Analysis of mechanical, microbiological behavior and life in fatigue of zirconia abutments with silver glass

• Grant number: 21/03878-3
• Support Opportunities: Scholarships in Brazil - Doctorate
• Effective date (Start): August 01, 2021
• Effective date (End): March 31, 2026
• Field of knowledge: Health Sciences - Dentistry - Dental Materials
• Principal Investigator: Renata Marques de Melo Marinho
• Grantee: Ana Carolina da Silva
• Host Institution: Instituto de Ciência e Tecnologia (ICT). Universidade Estadual Paulista (UNESP). Campus de São José dos Campos. São José dos Campos , SP, Brazil
• Associated scholarship(s): 23/03271-7 - Fatigue life analysis of ultra-translucent zirconia crowns coated by antimicrobial glasses, BE.EP.DR

Abstract

In two-stage implant systems, the prosthetic abutment is retained to the implant through fixation, which may generate a micro-gap between the abutment and the implant. This crack may be favorable to bacterial colonization, affecting the mucous seal and, consequently, causing peri-implantitis. Within this perspective, this study intends to develop an antimicrobial agent (glass with silver) that is applied on the surface of the emergency profile of zirconia abutments so that the bacteria in the oral environment do not penetrate the region of the abutment/implant interface. The objective of this study will be analyze the mechanical and microbiological properties of zirconia discs and pillars with silver glass. The groups of this study will consist by: YZ + glaze (commercial), YZ + bcasol (bioglass of sodium lime), YZ + Ag 5%, YZ + Ag 10%. Colony Forming Units Counting (UFC) tests will be carried out; analysis of Cell Viability (MTT); resistance to biaxial flexion; analysis of residual stresses; fatigue behavior (step-stress) and Weibull analysis; Fractographic analysis of the surface and biofilm (Escherichia coli and Strepctococcus sanguinis) by Scanning Electron Microscopy (SEM) and X-Ray Diffraction (XRD). 120 discs (12 mm in diameter, 1.2 mm thick) and 120 3Y-TZP zirconia pillars will be made. The discs will be polished with SiC # 1200 sandpaper and then together with the pillars they will be divided into 4 main groups (n = 30). After this step, the specimens will be sintered following the protocol recommended by the manufacturer. Subsequently, the glaze (Vita Akzent, VITA Zahnfabrik, Germany), sodium lime bioglass, glass with silver at 5% and 10% will be applied on the surfaces of the corresponding specimens and crystallized according to the temperature and time protocol previously established. Specimens of zirconia 3Y-TZP of 4.0 x 4.0 x 1.6 mm3 (n = 8) will be made and sterilized by ultraviolet light. Subsequently, they will be placed in contact with Escherichia coli biofilm (ATCC 25922) and Streptococcus sanguinis (ATCC 10557) to perform the MTT test. Then, these samples (n = 1) will have the surface analyzed in SEM. The zirconia discs (n = 2) will be analyzed by X-ray diffraction (XRD) in order to characterize the phases formed during the crystallization of the glass with silver. The analysis of residual stresses will be determined by the indentation technique (n = 5). Then, the biaxial flexion test will be performed. For this, the discs (n = 30) will be positioned in a specific device (ISO 6872) and fractured in a universal testing machine. The results (MPa) will be submitted to Weibull analysis according to the maximum likelihood method (95% CI). Subsequently, two samples from each group will be selected for observation, in SEM, of the region of origin of the fractures. For the analysis of infiltration in the abutment/implant region (n = 30), the abutment/implant set will be immersed in BHI broth containing the bacterial suspensions. The colony count (CFU/ml) (n = 8) will be based on the collection of the interior content of the implants. Then, the abutment/implant sets will be tested for fatigue under the step-stress method (n = 30) and the data will be analyzed by Kaplan Meier and Mantel-Cox. After the fatigue and resistance to biaxial flexion tests, two fractured samples (discs and pillars) from each group will be subjected to fractographic analysis in SEM. (AU)