What does a throbbing toothache mean?

The pulp at the centre of the tooth is nerve and blood vessel tissue living in a chamber surrounded by hard walls. MSD Manuals writes that inflammation of the pulp (pulpitis) is most often caused by decay and next most often by a blow; that mild inflammation may cause no lasting harm to the pulp if its cause is removed, whereas severe inflammation can lead to the death of the pulp. Dentistry gives these two stages two separate names: reversible pulpitis (the nerve can be saved) and irreversible pulpitis (the nerve cannot be saved). The real question with a throbbing toothache is which side of this line the tooth is on.

MSD describes this line through a simple test the dentist carries out: a cold or sweet stimulus is applied to the tooth (pain brought on by heat that lingers fits the irreversible picture more). If the pain passes within 1 to 2 seconds of the stimulus being removed, the pulp may be healthy enough to be saved. If the pain carries on after the stimulus has gone, or comes on by itself with no stimulus at all, the pulp may be beyond saving. Pain that throbs, wakes you at night and comes back when a painkiller wears off usually fits this second picture.

This description also gives you a rough clue at home. On the painful side, take a sip of cold water, hold it for a few seconds, spit it out and start counting. If the twinge dies down as soon as you spit the water out, within a second or two, the nerve may still be at a stage where it can recover. If the pain carries on for minutes after you spit out the water, or even builds up, that fits the description of lingering pain. This test does not make a diagnosis, and it does not tell you which tooth is hurting either. But it gives you the most valuable piece of information to describe to the dentist. If there is also a tooth whose pain is soothed by cold water and flares up with a hot drink, be sure to mention it.

How reliable is the classification dentists base on these symptoms? In a study at a general practice over 5 years, in which 95 teeth extracted for other reasons were first classified by their clinical symptoms and then examined under a microscope, a diagnosis of a healthy pulp or reversible pulpitis was confirmed by microscopy in 57 of 59 teeth (96.6%), and a diagnosis of irreversible pulpitis in 27 of 32 teeth (84.4%). In teeth with irreversible pulpitis, infection that had advanced into the pulp tissue was common; in healthy or reversible teeth it was never seen. So the description of the symptoms usually points the right way; where it goes wrong most is the diagnosis of irreversible pulpitis: in 5 of 32 teeth, roughly one in six, the microscope did not confirm it.

The second meaning of throbbing is that the inflammation has overflowed from inside the tooth and reached the root tip. MSD writes that when an abscess develops, the tooth becomes extremely sensitive to pressure and to being tapped with a dental instrument, and that pain on tapping usually shows the inflammation has spread to the surrounding tissues. In practice, this means the pain now comes not only with cold or heat, but also when you close your teeth together and chew on that side. Because the pulp has often died by this stage, the tooth may no longer respond to cold; the pain comes not from the nerve but from the pressure at the root tip.

What makes a throbbing toothache most misleading is that it hides where its source is. In a study in Tehran of 100 patients whose source of pain was confirmed by a clinician, 65% marked the pain as felt in an area different from where the source was. What was associated with the pain spreading elsewhere was not throbbing or the severity of the pain, but the pain coming on by itself, lasting a long time and its character; in other words, exactly the features of irreversible pulpitis. Pain from a lower tooth can be felt in the upper jaw, and pain from a back tooth in the ear or the temple. That is why it is the tests, not you, that show which tooth is hurting.

A throbbing pain does not always come from a tooth, either. A review from the University of Leuven lists pain in the chewing muscles, nerve pain (such as trigeminal neuralgia), headaches and facial pain of vascular origin, heart pain and sinus disease among the conditions that mimic toothache, and sets its aim as preventing wrong and unnecessary dental treatment. In a series of three cases from a dental school in Tokyo, in three women with throbbing pain in the upper molar area, root canal treatment done earlier had not relieved the pain; two had been misdiagnosed with pulpitis. In the end all three were diagnosed with migraine by headache specialists (linked to menstruation in two), and their pain receded with migraine medicine. With throbbing that no tooth reproduces with cold, heat or tapping, this possibility should be put on the table.

