“A tooth has two parts, a head and a tail, one known as the crown and one known as the root, with the cervical part of the tooth in between.
Normally it is the thicker crown that grows out and is exposed in the mouth to perform functions such as chewing, and the thinner and longer root that is buried in the alveolar bone and covered by the gums. When the alveolar bone is resorbed, the roots of the teeth are exposed and can be seen directly from the mouth. Periodontal disease causes the roots to become exposed, causing gaps between the teeth to widen and a ‘black triangle’ to appear, which is aesthetically displeasing.”