Tissue sensitivity can be a common issue with PFM (porcelain fused to metal) crowns and bridges. Base-metal crowns contain nickel, which can cause an allergic reaction in many people, especially women. Restorations that use non-precious metals can sometimes result in gum tissue that is purplish in appearance, and some patients experience irritation and/or gingival recession. Alternatively, zirconia is a biocompatible material and has been used with great success in other medical applications, for example, hip replacements, for the past 20 years. Similarly, zirconia results in excellent tissue response when used in the mouth - gum tissue appears healthy and is pink in color. Further, the tissue does not pull away from the material, which can occur with traditional PFM restorations.
Dr. James L. Johnson