Does a root canal hurt?

root canal

A root canal is the most the feared dental procedure among folks. It is not painful for most patients because of the use of local anaesthesia, however, almost 17% of patients describe it as the most painful experience.

Pain is a subjective feeling, and everyone perceives it differently. Women experience more pain than men. Several factors cause pain before, during and after the root canal therapy.  We will see the reasons for each of them separately.

Pain before the root canal treatment

Discomfort and pain arises in the tooth either due to irreversible pulp damage (root canal infection), dead (necrosed pulp) tooth or abscess where infection comes of tooth into the bone and causes pain and swelling.

Pain during the root canal treatment

Patients feel varying intensities of pain during the endodontic procedure. Duration of appointment also affects pain levels during the procedure. Long appointments often cause pain because of anxiety of opening mouth for a long time. Following are the reasons of pain during the procedure.

Inadequate anesthesia

Anatomical differences in some patients often make it difficult for a dentists or root canal specialists (endodontists) to numb the area.

Highly infected tooth and abscess present difficultly to anaesthetise the tooth because the nerves in and around the tooth become hypersensitive and resistant to anaesthetic agent.

Dentists try different techniques to numb the area like dental blocks (injection given remote to the site of infection), PDL injections (injection given in the space between tooth and gums) or injection directly into the canal. Experienced dentist or endodontist attains anesthesia successfully in these situations.

Instrumentation past the end of the root

Sometimes a dentist inadvertently pushes the instrument or disinfectant solution past the root. This triggers pain or inflammation during or after the procedure.

This may not have any effect on the treatment in the long run.  It heals on its own and no treatment is needed.

Pain after the root canal treatment

Most patients experience some form discomfort after a root canal treatment because of the irritation and inflammation around the treated tooth. The pain is mild to moderate in nature and lasts for 1-7 days.

Its resolves as soon as the tooth surrounding structures heals. However, if you experience severe pain, call your dentist.

Following are the causes of pain after the appointment:

Improper cleaning of root canals

This occurs due to the incomplete cleaning of tooth canals. Every tooth has one more roots and each root contains one or more canals of varying lengths.  The aim of the root canal treatment is to clean, fill and seal it till its end. Therefore length of every canal is measured during the procedure.

Incorrect root canal determination leads to either short fillings leaving behind infected pulp or overfilled root canals extending outside the tooth.

Improper instrumentation or disinfection also leaves behind infected tissue and requires re-treatment of the tooth. You may get a root canal infection (re-infection) and experience more or less the same pain you had before treatment.

Missed root canal

As discussed, teeth roots have one more canal. Some people have an extra canal and could be missed during the treatment. Moreover, few people have a canal isthmus (a communication between two canals that contains pulp tissue) in their roots. It is inaccessible to instruments, solutions and medicines injected into the canal and is mostly found in lower molar canals.

This infected tissue can cause pain and reinfection. Isthmus cleaning requires cleaning after surgically removing the end of root, followed by filling and sealing. Missed or extra canal requires re-treatment.

Expulsion of infected pulp outside tooth

Expulsion of infected pulp outside the root canals of tooth during instrumentation (cleaning with instruments) is the main cause of pain following root canal procedures.

Irritation of tissues outside the tooth by accidentally pushing the instrument or disinfectant solution past the end of root leads to post-treatment pain.

This irritated tissues or extruded pulp debris heals on its own within few days.

Cracked tooth

Teeth are prone to crack during the cleaning or filling of root canals because of the weakened tooth structure due to decay. Crack can already be present before the treatment and can lead to tooth loss.


Root canal is painless and less distressful for majority of the patients because of the injection of local anesthetic injection. However, it can be painful for people with highly infected tooth and tooth abscess. Skilled dentist and endodontics are trained in handling such situations.

Leave a Comment

Your email address will not be published.