Know Before You Go: Root Canals

Updated on


Hi, I’m Dr. B, practicing functional dentist for 35 years. I graduated from the Dugoni School of Dentistry in San Francisco, CA in 1987 and am a member of the American Academy of Dental Sleep Medicine (AADSM), Academy of General Dentistry (Chicago, IL), American Academy for Oral Systemic Health (AAOSH), and Dental Board of California. I'm on a mission to empower people everywhere with the same evidence-based, easy-to-understand dental health advice that my patients get. Learn more about Dr. B

If you’ve been told you need a root canal or are scheduled for one soon, you’re in the right place. This is your guide to everything you should know before getting a root canal as well as what to expect during the procedure.

By the end of this post, you’ll know:

  • Exactly what questions to ask your dentist
  • What to expect during the procedure
  • What to expect in terms of pain
  • How to not get ripped off
  • Everything that should be discussed with your dentist before you agree to a root canal

What Is a Root Canal?

root canals

A root canal is a procedure to preserve (not save) a dead tooth.

I say “preserve” and not “save” because it’s like mummification. It’s taking a dead pharaoh and stuffing him — it’s not saving the pharaoh’s life.

By the time you need a root canal, it’s too late to save the life of the tooth because it’s already infected and dying.

Why mummify a dead tooth? You do this because you want to keep the tooth in your mouth. It’s a dead tooth that’s mummified.

Why not pull the dead tooth out? Well, you can, and then you would have to replace the dead tooth with an implant to fill the hole left behind in your jaw along with a new, artificial tooth—and actually, the new school of thought is that going straight to an implant is the right thing to do.

The main reason for getting a root canal instead of an implant is that it’s simpler to keep your old tooth, even though it’s dead, because you can still benefit from having the structure of the dead tooth to chew food and help you speak properly.

Ever seen a movie where someone’s leg gets infected and it has to be cut off? A root canal is like that —you have to cut out the infected tissue inside the tooth to prevent infecting the rest of your body and killing you.

But there are consequences.

Having a root canal done makes the tooth brittle and prone to fracture — think of the mummified pharaoh. The inside of the tooth has been scraped out, leaving the outer shell of the tooth dry, brittle, and prone to breakage.

That’s why a root canal procedure requires a second procedure shortly afterwards: A crown.

A root canaled tooth needs protection because you’ve carved out the tissue inside it.

Enter: the crown, which is a rigid covering that is stronger than enamel that preserves the structural integrity of the tooth and prevents it from breaking.

tooth anatomy

What Are the Pros and Cons of a Root Canal?

Root Canal Pros:

  • You don’t have to extract the tooth.
  • You can keep the tooth.
  • You don’t lose the bone around the tooth.

Root Canal Cons:

  • There’s no such thing as a 100% clean root canal.
  • It can be hard to sit with your mouth open for a few hours during the procedure.

What Is the Procedure Like?

Here’s a great visual of what a root canal is, except for just two things: I don’t recommend or do posts, as they crack the teeth. The method shown for sealing the tooth is an older method called lateral condensation. There are newer and better methods used today for sealing.

You’ll sit in the chair for a few hours with your mouth open the entire time — this part is tough for most people. Load up your phone with a great audiobook or an addicting podcast to distract yourself.

During the procedure, your dentist will remove the inflamed or infected pulp, carefully cleaning out and shaping the inside of the tooth, and then filling and sealing the space so it’s closed off to infection.

After that, you’ll need to come back to the dentist to get a crown placed on the tooth to protect it so that you can once again chew on it and use it like the rest of your teeth.

After that, your tooth will function just like any other tooth would — you’ll be able to bite on it, chew on it and use it normally.

