If a child bumps his baby tooth it may turn dark. It usually happens 2 to 3 weeks after an accident. The colour is usually grey or purple- like.
Whether it turns dark or not, doesnt always depend on the severity of the injury. However, if the tooth is displaced or knocked very loose at the time of the injury, there seems to be a greater chance of it turning dark. If the tooth doesnt turn dark after a month, it likely wont have any further problems.
Will the tooth ever lighten back up?
It can, but it takes a while. There is just not a good blood supply to the tooth. If the blood supply of the tooth has been damaged with displacement, it might not recover or lighten at all. However, most dark baby teeth do lighten back.
BUT remember, if it is a permanent tooth, then it is a whole new ball game!
A traumatized permanent tooth that turns dark usually means that the tooth is dead and will need a root canal treatment to save it. It will also need a porcelain crown after the root canal treatment to support the tooth structure and to get the colour to match the other teeth again.
How long will it take to lighten back up?
Baby teeth seem to take several months to lighten. Its like a bruise inside the tooth. Unlike a bruise on the skin, where there is a good blood supply, the tooth takes a longer amount of time to recover. Sometimes it will lighten to sort of a slight opaque look, which is barely noticeable. This is due to the canal inside the tooth closing up. It is kind of like a scar inside the tooth. If this happens then the tooth looks pretty good and is not likely to have any further problems.
Sometimes the tooth never lightens and stays dark. If no signs of infection or injury are present, then the tooth must just be observed. Often no need for treatment is necessary. An x-ray can be taken, if possible, to check for problems. In a few cases, the tooth can form an abscess due to the death of the pulp (nerve) inside the tooth. The body cant get into the tooth to heal the injured pulp. It is thus important to watch out for this.
If the baby tooth is dark and you dont like the look of it, then a filling on the front of the tooth can be done to hide the colour.
If an abscess (swelling or bump above the tooth with sometimes pus coming out) is present, the treatment at this stage is often to remove the baby tooth to prevent damage occurring to the permanent tooth.