When you visit your dentist to get a filling, you may be given local anesthesia to numb the area if necessary. Next, your dentist will remove decay from the tooth, using a drill.
A drill, which dentists call a handpiece, uses metal cones called burs to cut through the enamel and remove the decay. Burs come in many shapes and sizes. Your dentist will choose the ones that are right for the size and location of your decay.
At first, your dentist will use a high speed drill (the one with the familiar whining sound) to remove the decay and unsupported enamel of the tooth. Once the drill reaches the dentin, or second layer of the tooth, the dentist may use a lower speed drill. That’s because dentin is softer than enamel.
Once all the decay is removed, your dentist will shape the space to prepare it for the filling. Different types of fillings require different shaping procedures to make sure they will stay in place. Your dentist may put in a base or a liner to protect the tooth’s pulp (where the nerves are). The base or liner can be made of composite resin, glass ionomer, zinc oxide and eugenol, or another material.
Some of these materials release fluoride to protect the tooth from further decay.
If your dentist is placing a bonded filling, he or she will etch (prepare) the tooth with an acid gel before placing the filling. Etching makes tiny holes in the tooth’s enamel surface. The composite material fills in the holes as the dentist places the filling. A bonding material also is used, so the filling bonds to the tooth in two ways. Bonded fillings can reduce the risk of leakage or decay under the filling. Bonding is generally done with composite fillings.
Certain types of fillings get hardened by a special light. With these fillings, your dentist will layer the material, stopping several times to shine a bright light on the resin. This cures (hardens) the material and makes it strong.
Finally, after the filling is placed, your dentist will use burs to finish and polish the tooth.
*Source: Colgate Oral Care Center