Biological Principles of Tooth Preparation help in preserving the health and integrity of the remaining tooth structure, where the Principles of Tooth Preparation deal with obtaining the proper shape, retention, resistance form of the cavity for restoration. The main principles of cavity preparation are to preserve the underlying tooth structure, protect the pulp tissue, save as much as Enamel or Dentin as possible, shape the cavity to achieve maximum resistance and Retention as possible depending on the type of restoration used to help in bearing the mastication forces.
The Biologic Principles of Tooth Principles are divided into three parts:
- Protection of the Pulp
- Prevention of Caries Recurrence
- Aseptic Procedures
During Cavity preparation the pulp tissue must be protected against the frictional, mechanical or thermal forces of the hand or rotary instruments. There are certain steps which must be followed –
- The burs must be placed parallel to the recessional lines of pulp to prevent cutting across the lines.
- Preserve as much Enamel or Dentin as possible by restricting the tooth preparation pulpally and facio-lingual.
- Avoid excess pressure while using a Rotary instrument – Temperature and Pressure limits during cavity preparation
- Avoid use of any chemicals at the cavity floor which can be harmful to the pulp underneath
- Use copious amounts of water during cutting to prevent heat generation
- Use of Large round burs with micro motor at low speeds is recommended while removing soft dentin which is close to the Pulp.
Prevent Recurrence of Caries:
Complete Caries removal and preventing the recurrence of caries is one of the most important step of Cavity preparation and restoration of the tooth, as it is done to preserve the vitality of the tooth. So to prevent Recurrence of Caries the following steps should be followed during cavity preparation –
- Remove all Carious enamel of dentin, any remaining caries can lead to secondary caries under the restoration.
- Remove all undermined enamel
- Include all the caries susceptible surfaces in the cavity preparation by extending the cavity such as Pits and Fissures.
- Based on the physical characteristics of the type of Restorative material being used, the cavo-surface angle needs to be corrected.
Following strict Sterilization protocols is a must in any cavity preparation procedure. It helps in achieving the desired result after restoration if proper asepsis is followed. The following Aseptic steps should be followed during Cavity preparation –
- Use of Sterilized cavity preparation instruments
- Use of Clean instruments without any debris from the previous case
- Isolation of the operative field using a Rubber Dam or Cotton Rolls.
- Proper Sterilization of the operator and assistant
The choice of Restorative material plays an important role in the cavity preparation, in case of Bonded Restorative materials such as GIC or Composite minimal tooth preparation is required, while Amalgam requires extensive tooth trimming to achieve mechanical retention. So it is best to Avoid Amalgam restoration in minor carious restorations which can help in minimal tooth trimming and preserving as much tooth structure as possible. Instruments used for Cavity preparation also change with the type of Restorative material used.