Dental stone and improved dental stone surface hardness: the effect of the addition of potassium salts.

Changes in dental stone and improved dental stone surface hardness observed when prepared with aqueous solutions of potassium salts (K2SO4, KCl, KF, KBr, KNO4, KMnO4, K2Cr2O7) in concentrations of 0.5-5.0% were investigated. Parallel studies were carried out on dental stone and improved dental stone prepared with distilled water and crystallised in contact with alginate impression material, previously immersed in the above solutions for 2 minutes. Vicker's hardness tests were performed 3 hours and 24 hours after the initial set. The surface hardness of dental stone and improved dental stone is increased significantly by either method. The most effective hardening solution is potassium sulphate in concentrations of 0.5-5.0%. The degree of increase in surface hardness is directly proportional to the concentration of the solutions and proportionately greater at a shorter time (3 hours after the initial set).