It does not hurt and is still treated - provided the tests confirm it
- A painless lesion at the root tip does not yet say what to do: the tooth’s history and the result of the pulp vitality test decide together. The history alone is not enough.
- The absence of pain rules nothing out. A chronic infection at the root can stay silent for years.
- The radiograph shows a loss of bone. It does not say whether the pulp is alive or whether the lesion is growing; that is settled only by a pulp test and a second radiograph a few months later.
- A tooth that responds normally to cold is usually not a candidate for having its canals opened, however large the radiolucency. This is not something you can check yourself.
- This article deals with a lesion found by chance, at a tooth that does not hurt. A tooth that already hurts, or one where swelling has appeared, is a different situation and a different level of urgency.
What a painless lesion at the root tip says about the tooth, and what it does not
The radiograph records an effect, but says neither what caused it nor when.
A single frame does not distinguish a lesion that is healing from one that is slowly growing, because both look the same: like a loss of bone. They are told apart only by a second frame, taken a few months later. The darker patch at the root tip is a place where bone has been lost, dissolved by the body in order to wall itself off from what is escaping from inside the tooth. A radiologist will call it a periapical lesion (a loss of bone at the tip of the root), the note in your records may read “radiolucency at the root”, and neither of those names is yet a diagnosis.
Silence is the rule here. Inflammation of the tissues at the root tip usually runs a chronic and symptom-free course, and worldwide one adult in two has at least one tooth with such a focus; in the general population the figure is closer to four in ten. A finding of this kind is therefore usually old, and that changes the pace at which it has to be answered.
What to bring to the appointment so that a decision can be made there
Bring the image file and the date it was taken, because without a date there is nothing to compare with what. These are worth asking about on the spot:
- Which tooth exactly has the lesion, and has it ever had root canal treatment?
- How did this tooth respond to the cold test, and how did the neighbouring tooth respond?
- Is there anything to compare with, that is, is there an older radiograph of this site in my records?
- Is this already a diagnosis, or an image to be monitored, and when do we check again?
Three situations in which you do not wait for a follow-up
They override any plan to monitor and mean an appointment the same day:
- swelling of the cheek, the gum or the floor of the mouth;
- fever, general malaise, enlarged lymph nodes;
- pain building from hour to hour, difficulty swallowing or opening the mouth.
Four situations and four different decisions
The tooth’s history and the result of the pulp vitality test divide an incidental finding into four baskets.
| Tooth history and test result | What that usually means | Next Step |
|---|---|---|
| Previously untreated tooth, normal response to cold | The pulp is alive, so this tooth is probably not the source of the lesion | The canals are not opened. We check the neighbouring tooth, anatomical structures and images projected from the surrounding area |
| Previously untreated tooth, no response to cold or to electric testing | The pulp has died, and infection of the canal continues despite the silence | Root canal treatment, usually planned |
| Tooth after root canal treatment, no symptoms | Persistent or secondary infection, less often a bone scar, which looks similar on the radiograph | We check whether the canals are well filled and whether the restoration is sealed |
| The tests contradict one another or the image is atypical | There is no diagnosis yet | We add to the examination or monitor over time, without opening the tooth |
A normal response to cold argues against a diagnosis of a dead pulp, and in a tooth that does not hurt, the lesion on the radiograph alone is not an indication for root canal treatment, however alarming the image may look. Opening such a tooth treats nothing, and takes its living pulp away irreversibly.
This rule has a limit. In a multi-rooted tooth the response may come from a root whose pulp is alive, while in the other root the pulp is dead and it is that root which keeps the focus going. In molars the diagnosis rests on the whole picture; the test alone does not settle it.
A never-treated tooth that responds to no test has usually died without anyone noticing. The pulp can die after an old injury, after a deep filling placed years ago, or after slow decay that never gave sharp pain. A darker crown is sometimes the only trace visible to the naked eye, though often there is not even that.
Teeth after root canal treatment in which a lesion is still visible have a prognosis of their own. Such teeth more often still had a focus years later and more often ended in extraction than root-filled teeth with no focus at the outset; this was counted in two Danish cohorts followed for ten years. That observational study, however, gives the direction alone, without a number for a single tooth. A lesion at a treated tooth is a signal to check, not to postpone.
