Gold fillings, technically known as cast gold restorations, are one of the oldest and most durable methods for repairing damaged teeth. These restorations are not made of pure gold, but rather a custom-fabricated gold alloy designed for strength and longevity. Dentistry has long relied on this material to withstand the immense forces of chewing. Patients often question the safety profile of placing a metal alloy within the body, rather than its durability. This evaluation examines the material science, biological interactions, and comparative safety of gold restorations.
Composition and Material Safety
The material used in dental restorations is classified as a high-noble alloy. Pure gold is too soft, so it is combined with metals like copper, palladium, and silver to achieve necessary hardness and wear resistance. A typical high-noble gold alloy contains at least 60% noble metals, with a minimum of 40% being gold by weight.
Gold is chemically inert, meaning it resists reaction with the corrosive oral environment and is non-toxic to human tissue. The other metals in the alloy rarely cause systemic issues or allergic contact dermatitis. Allergic reactions to gold alloys are uncommon, and the material is considered highly biocompatible.
Long-Term Biocompatibility
The long-term safety of a dental material depends on its interaction with the body over decades. Gold alloys are noted for their exceptional resistance to corrosion, which is a primary measure of long-term biocompatibility. This inert quality means the restoration does not break down or tarnish when exposed to saliva and the fluctuating pH levels of the mouth.
Minimal degradation prevents the sustained release of metal ions into the surrounding tissue or bloodstream. Because the material remains stable and intact, the risk of systemic exposure to alloy components remains very low throughout the restoration’s lifespan. Biocompatibility studies often use noble metal alloys as the standard comparison point due to their anti-corrosive properties.
Electrical and Thermal Reactions
As a metal, gold conducts both temperature and electricity, which can lead to localized, temporary reactions. Gold is a thermal conductor, which may cause a tooth to feel sensitive to hot or cold foods immediately following placement. This sensitivity is usually short-lived as the tooth adjusts to the new restoration material.
A specific concern is oral galvanism, often called galvanic shock, which occurs when two dissimilar metals are present in the mouth. For example, if a gold filling is placed next to an existing silver amalgam filling, saliva acts as an electrolyte, creating a small electric current. This reaction can cause a sharp pain or a metallic taste, though it is rare. The galvanic effect can also increase the corrosion of the less noble metal, potentially leading to increased release of metal ions from the other restoration.
Gold Fillings Versus Other Materials
The safety profile of gold fillings is often compared favorably to the two most common alternatives: dental amalgam and composite resin. Amalgam fillings contain approximately 50% elemental mercury, which has led to public health debates about mercury vapor release. Gold is completely free of mercury, eliminating this specific health concern entirely.
Composite resin fillings are made of plastic and glass materials which may contain trace amounts of bisphenol A (BPA) or related compounds. Although current composite materials are generally regarded as safe, degradation over time can lead to the leaching of these trace elements. Gold alloys offer a chemically stable alternative, providing a non-polymer, non-mercury material that resists chemical breakdown.