Cavity preparation is the controlled removal of carious (decayed) tooth structure followed by precise shaping of the remaining hard tissue to receive a dental restoration. Sometimes called tooth preparation, it establishes the mechanical and biological foundation for a filling, inlay, onlay, or crown.
Why Cavity Preparation Matters
The design of a preparation directly influences how well—and how long—a restoration functions. A poorly shaped cavity can lead to microleakage, secondary caries, or premature restoration failure. A well-executed preparation removes all infected dentin while conserving as much healthy tooth structure as possible, a goal central to minimally invasive dentistry.
Proximity to the pulp chamber is another critical consideration. When decay approaches the pulp, the clinician may place a protective liner or base material before seating the final restoration to guard against thermal sensitivity and pulpal inflammation.
Key Steps in the Procedure
Although technique varies by case, cavity preparation generally follows a defined sequence:
- Outline form: Defining the external shape of the preparation based on the extent of caries and the access needed for instrumentation.
- Resistance form: Shaping internal walls so the tooth can withstand occlusal forces without fracturing.
- Retention form: Creating features—such as slight undercuts or surface roughening—that resist displacement of the restoration.
- Convenience form: Adjusting access to allow accurate placement of instruments and restorative material.
- Finishing and toilet of the cavity: Removing residual soft carious dentin, refining enamel margins, and cleaning the site before restoration placement.
Rotary carbide or diamond burs mounted on a dental handpiece are the primary cutting instruments. In delicate zones near the dentinoenamel junction (DEJ), spoon excavators and other hand instruments may be preferred to minimize the risk of inadvertent pulp exposure. The choice of restorative material—composite resin, amalgam, ceramic, or glass ionomer—also dictates preparation geometry, since each material carries specific requirements for wall angulation, depth, and surface character.
Meticulous cavity preparation, guided by sound knowledge of tooth anatomy and material science, is the single factor most predictive of a restoration that seals reliably and endures the daily demands of the oral environment.