Effects of acid etching and adhesive treatments on host-derived cysteine cathepsin activity in dentin.

PURPOSE: To analyze the effects of different processes during bonding on endogenous cysteine cathepsin activity in dentin. MATERIALS AND METHODS: Dentin powder, prepared from extracted human third molars, was divided into 10 groups. Two lots of dentin powder were used to detect the effects of the procedure of protein extraction on endogenous cathepsin activity. The others were used to study effects of different acid-etching or adhesive treatments on enzyme activity. Concentrations of 37% phosphoric acid or 10% phosphoric acid, two etch-and-rinse adhesive systems, and two self-etching adhesive systems were used as dentin powder treatments. The untreated mineralized dentin powder was set as the control. After treatment, the proteins of each group were extracted. The total cathepsin activity in the extracts of each group was monitored with a fluorescence reader. RESULTS: In the control group, there were no significant differences in cathepsin activity between the protein extract before EDTA treatment and the protein extract after EDTA treatment (p > 0.05). The cathepsin activities of the three different extracts in the 37% phosphoric acid-treated group were different from each other (p < 0.05). The two acid-etching groups and two etch-and-rinse groups showed significant enzyme activity reduction vs the control group (p < 0.05). There were no significant differences between those four groups (p > 0.05). Treating the dentin powder with any of the two self-etching adhesives resulted in an increase in cathepsin activity (p < 0.05). CONCLUSIONS: The activity of cysteine cathepsins can be detected in dentin powder. Treatment with EDTA during protein extraction exerted an influence on cathepsin activity. Acid etching or etch-and-rinse adhesive systems may reduce the activity of endogenous cathepsins in dentin. Self-etching adhesive systems may increase the enzyme activity.

[Effect of baicalein and quercetin on enzymatic resistance of dentin collagen].

OBJECTIVE: To investigate the effect of baicalein and quercetin on the enzymatic resistance of dentin matrix collagen. METHODS: Baicalein, quercetin and proanthocyanidin were dissolved in 20% dimethyl sulfoxide (DMSO) ethanol and prepared into pretreatment agents with a concentration of 50 g/L. Demineralized dentin specimens were prepared and immersed in pretreatment agents at 37 °C for 24 h, then they were digested in solution containing type?collagenase. The pretreatment agents of blank control group and negative control group were 20% DMSO ethanol, blank control group were digested in solution without collagenase. The ultimate tensile strength (UTS) and the hydroxyproline content of enzymolysis liquid in each group were measured respectively after collagenase digestion for 24 h, the dentin collagen morphology were observed under a field emission scanning electron microscopic (FE-SEM) after collagenase digestion for 12 h. RESULTS: After collagenase digestion for 24 h, the baicalein group had the highest UTS [(16.00±1.31) MPa], followed by proanthocyanidin group [(12.64±0.91) MPa], blank control group [(7.84±1.18) MPa], quercetin group [(3.20±1.07) MPa], and negative control group (0 MPa). Significant differences were detected among the UTS in each two group (P < 0.01). The hydroxyproline content in blank control group was the lowest [(0.40 ± 0.16) mg/L], followed by baicalein group[(2.95 ± 0.18) mg/L], proanthocyanidin group [(4.78±0.38) mg/L], quercetin group[(28.22±1.53) mg/L], and negative control group [(34.39±0.39) mg/L]. There were significant differences among the hydroxyproline contents in each group (P < 0.01). After collagenase digestion for 12 h, intact collagen network could be seen in blank control group under a FE-SEM. Collagen network in negative control group suffered nearly complete destruction and collapsed. In quercetin group, most of collagen collapsed. In proanthocyanidin group, a small portion of collagen destruction and collapse could be seen. In baicalein group, collagen network remained intact. CONCLUSIONS: The use of baicalein and quercetin could improve enzymatic resistance of dentin matrix collagen at a concentration of 50 g/L. The effect of baicalein was better than that of proanthocyanidin while the effect of quercetin was weaker than that of proanthocyanidin.