Scanning electron microscopy of the marginal fit of ceramometal restorations with facially butted porcelain margins

Abstract

A t t e m p t s to develop a complete ceramic restoration have been in progress for many years. Land I was the first to describe the technique for porcelain jacket crown construction using a platinum foil matrix. However, the inherent weakness of dental porcelain together with the high sintering shrinkage have been severe drawbacks to its universal acceptance as a complete veneer restoration. Although efforts to improve the strength of dental porcelain were mildly successful, 26 the problems of sintering shrinkage and marginal inaccuracy remained. The tendency for spheroiding of porcelain margins was an additional problem.** The ceramometal restoration was developed to reduce these limitations by providing a metal substructure to reinforce the porcelain and facilitate superior marginal integrity. 7 However, because the labial metal collar compromised the esthetics of anterior restorations, a facially butted porcelain margin has become an increasingly popular modification? McLean 9 classified laboratory techniques as platinum foil,10.11 refractory die, 12,13 and direct lift. 9,14,15 Prince et alJ 6 recently introduced a technique using wax as a binder for porcelain powder. Unfortunately, the facially butted porcelain ceramometal restoration had poor marginal adaptation with mean marginal openings of 40 to 50 ~tmJ 2' 17 The recent introduction of special shoulder porcelain powders (Vita VMK, Vita Zahnfabrik, Bad Sackingen, W. Germany) promises improvement. Inasmuch as these powders fuse at higher temperatures, the possibility of reduced shrinkage during sintering, and spheroiding during glazing unsupported, exists. This study measured the marginal adaptation of facially butted porcelain ceramometal restorations using the direct lift technique and compared this measurement to the shoulder-bevel ceramometal restoration and porcelain jacket crown. The marginal fit of shoulder-bevel ceramometal restorations after veneering was also investigated.