EFEITO DA IMERSÃO PERIÓDICA EM SOLUÇÕES LIMPADORAS NA RUGOSIDADE SUPERFICIAL, PORCENTAGEM DE VARIAÇÃO DE MASSA E RESISTÊNCIA FLEXURAL DE LIGAS DE COBALTO-CROMO
BORSA, Pedro Carlos Cortiana. Co-Cr ALLOY IMMERSION IN CLEANING SOLUTIONS: EFFECTS ON FLEXURAL STRENGTH, SURFACE ROUGHNESS AND PERCENTUAL OF VARIATION OF MASS. 2014. 62 f. Dissertação (Mestrado em Odontologia) - Universidade Federal de Santa Maria, Santa Maria, 2014.
Borsa, Pedro Carlos Cortiana
The aim of this study was to evaluate the flexural strength, elastic modulus, mass changes and surface roughness of two cobalt-chromium alloys, before and after immersions in four cleaning solutions and distilled water (as control). Co-Cr alloys (Co-Cr®, Dentsply-DeguDent Industria e Comércio, São Paulo, Brasil; and GM 800+®, Dentaurum GmbH & Co KG, Ispringen, Alemanha) were investigated. Fifty bar specimens (25 x 3 x 0,5 mm) for the flexural test, 50 quadrangular specimens (10 x 10 x 1 mm) for mass changes evaluation and 35 cylindrical specimens (10 x 1 mm) for surface roughness measurements were obtained by casting. They were polished by abrasive paper (#240 to #2500) and diamond polishing paste (3μm). Specimens were randomly divided into 5 groups according the following cleaning, solutions: pure white vinegar, 0.2% peracetic acid, sodium perborate - Corega Tabs®, 0.37% sodium hypochlorite and the control, distilled water. Surface roughness (Ra parameter) was analyzed using a profilometer (Mitutoyo SJ 410, Mitutoyo Corp, Kanagawa, Japan) before and after 5, 20 e 90 immersions (10 min each). Ra changes (ΔRa5, ΔRa20 e ΔRa90) were calculated for the different intervals. Qualitative surface analyses were performed by Scanning Electron Microscope (JSM 6360 SEM, JEOL). Both alloys, immersed in pure white vinegar, 0.2% peracetic acid, sodium perborate - Corega Tabs®, 0.37% sodium hypochlorite had similar roughness changes after 90 immersions (ΔRa from -0,012 to 0,022 μm). There was a significant surface roughening in hypochlorite (ΔRa90= 0,064 μm for CoCr®; and ΔRa90 = 0,592 μm for GM 800+). The number of immersions influenced on the roughness changes only in hypochlorite and there were greater changes in the GM 800+ alloy. After 90 immersions, GM 800+ alloy showed mass lost in the hypochlorite solution (-0,3%). This alloy presented higher flexural strength after 90 immersions in SH (σF= 1516 MPa in hypochlorite; 1366 MPa in control). However, there were no elastic modulus changes. CoCr® alloy did not present differences in the σF or in elastic modulus in any solution. The only solution that damaged the alloy surface was 0.37% sodium hypochlorite.