Tooth pain that lingers, sensitivity that does not settle, or swelling around your jaw can be easy to dismiss as something minor. In some cases, though, these are signs that the soft tissue inside a tooth has become infected, and that infection needs attention before it spreads further.
A root canal infection occurs when bacteria reach the pulp, the soft tissue at the centre of a tooth containing nerves and blood vessels. Left without treatment, the infection can affect the surrounding bone and neighbouring teeth. Understanding the warning signs early makes a significant difference to what root canal treatment options remain available.
Quick Overview
- A root canal infection happens when bacteria reach the soft tissue inside a tooth, causing inflammation or an abscess
- It may affect anyone with deep tooth decay, a cracked tooth, or a history of repeated dental work on the same tooth
- Root canal treatment involves removing the infected tissue, cleaning the canals, and sealing the tooth to prevent reinfection
- Outcomes depend on factors including how far the infection has progressed, the tooth’s structure, and individual healing
- Persistent pain, swelling, or sensitivity that does not settle are the key indicators that prompt assessment is needed
Keep reading to understand what causes a root canal infection, how it is treated, and when to seek dental care.
What Is a Root Canal Infection?
A root canal infection develops when bacteria enter the pulp of a tooth. The pulp sits in a hollow space at the centre of each tooth and extends down through the root canals. It contains the nerves, blood vessels, and connective tissue that support the tooth during its development.
Once fully formed, a tooth can function without its pulp. But when the pulp becomes infected, the bacteria multiply quickly, and the infection can spread into the surrounding bone if it is not addressed. Untreated infection may cause bone loss around the tooth, or ultimately lead to tooth loss.
What Are the Signs of a Root Canal Infection?
Some root canal infections develop without any obvious symptoms early on. When symptoms do appear, the most common include:
- A persistent toothache, particularly when biting or chewing
- Sensitivity to hot or cold that lingers after the source is removed
- Swelling of the gum near the affected tooth, or swelling that extends toward the jaw or face
- A pimple-like bump on the gum near the tooth, which may indicate pus building up
- Tooth discolouration, where the affected tooth appears darker than surrounding teeth
- A bad taste in the mouth, which may indicate the presence of an abscess
Pain levels vary between individuals. Some people experience intense, persistent pain while others notice only mild discomfort or intermittent sensitivity. If any of these signs are present, speaking with a dentist is the appropriate next step. Individual presentations vary considerably.
What Causes the Pulp to Become Infected?
Several factors can allow bacteria to reach the inner layer of a tooth: 
- Deep tooth decay that reaches through the enamel and dentine to the pulp
- A crack or fracture in the tooth that creates an entry point for bacteria
- A dental injury, even one that did not cause visible damage at the time
- Repeated dental procedures on the same tooth, which can weaken its structure over time
- Advanced gum disease, which in some cases can allow bacteria to travel down to the root
It is worth noting that an infection can develop even when a tooth has previously been treated. If bacteria re-enter through a leaking filling or an untreated canal space, further treatment may be required.
What Does Root Canal Treatment Involve?
Root canal treatment is a dental procedure that removes infected pulp tissue, cleans and shapes the root canal system, and seals the tooth to prevent reinfection. It is one of the most commonly performed dental procedures and is generally carried out under local anaesthetic.
Root canal treatment typically requires more than one appointment. At the first visit, the dentist removes the infected pulp, disinfects the canal system, and places a temporary filling. At a subsequent visit, the canals are permanently sealed with a filling material, and a crown or restoration is placed over the tooth to protect it.
Success rates for root canal treatment are generally high, and most people can expect a functional tooth following the procedure. Individual outcomes vary and depend on factors including the extent of the infection, the tooth’s anatomy, and how the tooth is restored afterwards.
A tooth that has undergone root canal treatment may eventually darken in colour. Your dentist can advise on options to manage this where relevant.
What Happens If a Root Canal Infection Is Left Untreated?
