She covered her mouth every time she smiled. It had become a habit — her hand would come up before anyone could see her teeth. Her front tooth had turned gray after a root canal years ago. She’d learned to live with it. Laughing with friends, taking photos with her kids, job interviews — she always found a way to hide it.
When she came into our Torrance office, the first thing she told me was, “I just want to smile without thinking about it.”
I told her we could probably fix it. And we wouldn’t need a crown or a veneer to do it.
Why Does a Tooth Turn Dark After a Root Canal?
This is actually really common. A lot of people notice their tooth getting darker months or even years after a root canal. And they wonder — what went wrong?
Usually, nothing went wrong. Here’s what happens.
During a root canal, the nerve and blood supply inside the tooth are removed. But sometimes, tiny amounts of blood and tissue get left behind in the small spaces inside the tooth. Over time, those leftover blood products break down. They seep into the inner walls of the tooth. And the tooth starts to change color — usually to a gray or brownish shade.
A few things can make it worse:
- Blood breakdown products — When blood sits inside a tooth for a long time, the iron in it stains the tooth from the inside
- Old filling materials — Some older root canal materials can cause discoloration on their own
- Incomplete cleaning — If the pulp chamber wasn’t fully cleaned out during the original root canal, leftover tissue breaks down and darkens the tooth
The stain is coming from inside the tooth. That’s why regular whitening strips and trays don’t work on it. The bleach can’t reach the stain because it’s behind the enamel.
What Is Internal Bleaching?
Internal bleaching is exactly what it sounds like. Instead of putting bleach on the outside of your tooth, we put it inside.
It’s sometimes called the “walking bleach technique” because you literally walk around with the bleaching agent sealed inside your tooth for about a week. The bleach works slowly from the inside out, lightening the stain that regular whitening can’t touch.
It’s one of my favorite procedures to do because the results can be pretty dramatic — and it’s about as conservative as it gets. We’re not grinding down your tooth. We’re not covering it up. We’re just cleaning up the color from within.
Good to know: Internal bleaching only works on teeth that have already had a root canal. The nerve has to be gone first. You’d never do this on a healthy, living tooth.
How Does Internal Bleaching Work? Step by Step
The process is simple. Here’s what a typical visit looks like at our office:
Visit 1: Placing the Bleach
- Open the access — I make a small opening in the back of the tooth (or reopen the existing one from your root canal)
- Protect the root filling — A protective barrier goes over the root canal filling so the bleach stays in the right spot
- Place the bleaching agent — Sodium perborate (a safe, slow-release bleaching material) gets packed into the hollow chamber inside the tooth
- Seal it up — A temporary filling closes everything off
That’s it. You go home. The bleach does its thing over the next 5 to 7 days.
Visit 2: Check the Result
You come back about a week later. I open it up, clean out the old bleach, and we take a look. If the color matches your other teeth — great, we’re done. If it needs a little more, I pack in fresh bleaching material and we do another round.
Visit 3 (If Needed): Final Check and Seal
Most teeth need 1 to 3 visits spread over 2 to 3 weeks. Once we’re happy with the shade, I place a permanent tooth-colored filling and you’re all set.
The whole process is about as low-key as dental treatment gets.
Does Internal Bleaching Hurt?
Nope. The tooth has already had a root canal, which means the nerve is gone. There’s nothing in there to feel pain. Most patients don’t even need numbing for this. You’ll sit in the chair, I’ll work on the tooth for maybe 20 minutes, and you won’t feel a thing.
No shots. No drilling into anything sensitive. It’s honestly one of the most comfortable procedures we do here in Torrance.
What Kind of Results Can You Expect?
Most teeth lighten by 2 to 4 shades. Some get a near-perfect match to the surrounding teeth. It depends on a few things — how long the tooth has been dark, what caused the stain, and how deeply the discoloration has set in.
Newer discoloration tends to respond better. A tooth that turned gray a few months after a root canal will usually bleach out nicely. A tooth that’s been dark for 10+ years? It can still improve a lot, but getting an exact match is harder.
I actually have a case study on our site showing a 42-year-old patient with gray discoloration that had been there for several years. After one week of internal bleaching with sodium perborate, the gray tone was gone. There was still a slight yellow undertone — which is typical for older stains — but the overall result was a big improvement. She was happy, and we avoided any need for a crown or veneer.
Real talk: I always set honest expectations. Most patients see a big improvement. Some get a perfect match. A few get a “good but not ideal” result, especially with older stains. But even in those cases, the tooth looks way better than it did before — and we haven’t touched the outside of the tooth at all.
Internal Bleaching vs. Veneer vs. Crown
If you’ve got a dark tooth, you’ve probably looked into veneers and crowns. Here’s how they compare:
Internal bleaching:
- Cost is a fraction of a veneer or crown
- No tooth structure is removed
- Takes 1-3 short visits
- If the color fades years later, you can just do it again
- Works best on teeth that are otherwise healthy and intact
Veneer:
- Requires shaving down the front of the tooth
- More expensive
- Looks great, but it’s permanent — the tooth always needs a veneer after that
- Better option if the tooth also has chips, cracks, or shape issues
Crown:
- Requires removing tooth structure all the way around
- Most expensive option
- Best for teeth that are already weakened and need structural support
- Overkill if the only problem is color
My approach? Always try the least invasive option first. If internal bleaching can fix the color, there’s no reason to grind down a perfectly good tooth for a veneer or crown. You can always do more later if needed. But you can’t undo a crown.
When Internal Bleaching Might Not Work
I want to be straight with you. Internal bleaching is great, but it’s not for every situation.
It may not work well if:
- The discoloration is from tetracycline antibiotics — This type of staining is deep and resistant to bleaching agents
- The tooth has external root resorption — Bleaching could make this worse, so we need to rule it out first
- The root canal filling is very old or failing — Sometimes the root canal itself needs to be redone before we can safely bleach
- The tooth needs a crown anyway — If the tooth is weak or heavily filled, a crown might be the smarter move since it addresses both strength and color
During your consultation, I’ll take a close look and let you know if you’re a good candidate. No pressure, no upsell. Just an honest answer.
Ready to Fix That Dark Tooth?
If you’ve been hiding a dark tooth for months or years, internal bleaching might be the simple fix you didn’t know existed. It’s quick, it’s comfortable, and it works for most people.
Patients come to our Torrance office from all over the South Bay for this — Redondo Beach, Palos Verdes, Manhattan Beach, Gardena, Carson. It’s a short visit, and you leave the same day with the bleach already working.
Call (310) 378-8342 to schedule a consultation at Phan Endodontic Partners. We’ll take a look at your tooth, talk about what’s realistic, and get you smiling again — no hand in front of your face required.