Evaluation of macrohardness of recasted Cobalt–chromium alloy

Ahmed Al–Ali

doi:10.33899/rden.2006.40062

Abstract

Aims: To study the effect of recasting on the macrohardness of cobalt chromium (Co–Cr)alloy, and to evaluate the effect of finishing and polishing on it. Materials and methods: Two brand of Co–Cr alloys were used, divided into three groups, the specimens of the first group were casted from new materials, the second were casted from previously casted material without the addition of any new material (100% recast), the third were casted by combination 50% new material and 50% used material. Half of the specimens just finished and the other half were finished and polished , hardness for all of them were measured. Results: Showed that recasting, both 100% and 50%, significantly increase the macrohardness of Co–Cr alloys and no significant effect of finishing and polishing on it. Conclusion: Recasting may affect properties of Co–Cr alloy and new material should be used rather than recasted material.

Highlights

For decades gold has been used in dental practice to fabricate cast dental prosthesis
Nickel–chromium (Ni–Cr) and Cobalt–chromium (Co–Cr) alloys became a substitute for high noble alloy for dental cast restorations
Previously used base metal alloy may be combined with new metal to produce restoration with minimum cost for the dental laboratoryes.[1]. It is expected that difficulties will occur during the finishing and polishing of base metal alloys because of their high hardness

Summary

Introduction

For decades gold has been used in dental practice to fabricate cast dental prosthesis. Nickel–chromium (Ni–Cr) and Cobalt–chromium (Co–Cr) alloys became a substitute for high noble alloy for dental cast restorations. Previously used base metal alloy may be combined with new metal to produce restoration with minimum cost for the dental laboratoryes.[1] It is expected that difficulties will occur during the finishing and polishing of base metal alloys because of their high hardness. High macrohardness of some alloys has been associated previously with greater abrasion resistance and time required to polish restorations. Such alloys would be difficult to finish. A proper testing method may be difficult to develop, it would be useful if dental alloys could be classified according to their abrasion resistance.[2]

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