It is not the intensity of the pain that settles it, but how long it lasts
- Whether pulpitis is reversible is decided neither by the intensity of the pain nor by its character, but by time: pain that disappears within a few seconds of the stimulus being removed means something different from pain that drags on for minutes. A proposed clinical classification puts the boundary at twenty seconds.
- That boundary determines whether the tooth ends up with a filling, or whether the pulp itself has to be reached.
- Spontaneous pain, arising without any stimulus, and pain that wakes you at night are the strongest signals of the irreversible form.
- A diagnosis of the irreversible form no longer automatically means root canal treatment: in the validation study, three patients out of sixty received it as first-line treatment.
- No chairside test measures the inflammation directly, so the diagnosis always remains an approximation based on symptoms.
Cold water hits the tooth, it hurts for two seconds, you put the glass down and the pain is gone. This has been happening for a few weeks. Then one evening the pain does not go away. It stays after the glass has been put down, drags on for a dozen or so minutes, and wakes you at night. Between those two evenings runs the boundary this article is about. It is set not by the intensity of the pain but by the number of seconds the pain lasts after the glass has been put down - and because of that, the same description means two different conditions in two different people. On one side pulpitis is reversible and the tooth ends up with a filling. Beyond it, treatment looks different.
The pulp is a tissue shut inside a box
The pulp is living tissue filling the inside of the tooth, with blood vessels, nerve fibres and cells that produce dentine.
Pulpitis is almost always caused by bacteria, which reach the pulp through a carious cavity, a crack in the enamel or the leaking margin of an old filling. The trouble lies in where this tissue sits. The pulp is enclosed within rigid walls of dentine and connects with the rest of the body through a narrow opening at the end of the root. When inflammation begins, the vessels widen and let fluid into the tissue. Anywhere else in the body swelling would form and that would be the end of it. Here the fluid has nowhere to escape. Pressure in the chamber rises and squeezes the very vessels that were meant to deliver the blood. The tissue loses its blood supply at the moment it needs it most. The longer this lasts, the less there is left to save.
This is how pulpitis becomes irreversible.
The pulp has one way of reporting trouble: pain. It does not distinguish touch, heat and pressure - it translates everything into the same signal, so a great deal has to be read out of the pain alone.
Reversible pulpitis: the pain ends together with the stimulus
The reversible form is a state in which, once the cause is removed, the tissue has a chance of returning to health: the tooth reacts to cold more strongly than its neighbours, but the reaction ends together with the stimulus, or shortly after it. The proposed clinical classification describes the mild form as a reaction lasting up to twenty seconds and then subsiding, and the moderate and severe forms as a reaction that drags on for minutes. This is not a measured threshold, nor a binding one, but a convention that puts the history-taking in order.
The second distinguishing feature: the pain appears only after something. After a cold drink, after something sweet, sometimes after drawing in air. Tooth pain on cold can be strong and unpleasant, yet it does not wake you at night and does not start of its own accord.
The third distinguishing feature can come as a surprise. In a validation study covering ninety-two adults with pulpitis, no patient in the two mildest categories reported spontaneous pain, and roughly one in six reported no pain at all. A tooth with reversible pulpitis can therefore not hurt at all and still require treatment. The study, however, covered only posterior teeth in adults, at a single centre, so the proportion cannot be transferred to the whole population.
The word "reversible" is often misunderstood. It does not mean "it will pass by itself". It means that the tissue still has enough health in reserve to heal, if the cause is removed. The cause is usually dentine caries, which will not reverse on its own.
Irreversible pulpitis: the pain starts to live a life of its own
Irreversible pulpitis is diagnosed when the tissue is damaged to the point at which removing the cause alone will not save it.
The symptoms do not merely intensify. They change in quality. The pain stops needing a stimulus. It appears on its own, can be throbbing, builds up when you lie down, and wakes you from sleep. In the same study, all thirty patients in the most severe category had spontaneous pain and all of them reported sleep disturbance because of it. Waking at night turned out to be one of the two most strongly discriminating features in the whole set of symptoms.
The reaction to cold changes too: it does not end together with the stimulus but drags on for minutes. The tooth begins to react to heat as well. Tenderness to percussion can be an additional signal, but it is not a condition of the diagnosis. In the same group it was found in slightly more than half of the patients.
There is one exception in this picture. In three patients from that group the reaction to cold appeared with a delay, but then dragged on for minutes. Once the tooth was opened, the pulp turned out to be already partly necrotic. A delayed but prolonged reaction therefore does not mean a milder condition; it can be a sign of a later one. Three cases are too few to settle anything. They are enough, however, not to treat a delayed reaction as a good sign and not to put off the appointment, waiting for it to pass by itself.
Urgency flags. Any one of these four symptoms brings the appointment forward to the next few days, because with each of them the window for keeping the pulp alive is closing:
- the pain appears on its own, without a stimulus;
- the pain wakes you at night, or builds up when you lie down;
- the reaction to cold appears with a delay, but drags on for minutes;
- severe pain has subsided by itself, because silence can be a sign that the pulp has died, not that it has healed.
