Root Canal Re-Treatment


Root Canal re-treatment is done if a previous root canal treatment has failed. Root canal re-treatment includes taking off the previous crown and cleaning the canals. It will then be refilled and a crown will be placed back on the treated tooth. A root canal re-treatment is basically the same as the original treatment other than the removal of the structure and its success rate is about 75%. Here at Smile Hub Dental Clinic in Bayside Medical Centre, we always try to keep teeth in cases where it is possible which is why we think root canal re-treatment is a good option for some patients instead of an extraction. Root canal re-treatment is a simple procedure which may only take 2 or 3 visits. If a tooth has enough bone and gums to support it and a solid surface there is a good chance that it can be saved. Other options if the tooth is extracted such as dental implants or bridges can be more expensive and harder to maintain.


A root canal may fail and need to be re-treated due to the following occurrences:

  • A crown has cracked and the filling material is leaking
  • Awkwardly shaped or thin canals have not been treated properly in the first treatment
  • A crown placement has been delayed after the root canal treatment
  • The tooth has new decay in it
  • A fracture has occurred in the root filled tooth
  • Saliva and bacteria had gotten into the restorative structure
  • Unnoticed complex canal structures


Before the root canal re-treatment starts, the patient will be given anaesthetic to numb the area. Here at Smile Hub Dental Clinic, we offer adult sedation for nervous patients so this can be an option for this treatment too. The tooth being treated will be surrounded with a rubber dam to keep the tooth dry and protected from saliva and bacteria. If the area is very inflamed or the treatment is difficult, there might be multiple appointments needed. If there is a post or crown placed it will be removed. The filling material blocking the canals will be taken out and the canals will be cleaned and reshaped with very small instruments. The dentist will take an x -ray to make sure that the roots are completely clean. If the treatment is difficult a medicated filling material may be placed and the patient will come back for a second visit. If the dentist is sure that the root canals are clean, they will fill the canals with a rubber material to seal the canals and prevent any bacteria getting in which may cause infection. A temporary filling or crown will be placed until the permanent crown is completed.


If you have any queries about root canal re treatment, please contact Smile Hub Dental Clinic at 01 5253888 or Book Online.

Frequently Asked Questions

Why do I need a root canal retreatment?

Root canal treatment is very successful but in some cases a patient may need a root canal re-treatment if their previous root canal treatment has failed. This depends on the particular case but it may be because the treatment has not healed correctly or an infection is present in the tooth.

Is root canal re-treatment painful?

The nerve has been removed in a tooth that has had root canal treatment. Even though there is no nerve a dentist will still use anaesthetic to numb the area so that the patient will not feel any pain during the procedure. After the numbness wears off there may be slight discomfort for a few days which pain killers can help with. It is recommended that the patient does not chew on anything hard on that side to prevent the tooth fracturing before the permanent crown is placed.

How do I know my root canal treatment has failed?

Some signs of a failed root canal treatment may include:

  • Pain in the area of the treated tooth
  • Sensitivity in the treated tooth
  • Swelling around the treated tooth
  • Pus leaking from the area
  • The tooth becoming darker in colour
  • An abscess beside the tooth
  • Problems with your sinus
  • An infection can be seen on an x-ray

How successful is a root canal retreatment?

How successful a root canal re-treatment is, depends on the pervious treatment of the tooth and the reasons of its failure. Usually, the success rate for a re-treated tooth can range from 75% to 88%.

How long does a retreatment root canal take?

A root canal retreatment usually takes around the same amount of time as the original treatment. A visit is usually between 30 to 60 minutes but can take longer if the case is difficult. If there is a lot of inflammation or the treatment is complex there may be more than one appointment needed to make sure the treatment heals correctly.

The average root canal treatment is 30 to 60 minutes long. More complex cases may take around 90 minutes. A root canal typically requires one or two appointments to complete.

What causes an infection in the root canal?

Teeth are made of outer enamel and dentin layers covering an inner dental pulp, in which there are blood vessels circulating nutrients for anatomical function and nerve endings transmitting nerve signals.

An infection of the inner tooth pulp is caused by tooth decay, bacterial infection, mycosis fungal infection, poor nutrition, excess sugar and acid diet, smoking, medication and serious health conditions including diabetes.

Damage to the outer enamel and dentin layers means that infection can enter the inner tooth. Once a tooth’s pulp is infected the infection can travel via the root canal system to other tooth roots and pulp inflaming oral tissue

Who is at risk of infection?

