Amalgam Class I Calculator

Amalgam quantity for class I cavities

Dental amalgam is a metallic alloy of silver, tin, copper and mercury, with mercury making up about half the mass. How much you need for a class I (occlusal) cavity tracks the cavity volume: m ≈ V × ρ, the mercury-free amalgam alloy sitting around ≈ 10–11 g/cm³ in density. In a small class I cavity a dentist usually condenses somewhere between 0.5 and 1.0 g of amalgam, so 1 to 2 capsules. Given depth p and occlusal area A, a quick estimate of volume is V = A × p.

What amalgam has going for it is durability of 15–20 years, high compressive strength and a low price, which is why it still shows up in posterior restorations within public health systems. The downsides: its metallic esthetics, a non-starter on anterior teeth, plus the long-running scientific argument over elemental mercury vapor release. The Minamata Convention (2013) set off a global phase-down, and in Brazil ANVISA regulates dental materials under RDC 478/2021.

Applications

Clinics and dental schools use it to estimate how much material they go through, public oral-health programs (SUS) use it to plan stock, and either way it helps when you need to work out cost per procedure. The CFO still authorizes amalgam, though esthetic alternatives such as composite resin and glass ionomer keep gaining ground. Note that encapsulated, pre-dosed amalgam is mandatory; handling bulk mercury by hand is forbidden.

FAQ

Is amalgam still safe? Regulatory bodies (FDA, WHO, ANVISA, CFO) consider it safe for most patients, while advising caution with pregnant women, children under 6 and people with kidney disease. An existing restoration shouldn't be removed unless there's a clinical reason to.

Amalgam or composite resin? Amalgam lasts longer and costs less. Composite is esthetic, mercury-free and bonds to the tooth, which preserves structure. On posterior teeth in adults under heavy masticatory load, amalgam is still acceptable. In esthetic zones, resin is the clear choice.

Does this calculator replace clinical judgment? No. The volume figure is only a rough estimate, and the dentist has to adjust it according to how the cavity was prepared, the isolation in place and the condensation technique used.