What is the minimum amount of mandibular depression needed for effective mastication?

The minimum amount of mandibular depression required for effective mastication is generally recognized as 18 mm. This range allows for adequate opening of the mouth to facilitate the mechanical processes of chewing. During mastication, the mandible must depress sufficiently to permit the effective manipulation of food between the upper and lower teeth. At least 18 mm of depression ensures that the molars can come into contact with the food to grind it effectively. While lower amounts of depression may permit some limited biting or initial contact, they are insufficient for the full range of movements necessary for efficient chewing and processing of food. Therefore, the choice of 18 mm reflects the biomechanical needs associated with mastication.