An infected tooth usually announces itself with a severe, constant, throbbing pain that doesn’t go away on its own. But not every infection starts dramatically. Some build slowly over weeks, beginning as mild sensitivity before escalating into something harder to ignore. Knowing the specific signs helps you catch an infection early, before it spreads beyond the tooth.
The Most Common Signs
The hallmark symptom is a deep, throbbing toothache that persists even when you’re not eating or drinking. Unlike a cavity that stings when sugar hits it, an infected tooth often hurts constantly, with the pain radiating into your jawbone, neck, or ear. This referred pain can be confusing. Some people initially think they have an ear infection or jaw problem when the source is actually a tooth.
Other signs to watch for:
- Sensitivity to temperature: Pain or discomfort when you drink something hot or cold, especially if the sensation lingers for more than a few seconds after the stimulus is gone.
- Pain when biting or chewing: Pressure on the tooth sends a sharp jolt, and even lightly tapping it with your finger may hurt.
- Swelling: Your face, cheek, or neck may visibly swell on the side of the affected tooth. In some cases, the gum near the tooth develops a small pimple-like bump (sometimes called a gum boil) that may ooze pus.
- Swollen lymph nodes: Tender lumps under your jaw or along your neck, a sign your immune system is actively fighting the infection.
- Bad taste or smell: A foul odor in your mouth or a sudden rush of salty, bad-tasting fluid. If pus drains on its own, you may actually feel temporary pain relief, but the infection is still there.
How a Tooth Infection Develops
Infections start when bacteria breach the outer layers of your tooth and reach the soft tissue inside, called the pulp. This usually happens through an untreated cavity, a crack, or a chip. Once bacteria enter the pulp, they cause inflammation. In the early stage, known as reversible pulpitis, the tooth can still recover if a dentist repairs and seals it promptly.
Left alone, the inflammation worsens into irreversible pulpitis, where the damage is too far gone for the tooth to heal on its own. Eventually the pulp tissue dies entirely. At that point the infection doesn’t stop. It tracks down through the root canal and into the jawbone, forming a pocket of pus called an abscess. This is also why partially erupted wisdom teeth are prone to infection: bacteria get trapped between the crown of the tooth and the surrounding gum tissue, with no easy way out.
The bacteria involved aren’t a single type. Dental abscesses are polymicrobial, meaning multiple species work together. The mix typically includes several types of anaerobic bacteria (organisms that thrive without oxygen) alongside streptococcal species that are normal residents of your mouth. This combination is part of what makes dental infections aggressive once they take hold.
Infections That Don’t Hurt (Yet)
One of the trickier aspects of tooth infections is that some progress silently. A tooth with a dead nerve may not produce the sharp pain you’d expect because the tissue responsible for sensing pain has already died. You might notice only a dull ache, slight discoloration of the tooth, or a persistent bad taste. In some cases, the only visible clue is a small draining bump on the gum that comes and goes.
This is one reason routine dental X-rays matter. An infection at the root tip shows up on an X-ray as a dark shadow, a sign of bone loss around the root. Dentists look for this radiolucency along with signs of root damage and loss of the thin white line (lamina dura) that normally outlines a healthy root. These changes can be visible on imaging long before you feel significant pain.
How a Dentist Confirms the Infection
If you go in suspecting an infection, the exam is straightforward. Your dentist will tap on the tooth and the ones next to it. An infected tooth is typically sensitive to touch or pressure, and this test helps pinpoint which tooth is the problem, since referred pain can make it hard to tell on your own.
An X-ray is the next step. It reveals whether an abscess has formed at the root tip and how far the infection has spread into the surrounding bone. If there’s concern that the infection has moved beyond the jaw into the neck or deeper tissues, a CT scan provides a more detailed picture of the extent.
Your dentist may also test the tooth’s response to cold or electrical stimulation. A tooth that doesn’t respond at all likely has dead pulp tissue, confirming that the infection has progressed past the reversible stage.
What Treatment Looks Like
The goal of treatment is to eliminate the infection and, when possible, save the tooth. A root canal is the most common approach for this. The dentist removes the infected pulp, cleans and disinfects the inside of the tooth, then fills and seals it. First-time root canals have a success rate of about 86%, making them a reliable option for most infected teeth. If a previous root canal fails, a retreatment procedure still succeeds about 78% of the time.
If the tooth is too damaged to save, extraction is the alternative. In either case, if there’s an abscess, your dentist may need to drain it first to relieve pressure and clear the pus. Antibiotics are sometimes prescribed alongside the procedure, particularly if the infection has spread beyond the tooth itself or if you have a weakened immune system.
What you can expect afterward: pain from the infection typically drops significantly within a day or two of treatment. A root canal tooth will need a crown to protect it long-term, usually placed a few weeks later.
Signs the Infection Is Spreading
A tooth infection that stays localized is painful but manageable with prompt treatment. The danger comes when it spreads. Swelling that extends into your neck, difficulty breathing or swallowing, fever, or a general feeling of being unwell are all signs the infection is moving beyond the tooth. Facial swelling that causes one eye to start closing or makes it hard to open your mouth fully signals a serious escalation.
Dental infections can spread into the deep spaces of the neck and, in rare cases, reach the chest cavity or bloodstream. These complications are the reason a tooth infection that involves facial or neck swelling, high fever, or trouble breathing warrants an emergency room visit rather than waiting for a dental appointment.