If a single front tooth has turned grey, brown or darker than its neighbours, ordinary teeth whitening will not fix it. Standard whitening gel works on living teeth from the outside. A tooth that has darkened after a knock or a root canal is discoloured from the inside, so it needs a different approach called internal bleaching, also known as the walking bleach technique. Studies report an immediate success rate of around 89 percent, with most teeth still looking good years later, though some need a top-up over time.
Key takeaways
- Internal bleaching whitens a single dead or root-treated tooth from the inside, where external whitening cannot reach.
- It is for teeth that have darkened after trauma or a root canal, not for general yellowing of all your teeth.
- Immediate success is around 89 percent; results last well, though 10 to 40 percent of teeth need re-treatment over the following years.
- It is more conservative and cheaper than a crown or veneer, and keeps more natural tooth.
- The tooth needs a healthy, well-sealed root canal first; your dentist will check this before bleaching.
The one rule: the tooth must be non-vital and properly root-filled
Internal bleaching only suits a tooth that is non-vital, meaning the nerve has died or been removed, and that has a sound root canal filling. The dentist places the bleaching agent into the inside of the tooth, behind a protective barrier that shields the root, so the colour change comes from within. If the tooth still has a live nerve, or the root filling is leaking, that has to be sorted first. This is why a dead tooth is whitened differently from your other teeth, which respond to surface whitening.
How internal bleaching works, step by step
Step 1: Assess the tooth
The dentist checks that the tooth is non-vital, takes an X-ray to confirm the root canal is sound, and discusses the likely result. Trauma and nerve-death discolouration usually respond better than discolouration caused by old filling materials.
Step 2: Protect the root
A small protective barrier is placed inside the tooth over the top of the root filling. This stops the bleaching agent reaching the root and is the key safety step that reduces the risk of root resorption.
Step 3: Place the bleach and seal
A bleaching agent is sealed inside the tooth with a temporary filling. In the walking bleach method it is left to work over several days, which is where the name comes from. This is often repeated two or three times over a few weeks until the shade matches.
Step 4: Final restoration
Once the colour is right, the access hole is sealed with a permanent tooth-coloured filling. Your dentist may slightly over-lighten the tooth, because a small amount of rebound is normal.
How long does it last?
Results are generally good. Studies report success of 75 percent or more after one to five years, but 10 to 40 percent of teeth need re-treatment over a longer period as some colour returns. A repeat course is usually straightforward. If a tooth keeps relapsing or is also weak or heavily filled, a veneer or crown may be the more durable answer.
Risks to know about
The main risk is cervical root resorption, where the root surface near the gum starts to break down. It is uncommon when a proper internal barrier is used and modern agents are chosen, which is why technique matters and why this is a dental procedure rather than a home one. Mild, short-lived sensitivity can also occur.
Internal bleaching vs the alternatives
| Option | How conservative | General cost range (AUD) | Best for |
|---|---|---|---|
| Internal bleaching | Most conservative, keeps natural tooth | Lower | A single dark, root-treated tooth |
| Composite veneer | Some tooth preparation | Moderate | Dark tooth that also needs reshaping |
| Porcelain crown or veneer | Most tooth removed | Highest | Dark tooth that is weak or heavily filled |
These are general comparisons, not a quote. The team at Lumi Dental does not list its own prices here; for current pricing see our current deals page or ask for a written quote.
Frequently asked questions
Can you whiten a dead tooth?
Yes. A dead or root-treated tooth is whitened from the inside with internal bleaching, because surface whitening gel cannot lighten internal discolouration.
Why is my one tooth grey?
A single grey or dark tooth usually means the nerve has died, often after a knock years earlier, or after a root canal. The breakdown products from the nerve stain the tooth from within.
Does internal bleaching damage the tooth?
When done with a proper internal protective barrier it is considered safe and conservative. The main rare risk is root resorption, which good technique minimises.
How many visits does it take?
Often two to three short visits over a few weeks, depending on how the tooth responds, plus the final sealing visit.
Will it match my other teeth?
The aim is a close match. If your other teeth are also discoloured, you may want to whiten them first so the shades line up.
If one tooth has gone darker than the rest, the team at Lumi Dental in Melrose Park can check whether internal bleaching is suitable. Related reading: root canal vs extraction, white spots on teeth, crowns vs veneers, and how long whitening lasts. You can also visit our teeth whitening page.
