Free gingival margin
The free gingival margin is the interface between the sulcular epithelium and the epithelium of the oral cavity. This interface exists at the most coronal point of the gingiva, otherwise known as the crest of the marginal gingiva.
Because the short part of gingiva existing above the height of the underlying Alveolar process of maxilla, known as the free gingiva, is not bound down to the periosteum that envelops the bone, it is moveable. However, due to the presence of gingival fibers such as the dentogingival and circular fibers, the free gingiva remains pulled up against the surface of the tooth unless being pushed away by, for example, a periodontal probe or the bristles of a toothbrush.