Mitigation of powder compaction defects in dental yttria-stabilized zirconia for improved reliability

• Grant number: 22/08594-6
• Support Opportunities: Scholarships abroad - Research Internship - Doctorate
• Effective date (Start): January 06, 2023
• Effective date (End): January 05, 2024
• Field of knowledge: Health Sciences - Dentistry - Dental Materials
• Principal Investigator: Gilmar Patrocínio Thim
• Grantee: Raíssa Monteiro Pereira
• Supervisor: Ulrich Lohbauer
• Host Institution: Divisão de Engenharia Mecânica (IEM). Instituto Tecnológico de Aeronáutica (ITA). Ministério da Defesa (Brasil). São José dos Campos , SP, Brazil
• Research place: Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Germany
• Associated to the scholarship: 21/05217-4 - Mechanical and optical characterization of the experimental fourth generation multilayer zirconia Y-TZP interface for dental applications, BP.DR

Abstract

Zirconia Y-TZP has been the most promising material in dental prosthodontics. Nonetheless, limitations persist despite intensive developments in powder technology. Current monolithic zirconia presents agglomerated particles that leave unfilled interstices behind, the origin of "Mercedes-Benz stars" after pre-sintering and high-temperature sintering. Such defects are responsible for severe drops in mechanical properties such as flexural strength. The consequence is the shortening of zirconia restorations clinical lifetime as well any other piece made of ceramic including implants and prostheses. This project aims to tackle this problem by tailoring the particle size distribution of the raw powder so to close the gap between vacant interparticle voids. For that purpose, commercial powders will be sieved to obtain the particle size distribution. In combination with the original distribution, narrow size ranges of sieved particles will be added to obtain a bimodal/multimodal size distribution. The compositions obtained will be pressed uniaxially and cold-isostatically for subsequent sintering. Dilatometry experiments will be conducted to define the appropriate sintering parameters. Finally, uniaxial and biaxial flexural tests will be performed with varying specimens' sizes to probe the Weibull size effect on strength, with accompanying fractographic analysis. We expect to substantially shift the critical size of particle distribution towards lower sizes and homogenize the scatter in strength, ultimately increasing the Weibull parameters and the clinical reliability of this material class. (AU)