Maxfacts

The pulp maintains a tooth’s nociceptive (denoting pain from stimulation) and sensory function. It may become inflamed due to the ingress of microorganisms from dental caries , through a crack in the tooth, or due to trauma, orthodontic movement or occlusal trauma. Inflammation can also be caused by chemical or mechanical irritation from dental treatment.

Root canal treatment aims to remove infected pulp tissue as completely as possible from the complex root canal system.

Assessment

Assessment should be thorough to ensure an accurate diagnosis is reached and should involve the following steps:

• history;
• examination (swelling, sinus, mobility, tenderness to percussion, caries, restoration, occlusion, periodontal status);
• vitality testing of tooth (cold, heat, electric pulp vitality testing (EPT));
• X-ray radiographs;
• diagnosis (reversible/irreversible pulpitis, necrosis , acute periapical periodontitis, abscess.

Indications

• following trauma (avulsed permanent tooth , complicated fracture , loss of vitality);
• pulp necrosis;
• irreversible pulpitis;
• restorable tooth;
• functional tooth;
• rubber dam can be applied;
• aesthetic zone.

Contraindications

• unrestorable tooth;
• unable to apply rubber dam.
 

Risks and other considerations

The risks of endodontic treatment include, but are not limited to:

• blockages of the root canal space which cannot be overcome with instruments;
• instrument separation/fracture within the canal;
• perforations of the canal;
• pain or discomfort following treatment;
• incomplete healing or failure of treatment;
• postoperative infection requiring further treatment or tooth extraction;
• tooth or root fracture which may require an extraction;
• fracture, loosening or chipping of the tooth or existing crown;
• change in sensation/numbness which may be permanent;
• adverse reactions to materials, chemicals, medications or local anaesthetics used.

Aims of treatment

Root canal treatment (RCT) requires thorough cleaning and shaping of the root canal system and provision of a good coronal seal. There are four crucial factors which improve RCT outcome:

• absence of a periapical lesion preoperatively;
• apical extent of the root filling 0 to 2 mm from the apex;
• the quality of the root filling;
• post-treatment restorative status.

An ideal preparation involves both chemical and mechanical irrigation, with a funnel taper shape. The three-dimensional contour of the tooth root canal space should be followed and the filling material should be well compacted to minimize spaces available for bacterial colonisation.

Common errors in root canal treatment are incomplete débridement either due to a short working length, inadequate time spent irrigating the space, missed canals, perforations, formation of ledges or elbows within the canals and apical transportation.

Procedure

• Diagnosis - imaging should allow for an estimated working length to be determined.
• Anaesthesia - this can be more challenging to achieve if there is infection present due to the acidity of pus. However, multiple techniques are available and this should not prevent treatment being attempted initially. Aside from the routinely used infiltrations and nerve blocks, techniques may include intraligamentary injections, intraosseous and intrapulpal anaesthesia.
• Tooth preparation - for example caries removal and building up the tooth to accommodate a rubber dam; this should be done before commencing root canal treatment.
• Rubber dam placement - essential to prevent ingress of oral bacteria into the root canal space, to protect the oropharynx from instruments, chemicals and debris. Also aids visualisation and moisture control when required.
• Access - the tooth should be accessed in a way that conserves as much tooth structure as possible whilst allowing good visualisation of the pulp spaces. Good lighting and magnification are recommended.
• Chemical and mechanical preparation - this can be with hand or rotary instruments, chemicals commonly used are sodium hypochlorite, NaOCl, and chlorhexidine gluconate. Copious irrigation is mandatory. Not only does this disinfect the canal, it prevents debris blocking the canal system and helps to flush away necrotic pulp and bacteria, as well as dentine chips. The whole canal system should be cleaned and necrotic pulp removed. The canal should be shaped to a tapered funnel, respecting the three-dimensional anatomy of the canal. X-ray radiographs may be necessary as well as the use of an apex locator to ensure the files are in the correct place and reaching the apex of the tooth. Most clinicians will ‘scout’ the canal first using a very fine file to the estimated working length of the tooth, before increasing the size of the files used to create a ‘glide path’. The coronal two thirds can then be flared, allowing for débridement and entry of irritants in to the canal system. Finally, the apical third can be prepared and the full canal shaped to a funnel taper.
• Obturation - the canal should be sealed with a sealant material (for example, Ca(OH)₂ or eugenol-based) plus in most cases gutta percha. This can be packed through cold lateral condensation, heated up and soft points inserted in to the canal, or a flowable form injected. An X-ray radiograph may be useful to check that the gutta percha filling is in the correct place both before sealing it, and before cutting it back. Excess gutta percha should be cut back, sealed (often by a flowable composite or resin-modified glass-ionomer cement (RM-GIC)) and the tooth restored. There are many different options for restoration of the tooth following obturation, including composite restorations, inlays and crowns.
• A final obturation X-ray radiograph is normally taken to assess the final result. However, this is a two-dimensional representation of a three-dimensional object and it will not be possible to see the entire tooth from all angles. The radiographic apex may also appear to be in a different location to the actual apex of the tooth.

The root filling material should be within 0 to 2 mm of the apex of the tooth for the best success rate. Within this distance the success rate was found to be 94 % compared with 76% for beyond the apex, and 68% if short by >2 mm. If the root is underfilled this leaves voids for fluid accumulation and bacterial proliferation, apical leakage and proliferation of a periodical infection. When overfilled, the material can push necrotic debris beyond the apex, causing inflammation or a foreign body reaction.

Restoration

The coronal seal is a crucial factor in the success of a root canal treatment. A good root canal treatment with a good coronal seal is the gold standard, however a poorer root canal treatment may still succeed if the coronal seal is adequate. The coronal seal prevents further ingress of bacteria in to the root-treated space and protects the tooth, which is often weak and vulnerable to fracture due to being ‘hollowed’ out in the process of root canal treatment.

Success

According to the European Society of Endodontology (2006), the criteria for success when assessed at one year (or four years if uncertain outcome) are as follows:

• favourable - no sinus / pain / swelling / loss of function, and X-ray radiograph shows normal periodontal ligament (PDL) space;
• uncertain - residual periapical lesion, remains the same or partially resolves;
• unfavourable - infection, periapical lesion formation, existing lesion expands, four years without resolution, root resorption.

X-ray radiographs should be taken at one year after treatment to assess the periodontal ligament space, the periapical status and bone levels around a root-canal treated tooth.