Biomimetic remineralization of caries-affect dentin via polymer-induced liquid precursors (PILP) and effect on the quality and mechanical stability of resin-dentin bonds.

• Grant number: 22/07333-4
• Support Opportunities: Scholarships in Brazil - Master
• Effective date (Start): November 01, 2022
• Effective date (End): February 29, 2024
• Field of knowledge: Health Sciences - Dentistry - Dental Materials
• Principal Investigator: Josimeri Hebling Costa
• Grantee: Maria Luiza Barucci Araujo Pires
• Host Institution: Faculdade de Odontologia (FOAr). Universidade Estadual Paulista (UNESP). Campus de Araraquara. Araraquara , SP, Brazil

Abstract

Sound and pathologically modified dentin, such as eroded and caries-affected dentin, coexist as substrates for adhesive restorations. Most papers published in this area use sound dentin; however, the results seen for this substrate cannot be directly transferred to the modified substrates. Caries-affected dentin (CAD), for instance, has characteristics that lead to inferior bond strength when compared to the values obtained for sound dentin. One of such characteristics is its lower cohesive strength, since CAD is less mineralized, has greater porosity, greater water content, and increased proteolytic activity. Thus, restorative materials able to induce remineralization should be used over the CAD. Moreover, when CAD is conditioned with phosphoric acid as an adhesive strategy, the surface is depleted of minerals, including the minerals inside the collagen fibrils. In sound dentin, intrafibrillar minerals represent ~34% of the total mineral content of this substrate (the remaining 66% are in the extrafibrillar region) and play a pivotal role in the mechanical resistance of collagen fibrils. However, one of the challenges of dentin remineralization still to be overcome is the replenishment of the intrafibrillar mineral. To achieve that, the use of biomimetic analogs of non-collagenous dentin proteins (NCPs), via PILP (polymer induced liquid precursor), has been investigated. Briefly, such a process aims to keep nanometric amorphous calcium-phosphate crystals (ACP), in a liquid phase, which are conducted to the interior of collagen fibrils to occupy the spaces (~40 nm) between collagen molecules. Once inside the fibrils, the nanocrystals undergo maturation and fill the spaces, previously filled with water. This process occurs physiologically during dentinogenesis, and the NCPs have an important role in promoting and inhibiting mineral crystal growth. Therefore, the overall purpose of the present project is to evaluate the remineralizing potential of dentin NCPs biomimetic analogs, via PILP, applied to CAD and using the dentinal fluid as the sole source of Ca2+ and PO43- ions. Initially, a pilot study will be performed to validate the biological method to induce in vitro dentin caries by determining the mineral:organic matrix ratio of the dentin surface. Then, it will be investigated (1) the remineralizing potential of PILP solutions with polyacrylic acid (PAA) and sodium trimetaphosphate (STMP) as biomimetic analogs and a simulated body fluid (SBF) as ions source, and (2) the remineralization of CAD via PILP using PAA and STMP and the dentin fluid as ions source, and the effect of the process on the quality and stability of resin-dentin bonds. Sound human teeth will be collected and submitted to a biological protocol to induce dentin caries in vitro. PAA and SMTP, separately or in combination, will be selected as biomimetic analogs and an SBF will be used as an ion source, in a storage solution, or via dentin tubules (dentin fluid). Analysis in Fourier transform infrared (FTIR) and Raman spectroscopy (FTIR), microtensile bond strength (immediate and 6 months), and nanoleakage will be performed to respond to the project objectives. Data will be submitted to specific tests after checking data distribution and homoscedasticity, and the statistical inferences will be taken at the 5% level of significance.