Effect of casting temperature and atmosphere on castability of Ni-Cr alloys: a comparative study with direct flame casting method

Abstract

The purpose of this study was to compare the effect of casting temperature and atmosphere on the castability of three Ni-Cr alloys against direct flame casting method. Vera Bond (VB), Vera Bond 2 (VB2) and Wiron 99 (W99) were cast at three temperatures: VB and VB2 (1310 °C, 1340 °C and 1370 °C); W99 (1400 °C, 1430 °C and 1460 °C) in atmosphere, vacuum and direct flame. Each alloy was cast in seven different conditions. Castability was assessed by the method that verifies the alloy potential to reproduce a nylon mesh. Kruskal-Wallis test demonstrated for VB, while there was no influence in the temperature range, castability was greater by vacuum (99.3%) than by direct flame (96.2%) and atmosphere (93.06%). For VB2, castability was greater at evaluated temperatures (1370 °C = 94.4%, 1340 °C = 91.15% and 1310 °C = 87.9%) than direct flame (77.8%); related vacuum (97.33%) obtained better values than atmosphere (84.6%) and direct flame. For W99, while atmosphere had no influence, castability was higher at 1460 °C (84.3%) than at other temperatures (1430 °C = 70.3%, 1400 °C = 37.05%) and direct flame (62.5%). Comparison among interactions showed that for all alloys it was possible to significantly increase the filling percentage of the mold in a comparative manner with the direct flame cast method

Effect of casting atmosphere on the shear bond strength of a ceramic to Ni-Cr and Ni-Cr-Be alloys

“…In the present study, specimens were not cast by gas-oxygen flame technique. Nevertheless, it is possible that the use of these methods might have resulted in lower MCBS values when compared to other groups, since the use of casting machines that enables closing the control of casting conditions may represent a significant contribution to improving the quality of dental restorations with base metal alloys (19). However, to the best of our knowledge, there were no studies that evaluated the effect of casting atmosphere on the MCBS of the Ni-Cr alloys.…”

“…The incorrect use of a direct gas-oxygen flame may affect the properties of Ni-Cr alloys (19), despite its ideal formulation and mold temperature, due to the possibility of over-or under-melting temperature and use of the oxidizing zone of the flame during casting. In the present study, specimens were not cast by gas-oxygen flame technique.…”

Effect of Angle and Type of Customized Abutment (Castable & Cast-to) on Torque Loss and Fracture Resistance After Cyclic Loading

“…Many manufacturers suggest using customized cast abutments as an alternative to prefabricated abutments for prosthetic rehabilitation of unconventional angulation of implants. Use of Cr-containing alloys such as Co-Cr and Ni-Cr has greatly increased due to their cost-effectiveness [15]. Evidence shows that defects in base metal restorations are mainly due to inaccurate casting rather than the suboptimal properties of the alloys [16].…”