The fourth basket is the hardest to accept. Contradictory tests do not mean the dentist has made a mistake, only that there is no diagnosis yet, and forcing one ends with the wrong tooth being opened.
Which examinations settle what the radiograph does not show?
Usually three: the cold test, the electric test and a comparison of two radiographs over time. The cold test checks whether the nerve in the tooth still answers, and the electric test stimulates the same fibre by another route. Neither of them measures the blood supply. Both therefore speak of sensation, and of the life of the pulp only indirectly. The dentist always tests several teeth, not one: the neighbouring tooth and the tooth on the opposite side of the arch serve as the reference.
The cold test also has a weaker point. On teeth covered by a crown it was correct in 86.6% of cases against 91.5% on teeth without a crown, the reference being direct assessment of the pulp after the tooth was opened. A more troubling number comes from the same paper: when living tissue was left only in the canals, the test was correct in roughly half of the cases, though in each group this concerned about thirty teeth.
A deeper problem was described by a systematic review prepared for the European endodontic society: pulp diagnosis lacks a reliable reference standard. There is no examination against which a test result can be compared and called “the truth”. A diagnosis is therefore built from a bundle of premises - the history, two tests, the responses of the comparison teeth and the image - not from a single measurement.
Cone beam tomography shows more. That does not mean it shows better. In one study the readers performed better on the plain radiograph than on the tomogram for subtle and moderate lesions, and both kinds of image were assessed by the same readers; for subtle lesions the tomogram additionally produced more false marks, that is, areas described as diseased without disease. We write more broadly about choosing the right examination in our guide to dental radiology.
When is monitoring reasonable, and what does the follow-up look like?
Usually when there is no diagnosis yet, and the tooth is symptom-free and responds to cold normally. An active infection at a dead tooth may enlarge the focus over time, while an anatomical or incidental image stays the same for years. The question the second radiograph asks is therefore not “is the patch still there” but “has it grown”.
A follow-up makes sense only when it can be compared: the radiograph has to be taken with the same alignment as the previous one, and both frames are assessed side by side, which cannot be done from memory. The first comparison usually after six months, the next after a year.
A painless lesion at the root tip that has neither grown nor shrunk does not settle the question of active infection, and where the pulp is dead it is not a reason to go on waiting. A smaller lesion confirms healing. A larger lesion ends the monitoring and moves the decision to treatment, including when the tooth still does not hurt.
The whole plan rests on the patient coming back, and a symptom-free tooth does not remind anyone of itself; it is the one that returns for follow-up least often. Monitoring without a second radiograph is not a decision, only the name of one.
The measure itself can be unreliable. At least a year after treatment the outcome was judged successful in close to eight teeth in ten on periapical radiographs and in just under seven in ten on tomograms. These were the same teeth, assessed by both methods at once, so the difference did not come from the patient’s mouth - it came from the instrument.
What is missing, moreover, is a study that would compare deliberate monitoring of a symptom-free lesion with treating it. There is therefore no number to give a patient who asks how much they risk by waiting a year. The decision to wait rests on the diagnosis and on clinical judgement; there is no comparative evidence beneath it.
When does a tooth need root canal treatment or retreatment?
When the pulp is dead there is one direction: root canal treatment removes the infected contents of the canal and takes the lesion’s fuel away, and the bone then rebuilds itself, so the image changes over months, not weeks. An antibiotic does not replace this: it does not reach the inside of the canal where the source sits. Its place is where there is swelling and fever, that is, where the infection is beginning to spread, not at a symptom-free finding.
The size of the lesion does not settle the question of surgery. Large foci measuring more than ten millimetres at upper front teeth, all of them following old injuries, managed by root canal treatment alone, shrank or disappeared in about eight patients in ten over two years of observation. Note the word “or”: complete disappearance happened rarely, in fewer than one patient in ten. Anyone expecting a radiograph without a trace after two years will probably read successful treatment as failed. Diagnosing a dental cyst is a separate matter and we write about it elsewhere.
In a tooth with filled canals and a persisting lesion the question returns: repeat the root canal treatment or reach for a procedure from the bone side. A systematic review pointed to no winner here, and the authors rated the quality of the included studies as low. We describe the choice between the two in our article on root canal retreatment. In everyday clinical practice at Modern Dental & Orthodontics (Klinika MDO) we encounter the situation in which the choice is decided by access to the canals and the state of the restoration, not by the size of the focus alone.
