A root canal treatment involves the removal and replacement of a tooth’s pulp. The pulp is pulpy tissue containing blood vessels, nerves and connective tissue.
- The pulp is found in a canal that runs through the centre of the hard tissue on the interior part of the tooth.
- The pulp expands from the pulp chamber in the crown down through the root canal to the tip of the root in the jawbone.
- A tooth has only one pulp room but may have more than one root and several root canals.
If pulp became damaged through wound or disease and cannot repair itself, bacteria and their products can leak into the pulp and cause the pulp to die. If a root canal procedure is not performed, an abscess can form at the tip of the root and cause severe pain. Even if there have no pain, the bone anchoring the tooth in the jaw can be damaged. If the treatment not performed, the tooth may have to be extracted.
It is well-recognized and universally accepted that a successful outcome in endodontic treatment essentially depends on three factors:
- Cleaning and shaping
- Three-dimensional obturation of the root canal system.
Requirements of the access cavity:
The access cavity must make the succeeding stride easier. It must therefore meet the following requirements:
- Permit the ejection of all the chamber contents:
One of the first steps for a favorable outcome in Endodontic is proper cleaning of the endodontic space, which comprises not only the root canal, but also the pulp chamber and its pulp horns. Cleaning should be as thorough as possible. Good endodontic cleaning , begins with the removal of the endodontic contents from the pulp chamber and its horns. To achieve this, it is necessary to completely remove the chamber roof. This allows the moving of all the pulp tissue, any calcifications, and all residue or traces of old filling material. If the chamber roof is not totally removed, it will not be feasible to perform proper cleaning of the pulp horns. There are two consequences:
- Contamination or infection of the endodontic area that the dentist is trying to clean.
- Stain of the endodontically-treated tooth (especially the front teeth).
To ensure sufficient removal of the roof above the pulp horns, one can use a small, curve probe. It is used to probe the walls of the access cavity for the presence of overhung.
- Permit complete, direct sight of the floor of the pulp chamber and canal openings:
The whole extent of the floor must be visualized, as its landmarks help in identifying the canal openings. This suggest particularly to the posterior teeth: the floor frequently has natural hollow, at the end of which the canal orifices are located.
To fulfil the second requirement, the access cavity must sometimes be slightly modified to give it the so-called “convenient shape”. Complete transfer of the roof, it is imperative to align the cavity slightly toward the dentist, particularly when dealing with the molars and patients with limited mouth opening. This permits the barriers a slight anterior inclination that facilitates inspection of the floor and thus localization of the canal openings.
Introduction of canal instruments into the root canal openings:
The pulp chamber floor of the posterior teeth frequently has grooves that serve as guides, not only to find the orifices of the root canals, but also to the introduction of endodontic instruments within them.
The floor is also completely convex and forms an acute angle with the chamber walls. If the access cavity has been effectively made and especially, if the chamber floor has not been affected by the cutting action of the bur, the instruments will enter the canals easily without encountering any obstacles. It adequate to slide the canal instrument along the wall at the point where the canal opening is located. The walls prepared by the endodontist and the floor created by Nature will guide the instrument toward the apex. If the external structure of the floor has been changed, resulting in flattening or irregularities, each introduction of an instrument must be checked with a mirror with the pulp chamber free of any medicated solution, to allow visualization of the canal orifice.
- Provide access as direct as possible to the apical one third of the canal for both preparation instruments and canal filling instruments:
Endodontic instruments should not be deflected by any obstruction in the crown. When working in the canal, they should shift freely, particularly in the apical one third.
For different reasons, the endodontic instruments should never touch the walls of the pulp chamber:
- They must be able to work on the entire circumference of the canal. An access cavity that is too narrow will force the dentist to work on only one wall of the canal, while the other remains completely untouched (Fig. 11.7). Deformations of the apical foramen may result.
- The friction of the instrument’s shaft opposed the coronal obstructions will have to be overcome. The force required to do so damage the Endodontist’s ability to sense how much the working portion of the instrument is engaged against the canal walls. This could easily lead to fracturing of the instrument.
- Provide a positive support for temporary fillings:
When the access cavity is temporarily closure to seal a medication within, the temporary cement must form an hermetic seal to avoid contamination of the cavity. The cement must be unaltered for the entire period of time required and it must not collapse into the chamber. To prevent this, the walls of the access cavity must be flared slightly in the shape of a funnel, so that the occlusal surface is slightly wider than the floor.