Development of self-etching adhesive systems combined with bioactive particles containing fluoride and strontium with or without sodium and zinc: analysis of adhesive properties and remineralization of the dentin matrix

• Grant number: 23/16722-7
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• Start date until: September 01, 2024
• End date until: August 31, 2026
• Field of knowledge: Health Sciences - Dentistry - Dental Materials
• Principal Investigator: Linda Wang
• Grantee: Victor Mosquim
• Host Institution: Faculdade de Odontologia de Bauru (FOB). Universidade de São Paulo (USP). Bauru , SP, Brazil

Abstract

Adhesive systems enriched with bioactive particles may present benefits besides the bonding potential, as they enable an increase in local pH and mineral precipitation. In silicate-based bioactive glasses, the presence of fluoride can allow the production of fluorapatite (FAP), and strontium can facilitate the degradation of the glass in an aqueous medium and has a synergistic effect with fluoride, improving the mineral precipitation. The presence of sodium is also common in these glasses, but its hygroscopic characteristic can accelerate the process of hydrolytic degradation of monomers. Thus, preparing sodium-free glass can improve the performance of these adhesives. A combination of adhesive systems with bioactive particles can also remineralize dentin and reinforce the collagen matrix, reducing the action of matrix metalloproteinases (MMPs) on exposed collagen, especially zinc-containing glasses, preserving bond strength over time. Therefore, the objective of this study is to manufacture silicate-based bioactive glasses containing or not sodium and/or zinc with different concentrations of fluoride and strontium and characterize them in terms of their bioactivity in Tris and artificial saliva. Thereafter, this study will incorporate these glasses and two commercial bioactive particles (Biomin F and S-PRG) into experimental two-step self-etching adhesive systems and evaluate their interaction with dentin through microtensile bond strength, degree of conversion (DC), wetting, antiproteolytic activity by in situ zymography and remineralization capacity in Tris and artificial saliva. To achieve this, the glasses will be manufactured using the melt-quench method and characterized by X-ray diffraction and Fourier transform infrared spectroscopy (FTIR) before and after immersion in Tris and artificial saliva. Then, these manufactured glasses, Biomin F glass or an S-PRG particle will be added to the adhesives, which will be evaluated for the DC by FTIR and applied to dentin specimens for bond strength analyzes (n = 10/group) after 24h and 6 and 12 months in artificial saliva. An analysis of the fracture mode of the beams will also be carried out. The wetting will be measured with a goniometer through the contact angle (n = 6/group) between the adhesive and the dentin treated with acid primer. Then, the dentin specimens will be demineralized and placed in contact with the already polymerized adhesives, immersed in Tris and artificial saliva and analyzed for the dentin remineralization capacity by FTIR after 24 hours, 7 days, 2 months and 6 months. The MMPs activity will be analyzed at baseline and after 6 months by in situ zymography with confocal laser electron microscopy. Data from the microtensile test and in situ zymography will be subjected to 2-way ANOVA and post-hoc Tukey tests. DC and wetting data will be subjected to ANOVA and post-hoc Tukey or Kruskal-Wallis and post-hoc Dunn tests. The alpha value will be set at 0.05 for all tests.