What to Ask Before Agreeing to Treatment

  • Is a root canal absolutely necessary?
  • Is it possible the tooth will recover and not need the root canal?
  • Why did the pulp die?
  • What are my options?
  • What if I don’t do the root canal?
  • Should I skip the root canal and go right to the implant?
  • Will my infection spread to other teeth or to my bone?
  • How predictable is the treatment?
  • And perhaps most important: Should I have this done by specialist or can you do as good of a job as a specialist can?

How Does My Dentist Know I Need a Root Canal?

For other conditions, a doctor can give you a blood test and the results will come back either positive or negative. It’s not so cut and dried with root canals.

Diagnosing whether you need a root canal does have a scientific basis but it can be a bit of an art form to find out how diseased the pulp of the tooth is.

This is why you really need someone who is experienced. A practitioner who rushes this process could choose the wrong treatment of the tooth.

To diagnose whether or not you need a root canal, your dentist will need to determine if the pulp inside the tooth is dead or dying or if it’s possible that the pulp could recover.

Data Points Your Dentist Uses to Decide If You Need a Root Canal

Lingering pain: Your dentist will ask you about how your tooth responds to hot and cold. When you drink cold water, does your tooth get sensitive? How long does the pain last? This is a way of figuring out if you have “lingering” or “non-lingering” pain. “Lingering” means the pain sticks around. Non-lingering pain goes away. If the pain goes away, the pulp inside your tooth might be alive enough to recover from the hot and cold, indicating that the tissue could potentially recover. If you drink cold water and you’re sensitive for the next hour or more, that’s “lingering” pulpitis (infection of the pulp) which means your tooth isn’t recovering and the nerve is likely dead.

Positional pain: Does your pain get worse when you lie down or stand up suddenly or run in place? This can be the sign of an abscess and, likely, a dead tooth.

Spontaneous pain: If pain is brought on by a stimulus like a hot or cold drink, it’s possible that the pulpitis is reversible, but if you’re sitting there doing nothing and get a wave of pain, that’s probably a dead tooth.

Fistula on the gum: A fistula is a little white, yellow, or red pimple-looking thing that shows up your gum. What this tells your dentist is that there is an infection because there is pus, blood, and infectious materials trying to get out and the body is trying to vent it. The problem is that it doesn’t always go alongside the tooth that is infected — a fistula can mislead the dentist as to which tooth it is.

Abscess: An abscess is typically seen on an x-ray. It is essentially a hole in the jawbone that shows up as a dark spot on the x-ray because the bone doesn’t want to grow in that area. Bone won’t grow in the area around an infection and an infection typically comes from the tip of the root, which is where everything is spilling out from the dead tissue inside of the tooth.

Referred pain: I weigh this one heavily. If the pain is not only in your tooth but also referring to another part of the body, like your jaw, ear, or surrounding teeth, this could mean you have an abscess. What I try to do is ask my patients in such a way that they don’t know what I’m asking so that I get the right answer.

How Long Can I Wait Before I Get My Root Canal Done?

Once you find out you need a root canal, it’s like a ticking time bomb, because the infection will eventually blow up. You’ll get more pressure and more swelling if you wait. You might get a bad taste in your mouth or might start to go numb. The infection could spread to more vulnerable tissues, like your heart. This is why people used to die of tooth infections hundreds of years ago.

Your dentist will prescribe you antibiotics for the infection. Once you start taking antibiotics, you’ve bought yourself four or five weeks. If you get on the antibiotics before the root canal is done, you’ll have less pain during the procedure because this will make it easier to get you numb.

As soon as you find out you need a root canal, you need antibiotics right away. Don’t delay! It could turn into a life-threatening condition if you don’t. Yes, a tooth infection can kill you!

Should I Get a Root Canal Or an Implant?

A big question now in dentistry is: do you go right to the implant because it’s more predictable than a root canal?

To make this decision, you need to ask your dentist about the predictability of success of a root canal. This is something that you and your dentist have to decide together, after you consider all the options for your unique case.

If you talk to an endodontist, she will want to do the root canal.

If you talk to the oral surgeon, he will want to do the implant.

