Flavonoid-laden adhesive system for caries-affected dentin bonding: physicochemical, mechanical, and biological analyses

• Grant number: 25/02243-5
• Support Opportunities: Regular Research Grants
• Start date: July 01, 2025
• End date: June 30, 2028
• Field of knowledge: Health Sciences - Dentistry - Dental Materials
• Principal Investigator: Josimeri Hebling Costa
• Grantee: Josimeri Hebling Costa
• Host Institution: Faculdade de Odontologia (FOAr). Universidade Estadual Paulista (UNESP). Campus de Araraquara. Araraquara , SP, Brazil
• Associated researchers: Carlos Alberto de Souza Costa

Abstract

Caries-affected dentin (CAD) is frequently the available substrate for clinical adhesion, highlighting the need to explore adhesive materials and strategies for stabilizing the interface between these materials and CAD. Furthermore, CAD is less mineralized, more porous, has greater collagen exposure, higher water content, and increased proteolytic activity compared to sound dentin, challenging both the immediate adhesion of resin-based materials and the long-term stability of the resin-dentin bond. The use of naturally formed in vivo CAD, although viable, incorporates important variables that are difficult to control, such as the degree of dentin involvement, lesion depth, and available adhesion area. In this context, the development of dentinal caries through laboratory models has been investigated to make in vitro studies more representative of clinical conditions. Additionally, treating CAD with natural cross-linkers, such as certain flavonoids, before adhesive procedures has proven to be a promising strategy for enhancing the longevity of adhesive interfaces. Studies indicate that these agents improve the mechanical properties of collagen and inhibit the action of endogenous proteases, increasing the hybrid layer's resistance to hydrolytic and enzyme-mediated degradation. Incorporating flavonoids into adhesive systems could reduce technique sensitivity and clinical steps. Moreover, due to their antimicrobial activity, flavonoids could provide protective effects against the detrimental impact of marginal infiltration by microorganisms. Thus, this study aims to investigate the effects of flavonoid incorporation into adhesive systems (self-etch and universal) on their physicochemical properties, the stabilization of adhesive interfaces in CAD obtained through a laboratory-induced protocol, as well as their antibacterial, anti-proteolytic, and cytotoxic activities. The project consists of three sequential phases. In the first phase, different in vitro dentinal caries production protocols will be compared through physicochemical and mechanical characterization of the substrates obtained before and after selective removal of carious tissue, compared to naturally occurring CAD. Analyses will include mineral-to-organic matrix ratio, mineral quality, collagen maturity, hardness, transverse elastic modulus, and morphology. In the second phase, a screening of different flavonoid concentrations incorporated into adhesive systems (self-etch and universal) will be conducted to evaluate their effects on physicochemical properties, mechanical stability, marginal seal quality, and the proteolytic activity of the resin-dentin bond produced by these materials on CAD obtained through the laboratory-induced protocol. In the third phase, the antibacterial activity of the adhesives against S. mutans, the anti-proteolytic activity on matrix metalloproteinases present in dentin, and the transdentinal cytotoxicity and bioactivity of the formulations will be assessed. The number of repetitions for each protocol was initially based on previous studies and will be recalculated according to data obtained in the first experimental stage, with adjustments as necessary. Data will be subjected to specific statistical analyses after verifying sample distribution type (Shapiro-Wilk) and variance homogeneity (Levene). Statistical inferences will be made considering a 5% significance level. (AU)