The fit of gold-alloy full-crown castings made with pre-wetted casting ring liners.
Measurements were made of the fit of full-crown gold-alloy castings produced with two types of pre-wetted ring liner (asbestos and cellulose) and a typical gypsum-bonded investment (Cristobalite Inlay, Sybron/Kerr Products, Romulus, MI; W/P = 0.40). Laboratory measurements were made of the effects of the liners on potential investment expansion, and properties of the lining materials considered relevant to casting accuracy were also measured. There was a wide variation in values for mean dimensional inaccuracy. One liner produced a series of castings all of whose inaccuracies lay within the range +/- 0.1%, with a mean value of + 0.01%. With the other five liners, all or most castings were undersize. With three, all or most castings showed inaccuracies worse than -0.2%. The values for casting inaccuracy with the various liners showed a probable correlation with potential investment expansion (p < 0.05); however, no correlation was found between casting inaccuracy and any apparently relevant liner properties, alone or in combination. In casting techniques which use a pre-wetted ring liner, the choice of a specific lining material is an important factor which has a significant effect on casting inaccuracy. With at least three of the six liners tested, a higher investment expansion was needed for accurate full-crown castings to be ensured.
Morey
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EF
Department of Operative Dentistry, University of Sydney, Surry Hills, NSW, Australia.
Earnshaw
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R
D000042:Absorption; D001194:Asbestos / Q000737:chemistry*; D002133:Calcium Sulfate / Q000737:chemistry*; D002482:Cellulose / Q000737:chemistry*; D003442:Crowns; D003734:Dental Casting Investment / Q000737:chemistry*; D003735:Dental Casting Technique / Q000295:instrumentation*; D004867:Equipment Design; D006047:Gold Alloys / Q000737:chemistry*; D008422:Materials Testing; D013314:Stress, Mechanical; D013499:Surface Properties; D013816:Thermodynamics; D014867:Water
D003734:Dental Casting Investment; D006047:Gold Alloys; D014867:Water; D001194:Asbestos; D002482:Cellulose; D002133:Calcium Sulfate