When a tooth dies, it means that the pulp inside the tooth, which contains nerves and blood vessels, has become infected or damaged to the point where it can no longer survive. This can happen due to various reasons, including severe decay, gum disease, or trauma, such as a tooth being knocked. A dead tooth can lead to pain, discolouration, and swelling if left untreated.

When a tooth that has undergone root canal treatment (endodontic therapy) turns grey or discolored, it is typically due to changes that occur within the tooth's structure as a result of the treatment. This discoloration is often associated with the loss of vitality in the tooth and changes in its internal tissues.

When a tooth dies, it means that the pulp inside the tooth, which contains nerves and blood vessels, has become infected or damaged to the point where it can no longer survive. This can happen due to various reasons, including severe decay, gum disease, or trauma, such as a tooth being knocked. A dead tooth can lead to pain, discolouration, and swelling if left untreated.