Inhibitory effect of curcuminoid pretreatments on endogenous dentin proteases

Effect of dentin biomodification using natural collagen cross-linkers on the durability of the resin-dentin bond and demineralized dentin stiffness

OBJECTIVE

The purpose of this study was to evaluate the effect of using natural cross-linkers as sumac and curcumin on the durability of the resin-dentin bond and stiffness of demineralized dentin matrix.

METHODS

Thirty sound molars were divided into 5 groups: Control (CO), Grape Seed extract (GSE), Cacao seed extract (CSE), Sumac extract (SE) and Curcumin extract (CE). The teeth had their coronal dentin exposed, etched, and pre-treated for 1 min with the extracts. Teeth were then bonded using Single-Bond II adhesive and 4 mm composite was built up on dentin surface. Teeth were sectioned into 1 × 1 × 8mm beams and their micro-tensile bond strength (μTBS) was tested after 24 h and 6 months of water storage. For stiffness testing, 15 teeth were sectioned to obtain dentin beams (1 × 1 × 6.5 mm), the beams were demineralized in 10% phosphoric acid then rinsed and divided into 5 groups. Beams were then immersed in their respective extract solution for 1 min after which they were subjected to a 3- point loading test using a universal testing machine to calculate their modulus of elasticity.

RESULTS

After 24 h, no significant difference in μTBS was shown between all groups. After 6 Months, GSE, CE, and SE showed significantly higher μTBS compared to CO (p ≥ 0.05). For the modulus of elasticity; only GSE showed a significantly higher modulus compared to other groups.

CLINICAL RELEVANCE

The application of grape seed extract, curcumin and sumac extract as dentin pre-treatments appear to be a promising approach to enhance the durability of the resin-dentin bond in a clinically relevant application time.

Evaluation of Chitosan-Oleuropein Nanoparticles on the Durability of Dentin Bonding

Purpose

To evaluate the effects of dentin pretreatment with chitosan-loaded oleuropein nanoparticles (CONPs) on the durability of resin-dentin bonding interfaces.

Methods

Eighty freshly extracted non-carious human third molars were randomly divided into four groups (n = 20 each): a de-ionized water (DW) group, a chitosan (CS) group, a chlorhexidine (CHX) group and a CONP group. The dentin in the DW, CS, CHX, and CONP groups were pretreated with de-ionized water, 1.0 mg/L CS solution, 2% chlorhexidine solution, and CONP suspension (prepared with 100 mg/L oleuropein), respectively, followed by the universal adhesive and resin composites. The bonded teeth of each group were randomly divided into two subgroups: an immediate subgroup and an aged subgroup. The bonded teeth of each group were then cut into the bonded beams. We measured their microtensile bond strength (μTBS), observed the characteristics of bonding interface by atomic force microscope, calculated the percentage of silver particles in a selected area for interfacial nanoleakage analysis, and evaluated the endogenous gelatinase activity within the bonding interface for in-situ zymogram analysis. Data were analyzed with two-way ANOVA and LSD multiple comparison test (P < 0.05).

Results

Regardless of after 24 h or after thermocycling, CONP exhibited better μTBS (P < 0.05) than the other three groups except that there was not a statistical significance (P > 0.05) in the CONP and CHX groups after 24 h. Besides, the CONP group presented significantly higher modulus of elasticity in the hybrid layers (P < 0.05), lower expression of nanoleakage (P < 0.05), and better inhibitory effect of matrix metalloproteinases than the other three groups before and after thermocycling.

Conclusion

Altogether, the CONPs had the potential to act as a dentin primer, which could effectively improve the dentin-resin binding durability.

