Intrinsic staining of teeth is usually permanent. When the whole tooth is discoloured, the pulp is almost always irreparably damaged.
Initially, the tooth can appear pink as the blood seeps into the microscopic tubules within the dentine. As the blood cells break down, the colour will usually change to purple and eventually grey (similar to how a bruise changes colour after the initial injury, prior to healing). With time, the dead (necrotic) pulp will become infected and leak into the bone surrounding the tip of the root, causing an abscess or granuloma. These teeth are often painful so it is recommended that they receive Root canal treatments or are extracted.
Filling in molar affected by decay
Discolouration can occasionally appear on a small portion of the tooth. Localised, internal bleeding will usually lead to the death of the tooth but, occasionally, the pulp does recover. With this in mind, the affected teeth should be monitored and assessed with regular x-rays.