After an accident that included impact trauma to the jaw, you should always have your teeth checked out by your dentist. It's easy to dismiss an accident like this if there's no obvious damage to your teeth, but sometimes that damage doesn't show up until later—when a tooth rapidly changes colour.
A bruised tooth can be several different colours—which may change as the bruising progresses. Bruising can start as a pink hue, become red and progress to a blue, which then becomes darker. It's an alarming sight, and it may be accompanied by discomfort and sensitivity or even a strong toothache. However, the change in colour might be the only sign that something's amiss.
Something clearly is wrong with the tooth, and the issue is at the very centre of its structure, where the pulp chamber is found. This chamber is where the tooth's pulp (or nerve) is located. This is the tooth's living tissue, and the impact trauma has caused your pulp to bruise. It has become inflamed, and the resulting colour change is so prominent that it can be seen through the tooth's external layers (with your dental enamel being partially translucent). Your bruising may subside without serious incident. However, only a dentist can tell for sure.
Make an urgent appointment with your dentist. Their priority is to save the tooth, and the first step is a pulp vitality test. Using thermal or electrical testing devices, your dentist assesses blood flow to the pulp. The confirmation of this flow, along with its strength, helps your dentist to determine whether your dental pulp is likely to survive its impact trauma. If the results of your pulp vitality test are encouraging, no further action is needed other than a follow-up appointment.
Even when your dental pulp recovers, its inflammation can discolour the internal walls of the tooth's pulp chamber. This cannot be removed with external bleaching, so your follow-up treatment for a bruised tooth can involve minor cosmetic work to conceal the discolouration. This may require a dental veneer or teeth bonding. But what if the impact to your tooth was so severe that your dental pulp won't survive?
Discouraging results from your pulp vitality test can lead to root canal treatment, which is the outright removal of your damaged dental pulp. The tooth will remain strong and intact, even without its pulp. The empty pulp chamber is cleaned and then packed with latex before the tooth is sealed (with a filling and/or a dental crown).
When a tooth rapidly changes colour after an accident, you need to see your dentist quickly. Contact your dentist for more information.