The question of whether gold fillings contain mercury is common, stemming from public concern about metals in dental work. The direct answer is that gold fillings, also known as cast gold restorations, do not contain mercury. These restorations, which can take the form of inlays, onlays, or full crowns, are made from specific metal alloys. Their composition is entirely free of mercury, distinguishing them from other dental filling options.
The Clear Answer: What Gold Fillings Are Made Of
Gold fillings are not crafted from pure, 24-karat gold. The soft, malleable nature of pure gold would not withstand the forces of chewing and could easily deform in the mouth. Instead, they are fabricated from specialized gold alloys, which are mixtures of gold and other metals engineered to provide the necessary strength and resistance for a long-lasting dental restoration.
Dental gold alloys are classified based on their noble metal content, which includes gold, platinum, palladium, and silver. “High noble” alloys contain at least 60% noble metals, with a minimum of 40% gold. “Noble” alloys contain at least 25% noble metals.
The remaining composition includes metals like copper, silver, and platinum, which are added to increase the material’s hardness, strength, and resistance to corrosion. Copper and silver increase the alloy’s strength, while palladium can improve color and corrosion resistance. This precise blend ensures the final restoration is biocompatible and durable in the oral environment.
The Source of Confusion: Understanding Dental Amalgam
The public’s association of mercury with dental fillings relates to a different material entirely: dental amalgam. Dental amalgam is a restorative material used for over 150 years and is often referred to as a “silver filling” due to its appearance. The presence of mercury in amalgam is what causes the confusion with gold restorations.
Dental amalgam is composed of liquid, elemental mercury mixed with a powdered alloy. The powdered alloy is primarily made of silver, tin, and copper. By weight, approximately 50% of the final set dental amalgam is elemental mercury.
The mercury serves as a binder that reacts with the alloy powder to create a strong, durable, and hard filling. This property allows the dentist to pack the soft mixture into a cavity before it hardens.
Durability and Longevity of Gold Restorations
The composition of gold alloys is chosen to provide exceptional functional and physical advantages in the mouth. Gold has a long history in dentistry because of its resistance to corrosion from oral acids and its inertness to body chemistry. This high stability means the restoration is less likely to break down or oxidize over time.
Gold restorations are renowned for their strength and superior load-bearing capability, making them highly effective in areas that endure heavy chewing forces, such as the molars. The metal’s slight malleability allows it to absorb stress without chipping or cracking, which is a common issue with more brittle materials. Gold also wears down similarly to natural tooth enamel, helping preserve the opposing teeth from excessive wear.
With proper care, gold crowns, inlays, and onlays have a remarkable lifespan in indirect restorations. Clinical studies frequently report survival rates for gold restorations that exceed 15 to 20 years. This long-term clinical performance supports the material’s continued use for reliable, high-stress restorations.