Dead teeth will change colors because of the decomposition of blood from within the tooth. The color change is not immediately noticeable because it gradually happens over many years.
It will become a cosmetic concern at some point in your life and you will want to address it.
Color change mechanism
Most commonly, the discoloration of dead teeth is due to the intracoronal decomposition of blood. Yes, the pulp chamber contains not only the nerves but the blood supply which provides it nutrients.
A similar phenomenon occurs to the human body such as in the first stage of death, pallor mortis. The only exception is that the color change is isolated to the dentition since only the tooth has died while the rest of the body is still alive.
Decomposition of blood
According to a study in the journal of operative dentistry, the reason for non-vital teeth to change colors is because the blood breaks down after death. The researchers referenced a textbook by Drs Walton and Torabinejad called Principles and Practices of Endodontics for the etiology of this phenomenon.
Essentially, when teeth are still alive, the apices of the root is connected to the rest of our body's blood supply. That is literally how it receives nutrient. However, when the tooth dies, the nerve and the blood supply from within the tooth will start to degrade and break down.
After enough time has passed, the degradation of the blood vessels will cut the tooth off from the rest of the blood supply. The tooth will become weakened since it is no longer receiving any nutrients from our body.
Of course, the most visible result of this is tooth discoloration which can be incredibly unaesthetic. The beginning stages of it may be mild but the later stages can be very severe.
Pallor mortis
A very similar phenomenon to dead teeth discoloration is pallor mortis, which is the first stage of death. As you may know, when people die their body starts to lose color very quickly and start to look grey.
The drainage of color from a body is indicative of death. After all, the expression "deathly pale" is used to describe those who aren't in good health.
Now isn't it interesting that it can happen to your tooth but in isolation?
What color it changes to
A dead tooth can be easily distinguished from vital teeth due to the severe discoloration that accompanies this condition. These teeth often look much darker than their adjacent non-dead neighbors.
Non-vital tooth colors:
Black
Grey
Dark yellow
The color may differ from individual to individual but a common trait is that they will be darker than the teeth next to them. Therefore if one of your teeth looks like a different color from the rest of your mouth, you may have a non-vital tooth.
How long it takes to change colors
Teeth don't change colors immediately after dying because it is a slow gradual process. Oftentimes it takes years or even a decade before the tooth has darken enough for the patient to even notice it. That is literally how slow the color change is once your tooth has died.
As a matter of fact, we often have to point out to the patient that one of their teeth is even discolored. Patients typically will not realize it until it gets severely discolored.
Treatment
Once the tooth has become discolored, it can be whitened chemically or prosthetically by masking the color with porcelain. Typically, the former is attempted first since it is the least invasive option but if that fails then the latter can be tried.
Teeth whitening
As you may have guessed, teeth can be whitened or bleached to a lighter shade by using hydrogen peroxide. The peroxide will chemically oxidize the discoloration by diffusing through it and converting the double conjugated bonds to single bonds. This treatment can be done on the teeth externally, internally, or by using a combination of both techniques.
The most common form of whitening which you're probably familiar with is actually external whitening. That is when the bleaching gel is placed on the exterior of the tooth and it whitens it from outside in.
However, for dead teeth external whitening is often inadequate to fully brighten the tooth back to its original shade. This condition requires a combination of external and internal whitening. The process of whitening the tooth internally requires placing the bleaching gel inside of the tooth's pulp chamber. This whitens the tooth from the inside out.
Note: Internal bleaching requires the tooth to be root canal treated first.
Prosthetic color change
If chemically changing the color of the tooth fails, the next best option would be to change it prosthetically. This would involve crowning it or putting a veneer over it.
The crown will typically mask the color of your dead tooth fairly well, especially the PFM or zirconia crowns since they are more opaque. The only downside is that you need to prepare the tooth for the cap, which involves shaving down the tooth to create enough space for it.
A veneer is also an option to change the color. It is more conservative than a crown in that it only requires shaving down the front half of the tooth while leaving the tongue side untouched.
The downside is that the porcelain for veneers tend to be very thin so the color underneath may show through. To counteract this, the lab technician may need to plaque a color blocking layer prior to making the porcelain.
Takeaway
A dead tooth changes colors because it has died. The process is due to the break down of the blood vessels from within the tooth. It is very similar to how a dead body will become drained and devoid of color.
The good news is that the color is correctable with cosmetic procedures from your dentist. You can give at home whitening a try first such as with a whitening pen and if that doesn't work then you can try covering it with a porcelain restoration.
