Indications

Any time teeth have been damaged by trauma, decay, or tooth fracture and/or heavily restored, those teeth are structurally compromised (Figure 20-2). These are good candidates for porcelain-fused-to-metal restorations. In addition, patients who have high esthetic demands or requirements may be treated with a porcelain-fused-to-metal restoration. This choice allows the dentist to create a restoration that can visually restore the tooth to its proper esthetics.

FIGURE 20-2 A lower first molar with a large restoration and a fractured distal buccal cusp.

Contraindications

The primary contraindication would be if the crown preparation cannot achieve sufficient occlusal clearance. This means 2 mm for the porcelain-fused-to-metal restoration. Another contraindication would be concern about porcelain wearing the opposing dentition when functional occlusion is restored. Porcelain would not be appropriate in a functional pathway. Instead cast metal would be more desirable.

Metals

There are a number of different material options for the metal substrate of the porcelain-fused-to-metal restoration. The major classes are base cast metals, high noble metals, and semi-precious metals. The advantages of each are partially based on cost. Base metals are inherently lower in price and tend to provide the structural integrity needed. These lower-cost restorations still provide for the patient’s functional and esthetic needs. However, the dentist must carefully select patients in whom base metals are to be used. Dentists must be concerned about the biocompatibility of the metals. Base metals frequently contain nickel, which is associated with a high incidence of allergic reactions in patient populations.

With high noble metals, restorations become a bit more expensive because of the cost of the material. These offer the advantage of better biocompatibility than base metals.

The semi-precious metals contain high percentages of gold, platinum, and palladium, all of which are even more biocompatible (Figure 20-3). These metals also tend to have a slightly better fit and even the potential for the margins to be burnished, which provides an enhanced clinical result.

FIGURE 20-3 A porcelain-fused-to-metal crown with a metal substructure that has a high gold content.

Porcelains and Ceramics

Many different types of porcelain can be used. The industry standard for years has been the use of stacked porcelains, where a powder and liquid are mixed together on top of the metal to provide the final esthetic result (Figure 20-4).

FIGURE 20-4 A powder-liquid mixture of porcelain is stacked onto the metal framework.

Numerous different ceramics are also available, with the selection often made based on personal preference of the dentist and/or on discussions with the ceramist.

Recently techniques have been developed wherein ceramics are actually pressed on top of metal. This provides another ceramic option to the dentist in obtaining an ideal end result. The pressed ceramics offer the advantages of ease of fabrication and slightly better strength.

Current Best Approach

The dentist must carefully consider the different options available for full-coverage restorations. Porcelain-fused-to-metal restorations are one of several different types of restorations available. Based on the patient’s clinical needs, the dentist’s experience, and the labo/>