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What causes toothache?

Decay near to the pulp can potentially cause toothache

X-ray deep caries

Toothache is the common term for pulpitis, or inflammation of the tooth pulp. Tooth pulp is the living tissue found in ther central portion of the tooth and it is a fragile tissue that contains blood vessels, nerves and connective tissue. The pulp is protected by the encasing hard tooth structure from bacterial infection.  In the presence of decay, fracture, cracks or gum disease, the pulp tissue will be inflamed resulting in pulpitis/toothache.  If pulpitis is allowed to progress, the bacterial infection will cause the pulp to degenerate and there will be an infected space within the tooth and the inflammation could also spread out into the bone tissue around the root of the tooth.

What are the signs of needing root canal treatment?

The most common indicator will be pain from tooth. The painis typically described as lingering sharp pain to thermal changes or spontaneous pain in the evening. It can also be pain on biting. More obvious signs would be swelling and pus discharge from the surrounding gums.

There are some cases there can be no symptoms and signs will be detected as part of a thorough routine examination.

What is root canal treatment?

Root canal treatment can be done to relieve symptoms related to the infection or inflammation of the pulp. It is the disinfection and cleaning of the root canal space and filling up of the canals to prevent re-infection.

The procedure itself can be done in one visit and several sittings. It is routinely done with the placement of a rubber sheet so that the tooth can be isolated to prevent saliva contamination in the course of treatment. Several exposures for radiographs are required before, after and during the procedures to ensure that is performed in accordance to accepted standards.

It would involve an:
1) Access opening by using rotary burs

2) Cleaning and shaping of the canals using small files.

Diagnostic length x-ray

Inserion of the files to confirm that the canals were cleaned and shaped along the whole length of the canal

3) Filling of the canals usually with gutta percha (a rubber base material) and biocompatible cement.

Root fill x-ray

Usually root canal treated teeth will need a full restoration to protect it from tooth fracture. This will enable to tooth to resume its full function.

Is root canal treatment procedure painful?

There are several anaesthetic procedures that can numb the tooth before root canal treatment can proceed. In some cases, the inflammation may cause the site to be more resistant to anaesthetic and the clinician may need to adopt adjunctive measures to obtain adequate anaesthesia.

What do I expect after root canal treatment?

Transient pain can occur following root canal treatment and can be adequately controlled by oral medicine. In some uncommon instances, there can be swelling from the tooth following root canal treatment. The clinician will need to re-examine the tooth and decide the necessary follow-up therapy.

Does root canal treated teeth need special care?

Teeth that are root canal treated have a higher tendency to fracture because they are usually already heavily filled. Therefore do not bite hard foods before the tooth can be permanantly restored.

The root canal treated tooth should be maintained like any other tooth to prevent tooth decay or gum disease. Brushing and flossing should resume.

What are the complications that can arise from root canal treatment?

Most of the complications are limited to the well being of the tooth and its supporting structures.  Some of the common complications are listed below.

Sometimes after completion of root canal treatment, despite root canal treatment being appropriately performed and with no signs of infection or inflammation, the tooth may not feel as it used to be, eg.the tooth feels sensitive on biting or to touch.

Aberration of the tooth resulting in higher chance of procedural complications. To name a few-there can be calcification of the root canal space making root canal treatment challenging, very curved canals causing higher chance of instrument fracture, premature tooth or tooth with limited tooth structure that that may fracture during treatment. When such complications occur, the success rate may be affected and other additional follow-up treatment may be required.

Curved and long roots can increase the risk of fracturing instruments used to clean the canals


Curved root spacer

Calcification causes narrowing of the canal, increasing the chance of error when locating the canal


Calcified canal

Why does a root canal treated tooth sometimes require another round of treatment?

Root canal treatment usually has good success rates and it ranges, depending on the pre-existing condition of tooth.

