In health, there are two types of gum tissues that surround the tooth. The part that is around the neck of the tooth is firmly attached to the tooth and underlying bone, and is called attached gingiva. The attached gingiva is immovable and tough and deflects food as it hits the gum. Below the attached gingiva is looser gum, or alveolar mucosa. This tissue contains muscle and is flexible to allow movement of the cheeks and lips. The muscles in the alveolar mucosa are constantly contracting, which pulls on the bottom edge of the attached gingival. However, normally the attached gingival is wide and strong enough to act as a barrier which prevents the gum from being pulled down (receding).

When the height and width of the teeth are already the proper size but there is still excessive gingiva, the lip lowering procedure can align the smile to look more natural. Instead of having orthonastic surgery (re-aligning the jaw bone), a simple surgery to lower the lip and restrict its motion will create a more proportional smile.