The material used in restorative dentistry, often called “dental gold,” is indeed real gold, but it is never used in its pure 24-karat form. Gold is blended with other elements to create specialized alloys tailored for the harsh environment of the human mouth. This alloying process transforms the soft element into a resilient material suitable for long-term use in crowns, bridges, and inlays.
Understanding the Gold Alloy Composition
Dental gold must be an alloy because pure gold is too malleable and lacks the necessary mechanical strength to withstand the forces of chewing. The addition of other metals significantly increases the hardness, durability, and wear resistance of the final restoration. This specialized mixture may include copper, silver, platinum, and palladium, each contributing distinct properties to the material.
The composition of dental alloys is categorized based on the percentage of noble metals they contain. High-Noble Alloys represent the highest quality, requiring a minimum of 60% noble metal content, with at least 40% of that total being gold. These materials are favored for their superior resistance to corrosion and tarnish in the oral environment.
The second tier is Noble Alloys, which contain at least 25% noble metals but do not meet the higher gold content requirement. Finally, Base Metal Alloys contain less than 25% noble metals, with the bulk of their composition made up of elements like nickel, chromium, or cobalt. The specific percentages of these alloying metals are controlled, as variations can change the material’s performance.
Material Science: Why Gold is Used in Dentistry
Gold alloys are utilized in dental restorations for their exceptional physical and chemical properties, not just aesthetics. A primary characteristic is their superior biocompatibility, meaning the material is non-toxic and resists corrosion when exposed to saliva and other oral fluids. This inertness prevents adverse reactions, ensuring the long-term health of the surrounding gum and bone tissue.
The material also exhibits excellent malleability, allowing dental technicians to cast and shape the alloy into an extremely precise fit against the tooth structure. This ability to create tightly sealed margins is paramount, as it prevents bacteria and plaque from leaking underneath the restoration, which could lead to secondary decay. Furthermore, gold alloys have a coefficient of thermal expansion that closely mirrors that of natural tooth enamel.
This similar expansion rate means the restoration and the tooth expand and contract at nearly the same rate when subjected to temperature changes. This synchronization minimizes the risk of micro-fractures or the loosening of the restoration over time. The high resistance to fracturing ensures the crown or filling can withstand years of heavy occlusal forces.
Determining the Financial Value
The financial worth of dental gold, typically assessed as scrap material, is determined by the total content of precious metals and the current market price. The value of a removed crown or filling depends on its weight and its percentage of gold, palladium, and platinum. This purity is often expressed in karats for resale, with many gold dental crowns falling into the 16K to 18K range (66.7% to 75% gold purity).
Because dental alloys are complex mixtures, a specialized refining process known as an assay is necessary to accurately determine the exact metallic composition. This scientific analysis identifies the precise amounts of all precious metals present, ensuring the seller receives a fair price for all valuable elements, not just the gold. The final payout is a calculation of the weight of the pure precious metals multiplied by their respective daily market prices, minus the refiner’s fee.