A frenum (also known as a frenulum) in the oral cavity is a fold of tissue connecting moveable soft tissue such as the lips, cheeks or tongue to the fixed tissues next to the teeth and floor of the mouth. This fold of tissue can contain some muscle fibers as well.

The major frena in the mouth can be found in three locations. The first is the maxillary labial frenum located on the underside of the middle of the upper lip, connecting it to the gum tissue above and between the front two teeth on top. Another frenum is the mandibular labial frenum, which is located on underside of the lower lip connecting it to the gum tissue below and between the front two teeth on bottom. The third is the lingual frenum, which is found on the underside of the tongue connecting it to the floor of the mouth.

In most cases these frena do not adversely limit tongue function, or affect the teeth or their surrounding hard and soft tissues. However, there are situations where they do and a surgical procedure is required to alleviate these problems. A maxillary labial frenectomy is the most common one performed, and is considered when a large and ropey frenum is attached too close to the crowns of the teeth or extends too far towards the roof of the mouth. Issues with the maxillary frenum can cause space between the two front teeth, keeps the teeth apart, and can even affect the gums and bone between the front two teeth. A lingual frenectomy is considered when the lingual frenum attaches too far forward on the tongue and is impairing function including, speech, swallowing or eating.

When an abnormal frenal attachment is present, certain surgical procedures like a frenectomy to remove a portion of the frenum can be performed. This surgery prevents further tissue damage, allows for appropriate tooth movement and stability, and restores normal function.