leached out of three glass ionomer cements on growth and metabolism of oral epithelial cells. Aseptically prepared discs of Ketac-Cem Radiopaque (KCR), Ketac-Cem Maxicap (KCM) and Fuji I were incubated in Dulbecco's medium for 10 d, with daily medium changes. Cultures of hamster cheek pouch (HCP) cells, a line of hamster buccal pouch epithelial cells, were incubated in control or eluate-containing media for 24 h. Viable cell numbers were determined by the colorimetric MTS assay, and DNA and RNA syntheses were assessed using [3H]thymidine and [3H]uridine incorporation, respectively. Responses to materials were determined by comparison of cell numbers and radioisotope incorporation (counts per minute (cpm) per 1000 cells). Results were analysed by ANOVA and Duncan's multiple range test, then converted to percent control for comparison. The eluates of all three materials from the first 24 h of soaking inhibited HCP cell growth. The number of cells in cultures exposed to Fuji were 88% of control cultures, while those exposed to KCR and KCM were 58% and 59% of control, respectively. The difference between Fuji-exposed and control cultures was significant (P < 0.05). The two Ketac cements were different from Fuji-exposed and control cultures (P < 0.05) but not from each other. All of the materials caused significant increases in labelling of DNA compared to control cultures (P < 0.05) when calculated on a per cell basis, but the materials did not differ from each other. Both Ketac cements also significantly stimulated labelling of RNA per cell compared to control cultures (P < 0.05). All effects of the material decreased over time. Results suggest that leachable components of the materials may affect the rate of progression of HCP cells through the cell cycle, rather than overt toxicity that results in cell death.