Evaluation of tensile strength of nickel-chromium alloys for metalloceramic restorations melted under different heat sources

Abstract

The aim of this study was to verify the tensile strength (TS) of three Ni-Cr alloys melted under two different heat sources: blow pipe gas/oxygen (BP) and induc- tion melting machine (IM - F.lli Manfred). The alloys used were: Ni-Cr (NC - VeraBond II/AalBa), Ni-Cr-Be (NB - VeraBond/Aalba) and Ni-Cr-Ti (NT - Tilite-Star/ Taladium), totalizing six groups. Thirty-six cylindrical specimens, six for each experimental con- dition (45 mm long and with a diameter of 1.6 mm) were melted with a phosphate investment (Mi- cro Fine 1700). The tensile test was performed with a universal machine (Riehle) at a crosshead speed of 0.5 mm/min and specimen testing length of 25 mm. Data were submitted to a two-way ANOVA and Tukey’s test for mean comparisons (a = 0.05). The means (MPa), standard deviations (MPa) and statistical significances were: group (NC + BP) = 613.8 ± 87.8b; group (NC + IM) = 557.4 ± 80.0b; group (NB + BP) = 877.7 ± 76.8a; group (NB + IM) = 675.9 ± 103.9b; group (NT + BP) = 836.0 ± 57.6a; group (NT + IM) = 912.1 ± 79.9b. It was concluded that: 1) The heat source has influenced just on the tensile strength of Ni-Cr-Be; 2) Ni- Cr-Ti alloy showed better results than Ni-Cr alloy, despite of the heat source; 3) Absence of Be lead to lower TS values. Key words: metal loceramic alloys, dental casting technique, tensile strength.