At first, the dentist breaks through the hard enamel layer with the aid of a high-speed aerator (which makes the familiar humming sound). The aerator is carefully cleaned of caries and the area where the filling will be placed is determined. When the dentist reaches the dentin, the second layer of the tooth, he starts using a contra-angle handpiece at a slower speed because the dentin layer is softer than enamel. During the cleaning phase, the dentist makes sure that all the caries are cleaned by using a hand tool. When all the caries is cleaned, the dentist shapes the cavity and prepares it for filling.

Different shapes are required for each different filling. The dentist may use a base or sealant to protect the nerve of the tooth. The base or cover may be made of composite resin, glass ionomer, zinc oxide, eugenol, or another calcium-based material. Some materials release fluoride to protect the tooth from caries.

If the dentist is going to place a composite filling, he may first need to prepare the tooth using acid gel. Etching opens tiny pores on the surface of the tooth (especially in the enamel layer). These pores allow the filling to adhere tightly to the tooth. Today's developments have produced single-stage agents that do not require the use of phosphoric acid used, but there is still debate that they cannot achieve the roughening caused by phosphoric acid in composites.