Short answer: Root canal retreatment means removing the old root canal filling and cleaning and filling the canals again when a tooth that has already had a root canal does not heal or develops an infection again. The main signs are pain when biting, swelling or a pimple-like discharge on the gum, and inflammation at the root tip seen on an X-ray. In suitable cases it is an option that allows the tooth to be saved.
Root canal treatment is one of the most common ways to save an inflamed or infected tooth without extracting it, and in most cases it gives trouble-free results for many years. In some teeth, however, healing does not happen as expected, or problems reappear years later. What comes up in this situation is root canal retreatment, the procedure of redoing the root canal. In this article we look at why root canal treatment can fail, which symptoms need attention, how retreatment is done and the alternative options.
Why does root canal treatment fail?
The most common reason root canal treatment fails is that bacteria remain inside the root canals or that bacteria leak back into the canals after treatment. A tooth's root canal system is often much more complex than people think; alongside the main canals there may be thin lateral canals, curves and branches. It is not always possible to clean and fill all of these structures.
The main causes that can lead to failure are:
- An extra root canal that was not detected in the initial treatment
- Canals that were not cleaned well enough or not filled to their full length
- The filling or crown on top being placed late after root canal treatment, or leaking over time
- New decay developing in the root canal-treated tooth
- A broken instrument fragment inside the canal blocking cleaning
- A crack or fracture forming in the tooth or root
Some of these causes appear over the years. For example, a sound root canal treatment can become reinfected when the filling over it wears down over time and starts to leak. That is why sealing the tooth on time and without leakage with a suitable filling or crown after root canal treatment is at least as important to the success of the treatment as the root canal procedure itself.
What are the signs of a failed root canal?
The most common sign of a failed root canal is pain felt when pressing on the tooth or biting. In addition, the following signs may also occur:
- Swelling of the gum in the area of the tooth
- A pimple-like bump on the gum that occasionally drains (fistula)
- A feeling that the tooth is taller than the others, tenderness to touch
- A bad taste or odor
- Swelling of the face or under the jaw
An important point is that a failed root canal does not always cause symptoms. In some teeth, inflammation developing at the root tip stays silent for a long time and is noticed only on an X-ray taken during a routine check-up. That is why it is recommended to monitor root canal-treated teeth with X-rays at regular check-ups. Not every shadow seen on an X-ray necessarily requires new treatment; an area that is healing can look similar. The assessment is made by comparing with previous X-rays and together with the clinical findings.
How is root canal retreatment done?
Root canal retreatment is the procedure of completely removing the old root canal filling from the tooth, reshaping and disinfecting the canals and filling them again. It often takes longer than the initial root canal and is technically more difficult, because the dentist first has to remove the materials used in the previous treatment.
The procedure usually proceeds through the following steps:
- Assessment: The cause of the problem is investigated with a clinical examination and X-rays. In complex cases, a three-dimensional CT scan can help assess missed canals or root cracks.
- Accessing the tooth: Local anesthesia is given. If the tooth has a crown or a post inside the canal, these may need to be removed to reach the canals.
- Removing the old filling: The filling material in the canals is removed with special instruments and solvents. If there is a broken instrument fragment, an attempt is made to remove it or bypass it.
- Cleaning and disinfection: The canals, including any missed canals, are reshaped and rinsed with disinfectant solutions. Magnification devices and a microscope are important aids at this stage.
- Intracanal medication: Depending on the state of the infection, medication may be placed in the canals for a period and a second visit planned.
- Filling and sealing: The canals are filled again and the tooth is sealed with a temporary or permanent filling. Then, depending on the tooth's structure, a permanent filling or crown is placed.
Mild tenderness lasting a few days may occur after the procedure. Healing is monitored over months with X-rays taken at follow-up appointments.
After retreatment, sealing the tooth permanently should not be postponed. When temporary fillings stay in the mouth for a long time, they can wear down and allow bacteria to leak back into the canals. In back teeth, especially root canal-treated teeth with a large loss of tooth structure, a crown may be recommended to protect the tooth against chewing forces. Completing this stage is an important step that supports the long-term success of retreatment.
Alternatives: apicoectomy and extraction
When root canal retreatment is not possible or not sufficient, the main alternatives are apicoectomy and extraction of the tooth.
Apicoectomy (root-end surgery): A procedure in which the gum is opened to reach the root tip, the inflamed tissue is removed, a small portion of the root tip is cut off and the end of the canal is sealed. It may be preferred when accessing the inside of the canal carries risk, for example when the tooth has a crown in good condition and a long post, or when there is no healing despite retreatment. It is done under local anesthesia.
Extraction: If the tooth has a vertical root fracture, if too little tooth structure remains for the tooth to function or if gum and bone support has been severely lost, saving the tooth may not be possible. In that case, the tooth is extracted and the resulting gap can be filled with an implant, a bridge or a removable denture.
Which option is suitable is determined by considering together the tooth's structural condition, its importance in the mouth, the gum and bone support and the patient's preferences. Keeping your own tooth is usually the priority whenever possible.
What is the success rate of root canal retreatment?
The success of root canal retreatment varies from case to case; however, scientific studies have shown that with retreatment done in suitable cases, a significant proportion of teeth can continue to function in the mouth for a long time. The main factors affecting success are:
- The size and duration of the inflammation at the root tip
- Whether missed canals can be found and cleaned
- The presence of additional problems inside the canal, such as a broken instrument or a perforation
- Whether there is a crack or fracture in the root
- Sealing the tooth on time with a leak-proof filling or crown after treatment
Based on the examination and X-ray findings, your dentist will share with you the possible options for your tooth and the pros and cons of each. You can find answers to frequently asked questions about root canal and other treatments on our frequently asked questions page; for technical terms, take a look at our dental glossary.
When you notice a problem with a root canal-treated tooth
When you notice pain when biting, a bump on the gum or swelling around a tooth that has had a root canal, you should not put off an examination even if the symptoms ease temporarily, because infection at the root tip can progress silently. At our polyclinic in Park Oran Ofis in Oran, Çankaya, your tooth is assessed clinically and radiographically, and we explain to you whether root canal retreatment or one of the alternative options is suitable.
Frequently asked questions
Can root canal treatment be done again?
Yes, in suitable cases root canal retreatment can be performed on a tooth that has had a root canal before. The old filling is removed, and the canals are cleaned and filled again. If the tooth has a root fracture or not enough tooth structure remains, retreatment may not be suitable.
How many visits does root canal retreatment take?
The number of visits depends on the state of the infection, the number of canals and how difficult it is to remove the old filling. Some cases are completed in a single visit, while in others medication is placed in the canals and a second visit is planned. The timeline is determined by the dentist after the examination.
My root canal-treated tooth does not hurt; might it still need treatment?
Some inflammation developing at the root tip can progress without symptoms and is noticed only on an X-ray. In this case, whether treatment is needed is assessed by comparing with previous X-rays and with the clinical findings. Some areas can simply be monitored.
