The short answer
Teeth usually become sensitive when the softer layer under the enamel, called dentin, is exposed. That can happen when enamel wears thin, when gums recede and uncover the root, or when a tooth has decay, a crack, a worn filling or gum disease. Whitening and grinding can add to it. Desensitizing toothpaste helps many people, but a lasting zing deserves an exam to find the cause.
General information, not a diagnosis. Your dentist will examine your mouth before recommending treatment.
What is happening inside the tooth
You sip something cold and get a sharp jolt that fades in a second or two. Or you bite into a cookie and one tooth complains. Either way, something is letting the outside world reach the inside of the tooth.
Enamel is the hard outer shell. Under it sits dentin, a softer layer full of tiny channels that lead toward the nerve. When enamel wears thin or the gums pull back and uncover the root, which has no enamel at all, those channels are open, and temperature or sweets can reach the nerve. That is dentin hypersensitivity, the formal name for sensitive teeth.
Decay, a crack or a worn filling does the same thing by a different route: it opens a path through the tooth itself. So the question is not only whether the teeth are sensitive, but what opened the path. The answer decides whether toothpaste, a filling or something else is the fix.
The common causes
The ADA's patient site lists the usual reasons dentin becomes exposed, and most people have more than one going on at once. A few other causes are easy to overlook because they come from habits rather than disease.
- Worn enamel, often from acidic drinks, reflux or brushing too hard with a stiff brush.
- Exposed root when gums recede. Root surfaces are not protected by enamel and are often sensitive to hot and cold. See receding gums: causes and treatment.
- Tooth decay, which can cause sensitivity to sweets, hot or cold as it advances.
- A cracked or fractured tooth, which tends to hurt when you chew or when you release the bite. See cracked tooth symptoms and treatment.
- Worn fillings that no longer seal the tooth.
- Gum disease, which can lead to recession and exposed roots.
- Whitening, because the peroxide can reach the dentin; this sensitivity is usually temporary.
- Grinding or clenching, which can wear, chip or crack teeth over time.
How to tell the clues apart
The pattern of the pain is useful information, so pay attention before your visit. A brief zing from cold across several teeth is the classic picture of worn enamel or recession. A sharp pain in one tooth when you bite down or let go is the classic picture of a crack.
Pain that lingers after the hot or cold is gone can mean the pulp inside the tooth is inflamed, which is one of the signs that root canal treatment may be needed. Sensitivity to sweets often points to decay or a leaking filling. Sensitivity that began right after whitening or after a new filling usually has an obvious cause and often settles.
The table below is a guide for the conversation, not a diagnosis. Only an exam, and sometimes an X-ray, can tell a shallow cavity from a crack from exposed dentin.
| What you notice | Often points to | What usually helps |
|---|---|---|
| Brief zing from cold on several teeth | Worn enamel or receding gums exposing dentin | Desensitizing toothpaste, soft brush, fluoride at the office |
| One tooth, sharp pain when biting or letting go | Cracked tooth or fractured cusp | Exam; filling, crown or root canal depending on the crack |
| Sweet foods set it off | Decay or a worn, leaking filling | Filling or crown after the dentist checks |
| Pain lingers after hot or cold is gone | Inflamed pulp inside the tooth | Prompt exam; root canal treatment may be suggested |
| Started right after whitening | Peroxide reaching the dentin | Pause whitening, desensitizing toothpaste, try again later |
| Worse in the morning with a sore jaw | Grinding or clenching | Exam for wear; a custom night guard |
| Tooth looks longer, root showing | Gum recession | Find the cause; gentle brushing; graft if tissue is lost |
What helps at home
Desensitizing toothpaste contains compounds that help block the transmission of sensation from the tooth surface to the nerve. The ADA notes that twice-daily use of toothpastes with stannous fluoride, potassium or arginine can be recommended to reduce dentin hypersensitivity pain. Use it as your regular toothpaste rather than a one-off.
Switch to a soft-bristled or electric brush and let the bristles do the work with light pressure, especially near the gumline. If whitening set it off, pause and try again later. If you wake with a sore jaw, ask about a custom night guard, since store-bought guards may not protect as well as one made for you.
What home care cannot do is fill a cavity, seal a crack or regrow gum tissue. If the zing is new, getting worse, or limited to one tooth, treat the toothpaste as a bridge to the exam, not a replacement for it.
What the dentist may do
At a dental checkup the dentist looks at each tooth and your gums, may take X-rays, and checks existing fillings. Tell the dentist which teeth react, to what, and for how long; that history narrows the search before any instrument touches a tooth.
From there, the ADA's patient site lists the treatments that match each cause. An in-office fluoride gel can strengthen enamel and reduce the transmission of sensation. A filling, bonding, inlay or crown corrects a flaw or decay. A gum graft protects a root where tissue has been lost, and root canal treatment is reserved for sensitivity that is severe, persistent and cannot be handled any other way.
If recession is the cause, the first job is finding out why, because recession from hard brushing and recession from gum disease are treated differently. The receding gums page explains the exam. If a graft is indicated, your dentist may refer you to a periodontist, a dentist with additional training in treating the gums. If the question is how much tooth is damaged, crown vs. filling vs. onlay explains how the choice is made.
When not to wait
Most sensitivity is a nuisance rather than an emergency, and acid wear and early decay look different; enamel erosion vs. cavities walks through that. Some patterns should move you to call sooner.
Call promptly for a toothache that does not go away, pain when chewing, a tooth that hurts long after the cold is gone, or sensitivity after a blow to the mouth. We offer same-day appointments when possible. Swelling of the face or jaw with fever, or any trouble breathing or swallowing, is an emergency room matter first; emergency dentist or ER lays out where to go.