A study into the use of chromium-cobalt alloy for constructing the framework for osseointegrate prostheses

The feasibility of using chromium-cobalt alloy instead of silver-palladium in dental prosthetic framework was investigated. The frameworks were cast and tested for accuracy of fit on an abutment analogue. Whereas the silver-palladium frameworks fitted passively, with little need of adjustment (mean marginal opening, 8 microns), the colbalt-chromium frameworks demonstrated a wide range of marginal openings with a mean of 26.4 microns. This was attributed to the problems associated with the dimensional control of a higher shrinkage system, and could possibly overcome with an optimized casting design, (i.e. higher surface area to volume ratio). When the mechanical properties of the two different alloy frameworks were compared using strain-gauged, vertically-loaded cantilever arms (maximum load, 20kg) the advantage of the stiffer colbalt-chrome became apparent. The cantilever arms in colbalt-chromium were 2.5mm x 4mm in cross-section yet gave almost identical strain values to the much bulkier 6mm x 4mm silver-palladium arms. Thus a much less bulky framework could be designed from the former which would be a major advantage if intraoral space is limited.