Y-TZP/MWCNT-COOH nanocomposite development for dentistry application: characterization and aging

• Grant number: 12/16027-2
• Support type: Regular Research Grants
• Duration: March 01, 2015 - February 28, 2017
• Field of knowledge: Health Sciences - Dentistry - Dental Materials
• Principal Investigator: Paulo Francisco Cesar
• Grantee: Paulo Francisco Cesar
• Home Institution: Faculdade de Odontologia (FO). Universidade de São Paulo (USP). São Paulo , SP, Brazil
• Assoc. researchers: Dolores Ribeiro Ricci Lazar

Abstract

The main purpose of this study is to develop a nanocomposite Y-TZP/MWCNT-COOH (3 mol% Yttria-stabilized Tetragonal Zirconia Policrystal reinforced with -COOH functionalized multi-walled carbon nanotubes) to be use as fixed dental prostheses framework and implant abutments. This new material will be characterized and compared to a conventional Y-TZP for its physic-mechanical properties, aging resistance and slow crack growth susceptibility. The material development will be done by coprecipitation followed by hydrothermal/solvothermal treatment and isostatic pressing to form CAD/CAM blocks. Bar-shape specimens (25x4x3 mm) of Y-TZP and Y-TZP/MWCNT-COOH will be prepared to characterize and compare the microstructure, optical properties, flexural resistance, fracture toughness, fatigue limit and crystalline phase stability versus in vitro aging. The characterization will be performed by density measurement before and after sintering (nd=10), microstructural and chemical analysis using SEM and EDS (nm=3), porosity and grain size measurements, and determination of elastic constants (E e n) (np=5), contrast ratio, translucency parameters and opalescence index (no=10). The phase stability maintenance (nf=10) will be verified by XRD before and after an autoclave aging cycle. As well, the bar-shape specimens will be submitted to a 4-point flexural strength test (n=30) following the ISO 6872:2008. The obtained data will be analysed by Weibull distribution (5%) and differences will be indentified using the confidence interval. The fracture toughness (nt=5) will be evaluated by the single-edge-V-notched Beam method for the both materials and differences will be calculated using the t-Student test (±=0,05). The cyclic fatigue limit will be evaluated by the staircase method using a ElectroPuls E3000 Instron equipament, that also will provide information to calculate the subcritical crack growth parameters (n* and A*). A fractographic analysis will be performed in all the fractrured bars to aquire information related to the fracture origin and the influence of the nanotube protection mechanism during the fracture. (AU)