What is a root canal therapy

When is root canal therapy necessary?

In order to understand what a root canal therapy is, knowledge of some dental anatomy can be useful. On the inside of a tooth, under the white enamel and the layer of hard tissue called dentine, there is a body of soft tissue called pulp. Dental pulp, which is limited to the inside of a tooth, is commonly identified as the “tooth’s nerve”, but it is actually a highly specialized connective tissue which includes arteries, veins, nerve endings and connective tissue cells (Fig. 1).
A fully formed tooth, that has completed its development, will be able to survive for a long time even without its pulp because it will continue to be nourished by the surrounding tissues.
Following deep caries and its relative bacterial contamination, or following trauma, the pulp will become infected and inflamed: this is the, often clinically painful, condition of pulpitis.
The acute or chronic inflammation (that is to say more or less rapid in its evolution) can spread from the root apex to the surrounding alveolar bone, causing a lesion such as an abscess, a granuloma or a cyst which will be visible on the radiograph as a dark area (bony rarefaction) around the radicular apex (Fig. 2).  In cases like this the indication for endodontic treatment is absolute, since it is the only viable alternative to tooth extraction.
Another indication for endodontic treatment is represented by the need to redo a previous root canal therapy that has failed or was badly executed: an endodontic retreatment.

What is an endodontic treatment ?

An endodontic treatment consists of the removal of pulpal tissue from both the crown and the roots (Fig. 3) and its replacement with a permanent obturation in guttaperca and root canal cement, after having adequately disinfected and shaped the root canals (Fig. 4). The tooth will then be reconstructed with a filling, an inlay or a crown to protect it from any possible fractures or chips. Once the tooth has been restored, it will continue to be as functional as any other tooth.
Endodontic treatment, therefore, has a role in maintaining a natural smile, masticatory function and it also avoids having to rely on more expensive, more invasive treatment. When performed correctly, it will allow one to keep the treated tooth exactly the same as ones other natural teeth, even for the rest of  ones life.

How long is an appointment?

An endodontic treatment may be quite lengthy especially for molars, because depending on the case it might require one or more appointments. The operative times for endodontic treatment are as follows:

  • Local anaesthesia (the entire treatment is painless and anaesthesia shouldn’t be necessary if the pulp is necrotic or in the case of a retreatment).
  • Temporary reconstruction of the crown if it is entirely or partially missing, so as to obtain optimal conditions for isolation of the operative field.
  • Isolation of the operative field using the so called “rubber dam”. It consists of a rubber sheet that is kept stretched by a metal frame and is held in place by a clamp (Fig. 5).
  • It’s function is to isolate the tooth from saliva but above all it avoids dangerous ingestion or inhalation of disinfectants and sharp instruments.
  • Opening of the pulp chamber through the dental crown.
  • Location of the root canals.
  • Measurement of the length of each canal (from the crown to the opening at the root apex) using an electronic apex locator and an intraoral radiograph. The radiation dose absorbed by patients during dental radiography is minimal (consider that, for radiation close to the eye, to start having a lesion on the crystalline lens you would need 10.900 intraoral radiographs). The cost/benefit ratio is in favour of the benefits and therefore towards a correct root canal therapy.
  • Root canal preparation using endodontic instruments that remove radicular pulp, bacteria and infected matter, simultaneously creating a conical shape that is suitable for filling with the obturation material.
  • Rinsing with sodium hypochlorite, a powerful antiseptic and solvent of proteinaceous matter (bacteria and pulp residues), to achieve an environment as aseptic as possible.
  • Three dimensional obturation of the root canals using guttaperca, a material that is malleable with heat, together with root canal cement (Fig. 6).
  • Temporary filling
  • Radiographic follow-up at the end of the therapy.
  • Tooth reconstruction

Lastly, especially when treating premolars and molars, it’s strongly recommended to prosthetically cover the cusps with a crown or an inlay (Fig. 7,8), so as to avoid any coronal or radicular fracturing of the tooth, that has been weakened by preceding caries and (even if minimally) by the procedures necessary to perform a correct endodontic therapy.

Will it hurt?

During an endodontic treatment pain is completely absent thanks to local anaesthesia and even when it isn’t used (teeth with necrotic pulp and retreatments) intra-operatory pain is non-existent. For two or three days following root canal therapy there is almost always an aching sensation that subjectively  can be more or less intense. It can be dealt with any sort of analgesic. In very rare cases, in badly infected roots, the mobilization and passage of bacteria beyond the apex may cause a painful abscess to develop; the onset of this complication does not compromise the success of the endodontic therapy underway. In these cases it will be necessary to drain the abscess through the canals: this can obviously be done by attending the practice for a brief appointment.

What will endodontic treatment achieve?

Recovery of your tooth and the possibility of its functional re-integration (with a prosthetic restoration) in your dental arch.
The success rate for a correctly performed endodontic treatment is, under normal conditions, very high, it’s very close to 100%, more so than just about any other medical or surgical therapy. The success rate diminishes for retreatments, which are done when an inadequate root canal therapy was previously performed (short canal obturations, instrumentation errors, presence of anatomical variants, etc.).
In these cases it’s possible to intervene surgically by means of an apicoectomy followed by a retrograde obturation which noticeably increases the success rate.