Microstructure characterization and SCG of newly engineered dental ceramics.
The aim of this study was to characterize the microstructure of four dental CAD-CAM ceramics and evaluate their susceptibility to stress corrosion.



SEM and EDS were performed for microstructural characterization. For evaluation of the pattern of crystallization of the ceramics and the molecular composition, XRD and FTIR, respectively, were used. Elastic modulus, Poisson's ratio, density and fracture toughness were also measured. The specimens were subjected to biaxial flexure under five stress rates (0.006, 0.06, 0.6, 6 and 60MPa/s) to determine the subcritical crack growth parameters (n and D). Twenty-five specimens were further tested in mineral oil for determination of Weibull parameters. Two hundred forty ceramic discs (12mm diameter and 1.2mm thick) were made from four ceramics: feldspathic ceramic - FEL (Vita Mark II, Vita Zahnfabrik), ceramic-infiltrated polymer - PIC (Vita Enamic, Vita Zahnfabrik), lithium disilicate - LD (IPS e.max CAD, Ivoclar Vivadent) and zirconia-reinforced lithium silicate - LS (Vita Suprinity, Vita Zahnfabrik).



PIC discs presented organic and inorganic phases (n=29.1±7.7) and Weibull modulus (m) of 8.96. The FEL discs showed n=36.6±6.8 and m=8.02. The LD discs showed a structure with needle-like disilicate grains in a glassy matrix and had the lowest value of n (8.4±0.8) and m=6.19. The ZLS discs showed similar rod-like grains, n=11.2±1.4 and m=9.98.



The FEL and PIC discs showed the lowest susceptibility to slow crack growth (SCG), whereas the LD and ZLS discs presented the highest. PIC presented the lowest elastic modulus and no crystals in its composition, while ZLS presented tetragonal zirconia. The overall strength and SCG of the new materials did not benefit from the additional phase or microconstituents present in them.
Department of Dental Materials and Prosthodontics, São Paulo State University (UNESP), Institute of Science and Technology, 777 Eng. Francisco José Longo Avenue, 12245-000, São José dos Campos, SP, Brazil.
Nathália de Carvalho
Nde C
Ramos
Aeronautics Technological Institute (ITA), 50 Praça Marechal Eduardo Gomes, 12228-900, São José dos Campos, SP, Brazil.
Tiago Moreira Bastos
TM
Campos
Department of Dental Materials and Prosthodontics, São Paulo State University (UNESP), Institute of Science and Technology, 777 Eng. Francisco José Longo Avenue, 12245-000, São José dos Campos, SP, Brazil.
Igor Siqueira de La
IS
Paz
National Institute for Space Research, Associated Laboratory of Sensors and Materials, 1758 Astronautas Avenue, 12217-010, São José dos Campos, SP, Brazil.
João Paulo Barros
JP
Machado
Department of Dental Materials and Prosthodontics, São Paulo State University (UNESP), Institute of Science and Technology, 777 Eng. Francisco José Longo Avenue, 12245-000, São José dos Campos, SP, Brazil.
Marco Antonio
MA
Bottino
University of São Paulo (USP), School of Dentistry, Department of Biomaterials and Oral Biology, 2227 Prof. Lineu Prestes Avenue, 05508-000, São Paulo, SP, Brazil.
Paulo Francisco
PF
Cesar
Department of Dental Materials and Prosthodontics, São Paulo State University (UNESP), Institute of Science and Technology, 777 Eng. Francisco José Longo Avenue, 12245-000, São José dos Campos, SP, Brazil. Electronic address: renata.marinho@ict.unesp.br.
Renata Marques de
RM
Melo
D002516:Ceramics; D017076:Computer-Aided Design; D003343:Corrosion; D003776:Dental Porcelain; D003799:Dental Stress Analysis; D055119:Elastic Modulus; D008422:Materials Testing
D003776:Dental Porcelain
Ceramics; Computer-aided design; Dental porcelain; Flexural strength; Glass ceramics; Spectroscopy; Stress corrosion; Subcritical crack growth; Young's modulus