An in vitro study of marginal leakage associated with composite restorations using an acidified agar technique.

The marginal leakage associated with a composite restorative material was examined using an in vitro method for the production of secondary caries-like lesions after the restorations had been subjected to thermal cycling. The fillings were placed in cavities with a 90 degrees cavo-surface angle with and without etching of the walls with phosphoric acid and in cavities with a bevelled margin which were also acid etched. Some degree of leakage was demonstrated in 95% of the unetched cavities while approximately half of the restorations in etched unbevelled cavities showed leakage. With the bevelled and etched group virtually no leakage occurred.