Root Canal (Tooth Anatomy)

What Is Inside a Root Canal?

The root canal houses the dental pulp — a soft connective tissue that keeps the tooth alive. The pulp contains:

• Blood vessels — which supply the tooth with oxygen and nutrients
• Nerves — which give the tooth its ability to sense temperature, pressure, and pain
• Connective tissue — which supports and maintains the internal structure of the tooth
• Lymphatic vessels — which support the tooth's immune defences

The pulp extends from the pulp chamber — the wider space inside the crown — down through the root canals to the tip of the root, called the apex. At the apex, a small opening called the apical foramen allows blood vessels and nerves to connect the pulp to the surrounding tissues in the jaw.

The root canal itself is lined by dentine — the hard calcified tissue that forms the main body of the tooth. The outer surface of the root is covered by cementum, a layer of hard tissue that anchors the tooth to the periodontal ligament and the surrounding bone.

How Many Root Canals Does a Tooth Have?

The number of root canals varies by tooth type:

• Front teeth (incisors and canines) — typically one root and one canal
• Premolars — usually one or two roots, with one or two canals
• Molars — typically two to three roots, with two to four canals or more

Root canal anatomy varies between individuals. Some teeth have additional smaller channels called accessory canals that branch off from the main canal, most commonly near the root tip.

These connect the pulp to the periodontal ligament and can be relevant during endodontic treatment.

What Does a Root Canal Do?

During the development of a tooth, the pulp inside the root canal plays an active role — forming the surrounding dentine and helping the tooth grow and mature. Once a tooth is fully developed, the pulp is no longer essential for its structural survival, since the tooth continues to receive nourishment from the surrounding tissues. However, the nerves within the root canal remain functional, allowing the tooth to register sensation.

The root canal system also acts as a pathway for the tooth's immune defences, helping the tooth respond to infection or injury.

What Happens When a Root Canal Becomes Infected?

The pulp inside the root canal can become inflamed or infected when bacteria reach it. This most commonly occurs as a result of:

• Deep tooth decay — when a cavity progresses through the enamel and dentine and reaches the pulp
• A cracked or fractured tooth — which creates an opening through which bacteria can enter
• Repeated dental procedures — which can compromise the integrity of a tooth over time
• Dental trauma — a knock or impact to a tooth that damages the pulp, even without visible external damage

When the pulp becomes infected, the bacteria multiply within the root canal system. The infection can spread to the surrounding bone through the apical foramen, forming a dental abscess — a pocket of pus at the root tip. Visit dental abscess for more information.

Why Should an Infected Root Canal Not Be Left Untreated?

An infected root canal does not resolve on its own. Without treatment, the infection progresses and the consequences become more serious over time:

• Pain and swelling — infection within the pulp typically causes significant pain, sensitivity to heat and cold, and swelling in the surrounding gum and jaw
• Abscess formation — bacteria spreading beyond the root tip form a dental abscess, which can cause severe pain, facial swelling, and in some cases fever
• Bone loss — a longstanding infection destroys the surrounding jaw bone, potentially compromising adjacent teeth and future treatment options
• Tooth loss — if left too long without intervention, the tooth may no longer be salvageable and extraction becomes the only option
• Systemic spread — in rare but serious cases, a dental infection can spread beyond the mouth to other parts of the body

When the pulp is infected, root canal treatment — carried out by a Specialist Endodontist — removes the infected tissue, cleans the canal system, and seals the tooth to prevent reinfection. At Drs. Nicolas & Asp Centers, our Specialist Endodontists use high-powered microscopes for precision during treatment. In most cases the tooth can be preserved. Visit our Endodontics page for more information.