A lesion that does not resolve despite correctly performed treatment calls for a diagnosis, not a third attempt. Malignant lesions have been described that looked like an ordinary focus at the root and usually had no alarming features on the image. They are rare, but the cost of missing one is time.
Consult your case with an expert and get your treatment plan
Frequently asked questions
Does a lesion at the root always come from the tooth?
No. Some radiolucencies in this area are anatomical structures, bone lesions or images projected from the surrounding area. Rare malignant lesions mimicking an inflammatory focus at the root have also been described, most often in the posterior mandible and usually without warning features on the radiograph. The diagnosis therefore rests on the tests. The appearance of the patch alone will not replace them.
Does a symptom-free focus harm the whole body?
There is no evidence that it causes systemic disease. Observational studies link chronic inflammatory foci with systemic diseases, but they do not separate cause from effect. It is not a matter of indifference, though: before treatment that lowers immunity, before a planned cardiac procedure and before an implant is placed in that area, the focus has to be reported to the doctor and usually dealt with beforehand.
Can such a lesion disappear on its own?
A focus arising from infection of the canal will not resolve by itself, because the source stays in the tooth. It recedes only once the infection has been removed. An image that merely resembled an inflammatory lesion, on the other hand, may be unchanged on the next radiograph or may disappear along with another cause - for example once the socket has healed after an extraction next door.
Is tomography always needed?
No. It is not a screening examination. When the periapical radiograph is legible it usually changes nothing in the decision. It is reached for when a specific question has to be answered: how many roots the tooth has, whether the lesion involves the sinus, whether the root is cracked. The question first, the examination second.
Can a tooth without symptoms suddenly start to hurt?
It can. A chronic focus may stay silent for years and flares up when the balance between the infection and the immune response shifts, for example during an illness or after the tooth has been heavily overloaded. Pain on biting, swelling or the feeling of a “taller” tooth then appears. That is already an indication for an urgent appointment.
What does a patient feel in the first days after treatment of a symptom-free tooth has begun?
A tooth that was silent before usually becomes noticeable. Tenderness on biting for a few days, sometimes a week, is typical, resolving on its own or after an ordinary painkiller. The treatment itself is usually planned over one or two appointments. Increasing pain, swelling or fever do not fit the normal course and call for contact with the practice.
How long after treatment does the radiograph show that the lesion is healing?
The first follow-up after treatment is usually done after six months, the next after a year, and a sound assessment of the bone only after two years. Healing shows as a gradual shrinking of the radiolucency and a thickening of the bone trabeculae, less often as a return to a completely clear image. No shrinkage after two years is an indication to re-examine.
A painless lesion at the root tip describes the tooth’s past, and its size does not set the prognosis
The patch at the root is a record of what has already happened. What comes next is decided by the state of the pulp and the treatment history; the diameter of the shadow on the radiograph says little about it. Two mistakes cost the most and they are exactly opposite: opening the canals in a tooth that is alive, and monitoring a focus for years at a tooth that has died. Both come from reading the image alone - in isolation from the test.
Read more:
- Root canal treatment in Warsaw
- Root canal retreatment after failed treatment — when it makes sense and when it does not
- Dental cyst - what it is and why it should not be ignored
- Dental radiographs, panoramic imaging, 3D tomography: A guide to dental radiology
- Root canal treatment step by step: How long does it take, what does it look like and what to expect?
Content and liability disclaimer
This article is informational and educational in nature and does not constitute medical advice, a diagnosis or a therapeutic recommendation — it does not replace a consultation with a specialist. If you are experiencing symptoms, have doubts or are facing a decision about treatment, consult a dentist. The methods described and the data cited are general in nature. The results of scientific studies relate to populations, not to an individual patient. The course and outcome of therapy depend on the individual clinical situation and may vary between patients. No information contained in this article constitutes a guarantee of result. The content has been prepared with due care, based on publicly available medical knowledge and the scientific publications indicated in the Sources section. We do not advise taking or refraining from any health-related action solely on the basis of the content of this article, without prior consultation with a doctor.
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