Composite fillings are tooth coloured fillings. To the untrained eye you can’t see them in the tooth.
The fillings bond directly to the tooth, they can restore it virtually to its original strength. As the composite filling bonds directly to the tooth it leaves no margins for leakage so there are no areas where bacteria can get in to cause decay, unlike the silver (amalgam) fillings. Where the silver fillings are packed into the cavity, these can weaken the tooth, making it more susceptible to breaking. Repairing a broken tooth can be expensive and may require crowns/caps, so white fillings can save money in the long term.
Teeth filled with the composite fillings can be less sensitive to hot and cold foods/drinks than those restored with the silver fillings.
Composites are mercury-free. When preparing the tooth for a composite filling only a small amount of the tooth structure is removed, the size of the hole made for the filling can be dramatically smaller with composites.