Managing vertical growth requires further prevention or increase of the lower facial height. This involves prevention of any eruption of posterior molars because their eruption would lead to mandible moving downwards and backwards which would cause worsening of a Class II malocclusion and increase in the lower facial height. These type of patients must have intrusion of the incisors to achieve desired correction of anterior deep bite in conjunction with prevention of any eruption of posterior molars which maintains the vertical height of the patient. Deep bite with horizontal facial growth pattern In these types of cases, a patient has reduced anterior lower facial height and they have a skeletal deep bite tendency. It is essential in these type of patients, to increase the vertical height of the face and one of the most common ways this can be performed is through relative intrusion. This movement involves extrusion of the posterior molars and is sometimes combined with intrusion of anterior incisors. It is important to note the difference of ages that play a role in eruption of the posterior molars. An adolescence has an inter-maxillary growth space which allows the posterior molar eruption without any relapse in the later age when relative intrusion is performed in their orthodontic treatment. However, if relative intrusion is performed in adults who have a deep bite tendency with short anterior lower facial height, there is a higher chance of relapse of this movement. This is due to two reasons: Adults do not have intermaxillary growth space that posterior teeth can erupt into and adults tend to have a strong facial jaw musculature which leads to "pound" the molars back into their original position. Therefore, in an orthodontic treatment it is important to diagnose a patient with a type of facial growth that is occurring before taking any treatment steps. Major Principles of Intrusion Dr. Charles Burstone in his 1977 paper discussed about six major principles to follow when working with intrusion mechanics Controlling the force magnitude and consistency Single point contacts on the anterior teeth Point of force application & Center of Resistance Selective Intrusion based on anterior tooth geometry Control over the reactive unites by formation of a posterior anchorage unit Inhibition of eruption of posterior teeth and avoidance of "extrusive" mechanics Force Magnitude It is important to note that force magnitude in pure intrusion of incisors must be constant throughout the application.