An application of the jet test method for the evaluation of disintegration of dental luting cements in marginal gaps analogous to those of crowns and bridges

Abstract

A new type of cement holder designed to simulate the clinical situation of a crown margin with a shoulder finish was developed for use in the jet test apparatus. The disintegration of thin films of cement exposed at their margins to jets of dilute acid media was evaluated. Glass ionomer (Aquacem), zinc polycarboxylate (Poly F) and zinc phosphate (Ash CAS) cements were tested with lactic and citric acids at pH levels 2.5 and 4.0. The effect of increasing the thickness of cement lute from 20 to 160 micrometres was also examined. Breakdown of the cement was assessed by means of planimetry and also by linear measurement of the maximum depth of loss. It was found that the results from the two methods were highly correlated (r = 0.992). The materials were ranked in order of disintegration as follows, glass ionomer < polycarboxylate < zinc phosphate. The more acidic media caused increased disintegration of zinc polycarboxylate and zinc phosphate, as did an increase in the thickness of cement lute. However, both these factors had a negligible effect on the glass ionomer cement.