Evaluation of the dimensional changes and surface roughness of gold crowns cast with rapidly prepared phosphate-bonded investment: A pilot study

Abstract

Statement of problem. Accelerated bench-set and burnout schedules are used with little knowledge of the effect acceleration has on clinical factors determining casting success.Purpose. This pilot study investigated the effect of 2 rapid mold preparation schedules on full crown castings by comparing size, margin sharpness, and surface roughness.Material and methods. Three groups of 10 crowns were cast with a type III gold alloy. All crowns were nominally identical, only their mold preparation schedules differed. Two groups used accelerated schedules; the third group was cast using a conventional schedule. Group comparisons were based on direct microscopic measurements of crown diameters (x50 magnification), and surface roughness was measured. Margin sharpness was judged by amount of marginal length lost in the axial direction as a result of the casting process.Results. Measured crown diameters, indexing size for the 3 groups, were not significantly different. Crowns made with the conventional schedule had greater surface roughness, and better margin sharpness or length.Conclusion. Crowns were successfully cast using accelerated mold preparation techniques and considerable time was saved, but a small loss of margin length or fineness was observed.