A single tooth turning dark or grey usually means the nerve inside it is damaged or dying, most often after an old knock to the tooth, deep decay or a large filling. It isn’t always painful, and it isn’t always an emergency, but a dead nerve can become infected over time. The most common fix is root canal therapy, followed by whitening from the inside or a cosmetic restoration to match the colour.
Common causes of one dark tooth: an old injury, a dying or dead nerve, deep decay, a large silver filling showing through, a past root canal, or internal changes in the tooth. Whole-mouth yellowing is a different issue, usually from food, drinks, smoking and age.
People usually notice it in a photo or a mirror. One front tooth looks a shade or two darker than its neighbours. Sometimes it’s grey, sometimes brown, occasionally pinkish.
At Bolton Park Dentistry, we see this most often in adults who remember a fall, a sports hit or a face plant on the ice years ago. The tooth seemed fine at the time. Then, slowly, it changed colour.
If the tooth has been heavily filled or root treated, it may also be weaker than it looks. In that case, protecting it with one of our dental crowns can prevent it from cracking later.
For front teeth, appearance matters too. Porcelain veneers can cover a stubborn dark tooth, and some teeth respond well to teeth whitening, either from the outside or from inside after a root canal.
Why does one tooth turn dark?
1. Injury and a dying nerve
A blow to a tooth can damage the blood vessels inside it. Blood breaks down inside the tooth and stains the dentin from within, a bit like a bruise that can’t heal. Over weeks or months, the tooth turns grey or dark.
The nerve may stay alive and the colour may partly return, or the nerve may slowly die. That’s called pulp necrosis.
2. Deep decay
Decay that reaches the nerve can inflame and eventually kill it. The tooth may look darker, especially near the gumline, and may have had a phase of sensitivity or pain that then stopped.
3. Old silver (amalgam) fillings
Large silver fillings can make a tooth look grey, because the metal shows through thin enamel. Over time, the metal can also stain the tooth structure around it.
4. Past root canal treatment
Teeth that had a root canal years ago sometimes darken, especially if some pulp tissue or older filling materials stayed in the crown of the tooth.
5. Internal resorption
Rarely, a tooth’s own cells begin breaking down the inside of the tooth. This can show as a pink spot. It needs prompt assessment.
6. Medication and development
Tetracycline antibiotics taken during childhood, or high fluoride levels while teeth are forming, can cause grey, brown or banded discolouration. These usually affect several teeth, not one.
How quickly does a tooth change colour after an injury?
It varies. Some teeth turn pinkish or grey within days of a hit. Others look normal for months or even years, then slowly darken as the nerve dies.
A real example: a patient in their 30s noticed a grey front tooth and couldn’t think why. Then they remembered taking a puck to the mouth at 16. The X-ray showed a small infection at the root tip, and a root canal plus internal bleaching brought the colour back close to its neighbours.
How serious is a grey tooth?
| Situation | Likely meaning | How urgent |
|---|---|---|
| Darkened weeks after a knock, no pain | Nerve injury, may recover or die | Book an exam soon |
| Grey for years, no symptoms | Likely a dead nerve | Book an exam, infection can develop silently |
| Dark tooth with a pimple on the gum | Infection draining from the root | See a dentist within days |
| Dark tooth with swelling or throbbing pain | Active infection or abscess | Same-day care |
| Pink spot on the tooth | Possible internal resorption | Prompt assessment |
| Grey shadow next to a large silver filling | Metal showing through | Routine visit |
Get urgent care if a dark tooth comes with facial swelling, fever, a bad taste or trouble swallowing. These can be signs of a spreading infection. Breathing problems need emergency medical care right away. This article is general information and doesn’t replace an assessment by a licensed dentist registered with the Royal College of Dental Surgeons of Ontario (RCDSO).
How does a dentist find out why a tooth is dark?
- History. Any past injury, pain, fillings or root canals on that tooth.
- Visual exam. Colour, cracks, fillings and the gum around the tooth.
- Vitality tests. Cold and electric tests check whether the nerve is still alive.
- Tap and bite tests. These show inflammation around the root.
- X-ray. Shows infection at the root tip, resorption, cracks or an old root canal.
- Diagnosis and options. The dentist explains whether the tooth needs treatment, monitoring or cosmetic care.
How is a dark tooth treated?
Root canal therapy
If the nerve is dead or infected, root canal therapy removes the damaged pulp, cleans the canals and seals them. This stops infection and keeps the natural tooth.
Internal bleaching
After a root canal, whitening gel can be placed inside the tooth, under a temporary filling, and changed over a few visits. This can lighten a tooth that regular whitening can’t reach.
Bonding or a veneer
If the colour can’t be fully corrected, tooth-coloured bonding or a porcelain veneer can cover the front surface and match the neighbouring teeth.
A crown
If the tooth is weakened by a large filling, decay or a root canal, a crown protects it and gives it a new, matching colour.
