Risks of Porcelain-Fused-to-Metal (PFM) Crowns
Dec 06, 2021
Source: Cainiu Health
Dr. Liu Dong
Introduction
1. Poor oral health increases susceptibility to infection. An unhealthy oral environment predisposes individuals to infections; additionally, inadequate marginal fit between teeth and crowns may lead to secondary dental diseases.
2. Fixed porcelain-fused-to-metal (PFM) bridges are prone to causing secondary dental diseases. Excessive tooth reduction during preparation brings the PFM crown too close to the dental pulp, increasing the risk of infection.
3. Allergic reactions may be triggered by materials used in porcelain-fused-to-metal restorations.
All-ceramic crowns refer to a high-tech dental restoration method developed in recent years. In this procedure, an inner crown—a fully transparent ceramic framework—is fabricated over the prepared tooth root, and then a layer of porcelain powder, closely matching the natural tooth’s color, is fused onto its outer surface via high-temperature firing. Finally, the completed crown is bonded to the tooth.
Potential Risks Associated with Porcelain-Fused-to-Metal (PFM) Crowns
1. Increased Risk of Oral Infection Due to Poor Oral Health
Not everyone is a suitable candidate for PFM crowns. Patients with compromised oral health are at higher risk of infection. Additionally, inadequate marginal fit between the natural tooth and the crown may predispose individuals to secondary dental diseases.
2. Multi-unit PFM Bridges May Lead to Secondary Dental Problems
Firstly, multi-unit PFM bridges often experience uneven occlusal forces during mastication, increasing the likelihood of loosening and creating opportunities for bacterial infiltration. Secondly, excessive tooth reduction during crown preparation may place the crown margin too close to the dental pulp, raising the risk of pulpitis or infection. Therefore, single-unit crowns are generally preferred over multi-unit bridges.
3. Allergic Reactions Triggered by Crown Materials
Non-precious metal PFM crowns consist of a nickel-chromium alloy substructure veneered with porcelain via high-temperature firing. Due to their relatively low cost, they remain widely used in China. However, these crowns have several drawbacks: poor marginal adaptation; suboptimal biocompatibility with human tissues—some patients develop a visible “gray line” along the gingival margin after prolonged wear—and documented cases of allergic reactions reported internationally. Moreover, chipping or fracture of the porcelain layer (“porcelain fracture”) occurs more frequently clinically.
4. Sensitivity to Thermal and Chemical Stimuli
After receiving a PFM crown, some patients experience discomfort or pain when consuming hot, cold, sour, or sweet foods. This is commonly attributable to excessive or overly rapid tooth preparation, which causes significant irritation to the dental pulp—leaving it in a state of hyperemia (increased blood flow). Prior to crown placement, clinicians must thoroughly assess periodontal and gingival health. Active gingival inflammation, erythema, swelling, recession, or discoloration necessitates initial periodontal therapy; only after gingival health has been restored should crown restoration proceed.
The above outlines the potential risks associated with PFM crowns. We hope this information is helpful to you.
