Zirconia tetragonal polycrystals and doped by niobium oxide to reduce the effect of low-temperature degradation: fabrication of blocks and disks for CAD:CAM

• Grant number: 22/07559-2
• Support Opportunities: Research Grants - Innovative Research in Small Business - PIPE
• Duration: August 01, 2023 - April 30, 2024
• Field of knowledge: Health Sciences - Dentistry - Dental Materials
• Principal Investigator: Márcio Gomes Sabino
• Grantee: Márcio Gomes Sabino
• Host Company: Cer-Oss Pesquisa e Desenvolvimento em Biomateriais Ltda
• CNAE: Fabricação de produtos cerâmicos não-refratários não especificados anteriormente
• City: São Carlos

Abstract

Tetragonal zirconia polycrystals (3Y-TZP) is a bioceramic used in the manufacture of prostheses by CAD-CAM system and implants for Dentistry. Its use is due to its exceptional mechanical properties (compression/flexion/biaxial breaking strength and fracture toughness) and its biocompatibility. The discs are imported and have a high cost (R$ 1384.20/disc), and combined with the CAD-CAM machining and professional procedure expensive. However, despite the excellent mechanical properties, 3Y-TZP presented several ruptures in the Orthopedic area (femur head and acetabulum), and these ruptures are explained by a phenomenon called hydrothermal degradation and occur in the presence of moisture, inducing the transformation of the tetragonal phase into monoclinic with the volumetric expansion of 4-5% with the possible generation of microcracks and weakening the material. The degradation is related to the vacancy left by the stabilizing agent of the tetragonal phase trivalent yttrium oxide (Y2O3) and tetravalent zirconia. To solve this unbalance, the project aims to insert a pentavalent element in an appropriate amount to reduce the vacancy of oxygen and consequently the degradation. Evaluation of doping 3Y-TZP with niobium oxide (Nb2O5) for reducing degradation and propose a ceramic process scalable for the manufacture of 3Y-TZP and 3Y-TZP/xNb2O5 discs for CAD-CAM milling system used to manufacture prostheses on implants for use in oral rehabilitation in Dentistry. The nationalization of this technology will make it possible to obtain a material with the quality to that exists in the dental market. The preparation steps will follow a laboratory scale ceramic processing method, and the characterization comprises the determination of biaxial flexural strength, fracture toughness (KIc), and determination of the Weibull modulus (m), d) failure probability (Pf). The 3Y-TZP doped with Nb2O5 was evaluated against hydrothermal degradation at 3, 6, and 9 hours and its verification will be via X-ray diffractometry and quantification by Rietveld refinement. Samples with effective degradation reduction will be evaluated for element quantification by X-ray fluorescence spectroscopy and surface morphology by scanning electron microscopy. The final process is obtaining ceramic discs via uniaxial pressing and testing in a CAD-CAM system for validation. (AU)