My tooth hurts but I cannot see a cavity: what could be causing it, and what will the dentist check?

Why a tooth can hurt when nothing shows

A mirror shows you the outer enamel of the teeth you can reach with a light. Most of the places where pain starts are out of view: the surfaces between teeth, the tooth under an existing filling or crown, the root, the nerve chamber inside the tooth, and the bone and ligament that hold the tooth in place. A cavity large enough to see as a dark hole is often already well advanced; much decay is found by examination and X-ray before the patient can see it, so a painful tooth that "looks fine" is common rather than mysterious. The guide Can you have a cavity without tooth pain? explains the reverse problem.

The usual hidden causes, roughly in the order a dentist tends to consider them:

• Decay between teeth or under a restoration. Plaque collects where a toothbrush cannot reach, and decay there can reach the sensitive dentin layer with no change on the visible surface.
• A crack. Cracks can be too fine to see and often do not show on an X-ray. The classic sign is a sharp pain when biting, often when you release the bite, and sensitivity to temperature. See Sharp pain when you release your bite: the cracked-tooth clue explained.
• An inflamed or dying nerve. The pulp inside a tooth can become inflamed from deep decay, a crack, a heavy bite or past trauma. An irritated nerve may react sharply to cold and settle within seconds; once more seriously inflamed it aches for a while after cold, and later it may ache on its own or throb.
• An inflamed gum pocket or ligament. Gum disease, food trapped under the gum, or a tooth bruised by a heavy bite can make the tooth tender to pressure without anything wrong inside it.
• A filling or crown that meets first. If a recent restoration sits slightly high, that tooth may take the first contact on every bite and can become sore.
• Clenching and grinding. Often done during sleep without awareness, it can leave teeth sensitive, achy or chipped and the jaw muscles sore in the morning.
• Sinus pressure. The roots of the upper back teeth sit close to the sinus floor. Sinus inflammation can produce a dull ache in several upper teeth at once, along with facial pressure or congestion.
• Referred pain from the jaw joint or chewing muscles. Pain from a temporomandibular disorder can spread across the face and be felt in the teeth.

What changes the answer

Your description narrows the list more than any single test, so it helps to think these through beforehand:

• The trigger. Cold, heat, sweet, biting down, letting go after biting, or nothing at all.
• How long it lasts. A twinge that stops within seconds points one way; an ache that lingers well after the cold or heat is gone, or starts on its own, points another.
• How sure you are of the tooth. Pain from the nerve inside a tooth is often hard to pin down and can feel as if it comes from a neighboring tooth or from the opposing jaw on the same side. Pain from the gum or ligament around a tooth is usually easier to locate.
• Recent dental work on that tooth or its neighbor in the past weeks.
• Sinus or jaw symptoms. Congestion, a recent cold, facial pressure, jaw clicking, jaw stiffness or morning soreness.
• Gum signs. Bleeding, a bad taste, a puffy gum, or a tooth that feels slightly loose.

Pain patterns and what they often point to

These are patterns, not diagnoses; the exam is what separates them.

• A brief twinge with cold or sweet that stops quickly often means exposed dentin from early decay, wear or an exposed root, or a nerve that is irritated but can recover.
• Pain that lingers after hot or cold suggests the nerve is more seriously inflamed and should be checked soon.
• A sharp pain when biting or releasing the bite is the typical crack pattern, though a loose filling or decay can produce it too. Why does one tooth hurt when you bite? goes through these patterns in detail.
• A dull ache across several upper back teeth, with congestion or facial pressure raises the question of the sinuses.
• A constant throbbing ache, pain that wakes you, or a tooth that hurts to touch suggests the nerve is dying or an infection is building, and needs prompt attention.
• Any swelling of the gum or face, or fever with tooth pain needs same-day professional attention, and the emergency routing below if the swelling is spreading or if fever comes with facial swelling.

What the exam may check

Not every test is done at every visit; the dentist chooses the ones that fit your description.