The NHS gives concrete thresholds for toothache: it recommends seeing a dentist for toothache that lasts more than 2 days, does not go away with painkillers, comes with a high temperature, pain when you bite, red gums or a bad taste in the mouth, or makes your cheek or jaw swell. It says to go straight to A&E if the area around your eye or your neck has swollen, or if swelling in your mouth or neck is making it hard to breathe, swallow or speak. On its dental abscess page it adds pain or swelling in the eye, a sudden change in vision, widespread swelling in the mouth and difficulty opening the mouth to this list; if any of these is present, call 112 or go to A&E too.

A throbbing toothache is never a pain you can expect to go away permanently on its own. In the situations in the first list, see your dentist as soon as possible; if any from the second list applies, do not wait for an appointment.

The order is set up to establish first whether there is a spreading infection, then which tooth the pain is coming from, and finally whether that tooth's nerve can be saved.

1. 1

   Signs of spread

   Swelling in the face or neck, temperature, how far the mouth opens and swallowing are checked. If any of the signs on the NHS emergency list is present, that picture is dealt with first.

2. 2

   The history of the pain

   You are asked what sets the pain off, how long it lasts once the trigger has gone, whether it comes on by itself, whether it wakes you at night, whether it gets worse when you bite, and whether cold soothes it. Describe the result of the cold water test you did at home here.

3. 3

   Cold and heat tests

   The suspect tooth and its neighbours are tested, as well as a healthy tooth on the opposite side for comparison. Following MSD's description, whether the pain passes within 1 to 2 seconds of the stimulus being removed guides whether the nerve can be saved.

4. 4

   Tapping and biting tests

   The tooth is tapped lightly and you are asked to bite. According to MSD, tenderness on tapping usually shows the inflammation has spread to the tissues around the tooth.

5. 5

   Electric pulp testing and an X-ray

   Electric testing shows whether the pulp is alive but, as MSD points out, not whether it is healthy. On the X-ray, the dentist looks for deep decay, a gap under a filling and changes in the bone at the root tip.

6. 6

   If no tooth reproduces the pain

   If the tests cannot reproduce the pain in any tooth, muscle, sinus, nerve and headache sources are reviewed before starting an irreversible procedure. If needed, a referral is made to oral medicine, ENT or neurology.

The treatment of throbbing depends on what stage the tooth's nerve is at. All of it falls within the field of your own dentist or a root canal specialist (endodontist).

The points below are decisions that either make the pain last longer or lead to an irreversible procedure on the wrong tooth.

The course below is for the usual situation in which the source tooth is correctly found and treated. What the clinician treating you says takes priority.

1. The first day of treatment

   When the nerve or the inflamed pulp is removed, the source of the throbbing is gone. In the study comparing pulpotomy and root canal treatment, pain eased from the first day towards the seventh in both groups.

2. The first week

   Slight tenderness on biting can remain in the tooth and should ease day by day. Not biting hard things with the treated tooth makes this period easier.

3. Check-ups

   Teeth treated with pulpotomy are checked with pulp tests and X-rays at intervals of a few months. In teeth with an abscess at the root tip, healing of the bone is followed on X-rays over months.

We do not give a single figure, because behind a throbbing toothache there may be inflammation that settles with a filling, a tooth that needs root canal treatment and a crown, or migraine that needs no dental treatment at all. These are the items that determine the scope:

What stage the nerve is at

A filling for reversible pulpitis, pulpotomy or root canal treatment for irreversible pulpitis, and for an abscess, drainage followed by root canal treatment or extraction.

The healthy tissue left in the tooth

The remaining tooth tissue determines whether the tooth is finished with a filling or a crown after root canal treatment.

How difficult the canal system is

Molars have more roots and canals; curved or narrowed canals make the work longer and may need a specialist.

Whether the source is in a tooth

If the pain does not come from a tooth, the assessment moves to specialists outside dentistry and no dental treatment is needed.