Methacrylate-functionalized proanthocyanidins as novel polymerizable collagen cross-linkers - Part 2: Effects on polymerization, microhardness and leaching of adhesives

Effects on dentin nanomechanical properties, cell viability and dentin wettability of a novel plant-derived biomodification monomer

OBJECTIVES

To evaluate the effects of dentin biomodification agents (Proanthocyanidin (PAC), Cardol (CD) and Cardol-methacrylate (CDMA) on dentin hydrophilicity by contact angle measurement, viability of dental pulp stem cells (DPSCs) and nanomechanical properties of the hybrid layer (HL).

METHODS

CDMA monomer was synthesized from cardol through methacrylic acid esterification. Human extracted third molars were used for all experiments. For nanomechanical tests, specimens were divided in four groups according to the primer solutions (CD, CDMA, PAC and control) were applied before adhesive and composite coating. Nanomechanical properties of the HL were analyzed by nanoindentation test using a Berkovich probe in a nanoindenter. Wettability test was performed on dentin surfaces after 1 min biomodification and measured by contact angle analysis. Cytotoxicity was assessed by a MTT assay with DPSCs after 48 and 72 h. Data were analyzed with Student's t test or Two-way ANOVA and Tukey HSD test (p < 0.05).

RESULTS

CD and CDMA solutions achieved greater hydrophobicity and increased the water-surface contact angles when compared to PAC and control groups (p < 0.05). PAC group showed a greater reduction of elastic modulus in nanoindentation experiments when compared to CD and CDMA groups (p < 0.05) after 4 months of aging. CD inhibited cell proliferation compared to all further materials (p < 0.05), whilst CDMA and PAC indicated no cell cytotoxicity to human DPSCs.

SIGNIFICANCE

Cardol-methacrylate provided significantly higher hydrophobicity to dentin and demonstrated remarkable potential as collagen crosslinking, attaining the lowest decrease of HL's mechanical properties. Furthermore, such monomer did not affect pulp cytotoxicity, thereby highlighting promising feasibility for clinical applications.

Effect of Collagen Crosslinkers on Dentin Bond Strength of Adhesive Systems: A Systematic Review and Meta-Analysis

This study aimed to identify the role of crosslinking agents in the resin–dentin bond strength (BS) when used as modifiers in adhesives or pretreatments to the dentin surface through a systematic review and meta-analysis. This paper was conducted according to the directions of the PRISMA 2020 statement. The research question of this review was: “Would the use of crosslinkers agents improve the BS of resin-based materials to dentin?” The literature search was conducted in the following databases: Embase, PubMed, Scielo, Scopus, and Web of Science. Manuscripts that reported the effect on the BS after the use of crosslinking agents were included. The meta-analyses were performed using Review Manager v5.4.1. The comparisons were performed by comparing the standardized mean difference between the BS values obtained using the crosslinker agent or the control group. The subgroup comparisons were performed based on the adhesive strategy used (total-etch or self-etch). The immediate and long-term data were analyzed separately. A total of 50 articles were included in the qualitative analysis, while 45 articles were considered for the quantitative analysis. The meta-analysis suggested that pretreatment with epigallocatechin-3-gallate (EGCG), carbodiimide, ethylenediaminetetraacetic acid (EDTA), glutaraldehyde, and riboflavin crosslinking agents improved the long-term BS of resin composites to dentin (p ≤ 0.02). On the other hand, the use of proanthocyanidins as a pretreatment improved both the immediate and long-term BS values (p ≤ 0.02). When incorporated within the adhesive formulation, only glutaraldehyde, riboflavin, and EGCG improved the long-term BS to dentin. It could be concluded that the application of different crosslinking agents such as carbodiimide, EDTA, glutaraldehyde, riboflavin, and EGCG improved the long-term BS of adhesive systems to dentin. This effect was observed when these crosslinkers were used as a separate step and when incorporated within the formulation of the adhesive system.

Mussel-inspired monomer - A new selective protease inhibitor against dentine collagen degradation

OBJECTIVES

To evaluate the inhibitory effect of a novel mussel-inspired monomer (N-(3,4-dihydroxyphenethyl)methacrylamide (DMA) on the soluble and matrix-bound proteases.

METHODS

The inhibitory effect of DMA (0, 1, 5, and 10 mM) and 1 mM chlorhexidine (CHX) dissolved in 50% ethanol/water on soluble recombinant human matrix metalloproteinases (rhMMP-2, -8, and -9), as well as cysteine cathepsins (B and K) were evaluated using both fluorometric assay kits and molecular docking. The effect of CHX and DMA on matrix-bound proteases was examined by in situ zymography, and the fluorescence intensity and relative area were calculated by Image J software. All data obtained were analyzed by one-way ANOVA followed by Tukey test (α = 0.05).

RESULTS

The anti-proteolytic ability of DMA increased in a dose-dependent manner except that of rhMMP-9. Inhibitory effect of 1 mM DMA against rhMMP-2, - 8, - 9, as well as cathepsin B and K was all significantly lower than 1 mM CHX (p < 0.05). The molecular docking analysis was in good agreement with the experimental results, that the binding energy of DMA was lower than CHX for all proteases. In situ zymography revealed that all DMA- and CHX-treated groups significantly inactivated the matrix-bound proteases, with a dramatic reduction of the fluorescence intensity and relative area compared with the control group (p < 0.05).

SIGNIFICANCE

Under the prerequisite condition that the overall inhibitory performance on matrix-bound proteases was comparable by DMA and CHX, the more selective property of DMA could avoid inducing potential negative effects by suppressing MMP-9 when applied in dental treatment compared with CHX.

Procyanidins and Their Therapeutic Potential against Oral Diseases

Procyanidins, as a kind of dietary flavonoid, have excellent pharmacological properties, such as antioxidant, antibacterial, anti-inflammatory and anti-tumor properties, and so they can be used to treat various diseases, including Alzheimer’s disease, diabetes, rheumatoid arthritis, tumors, and obesity. Given the low bioavailability of procyanidins, great efforts have been made in drug delivery systems to address their limited use. Nowadays, the heavy burden of oral diseases such as dental caries, periodontitis, endodontic infections, etc., and their consequences on the patients’ quality of life indicate a strong need for developing effective therapies. Recent years, plenty of efforts are being made to develop more effective treatments. Therefore, this review summarized the latest researches on versatile effects and enhanced bioavailability of procyanidins resulting from innovative drug delivery systems, particularly focused on its potential against oral diseases.