Proanthocyanidin encapsulation for sustained bioactivity in dentin bioadhesion: A two-year study

Mechanistic study of the stabilization of dentin-bonded restorative interfaces via collagen reinforcement by multi-acrylamides

Hydrolytically and enzymatically-stable multi-acrylamides have been proposed to increase the long-term durability of dental adhesive interfaces as alternatives to methacrylates. The aim of this study was to investigate the mechanical and biochemical properties of experimental adhesives containing multi-functional acrylamides concerning collagen reinforcement and metalloproteinases (MMP) activity. Multi-functional acrylamides, TMAAEA (Tris[(2-methylaminoacryl) ethylamine) and DEBAAP (N,N-Diethyl-1,3-bis(acrylamido) propane), along with the commercially available DMAM (N,N-dimethylacrylamide) (monofunctional acrylamide) and HEMA (2-Hydroxyethyl methacrylate) (monofunctional methacrylate - control) were tested for stability against enzymatic hydrolysis by cholesterol esterase/pseudocholinesterase (PC/PCE) solutions for up to 30 days. Collagen-derived substrate and gelatin zymography were performed to examine the effect of the compounds on the biological activity of human recombinant and dentin-extracted gelatinases MMP-2 and MMP-9. In situ zymography was carried out by fluorescent collagen degradation combined with confocal microscopy analysis. Hydroxyproline content was measured in collagen derived from dentin extracts though reaction with Ehrlich's reagent p-dimethylaminobenzaldehyde (DMAB), generating a stable chromophore measured at 550 nm. Storage shear modulus of demineralized dentin discs treated with the tested compounds was measured by oscillatory rheometry, in order to investigate potential collagen reinforcement. FT-IR was performed to determine qualitative differences in collagen based on observed changes in amide bands. The results were analyzed by ANOVA/Tukey's test (α = 0.05). Multi-acrylamides survived 30 days of incubation in cholinesterase/pseudo-cholinesterase (PC/PCE) solutions, while HEMA showed approximately 70 % overall degradation. Incubation with multi-acrylamides reduced collagen degradation as evidenced by the reduced hydroxyproline levels and by the 30 % increase inshear storage modulus. Biochemical and zymography assays showed no noticeable inhibition of recombinant and extracted MMPs enzymatic activity. The infra-red spectroscopy results for multi-functional acrylamides treated samples demonstrated shifts of the amide II bonds and marked increase in intensity of the bands 1200 cm-1, which may indicate partial collagen denaturation and some degree of cross-linking of the compounds with collagen, respectively. The multi-acrylamides exhibited not only comparable mechanical properties but also demonstrated significantly enhanced biochemical stability when compared to the widely used methacrylate control. Clinical relevance: These findings highlight the potential of multi-acrylamides to increase the bonding stability to tissues and, ultimately, contribute to the longevity of dental restorations.

Flavonoids effects against bacteria associated to periodontal disease and dental caries: a scoping review

This scoping review focused on exploring the efficacy of flavonoids against bacteria associated with dental caries and periodontal diseases. Inclusion criteria comprise studies investigating the antibacterial effects of flavonoids against bacteria linked to caries or periodontal diseases, both pure or diluted in vehicle forms. The search, conducted in August 2023, in databases including PubMed/MEDLINE, Scopus, Web of Science, Embase, LILACS, and Gray Literature. Out of the initial 1125 studies, 79 met the inclusion criteria, majority in vitro studies. Prominent flavonoids tested included epigallocatechin-gallate, apigenin, quercetin, and myricetin. Predominant findings consistently pointed to bacteriostatic, bactericidal, and antibiofilm activities. The study primarily investigated bacteria associated with dental caries, followed by periodontopathogens. A higher number of publications presented positive antibacterial results against Streptococcus mutans in comparison to Porphyromonas gingivalis. These encouraging findings underline the potential applicability of commercially available flavonoids in materials or therapies, underscoring the need for further exploration in this field.

Development of Proanthocyanidin-Loaded Mesoporous Silica Nanoparticles for Improving Dental Adhesion

Dentin biomodification is a promising approach to enhance dental tissue biomechanics and biostability for restorative and reparative therapies. One of the most active dentin tissue biomodifiers is proanthocyanidin (PAC)-rich natural extracts, which are used in the dental bonding procedure in combination with resin-based adhesives (RBAs). This study aimed to investigate the use of mesoporous silica nanoparticles (MSNs) for the sustained delivery of PACs for dentin biomodification as a novel drug-delivery system for dental applications. The effects of the incorporation of MSN functionalized with 3-aminopropyltriethoxysilane (APTES) and loaded with PAC into an experimental RBA were assessed by characterizing the material mechanical properties. In addition, the immediate and long-term bonding performance of an experimental resin-based primer (RBP) containing MSN-APTES loaded with PAC was also evaluated. For that, different formulations of RBA and RBP were prepared containing 20% w/v MSN-APTES loaded with PAC before or after functionalization (MSN-PAC-APTES and MSN-APTES-PAC, respectively). The incorporation of MSN-APTES-PAC did not negatively impact the degree of conversion or the overall mechanical properties of the RBA. However, adding MSN-PAC-APTES resulted in inferior mechanical properties of the experimental RBA. In the adhesion studies, APTES-functionalized MSN was successfully added to an experimental RBP for drug-delivery purposes without compromising the bond strength to the dentin or the failure mode. Interestingly, the sequence of surface functionalization with APTES resulted in differences in the bonding performance, with better long-term results for RBP containing MSN loaded with PAC after functionalization.

Biodegradation of Dental Resin-Based Composite—A Potential Factor Affecting the Bonding Effect: A Narrative Review

In recent years, although resin composite has played an important role in the restoration of tooth defects, it still has several disadvantages, including being biodegraded by saliva, bacteria and other enzymes in the oral cavity, which may result in repair failure. This factor is not conducive to the long-term survival of the prosthesis in the mouth. In this article, we review the causes, influencing factors and prevention methods of resin biodegradation. Biodegradation is mainly caused by esterase in saliva and bacteria, which breaks the ester bond in resin and causes the release of monomers. The mechanical properties of the prosthesis can then be affected. Meanwhile, cathepsin and MMPs are activated on the bonding surface, which may decompose the dentin collagen. In addition, neutrophils and residual water on the bonding surface can also aggravate biodegradation. Currently, the primary methods to prevent biodegradation involve adding antibacterial agents to resin, inhibiting the activity of MMPs and enhancing the crosslinking of collagen fibers. All of the above indicates that in the preparation and adhesion of resin materials, attention should be paid to the influence of biodegradation to improve the prosthesis’s service life in the complex environment of the oral cavity.