Updated on: 24 September 2026
Has that 'zing' in your tooth that hits you with a cold drink turned into a dull and persistent ache? It's probably time to have your dentist take a look, especially if it's keeping you from your normal daily activities. It may indicate a tooth infection and the need for a root canal. The most common signs are:
- Ongoing tooth pain
- Sensitivity to hot or cold that lingers
- Swollen gums or a pimple on the gum
- Pain when chewing
Here's what each one means and when to see your dentist.
The Signs and Symptoms of a Tooth Infection
Here are four telltale signs that your tooth is infected and needs root canal treatment in Dunedin:
1. Persistent and Deep Tooth Pain
If you've ever experienced a severe and constant toothache, you know that it's difficult to focus on anything else.
Don't ignore this pain, waiting for it to go away on its own. A tooth infection will not resolve without treatment from your dentist, and it could spread to other teeth and other critical areas of your body if it's left untreated.
2. Lingering Sensitivity to Hot and Cold
Tooth sensitivity to temperature or sweets may indicate a tooth infection, especially when it lingers and persists.
If you experience tooth sensitivity to temperature that goes away on its own, this is actually a good time to visit your dentist. With an exam, your dentist may be able to spot tooth decay and treat it before it becomes a more significant problem, such as a tooth infection.
3. Gum Swelling, Pimple on the Gums or Tooth Discolouration
Swollen gums or a white blister or pimple on the gums surrounding your compromised tooth may indicate an infection. If your tooth appears dark or discoloured, it may also be infected.
Don't wait to treat the blister or pimple on your own; contact your emergency dentist in Dunedin right away for prompt treatment.
4. Pain When Chewing or Applying Pressure
Consistent pain or an ache when you chew and eat food is also an indicator of an infected tooth.
What Causes a Tooth to Need a Root Canal?
A root canal is needed when bacteria reach the pulp inside the tooth. Common causes include:
- Deep decay that has worked through the enamel and dentine
- Cracked or chipped teeth that let bacteria in
- A knock or injury to the tooth, even one that happened years ago
- Repeated fillings or dental work on the same tooth
Can You Need a Root Canal Without Any Pain?
Yes. Sometimes the nerve inside a tooth dies quietly, and the only clue is discolouration or an issue spotted on an x-ray. This is one reason regular check-ups matter, even when your teeth feel fine.
How Does a Dentist Confirm You Need a Root Canal?
Your dentist will ask about your symptoms, examine the tooth and gums, and take x-rays to look at the roots and surrounding bone. They may also gently test how the tooth responds to temperature or pressure. Together, these help show whether the pulp is healthy, inflamed or infected.
What Happens Next?
If an infection is confirmed, root canal treatment can clear it and save your natural tooth. To learn about the procedure, recovery and costs, read our guide to what to expect during root canal treatment.
Talk to Our Dunedin Dental Team
We invite you to talk to our team on (03) 477 8387 for prompt emergency dental care if you or a loved one is experiencing any of these symptoms.