One front tooth slowly turning gray, brown or darker than the ones beside it is something we see often, and it usually has a story behind it: a ball to the mouth, a fall, a hit years ago that nobody thought much about at the time. The color is the tooth telling you something changed on the inside.
The short answer: a single tooth that turns gray usually means the nerve inside has died, most often after an injury. It may never hurt, but it still needs to be checked, because a dead nerve can lead to infection at the root. The color can usually be fixed, either by bleaching the tooth from the inside after a root canal, or with a veneer or a crown, depending on how much of the tooth is left.
Why one tooth turns gray
When a tooth is hit hard enough, the blood vessels feeding the nerve can be damaged. If the nerve dies, its blood and tissue break down inside the tooth, and those breakdown products work their way into the dentin, the layer under the enamel. The tooth darkens from the inside out, sometimes over weeks, sometimes over years.
Injury is the most common cause, but not the only one. In a study of 255 discolored teeth that were bleached from the inside, trauma was behind 59% of them, earlier dental work 24%, a nerve that died for other reasons 14%, and a canal that had filled in with calcium about 4%.
Abbott P, Heah SY. Internal bleaching of teeth: an analysis of 255 teeth. Aust Dent J. 2009;54(4):326-333.
This is different from teeth that are dark all over, or in bands across the whole smile. That pattern usually comes from something during childhood, like tetracycline staining, and it’s handled differently.
Is a gray tooth always dead?
Usually, but not always, especially right after an injury. A tooth can darken soon after a knock and then lighten again if its blood supply recovers. That’s why a recently injured tooth is watched and tested over time rather than treated on the first day.
To tell, we compare the tooth with its neighbors: cold, to see whether the nerve still responds, tapping, to check the tissue around the root, and X-rays to look for infection at the root tip. How we test a tooth that may need a root canal.
Heithersay GS, Hirsch RS. Tooth discoloration and resolution following a luxation injury. Quintessence Int. 1993;24(9):669-676. A report of two injured teeth whose color resolved.
Why a gray tooth needs attention even if it doesn’t hurt
Most gray teeth don’t hurt, which is why people leave them alone for years. But a nerve that has died inside a tooth can become infected at the root tip, often without any pain, and that infection can slowly damage the bone around the root. A tooth whose nerve has died usually needs a root canal, which an endodontist does for us. The other signs that point to a problem inside the tooth.
How the color gets fixed
There are three ways to fix a dark tooth, and which one fits depends mostly on how much of the tooth is left and whether the teeth around it need work too.
- Bleaching from the inside. After the root canal, a bleaching agent is placed inside the tooth, sealed in, and changed every few days until the color matches. It’s the most conservative option, because nothing is cut off the outside of the tooth. We’ve done it ourselves, but we’ve had better results when the endodontist does it after the root canal and an evaluation, so in general we refer it.
- A veneer. A thin layer of porcelain bonded to the front of the tooth. It makes sense when the tooth is sound but the color won’t fully bleach out, or when the teeth beside it are being improved at the same time. How veneers work here.
- A crown. When the tooth is broken down, from the injury or from old fillings, a crown covers and protects what’s left and fixes the color at the same time. How crowns work here.
What about regular whitening? Once in a while, the darkness on one tooth is only surface stain. Then bleaching just that tooth can help, with gel placed only in that tooth’s spot in a whitening tray. But when the color comes from inside the tooth, as it does when the nerve has died, bleaching from the outside probably won’t lighten it, and whitening the others can make the dark one stand out more. Why some teeth won’t get white.
How long bleaching from the inside lasts
It almost always works at first. Some of the color often creeps back over the years, and patients notice it. Here’s what the long-term studies found:
- At five years, 79% of bleached teeth were still a success in one study. In another, color crept back in 15 of 25 teeth, but by no more than a few shades.
- At 16 years, about two-thirds had held their color and about one-third had darkened noticeably.
- At 25 years, 85% still matched the teeth beside them in one group of 40 patients.
How well the tooth is sealed afterward matters: in the study of 255 teeth, the color held best when the opening was sealed with tooth-colored filling material. Gray and light yellow teeth bleach most predictably. Very dark teeth take more rounds.
Glockner K, et al. Five-year follow-up of internal bleaching. Braz Dent J. 1999;10(2):105-110. Deliperi S. Clinical evaluation of nonvital tooth whitening and composite resin restorations: five-year results. Eur J Esthet Dent. 2008;3(2):148-159. Amato M, et al. Bleaching teeth treated endodontically: long-term evaluation of a case series. J Endod. 2006;32(4):376-378. Amato A, et al. In-office and walking bleach dental treatments on endodontically-treated teeth: 25 years follow-up. Minerva Stomatol. 2018;67(6):225-230. Abbott P, Heah SY. Aust Dent J. 2009;54(4):326-333.
How it works here
We start by finding out what’s going on: whether the nerve is alive, whether there’s infection at the root, and how much of the tooth is left. If the tooth needs a root canal, an endodontist does it, and usually handles the internal bleaching afterward. If a veneer or crown is the better answer, especially when neighboring teeth need work too, we plan and make it here, and we plan the whole sequence with you before anything starts.
Where to start
If one of your teeth has turned gray or darker than the others, call 702-734-0776. If you remember an injury to that tooth, even years ago, tell us. If a tooth was just knocked loose or out, that’s urgent. What to do in a dental emergency.
General education, and not a substitute for an exam.