All healthcare professionals tend to recommend things that we know more about and are more skilled in or comfortable with. Always keep in mind this inherent bias, and don’t be afraid to ask for a second opinion.

Root Canals Are Never “100% Clean”

accessory canals

Essentially, the concept of a root canal is this: inside of this enclosed space inside the tooth, there’s a lot of infected tissue with bad bugs. It’s up to the dentist to go in and remove 100% of that infected tissue.

The cartoon above is simplified to show just one canal, but in real life, a root has several canals that all twist and turn, making it impossible to remove perfectly 100% of this infected tissue.

After the infected tissue is removed, your dentist has to seal it off to make sure no bacteria can get back in there. There is no way to make a perfect seal because there are so many accessory canals, which are canals running off the main canal. (Imagine a vein in a leaf, with lots of little “accessory” veins running off of the main vein.)

I’ve had very few root canals fail in my nearly thirty years of dentistry. Even though we’re trained to scrape out the infected tissue once, I do it three times, but I’m maniacal about the details and getting every last little bit of tissue.

Given these two points, they say a root canal is 95% effective, which I would say is optimistic.

People that are proponents of implants see this as a con for root canals because, with an implant, you’ve removed the source of the infection completely — there are no sealing or removal issues and you’re placing something sterile into the jawbone.

This is why, if you decide to get a root canal, it’s essential your dentist is very skilled, because the procedure is so technique-sensitive, and that your dentist has assessed there’s a good chance of success of the root canal.

You want someone who’s a perfectionist.

I have an all-or-none philosophy when it comes to root canals; either you get everything and you really clean it out, or don’t bother and go with the implant.

A Word on DUI (Deciding Under the Influence)

A lot of the time, people are in a lot of pain when they have to make the decision about whether to get a root canal.

When you’re in pain and you’re desperate, I call this making decisions under the influence of pain. You’ll do anything to get rid of that pain.

Here’s where it’s important to still be wary. Make sure your dentist has your best interest at heart and is helping you make the right decision, instead of taking advantage of the state of pain you’re in.

During the Appointment

root canal rubber dam

During the appointment, your dentist will give you deep full local anesthesia, which is a little more than required for a filling because your dentist is removing the nerve.

Many x-rays will be taken to make sure that the instruments are in the correct location to remove the infected tissue.

Your dentist may place a sheet of latex, called a rubber dam, over your mouth, so that when the tooth is opened, no bacteria from the mouth can get in and when medications are used inside of the tooth, you don’t have an opportunity to swallow them.

The rubber dam essentially isolates the tooth from the oral environment and in some cases helps the dentist do the root canal.

The procedure should take longer than your standard filling. Expect to get very numb with local anesthesia.

Bring a book on tape or a long podcast you can listen to in order to pass the time.

One Appointment vs. Several

Some dentists will do a root canal all in one visit. Others will take two or three visits to do it.

Neither is better than the other — again, there are differing opinions on this. Some dentists wait and let the tooth dry and empty for a little bit and disinfect a second time then fill it.

I do all of my root canals in two visits because I think this is the best way to be as thorough as possible.

It’s more profitable to do a root canal in one visit. Doing a root canal in one visit might also be considered a service to you as the patient since it might be more convenient. But my recommendation is, be willing to take your time.

Don’t rush it or try to speed things up because it is such a technique-sensitive procedure.

What to Expect During the Appointment

You shouldn’t have any pain. If the dentist is skilled at delivering the local anesthesia, you won’t feel a thing.

Sometimes, a dentist will begin the root canal and things go wrong—this can be a good thing!

If your dentist gets inside the tooth and is presented with new information that changes the chances of success of a root canal, he will stop to tell you so you have the choice to abort the procedure before proceeding with a root canal that has lower chances of success than you both originally thought.

Reasons to Abort a Root Canal

A separated instrument: This is when an instrument breaks off inside the tooth.

