The gingival margin(F) is the most coronal point of the gingiva, depicted as the zenith of the pink hill in this diagram. To the left lies the sulcular epithelium within the gingival sulcus (G), and to the right lies the oral epithelium (E).
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.
Gingival retraction or gingival recession is when there is lateral movement of the gingival margin away from the tooth surface. It is usually termed gingival retraction as an intentional procedure, and in such cases it is performed by mechanical, chemical, or electrical means in order to perform certain dental surgery procedures. It is usually referred to as gingival recession as a spontaneous or non-intentional presentation, and in such cases it may indicate an underlying inflammation, a pocket formation or displacement of the marginal gingivae away from the tooth by mechanical, chemical, or surgical means. It may expose the roots of the teeth, similarly to gingival recession.