Looking, drying and magnifying

The tooth and its neighbors are usually dried and examined under good light, often with magnification. Drying matters because a wet surface can hide early decay and fine craze lines. A bright light shone through the tooth, or a dye, may be used to make a crack stand out, and the edges of existing fillings and crowns are checked.

X-rays, and why a recent one may still miss something

X-rays show what the eye cannot: decay between teeth and under restorations, the shape of the nerve chamber, and changes in the bone around the root tip that point to a nerve problem. Which X-rays are taken, and whether any are needed, depends on your history and the findings so far rather than on a fixed schedule; Do you need dental X-rays at every check-up? explains that decision. One limitation is worth knowing: a crack often does not appear on an X-ray at all, and early changes around a root can take time to show. A normal recent X-ray therefore does not rule out a crack or an early nerve problem.

Tapping, cold and bite tests

• Tapping (percussion). A gentle tap on each tooth tests the ligament around the root. A tooth that is tender to tapping usually has inflammation around it, whether from the nerve, the gum or a high bite.
• Cold test. A cold stimulus is applied to the suspect tooth and to healthy teeth for comparison. A short, sharp response that fades quickly suggests a nerve that can recover; a response that lingers suggests more serious inflammation; no response at all can mean the nerve has died.
• Bite test. You bite on a small instrument placed on one cusp at a time. Pain on one cusp, especially on release, is a strong pointer to a crack in that part of the tooth.

The gums and the bite

A periodontal probe measures the depth of the gum pocket around the tooth. A deep or bleeding pocket, or a tooth that moves slightly, points toward the gum and ligament rather than the nerve. The dentist also looks at how your teeth meet: whether the painful tooth or a recent restoration contacts first, and whether flattened wear facets or chipped edges suggest clenching or grinding.

Sinus and jaw questions

For an upper back tooth, you may be asked about recent colds, congestion and facial pressure. For any tooth, you may be asked about jaw clicking, stiffness, limited opening or morning muscle soreness, and the jaw joint and chewing muscles may be gently pressed.

When the findings do not match the pain

Sometimes every test comes back normal, or the tooth that reacts is not the one that hurts. That is a finding in itself. Reasonable options include monitoring and re-testing in a week or two, treating a likely cause such as a high spot or a gum pocket and seeing whether the pain resolves, taking a different X-ray view or a 3D image, or referring to a specialist in the nerve of the tooth or in facial pain. Re-testing before treating protects you from treatment the tooth may not need.

What is safe to do until you are seen

• Over-the-counter pain relievers, as directed on the label. The ADA's guidance for acute dental pain favors non-prescription anti-inflammatory medicines, alone or combined with acetaminophen, over opioids for most adults. Check with a pharmacist or physician first if you have other health conditions, take blood thinners or are pregnant.
• Chew on the other side and avoid very hot, very cold or hard foods on the painful tooth.
• Keep the area clean. Gentle brushing and flossing can dislodge food that is pressing on the gum.
• Do not take leftover antibiotics. Most tooth pain is not treated with antibiotics; the ADA recommends dental treatment of the cause instead, with antibiotics generally reserved for infection that is spreading or accompanied by fever or feeling unwell.
• Do not place pills or other remedies on the gum. They do not treat the cause, and the tooth still needs to be examined.

When to go to emergency care first

Go to the nearest emergency department or call 911, rather than waiting for a dental appointment or using the online request form, if tooth pain comes with difficulty breathing or swallowing, swelling that is spreading quickly across the face, toward the eye or into the neck, fever together with facial swelling, bleeding that will not stop, or a serious injury to the face or jaw. These can be signs of an infection spreading beyond the tooth. For everything else, a dental office is the right place to call; Tooth pain tonight: what information helps your dentist decide urgency? covers what to say.

The next step

Write down the trigger, how long the pain lasts, which tooth you think it is, and any recent dental work, sinus or jaw symptoms. Then request an appointment or call the office during hours, and say that you have tooth pain so the team can plan the visit. A request through the form is not a confirmed appointment; the team follows up. Loul Dental Studio lists check-ups with digital X-rays and bite assessment, and emergency care, among its services.