Why does one tooth hurt when you bite down?

Why biting singles out one tooth

Chewing puts a large, brief load on a tooth. A healthy tooth and the ligament that cushions it in the bone absorb that load without complaint. When something about the tooth or its support has changed, the same load produces pain, and because the problem is usually in one place, usually one tooth hurts. The examination works out which part has changed: the tooth, the nerve inside it, the ligament and bone around it, or the gum. The pattern you notice gives the first clue.

The pattern usually narrows the cause

Sharp pain on biting, often worse on release, that fades quickly

A sharp, sometimes erratic pain when you bite on something, and especially when you let go, is the classic pattern of a cracked tooth. The pieces flex apart and snap back as you load and release, irritating the pulp (the nerve) inside. The pain may come and go, and the tooth may also react to hot or cold. Cracked teeth are often hard for the patient and even the dentist to pin down, because the tooth can look normal and the pain does not always repeat on command. This is not usually a same-day emergency, but it should be examined soon, because a crack that is caught early is easier to manage than one that has spread toward the pulp or the root.

A constant ache, a tooth that feels taller, tenderness when tapped

When the nerve inside a tooth dies or becomes infected, inflammation builds up at the tip of the root. The ligament around the root swells, so the tooth may feel slightly raised and meets the opposing teeth first, and any pressure on it, from chewing or even from a fingertip tap, hurts. A tooth abscess typically causes a continuous, severe toothache that is worse when chewing, and it may come with a swollen or tender gum, a bad taste, a sense of pressure, or fever. This pattern deserves a call to the office as soon as it is open, so the tooth can be assessed and drained or treated. If the office is closed, send an appointment request, and treat spreading swelling, fever with facial swelling, or trouble swallowing or breathing as an emergency (see below).

Pain only since a new filling or crown

A filling or crown that sits even slightly high meets the opposing tooth before everything else does, so that tooth takes the first and hardest hit on every bite. The usual result is a tooth that is sore to pressure within days of the appointment, sometimes with an initial sharp twinge that settles into a dull ache. This is a routine call, not an emergency: a small adjustment to the new restoration usually resolves it. Do not try to grind or file the restoration yourself.

Pain with cold or sweet, plus a visible hole, rough edge or missing piece

Decay that has reached the dentin (the softer layer under the enamel), a filling that has broken or come loose, or a chipped edge can all let chewing pressure and temperature reach the sensitive inner tooth. The pain is often triggered by cold, sweet or acidic foods as well as by biting, and you may be able to feel the defect with your tongue. Schedule an appointment soon, within days rather than weeks, because untreated decay tends to progress and can lead to pain and infection. A cavity can also be present without any pain at all; see Can you have a cavity without tooth pain? for why early decay is often silent.

Morning soreness in several teeth or in the jaw muscles

If the tenderness is worst when you wake, moves between teeth, or comes with tight or tired jaw muscles, headaches or worn-looking edges, clenching and grinding during sleep may be the cause. Grinding can leave teeth sore and sensitive and can also crack or chip them, so a tooth that started as a grinding complaint can turn into a crack complaint. This is a routine appointment; a dentist can check for wear and may discuss a night guard.

Several upper teeth ache during a cold or with congestion

Sinus inflammation is a recognized cause of toothache in the upper back teeth, which sit near the sinuses. The pressure can be felt in those teeth as a dull ache that often involves more than one tooth and tends to ease as the congestion clears. This is referred pain: pain that is felt in the teeth but starts somewhere else. If the ache persists after the cold is gone, or if one tooth stands out, a dental examination can check whether a tooth is the real source.

A sore, swollen or bleeding gum beside the tooth

When the gum next to the tooth is tender, swollen or bleeding, or food keeps packing between two teeth, pain on biting can come from a gum pocket or gum abscess rather than from the nerve. Gum disease can make chewing painful. Gum measurements and a cold test separate the two; this is usually a routine appointment unless swelling or fever develops.

What the dentist checks

An examination for pain on biting is methodical, because several of these causes can look alike.

• Bite test on individual cusps. You bite on a small instrument placed on one cusp (one of the raised points of the chewing surface) at a time. A crack usually hurts on one specific cusp, often on release, which helps locate both the tooth and the part of it that is involved.
• Tapping (percussion). Tenderness when the tooth is tapped points toward inflammation in the ligament around the root, which is common with an infected nerve or a high restoration.
• Cold test. A cold stimulus on the tooth checks whether the nerve is alive and how it reacts. A brief response that stops quickly is usually normal; pain that lingers, or no response at all, suggests the nerve is inflamed or has died.
• Gum measurements and palpation. Measuring the pocket around the tooth and pressing on the gum helps separate a gum or ligament problem from a nerve problem.
• X-rays. These show decay, the fit of fillings and crowns, bone loss, and changes at the root tip that develop when a nerve has been dead for some time.
• Checking the bite and signs of grinding. Marking paper shows which teeth meet first, and wear patterns suggest clenching or grinding.

Why cracks often do not show on X-rays

Patients are often surprised when an X-ray looks normal and the dentist still suspects a crack. Most cracks in back teeth run from front to back along the tooth, across the path of the X-ray beam rather than along it, so the thin line is not captured. Cracks also have no width to speak of until they have progressed. For that reason, the diagnosis rests mainly on the history, the bite test, staining dyes, shining a light through the tooth, and sometimes removing an old filling to look underneath. Three-dimensional imaging is used in selected cases but is not a routine first step.

Until you are seen

• Chew on the other side and avoid hard, sticky or very cold foods on the sore tooth.
• Over-the-counter pain relievers may be used only as directed on the label. Do not place aspirin or any other painkiller against the gum next to the tooth; it can burn the tissue.
• Keep the area clean. Gentle brushing and rinsing with warm water are fine; flossing can remove trapped food that adds pressure.
• Do not adjust the tooth or a restoration yourself, and do not use sharp objects to probe a suspected hole.
• Antibiotics are usually not the answer for a toothache on their own. Most causes of pain on biting need dental treatment, and a dentist decides whether an antibiotic is appropriate alongside it.

When this is an emergency

Go to emergency care (call 911 or the nearest emergency department), not to a dental appointment request, if you have any difficulty breathing or swallowing, rapidly spreading swelling of the face or neck, fever together with facial swelling, uncontrolled bleeding, or a severe injury. Those signs can mean an infection is spreading beyond the tooth. Facial swelling with tooth pain: when emergency medical care comes first explains these signs in more detail. Emergency care is among the services listed on the practice's website; ask the team, during office hours, how they prefer to be contacted for an urgent problem, and see the services page for what emergency care covers.

What to tell the office when you call

The more precisely you can describe the pattern, the easier it is for the team to judge urgency and plan the visit. Have ready:

• which tooth, or at least which side and whether upper or lower;
• whether it hurts when you bite down, when you release, or both;
• whether hot, cold or sweet triggers it, and how long the pain lingers afterward;
• whether the pain comes on by itself or wakes you;
• any swelling of the gum or face, bad taste, or fever;
• any recent dental work on that tooth or nearby;
• whether you clench or grind, or wake with a sore jaw.

For a toothache that starts at night, Tooth pain tonight: what information helps your dentist decide urgency? walks through the same questions in more detail.

The next step

Pain on biting in one tooth is a signal worth acting on: cracks, decay and infected nerves all tend to become larger problems when they are left alone, and a high filling is often resolved with a simple adjustment. Note the pattern using the table below, chew on the other side, and contact the office during its hours or send an appointment request describing what you have noticed. A request is not a confirmed appointment; the team will follow up. If any of the emergency signs above appear, seek emergency medical care first.