Teeth are attached to the surrounding and supporting alveolar bone by periodontal ligament (PDL) fibers; these fibers run from the bone into the cementum that naturally exists on the entire root surface of teeth.
The supracrestal attachment apparatus is composed of two layers: the coronal junctional epithelium and the more apical gingival connective tissue fibers.
[1] The two layers together form the thickness of the gingival tissue, and this dimension is termed the biologic width.
Clinical attachment loss is a sign of destructive (physiologically irreversible) periodontal disease.
Connective tissue attachment loss refers to the pathological detachment of collagen fibers from cemental surface with the concomitant apical migration of the junctional or pocket epithelium onto the root surface.