The centre of rotation is the point around which an object rotates during tooth movement. Its position varies depending on the type of tooth movement. There are four main types of tooth movement: uncontrolled tipping, controlled tipping, translation, and root movement - each with a different location of the centre of rotation, either near the centre of resistance, apex of the root, at infinity, or incisal edge respectively.
2. CENTRE OF ROTATION
• It is the point around which rotation actually occurs when an object is
being moved.
• The centre of rotation is a variable point and changes according to the
type of tooth movement.
• It can be at any position on or off the tooth.
3. TYPES OF TOOTH MOVEMENT AND
POSITION OF CENTRE OF ROTATION
UNCONTROLLED TIPPING:
In this situation, when force is
applied
the crown moves in one direction and
root moves in the opposite direction.
Here the centre of rotation lies near
to centre of resistance (away from
the
root apex).
4. TYPES OF TOOTH MOVEMENT AND
POSITION OF CENTRE OF ROTATION
CONTROLLED TIPPING:
In this situation, crown moves in the
direction of force but the root
position
remains the same or get minimally
displaced. Here the centre of rotation
lies at the apex of root.
5. TYPES OF TOOTH MOVEMENT AND
POSITION OF CENTRE OF ROTATION
TRANSLATION:
In this tooth moves bodily e.g. both
crown and root portion of tooth
moves
bodily in the direction of force. Here
centre of rotation lies at infinity.
6. TYPES OF TOOTH MOVEMENT AND
POSITION OF CENTRE OF ROTATION
ROOT MOVEMENT:
In this root moves in the direction of
force but the crown position remains
the same or get minimally displaced.
Here centre of rotation lies at incisal
edge of the crown.
7. REFERENCES:
Contemporary Orthodontics 5th Edition William R. Proffit
Orthodontics The Art And Science 7th Edition S.I Balajhi
Swain, B.F , and Ackeman, J.L : An evaluation of the Begg
technique, AM. J. ORTHOD. 55:668-687
