A filling repairs a tooth that has a cavity but a healthy nerve. A root canal treats a tooth whose nerve, called the pulp, has become infected or inflamed. Which one you need depends on how far the damage has reached, and your dentist can find out with an exam and an X-ray.
When a tooth starts to ache, it is natural to wonder whether you are facing a quick filling or something bigger. This guide compares root canal vs filling: how the two treatments differ and how a dentist decides between them. It is general education and cannot replace an exam.
Root Canal vs Filling at a Glance
Both treatments aim to save a damaged tooth instead of removing it. The difference is how deep the problem goes.
- A filling repairs a cavity. Your dentist removes the decayed tooth tissue and fills the space with a filling material, and the nerve inside the tooth is still healthy.
- A root canal treats damage inside the tooth. Your dentist removes the infected or injured pulp, cleans and disinfects the canals, then fills and seals them. The tooth is then restored with a permanent filling or a crown.
What a Filling Does
A cavity starts when bacteria in your mouth make acids that attack the tooth’s surface, called the enamel. The National Institute of Dental and Craniofacial Research explains that a filling is used to treat a small hole, or cavity, in a tooth: the dentist removes the decayed tooth tissue and then fills the space with a filling material. Fillings come in tooth-coloured (composite) and silver-coloured (amalgam) types, and the Canadian Dental Association describes both metal and tooth-coloured options, so ask your dentist which suits your tooth. Our guide to tooth-coloured dental fillings covers the natural-looking option in more detail.
When a Filling Is Usually Enough
A filling is the usual answer when decay is caught before it has done deeper harm. In early decay there are usually no symptoms, according to NIDCR, which is why decay can be found at a regular check-up with a visual exam and sometimes an X-ray. The CDA’s page on cavities says a small cavity that is not progressing quickly may simply be monitored, while a bigger one, or one that shows signs of progression, is best filled right away.
When a Root Canal Is the Better Choice
A root canal comes into the picture when the damage has reached the pulp, the soft tissue inside the tooth that holds its nerves and blood vessels. The American Dental Association’s MouthHealthy explains that pulp can become infected because of a deep cavity, repeated dental procedures on the tooth, a cracked or fractured tooth, or an injury. The CDA describes root canal treatment as removing infected, injured or dead pulp from a tooth, and for many patients it is the only viable way to keep a severely damaged or infected tooth.
Symptoms that mean a tooth needs attention include:
- A toothache, or sensitivity to sweets, hot, or cold, which NIDCR lists as symptoms of advancing decay
- Pain and swelling around the tooth, which the ADA says often appear when infection reaches the tissues around the root
- Facial swelling or a fever, which NIDCR connects with an abscess, a pocket of pus
Symptoms overlap, so pain alone does not tell you which treatment a tooth needs. Our guide to the signs you may need a root canal has more detail.
How to Tell If You Need a Root Canal or Just a Filling
You cannot tell from the outside, and your dentist will not guess from symptoms alone. Expect questions about when the pain started and what sets it off, a close look at the tooth and gum, and usually an X-ray. NIDCR notes that an X-ray can show decay, and the CDA says a dentist may notice an infection from an X-ray or other changes in the tooth.
What the exam finds usually settles the question:
- Decay that has not reached the pulp is normally treated with a filling.
- Pulp that is infected or damaged is treated with a root canal.
- A tooth too badly damaged to restore may mean talking about removing it instead. Our comparison of root canal vs tooth extraction explains how dentists weigh that choice.
Can a Filling Turn Into a Root Canal?
Having a filling does not mean you will need a root canal, but a tooth with a deep or aging filling can still need one later. The CDA says bacteria can enter a tooth through deep cavities, cracks or flawed fillings, and the ADA lists repeated dental procedures on the same tooth among the reasons pulp can become infected. MouthHealthy’s page on cavities also points out that over the years fillings can weaken, fracture and leak around the edges, and that bacteria collecting in those tiny crevices can lead to new decay.
That is one reason regular check-ups matter: your dentist can spot a failing filling before the decay underneath reaches the nerve. If you have already lost one, read what to do before you can see a dentist.
