Root Canal Therapy

Last updated: November 6, 2026·Reviewed by Soo Jin Kim, DDS

Root canal therapy eases the pain of an inflamed or infected tooth and can save a tooth that might otherwise have to be pulled. The treatment, also called endodontic treatment, removes the soft tissue inside the tooth (the pulp), cleans, shapes, and disinfects the root canals, and then fills and seals them. We do it under local anesthetic, usually over one or two appointments, and then restore the tooth with a filling or, often on a back tooth, a crown. With proper care, most teeth that have had root canal treatment can last for many years. We see most dental emergencies the same day at ConfiDental's Carlstadt office, severe tooth pain and swelling included.

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Overview

A tooth needs root canal therapy when its pulp, the soft tissue of nerves, blood vessels, and connective tissue inside it, becomes infected or so inflamed that it cannot recover. Common causes are deep decay, repeated dental procedures on the same tooth, a faulty crown, and a crack or chip, and an injury can damage the pulp even when no crack is visible. Left untreated, an inflamed or infected pulp can cause pain or lead to an abscess (a pocket of pus at the root tip), and the bacteria can damage the bone that holds the tooth in the jaw. A fully developed tooth can survive without its pulp, because the surrounding tissues continue to nourish it.

Signs that can point to a pulp problem include lingering sensitivity to hot or cold, severe pain when chewing or biting, a pimple-like bump on the gum, swollen or tender gums, and a tooth that has darkened, although some affected teeth cause no symptoms at all. Diagnosis draws on the history of the pain, X-rays, and simple tests compared against neighboring teeth, such as a cold test, tapping on the tooth, and pressing on the gum. Discomfort that fades within a couple of seconds after something cold or sweet usually indicates reversible pulpitis, which typically settles once the cause, such as decay, is treated. Pain that lingers, often for 30 seconds or longer, or that comes on by itself points to irreversible pulpitis, and a pulp that has died (pulp necrosis) no longer responds to testing; both are indications for root canal treatment.

Treatment begins with local anesthetic, and a small protective sheet called a dental dam isolates the tooth to keep it clean and dry. An opening is made through the top of the tooth, the pulp is removed with small instruments, and the canals are cleaned, shaped, and disinfected before they are filled with a rubber-like material called gutta-percha and a sealing cement. A temporary filling closes the opening until the tooth receives its permanent filling or crown, and a post may be placed inside the root when too little tooth remains to hold the restoration. Back teeth are commonly crowned, and in a systematic review of tooth survival, a crown placed after root canal treatment was the factor most strongly associated with keeping the tooth.

Most teeth treated this way are kept for many years. A treated tooth may still heal poorly or develop a new infection later, for example when a narrow or curved canal was not reached, the permanent restoration was delayed, or new decay or a broken filling let bacteria back in. Such a tooth may be retreated, which means reopening it, removing the old filling material, and cleaning and refilling the canals, or treated with endodontic surgery, most commonly an apicoectomy (root-end resection), which removes the very tip of the root. When a tooth cannot be saved, the alternative is extraction, usually followed by replacing the tooth with an implant, a bridge, or a partial denture.

When It's Recommended

Pain or sensitivity to hot or cold that lingers after the stimulus is removed, a sign of irreversible pulpitis
Spontaneous, unprovoked tooth pain, which may worsen when lying down or bending over
Pulp necrosis, in which the pulp has died, sometimes shown by a tooth that has darkened or no longer responds to testing
A tooth abscess or infection at the root tip, with signs such as a pimple-like bump on the gum, swelling of the gum or jaw, or pain when chewing or touching the tooth
Deep decay that has reached the pulp
A cracked or chipped tooth in which the crack has reached the pulp but does not extend below the gum line
An injury to a tooth that has damaged the pulp, even without a visible crack or chip

What are the risks of Root Canal Therapy?