When root canal treatment fails, it usually presents as persistent inflammation of the bone and may sometimes give rise to swelling and pus discharge. Below are some of the reasons why root canal treatment fails:

  1. Persistent or recurrent root canal infection. This may occur even a good root canal treatment has been performed. The assessment of re-treatment will be based on the quality of root canal filling, the status of the disease and the nature of the signs and symptoms.

  2. Defective fillings that may compromise the sealing ability of root canal fillings from bacteria.



Lost filling causing exposure of the root filling to the oral environment leading to reinfection

Failed root canal treatment

A tooth with persistent root canal infection despite root canal treatment


Redoing root canal treatment can be more complex as it can be complicated by the presence of materials that are challenging to be removed. It will then require more time and effort for good success. 

What is endodontic surgery/apical surgery/apicectomy?

The abovementioned is a surgical procedure that is required when there is:

  1. Persistent disease despite root canal treatment, this is usually because of complex root canal anatomy
  2. Teeth restored with post core retained crowns that may not allow conventional retreatment of the root canal.
  3. Exploratory purposes for teeth suspected to have a crack in the root.

This can be performed under local anaesthesia and will require cutting the gums to expose the inflammed or infected tissue. The affected tissue is then removed and the root are treated as well before the gums were sutured back.

periapical pathosis

Tooth with persistent infection as indicated by the dark area


spacer apic

Apical surgery to remove the root tip where the complex anatomy of the root canal system could harbour bacteria



Other situations that may require root canal treatment

What is Cracked tooth?

A cracked tooth is different from a fractured tooth. A cracked tooth means there is an incomplete fracture of the tooth. A crack is a separation of the deeper part of the tooth structure  and it propagates towards the pulp space and the gums. The extension of the crack is usually vertical in nature and not something that is routinely detected on radiographs.

Once the pulp tissue is involved, toothache results. It is often referred to as cracked tooth syndrome. Root canal treatment may be recommended to relieve the pain.

Sometimes the crack may be very advanced and it may not be worth the time, effort and cost to save the tooth, and extraction may be reocommended instead together with replacement options.

What is an Immature tooth? Does the root canal treatment of an immature tooth differ from a mature tooth?

The pulp tissue is responsible for maturation of the tooth. Maturation means continued development of the tooth roots. A mature tooth root will have thick walls and properly-formed root tip. Should an immature tooth require root canal treatment, the treatment will differ because the canal development is arrested before it is completed leaving a large open end that is not shaped  for a normal root canal filling.

Open Apex




Open end of the canal of an immature tooth

The cleaning methods can be easily modified while the root filling procedure needs more attention. There are several treatment methods for such teeth.  Some proven methods are as follows.

  1. Placement of a medicament to induce closure of the open canal (apexogensis) . This typically requires a few sessions over 3-6 months.

  2. Placement of a special material known as Mineral Trioxide Aggregrate (Apexification). This is a technological advancement that reduces the number of treatment visits
Root fill_open apex spacer Apex closure


Two radiographs (left) showing management of the open apex of the immature tooth

What are the different kinds of trauma to the teeth? How is it related to root canal treatment?

For simplification, trauma to the teeth can beclassified into 2 main categories. There are fractures of the tooth structure and loosening of the tooth within its socket. These can happen concomitantly. Both types of trauma can affect the pulp tissue and it may degenerate because the blood supply to the pulp is compromised or it gets infected via the tooth fracture.

For fractures of the tooth structure, they can further classified by the type of tooth structure involved. The clinician will need to check the extension of fracture and determine the need of root canal treatment before placing a full restoration.  Modifications of root canal treatment may be required for some of the fractured tooth.

For teeth that have been loosened, both the pulp and the surrounding tissue around the roots are affected. There are some mild cases that may not require root canal treatment yet and long term monitoring is required to ensure that the pulp tissue is not affected.  There are some severe cases like intrusion of the teeth or avulsion (where the tooth is totally knocked out of the socket), outcomes of such teeth may be considered poor.  The outcome and treatment for the different type of tooth loosening varies and the clinician should explain to you what the treatment options are and the likely outcomes for these traumatized teeth.