A root-filled tooth that starts aching again, sometimes years after treatment, has not necessarily reached the end of the road. In many cases the tooth can be reopened, cleaned again and resealed. A systematic review of this procedure (Ng and colleagues, International Endodontic Journal, 2008) found that about three in four retreated teeth healed completely, which is why retreatment is usually considered before removing the tooth.
How a treated tooth becomes infected again
The inside of a tooth is not a single tube. Canals can be narrow, curved and branched, and some teeth have an extra canal that is hard to find. If bacteria are left in part of that system, or get back in later, infection can persist or return around the root tip.
The usual routes back in are a canal that was missed or could not be fully cleaned, a filling or crown that has leaked or broken down, new decay reaching the root filling, or a crack in the tooth. A back tooth that went too long without a crown after its first treatment is also more likely to crack or leak. Because most of these problems sit inside the tooth, they are often within reach of a second, careful cleaning.
It does not always hurt
Some teeth that need retreatment throb or ache. Others are tender when you bite, or a small pimple appears on the gum and drains from time to time. A fair number cause no symptoms at all and are first noticed as a dark area around the root on an X-ray at a routine check-up.
If a previously treated tooth becomes sore again, it is worth having it checked rather than waiting to see whether it settles. Our articles on pulpitis and what to do about an abscessed tooth describe the kinds of pain and infection that can develop.
What retreatment involves
Non-surgical retreatment is done under local anaesthetic, much like the first root canal. The dentist removes the crown or filling where needed to reach the canals, takes out the old root filling material, searches for any canals that were missed, then cleans, disinfects and reseals the canal system. The tooth then needs a sound final restoration, usually a crown on a back tooth, to keep bacteria out.
Retreatment is often more involved than the first treatment. Old filling materials, posts or blocked canals can take time to remove, and complex cases are often referred to a registered specialist endodontist.
When surgery at the root tip is considered
If retreatment is not possible, for example because a post cannot be removed safely, or if retreatment has not resolved the problem, a small operation called an apicoectomy may be an option. The root tip is reached through the gum, the infected tissue and the end of the root are removed, and the root end is sealed. With modern microsurgical techniques, a 2010 meta-analysis (Setzer and colleagues, Journal of Endodontics) reported a pooled success rate of about 94 per cent, compared with 59 per cent for older techniques. Our guide to apicoectomy explains the procedure in more detail.
A 2009 systematic review (Torabinejad and colleagues, Journal of Endodontics) compared the two approaches. Surgery had slightly higher success at two to four years, but retreatment had higher success at four to six years, and the success of surgery tended to fall with longer follow-up. The right choice depends on the tooth, the cause of failure and what can be reached.
Comparing the options
| Option | Often suits | Keeps your tooth? |
|---|---|---|
| Non-surgical retreatment | Problems inside the canals, such as a missed canal or leakage | Yes |
| Apicoectomy | Teeth where retreatment is not possible or has not worked | Yes |
| Extraction and replacement | Teeth that are cracked, split or too broken down to restore | No |
When a tooth cannot be saved, it can be replaced with an implant, a bridge or a denture. Our comparison of implants, bridges and dentures covers those choices, and our guide to root canal versus extraction looks at the decision more broadly.
Questions we are often asked
Is retreatment more painful than the first root canal?
It is done with local anaesthetic and usually feels similar. Some tenderness for a few days afterwards is common and is usually managed with simple pain relief.
Is retreatment less likely to work than a first root canal?
Not necessarily. A large prospective study (Ng and colleagues, International Endodontic Journal, 2011) found similar rates of complete healing after a first root canal and after retreatment, about 83 and 80 per cent of roots. Success depends a great deal on why the first treatment failed, whether there is infection around the root and how much healthy tooth remains, and old materials can make parts of the canal harder to reach.
How long will a retreated tooth last?
Many retreated teeth last for years when they are properly sealed, protected with a suitable restoration and looked after with good home care and regular check-ups. No dentist can promise a specific lifespan.
Should I just have the tooth taken out?
Sometimes that is the better choice, particularly if the tooth is cracked or has little structure left. When the tooth is restorable, keeping it is often worth considering, because replacements involve their own cost and upkeep.
If a previously treated tooth is bothering you, the team at Lumi Dental can examine it, take X-rays and talk through the options, including referral where that is the better path. Current offers are on our current deals page.
This article is general information and not a substitute for personalised advice from your dentist.