When to Avoid

A tooth that cannot be restored because too little sound tooth structure remains after decay or fracture
A crack that extends below the gum line, which leaves the tooth no longer treatable by root canal therapy
A vertical root fracture (a crack that begins in the root and extends toward the chewing surface), where treatment may involve extraction of the tooth

Possible risks

Tenderness of the tooth when biting and mild jaw soreness for a few days after treatment
A flare-up of pain or swelling in the days after treatment
Temporary numbness from local anesthetic, with a risk of biting the lip, cheek, or tongue while numb
Infection that persists or returns in the tooth root, which may lead to retreatment, endodontic surgery such as an apicoectomy, or extraction
New decay or a loose, cracked, or delayed crown or filling can let bacteria back into the canals and cause a new infection
Fracture of the treated tooth, particularly before the permanent crown or filling is placed
Nerve damage
Allergic reaction to a medicine used during or after treatment
Loss of the tooth
This is not an exhaustive list, and individual risks depend on the tooth, the extent of the infection, and the restoration that follows

Who needs extra care

Certain heart conditions, such as a prosthetic heart valve or a history of infective endocarditis, may call for antibiotic prophylaxis before procedures that manipulate the gums or the tissue around the root tip
Antiresorptive medicines such as bisphosphonates or denosumab are reviewed before treatment; for people at elevated risk of medication-related osteonecrosis of the jaw, an ADA expert panel considers root canal treatment preferable to surgery when the tooth can be saved, without instrumentation beyond the root tip
Pregnancy is taken into account when choosing medicines and imaging; the ADA and ACOG agree that root canals can be performed safely during pregnancy, local anesthetics with epinephrine may be used, and dental X-rays are considered safe at any stage
Fever, malaise, or a weakened immune system changes how a dental infection is managed, and antibiotics may be added to root canal treatment in these situations
A latex allergy is noted before treatment, because the protective sheet (dental dam) used to isolate the tooth is commonly made of latex

What to Expect During Treatment

The visit opens with your symptoms: we ask what the tooth is doing, note your dental and medical history and medications, and examine the tooth and gums
We take digital dental X-rays and do simple tests, such as a cold test, tapping on the tooth, and pressing on the gum, comparing the results with neighboring teeth to confirm that the pulp is the source of the problem
Local anesthetic numbs the tooth and the surrounding area
A small protective sheet called a dental dam keeps your tooth clean and dry while we work
We make a small opening through the top of the tooth to reach the pulp chamber
We remove the pulp, then clean, shape, and disinfect each root canal with small instruments, draining any abscess
When treatment is spread over two visits, medicine may be placed in the canals and the tooth closed with a temporary filling in between
We fill the cleaned canals with gutta-percha and a sealing cement
A temporary filling closes the opening until the permanent restoration is placed
At a follow-up visit we place the permanent filling or crown, sometimes with a post in the root when too little tooth structure remains to hold it
At a later check, we assess whether the infection has cleared and the tissue around the root has healed, often using an X-ray

How does Root Canal Therapy work?

Bacteria inside the root canal system drive the infection and inflammation that root canal therapy treats. Removing the inflamed or dead pulp, disinfecting the canals, and sealing them takes away that source, which allows the tissue around the root tip to heal and helps prevent reinfection.

The pulp helps a tooth's root grow while the tooth is developing, but a fully developed tooth can survive without it, because the tissues around the root continue to nourish it. This is what allows the pulp to be removed while the tooth itself is kept.
The canals are cleaned and shaped with small instruments so that they can be disinfected and then sealed along their length. Gutta-percha, a rubber-like material, is placed with a cement to seal the canals completely.
A permanent crown or filling then seals the top of the tooth. A loose, cracked, or delayed restoration, or new decay, can expose the root canal filling to bacteria and cause a new infection in the tooth.
An American Dental Association guideline on pulp-related tooth pain and swelling prioritizes immediate dental treatment, such as root canal therapy or draining an abscess, and reserves antibiotics for signs of systemic involvement such as fever or malaise.

Recovery & Aftercare

Numbness from the anesthetic typically lasts 2 to 4 hours, and you may be advised not to eat until it wears off
The tooth may feel sore or tender to biting for a few days as the area heals, and in most cases symptoms improve within three to five days
Over-the-counter pain relievers such as ibuprofen or acetaminophen are often sufficient for the soreness, used within the dosing directions on the label
Most patients return to work or school the same day
Chewing hard food or biting down heavily on the treated tooth is typically avoided until the permanent crown or filling is in place, to protect the tooth from breaking
Brushing and flossing continue as usual, gently around the treated area
Contact the dental office promptly if you notice visible swelling inside or outside the mouth, severe pain or pressure lasting more than a few days, a rash, hives, or itching after taking a medicine, a bite that feels uneven, a temporary filling that comes out, or the return of the symptoms you had before treatment

