Inhibitory activity of S-PRG filler on collagen-bound MMPs and dentin matrix degradation

Objectives: To evaluate the inhibitory activity of an ion-releasing filler (S-PRG) eluate on dentin collagen-bound metalloproteinases (MMPs) and dentin matrix degradation. Methods: Dentin beams (5 × 2 × 0.5 mm) from human molars were completely demineralized to produce dentin matrix specimens. The dry mass was measured, and a colorimetric assay (Sensolyte) determined the initial total MMP activity to allocate the beams into four treatment groups (n = 10/group): 1) water for 1 min (negative control); 2) 2% chlorhexidine digluconate (CHX – inhibitor control) for 1 min; 3) S-PRG eluate for 1 min; 4) S-PRG eluate for 30 min. After the treatments, the total MMP activity was reassessed. The specimens were stored in simulated body fluid (SBF) at 37 °C for up to 21 days. The dry mass was reassessed weekly. On day 7, the dentin matrix degradation was analyzed for the presence of collagen fragments (CF; Sirius Red) and hydroxyproline (Hyp) in the SBF. Statistical analyses were performed with ANOVA/Tukey, paired t-tests, and RM-ANOVA/Sidak (α = 5%). Results: S-PRG eluate exposure for 1 and 30 min reduced (p < 0.0001) MMP activity. S-PRG exposure for 30 min presented MMP activity inhibition equivalent to CHX (p = 0.061). S-PRG and CHX decreased CF (p ≤ 0.007) and Hyp (p < 0.046) release. After 21 days of storage, S-PRG-treated beams, regardless of exposure time, presented a reduced (p ≤ 0.017) mass loss, intermediate between CHX and control. Conclusion: Treating demineralized dentin with S-PRG eluate for 1 or 30 min reduced matrix-bound MMP activity and dentin matrix degradation for up to 21 days. Clinical significance: S-PRG filler may hinder the progression of dentin carious/erosive lesions and enhance the stabilization of dentin bonding interfaces.