When a Tooth Hurts

The cause of tooth pain depends on when and how it hurts. Is it a sharp pain only when biting? A throb even at rest? Brief sensitivity to cold? Worse at night? Just noting these four things before you come in makes diagnosis much faster. Boston Miso Dental Clinic in Uijeongbu doesn't decide on treatment from symptoms alone — we confirm the cause with X-rays, 3D CT (CBCT), and Qray exams, then look first at options that preserve more tooth and avoid extraction.

At a glance — throbbing toothache: causes, and how the dentist examines and treats it

Short answer: Most toothaches come from one of five causes: a deep cavity, nerve (pulp) inflammation, inflammation at the root tip, a cracked tooth, or gum inflammation. At the clinic, we narrow down the problem tooth with X-rays and cold, tapping, and biting tests, add 3D CT and Qray fluorescence screening if needed, and then treat the cause. If it throbs even at rest or hurts more at night, we suspect nerve inflammation first.

The table groups common patterns, but symptoms often overlap, so the cause is confirmed by examination. Each cause is explained in detail below.

When a tooth hurts, what are the common causes?

There are five common causes.

• A deepening cavity — If sensitivity to sweets or cold gradually turns into longer-lasting pain, the cavity has likely progressed close to the nerve. Early on, cavity treatment is enough, but putting it off can mean root canal treatment.
• Nerve (pulp) inflammation — If it throbs even at rest, worsens at night, and reacts to hot things, we suspect nerve inflammation. Even at this stage, the tooth is often saved with root canal treatment rather than extraction.
• Inflammation at the root tip (periapical abscess) — An ache when you bite, along with gum swelling or pus, means inflammation has collected at the root tip. It shows up as a dark shadow on X-rays.
• A cracked tooth — Typical signs are a sharp pain only when biting on a specific spot, and pain when you release the bite. Cracks are hard to see on X-rays, so we look for them with Qray and bite tests.
• Gum inflammation — The gums, rather than the tooth itself, swell, bleed, and ache dully. This calls for gum treatment (periodontal treatment).

If it's swelling and pain around a wisdom tooth, the cause is different — see When a Wisdom Tooth Swells and Hurts.

What should I check at home first?

1. How it hurts — Only when biting / only with cold / even at rest / worse at night. This roughly follows the order "crack or early cavity → deep cavity → nerve inflammation," though they often overlap.
2. How long it lasts — Does it stop as soon as the trigger is gone, or linger for 10 seconds or more? The longer it lasts, the more likely it's nerve inflammation — though only an exam can confirm it.
3. Gum condition — Is the gum around that tooth swollen, and does pressing it produce discharge?
4. Recent treatment — If the tooth recently had a crown or resin filling, the pain may simply be from the bite being too high.

Even if painkillers ease it for a while, the underlying cause remains. In particular, if it hurt for several days and then suddenly stopped, that may not mean it has healed — the nerve may have died, which is all the more reason to get it checked.

What does the dentist check?

We use X-rays to check the depth of the cavity and any inflammation at the root tip, and 3D CT if needed to see between the roots and inside the bone. Qray fluorescence screening is a supplementary exam that reveals early cavities and surface cracks X-rays can miss — cracks below the gumline or deep cracks may not show up under fluorescence either, so a suspected cracked tooth is assessed together with biting and occlusion tests. Cold, tapping, and biting tests then narrow down which tooth is the source. We go through the results with you on screen.

How does the treatment approach differ by cause?

• Cavity → Resin filling or inlay, depending on depth. If it has reached the nerve, root canal treatment followed by a crown.
• Nerve inflammation or root-tip inflammation → Our aim is to save the tooth with root canal treatment. We even have a case where a molar that had kept a patient up at night was saved without extraction.
• Cracked tooth → The depth of the crack is what matters. If it extends into the root, extraction is unavoidable, but before that point, capping it with a crown can stop it from progressing.
• Gum inflammation → A cleaning (scaling) or subgingival tartar removal.

If you've been told a tooth needs to come out, we recommend reading Four Things to Check Before Extraction first.

Don't put it off in these cases

• Your face or gums are noticeably swollen — the inflammation is spreading.
• It hurts badly enough to wake you at night — nerve inflammation has already progressed.
• Only one specific tooth stings when you bite — it needs to be checked before the crack widens further.

We have evening hours until 21:00 on Thursdays, so pain that gets worse in the evening can be checked the same day.

Related Treatments & Cases

• Cavity Treatment
• Gum Treatment
• A molar with inflammation between the roots, saved with root canal treatment instead of extraction
• A loose tooth with pus from the gum, saved with root canal retreatment
• A crown that kept coming off — rethinking the cause from scratch
• Symptom Checker
• Fees

FAQ

Painkillers make it feel better — do I really need to come in?

Painkillers only mask the pain. The cavity and inflammation keep progressing in the meantime, and treatment that could have ended with a simple resin filling early on can grow into root canal treatment and a crown. If the pain keeps recurring, we recommend having the cause checked.

A tooth that was hurting suddenly stopped hurting. Is it healed?

Often the nerve has died and the sensation has simply disappeared. It tends to return later as swelling from inflammation collecting at the root tip, or as an ache when you bite. Even if the pain is gone, it still needs to be checked.

I can't tell which tooth is hurting.

That's common. Nerve pain can radiate and feel like it's coming from the teeth above, below, or beside the affected one. Cold, tapping, and biting tests along with an X-ray help us narrow down the source.

References

The order of evaluation and treatment approach described here are Boston Miso Dental Clinic's own standard; the causes, mechanisms and treatment effects are based on the references below.

※ This guide is general information. Even with the same symptom, the cause and the right treatment vary with your oral health. Dr. Lee, the Clinic Director, explains your diagnosis in person after an exam. Any dental treatment can cause side effects such as pain, bleeding, or infection, which vary from person to person.

The clinician responsible for treatment guidance at Boston Miso Dental Clinic is Dr. Jongbum Lee, Clinic Director, a board-certified specialist in Advanced General Dentistry (Korea).