Types of Intrusion
- True Intrusion: Incisors move towards the bone without movement of posterior teeth
- Relative Intrusion: Extrusion of posterior teeth to correct deep bite
- Can be performed in adolescents with deep bite tendency
Methods of Intrusion
- Burstone's Intrusion Arch: Segmental arch method with low magnitude forces
- Ricketts Utility intrusion arch: Continuous wire with statistically indeterminate system
- Three-Piece intrusion arch: Developed for retraction and intrusion simultaneously
Types of Cases for Intrusion
- Deep bite with vertical facial growth pattern: Manage vertical growth and prevent eruption of posterior molars
- Deep bite with horizontal facial growth pattern: Increase vertical height through relative intrusion
Major Principles of Intrusion
- Controlling force magnitude and consistency
- Single point contacts on anterior teeth
- Point of force application and center of resistance
- Selective intrusion based on anterior tooth geometry
- Control over reactive units and avoidance of extrusive mechanics
Force Magnitude in Intrusion
- Force magnitude must be constant throughout application
- Higher force can lead to side effects such as root resorption and extrusion of posterior teeth
- Equal and opposite forces are produced at incisors and molars
- Use wire with low load-deflection rate for constant force of intrusion
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".
