A tooth that goes dark after a knock or an injury is one of the more common dental concerns we see at our Pymble practice, and one of the more worrying for the patient. The good news is that a dark tooth after trauma is not always a sign of something serious, and there are effective treatments for the cases that need it. At Dentist Pymble, we assess and treat traumatised teeth for patients across the Ku-ring-gai region, and the right answer depends on what is causing the discolouration and what the underlying pulp looks like. This page covers why a tooth goes dark after an injury, the difference between staining and pulp necrosis, when to see a dentist, the treatment options, and the long-term outlook.

Why does a tooth go dark after an injury?

The most common reason is bleeding inside the tooth. When a tooth is hit hard enough to damage the pulp, the blood vessels inside the pulp chamber can rupture, and blood leaks into the dentine (the layer underneath the enamel). The blood breakdown products — particularly iron sulphides — stain the dentine from the inside, and the tooth takes on a grey or brown appearance that gets darker over the first few weeks after the injury.

The darkening can be temporary or permanent. In some cases, the pulp recovers and the tooth gradually returns to its normal colour over months. In other cases, the pulp dies (pulp necrosis) and the darkening becomes permanent unless treated. The two outcomes cannot be distinguished by the colour alone — you need clinical testing and x-rays to know which one you have.

Pulp necrosis vs staining — what’s the difference?

The two main causes of a dark tooth after trauma are staining from internal bleeding (with the pulp still alive) and staining from pulp necrosis (with the pulp dead). The distinction matters because the treatment is very different.

• Staining from internal bleeding with a vital pulp — the tooth is dark, but the pulp is still alive. Often the colour improves over months as the pulp recovers. No treatment needed for the dark colour itself, though the tooth will be monitored for signs of necrosis developing later.
• Pulp necrosis — the pulp is dead, and the darkening is permanent. The tooth usually needs root canal treatment to remove the dead pulp, and may need internal bleaching or a veneer/crown to address the cosmetic appearance.

A less common but more serious complication is internal resorption, where the tooth starts to resorb itself from the inside. This is usually picked up on x-ray and requires prompt endodontic treatment to save the tooth. Regular monitoring after trauma is the main way to catch it.

When to see a dentist

If you have had a tooth knocked, hit, or traumatised in any way, and the tooth is now darker than it used to be, it is worth a check-up. The dentist will:

• Test the vitality of the pulp (with cold, heat, or an electric pulp tester)
• Take an x-ray to check for signs of necrosis or internal resorption
• Examine the tooth for other signs of damage (cracks, mobility, displacement)
• Discuss the findings and the recommended follow-up

Most dark teeth after trauma are not emergencies, but they are worth assessing within a few weeks of the injury so that any necessary treatment can be planned.

Treatment options (root canal + internal bleaching, veneer, crown)

The treatment depends on the cause and the patient’s goals:

• No treatment — for teeth that are dark but asymptomatic and the pulp is still alive, the colour often improves over months. The tooth is monitored with periodic x-rays.
• Root canal treatment — for teeth with pulp necrosis. The dead pulp is removed, the canals are cleaned and sealed, and the tooth is preserved. This is the foundation for any further cosmetic treatment.
• Internal bleaching (walking bleach) — for root-canaled teeth that are still dark. A bleaching agent is sealed inside the tooth for 1-2 weeks, and the process is repeated as needed until the tooth matches the neighbouring teeth.
• Veneer or crown — for teeth that are too dark for bleaching to work, or where the patient wants a more predictable result. Covers the discolouration completely and can also change the shape if needed.
• Extraction — for teeth that are too damaged to save. Usually a last resort.

The root canal therapy service at our Pymble practice is the starting point for the cases that need endodontic treatment. We can do the internal bleaching in-house, and we work with trusted local labs for veneers and crowns when needed.

Long-term outlook for a traumatised tooth

The long-term outlook depends on the severity of the initial injury:

• Mild injury (small chip, brief sensitivity) — usually heals completely with no lasting effect
• Moderate injury (concussion, subluxation, crack) — the tooth usually survives, but may need monitoring and possibly root canal treatment years later
• Severe injury (avulsion, intrusion, root fracture) — the tooth may survive with treatment, but the long-term prognosis is reduced and extraction is sometimes the eventual outcome

The key to long-term success is regular monitoring. Most complications of dental trauma (pulp necrosis, internal resorption, root resorption) develop over months to years, and catching them early is the difference between saving the tooth and losing it. The recommended monitoring is x-rays at 6 months, 12 months, and then yearly for at least 5 years after the trauma.

If you live in Pymble, Gordon, Turramurra, Wahroonga or anywhere else in the Ku-ring-gai area and you have a dark tooth after trauma, or you have had a recent dental injury, call our practice. We see neighbouring Gordon patients and other nearby residents, and the earlier we see a traumatised tooth, the better the long-term outcome.

Frequently asked questions

Why is my tooth dark after being hit? The most common reason is bleeding inside the tooth from the impact. Blood breakdown products stain the dentine from the inside, giving the tooth a grey or brown appearance. The discolouration may improve over months if the pulp recovers, or it may be permanent if the pulp dies.

Will a dark tooth after trauma go back to normal? Sometimes, particularly if the pulp is still alive. The colour often improves over 6-12 months as the pulp recovers. If the pulp dies, the discolouration is permanent without treatment.

Do I need a root canal for a dark tooth? Only if the pulp has died. The dentist will test the pulp and take an x-ray to determine whether root canal treatment is needed. Many dark teeth after trauma are still vital and do not need a root canal.

Can a dark tooth be whitened? External whitening does not work on internal discolouration. Internal bleaching (walking bleach) is the standard approach for dark root-canaled teeth, and works well in most cases. For teeth that are still vital but dark, the options are usually to wait and see, or to cover the tooth with a veneer or crown.

How long do I need to monitor a traumatised tooth? At least 5 years, with x-rays at 6 months, 12 months, and then yearly. Most late complications of dental trauma show up in the first 2-3 years, but some (particularly root resorption) can develop later.