In conversations with patients presenting at Modern Dental & Orthodontics (Klinika MDO), one question keeps coming back: why they cannot point to the tooth that hurts. The pulp has no sense of location comparable to that of the skin. The pain can therefore be diffuse and radiate along the arch.
Pulpitis symptoms: how the reversible form differs from the irreversible one
The table puts the history in order; it does not replace an examination.
| Feature | Reversible form | Irreversible form |
|---|---|---|
| What triggers the pain | Always a stimulus: cold, sweet, air | The pain also appears without a stimulus |
| How long the pain lasts after the stimulus is removed | Up to 20 seconds, then it subsides | Minutes, sometimes longer |
| Pain at night and when lying down | Does not occur | Typical, can be a reason for waking |
| Reaction to heat | Usually normal | Often distinctly painful |
| Tenderness to percussion | Rarely | In some patients, not in all |
| Depth of the cavity on the radiograph | Deep caries | Caries reaching the pulp |
| What is usually enough | Remove the caries and restore the tooth with a tight seal | The pulp itself has to be reached |
What is striking is what this table does not contain. When the data of those same ninety-two patients were analysed, it turned out that the type of pain and its intensity did not tell one form from the other. Sharp or dull, a seven or a nine on a scale of ten, and throbbing too was distributed similarly on both sides of the boundary; what distinguished the forms was mainly four other features: how long the reaction to cold lasts, whether the pain appears on its own, whether it wakes you at night, and how deep the caries is. The patient describes how much it hurts; the dentist has to know when the pain starts and when it ends.
What the research says, and what can be seen in the surgery
| What the research says | What can be done in the surgery |
|---|---|
| The reference standard for diagnosis is microscopic examination of a specimen of the pulp | A specimen cannot be taken from a tooth that is meant to be kept |
| The systematic review prepared for the European guideline states it plainly: a reliable reference standard under clinical conditions is lacking, and the effectiveness of diagnosis is low | The diagnosis is made from the history, the cold test, percussion and the radiograph |
| Attempts were made to replace the two-tier division with a more detailed one, with four categories | When the same patients were assessed by seven clinicians, they assigned them more consistently to the old division than to the new one, and the data indicated that there are really three categories |
| Concentrations of inflammatory proteins in pulp blood differ between the forms of pulpitis | There is no chairside test that measures them; this is a direction of research |
The conclusion is uncomfortable: the diagnosis rests on what the patient describes and on how the tooth responds to two simple tests. Not on a measurement.
How the dentist checks the state of the pulp
One distinction explains why pulpitis is so hard to diagnose. A vitality test would check the blood supply to the pulp, that is, whether the tissue is alive; a sensibility test checks the response of the nerve fibres. In the surgery it is the second that is done routinely, and the first is inferred from it. It is performed with a cotton pellet soaked in a cooling agent and applied to the neck of the tooth, and can be supplemented with an electric test that stimulates the same fibres with a current. Suspected pulpitis of the tooth is therefore confirmed indirectly, through the response of the nerve, and what counts is not the fact of a response but how long it lasts after the cotton has been taken away, and whether it differs from the neighbouring tooth and from the same tooth on the opposite side.
Percussion says something else as well: it speaks about the tissues around the end of the root. A painful response can be a signal that the inflammation has reached beyond the tooth, but it also accompanies pulpitis itself. The radiograph does not show the state of the pulp. It shows how deep the caries reaches and whether a lesion is visible at the apex of the root. In the validation study, the depth of the cavity was among the features that discriminated between the categories. The last word belongs to what is seen once the tooth has been opened: the appearance of the pulp and the time it takes for bleeding from the exposed tissue to stop. The treatment plan sometimes changes during the procedure, and this is not a sign of a diagnostic error but a limit of the method.
Treatment of pulpitis: what follows from this for the tooth
When pulpitis is reversible, the aim is to remove the caries and to restore the tooth with a tight seal; how the cavity is prepared also counts, although that is the dentist's choice. In a randomised trial, on one hundred and twenty-four permanent teeth, total removal of the lesion with immediate management of the exposed pulp gave pulp survival at one year in more than ninety-eight cases in a hundred, and selective removal in slightly fewer than eighty-three. The pulp was exposed in more than one quarter of the teeth prepared by total removal: exposure alone therefore does not decide failure, if it is managed straight away. The European guideline nevertheless recommends selective removal here, so as not to expose the pulp. This is a contested point - and it will not be settled by the patient, but by the dentist at the chair. One figure from that trial concerns the patient directly: the prognosis was worse for teeth that before treatment hurt more than halfway up the scale. The intensity of the pain does not tell you which form of pulpitis you have, but it does say something about the chances of saving the pulp.
