SHORT-TERM CONTAMINATION OF LUTING CEMENTS BY WATER AND SALIVA

Objectives. The aim of this study was to determine the effect of water , artificial saliva and natural saliva on the hardening process of thr ee dental luting cements. Methods. Cement samples, 1 mm thick and 5 mm in diameter, were subjected to various storage conditions in an oven maintained at 37 degrees C. Some samples were aged in 100% humidity or water for up to 1 wk. The other samples were covered with water, arti ficial saliva or natural saliva at various times after mixing. The Kno op hardness values of the cement surfaces were measured. Differences b etween groups were evaluated with an ANOVA followed by a Tukey multipl e comparison at the 5% level of significance. The hardness ratio of th e contaminated samples was calculated using the 30 min mean KHN of the samples aged in 100% humidity as the divisor. Results. The glass iono mer samples were significantly harder (48.3 +/- 3.8) than the zinc pho sphate (38.9 +/- 7.5) or composite cements (35.4 +/- 10.2) after 1 wk in 100% humidity storage condition. When immersed in water, the hardne ss of both the glass ionomer and the zinc phosphate decreased to almos t half that of the specimens stored in 100% humidity (26.2 +/- 2.7 and 16.9 +/- 2.5, respectively). Contamination decreased the hardness of zinc phosphate and glass ionomer (hardness ratio, water contamination at 5 min: 0.39 +/- 0.10 and 0.52 +/- 0.12, respectively) but had very little effect on the composite. Overall, water had a greater softening effect than artificial or natural saliva on the cements. Significance . In light of these results, glass ionomer cement should be protected from water and saliva for the first 15 min after mixing.