Why does one tooth hurt when I eat something sweet?

Why one tooth reacts to sweets

Enamel, the outer shell of a tooth, has no nerve supply. Underneath it sits dentin, a layer threaded with thousands of microscopic fluid-filled tubules that run toward the pulp, where the nerve lives. When enamel or the thin covering on a root (cementum) is worn through, broken or dissolved by decay, those tubules open to the mouth. Sugary foods and drinks pull fluid outward through the open tubules, the fluid shift stimulates the nerve endings near the pulp, and you feel a short, sharp jolt. Cold, heat, acids and sticky foods can do the same thing. This is the hydrodynamic explanation of dentin sensitivity, and it is the most widely accepted account of why exposed dentin hurts.

The question is not whether dentin is exposed; sweet sensitivity suggests that it usually is. The question is how it became exposed on that one tooth. The common routes are:

• A cavity that has reached dentin. Early decay confined to enamel is usually silent, which is why cavities are often found at check-ups rather than by symptoms (see Can you have a cavity without tooth pain?). Sensitivity to sweets, hot or cold is one of the first signs that decay has moved deeper.
• A worn, chipped or leaking filling. Fillings wear and their edges can open, letting sugars reach dentin at the margin or allowing new decay to form beneath the filling.
• A crack. A cracked tooth often hurts erratically when chewing or when biting pressure is released and is commonly sensitive to temperature; because a crack can expose dentin, sweets can set it off as well.
• An exposed root. Gum recession, or abrasion at the gum line, uncovers root surface that is softer than enamel and more easily sensitized.
• Worn enamel. Frequent acidic foods and drinks, or heavy grinding, can thin enamel until dentin is near the surface.

Several of these can look identical from the outside. A tooth that appears healthy can still have decay between it and its neighbor, or under an older filling, which is why the pattern of your symptoms is useful information and an examination is still needed to name the cause.

What the pattern of pain may suggest

Dentists use the trigger, the duration and what else accompanies the pain to decide how soon a tooth should be seen. The table in the printable section below lays this out in full. In brief:

• A sweet-only twinge that stops as soon as you swallow or rinse often points to early dentin exposure or a small cavity. Schedule an examination in the next few weeks.
• Sweet plus cold, with pain that lingers well after the cold or sweet is gone suggests deeper decay or an inflamed nerve. Call the office this week.
• Sweet plus pain when you bite or release a bite is the classic pattern of a cracked tooth or a failing filling. Call this week, and avoid chewing on that side.
• Sweet sensitivity at the gum line on several teeth is more typical of recession or enamel erosion than of a cavity in one tooth. A routine visit is usually appropriate.
• Sweet sensitivity with a constant ache, throbbing, or gum or facial swelling may mean the nerve is infected or an abscess is forming. Call the office today; if the office is closed and the swelling is growing, do not wait for it to reopen: go to an urgent care clinic or emergency department.

These are patterns, not diagnoses. Other conditions can mimic dentin hypersensitivity at different stages, and the only way to confirm the cause is to examine and test the tooth.

Why sweet, cold and biting are different clues

Sweet and cold both work through the dentin tubules, but a brief reaction that disappears immediately usually indicates that the nerve is still healthy and simply responding to a stimulus. When cold pain lingers after the stimulus is gone, or when the tooth starts hurting on its own, the pulp itself is more likely to be inflamed. Pain on biting is a different signal again: it often means that two pieces of a cracked tooth or a loose filling are flexing against each other under load. Writing down which triggers set the tooth off, and for how long, is worth doing before your visit; Tooth pain tonight: what information helps your dentist decide urgency? walks through the questions you are likely to be asked.

What the examination involves

An examination for a sweet-sensitive tooth typically includes:

• Looking and probing. The dentist checks for soft or stained areas, open filling margins, chips and visible cracks, and looks at the gum line for recession or wear.
• Bitewing X-rays. These show decay between teeth and under existing fillings, which the eye cannot see. Whether new X-rays are needed depends on what is already on file and your decay history, not on a fixed schedule (see Do you need dental X-rays at every check-up?).
• A cold test. A cold stimulus is applied to the suspect tooth and to a healthy neighbor for comparison. How quickly the tooth responds and how long the sensation lasts helps the dentist judge how the nerve is responding and whether the pain lingers.
• Bite testing. Biting on a small instrument tooth by tooth can locate a crack or a filling that moves under pressure, since cracks often do not show on X-rays.

At Loul Dental Studio, check-ups include a clinical examination with digital imaging and a bite assessment; ask the office which tests are appropriate for your tooth.

What treatment may involve

The treatment follows the cause, and the range is wide:

• Early damage without a cavity may be managed with fluoride applied at the office or in a prescription toothpaste, desensitizing toothpaste, and changes to how often you have sugars and acids. The tooth is then monitored. Early enamel damage versus a cavity: why treatment can differ explains how that decision is made. Not every early lesion can be stabilized, and a lesion that progresses into dentin usually needs a filling.
• A cavity into dentin is usually treated by removing the decay and placing a filling; several filling materials exist, and the dentist can explain which suits the location.
• A worn or leaking filling is generally replaced, sometimes with a larger restoration if decay has spread beneath it.
• A cracked tooth may need a restoration that holds the pieces together, which can mean a partial-coverage restoration or a crown depending on how far the crack extends. See When a partial-coverage restoration may be discussed instead of a crown.
• An exposed root may be treated with desensitizing agents, bonding over the exposed surface or, in selected cases, a gum graft. Do receding gums always need a graft? covers that decision.
• An inflamed or infected nerve may require root canal treatment to save the tooth.

A tooth that already has a crown can still develop decay at its margin and become sweet-sensitive; Can a tooth under a crown still get a cavity? explains why.

Until you are seen

• Limit sweets, and especially sipping. Sugary drinks nursed over an hour keep the mouth acidic far longer than the same drink finished at a meal.
• Brush twice daily with a fluoride toothpaste, and consider a toothpaste labeled for sensitive teeth; these contain compounds that help block the transmission of sensation from the tooth surface to the nerve, usually need several applications before sensitivity is reduced, and do not treat the underlying cause.
• Avoid chewing on that side if the tooth also hurts to bite, to reduce the chance of a crack spreading.
• Rinse with water after sweet or acidic foods rather than brushing straight away.
• Pain relievers, if you choose to use them, only as directed on the label.

Do not assume that sensitivity which fades has resolved itself. Decay can continue to progress without symptoms, so the tooth still needs to be examined.

When emergency care comes first

Sweet sensitivity alone is rarely an emergency. The following are different, and they go to emergency medical care, not to an appointment request: difficulty breathing or swallowing, facial or neck swelling that is spreading quickly, fever together with facial swelling, uncontrolled bleeding, or severe trauma. Call 911 or go to the nearest emergency department. Facial swelling with tooth pain: when emergency medical care comes first explains the warning signs in more detail.

The next step

Note which tooth reacts, what sets it off, how long the pain lasts and whether biting hurts, and bring that record with you. You can request an appointment online (a request is not a confirmed appointment; the team follows up) or call (805) 565-5111 during office hours, Monday to Thursday, 8:00 am to 5:00 pm. If the tooth is aching constantly or the gum is swelling, say so when you call so the team can advise you on timing.