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Measurement of the setting expansion of phosphate‐bonded investment materials: Part I – Development of the Casting‐Ring Test
Author(s) -
Lloyd C. H.,
Yearn J. A.,
Cowper G. A.,
Blavier J.,
Vanderdonckt M.
Publication year - 2004
Publication title -
journal of oral rehabilitation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.991
H-Index - 93
eISSN - 1365-2842
pISSN - 0305-182X
DOI - 10.1111/j.1365-2842.2004.01292.x
Subject(s) - ring (chemistry) , investment (military) , reproducibility , materials science , investment casting , test (biology) , property (philosophy) , composite material , mechanical engineering , structural engineering , mathematics , engineering , chemistry , statistics , geology , mold , paleontology , philosophy , organic chemistry , epistemology , politics , political science , law
summary The setting expansion is an important property for a phosphate‐bonded investment material. This research was undertaken to investigate a test that might be suitable for its measurement when used in a Standard. In the ‘Casting‐Ring Test’, the investment sample is contained in a steel ring and expands to displace a precisely positioned pin. Variables with the potential to alter routine reproduction of the value were investigated. The vacuum‐mixer model is a production laboratory variable that must not be ignored and for this reason, experiments were repeated using a different vacuum‐mixer located at a second test site. Restraint by the rigid ring material increased expansion, while force on the pin reduced it. Expansion was specific to the lining selected. Increased environmental temperature decreased the final value. Expansion was still taking place at a time at which its value might be measured. However, when these factors are set, the reproducibility of values for setting expansion was good at both test sites (coefficient of variation 14%, at most). The results revealed that with the control that is available reliable routine measurement is possible in a Standard test. The inter‐laboratory variable, vacuum‐mixer model, produced significant differences and it should be the subject of further investigation.