Characterization of the biochemical and viscoelastic properties of the adhesive interface in dentin treated with bromelain associated with bioactive glass-ceramic

• Grant number: 22/12244-0
• Support Opportunities: Scholarships abroad - Research Internship - Doctorate
• Start date: July 01, 2023
• End date: June 30, 2024
• Field of knowledge: Health Sciences - Dentistry - Dental Materials
• Principal Investigator: Fernanda de Carvalho Panzeri
• Grantee: Rocio Geng Vivanco
• Supervisor: Ana Karina Barbieri Bedran-Russo
• Host Institution: Faculdade de Odontologia de Ribeirão Preto (FORP). Universidade de São Paulo (USP). Ribeirão Preto , SP, Brazil
• Institution abroad: Marquette University, United States
• Associated to the scholarship: 19/24922-0 - Effect of the use of Bromelain associated to bioactive glass-ceramic on dentin/adhesive interface, BP.DR

Abstract

The incomplete removal of the smear layer observed with self-etch adhesives systems may negatively affect hybridization. Studies have shown an increase in bond strength after complete removal with deproteinizing agents. Bromelain has been proposed as a natural alternative depicting favorable results when applied before etch-and-rinse adhesive systems. The use of remineralizing agents has also been studied aiming to increase the longevity of adhesive restorations. Biosilicate can reduce the activity of endogenous proteases and increase the bond strength of self-etch adhesive systems to sound and caries-affected dentin. Its association with natural substances has shown interesting results. The proponent's doctoral research evaluated the effect of bromelain and Biosilicate on the bond strength of a universal adhesive system applied in self-etch mode to sound and caries-affected dentin, showing promising results. However, bond strength assay has its limitations. The analysis of the biochemical and viscoelastic properties of biomodified dentin and the viscoelastic behavior of the components of the adhesive interface would contribute to the interpretation of the previous results. The present study aims to evaluate the long-term effect of bromelain associated with Biosilicate on the biochemical and viscoelastic properties of sound and caries-affected dentin, and on the viscoelastic properties of the components of the adhesive interface. Mid-coronal dentin discs will be obtained from sound extracted human molars (2 mm-thick), embedded in epoxy resin, and polished. Half of them will be submitted to formation of caries by biological model with S. mutans strain ATCC25175. Specimens will be then randomly separated into 4 groups (n = 5), according to the treatment received: Control Group - Adhesive System; Br Group - 5% Bromelain extract; Bio Group - 10% Biosilicate suspension; BrBio Group - Br + Bio. The chemical composition of treated samples will be assessed via micro-Raman spectroscopy (XploRA Plus, Horiba Scientific) after 24 hours and 6 months of storage in simulated body fluids at 37 °C. Raman peaks will be used to analyze the mineral and organic content of the dentin before and after biomodification. The viscoelastic properties of sound and caries-affected dentin will be determined by dynamic-mechanical analysis at nanoscale (nano-DMA) using a TI980 nanoindenter (Hysitron Bruker) before and after dentin biomodification. The nanomechanical properties [complex modulus (E*), storage modulus (E'), loss modulus (E") and the damping capacity (tan ´)] will also be obtained. Nano-DMA will be performed to evaluate the viscoelastic properties of the components of the dentin-resin interface. The occlusal-third of sound human molars will be removed to expose a flat dentin surface, and half of them will be submitted to artificial caries process. The teeth will be then randomly separated into the described groups. After treatments, two layers of adhesive system (Single Bond Universal, 3M ESPE) will be applied and then, resin composite (Filtek Z350XT, 3M ESPE) build-ups will be constructed (2 mm-thick). Samples will be sectioned into sticks of 2 mm2 (n = 5), embedded in epoxy resin and polished. The viscoelastic properties of the components of the adhesive interface will be determined after 24 hours and 6 months. Data will be analyzed according to the most appropriate statistical test. (AU)