Porcelain-Fused-to-Metal Versus Zirconia-Based Ceramic Restorations, 2009

Abstract

P orcelain-fused-to-metal (PFM) restorations have been the dominant option in esthetic crown and fixedprosthesis restorations for about 50 years. When these restorations were introduced, there was pessimism about their value and their potential for long-term service. However, both research and clinical observation since have shown that they serve well. Research regarding the longevity of service of PFM crowns and fixed prostheses shows variable but relatively impressive results, depending on the number of units replaced, period of observation and location of the study. The method of PFM failure is apparent to clinical practicing dentists. The most destructive type of failure is breakage of a large piece of ceramic from the metal substructure. If the piece is small, the restoration can be smoothed and continue to serve. If it is a larger piece of ceramic, the restoration must be replaced. Another challenge arises when, across time, the gingival tissues recede, the crown margins become visible and the restoration is easily identified by a lay observer as a “false tooth.” Additionally, superficial color placed on crowns and fixed prostheses may abrade or dissolve from the restorations, leaving them chalky and often a lighter color than when they were placed. Again, they appear to be unnatural. Nevertheless, from a purely functional standpoint, the PFM restorations continue to serve long after they have become relatively unesthetic, and if a chip breaks from the restoration, the underlying metal substructure protects the tooth structure until some other restoration can be placed. Dentists trust PFM restorations because of their clinically observable service longevity when compared with several previous generations of all-ceramic crowns. The current generation of zirconia-based all-ceramic crowns and fixed prostheses is becoming popular. I have observed in the continuing education (CE) courses I teach that many general dentists and prosthodontists have used these restorations to a significant degree. Jim Schuck, vice president of sales and marketing of Glidewell Laboratories, Newport Beach, Calif. (the largest laboratory in the United States), estimates that use of all-ceramic restorations is increasing (J. Schuck, oral communication, April 2009). He also estimated Porcelain-fused-to-metal versus zirconia-based ceramic restorations, 2009