Intrusion Mechanics

Jackson’s Triad consists of structural integrity, functional stability, and esthetic harmony. An ideal position of the incisors on its apical base in all three planes of space plays a vital role in achieving this balance. Deep bite (or excessive vertical overlap) is a common symptom associated with Class II malocclusions and can be corrected with various modalities including intrusion of upper and/or lower incisors, extrusion of posterior teeth, and flaring of anterior teeth. The intrusion of the upper and lower incisors is the most effective way of correcting the deep bite, as it moves their root apices closer to the nose and lower border of the mandible, respectively. Intrusion is defined as the ＂tooth movement that occurs in an axial (apical) direction and whose center of rotation lies at infinity. It is an axial type of translation＂. It is often associated with an increase in the vertical dimension of the face, as well as an improvement in the aesthetic appearance. Relative intrusion/ pseudo-intrusion of the incisors can also be used, keeping them where they are while the mandible grows and the posterior teeth erupt. This method is used to maintain the mandibular plane angle.