How do I know if I need a root canal?

Stanislav Moline
(You probably meant root canal treatment because root canal is a space within a tooth)

The answer is: when your dentist suggests and endodontist confirms it.

There are many situations in which a patiet may not have any discomfort, while examination finds the need for the treatment (example: asymptomatic infection). Sometimes, the treatment is needed for restorative purposes (example: there is not enough tooth structure to place a crown or the pulp containing the nerve is too close to decay for decay to be safely removed). 

There are, of course, situations when the tooth hurts all the time or for a prolonged time after eating, or pain just comes on its own. However, the treatment may not automatically require root canal treatment (a filling may be needed or desensitization can be performed). In some situations, the tooth may be too late to save.

Anyway, the best way is to check with your dentist and confirm with an endodontist.
Lucia Yau, DDS

If you have cold sensitivities that leads to pain and does not go away quickly; a "pimple" in the gum next to the tooth; or simply just a large "hole" in the tooth, etc.; all can indicate the need of root canal treatment. The best way to determine the course of treatment is to visit a dentist. The dentist can verify whether the cavity has progressed to the center of the tooth via x-ray and check the tooth in question carefully.

You may need a root canal if you have a severe toothache, usually along with swelling in your jaw around your tooth. When the pulp (the soft tissue inside the roots and center of a tooth) is damaged from a cracked tooth or other injury, or from a deep cavity, it can get infected. This can cause pain, swelling, and even an abscess in the bone around the tooth. To treat the damage, your dentist can do a root canal to remove the pulp from the tooth's roots and pulp chamber, treat any infection, and fill the tooth. You will then need a crown over the repaired tooth.
Steven M. Katz, MD

Signs of the need for root canal therapy include pain, prolonged sensitivity to heat or cold, tenderness to touch or chewing, discoloration of the tooth and/or swelling or tenderness in the gum area. Sometimes, however, there are no symptoms at all.

You may or may not be able to know if you need root canal treatment (RCT) because not every case will produce symptoms. It is best to go to your dentist regularly for prevention and early detection so that a more simple procedure can be performed and avoid the need for RCT. The most common symptom that usually needs RCT is sharp shooting pain that keeps you up at night. Now, wouldn't you want to avoid that!
In determining the need for a root canal, clinical symptoms, pulp testing, and x-rays may be used to determine if a tooth needs a root canal. Symptoms may include pain on biting, swelling, and a bump on your gum. Sometimes x-rays will show an abscess in a tooth that has no clinical symptoms.
Root canals are indicated in teeth that are usually infected due to different causes such as large cavities, fractured teeth or in some instances when very little tooth structure is left and in order to rebuild the tooth you have to place a post inside of it, and then restore the tooth. To find out for sure if a tooth needs root canal you need to see a dentist and have exam and x-ray done to find out if this tooth is a good candidate for root canal treatment.
In all honesty, you’ll almost always know that “something” is wrong -- in most cases where a root canal may be necessary, the area will hurt. But in the end, your dentist will tell you whether you need a root canal or not. Sometimes, a large filling will handle the issue, and other times, an extraction might be the best course of action. Your dentist will examine you, make his or her best recommendation, and present you with options for treatment, one of which may be a root canal. 
Is the pulp (soft tissue inside your teeth containing blood vessels, nerves and connective tissue) inflamed or diseased? If so, you may need a root canal to save the tooth.

A root canal removes the diseased pulp. The pulp chamber and root canal(s) of the tooth are then cleaned and sealed. 
Root canal treatment or endodontic therapy is often the indicated treatment when someone has a toothache. The symptoms are spontaneous pain, lasting sensitivity to cold which is then relieved by heat in the earlier stage of pulpal deterioration and lasting sensitivity to heat which is relieved by cold in later stages of pulpal degeneration. As the pulp ("nerve area") dies an abscess may form which creates pain on biting and touch, tenderness to palpating tissue near the involved tooth and possibly swelling. This is due to the infection at the tip of the tooth.

Obviously it is best to avoid dental emergencies by taking good care of your teeth and scheduling regular dental visits and examinations by your dentist. Often there may be evidence on radiographs (x-rays) of a chronic infection at the tip of the tooth or decay which is either into the pulp or very near it. Both of these conditions are indications for root canal treatment prior to an emergency. DON'T WAIT TILL IT HURTS.

Also, there are situations when a tooth has an extensive large filling and requires a crown. In this case it may be indicated to electively have the endo treatment performed prior to the crown services.

Unfortunately, there are times when you have the symptoms indicating the need for endodontic treatment, but the tooth is so broken down that it is not fixable. In this situation extraction is the only solution to the problem.
Your Dentist needs to find out why your tooth is painful before a root canal is done. Not all sensitive teeth require root canal therapy. A diagnosis is made by testing the tooth- checking to see if the tooth nerve is alive by using a cold spray (this is called a pulp test). A radiograph of the tooth and the bone surrounding the tooth will be taken to see if there is an infection. Your Dentist may tap on the tooth, or have you bite on something to see if it is painful. 

If the nerve on the tooth is not alive, or an abscessed area on the radiograph is found, there is a good chance you will need to have root canal therapy. The goal of this therapy is to remove the dead nerve and treat the infection in the bone. Typically a patient with an abscess will wake up and night with pain- also will have pain for no apparent reason (achy, throbbing).

If the nerve is found to be alive, but extremely painful- reacting in an irregular way to normal stimuli, you may also need root canal therapy. For example, if you have ice cream and the tooth hurts you for 20 minutes, and aches -- and you need to reach for Advil -- that is abnormal. The diagnosis may be "irreversible pulpitis”, and only root canal therapy will relieve your pain. 

Sometimes there is a fracture in the tooth. Typically the patient cannot bite on the tooth. Many times we cannot find them and an Endodontist needs to look with a microscope. These teeth have the worst outcome if the fracture is in a root. Unfortunately, some need to be extracted. 

In most cases, after a successful root canal therapy, the tooth will require some sort of a full coverage restoration -- like a crown or an onlay. Left on its own, without being restored, the tooth is subject to fracture and reinfection. 
The most common symptoms are pain to hot and cold liquids. When you bite on the tooth and it elicits discomfort. Sometimes mild sensitivity is a symptom, although it may be from other causes such as recession or hard tooth brushing that removes enamel.

There are instances where there are no symptoms but your dentist sees infection on the x-ray. 

Only a dentist can tell you if you indeed require root canal therapy based on your symptoms and x-rays.
The best way to find out if you need root canal treatment or not is to consult an endodontist (also known as a root canal specialist). A tooth that needs root canal treatment might or might not have any symptoms at all.

If the tooth is symptomatic, usually you will feel lingering pain to cold, hot and/or sweet, spontaneous pain, swelling in the area, throbbing pain, pressure pain and more.

Examples where your tooth might need root canal treatment but does not hurt at all include:
  • chronic infection with a cyst at the root tip
  • internal resorption (an inflammatory process that, if not stopped immediately, can lead to tooth loss)
  • a severely broken tooth that requires a post and a crown
Again, the best way to find out if a tooth is in need of root canal treatment is to consult your dentist or a root canal specialist. 

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.