Effect of flavonoid incorporation in dentin adhesives on bond strength and quality of resin-dentin bonds on sound and caries-affected dentin.

• Grant number: 25/19316-5
• Support Opportunities: Regular Research Grants
• Start date: January 01, 2026
• End date: December 31, 2026
• 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
• City of the host institution: Araraquara
• Associated research grant: 25/02243-5 - Flavonoid-laden adhesive system for caries-affected dentin bonding: physicochemical, mechanical, and biological analyses, AP.R
• Associated scholarship(s): 26/00325-7 - Effect of flavonoid incorporation in dentin adhesives on bond strength and quality of resin-dentin bonds on sound and caries-affected dentin., BP.IC

Abstract

Caries-affected dentin (CAD) is the most frequent clinical substrate for adhesion. This substrate is characterized by a lower mineral content, higher amount of exposed collagen, higher water content, and higher proteolytic activity in comparison to sound dentin (SD). These features challenge adhesion to CAD, affecting the stability of the resin-dentin bond. Therefore, more studies evaluating new adhesive materials used in CAD and hybrid layer resistance to degradation are still necessary. The treatment of CAD with natural crosslinkers, such as certain flavonoids, before the adhesive procedure is a viable strategy for enhancing the longevity of resin-dentin bonds. It has been shown that the flavonoids improve collagen mechanical properties and inhibit endogenous proteases activity, turning the hybrid layer more resistant to both hydrolytic and matrix metalloproteinase (MMPs)- and cysteine cathepsins (CT)-mediated degradation. Flavonoid-containing solutions are applied as a pre-adhesive treatment as a separate step. However, incorporating these crosslinkers into the adhesive systems would reduce the technique's sensitivity and the number of clinical steps. Therefore, this study aims to investigate the effects of incorporating proanthocyanidins (GSE; grape seed extract) or quercetin (QU) in adhesive systems (self-etching and universal) on the immediate bond strength, quality of the marginal sealing, and proteolytic activity in interfaces produced on SD and CAD. Concentrations of QU (0.1 and 0.5%) and GSE (1 and 5%) will be incorporated into the components of Clearfil SE Bond (CSE) (only Primer, only Bond, and both) and into Single Bond Universal (SBU). Non-modified adhesives will serve as controls. Then, human molas will be collected, and sound or caries-affected flat dentin surfaces will be produced and treated with the adhesives. Immediate bond strength, Raman spectroscopy, and nanoinfiltration (n=8) will be performed to evaluate the quality of the interface and the adhesive mechanical resistance. For antiproteolytic activity analysis, the MMP-2 and -9 percentage of inhibition (n=5 for each MMP) will be evaluated. The number of biological repetitions (n) for each experimental protocol is based on previous studies. However, this number will be rechecked after the first experimental occasion (GPower), and if necessary, it will be adjusted. Data will be submitted to specific statistical analysis after verification of the type of sample distribution (Shapiro-Wilk test) and homogeneity of variances (Levene's test). Statistical decisions will be taken at the 5% level of significance. (AU)