Most of us at some point have noticed someone with a dark tooth like the image below, or perhaps your own tooth looks similar to this one. What causes one tooth to darken like this? Most often it’s because the nerve within the tooth is losing its blood supply, creating a “dead nerve”—what dentists refer to as a “necrotic pulp.”
The loss of blood supply to the nerve is often caused by some sort of trauma to the tooth, for instance, a blow to the face. If a tooth gets pushed upward into the bone in this traumatic event, the delicate blood vessels, which enter the tooth at the root tip, may get pinched off or damaged, causing the nerve tissue to die. (Picture a garden hose getting kinked or severed.) As the nerve tissue dies, dark pigments from bacteria living within the necrotic pulp tissue stain the tooth from within. Sometimes this darkening of the tooth happens within weeks after a traumatic injury. However, it may happen a considerable time after a traumatic event. In fact, sometimes a person may not even remember the accident that caused the trauma.
Another instance of a tooth darkening is after root canal treatment. When a root canal is done, sometimes there is residual nerve tissue that can’t be removed from the tooth. Just like in the above example, this residual necrotic tissue causes dark staining within the tooth.
How do we make the tooth white again in such a case? If the tooth has not had root canal treatment already then a root canal is the first step. Once the root canal has been completed, a strong bleaching solution is placed into the hollow space within the crown of the tooth; this space was created when the root canal was completed. A temporary filling is placed in the back of the tooth to keep the bleach sealed inside the tooth. The “bleach,” (hydrogen peroxide), is left inside the tooth for a day or two. Noticeable whitening of the tooth usually takes place in the first twenty-four hours. A changing of the bleach solution may be necessary if additional whitening is desired. Once the tooth has been whitened, the hollow portion of the tooth is filled with white filling material.
This particular tooth is one I treated in 2007. The color has remained stable ever since.