A dental crown is used in restorative dentistry to cover a damaged or weakened tooth. Gold has been a traditional crown material for decades due to its durability and excellent fit. When people ask if gold crowns are toxic, they are concerned about the long-term safety of having metal in their body. Dental gold is not pure gold, but a complex alloy, and its safety profile depends entirely on its specific composition.
The Composition of Dental Gold Alloys
The gold used in dentistry is mixed with other metals to increase its hardness and durability, as pure gold is too soft for chewing forces. This mixture forms a dental alloy, which is chemically different from the pure element. Dental alloys are classified based on their noble metal content, which includes gold, platinum, palladium, and silver.
The three main classifications are High-Noble, Noble, and Base-Metal alloys. High-Noble alloys contain at least 60% noble metals, with a minimum of 40% gold. Noble alloys contain a minimum of 25% noble metals, while Base-Metal alloys contain less than 25%. Non-gold components, such as copper, silver, and palladium, are added to modify the alloy’s physical properties. Copper and silver, for example, improve strength and hardness.
Gold Crowns: Biocompatibility and Systemic Safety
The question of systemic toxicity is addressed by the concept of biocompatibility. Biocompatibility describes a material’s ability to exist in the body without causing an adverse reaction. High-Noble and Noble gold alloys have very high biocompatibility, largely due to their resistance to corrosion.
These alloys are extremely stable in the oral environment, which is moist, saline, and slightly acidic. Because of this stability, they do not typically break down or leach significant amounts of metal ions into the bloodstream. This lack of ion release means the risk of systemic toxicity from a standard gold crown is very low. The high concentration of noble metals resists tarnish and corrosion, which is the primary mechanism for dental materials to release elements into the body.
Localized Reactions and Material Alternatives
While systemic toxicity is rare, specific localized adverse events can occur. These are distinct from a general health risk. One reaction is metal hypersensitivity, often called an allergy, usually caused by trace amounts of non-noble metals in the alloy. This reaction is often triggered by elements like nickel or copper, and symptoms manifest locally as dermatitis or irritation of the oral tissues.
Another issue is galvanic corrosion, which occurs when two different metallic restorations, such as a gold crown and an amalgam filling, are in contact within the mouth. This creates a minor electrical current, similar to a small battery. This current can accelerate the corrosion of the metals and increase the release of metal ions, leading to localized symptoms like a metallic taste or a burning sensation.
Material Alternatives
For patients with confirmed metal sensitivities or those who prefer a non-metal option, modern dentistry offers several alternatives. Porcelain, ceramic, and zirconia crowns provide excellent strength and superior aesthetics, as they can be precisely matched to the natural color of the surrounding teeth. Zirconia is a ceramic material known for its exceptional strength and high biocompatibility, often serving as a preferred choice for individuals seeking a metal-free restoration.