Between a filling and root canal treatment runs an intermediate path: pulp capping and pulpotomy, that is, removal of the part of the pulp that is beyond saving. They come into play when the pulp has been exposed during removal of the caries and the bleeding can be brought under control. That is the only signal available to the dentist at the chair: the review prepared for the European guideline found no feature that would allow the outcome of such treatment to be predicted before the procedure. When the bleeding cannot be brought under control, or the pulp turns out to be partly necrotic, the dentist changes the plan to root canal treatment within the same appointment. An unsuccessful attempt closes nothing off. A separate article on these procedures is in preparation.
When pulpitis is irreversible, for decades there was one answer: endodontic treatment, that is root canal treatment, described step by step in the article on what root canal treatment involves. That answer has stopped being the only one. In a randomised trial of sixty mature molars with irreversible pulpitis, removal of the coronal part of the pulp alone and root canal treatment gave a comparable result at one year, close to ninety-three cases in a hundred. A systematic review of two other studies, one hundred and fifty-six teeth in total, gave at one year ninety successes in a hundred for removal of the whole coronal pulp and eighty-three for removal of part of it, with no clear difference between the methods.
The scale of the change shows in a single figure: in the validation study, sixty patients had a diagnosis of the irreversible form and in the past all of them would have gone to root canal treatment. Under the new approach, three out of sixty received it as first-line treatment, and across the whole study the pulp was kept alive at one year in eighty-seven per cent of those who attended for follow-up. You may ask about such treatment, but you cannot demand it: what qualifies a tooth for it is the picture only after the tooth has been opened. These are one-year results, from a single centre, so they are not conclusive.
What you cannot assess at home
The fact that the pain has stopped does not mean that the tooth has recovered - the pulp may have died, and then the pain can come back from the direction of the bone.
Until the appointment, warming the cheek, a painkiller tablet held against the gum and an antibiotic from the home medicine cabinet all do harm. The state of the pulp cannot be diagnosed without an examination. Pain that appears on its own, or wakes you at night, is an indication for an appointment, not for waiting. If facial swelling or fever is added, the matter stops being one of the pulp alone and calls for help the same day. We write about it in the article on tooth abscess.
Frequently asked questions
Does pain on cold always mean root canal treatment?
No. Pain on cold on its own is a non-specific symptom and accompanies tooth sensitivity and leaking fillings as well. Time is what settles it: a reaction ending together with the stimulus argues for the reversible form, which is treated with a filling. A reaction dragging on for minutes calls for management that reaches the pulp itself.
Does irreversible pulpitis always end in root canal treatment?
Not any longer. Some such teeth are today treated by removing part of the pulp, keeping the tissue in the root alive. In the validation study, out of sixty patients with this diagnosis, three received root canal treatment as first-line treatment. Not every tooth is suitable for this, and the results come from a single centre and cover one year of follow-up.
Can pulpitis pass by itself?
The symptoms can subside; the disease itself does not. The pain going away means either that the inflammation has quietened down while the cause is still present, or that the pulp has died, which is a more serious state than the initial one. As long as bacteria have a route into the inside of the tooth, pulpitis carries on, only silently and without warning.
Why does the pain get worse at night?
Lying down increases the flow of blood to the head, so pressure in the closed chamber of the tooth rises. The absence of distracting stimuli also counts. In research on the diagnosis of pulpitis, sleep disturbance turned out to be one of the features that most strongly distinguish the irreversible form from the reversible one.
Will the anaesthetic work, and can I take something before the appointment?
A painkiller suppresses spontaneous pain, one of the features by which the dentist tells the irreversible form apart, so say what you took and at what time. A tablet does not remove the reaction to cold. In a randomised trial, an anti-inflammatory drug given an hour beforehand clearly increased the effectiveness of anaesthesia of the lower molars, although even so it was not sufficient in most cases.
How much time do I have to react once the symptoms appear?
It depends on what kind of pain you have. Spontaneous pain, or pain that wakes you at night, means an appointment within the next few days, because every day of delay reduces the chance of keeping the pulp alive. Pain only after something cold, ending together with the stimulus, gives more time, but the cause is usually caries, which will not reverse on its own. Nobody will set a fixed deadline, because the pace of change varies.
Can a tooth that does not hurt have a dead pulp?
Yes. The pulp can die painlessly, and the first signal is sometimes only a lesion at the apex of the root, visible on a radiograph taken for another reason. Reversible pulpitis can be painless as well: in a validation study covering ninety-two patients, roughly one in six with the mild form reported no complaints.
The boundary has moved, but it has not disappeared
The division into reversible and irreversible pulpitis came about in order to answer one question: does the tissue still have health in reserve. The answer still decides the fate of the tooth; what has changed is what follows from it. A diagnosis of the irreversible form is no longer a sentence condemning the tooth to removal of the whole pulp.
The practical conclusion can be remembered without the table.
Do not count how badly it hurts. Count how many seconds the pain lasts after the glass has been put down: under twenty is one size of problem, over a minute another. Tell the dentist that number - together with whether the pain wakes you at night.
Read more:
- Root canal treatment in Warsaw
- Root canal treatment step by step — how long it takes and what to expect
- Tooth decay stages: when can it be stopped without drilling
- Tooth abscess — does a tooth with an abscess always have to be removed?
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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