The signs that you may need a root canal typically come down to persistent tooth pain, sensitivity that lingers long after eating or drinking something hot or cold, and visible changes in your tooth or gums. No single symptom confirms it on its own, but certain combinations strongly suggest the nerve inside your tooth is infected or dying. Here’s what to look for and what happens when you visit a dentist to find out.
Pain Patterns That Point to a Root Canal
Not all toothaches mean you need a root canal, but the type of pain matters. A tooth with an infected or inflamed nerve tends to produce one or more of these patterns:
- Lingering sensitivity: A healthy tooth might feel a quick zing from ice cream, but the sensation fades in seconds. When the nerve is damaged, pain from hot or cold food hangs around for 30 seconds or longer after you remove the source.
- Sharp pain when biting down: If chewing on a specific tooth or even tapping your teeth together produces a sudden, sharp jolt, the tissue around the root is likely inflamed.
- A constant dull ache: Some people describe it as pressure that never fully goes away, centered in the same spot day after day. It can radiate into the jaw, ear, or temple on the same side.
- Pain that wakes you up at night: Nerve-related tooth pain often intensifies when you lie down because blood flow to your head increases, putting more pressure on the inflamed tissue.
Heat sensitivity is especially telling. A tooth that throbs in response to warm or hot drinks, and keeps throbbing afterward, is more likely to have a dying nerve than one that only reacts to cold.
Visual Signs You Can Spot Yourself
Sometimes the clues are visible before the pain gets severe. A tooth that has turned noticeably darker than its neighbors, shifting toward gray or brown, may have a nerve that has died. The discoloration happens because breakdown products from the dying tissue seep into the inner layer of the tooth.
Check your gums near the painful tooth. A small, pimple-like bump on the gum (dentists call it a fistula) is a drainage point for an abscess at the root tip. It may come and go, and you might notice a salty or unpleasant taste when it drains. Swelling that spreads into your cheek, jaw, or neck is a more advanced sign. If swelling makes it hard to breathe or swallow, that’s a dental emergency.
Tender or swollen lymph nodes under your jaw on the same side as the problem tooth can also signal that an infection has spread beyond the tooth itself.
What Happens at the Dentist’s Office
Your own symptoms give your dentist a starting point, but confirming the diagnosis requires a few in-office tests. None of them are complicated, and most take only a few minutes.
Thermal and Electric Tests
Your dentist will likely apply something cold, and sometimes heat, directly to the suspect tooth and its neighbors. They’re comparing how each tooth responds. A healthy nerve reacts briefly and then calms down. A compromised nerve either overreacts with lingering pain or doesn’t respond at all, which suggests the nerve has already died.
An electric pulp test works similarly. A small device delivers a mild, gradually increasing electrical stimulus to the tooth surface. A living nerve will signal a tingling sensation at some point. No response at all suggests the nerve tissue is no longer alive.
Percussion and Palpation
This is the simplest test: your dentist taps on the tooth with the handle of a dental instrument. A sharp, localized pain response points to inflammation around the root tip. They may also press on the gum tissue above the root to check for tenderness or swelling you can’t see in the mirror.
X-Rays
An X-ray shows what’s happening beneath the surface. Dentists look for a dark shadow at the tip of the tooth’s root, which indicates bone loss caused by infection. A healthy root tip blends into the surrounding bone with no visible dark area. The size and shape of the shadow, along with the results of the other tests, help confirm whether a root canal is the right treatment. Most infections that show up on dental X-rays stem from bacteria that have killed the nerve inside the tooth.
How to Tell if a Tooth Already Has a Root Canal
Some people searching this question want to know whether a tooth was treated in the past, especially if dental records are incomplete. A few clues can help.
A tooth that has had a root canal almost always has a crown or large filling on top, because so much tooth structure is removed during the procedure. If you run your tongue over the tooth and feel a full-coverage cap rather than natural enamel, that’s a strong hint. On an X-ray, a root-canal-treated tooth is easy to identify: the canals inside the roots appear as bright white lines, because they’ve been filled with a rubber-like material that shows up clearly on film. The tooth also won’t respond to cold or electric pulp testing, since the nerve was removed.
If you’re unsure, any dentist can confirm it with a single X-ray in a matter of seconds.
What a Root Canal Involves
If the diagnosis confirms you need one, the procedure is more routine than most people expect. Your dentist or an endodontist (a specialist in tooth nerves) numbs the area, creates a small opening in the top of the tooth, removes the infected or dead nerve tissue, cleans and shapes the hollow canals inside the roots, and fills them with a rubber-like material. A temporary filling seals the opening, and you return later for a permanent crown to protect the tooth long-term.
Most root canals are completed in one or two appointments, each lasting about 60 to 90 minutes. Molars take longer because they have more roots and canals to clean. The procedure itself feels similar to getting a deep filling. Soreness for a few days afterward is normal and usually manageable with over-the-counter pain relievers.
Cost by Tooth Type
Prices vary by location and insurance, but Delta Dental’s estimates give a useful ballpark. A front tooth root canal typically runs $620 to $1,100 without insurance. Premolars fall between $720 and $1,300, and molars cost $890 to $1,500. These figures generally cover all appointments and X-rays needed to complete the procedure. A crown, which most teeth need afterward, is an additional cost, often in a similar range. Dental insurance typically covers a significant portion of root canal treatment when the tooth is deemed restorable.