[Last updated: 26 August 2026]
Key takeaways:
A previously treated tooth can become reinfected due to leakage, missed canals, new decay or cracks
Root canal retreatment involves removing the old filling, finding and disinfecting the canals, then resealing the tooth
The article covers symptoms, retreatment and endodontic surgery, costs, MediSave coverage and what to expect from treatment
What is root canal retreatment? Retreatment removes the old root filling, cleans the canal system and reseals the tooth. It is one of the most common reasons dentists refer to an endodontist.
A tooth treated years ago can become reinfected, usually because bacteria have found a way back in through a leaking filling, a missed canal, new decay or a crack.
A root canal does not fail because the tooth wore out. It fails when bacteria get back inside. The usual routes includes: a filling that has started to leak, a canal the original treatment could not reach, decay creeping under the edge of a restoration, or a crack opening a new path.
A leaking restoration. The root filling depends on the seal above it. Once the filling covering the tooth wears, chips or loses its edge, saliva and bacteria seep down towards the root filling. The root canal below may have been done well; the seal above simply gave way.
A missed canal. Back teeth commonly hold three or four canals, sometimes more, and the extra ones are fine enough to be missed without magnification. An untreated canal keeps its infected tissue, and the tooth stays quietly inflamed until the day it is no longer quiet.
New decay. A treated tooth can still decay like any other, and because the nerve is gone, it decays without the warning of sensitivity. By the time it is visible, decay can have reached the canal system.
A crack. Root canal-treated teeth are more brittle than living ones. A crack from a hard bite or years of grinding lets bacteria straight into spaces that no filling seals.
Timing is a clue: a tooth comfortable for ten years that then flares usually means something new, such as leakage, decay or a crack, rather than a treatment that never worked.
The common signs are a tooth tender to bite on, a dull ache that comes and goes, a small spot on the gum that swells, drains and returns, or swelling in the gum or face. Some returning infections cause no symptoms at all and appear as a dark shadow on a routine X-ray.
Image: Sinus tract due to a root canal infection
The gum spot deserves particular respect. It is a sinus tract, a small drainage channel the infection makes for itself, and because it relieves pressure, the ache often settles when it appears. That is the infection finding an exit, not resolving.
Tenderness on biting points to inflammation around the root tip rather than inside the tooth: the nerve was removed at the first treatment, so a root-treated tooth that hurts is hurting from the tissues around it. On an X-ray, longstanding infection shows as a dark halo at the root tip, which is why some failures are found at a routine check-up before any symptom at all.
If you are unsure whether what you feel fits this pattern, the 60-second symptom check walks through the signs that matter, including the ones specific to previously treated teeth.
Retreatment is the original root canal done again, with one extra stage: everything from the first treatment has to come out before the cleaning can begin. The tooth is reopened, the old root filling is removed, the canal system is disinfected, including whatever was missed, and the tooth is sealed again.
Dental x-rays establish which tooth is the problem and what the first treatment left behind: the shape of the old filling, any untreated canal, the shadow at the root tip. It is also where the options, retreatment, surgery or extraction, are weighed honestly through a meaningful discussion with the specialist.
What matters most is to choose an option that you are comfortable with and will last in the long run!
If root canal retreatment is the chosen treatment, it will be performed under local anaesthesia. The endodontist works through the existing restoration to reach the root filling beneath.
The material that was previously used has hardened up along the root canal system. Careful inspection will be done under the microscope at 20x magnification to identify the type of material used. This will allow accurate techniques and right equipment to be employed to remove the material in the most minimally invasive manner.
Image: Removal of defective crown and endodontic retreatment was performed. Infected old root canal material was removed
Under the operating microscope, the canal system is inspected for untreated canals, blockages and cracks. In certain cases, broken instruments may be found in the root canal systems. These could have obstructed the disinfection of the canals. This will be managed tactfully in order to aid a better disinfection during the retreatment. This is the heart of retreatment, and Dr Elyssa Yap's daily work.
Flexible nickel-titanium instruments reshape the canals, and in selected cases, laser-activated irrigation drives the disinfecting solution into fine branches that instruments cannot reach. The tooth will be dressed in medication to allow continued disinfection in between the appointments.
