How does a root canal treat cavities?

When the cavity is very deep, it may be necessary to have a root canal. This is because the soft tissue inside your teeth has become infected. A root canal is when this soft tissue is removed.

The pulp chamber and root canal(s) of the tooth are then cleaned and sealed. If the infected pulp is not removed, pain and swelling can result, and your tooth may have to be removed.

Root canals do not treat cavities. Neglected cavities that spread to the pulp of the tooth lead to an infection that necessitates a root canal. During the root canal, the decay is removed along with the infected pulp of the tooth and the sterile space is filled with an inert material. Following the root canal, the tooth needs to be restored with a crown and sometimes a post and core as well

Root canals are generally used to treat a "large" cavity where the pulp is affected (or infected). In basic terms, the tooth is somewhat hollowed out, with the insides (canals) cleaned and filled. Almost always, a crown is then used to finish the job. A root canal can "save" a tooth that would otherwise have to be extracted, making it a sometimes-necessary procedure if one wants to keep their teeth.

A root canal treats a cavity that has extended to the inside part of the tooth called the pulp. The decay is removed from the tooth and pulp, and the pulp is filled with a root canal filling. The outer part of the tooth is then filled with a filling. Sometimes the outside part of the tooth needs a crown after a root canal.

Root canals treat cavities in no way at all: They treat a diseased nerve which is not tooth structure at all. Left alone, your tooth will become extremely sensitive.

Decay is caused by bacteria, streptococcus mutants and some other bacteria that ingest sugars and produce acid. 

This acid dissolves tooth structure and inflames gum tissue. The dissolved tooth structure is decay.

The bacteria  also causes inflammation of the pulp. Pulp is nerve tissue and blood vessels in the chamber in the center of the tooth that is designed to hold it. If the infected tissue is not treated the tooth will abscess and infect. At the very least it will make a deep cavity sensitive to hot and cold; and in full blown infection pain when you chew on the tooth. 

Now if you remember I have a recurring theme that the patient is in partnership with their dentist in the health of their mouth. Without your help we can't keep you healthy. Your part is home care and making your re-care appointments in a timely manner. That would be every three months or six months depending on your gum health. That is your responsibility!

The reason I stress this particularly in connection with root canal treated teeth is because your nerve is removed. Without sensation from a nerve you feel no hot and cold sensitivity that you would normally feel with a vital tooth. I have seen teeth totally destroyed by decay that the patient had no awareness that this was happening. Also the patient had not been in to see their dentist for quite some time.

Sometimes when the decay has resulted in such a loss of tooth structure, a root canal is necessary to help in the restoration of the tooth. The dentist will place a post down the root canal space where the gutta percha was and place a metal or fiber post in its place. This acts like reinforced steel in concrete. It holds the material in place better than if you didn't have anything there.

In conclusion I want to review what treatment of a cavity entails. Decay is the process by which the hard tissue of the tooth becomes soft. When we treat a decayed tooth the caries, or softened tooth structure, is removed. That area of the tooth is replaced with, a filling, inlay, onlay or crown. If the decay is so deep that it involves the nerve tissue then a root canal is necessary. The roots that have been treated can be used to reinforce the fillings or crowns with posts.
Romesh Nalliah
For a small cavity, the dentist will clean the cavity and then fill it with a dental restoration. When a cavity is very deep it can affect the nerve. This is more serious and can lead to severe pain if not managed soon. In such cases, a filling is insufficient and the tooth requires root canal treatment.

For a root canal treatment, the dentist will remove the infected nerve under local anesthetic. The space is then smoothed and a root canal filling (gutta percha) is used to fill the empty nerve space. The infection will heal due to the removal of the cause of infection and, usually, no antibiotics are needed. In this way root canal treatment helps to manage a deeply cavitated tooth.
Root canal treatment does not actually treat cavities. Endodontic (root canal) therapy treats the result that extensive decay has on the pulpal tissues within the canals of the tooth including various degrees of sensitivity and inflammation and eventually infection.

The destruction of tooth structure caused by the decay/cavities is corrected by restoration of the tooth, often with a build-up and crown/cap. The tooth must be properly restored following root canal treatment in order for the treatment to be successful and for the tooth to last as long as possible.
The cavity is removed when the general dentist or endodontist begins your root canal treatment. Because the cavities that create the need for a root canal are often large, what results in a hollowed out tooth (or a shell of a tooth) that requires further treatment -- usually a core buildup to fill the "hole" created by cavity removal and a crown to reinforce the weak, brittle shell that remains.
Lucia Yau, DDS
Root canal treatment removes nerve tissues and bacteria from the tooth, thus removing infection. The cavity portion of the tooth still needs to be removed, typically that is done in conjunction with the root canal procedures; thus stopping cavities from getting larger.

When a cavity is small it can usually be treated with a simple filling. However, when a cavity is large enough it can affect the nerve inside the tooth. Once the cavity reaches the inside nerve of the tooth it will need Root canal treatment. Part of doing the root canal treatment is removing the bad tooth structure that affected the nerve, along with removing the nerve in the tooth. It is a much more invasive procedure then when a cavity is small and caught early. It is recommended that you see a dentist regularly so that early detection is possible.  

To echo what my previous colleagues stated, it is important to have a restoration placed on the tooth. Just because you are pain free does not mean the tooth is "cured" or that no other problems can occur. Remember, it isn't just the nerve of the tooth that is taken out from the pulp chamber (thus resulting in no more pain, hopefully.) The blood supply to the tooth is also removed. Therefore, the tooth does not get any nourishment, and can become brittle over time and can fracture. This could result in loss of tooth pending type of fracture, recurrent decay or another infection! Refer to (American Association of Endodontics) or (click on 'for the patient').

Root canal treatment is usually the result of large, neglected cavities. If a cavity results in pain and/or infection surrounding the tooth then it could be said that the root canal treatment partially repairs the cavity bearing tooth.

The complete restoration of a cavity requiring root canal treatment would also include at minimum, a filling and most likely a crown or cap with possible reinforcement internally for strength and function.
Root canals are used to treat cavities that reach the inner pulp of the tooth and affect the nerve in the root of the tooth. The dentist drills through the surface of the tooth, removes the affected pulp, and cleans the canals, which are tiny channels within the tooth, using special instruments and medications. The tooth is then temporarily filled and sealed. Later, the tooth is given a permanent filling and a crown is placed over the top of the tooth. A root canal can save a tooth if the decay or damage is not so severe that the tooth must be extracted.

Continue Learning about Cavities


Cavities are tiny holes in your teeth that have developed from decay. Left untreated, cavities will get larger, and can cause toothache and possible loss of teeth. Anybody can get a cavity, but you put yourself at greater risk if ...

you don't brush regularly, or frequently consume sweets or sugary drinks. Your dentist can help prevent cavities with fluoride treatments, and can find them by taking pictures (X-rays) of the teeth. Once found, the dentist may treat your cavity with a filling or if extensive, with a crown. If there has been an extensive infection, other treatments, including antibiotics or a root canal surgery may be indicated.

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.