Most dental cements harden through an acid-base reaction, which has initially a low pH. Because of this it would be expected that decalcification of teeth will occure. In this study, several cements were mixed and applied to human dentin. SEM observations were carried out on the cement-dentin interface and the dentin surfaces. Zinc phosphate cement revealed severe decalcification of the dentin, and was followed by glass ionomer luting cements for degree of severity.
The hybrid layer is essential to creat bonding to dentin. The importance of hybrid layer is not only bonding to dentin but it could improve characters of dentin. It could resist against demineralization and degradation with sodium hypochlorite. This modification is very important but we did not realize the merit. The hybrid layer does not permit invation of stimuli such as microorgaisms and their products which has been impossible before.