The canals were treated, but the tooth hurts again
This is one of the most common reasons people come to us for a second opinion. The tooth was treated five, ten, fifteen years ago, there is a crown on top — and suddenly it aches when biting and a bump appears on the gum. Most people assume it has to come out. Often it does not. A tooth with poorly treated canals can almost always be retreated; the real question is how much tooth is left.
Why a treated tooth starts hurting again
The goal of root canal treatment is simple: remove everything living and everything infected from the canals, then seal the empty space tightly so bacteria have nowhere to settle. If a gap is left anywhere along that chain, sooner or later it makes itself known.
The causes we see most often on scans:
The canal is not sealed to the tip. The filling material stopped a few millimetres short. Infected tissue stays in that last stretch and a lesion slowly grows around it in the bone.
Not every canal was found. Upper first molars very often have a fourth canal — narrow and hidden in the wall. Without a microscope it is easy to miss. Three canals are treated perfectly, the fourth was never opened.
The seal on top failed. The filling above the canals leaked, or the crown does not sit tightly, and saliva with bacteria seeps in. The canals themselves may be filled impeccably.
A cracked root. The worst scenario, and the only one where the tooth usually cannot be saved.
Often there is no pain at all. The lesion grows silently for years and turns up by accident — on a CT scan taken before implanting a neighbouring tooth.
What a CT scan shows that an X-ray does not
A periapical X-ray is the shadow of a three-dimensional tooth on a flat plane. Roots overlap each other and half the picture is lost.
A CT scan shows the tooth from every side in separate slices. It reveals what the decision actually depends on:
how many canals there really are and whether all of them were treated; how tightly the tip of each one is sealed; the true size of the lesion in the bone rather than its projection; whether a root wall is perforated; exactly where a broken instrument sits, if there is one; how close the root is to the maxillary sinus or the mandibular nerve.
Without a CT scan, retreatment is work done blind. We do not plan endodontic retreatment without one.
How retreatment works
It is longer and more delicate than first-time treatment. The tooth has already been opened once, there is less tissue inside and the risk of breaking through is higher. That is why all of it is done under a microscope.
Step one — take apart what is there. The crown or old filling comes off and the old material comes out of the canals. Gutta-percha is removed with solvent and instruments; glass ionomer and pastes are drilled out under optical control.
Step two — find what was missed. Under the microscope the floor of the pulp chamber is seen at twenty times magnification. The entrance to a hidden canal looks like a dark dot or a fine groove that the naked eye cannot distinguish.
Step three — shaping and disinfection. The canals are worked to full length under apex locator control, irrigated and left with a medicated paste. Between visits the tooth carries a temporary filling.
Step four — filling and follow-up. The canals are sealed tightly and a control image is taken. Then the tooth has to be rebuilt — after retreatment a back tooth almost always needs a crown.
When the canal cannot be reached: root microsurgery
Sometimes the tip cannot be reached from above. The canal is blocked by a post, the tooth carries a large bridge that is not worth dismantling, or the anatomy is such that no instrument will pass.
Then the work is done from the other side, through the gum. Root canal microsurgery: under a microscope a small access is made to the root tip, the lesion is removed, two to three millimetres of the tip are cut off and the cut surface is sealed with a special cement retrogradely.
It is a gentle procedure. The incision is small and the sutures come out after a week. The tooth stays where it is and keeps working under its own crown.
It is a separate line in the price list: root canal microsurgery — from UAH 16,500.
A broken instrument in the canal
Thin nickel-titanium files sometimes fracture. It is a known situation that happens even in experienced hands, particularly in narrow curved canals.
The fragment itself does not poison the body. The problem is different: it blocks the canal, and beyond it an untreated stretch is left where bacteria live.
What is done with it depends on where it sits. In the straight upper third it is usually visible under the microscope and retrieved with ultrasonics. Beyond a curve, retrieval is often impossible without risking a perforation — then the canal is cleaned down to the fragment and filled together with it, and if the lesion does not resolve, microsurgery follows.
Instrument retrieval — UAH 1,950–3,250 depending on difficulty.
Cost and number of visits
Retreatment usually takes two or three visits with two to four week intervals. The bone needs time to respond to the medicated paste inside.
Reference figures from the price list:
Preparation for endodontic treatment (dismantling the old work, removing the crown, unfilling the canals) — from UAH 2,200.
Periodontitis treatment in a single visit — from UAH 8,900.
Retrieval of a fractured instrument — UAH 1,950–3,250.
Root canal microsurgery — from UAH 16,500.
The exact figure is given after the CT scan, before any work starts. Sometimes the answer is unwelcome: a tooth with a cracked root, or with a couple of millimetres of tissue above the gum, is not worth retreating — the money goes into something that will split within a year anyway. In that case it is more honest to price an implant straight away.
Control images are taken at six months and at one year. The lesion shrinks gradually; bone does not rebuild in a week.
Frequently asked questions
Can a tooth be retreated without removing the crown?
Sometimes yes: an opening is made through the crown, the work is done through it and sealed with a filling at the end. That works when the crown is new and fits well. But visibility of the chamber floor is worse through an opening, so in a difficult case the crown is better removed.
How many times can the same tooth be retreated?
There is no formal limit, but there is a physical one: each attempt costs some root tissue. A second treatment is usually possible, a third rarely is. That is why it matters that the repeat attempt is done properly and under a microscope.
Why has the lesion not disappeared after six months?
Bone rebuilds slowly. Shrinkage at six months is already a good sign. Complete resolution sometimes takes one to two years. What is worrying is a lesion that has not changed or has grown.
The tooth does not hurt but the scan shows a lesion. Does it need treatment?
Yes. A chronic lesion lives painlessly for years and then flares up at the worst possible moment — on holiday, before a flight, during an illness. It also keeps destroying the bone around the root, and the larger it gets the worse the prognosis.
Can a tooth under a bridge be retreated?
Yes, but access will be through an opening in the bridge or through microsurgery. Dismantling a bridge for the sake of one tooth is usually not worth it if the other abutments are sound.
Is retreatment painful?
Under anaesthetic, no. The tooth has no nerve; sensitivity comes only from the ligament around the root. For two or three days afterwards biting may feel uncomfortable — that is a normal response to the work.
Which is cheaper: retreatment or an implant?
Retreatment is almost always cheaper, even with a new crown. But the comparison should be about prognosis, not price: if the tooth is held by two millimetres of tissue, the cheaper option turns out to be the most expensive one.
Are antibiotics needed?
Not always. They are prescribed for marked swelling, fever or spreading inflammation. Periodontitis itself is not cured with antibiotics — the infection lives inside the canal, where the bloodstream does not deliver the drug.
Chief doctor at Houston clinic. Restorative dentistry and endodontics under a microscope, treatment of canals, cysts and granulomas, cosmetic restoration.
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The doctor will look at the scan, say whether the tooth can be saved, and give a plan with exact figures before any work begins. A consultation with the head doctor costs UAH 1,500.
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Book a CT scan and find out the tooth's prognosis
The doctor will look at the scan, say whether the tooth can be saved, and give a plan with exact figures before any work begins. A consultation with the head doctor costs UAH 1,500.
Book now