Long-term effect of curcuminoid treatment on resin-to-dentin bond strength

Endogenous dentin proteases contribute to the degradation of collagen fibrils in the hybrid layer. Recently, inhibition of host-derived proteases by curcuminoids has shown promising results. The aim of this study was to evaluate the effect of curcuminoid treatment on the microtensile bond strength (μTBS) after 24 h or 12 months of storage. Fifty-four extracted sound human molars were flattened to mid-coronal dentin and divided into nine groups. After phosphoric acid-etching for 15 s, the dentin was experimentally treated for 60 s using 100 μM or 200 μM of curcumin, diflourobenzocurcumin, or demethoxycurcumin dissolved in 1% and 2% dimethyl sulfoxide (DMSO)/water solutions. Untreated and DMSO-treated groups served as controls. After bonding agent application, each tooth was restored with dental composite. The molars were sectioned into 0.9 × 0.9 × 6 mm beams. The μTBS testing was performed after 24 h and 12 months of storage in artificial saliva. Data were analyzed using regression analyses. Failure patterns were evaluated using scanning electron microscopy. Dentin treatment with curcuminoids did not adversely affect 24-h μTBS compared to controls. After 12 months, the μTBS of curcuminoid groups was statistically significantly higher than the controls. This study indicates the feasibility of using curcuminoids as protease inhibitors.

Effect of Curcumin Suspension and Vitamin C on Dentin Shear Bond Strength and Durability. A Pilot Study

Background:

Preserving the strength and durability of dentin bonds is a concern of dental researchers and practitioners.

Objective:

The aim of this study was to investigate the effect of treating etched dentin with vitamin C and curcumin suspension as cross-linking agents on the shear bond strength and durability of a universal dental adhesive.

Methods:

Extracted human third molar teeth were collected. Fifty-six flat coronal dentin surfaces were divided equally into four groups: (1) treated with adhesives; (2) etched with 37% H3PO4 for 10s before application of adhesives; (3) same as group (2), but with dentin treated with 2.5% curcumin suspension for 60s before the application of adhesive; and (4) same as group (3), but with the use of a 20% vitamin C suspension instead of a curcumin suspension. Filtek Z350XT composite was built for all samples. Half of the samples in each group were subjected to thermocycling. Shear bond strength was measured using a universal testing machine. Scanning electron microscopy was used to investigate the dentinal surfaces after treatment.

Results:

Treatment with curcumin suspension preserved immediate and long-term bond strength. Conversely, treatment of etched dentin with vitamin C solution significantly reduced the immediate bond strength, but a significant improvement was observed after aging. SEM showed that both cross-linking agents resulted in narrowing or closing of the dentinal tubules, with an adhesive mode of failure.

Conclusion:

The application of curcumin or vitamin C suspension to acid-etched dentin resulted in different effects on immediate and long-term shear bond strength when using universal adhesives.

Quercetin as an Auxiliary Endodontic Irrigant for Root Canal Treatment: Anti-Biofilm and Dentin Collagen-Stabilizing Effects In Vitro

Bacterial reinfection and root fracture are the main culprits related to root canal treatment failure. This study aimed to assess the utility of quercetin solution as an adjunctive endodontic irrigant that does not weaken root canal dentin with commitment anti-biofilm activity and bio-safety. Based on a noninvasive dentin infection model, dentin tubules infected with Enterococcus faecalis (E. faecalis) were irrigated with sterile water (control group), and 0, 1, 2, 4 wt% quercetin-containing ethanol solutions. Live and dead bacteria percentages in E. faecalis biofilms were analyzed by confocal laser scanning microscopy (CLSM). Elastic modulus, hydroxyproline release and X-ray photoelectron spectroscopy (XPS) characterization were tested to evaluate the irrigants’ collagen-stabilizing effect. The cytotoxicity was tested by CCK-8 assay. Quercetin increased the proportion of dead bacteria volumes within E. faecalis and improved the flexural strength of dentin compared to control group (p < 0.05). Quercetin-treated dentin matrix had less elasticity loss and hydroxyproline release after collagenase degradation (p < 0.05). Moreover, quercetin solutions revealed an increase in the C-O peak area under both C1s and O1s narrow-scan spectra of XPS characterization, and no cytotoxicity (p > 0.05). Quercetin exhibited anti-biofilm activity, a collagen-stabilizing effect with cytocompatibility, supporting quercetin as a potential candidate for endodontic irrigant.