Image: The root canals were disinfected and re-sealed
On the final visit, the canals are filled and sealed. You will be referred to your own general dentist to complete the crown and continue your regular care.
Sometimes the canals cannot safely be re-entered from above, because a post is cemented inside one or reopening would destroy sound work, and sometimes infection persists at the root tip despite a well-filled canal.
In these cases, an apicoectomy may be considered. This is a minor surgical procedure where the dentist accesses the infected area through the gum at the tip of the root, removes the affected tissue and seals the root tip. It is a minor procedure under local anaesthesia, and whether it suits your tooth is an assessment finding, not a preference.
Regular root canal treatment and retreatment are not MediSave-claimable. However, certain endodontic surgeries, including an apicoectomy, may be MediSave-claimable under specific procedure codes, subject to the applicable claim limits.
For example, endodontic surgery is claimable up to $1,620 in total for a single-rooted tooth (under procedure code SF708T), and up to $1,890 for a multi-rooted tooth or more than one tooth (under procedure code SF818T).
*The figures were accurate at the time this article was last updated. For the latest claim limits and current treatment fees, please check directly with the clinic.
These amounts combine the procedure limit with the applicable day-surgery fee. GST is not included in the claimable amount and cannot be claimed through MediSave.
Eligible patients aged 60 and above may also use up to $400 per year through Flexi-MediSave for outpatient root canal treatment. How claims work, along with CHAS and insurance, is on our payments and insurance page.
At Sage Dental Specialists, root canal retreatment starts from $1,417 per tooth. Every quotation is itemised at consultation before treatment begins.
Removing old root canal fillings is often the most time-consuming part of retreatment. Your specialist needs to carefully remove the old filling material without damaging the tooth, work through blocked canals, and look for canals or areas that may have been missed during the first treatment. This is why retreatment can take more time, especially when a dental microscope is needed.
If surgery is recommended instead, the cost will be discussed and quoted during your consultation, based on the specific procedure needed. All fees are listed in Singapore dollars and include 9% GST; the full fee table is published on the fees section of the treatment page.
*The prices shown in this article are for reference only. For current pricings, please contact Sage Dental Specialists directly. Your final quotation will depend on your individual treatment needs and will be provided at your consultation.
Anything from the original treatment shortens the visit: a referral letter if you have one, previous X-rays, roughly when the tooth was treated, and what has happened to it since, including repairs, earlier flare-ups, and how long the gum spot has been coming and going. Records sent ahead by WhatsApp let a quotation be prepared before you arrive.
None of it is compulsory, and X-rays can be taken on the day. If your dentist is referring you, everything they need is on the for referring dentists page, and after treatment they receive a full report, so your ongoing care stays where it was.
Yes. Retreatment is within the scope of general dental practice, and some general dentists take it on, particularly in straightforward teeth. In practice it is one of the procedures dentists refer most often, because removing old filling material and finding missed canals is slow, technical work that benefits from an operating microscope and specialist repetition. A dentist who refers a retreatment is making a considered judgement about where the tooth is better treated.
There is no honest number. It depends on how much sound tooth structure remains, the quality of the final restoration sealing the tooth, and the forces the tooth takes in your bite. The factors deciding it are weighed before retreatment is recommended, so a tooth unlikely to be worth re-treating is identified at assessment, and review X-rays afterwards show whether the bone around the root tip is healing.
Neither answer is right by default. Keeping a natural tooth generally serves you well when enough sound structure remains to rebuild it; extraction followed by an implant or bridge can be the more sensible path when it does not. The deciding factors are restorability and what the X-rays show, which is why an assessment is important.
The procedure itself is carried out under local anaesthesia, the same as a first root canal, and removing an old filling is not inherently more uncomfortable than the original cleaning. Tenderness for a few days afterwards is common, and more likely if the tooth was acutely inflamed beforehand. Over-the-counter painkillers are usually enough while it settles. Pain that worsens rather than settles is worth a call to the clinic.
Reviewed by Dr Elyssa Yap, BDS, MDS (Endodontics), Registered Specialist in Endodontics, Singapore Dental Council.
To make an appointment at Sage Dental Specialists, call or WhatsApp +65 9736 5989.
Address: 435 Orchard Road, #12-04 Wisma Atria Office Tower, Singapore 238877