A mucogingival junction is an anatomical feature found on the intraoral mucosa. The mucosa of the cheeks and floor of the mouth are freely moveable and fragile, whereas the mucosa around the teeth and on the palate are firm and

keratinized Keratin () is one of a family of structural fibrous proteins also known as ''scleroproteins''. Alpha-keratin (α-keratin) is a type of keratin found in vertebrates. It is the key structural material making up scales, hair, nails, feathers, h ...

. Where the two tissue types meet is known as a mucogingival junction. There are three mucogingival junctions: on the

facial A facial is a family of skin care treatments for the face, including steam, exfoliation (physical and chemical), extraction, creams, lotions, facial masks, peels, and massage. They are normally performed in beauty salons, but are also a comm ...

of the

maxilla The maxilla (plural: ''maxillae'' ) in vertebrates is the upper fixed (not fixed in Neopterygii) bone of the jaw formed from the fusion of two maxillary bones. In humans, the upper jaw includes the hard palate in the front of the mouth. T ...

and on both the facial and lingual of the

mandible In anatomy, the mandible, lower jaw or jawbone is the largest, strongest and lowest bone in the human facial skeleton. It forms the lower jaw and holds the lower teeth in place. The mandible sits beneath the maxilla. It is the only movable bone ...

. The

palatal The palate () is the roof of the mouth in humans and other mammals. It separates the oral cavity from the nasal cavity. A similar structure is found in crocodilians, but in most other tetrapods, the oral and nasal cavities are not truly separ ...

gingiva of the maxilla is continuous with the tissue of the

palate The palate () is the roof of the mouth in humans and other mammals. It separates the oral cavity from the nasal cavity. A similar structure is found in crocodilians, but in most other tetrapods, the oral and nasal cavities are not truly separ ...

, which is bound down to the palatal bones. Because the palate is devoid of freely moveable

alveolar mucosa The oral mucosa is the mucous membrane lining the inside of the mouth. It comprises stratified squamous epithelium, termed "oral epithelium", and an underlying connective tissue termed '' lamina propria''. The oral cavity has sometimes been des ...

, there is no mucogingival junction.Carranza's Clinical Periodontology, W.B. Saunders 2002, page 17.

Clinical importance

The clinical importance of the mucogingival junction is in measuring the width of attached gingiva. Attached gingiva is important because it is bound very tightly to the underlying

alveolar bone The alveolar process () or alveolar bone is the thickened ridge of bone that contains the tooth sockets on the jaw bones (in humans, the maxilla and the mandible). The structures are covered by gums as part of the oral cavity. The synonymous t ...

and provides protection to the mucosa during functional use of the structures of the oral cavity during function, such as

chewing Chewing or mastication is the process by which food is crushed and ground by teeth. It is the first step of digestion, and it increases the surface area of foods to allow a more efficient break down by enzymes. During the mastication process, th ...

. Without attached gingiva, the freely moveable alveolar mucosa, being more fragile, would suffer injury during eating and cleansing activities, such as brushing of the

teeth A tooth ( : teeth) is a hard, calcified structure found in the jaws (or mouths) of many vertebrates and used to break down food. Some animals, particularly carnivores and omnivores, also use teeth to help with capturing or wounding prey, t ...

. The width of attached tissue is critical, because the more there is available provides a greater sense of protection against the aforementioned insults to the tissue. Using the mucogingival junction as the boundary demarcating the

apical Apical means "pertaining to an apex". It may refer to: *Apical ancestor, refers to the last common ancestor of an entire group, such as a species (biology) or a clan (anthropology) *Apical (anatomy), an anatomical term of location for features loc ...

border of the attached gingiva, a

periodontal probe A periodontal probe is an instrument in dentistry commonly used in the dental armamentarium. It is usually long, thin, and blunted at the end. The primary purpose of a periodontal probe is to measure pocket depths around a tooth in order to establ ...

is inserted into the

gingival sulcus The gingival sulcus is an area of potential space between a tooth and the surrounding gingival tissue and is lined by sulcular epithelium. The depth of the sulcus (Latin for ''groove'') is bounded by two entities: apically by the gingival ...

to measure how much of the

gingiva coronal to the mucogingival junction is in fact attached to the underlying bone. The depth of the gingival sulcus, determined by the depth to which the probe enters the sulcus, is not attached to the underlying bone, and is subtracted from the total height of the keratinized tissue. Thus, if the entire height of the keratinized gingiva, from the

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 s ...

to the mucogingival junction is 8 mm, and the probing depth on the

tooth A tooth ( : teeth) is a hard, calcified structure found in the jaws (or mouths) of many vertebrates and used to break down food. Some animals, particularly carnivores and omnivores, also use teeth to help with capturing or wounding prey, t ...

at that location is 2 mm, the effective width of attached gingiva is 6 mm. If the probe enters the sulcus and can descend up to or beyond the mucogingival junction, this is called a mucogingival defect.

References

Gingiva {{dentistry-stub