Mucogingival junction

A mucogingival junction is a feature which is located on the intraoral mucosa. The mucosa which is present on the cheeks and on the floor of the mouth is freely moveable and more fragile. In contrast, the mucosa which surrounds the teeth and is on the palate of the mouth is more firm and contains keratin (keratinized). Being keratinized makes the cells tougher and more structurally sturdy. The area in the mouth where these two different types of tissue meets is called a mucogingival junction.

There are three mucogingival junctions present inside the mouth which are summarized below:

• Facial of the maxilla – the maxilla is the upper fixed jawbone. Facial refers to the side adjacent to or which faces towards the inside of the lips
• Facial of the mandible – the mandible is the moveable lower jawbone which sits below the maxilla
• Lingual of the mandible – lingual refers to the side which is adjacent to the tongue

The palatal gingiva of the maxilla is continuous with the tissue of the palate. This is bound down to the palatal bones. Due to the fact that the palate does not contain any freely moveable alveolar mucosa, it does not contain a mucogingival junction.

Clinical Relevance

The mucogingival junction is clinically import because it is needed to measure the attached gingiva width. Attached gingiva is important because it is tightly secured to the underlying alveolar bone and provides the mucosa protection during use such as chewing. Without the attached gingiva, the freely moveable alveolar mucosa would experience trauma when patients performed daily activities such as eating and brushing their teeth.

The width of the attached tissue is vital as if corresponds to an increased level of protection from trauma or insults. When the mucogingival junction is used as the reference point of demarcation between the apical borders of the attached gingiva, a periodontal probe can be inserted in the gingival sulcus to measure the amount of keratinized gingiva coronal to the mucogingival junction which is attached to the underlying bone. The gingival sulcus depth, which is determined by the depth where the probe enters the sulcus, does not attach to the bone. As a result, it is excluded when the keratinized tissue’s total height is measured. In cases where the probe enters the sulcus and descends in line with or above the mucogingival junction, the area is classified as a mucogingival defect.

If the entire height of the keratinized gingiva, from the free gingival margin to the mucogingival junction, is 8 mm, and the probing depth on the tooth at that particular location is 2 mm, the attached gingiva width is 6 mm.

The area is classified as a mucogingival defect if the probe can enter the sulcus and descend up to or go beyond the mucogingival junction.

Mucogingival Conditions

A mucogingival condition is the altered relationship between the mucogingival junction and gingival margin. Mucogingival conditions are typically associated with progressive gum recession or those which do not allow for controlled inflammation. In addition to the probing depths which extend beyond the mucogingival junction, other mucogingival conditions include gingival recession, and missing keratinized gingiva. The defects can occur from trauma to the tissue through the use of a toothbrush. People who have a thinner profile periodontium also tend to be more prone to gingival recession than those with a thicker periodontium.