Inhibition of endogenous human dentin MMPs by Gluma.

OBJECTIVE: The objective of this study was to determine if Gluma dentin desensitizer (5.0% glutaraldehyde and 35% HEMA in water) can inhibit the endogenous MMPs of dentin matrices in 60 s and to evaluate its effect on dentin matrix stiffness and dry mass weight. METHODS: Dentin beams of 2 mm×1 mm×6 mm were obtained from extracted human third molars coronal dentin. To measure the influence of Gluma treatment time on total MMP activity of dentin, beams were dipped in 37% phosphoric acid (PA) for 15 s and rinsed in water. The acid-etched beams were then dipped in Gluma for 5, 15, 30 or 60 s, rinsed in water and incubated into SensoLyte generic MMP substrate (AnaSpec, Inc.) for 60 min. Controls were dipped in water for 60 s. Additional beams of 1 mm×1 mm×6 mm were completely demineralized in 37% PA for 18 h, rinsed and used to evaluate changes on the dry weight and modulus of elasticity (E) after 60 s of Gluma treatment followed by incubation in simulated body fluid buffer for 0, 1 or 4 weeks. E was measured by 3-pt flexure. RESULTS: Gluma treatment inhibited total MMP activity of acid-etched dentin by 44, 50, 84, 86% after 5, 15, 30 or 60 s of exposure, respectively. All completely demineralized dentin beams lost stiffness after 1 and 4 weeks, with no significant differences between the control and Gluma-treated dentin. Gluma treatment for 60 s yielded significantly less dry mass loss than the control after 4 weeks. SIGNIFICANCE: The use of Gluma may contribute to the preservation of adhesive interfaces by its cross-linking and inhibitory properties of endogenous dentin MMPs.

Stabilization of dentin matrix after cross-linking treatments, in vitro.

OBJECTIVES: To evaluate the effect of EDC on elastic modulus (E), MMPs activity, hydroxyproline (HYP) release and thermal denaturation temperature of demineralized dentin collagen. METHODS: Dentin beams were obtained from human molars and completely demineralized in 10 wt% H3PO4 for 18 h. The initial E and MMP activity were determined with three-point bending and microcolorimetric assay, respectively. Extra demineralized beams were dehydrated and the initial dry mass (DM) was determined. All the beams were distributed into groups (n=10) and treated for 30 s or 60 s with: water, 0.5 M, 1 M or 2 M EDC or 10% glutaraldehyde (GA). After treatment, the new E and MMP activity were redetermined. The beams submitted to DM measurements were storage for 1 week in artificial saliva, after that the mass loss and HYP release were evaluated. The collagen thermal denaturation temperature (TDT) was determined by DSC analysis. Data for E, MMP activity and HYP release were submitted to Wilcoxon and Kruskal-Wallis or Mann-Whitney tests. Mass loss and TDT data were submitted to ANOVA and Tukey tests at the 5% of significance. RESULTS: EDC was able to significantly increase collagen stiffness in 60s. 10% GA groups obtained the highest E values after both 30 and 60s. All cross-linking agents decreased MMP activity and HYP release and increased TDT temperature. Significant differences were identified among EDC groups after 30 or 60 s of cross-linking, 1M or 2M EDC showed the lowest MMP activity. SIGNIFICANCE: Cross-linking agents are capable of preventing dentin collagen degradation. EDC treatment may be clinically useful to increase resin-dentin stability.