Individuals most at risk of infection are patients with tartar and plaque build-up on their teeth and those who do not maintain good oral hygiene or visit a dentist regularly. Bacterial and fungal growth can set in when food becomes trapped between the teeth from a lack of teeth brushing and flossing. These cause the start of infection and tooth decay, which breaks down the enamel and dentin layers and infects the inner tooth pulp.

People who consume excess sugar and high acid concentrations may experience enamel erosion and damage, exposing the dental pulp to infection. Poor nutrition and smoking are also linked to tooth decay. Certain medications may also trigger bleeding gums and erosion of tooth enamel. Side-effects are often listed on medication leaflets. Those on medication and with health conditions which impact oral health should notify their dentist to ensure proper care can be put in place.

What are the symptoms?

Patients with dental pulp infection may experience incessant tooth pain and sensitivity as the oral inflammation increases. If left untreated the toothache escalates with throbbing teeth, mouth and facial aches. Along with prolonged oral pain, bleeding and swelling gums, other symptoms include receding gums, loose teeth and bad breath.

Nerve endings in the pulp may also be traumatised, resulting in neurological symptoms of migraine or severe headaches, particularly if abscesses develop. People can also experience associated symptoms such as high temperature, fever and nausea. Chronic gum disease, periodontitis and/or necrotising ulcers may also form in the mouth.

What procedures are involved in root canal treatment?

An oral examination is initially carried out with diagnostic testing tools, such as X-rays, imaging and biopsy to isolate the cause of infection. The spread of dental pulp infection is tracked, so that the exact location of infected root canals can be identified. Once a patient consents to the root canal procedure a treatment date is set. The patient’s teeth will first be cleaned and a local anaesthetic is given to numb the treatment area for pain-free root canal treatment.

The oral surgeon then uses a dental drill to gently access the inner tooth pulp. A dental instrument is used to carefully scrape away the infected tooth root tissue. Based on the severity of infection and treatment required, the patient may need time to recover from the initial procedure before receiving further root canal treatment.

Once the infected dental pulp and tooth root tissue are removed, a dental substance known as gutta percha is inserted into the space to secure the tooth within the jawbone and prevent the return of infection. A dental crown may then be placed over the tooth surface to solidify structure and improve dental bite function.

What will happen if dental pulp infection is left untreated?

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Another random question?

When infection spreads through the dental pulp and root canals, the tooth structure is weakened and teeth are at higher risk of fracture. Some people experience bone or tooth loss and may require a bone graft. The infection can spread through the blood stream via the blood vessels in the dental pulp. Such infection can cause complications within the body for the autoimmune, circulatory and metabolic systems.

Physical infection may trigger high blood pressure resulting in an increased risk of stroke, heart attack and cardiac or vascular disease. Others may experience neurological conditions if the infection causes nerve damage. When infection spreads oral function, such as the ability to eat and bite, and nerve function deteriorate. The whole body is placed under pressure and weakens, leading in a rise of susceptibility to illness and disease.

Are there complications associated with root canal treatment?

Although all surgical procedures may result in bleeding and bruising or other side-effects, root canal treatment is designed to remove tooth infection and is less complicated than other procedures. Oral surgeons perform the procedure with expertise gained through experience and patients have pain-free treatment options. A patient’s medical history and health are always considered for risk management during the procedure.

Complications likely to arise due to ignoring dental pulp infection are far more damaging to your oral and overall health, particularly if there is damage to the immune system and neurological function. Painkillers are prescribed following the root canal procedure to ease any discomfort, with all risks and benefits discussed prior to treatment.

What alternative treatments are there?

If root canal treatment is not appropriate a dental surgeon may recommend apicectomy as a means to remove infected tooth root tissue. Tooth extraction is also a possibility but only in severely advanced cases. Dentists will try to preserve natural tooth structure where possible.


Prevention of dental pulp infection is the best alternative treatment. Eating a balanced diet with moderate sugar or acid intake, maintaining oral hygiene and attending regular dental check-ups are all vital for good dental health. You are also recommended to quit smoking if this is something you do.

How successful is root canal treatment?

Root canal treatment carries a 70 to 90 percent success rate, though further infection may not be totally eliminated. Individuals are responsible for their oral health condition and need to actively engage with dentists to maintain the health of their teeth and prevent damage to the tooth structure.

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    Smile Hub Dental Clinic, Bayside Medical Centre, Bayside Shopping Centre, Sutton, Dublin 13