Alternative Treatments

Tooth extraction, which removes the tooth, usually followed by replacement with a dental implant, a bridge, or a removable partial denture so that neighboring teeth do not shift into the gap
Treating the cause alone, such as removing decay and placing a filling, when the pulp is only reversibly inflamed and can recover
Antibiotics, which an ADA guideline reserves for infections with systemic signs such as fever or malaise, and which accompany dental treatment of the tooth without replacing it
Leaving the tooth untreated, which risks continued pain, an abscess, and damage to the bone around the tooth

What the Research Says

Root canal treatment removes inflamed or infected pulp from inside a tooth, cleans and disinfects the canals, and fills and seals them so the natural tooth can be kept[1]
Irreversible pulpitis, in which the inflamed pulp cannot heal, and pulp necrosis, in which the pulp has died, are both indications for root canal treatment[9]
In a United States study of nearly 1.5 million teeth, 97% remained in the mouth 8 years after initial nonsurgical root canal treatment[15]
Across 72 studies pooled in a systematic review, the share of patients reporting pain fell from about 81% before root canal treatment to 40% one day after and 11% one week after[17]
In a university cohort, root-canal-treated teeth that were not crowned afterward were lost at about six times the rate of teeth that were crowned[16]

Who provides this at ConfiDental Family and Cosmetic Dentistry

Soo Jin Kim

DDS

Performs root canal treatment in our office and refers most complex cases to a specialist.

NYU-trained family and cosmetic dentist with a hospital residency at Mount Sinai

Full profile

Frequently Asked Questions

What is a root canal?

A root canal is a treatment for an inflamed or infected tooth that removes the pulp, the soft tissue of nerves and blood vessels inside it, so the tooth itself can be kept. The canals inside the root are cleaned, disinfected, filled, and sealed, and the tooth is then restored with a filling or crown. It is done under local anesthetic and typically relieves the pain the infection was causing.

Does a root canal hurt?

Local anesthetic numbs the tooth first, so you typically feel pressure or movement during treatment, not pain, and most patients report being comfortable. The tooth may be sore or tender to biting for a few days afterward, and in most cases this improves within three to five days. Pain tends to be worst before treatment, and in pooled studies the share of patients in pain fell sharply within a week of it.

Is root canal treatment safe?

Root canal treatment is a routine, well-established dental procedure carried out under local anesthetic, and treating the tooth can keep an infection from spreading to the bone around it. The ADA and the American College of Obstetricians and Gynecologists agree that root canals can be performed safely during pregnancy. Specific risks are listed in the risks section.

How many appointments does a root canal take?

Most root canals are completed in one or two appointments, each often 60 to 90 minutes, depending on the tooth and the extent of the infection. When treatment is spread over two visits, a temporary filling protects the tooth in between. Another visit is usually needed for the permanent filling or crown, and a later check looks at whether the area has healed.

What happens during a root canal?

Once the tooth is numb, a small protective sheet called a dental dam keeps it clean and dry. We open the top of the tooth, remove the pulp, the soft tissue inside it, and clean, shape, and disinfect the canals. We fill them with a rubber-like material called gutta-percha and seal them, and a temporary filling closes the tooth until it is permanently restored.

Who is not a candidate for a root canal?

Root canal treatment depends on the tooth being restorable afterward. A tooth with too little sound structure left after decay or fracture, or with a crack that extends below the gum line, can no longer be treated with a root canal. A vertical root fracture, a crack that begins in the root, may also mean the tooth needs to be extracted. An examination and X-rays show which applies.

Is a crown needed after a root canal?

Back teeth are commonly restored with a crown after a root canal, and in a systematic review of tooth survival, a crown after treatment was the factor most strongly linked to keeping the tooth. A front tooth with enough sound structure may be restored with a filling. Chewing hard food on the treated tooth is usually avoided until the crown or filling is in place.

What should I do if I think I need a root canal?

Call our office at (201) 729-0900 and describe what the tooth is doing, such as pain when you bite or swelling in the gum. If dental visits make you anxious, say so when you call and ask about oral conscious sedation.

Sources & References

This article draws from 22 peer-reviewed sources.

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