MARGIN DESIGN FOR PORCELAIN FUSED TO METAL RESTORATIONS WHICH EXTEND ONTO THE ROOT

A 90 degree shoulder is probably the most commonly used margin design for porcelain fused to metal (PFM) restorations. However, this design requires the removal of a significant amount of tooth tissue to provid e a predictable restoration. This increases the risk of irreversible d amage to the pulp, particularly if little tooth tissue is present, for example on exposed roots. In these situations more conservative desig ns, such as the 135 degree shoulder or deep chamfer, should be conside red. Ideally these designs should be used with an all-metal margin sin ce this is associated with the most predictable marginal seal. Where a n all metal margin is aesthetically unacceptable a porcelain butt or s ubgingival margin can be considered. Newer techniques, such as resin b onded crowns, which minimise tooth destruction and provide acceptable aesthetics may be a viable alternative to traditional PFM restorations . Unfortunately, these newer techniques have not been evaluated long-t erm.