Erosion of Gypsum Casts Following Cleaning of Debris From Cast Trimmer

Objectives: The most accurate casts are made using a two-stage pour method. Debris mixed with water will be deposited on the surface of the dental cast when the base of the two-stage pour is trimmed. Our objective is to evaluate the efficiency of different methods used to clean the cast, and the effect of tap water on the surface quality of the cast.

Methods: The ANSI/ADA die for spec 18 was embedded into a dentoform with the machined lines at the same position as the occlusal surface of the posterior teeth. Forty polyvinylsiloxane impressions were made of the dentoform and poured in an improved dental stone. Each cast was reviewed for accurate reproduction of the lines. The base of the two-stage pour was trimmed using a cast trimmer with water, the surface debris was removed by rinsing by hand under tap water for 10 seconds, brushing the cast with a soft toothbrush for 10 seconds, and resoaking the cast and swishing in water for 10 seconds. The amount of debris was evaluated on a scale of 1-4, and the quality of the 20 micron line was evaluated on a 1-4 scale under a 10X magnification.

Results: See table. ANOVA/Tukey (p<0.05)

Conclusions: Rinsing the cast under tap water and brushing or hand washing, or swishing the surface for 10 seconds had no noticeable effect on the quality of a 20 micron line, and all three methods resulted in a clean cast.