Teeth marks on the tongue: what does a scalloped edge mean?

The tongue is a muscular organ that sits next to the teeth inside the mouth all the time. Normally, at rest, it leans lightly against the inner surface of the teeth but does not press hard enough to leave a mark. When the tongue rests against the teeth forcefully for hours, or takes up too much room for the inside of the mouth, the indentations of the teeth stay printed along its edge like a permanent wave. The mark itself does not hurt, does not cause sores and needs no treatment; what it points to varies from person to person.

The first thing to know is that this appearance is also common in people who do not have apnoea. In a group of 100 patients without sleep apnoea, examined in a sleep laboratory and an ear, nose and throat clinic, 28 per cent had scalloping along the edge of the tongue. So seeing teeth marks on your tongue does not mean there is a disease; it is only a sign whose cause is worth looking at.

The commonest and simplest cause is clenching. In people who clench their jaw at stressful moments during the day or in their sleep at night, the tongue is pushed towards the teeth too and the mark deepens. Stress and anxiety are known to be the commonest cause of clenching; sleep disorders, some medicines, smoking, and a lot of alcohol and caffeine also go with it. In this picture, the mark on the tongue often comes with jaw pain in the morning, worn tooth edges, headaches in the temples, or grinding that your partner hears.

Another cause is a tongue that is large for the space in the mouth. In medicine, the picture where the tongue really is enlarged is called macroglossia, and it is described like this: the tongue at rest extends beyond the row of teeth or the arch of the toothless ridge. There is also the case where the tongue itself is normal but looks large because the mouth is small; this is called relative macroglossia. In both, the tongue rests against the teeth all the time and a mark is left along its edge. True macroglossia is rare in adults and is usually a sign of another underlying condition.

Sleep apnoea is the link people wonder about most, and the strength of the evidence needs reading correctly. In a study of 1,130 people from the community in Japan, drops in oxygen at night were found more often in those with moderate or marked scalloping of the tongue; but this link was significant only in people who were overweight, and no clear difference appeared in those of normal weight. So scalloping may be a sign, but as we saw above it is also found in many people without apnoea; it is not a diagnostic tool on its own.

That is why what actually helps is reading the scalloping not on its own but together with other signs. In a study of 160 patients in a sleep laboratory, people with a neck circumference of 40 centimetres or more and scalloping of the tongue had an odds ratio of about 4.2 for severe sleep apnoea (confidence interval 1.9 to 9.2). Nine in ten of this group already had apnoea, and in the same study scalloping on its own showed no significant link with the presence of apnoea. If loud snoring, a partner who notices your breathing stopping in your sleep, morning headaches and tiredness that lasts all day come with your scalloped tongue, what needs discussing is not your tongue but your sleep.

An underactive thyroid gland can also enlarge the tongue. In hypothyroidism, a kind of protein-rich substance builds up in the tissue of the tongue and the tongue thickens. In this case the mark on the tongue often comes with other symptoms such as feeling the cold, unexplained weight gain, constipation, a hoarse voice, and puffiness in the face and around the eyes. If there is a picture like this, you need to see not a dentist about your tongue but your doctor for a thyroid blood test.

Dehydration, allergies, infections, smoking, some vitamin deficiencies and jaw joint problems are also counted among the causes that leave marks along the edge of the tongue. What they have in common is the tongue swelling temporarily or resting more against the teeth. A rare but important cause is sudden swelling of the tongue: in a 78-year-old patient taking blood pressure medicine, swelling of the tongue that started within a few hours came with marked teeth marks on both sides, and the patient became unable to speak or swallow. The swelling went down the next day, and the cause was thought to be the blood pressure medicine the patient was taking. Here the teeth marks were a sign of new, fast-developing swelling.

The distinction below is not a firm diagnosis; it is a framework showing when you can relax and when you should see your doctor or go to A&E.

The sequence below describes the steps to follow once you notice the mark on your tongue. If there is no emergency picture, the first place to go is your dentist or your GP.

1. 1

   First, check whether it started suddenly

   If the tongue has swollen within a few hours, or speaking, swallowing or breathing has become difficult, do not wait for the next steps; call 112. If there is a medicine you have recently started, especially a blood pressure medicine, tell the team.

2. 2

   Look at where your tongue sits in the mirror

   Open your mouth slightly and let your tongue relax. If the tongue spills over the teeth at rest, it may be large for the mouth. Look at whether the marks are on both sides and similar, and whether they change between morning and evening; taking a photo helps at the next examination.

3. 3

   Gather the signs of clenching

   Jaw pain in the morning, worn or broken tooth edges, headaches in the temples, grinding at night: if any of these applies, tell your dentist. By looking at the wear surfaces on the teeth and at the jaw muscles, the dentist can largely assess clenching through the examination.

4. 4

   Ask about your sleep

   Ask someone who sleeps beside you whether you snore and whether your breathing stops. Measure your neck circumference. If snoring and daytime tiredness go together with a scalloped tongue, your GP can refer you for a sleep test.

5. 5

   Go over the general symptoms

   Symptoms such as feeling the cold, weight gain, constipation, a hoarse voice and puffiness in the face suggest the thyroid; thirst and a dry mouth suggest fluid balance. Tell your doctor about these rather than your dentist; a blood test is requested if needed.

6. 6

   A plan is made according to the cause

   For clenching, a protective guard and managing stress; for sleep apnoea, treatment for sleep; for an underactive thyroid, medicine. As the cause improves, the swelling of the tongue and how marked the scalloping is often lessen too.

There is no treatment specific to the mark on the tongue; what is treated is the cause. The options below do not replace one another; the examination decides which is needed.

The mark on the tongue does no harm on its own. The risk of being missed lies not with the mark but with the cause behind it.

How long the mark takes to fade depends on its cause. The course below is a general framework; your doctor or dentist gives the exact timetable.

1. The first few days

   Marks caused by dehydration or temporary swelling can fade within a short time as fluid balance improves. With sudden swelling, on the other hand, the first hours need emergency follow-up.

2. The first few weeks

   Once a guard and stress management are started for clenching, jaw tiredness in the morning is usually the first symptom to improve. The mark on the tongue fades more slowly.

3. Over months

   As the swelling of the tongue decreases with treatment for sleep apnoea or the thyroid, the marks fade too. The mark may not disappear completely; the real goal is to have not the mark but the cause under control.

4. If it stays

   In people whose tongue is large for the mouth, the mark can stay as part of their make-up. If there is no pain, sore or other symptom, this is not something that needs treatment.

The mark on the tongue itself needs no procedure; the scope is set by investigating and treating the cause behind it. These are the items that determine it:

Whether the cause lies in the mouth or in general health

Clenching falls within the dentist's remit; sleep apnoea and the thyroid fall within your doctor's.

Whether a protective guard is needed

For clenching, a guard made for your mouth is a separate item; if there is wear or fractures on the teeth, repairing them is added.

A sleep test

The overnight test done when sleep apnoea is suspected, and the treatment that follows, are a separate process planned by the sleep centre.

Blood tests

Checking thyroid and vitamin levels falls within the remit of your GP or doctor.