A dental filling is a procedure used to fill a hole, or cavity. It is the treatment for a tooth damaged by caries. Filling will help to restore the tooth back to its normal shape and function. It will prevent further decay. It is one of the most common dental procedures that takes place in a dental office.

Treatment of caries.
When bacteria eat away the tooth enamel and causes a hole, it is called a cavity. Smaller cavities are usually repaired with dental fillings.
During this procedure, your dentist removes the decayed portion of your tooth, then fills in the hole with filling material. This halts the progression of tooth decay and reduces the risk of further damage.
Fillings are also placed after trauma like chipped enamel, fractures, deep cracks to prevent them from spreading further. Fillings are placed to prevent further erosion of enamel surface due to poor handling of teeth – opening hard objects, biting nails, erosion from acidic foods etc
Silver vs tooth-colored fillings
Amalgam fillings are cheaper than any other kind
The main drawback of amalgam is the metal color. Many people do not like others being able to see their fillings when they laugh or smile.

Amalgam is quick and easy to place compared to other types of filling.
However, because it does not chemically bond with the tooth, which means some of the healthy tooth structure has to be removed in order to prepare a space that will keep the filling secure.
It is a more invasive type of filling, one which can weaken the tooth structure and increase the risk of tooth fractures.
Composites are shaded to match the natural tooth color as closely as possible, making them almost undetectable. Over time, however, resin composite can stain and become more noticeable. It can also shrink slightly, if not set properly, creating small gaps that harbor bacteria.

The process for placing composites requires more time and skill than amalgam. The tooth surface must be kept completely dry while the surface is etched, and the filling is built up in layers which are cured one at a time. One benefit of composite is that it chemically bonds to the tooth structure which offers extra support and means that no additional healthy tooth has to be removed in the process.
Several studies have shown composite fillings to be about as durable as amalgam.
Composite fillings may be more likely to fail than amalgam fillings. However, the main cause of failure was found to be recurring tooth decay, not fracture of the fillings.
Dental amalgam also contains mercury, which has raised concerns about it being toxic. Mercury can enter the environment when old amalgam fillings are replaced. Composite resin avoids these concerns, as it does not contain mercury.
Since some governments around the world have agreed to phase out amalgam, composite fillings have continued to become more common.
For a long time, amalgam was regarded as the best direct filling material in terms of strength and durability.