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Biofilm and pH effects on the slow crack growth and microstructure of dental ceramics


This study aims to study the alterations in the microstructure e the resistance to crack propagations of dental ceramics. The influence of biological factors such as the biofilm formation and its products, the presence of saliva and the pH after dripping different solutions on the material will be analyzed. One hundred and seventy ceramic discs (1.2 mm thick and 15 mm diameter) will be made for each of two ceramics (Vita VM7 e VM 13, Vita Zahnfabrik, Bad Sackingen, Germany) and divided into groups for in situ e in vitro studies. Indented and non-indented specimens will be subjected to biaxial flexural strength test in mineral oil (0.5 mm/min, 100 MPa/s) for calculation of the initial strength. For the in vitro study, the specimens will receive an indentation as initial crack. The specimens will then stay in S. mutans culture for 14 d and, after that, in remineralizing solution for the same length of time. These specimens will be subjected to the flexural test under four loading conditions (0.1; 1; 10 e 100 MPa/s), to determine the slow crack growth parameters. In the in situ study, non indented discs will be fixed to an intraoral device that will be worn for 10 subjects for 15 d. The subjects will also drip three solutions (distilled water, 20% sacarose, and orange juice) on the discs to determine the effect of the pH variation on the specimen covered with the biofilm. The pH will be measured with a microsensor on the second and fourteenth days of usage of the device. MEV, XPS and FTIR will be used for the microstructural analysis. The fractured samples will be analyzed fractographically. The results of initial strength of non-indented specimens will be used for Weibull analysis for calculation of the Weibull modulus "TM". Other statistical tests (Anova, Tukey, a=5%) will be used to compare the strength to the microstructure. (AU)

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(References retrieved automatically from Web of Science and SciELO through information on FAPESP grants and their corresponding numbers as mentioned in the publications by the authors)
MELO, RENATA M.; PEREIRA, CRISTIANE; RAMOS, NATHALIA C.; FEITOSA, FERNANDA A.; DAL PIVA, AMANDA M. O.; TRIBST, JOAO PAULO M.; OEZCAN, MUTLU; JORGE, ANTONIO O. C.. Effect of pH variation on the subcritical crack growth parameters of glassy matrix ceramics. International Journal of Applied Ceramic Technology, v. 16, n. 6, p. 2449-2456, . (10/50450-4)

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