Biomechanics of Intrusion

Intrusion is a common orthodontic tooth movement which is employed in the cases of deep bite where anteriors are intruded for correction or in anterior open bite where posteriors are intruded to close the bite for correction.intrusion is tooth movement that occurs in an axial (apical) direction and whose center of rotation lies at infinity. Intrusion is considered to be a procedure safe from root resorption provided that the magnitude and direction of forces are carefully monitored. intrusion can be of three types namely true intrusion relative intrusion and pseudointrusion. True intrusion is achieved by moving the root apices of the anteriors closer to the bony base. Relative intrusion is achieved by keeping them where they are while the mandible grows and the posterior teeth erupt. Apparent intrusion is achieved by extrusion of the posterior teeth.