TOILET OF THE CAVITY:
This is the act of freeing the preparation walls and margins from objects that may interfere with proper adaptability and behavior of the restorative material.
It comes under Coronal Cavity preparation principles which include other principles like – Outline form, Convenience form, Removal of any remaining caries and old restorative materials and the last Toilet of the cavity.
Toilet of the Cavity is accomplished by:
- Removal of all enamel and dentin chips due to excavation and grinding with warm water.
- Drying with an air syringe.
- Sterilization.
Toilet of the cavity is achieved by using Round burs, endodontic spoon excavators and irrigation with Sodium hypochlorite to clean the chamber, in the bed the chamber is wiped with cotton and air from a three-way syringe is used to dry the chamber. The air should not be directed towards the canals as Air might get trapped in the canals and cross the apex leading to Emphysema.
Englander et al have shown that silver nitrate and alcohol cause irreparable pulp damage if these are allowed to enter into the dentinal tubules.
Shay, Allen et al have shown that ZnOE, Ca(OH)2and fluoride content in some restorative material s show a certain amount of protection even on unsterilized condition of cavities.
to prevent materials and objects from entering the canal space. To make sure that any foreign materials do not enter into the pulp chamber before the restorative material is placed in it. If foreign materials enter the canal space they might block the apical portion of the canal thus leading to failure of the Root Canal Treatment.
Toilet of the cavity is performed before radicular preparation is started
What is Smear Layer:
Later based on research debridement comprised of cleaning the cavity with warm water so as to protect the smear layer formed. Smear layer prevents penetration of bacteria and their products further into the pulp-dentin complex through the dentinal tubules. Further treatment with caustic solution damages Smear layer.
The Advantage of having a Smear layer is that it helps in blocking the orifices of dentinal tubules thus decreasing the permeability of dentin, it is mostly impervious to bacteria but not completely, so if you completely remove the smear layer, the dentinal tubules are open and can form a clear pathway for the bacteria to pass through them along with other products which can diffuse through the tubules and lead to irritation of the pulp tissue.
isn’t smear layer bad !? they are always asked to be removed…
Smear layer, on the whole, has two properties, one is that it contains debris from a cut or prepared Dentin and on the other hand it forms a layer which helps in blocking the Dentinal tubules which are open. This blockage prevents the entry of any Bacteria or pulpal irritants through the dentinal tubules and thus protecting the pulp chamber.
So Smear layer is both good and bad and hence it has to be treated but not completely removed which might open up the dentinal tubules for the bacteria and irritants to seep through leading to Pulpal irritation.