Periodontal Anatomy – Mucogingival junction
A mucogingival junction is located on the intraoral mucosa. The mucosa found on the cheeks and base of the mouth are fragile and freely moveable. However, the mucosa which is on the palate and surrounds the teeth is keratinized and firm. When something is described as keratinized, it means the cells are tougher and sturdier. The location where these two types of tissue meet is referred to as a mucogingival junction.
The following three mucogingival junctions exist inside the mouth:
- Facial of the maxilla: the maxilla is the upper jawbone which is fixed. The term facial is used to describe the side adjacent to or that which faces towards the inside of the lips
- Facial of the mandible: the mandible is the lower jawbone which is moveable. It sits directly below the maxilla in the mouth
- Lingual of the mandible: the term lingual is used to describe the side which is adjacent to the tongue
The palatal gingiva of the maxilla, or the upper jaw, is continuous with the tissue of the palate. The palate is secured down to the palatal bones. Because the palate does not contain freely moveable alveolar mucosa, it does not contain a mucogingival junction.
The clinical relevance of the mucogingival junction is in the measurement of the attached gingiva’s width. The attached gingiva is especially important because it is tightly bound to the underlying alveolar bone. It provides protection to the mucosa during the functional use of the structures, such as chewing and brushing the teeth. If the attached gingiva were not present, the freely moveable alveolar mucosa, because it is more fragile, would experience injuries while completing these routine activities.
The attached tissue’s width is especially important, as the surplus of this tissue provides additional protection against these potential insults to the tissue. Using the mucogingival junction as the boundary to indicate the apical border of the attached gingiva, a periodontal probe will be inserted into the gingival sulcus. This is done to measure the amount of the keratinized gingiva coronal to the mucogingival junction is indeed attached to the underlying bone. The depth of the gingival sulcus, which is determined by the depth of how far the probe is able to enter the sulcus, is not attached to the underlying bone. It is then subtracted from the overall height of the keratinized tissue.
As an example, if the overall height of the keratinized gingiva, starting from the free gingival margin down to the mucogingival junction is 8 mm, and the probing depth at that specific location is 2 mm, the width of the attached gingiva is actually 6 mm.
In cases where the probe is able to enter the sulcus and descend up to or past the mucogingival junction, this is a mucogingival defect.
A mucogingival condition occurs when there is an altered relationship between the mucogingival junction and the gingival margin. In most cases, mucogingival conditions are associated with progressive gum recession or cases which do not allow for controlled inflammation. Combined with the probing depths which extend past the mucogingival junction, other mucogingival conditions can include gingival recession and missing keratinized gingiva. These types of defects can occur as a result of trauma to the tissue through the incorrect or aggressive use of a toothbrush. Patients with a thinner profile periodontium have a tendency to be more prone to gingival recession compared to patients who have a thicker periodontium.