Intrusion (orthodontics)

Intrusion is a movement in the field of orthodontics where a tooth is moved partially into the bone. Intrusion is done in orthodontics to correct an anterior deep bite or in some cases intrusion of the over-erupted posterior teeth with no opposing tooth. Intrusion can be done in many ways and consists of many different types. Intrusion, in orthodontic history, was initially defined as problematic in early 1900s and was known to cause periodontal effects such as root resorption and recession. However, in mid 1950s successful intrusion with light continuous forces was demonstrated. Charles J. Burstone defined intrusion to be "the apical movement of the geometric center of the root (centroid) in respect to the occlusal plane or plane based on the long axis of tooth".

This type of intrusion consists of true intrusion of incisors without any extrusion of the posterior teeth. The incisors in the anterior teeth (depending on the arch) move towards the bone and no movement of posterior teeth is seen in comparison with relative intrusion where posterior teeth erupt out of the bone. A light continuous force is known to achieve true intrusion. True intrusion can be done with methods such as Burstonian segmental arch mechanics or the use of TADs anteriorly.

This type of intrusion consists of extrusion of posterior teeth to correct the deep bite. The anterior incisors do not move up or down in this type of intrusion. Relative intrusion can be done with various methods such as using a reverse curve of spee wires, anterior bite blocks, differential molar eruption with functional appliances such as Twin Block Appliance. This type of movement can be performed in patients who are adolescents and have deep bite tendency.

Two orthodontic techniques have been developed for the purpose of intrusion of anterior teeth. They are intruding the teeth segmentally, as proposed by Dr. Charles J. Burstone or intruding the teeth through the bioprogressive techniques.

This method was proposed by Dr. Burstone in 1950s. This segmental arch method used two posterior segments and one anterior segment. A separate continouous intrusion arch is used which was inserted in the auxiliary tube of molars on one end and tied to the anterior segment on the other end. The molars served as an anchorage for the intrusion arch while the pure intrusion was achieved via downward force on the anterior segment where the intrusion arch was engaged. Dr. Burstone also believed in using low magnitude forces to achieve the desired intrusion.

...
Wikipedia