Patient guide
Why does my tooth hurt when I bite?
Pain on biting has several possible causes, from a high filling to a crack to infection at the root. This guide explains how each one feels, what it usually means and how an endodontist tells them apart.
In this guide
A tooth that hurts when you bite is one of the most common reasons for seeing an endodontist, and one of the most misleading symptoms there is. Several very different problems produce it, and the right treatment depends entirely on which one you have.
A filling or crown that sits too high
If a tooth has recently been filled or crowned and now meets its opposite number before the rest do, every bite loads that tooth alone. The pain is a bruised ache that starts soon after the dental work and may ease between meals. The cure is a small adjustment to the bite by your dentist; left alone, the overloaded tooth can become genuinely inflamed.
A cracked tooth
A crack produces a sharp, brief pain on biting — often most noticeable as you release — and it tends to be hard to pin down to one tooth. Sensitivity to cold or sweet things without any visible decay is common. Cracks do not show on ordinary X-rays and are found with bite tests, dye, light and the microscope. What happens next depends on how deep the crack has gone; see cracked tooth diagnosis.
Inflammation around the root
When the pulp inside a tooth is dying or has died, the ligament that holds the root becomes inflamed and the tooth feels tender to bite on, slightly "high" or bruised. This is often accompanied by, or follows, a period of sensitivity to heat and cold, and by a dull ache that may come and go. It usually means the tooth needs root canal treatment.
Infection at the root tip
If a dead pulp has been left untreated, infection gathers in the bone at the tip of the root. The tooth is tender to bite on and to tap, there may be a swelling or a small boil on the gum, and a bad taste is common. A previously root-treated tooth can do the same if the root filling has failed. See root infection and abscess.
Sinus pressure
The roots of the upper back teeth sit close to the maxillary sinus, and a sinus infection can make several of them ache on biting at once. The clue is that more than one tooth is involved, the pain changes when you bend forward and there are cold-like symptoms. Nerve tests on the teeth are normal.
Grinding and clenching
Heavy grinding, often at night, overloads the teeth and their ligaments. Pain on biting that is worst in the morning, affects several teeth and comes with jaw ache or headaches points this way. Your dentist may suggest a night guard; the teeth themselves usually need nothing.
How the cause is identified
History first — when the pain started, what it feels like, whether anything has been done to the tooth recently — then an examination under magnification, nerve tests with cold and an electric tester, tapping and pressure on each suspect tooth, a bite test for cracks and small X-rays. Together these separate a tooth that needs root canal treatment from one that needs a bite adjustment or no treatment at all. A toothache investigation appointment takes about 45 minutes and ends with a written explanation.
When to be seen quickly
Pain on biting with a swelling, a tooth that is becoming loose, or pain that wakes you at night should be assessed promptly — say your symptoms are urgent when you book. A swelling that is spreading rapidly or difficulty swallowing needs medical help straight away through NHS 111 or A&E.
Endodontist Northampton · November 2026