What to Expect During Each Treatment
For a filling, your dentist removes the decayed tissue and places the filling material, and will explain how they will keep you comfortable. A root canal has more steps. The ADA says it usually takes one or two office visits, with little to no pain because your dentist uses local anesthesia. Your dentist will:
- Take X-rays and place a thin rubber sheet over the tooth to keep it clean and dry
- Open the top of the tooth, remove the damaged pulp and clean each canal
- Fill and seal the canals, then place a temporary filling until the tooth is restored
The CDA says the tooth may be tender for the first week or two, but bad pain or swelling is not common, and you should call your dentist if it happens. A later visit replaces the temporary filling with a permanent filling or a crown.
What Happens If You Wait
Treating a cavity early gives you the simplest option. The CDA warns that a large cavity that is not filled can get bigger and cause pain, infection or tooth loss. The ADA adds that when an infection reaches the root, bacteria can damage the bone that keeps the tooth connected to your jaw, which puts the tooth at risk.
When to Get Urgent Help
Get help quickly if a sore tooth comes with any of the following:
- Swelling of the face, jaw, or neck
- A fever or feeling generally unwell
- Severe, throbbing pain that does not settle
- Difficulty chewing or swallowing
If you have trouble breathing or swallowing, or swelling that is spreading quickly, go to the nearest emergency department or call 911. For a tooth emergency, call our office at (905) 420-1777 and describe what is happening. Our team will explain what to do next, and you can read more about our emergency dental care.
Cost and Coverage
Costs depend on the tooth and the treatment, so ask for an estimate before treatment begins. If you are enrolled in the Canadian Dental Care Plan, confirm what applies to your situation with our office and the official program, because eligibility is decided by Service Canada. Our CDCP page explains how coverage works at our office.
Frequently Asked Questions
Which is more painful, a root canal or a filling?
A root canal has a reputation for being painful, but the ADA says there is little to no pain during treatment because your dentist uses local anesthesia, and that you should no longer feel the pain you had before once it is done. For a filling, your dentist will also explain how they will keep you comfortable. If anxiety is the worry, ask us about sedation dentistry.
Can I get a filling instead of a root canal if my tooth hurts?
Not if the pulp is infected. A filling repairs the tooth structure and does not remove infected pulp. The CDA states that if the pulp becomes infected, it needs to be removed. Your dentist will examine the tooth and tell you which treatment fits what they find.
Will I need a crown after a root canal?
Often, but not always. The ADA says the temporary filling is replaced with a permanent filling or a crown, and the CDA says the choice depends on the strength of the tooth that is left. The CDA adds that a back tooth will likely need a crown, because chewing puts a great deal of force on back teeth.
Can a root canal be done at my regular check-up?
Usually not at the same visit. The ADA says your dentist will schedule a follow-up appointment, or you may be referred to an endodontist, a dentist who specializes in the pulp and the tissues around the teeth.
How long do fillings and root-canal-treated teeth last?
NIDCR says dental fillings and crowns generally do not last a lifetime and may need to be replaced. The CDA says that with proper care and regular dental visits, a tooth that has had a root canal could last as long as your other teeth.
Not Sure Which One Your Tooth Needs?
If a tooth has been bothering you, please do not wait for it to settle on its own. Our team at Pickering Square Dental, on Kingston Rd in Pickering, can examine the tooth, explain what we find, and talk through your options. Learn more about our root canal therapy, or contact us to schedule an appointment.
This article is for educational purposes only and is not a substitute for personalized dental advice, diagnosis, or treatment. Always speak with a regulated dental professional about your specific concerns.
About Dr. Marvin Lean, DDS
Dr. Marvin Lean, DDS, is the owner and lead dentist at Pickering Square Dental. With decades of experience in family and laser dentistry, Dr. Lean provides care focused on clear communication and patient comfort. He is a member of the Ontario Dental Association (ODA) and the Canadian Dental Association (CDA). Dr. Lean and his team provide comprehensive dental care including sedation dentistry, dental implants, emergency dental care, and the Canadian Dental Care Plan (CDCP) to patients in Pickering, Ajax, Whitby, Scarborough, Oshawa, and Markham. Dr. Lean spent the last 20 years as the Dentist for the Toronto Maple Leafs.
