In vitro evaluation of the anti-proteolytic and cross-linking effect of mussel-inspired monomer on the demineralized dentin matrix

From medical strategy to foodborne prophylactic strategy: Stabilizing dental collagen with aloin

Infectious oral diseases are longstanding global public health concerns. However, traditional medical approaches to address these diseases are costly, traumatic, and prone to relapse. Here, we propose a foodborne prophylactic strategy using aloin to safeguard dental collagen. The effect of aloin on the stability of dental collagen was evaluated by treating dentin with a solution containing aloin (0.1 mg/mL) for 2 min. This concentration is comparable to the natural aloin content of edible aloe. Furthermore, we investigated the mechanisms underlying the interactions between aloin and dentin collagen. Our findings, obtained through fluorescence spectroscopy, attenuated total reflection Fourier transform infrared spectroscopy, Gaussian peak fitting, circular dichroism spectroscopy, and X-ray diffraction, revealed that aloin interacts with dental collagen through noncovalent bonding, specifically hydrogen bonding in situ. This interaction leads to a reduction in the distance between molecules and an increase in the proportion of stable α-helical chains in the dental collagen. The ultimate tensile strength and thermogravimetric analysis demonstrated that dental collagen treated with aloin exhibited improved mechanical strength and thermostability. Additionally, the release of hydroxyproline, cross-linked carboxy-terminal telopeptide of type I collagen, and C-terminal cross-linked telopeptide of type I collagen, along with weight loss, indicated an enhancement in the enzymatic stability of dental collagen. These findings suggest that aloin administration could be a daily, nondestructive, and cost-effective strategy for managing infectious oral diseases.

Tissue Stabilization, Bacterial Adhesion, and Stem Cell Viability in Trans-cinnamaldehyde-conditioned Dentin

INTRODUCTION

This laboratory study aimed to evaluate the effect of trans-cinnamaldehyde (TC) conditioning on dentin tissue stabilization, bacterial adhesion, and stem cell toxicity.

METHODS

Dentin beams (n = 204) from extracted human molars were demineralized in phosphoric acid and treated with TC (2.5, 5, and 7.5%), 50% ethanol-water mixture (vehicle control) or 2.5% glutaraldehyde (GA) (positive control) for 30 minutes. Demineralized but untreated specimens served as the negative control. After treatment, collagen crosslinking was characterized by measuring the elastic modulus (Er) and hardness (n = 5). Biodegradation resistance was examined by determining the loss of dry mass (n = 8), hydroxyproline release (n = 4) and scanning electron microscopy (n = 2), after exposure to bacterial collagenase. Inhibition of bacterial adhesion was investigated by colony counting assay (n = 12) and scanning electron microscopy (n = 2). Viability of stem cells of the apical papilla on TC-conditioned dentin was determined using the Cell Counting Kit-8 assay (n = 8). Data were statistically analyzed using one-way analysis of variance (ANOVA) test followed by Dunnett's multiple comparisons at a significance level of 5%.

RESULTS

TC-conditioned dentin showed a concentration-dependent increase in Er and hardness. The Er and hardness of 5% and 7.5% TC-conditioned dentin were significantly greater than that of the negative control and vehicle control groups (P < .05). There was no significant difference in the biodegradation resistance between GA and 5% TC-conditioned dentin (P > .05). TC-conditioned dentin showed a well-preserved collagen fibril network with clear cross-banding, comparable to GA-conditioned dentin. All concentrations of TC inhibited bacterial adhesion on dentin, significantly greater than the negative control (P < .05). There was no reduction in viability of stem cells of the apical papilla viability on TC-conditioned dentin compared to the negative control (P > .05).

CONCLUSIONS

TC conditioning stabilized the dentin and protected it from enzymatic degradation. TC prevented bacterial adhesion on the dentin but maintained stem cell viability.

