What causes dry mouth, and does it harm your teeth?

Saliva does far more work in your mouth than you might think. It neutralises acids from food, carries calcium and phosphate to strengthen your enamel, makes chewing and swallowing easier, and constantly washes bacteria out of your mouth. When your salivary glands work less than they should, all of these jobs are disrupted at once; the result is not just an uncomfortable dryness but a whole system that protects your teeth and gums switching off.

The most common cause is medicine. Some antidepressants, blood pressure medicines, antihistamines, diuretics and some painkillers slow down how your salivary glands work. Most of these medicines are not given to reduce saliva; dryness is a side effect. If your mouth started to feel dry shortly after you began a new medicine, this is most likely the connection: do not stop taking it on your own decision, tell your doctor and check the patient information leaflet.

Radiotherapy to the head and neck damages the tissue of the salivary glands directly. Even after treatment ends, saliva production may not return to its previous level; when this happens, dryness becomes permanent and your daily care routine changes permanently to match. In patients having chemotherapy, dryness is usually seen during treatment and eases once treatment finishes.

Sjögren's syndrome is an autoimmune condition in which the immune system attacks the salivary and tear glands. Dry mouth is usually accompanied by dry eyes; if the two occur together and there is no other cause, you need to discuss this with your doctor. This is not something a dentist can diagnose alone; it needs a rheumatology assessment.

Uncontrolled blood sugar also dries out your mouth: as your body gets rid of excess sugar through urine, fluid loss increases, and this shows up in your saliva too. If you have diabetes and your mouth has recently started feeling dry, tell your doctor how your blood sugar readings have been running; dryness is sometimes one of the first signs that control has slipped.

Sleeping with your mouth open at night, a blocked nose or snoring are also common causes of morning dryness. This pattern is usually limited to the night and eases during the day; it is different from a lasting problem with the salivary glands themselves. If your nose is persistently blocked, an ear, nose and throat (ENT) assessment may be needed.

Ageing itself does not dry out the salivary glands; the dryness seen in older patients mostly comes from taking more medicines. In patients taking several medicines together, dryness comes not from any single medicine's effect but from several medicines with the same side effect adding up. Not drinking enough water and too much caffeine also make dryness more noticeable, but on their own they are not strong enough to cause constant dryness; if dryness is constant, one of the causes above should be considered.

The list below separates the situations where your dryness matches the causes above from those where something else needs investigating.

For dry mouth, the place to go is your dentist; in some cases your GP or another specialist gets involved too. The sequence below shows what should be discussed at the examination.

1. 1

   List your medicines

   Write down every medicine and supplement you take, and when you started each one. If dryness is new, checking which medicine was added is the first step.

2. 2

   Notice the pattern of your dryness

   Note whether it is worse only in the morning, all day, or while eating. Dryness limited to the morning points to how you breathe at night; constant dryness points to a medicine or a systemic cause.

3. 3

   Tell both your dentist and your doctor

   You need to tell both: your dentist assesses the damage in your mouth, your doctor looks at the underlying cause or medicine options. Neither replaces the other.

4. 4

   An oral examination

   Early decay, the state of your gums, denture fit if you wear one, and signs of a fungal infection are checked. In a dry mouth, decay usually starts near the gum line and between the teeth.

5. 5

   Further investigation if needed

   If dry eyes and joint pain are present, a referral to rheumatology may follow; if diabetes is suspected, a referral to general medicine. Dentistry is the starting point of this investigation, not the end of it.

These do not treat the underlying cause of dryness, but they reduce daily discomfort and protect your teeth.

Our aim is not to alarm you, but to make clear what you need to take seriously.

Whether dryness clears depends on its cause; so instead of a single timeline, the course here varies depending on the cause.

1. The first few days

   Moisturising products and drinking water often reduce daily discomfort. This does not treat the underlying cause, only eases the symptom.

2. A few weeks, if a medicine change is tried

   If your doctor has changed your medicine, you will see the effect within a few weeks. If nothing changes, this can show that the medicine was not the only cause.

3. Dental check-ups become more frequent

   For patients with chronic dryness, your dentist shortens the check-up interval from six months to three or four months; decay and gum disease are caught early.

4. If dryness after radiotherapy is permanent

   If the damage to the salivary glands is permanent, dryness becomes permanent too; here the aim is not to wait for it to pass but to protect your teeth with fluoride care and regular check-ups.

Dry mouth itself is not a procedure; what determines the cost is the extent of the damage it has caused to your teeth and gums. The items involved:

The scope of the decay and gum check

The longer dryness has gone on, the more areas may need checking; cases caught early stay more limited in scope.

Refitting a denture

In denture wearers, loss of fit can recur often while dryness continues; these adjustments are a separate item.

The protective products used

Saliva substitute gels, sprays or specialist toothpastes may be over the counter or on prescription; the choice depends on how severe the dryness is.

How often you are checked

In patients with chronic dryness, check-ups become more frequent, so the yearly total is calculated separately.