Avaliação da alteração de rugosidade de superfície e dispersão de íons de ligas metálicas odontológicas submetidas a ensaio de tribocorrosão experimental [thesis]

Denise Pupim
PUPIM D. Evaluation of changes in surface roughness and ion release from dental casting alloys after an experimental tribocorrosion process [thesis]. Ribeirão Preto: Universidade de São Paulo, Faculdade de Odontologia de Ribeirão Preto, 2015. 110p. The aim of this study was to evaluate the changes in surface roughness and ions release to the environment after experimental tribocorrosion of CoCrMo, NiCr and NiCrTi alloys, commercially applied in dental prosthesis, using artificial saliva
more » ... (Fusayama) as electrolyte with different levels of pH (3.0; 6.5 and 9.0). Fifteen samples were casted by flame from each alloy (13x2mm) and 15 by plasma in a casting machine with an inert atmosphere (argon), five samples for each pH analyzed. The experimental tribocorrosion was performed in a ball-on-flat configuration, using a zirconia ball (10mm) in vertical cycling equipment, simulating the masticatory cycle movement, applying 5N of load and recording the open circuit potential (OCP). The system operated at 60 cycles per minute, a total of 7500 cycles after 15 minutes, corresponding to the daily tooth contact. Artificial saliva at pH 3.0; 6.5 and 9.0 was used and surface roughness measurements were performed before and after the experimental tribocorrosion tests in a laser confocal microscope. After the tests, the saliva was stored in a DNA-free Falcon tubes and subjected to measurement of the ion release to the solution by means of ICP-MS analysis. The behavior of the alloys in contact with the zirconia ball during the experimental tribocorrosion performed in open circuit potential changed according to the pH (P<0.001) and the casting technique (P<0.001). All samples trended to repassivate when the ball contact was removed, indicating new formation of the protective film on alloy surface. The ion release was higher in the samples casted by flame and in contact with pH 3.0 (acid), nickel analyte being released in a higher concentration (P=0.010). However, the values found are below the limits specified to induce cytotoxicity and cellular changes. The results reflected that the samples casted by flame presented surface roughness statistically greater than those casted by plasma (P=0.042) and it was observed in these samples the presence of surface defects and possible casting flaws that enhance the corrosion process. The pH of the saliva and the casting technique presented influence on the repassivation behavior of the alloys, surface roughness and quantity of ions released into the environment, where the best results were found when the plasma casting technique was used.
doi:10.11606/t.58.2017.tde-17022016-170119 fatcat:rvfruvnk2ne55gqz755cchr4qa