Effect of Sodium Fluoride on the endogenous MMP Activity of Dentin Matrices.

OBJECTIVES: This study evaluated the effect of incorporating increasing concentrations of sodium fluoride in incubation media, on the loss of dry mass and solubilization of collagen from demineralized dentin beams incubated for up to 7 days. The effect of fluoride on the inhibition of matrix-bound metalloproteinases (MMPs) was also measured.

METHODS: Dentin beams were completely demineralized in 10% phosphoric acid. After baseline measurements of dry mass, the beams were divided into six groups (n=10) and incubated at 37°C either in buffered media containing sodium fluoride (NaF) at 75, 150, 300, 450, 600 ppm or in fluoride-free media (control) for seven days. Following incubation, dry mass was re-measured. The incubation media was hydrolyzed with HCl for the quantitation of hydroxyproline (HYP) as an index of solubilization of collagen by endogenous dentin proteases. Increasing concentrations of fluoride were also evaluated for their ability to inhibit rhMMP-9.

RESULTS: Addition of NaF to the incubation media produced a progressive significant reduction (p<0.05) in the loss of mass of dentin matrices, with all concentrations demonstrating significantly less mass loss than the control group. Significantly less HYP release from the dentin beams was found in the higher fluoride concentration groups, while fluoride concentrations of 75 and 150 ppm significantly reduced rhMMP-9 activity by 6.5% and 79.2%, respectively.

CONCLUSIONS: The results of this study indicate that NaF inhibits matrix-bound MMPs and therefore may slow the degradation of dentin matrix by endogenous dentin MMPs.