A calcified canal: This is a canal that can’t be filled because you can’t get inside it. If the canal cannot be negotiated due to a calcification (this is actually the tooth trying to do its own root canal) then that means the canal cannot be properly filled, hence the prognosis of the root canaled tooth drops.

A fracture: Once the tooth is opened, your dentist might see a fracture which is not visible on the x-ray typically. A fracture makes a tooth have a poor prognosis even if your dentist does the perfect root canal because seepage can occur at the fracture line, which can lead to bone loss. If you lose bone around the tooth, you lose the support of the tooth. What I always tell patients in this situation is this: Don’t remodel the kitchen if you have dry rot in the floor! Abort the procedure in this case and go for an implant.

A curved root: Also called “complex canal morphology.” Canals bend and turn. Your dentist should only do the root canal if she knows she’ll be able to negotiate to the tip of the canal. If there is complex root canal anatomy — lots of twists and turns that are hard to navigate — then the chance of success of the root canal goes down.

Your dentist should only do the root canal if conditions are ideal.

You can drive home if you got just local anesthesia. If you got knocked out, you’ll need to be driven home.

What to Ask Afterwards

After the procedure, ask your dentist:

  • How difficult was it?
  • Was it easy to negotiate the canals?

Your dentist is required to tell you if anything went wrong during the procedure. Sometimes instruments will break off inside the canal — this is called a separated instrument (see above) — and your dentist is required to tell you about it. If your dentist doesn’t, the tooth will later become re-infected because you can’t seal past the separated instrument.

What to Expect After You Go Home

You shouldn’t bite or chew on the treated tooth until you have had it restored with a crown by your dentist. A root canaled tooth is prone to fracture, so you’ll need to get the crown as soon as possible.

Until you’re able to come in to get the crown done, practice good oral hygiene and brush and floss normally.

Avoid biting on the tooth or chewing food on it.

Pain After a Root Canal

You might expect some pain, but don’t be surprised if there is no pain. No pain can happen and is not unusual.

If you do have pain, it usually peaks 17 to 24 hours after the procedure and it’s best to keep your head elevated while sleeping for the first one or two nights. If need be, take whatever pain medication that your dentist recommends.


Feeling soreness after a root canal is unusual, but it happens often enough to discuss.

Your tooth can be sore and tender, but not necessarily painful, but sore and tender to percussion and chewing for up to six months, even after you’ve gotten the crown.

The concept or theory here is that the infection was so great inside of the tooth that it affected the surrounding areas in the jaw bone and that the body has to fix those areas and that takes time.

Getting the Crown

The sooner the better, because the tooth could cracker if you bite down on something hard.

Once the root canal is done and pain has subsided, it’s wise to cover the tooth with a crown right away because a root canaled tooth has weakened and dried out.

Covering the cored out tooth with a crown gives it virtually no chance of fracturing.

Some people wait to do the crown so that they don’t max out their insurance, but this can be a dangerous game.

If the tooth breaks, you may lose your investment of the root canal and have to go to the implant and crown.

Be delicate with your tooth until you get crown and stay off of it.



My root canal was done a month ago and I still have pain. What does that mean?

A: The sensation of hot and cold typically goes away once you do root canal because the pulp is no longer in the tooth, but sometimes the root canaled tooth can be tender to percussion or chewing and it can still sometimes have positional pain. This can mean one of two things: It’s most likely normal post-surgery pain, which takes time to go away. The pain could also mean that your dentist missed a canal and didn’t fill it. Stay in communication with your dentist about the pain to decide the right course of action.

Do root canals cause cancer?

A: Many of you may have read that root canals can cause cancer by infecting the blood. The science on this is correlative, not causative, and the mechanism used to make this connection is based on methods and technologies from the 1950s. Root canal methods and materials have evolved many times over since those times and have been completely different since the 1970s. That said, a poorly done root canal can and will have effects on the health of the rest of the body.

