If there is a darker tooth between the white teeth than the other teeth, this tooth is usually a tooth that has lost its vitality or has undergone root canal treatment. The color of the tooth can be lightened with the whitening process to be performed on a single tooth. A whitening agent is placed inside the tooth by the dentist and the whitening process takes place after 1-2 days. And the process is finished with filling. The result is usually excellent and irreversible.