Effect of collagen cross-linkers on dentin bond strength: A systematic review and network meta-analysis

Objective: This study aimed to evaluate the role of collagen cross-linkers in the bonding performance of the resin-dentin interface through a systematic review and a network meta-analysis. Sources: The literature search was conducted in several databases like PubMed, EMBASE, Cochrane, Scopus and Web of Science from their inception till 30 April 2022. Study selection: The inclusion criteria consisted of in vitro studies evaluating the micro-tensile and micro-shear bond strengths of different cross-linkers acting on dentin. Bayesian network meta-analysis was conducted using RStudio. Data: Out of the 294 studies evaluated in the full-text analysis, 40 were included in the systematic review and meta-analysis. Most studies have used cross-linkers as primer (65.1%), followed by incorporating them into in adhesives and acid etching agents. The application methods of the adhesive system were classified as "etch-and-rinse (ER) adhesives" (77%) and "self-etching (SE) adhesives". Moreover, there were six types of cross-linkers in this presented review, of which the most numerous were polyphenols. Conclusion: Different application methods of cross-linkers, the long-term results showed that were only effective when used for longer durations, the immediate results were not statistically different. According to immediate and long-term results, etch-and-rinse (ER) adhesives showed a greater bonding performance than the control groups (p ≤ 0.05), whereas self-etching (SE) adhesives showed similar bond strength values (p ≥ 0.05). The result of network meta-analysis (NMA) showed that Dope like compound showed higher long-term bonding performance than other cross-linkers. Clinical significance: Long-term clinical studies may be needed to determine the effect of the cross-linkers on the bonding properties.

Treated Dentin Matrix in Tissue Regeneration: Recent Advances

Tissue engineering is a new therapeutic strategy used to repair serious damage caused by trauma, a tumor or other major diseases, either for vital organs or tissues sited in the oral cavity. Scaffold materials are an indispensable part of this. As an extracellular-matrix-based bio-material, treated dentin matrixes have become promising tissue engineering scaffolds due to their unique natural structure, astonishing biological induction activity and benign bio-compatibility. Furthermore, it is important to note that besides its high bio-activity, a treated dentin matrix can also serve as a carrier and release controller for drug molecules and bio-active agents to contribute to tissue regeneration and immunomodulation processes. This paper describes the research advances of treated dentin matrixes in tissue regeneration from the aspects of its vital properties, biologically inductive abilities and application explorations. Furthermore, we present the concerning challenges of signaling mechanisms, source extension, individualized 3D printing and drug delivery system construction during our investigation into the treated dentin matrix. This paper is expected to provide a reference for further research on treated dentin matrixes in tissue regeneration and better promote the development of relevant disease treatment approaches.

Enhancing resin-dentin bond durability using a novel mussel-inspired monomer

Numerous approaches have been developed to improve the resin-dentin bond performance, among which the bio-application of mussel-derived compounds have drawn great attention recently. To assess the performance of N-(3,4-dihydroxyphenethyl)methacrylamide (DMA), a mussel-derived compound, as a functional monomer in dental adhesive, its potential property to cross-link with dentin collagen and polymerize with adhesive will first be evaluated by transmission electron microscopy (TEM), attenuated total reflectance technique of Fourier transform infrared (ATR-FTIR), and atomic force microscopy (AFM) via Peakforce QNM mode. After validating the influence of DMA on collagen and adhesive separately, the overall performance of DMA/ethanol solution as a primer in dentin bonding was examined using micro-tensile bond strength (μTBS) testing, fracture pattern observation, and nanoleakage evaluation both immediately and after 10,000 times thermocycling aging. The inhibitory effect of DMA on endogenous metalloproteinases (MMPs) was evaluated by in situ zymography using confocal laser scanning microscopy (CLSM) and the cytotoxicity of DMA was evaluated using cell counting kit-8. Results demonstrated that DMA successfully cross-linked with dentin collagen via non-covalent bonds and had no influence on the polymerization and mechanical properties of the adhesive. Furthermore, even after 10,000 times thermocycling aging, the μTBS and nanoleakage expression of the DMA-treated groups showed no significant change compared with their immediate values. In situ zymography revealed reduced endogenous proteolytic activities after the application of DMA, and no cytotoxicity effect was observed for DMA concentration up to 25 ​μmol/L. Thus, DMA could be used as a novel, biocompatible functional monomer in dentin bonding.

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DMA acts as a functional monomer in dentin bonding system with high biocompatibility.

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DMA connects the adhesive and collagen network to resist various external attacks.

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DMA/ethanol inhibits the activity of MMPs and improve resin-dentin bond durability.