A root canal infection will not resolve on its own. Symptoms may fluctuate, but the underlying infection continues to progress inside the tooth. Over time, this can lead to:
- Formation of a dental abscess, which is a pocket of pus that develops at the root tip or in the surrounding bone
- Spread of infection into the jawbone, causing bone loss in the area
- Spread to neighbouring teeth or soft tissue, which in rare cases can become serious
- Loss of the tooth if the damage becomes too extensive to restore
Treating the infection early preserves more of the natural tooth structure and reduces the complexity of the procedure required. Delays tend to narrow the available options.
Can a Root Canal Infection Come Back?
In some cases, a tooth that has already been treated may develop a further infection. This can occur if bacteria re-enter through a cracked restoration, a poorly sealed canal, or an untreated branch within the root canal system. When this happens, a procedure called root canal retreatment may be considered.
Retreatment involves removing the existing root filling material, re-cleaning the canal system, and resealing the tooth. Whether retreatment is appropriate depends on the condition of the tooth and the surrounding bone. Your dentist can assess this and discuss the options with you.
How to Reduce the Risk of Tooth Infection
While not all root canal infections can be prevented, maintaining good oral hygiene significantly reduces the risk of tooth decay progressing to the point where the pulp is affected. Practical steps include:
- Brushing twice daily with fluoride toothpaste
- Flossing daily to remove plaque from between teeth where a toothbrush cannot reach
- Attending regular dental check-ups so decay or cracks can be detected early
- Avoiding using teeth to open packaging or bite on hard objects, which can cause cracks
- Wearing a mouthguard during contact sports to protect against dental injury
Early detection remains one of the most effective ways to avoid more involved treatment. Some infections show no symptoms until they are well established, which is one reason routine dental visits carry genuine value.
A Considered Approach to Root Canal Treatment
A root canal infection is a dental concern that benefits from prompt, professional assessment. The symptoms can be easy to minimise, particularly when pain is intermittent, but the underlying infection does not resolve without treatment. Addressing it early generally means simpler treatment and a better chance of keeping the natural tooth.
At Cross Road Dental, Dr Christine Brzezniak has a particular interest in root canal therapy and takes a minimally invasive approach to restorative care. If you are experiencing tooth pain, swelling, or lingering sensitivity, we welcome you to get in touch. You can book an appointment online or call us on (08) 8004 5137. We are open Monday to Saturday, with extended evening hours on Mondays and Tuesdays.
Note: Any surgical or invasive procedure carries risks. Before proceeding, you should seek a second opinion from an appropriately qualified health practitioner.
Frequently Asked Questions
How long does root canal treatment take?
Most people need more than one appointment to complete root canal treatment. The initial session focuses on clearing out the infected tissue and disinfecting the canal system, and a temporary seal is placed while the tooth heals. A follow-up visit is used to place the permanent filling and any crown or restoration needed to protect the tooth. How many visits are required and how long each takes will depend on the complexity of the tooth’s root structure and how far the infection has progressed.
What happens if a root canal infection is not treated?
Without dental treatment, the bacteria inside the tooth continue to multiply, and the infection spreads beyond the pulp into the surrounding tissue and bone. This can result in an abscess, progressive bone loss around the root, and in some cases the tooth becoming unsalvageable and requiring removal. Getting the infection assessed and treated promptly gives the tooth the best chance of being kept.
References
Department of Health and Human Services, Victoria. (2025). ‘Root canal treatment’. Better Health Channel, 14 July. Melbourne, VIC: State Government of Victoria. https://www.betterhealth.vic.gov.au/health/conditionsandtreatments/root-canal-treatment
Healthdirect Australia. (2025). ‘Root canal treatment’. Healthdirect Australia, February. https://www.healthdirect.gov.au/root-canal-treatment
Australian Dental Association. (n.d.). ‘Tooth Decay’. teeth.org.au. Sydney, NSW: Australian Dental Association. https://teeth.org.au/tooth-decay