Abstract
Physical and chemical properties of tetracalcium phosphate(4CP)and α-tricalcium phosphate(α-TCP)cement were compared.4CP or α-TCP was mixed with 45% citric acid solution at a powder-liquid ratio of 1.5(w/w).To determine the acidity of the cements, changes in the pH of 0.5ml of distilled water in contact with each cement surface was monitored.4CP cement gave the highest pH, ranging from 4.75 to 5.23, among the 4 types of cement tested.The measured pH values of α-TCP and polycarboxylate cements were 4.02 to 4.22 and 4.14 to 4.62, respectively.On the other hand, zinc phosphate cement showed strong acidity, (pH3.29 to 3.62).These in vitro results suggest that 4CP cement is irritative to the dental pulp.The compressive strengths of both 4CP and α-TCP cements, (50.0 and 74.9MPa respectively), fullfilled the requirement of ADAS No.61 for polycarboxylate cement.Under the same conditions, it was shown that 4CP and α-TCP cements had high solubility(1.8 and 4.0% respectively)which were inferior to the standard.When immersed in phosphate buffered saline, 4CP and α-TCP cements also showed high solubility but no changes in the compressive strength for 7 days.
