Evaluation of the castability of a Co-Cr-Mo-W alloy varying the investing technique

Abstract

The purpose of this study was to compare the castability of Co-Cr-Mo-W (Remanium 2000), Ni-Cr (Durabond) and Co-Cr-Mo (Vera PDI) alloys invested with either conventional (phosphate- and silica-based) or mixed investing techniques. A 10 X 10 mm square-shaped nylon net containing 100 open squares served as a template for construction of wax patterns, which were invested with phosphate-based investment (Termocast), silica-based investment (Refrafil) and mixed investing technique (2-mm layer phosphate investment plus filling with silica investment). Forty-five cast specimens (5 per experimental condition) were obtained and sandblasted with aluminum oxide. The number of completely reproduced cast segments was counted to obtain a percentage designated "castability value", which indicated the accuracy of the alloy to reproduce mold details. Statistical analysis using two-way ANOVA and Tukey's test showed that, comparing the alloys, Remanium 2000 had statistically similar castability (p>0.05) to Vera PDI and lower than Durabond (p<0.05). Considering the mixed technique results, Remanium 2000 yielded lower castability value (p<0.05) than Durabond and Vera PDI alloys, which showed similar results to each other (p>0.05). In conclusion, the castability of the Co-Cr-Mo-W alloy (Remanium 2000) was comparable to that of the Co-Cr alloy (Vera PDI) and worse than that of the Ni-Cr alloy (Durabond). Except for Remanium 2000, the mixed investing technique considerably improved the accuracy of the alloys to reproduce cast details, compared to the phosphate-based investment. The mixed investing technique appears as a viable alternative to improve castability of base metal alloys without decreasing the surface quality of the metallic pieces.

A Comparative Evaluation of Marginal Accuracy of Co–Cr Metal Copings Fabricated Using Traditional Casting Techniques and Metal Laser Sintering

“… 3 Cobalt–chromium alloys were preferred, the major advantages of this alloy are its lower thermal expansion coefficient and higher creeping strength in high temperatures during porcelain firing. 12 Nevertheless, Ni–Cr alloys despite their satisfactory clinical performance and high modulus of elasticity, give them rigidity even in small thickness, these alloys have limitations related to their high hardness, difficult laboratory processing 13 and low flow rate, the high incidence of incomplete margins being the most frequently reported problem. According to Moffa et al, 14 the increase of casting temperature increases the flow of the Ni–Cr alloy and reduces casting failures; nevertheless, it also increases surface roughness, which poses additional difficulty to the finishing and polishing procedures.…”

“…According to Moffa et al, 14 the increase of casting temperature increases the flow of the Ni–Cr alloy and reduces casting failures; nevertheless, it also increases surface roughness, which poses additional difficulty to the finishing and polishing procedures. 12 Many of the Ni–Cr alloys contain beryllium, which can be toxic in uncontrolled dental laboratories.…”

Assessment of the influence of selected electrolytic polishing process parameters on the surface roughness of casts made of the CoCrMo alloy

“…Numerous studies on Co-Cr alloys have revealed that their structure is predominantly characterized by the presence of large grains, which is associated with lower mechanical and physical properties, such as compressive strength, tensile strength and flexibility. 17,18 An analysis of the alloy microstructure showed that there were smaller grains in the thinner parts and larger grains in the thicker ones. This is due to the faster cooling of the thin parts, which disenables grain growth.…”

Comparison of Dental Prostheses Cast and Sintered by SLM from Co-Cr-Mo-W Alloy

“…In contrast to the alloys used in orthopaedics, cobalt-based dental alloys are free from the addition of nickel. Tungsten does not affect the fluidity of Co-CrMo alloys but increases the stacking-fault energy (SFE), thus reducing the density of stacking faults [6,7]. Moreover, compared to the Co-Cr-Mo alloys, alloys containing tungsten are characterized by lower thickness of the oxide layer generated in the manufacturing process, which facilitates the combination with ceramics.…”