Bovine hydroxyapatite bioceramics pressed and molded added with colloidal silica: microstructural and mechanical characterization

• Grant number: 24/09729-8
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: October 01, 2024
• End date: September 30, 2025
• Field of knowledge: Health Sciences - Dentistry - Dental Materials
• Principal Investigator: Ana Flávia Sanches Borges
• Grantee: Lucas Yoshizawa de Marins
• Host Institution: Faculdade de Odontologia de Bauru (FOB). Universidade de São Paulo (USP). Bauru , SP, Brazil

Abstract

This in vitro study aims to synthesize an experimental bioceramic composed of bovine- derived hydroxyapatite (HA) through two routes: pressed and molded, after the addition of colloidal silica (CS). The study will determine the appropriate sintering schemes and characterize these groups of experimental ceramics structurally, molecularly, and mechanically, comparing biaxial flexural strength (BFS) and fracture toughness by hardness, as well as evaluating the reliability of the two methods for obtaining the experimental ceramics through Weibull statistical analysis, comparing them with conventional zirconia (Y-TZP). Commercial specimens will be manufactured according to the ISO 6872:2015 standard for discs with a diameter of 12 mm and a thickness of 1.2 ± 0.2 mm and sintered according to the manufacturer's instructions (n=35). The HA will be extracted from bovine bones, repurposing these solid residues into a sustainable and low-cost material. The nanoparticulate HA will be uniaxially pressed (100MPa, 60sec) in a metallic mold into disc-shaped specimens (n=70). Half of these specimens will undergo isostatic pressing (200 MPa for 1 minute) (n=35). For the molded group, HA will be homogenized in a paddle mill (1000 rpm, 2min) with the slow addition of CS and polyethylene glycol dispersant (FS20). Four groups (n=35) will be formed, varying the proportion of CS and casting into molds according to ISO 6872:2015. The structural and molecular characterization of the experimental ceramics will be performed by X-ray Diffraction (XRD) and Scanning Electron Microscopy with energy-dispersive X-ray spectroscopy (SEM/EDS). Disc specimens for the biaxial flexural strength (BFS) test (n=30) and for the fracture toughness test using the indentation method (n=5) will be fabricated for each group. The data obtained will be subjected to ANOVA and Tukey tests in the case of parametric distribution, or to Kruskal-Wallis and Dunn tests in the case of non-parametric distribution, in addition to determining the Weibull distribution.