Replacing a silver filling
When the grey colour comes from an old amalgam filling, replacing it with a bonded, tooth-coloured filling often improves the colour a lot.
| Treatment | What it fixes | Best for |
|---|---|---|
| Root canal therapy | Dead or infected nerve | Any tooth with a non-vital nerve |
| Internal bleaching | Colour from inside | Root-treated front teeth |
| External whitening | Surface and general yellowing | Healthy teeth with stains |
| Bonding | Colour and small shape issues | Mild discolouration, quick fix |
| Porcelain veneer | Colour and shape on the front surface | Stubborn dark front teeth |
| Crown | Colour plus strength | Weak or heavily restored teeth |
What does root canal therapy for a dark tooth involve?
- Numbing. Local anesthetic makes the tooth comfortable, though dead teeth often feel little anyway.
- Access. A small opening is made in the back of a front tooth or the top of a back tooth.
- Cleaning. The damaged pulp is removed and the canals are cleaned and shaped.
- Sealing. The canals are filled with a rubber-like material and sealed.
- Colour plan. Internal bleaching may start at this stage or after healing.
- Final restoration. A bonded filling, veneer or crown completes the tooth.
Most root canals take 1 or 2 visits. Mild tenderness for a few days afterward is normal.
Can regular whitening fix a grey tooth?
Usually not on its own. Standard whitening works on stains in healthy enamel. A grey tooth caused by a dead nerve is stained from the inside, so internal bleaching or a restoration works better.
If your other teeth are also yellowed, whitening them first and then matching the dark tooth gives the most even result.
What about a child’s baby tooth turning grey?
This is common after a fall. A baby tooth may turn grey within days or weeks. Sometimes the colour fades as the tooth recovers. Sometimes the nerve dies.
Book a check with your dentist. Most grey baby teeth just need monitoring until they fall out naturally. Swelling, a gum boil or pain needs treatment, because infection could affect the adult tooth underneath.
Can you prevent a tooth from turning dark?
- Wear a mouth guard for hockey, basketball, soccer and other contact sports
- Get any knock to a tooth checked, even if it seems fine
- Treat cavities early, before they reach the nerve
- Replace old, leaking fillings
- Keep regular check-ups so changes in colour are spotted early
Athletic sports guards are one of the simplest ways to prevent the kind of injury that turns front teeth grey years later.
How long do colour fixes last?
Internal bleaching results can last many years, though some teeth slowly darken again and need a touch-up. Bonding usually lasts 3 to 7 years, porcelain veneers often 10 to 15 years or more, and crowns a similar length with good care.
What are the common myths about dark teeth?
- Myth: if a dark tooth doesn’t hurt, it’s fine. Dead nerves often cause no pain until infection develops.
- Myth: a grey tooth always has to come out. Most can be saved with root canal therapy and a cosmetic fix.
- Myth: whitening strips will even it out. Strips lighten surface stains and won’t reach staining inside the tooth.
- Myth: a dark tooth is just cosmetic. It can be a sign of nerve damage that needs treatment.
- Myth: root canal treatment is very painful. It’s done with local anesthetic and usually feels similar to a filling.
Why choose Bolton Park Dentistry?
Bolton Park Dentistry is a trusted family dentist in Bolton, offering complete care in a calm, welcoming environment designed to ease anxiety. We serve Bolton and the surrounding communities from 14 Parr Blvd Unit 5, Bolton, Ontario L7E 4H1.
We welcome new patients and offer same-day appointments when available for urgent needs, so a dark tooth with swelling doesn’t have to wait. Sedation options are available for nervous patients.
As a cosmetic dentist in Bolton, we also provide hygiene and preventive care, amalgam-free and bonded fillings, crowns, bridges, extractions, root canal therapy, implant restoration, porcelain veneers, teeth whitening, athletic sports guards, TMJ/TMD therapy, non-surgical gum therapy and free consultations for implants and braces.
Patients often tell us careful, gentle care is what makes us the top dentist in Bolton for them. Our dentists are registered with the Royal College of Dental Surgeons of Ontario (RCDSO). Call 647-496-2336, email reception@boltonparkdentistry.com, or visit boltonparkdentistry.com to book with a dentist in Bolton.
If your tooth is swollen or painful, call early and our emergency dental clinic in Bolton team will try to see you the same day. For colour concerns, patients often say our whitening and cosmetic care give them the best teeth whitening Bolton results they’ve had, and a natural match.
Frequently asked questions
Does a grey tooth mean it’s dead?
Often, but not always. A tooth can darken after an injury and partly recover. Vitality tests and an X-ray tell your dentist whether the nerve is still alive.
Can a dead tooth turn white again?
Yes, in many cases. After root canal therapy, internal bleaching can lighten the tooth. If that’s not enough, bonding, a veneer or a crown can match it to its neighbours.
How long can you leave a dead tooth?
It’s best not to leave it. A dead tooth can become infected at any time, even years later, so have it assessed and treated.
Why did my tooth turn grey after a filling?
A large silver filling can show through the enamel, or the nerve may have been irritated by deep decay. Your dentist can tell which with a few tests.
Is a grey tooth an emergency?
Not usually on its own. It becomes urgent if there’s swelling, pain, a gum boil or fever, which can signal infection.
Conclusion
A single dark or grey tooth usually means the nerve has been injured or has died.
Root canal therapy protects the tooth, and internal bleaching, veneers or crowns restore the colour.
Have any dark tooth checked by a licensed dentist, and seek prompt care if there’s swelling or pain.