Fluoride Prevents Dentin Matrix Degradation by Endogenous Collagenolytic Enzymes

Objectives: Demineralized dentin matrices degrade over time partly due to endogenous enzymatic activity of dentin matrices. Both matrix metalloproteinases (MMP) and cysteine cathepsins have been identified to be active in this process. Recently, inhibition of host-derived proteases by fluoride ions has shown promising results. However, the inhibition efficacy of different F^- compounds and concentrations are not known. This study aimed to evaluate the effect of NaF and KF on the enzymatic degradation of demineralized dentin matrix.
Methods: Dentin beams (1×2×6mm) were completely demineralized in 10% phosphoric acid for 24 h at 4°C. After initial dry mass evaluation, the beams (n=10/group) were assigned to different groups and incubated individually at 37°C in 1 mL of artificial saliva (AS, control), or AS with 5.9, 23.8 and 178.6 mM F^- containing NaF or KF. The changes in the dry mass of the beams were reassessed after the 1, 7 and 21 days of incubation. The total MMP activity was analysed by a colorimetric assay (SensoLyte®). Data were analyzed by using ANOVA and Tukey HSD tests (p=0.05).
Results: Both NaF and KF showed between 60-66 % decrease in total MMP activity compared to demineralized control beams (p<0.05). There were no significant differences between NaF and KF (p>0.05). The dry mass loss was 15.92(±2.29)% in the control group, and ranged between 8.43(±1.15)% and 7.83(±0.91)% for the NaF groups, and between 8.88(±2.33)% to 20.43(±6.69)% for the KF groups after 21 days of incubation. Increasing F^- concentrations decreased the mass loss significantly after 21 days of incubation (p<0.05).
Conclusions: Fluoride prevents the degradation of demineralized dentin matrices and the effect seems to be dose dependent. At lower concentrations NaF seems to be more effective than KF.