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Dental fillings

In the treatment of dental cavities, after drilling out the cavities, dental fillings are inserted. The intent is to prevent further damage to the tooth and thus avoid the eventual need for the tooth to be extracted.

Amalgam

Amalgam fillings are an alloy of mercury (from 43% to 54%) along with silver, tin, and copper. Mercury-based fillings were apparently first used by French dentists in the 1810s. They continue to be used today because of their hardness and durability; and because they are cheap.

Mercury is toxic, and the use of amalgam fillings is therefore controversial, as the fillings do emit mercury as a minute amount of vapor. Various government agencies, including the UN's World Health Organization and the USA's Food and Drug Administration and Centers for Disease Control and Prevention have stated that amalgam fillings are safe, even for pregnant women, children, and diabetics, except in rare cases of allergy.

Composite resin

Composite resin fillings are a mixture of powdered glass and plastic resin, and are white-colored. They are considered strong and durable, and are closer to "normal" tooth color than silver-colored amalgam fillings. They are much more expensive.

Glass Ionomer Cement

These fillings are a mixture of glass and an organic acid. They are tooth-colored and they vary in translucency. They are usually used for small fillings, and are expensive (about as expensive as composite resin). The fillings do not wear as well as amalgam or composite resin fillings.

Resin-Ionomer Cement

These fillings are a mixture of glass, an organic acid, and resin polymer that harden when exposed to a blue light that the dentist uses to finish the treatment. (The light activates a catalyst in the cement that causes it to cure in seconds.) The cost is similar to composite resin. It holds up better than glass ionomer, but not as well as composite resin, and is not recommended for biting surfaces of adults.

Porcelain (ceramic)

Porcelain fillings are hard, but can cause wear on opposing teeth. They are brittle and are not usually recommended for molar fillings.

Porcelain Fused to Metal

These are metal shells with porcelain "enameled" on top, and is used for crowns. They are very durable.

Nickel or Cobalt-Chrome Alloys

These are mixtures of nickel and chromium and are used for crowns and bridges. They can be abrasive to opposing teeth and do conduct heat and cold, but have excellent durability.

Gold

Gold fillings have excellent durability, wear well, and do not cause excessive wear to the opposing teeth, but they do conduct heat and cold, which can be irritating. They are expensive.

Other historical fillings

Lead fillings were used in the 1700s, but became unpopular in the 1800s because of their softness and because lead poisoning was understood.

According to U.S. Civil War-era dental handbooks from the mid-1800s, since the early 1800s metallic fillings had been used, made of lead, gold, tin, platinum, silver, aluminum, or amalgam. A pellet was rolled slightly larger than the cavity, condensed into place with instruments, and then shaped and polished in the patient's mouth. The filling was usually left "high", with final condensation - "tamping down" - occurring through the patient's chewing of food. Gold was the preferred filling material during the Civil War, with amalgam being the most common due to cost. Tin was also popular due to cost, but was held in lower regard.

One survey [1] of dental practices in the mid-1800s catalogued dental fillings found in the remains of seven Confederate soldiers from the U.S. Civil War; they were made of:

Thorium - radioactivity was unknown at that time, and the dentist probably thought he was working with tin
Lead and tungsten mixture, probably coming from shotgun pellets
Tin and iron
Mercury amalgam
Three soldiers had gold fillings