There is a 20% chance that the blood will be infected from bugs from the tooth during the root canal procedure, which is well-documented in the medical and dental literature. It is transient, meaning it lasts for around 20 minutes and a normal, healthy body can effectively deal with it. This can also happen when you pull a tooth or even cut your skin.

This transient, i.e. temporary, infection isn’t the thing to worry about because it happens in normal life all the time and the immune system is prepared to deal with it. It is the long-term infection of the blood from a leaky root canal that was not properly sealed that is the problem.

So, how do you know if your root canal is safe, i.e. properly sealed? My tips: Have a periapical (not bitewing) x-ray taken of the tooth every three years and have a an endodontist or dentist check it for bone loss or signs of local infection, which would indicate that the root canal is not doing well. At home, every six months, take the back end of a fork or spoon and tap on the root canaled tooth. If it’s tender and sore, compared to tapping on other healthy teeth, then that may be a sign that the root canal is failing and needs to be retreated. The good news is that they are beginning to genetically tag bacteria in the blood, so they’re able to trace specific bacteria back to the origin, the root canal. This technology will soon be available publicly in the form of a blood test.


How often do I come back for a follow-up?

A: Initially, you should get a follow-up within six months and after that every five years to make sure the root canal is doing what it’s supposed to be doing, which is preventing any reinfection inside of the tooth.

Why did my dentist not use a rubber dam for me but did use one on my husband?

A: There is currently a controversy in dentistry whether rubber dam is necessary or not. Some dentists will not use a rubber dam if you have severe TMD symptoms because you won’t be able to rest your jaw for quite a long time, which can give you severe TMD symptoms for 6-8 weeks after the procedure — this pain is sometimes worse than the root canal. In the old days, it was taught that every root canal was done with a rubber dam, but more and more, there’s less use of it. I don’t consider this to be a big factor in the success of a root canal, but in some cases, if there is likelihood of dropping an instrument inside a mouth, it’s a good idea. It’s something you can certainly request.


Pulp: Deep inside each of your teeth, underneath the white enamel exterior, is the pulp. Pulp is tissue helps the tooth grow. It also gives the tooth the ability to perceive hot and cold and vibration. Pulp and nerve is good because small cavities can recalcify and solve themselves but only if the tooth is alive and has not had a root canal. Pulp can become inflamed or infected from deep decay, repeated dental procedures on the same tooth, or a crack or chip in the tooth.

Crown: A crown is the procedure that strengthens a hollowed out tooth. A crown is necessary after you get a root canal to protect the tooth after the dead tissue has been scraped out during the root canal. You’ll need a crown after your root canal so that you can bite on your tooth and use it normally after a root canal.

Root Canal: A procedure done by a dentist that preserves a dead or dying tooth — essentially, scraping out the dead issue inside so that the outer portion of the tooth (the white enamel, and the root of the tooth which lives inside your gum) can stay in your mouth, instead of having to be taken out entirely.

Irreversible and reversible pulpitis: Pulpitis is inflammation of dental pulp tissue. If the pulpitis pain is irreversible, this might indicate more serious damage than if the pulpitis pain is reversible.

Endodontist: A dentist who specializes in root canals and procedures that preserve infected or diseased teeth.

Abscess: Essentially a hole in the jawbone. Bone won’t grow in the area around an infection, so this shows up as a dark space on the x-ray.

Percussion sensitivity: Tooth sensitivity, tenderness, or pain when you tap on the tooth.

Hot and cold sensitivity: Just like what it sounds like — this refers to whether your teeth are sensitive to hot or cold drinks.

Lingering and non-lingering pain: Pain that “lingers” (stays around) or does not linger (pain that goes away) are indicators your dentist will use to help determine if you need a root canal or not. When pain is lingering, this means that the tooth isn’t able to recover. When pain is non-lingering, this is a sign that the tooth is able to recover.