Types Of Tooth Movements

Types Of Tooth Movements

What are the types of orthodontic tooth movements? Discuss the various theories related to tissue changes incident to orthodontic tooth movement.
Answer.

Orthodontic Tooth Movements:

• Tipping: It is a simple type of tooth movement where a single force is applied to the crown which results in the movement of the crown in the direction of the force and the root in the opposite direction. It is the simplest among the tooth movements. It is of two types
  • Controlled tipping: Controlled tipping of the tooth occurs when a tooth tips about a center of rotation at its apex. Here there is a lingual movement of the crown with minimal involvement of the root in the labial direction.
  • Uncontrolled tipping: Uncontrolled tipping of the tooth describes the movement of a tooth that occurs about the center of rotation apical to and very close to the center of resistance. It is characterized by the crown moving in one direction while the root moves in opposite direction.
• Bodily movement: If the line of action of an applied force passes through the center of resistance of a tooth, all the points on the tooth will move an equal distance in the same direction signifying a bodily displacement. This is called translation.
• Intrusion: It is a bodily displacement of a tooth along its long axis in an apical direction.
• Extrusion: It is a bodily displacement of a tooth along its long axis in an occlusal direction.
• Rotation: Rotations are labial or lingual movements of a tooth around its long axis.
• Torquing: It can be considered as a reverse tipping characterized by the lingual movement of the root.
• Uprighting: During orthodontic treatment crowns of the certain teeth will be tipped in a mesiodistal direction with the roots tipped in opposite way. Tipping these roots back to get a parallel orientation is termed uprighting.

Theories Related to Tissue Changes Incident to Orthodontic Tooth Movement

Theories are:

• Pressure tension theory: Refer to Ans 9 of same chapter.
• Piezoelectricity: Refer to Ans 5 of same chapter.

Fluid Dynamic Theory

• It is also known as blood flow theory and is proposed by Bein.
• As per this theory, tooth movement occurs due to alteration in fluid dynamics inside the periodontal ligament.
• Periodontal ligament occupies the periodontal space between the tooth and the alveolar socket.
• Periodontal space has a fluid system which is made of interstitial fluid, cellular elements, blood vessels and the ground substance. In addition to the periodontal fibers.
• When force of the greater magnitude and direction is applied during orthodontic tooth movement, interstitial fluid inside the periodontal ligament squeezes out and move to the apex as well as cervical margins and leads to decrease in tooth movement which is known as squeeze film effect by Bien.
• As orthodontic force is applied it leads to compression of periodontal ligament.
• Blood vessels of the periodontal ligament get trapped between the principal fiers which lead to stenosis. Vessel above the stenosis, then balloons which leads to the formation of aneurysm.
• Bien had suggested that there is alteration in the chemical environment at the site of vascular stenosis because of decrease in oxygen level in compressed area as compared to the tension side.
• Formation of such aneurysms and vascular stenosis causes blood gases to escape in the interstitial fluid which create a favorable local environment for the resorption.