The effect of asbestos-alternatives on the accuracy of cast veneer crowns

The effect of three different lining materials on the investment expansion during the casting procedure, was compared. The accuracy of the castings was assessed by measuring slits at the gingival shoulder of a cast veneer crown. The liners were made of asbestosos, paper and a glassfiber material. They were used with a gypsum bonded and a phosphate bonded investment material using a regular type III and a high-fusing alloy. The glass-fiber material seemed to give a good and reproducible accuracy with both investments. The effect of this liner seemed to be comparable or better than that of the conventional asbest material. The paper liner sometimes allowed a sufficient expansion, but with varying results. Additional problems were connected to this material as it was burnt to ash during the mould heating procedure.