When you have been diagnosed with a cavity, your dentist will need to create an opening in your tooth to remove the decayed substance and restore your tooth with a filling. This is called a cavity preparation. You may also need a preparation when your tooth has a fracture, abrasion or erosion on the tooth surface.

Your dentist will examine your teeth and take x-rays to determine the subtle design features necessary to ensure longevity of your filling. These design features include the shape and size of the opening into your tooth, enabling the dentist to remove the decayed substance, as well as design features to prevent the filling from moving or fracturing. There may be times when the dentist will need to remove a bit of healthy tooth structure in order to gain access to the decayed material. 

Cavities can be broken up into six different groups, or classes, depending on which tooth surface, or surfaces, are affected. This is a general illustration of the six classes, but depending on the level of decay, each class may involve more surfaces, or even a combination of classes.

For each of these cavity preparations, the dentist will first clean and numb the affected area. The dentist will use several different instruments to first create the opening, and then remove the decayed material. Once complete, the cavity must be rinsed and cleaned of any remaining debris in preparation for the filling. 

The cavity will either be filled with amalgam, which is a silver filling, or resin composite, where the filling is similar to the colour of the tooth. The decision as to which material to use is based on the tooth location and affected surface, as well as patient preference when aesthetics are of concern.

A well-prepared tooth with good design features incorporated will provide you with a long lasting cavity restoration.