Furthermore, there are experimental data indicating that the diminishing of dentinal fluid flow may reduce dentinal caries progression [45,46], but because the concentrations of MMP-1 and MMP-2 in the saliva of our patients with caries were increased in comparison to healthy individuals, and after the treatment we noted a decrease in MMPs, we speculate that the main source of MMPs in patients with caries is probably carious dentin. The gene discussed is MMP2; the disease is dental caries.