2. Facial growth in terms of rotations is
important in terms of understanding the
development of craniofacial complex.
The introduction of implant method by
Bjork(1955) made it possible to study the
rotations of maxilla and mandible.
3. Hard palate behind deciduous canines (prior
to eruption of permanent maxillary incisors)
Below the anterior nasal spine(after eruption
of maxillary incisors)
Two implants on either side of zygomatic
process of maxilla
Border between the hard palate and alveolar
process medial to the first molars
4.
5. Anterior aspect of symphysis
Two pins on the right side of mandibular
body, one pin under the first premolar and
second under the second premolar or first
molar
One pin on the external aspect of the right
ramus at the level of occlusal surface of
molars
6.
7. ROTATION
It is the angular movement of one body
relative to another
FORWARD ROTATION
Posterior growth greater than anterior
Counterclockwise rotation
Negative rotation
10. INTERNAL ROTATION
Rotation that occurs in the core of the jaw.
e.g in the mandible core is the bone that
surrounds the inferior alveolar nerve
Bjork and Skieller distinguished two
contributions to internal rotation
a)Matrix rotation
b)Intramatrix rotation
11.
12. MATRIX ROTATION
Rotation around the condyle
INTRAMATRIX ROTATION
Rotation centered within the body of the
mandible
14. EXTERNAL ROTATION
Rotations caused by surface changes and
alterations in the rate of tooth eruption.
Surface and remodelling changes in
functional processes of the mandible
Alveolar process
Muscular process
Condylar process
15.
16. INTERNAL ROTATION
For an average individual with normal vertical
facial proportions, there is about -15 degrees
internal rotation from age 4 to adult life
Matrix Rotation 25%
Intramatrix Rotation 75%
17. EXTERNAL ROTATION
During the time the core of the mandible
rotates forward an average of 15 degrees, the
mandibular plane angle representing the
orientation of the jaw to an outside observer
,decreases only 2-4 degrees on the average
The reason that the internal rotation is not
expressed in jaw orientation,of course, is that
surface changes(external rotation) tend to
compensate
18. This means that the posterior part of the
lower border of mandible must be an area of
resorption, while the anterior aspect of the
lower border is unchanged or undergoes
slight apposition
21. INTERNAL ROTATION
Forward and backward
EXTERNAL ROTATION
Remodelling of palate ,alveolar
process,variations in amount of eruption of
incisors and molars contribute to external
rotation
Opposite in direction and equal in magnitude
to internal rotation
22. So the two rotations cancel and the net
change in jaw orientation(as evaluated by the
palatal plane) is zero.
23.
24. Short face type
Short lower anterior
facial height
Nearly horizontal
palatal plane
Low mandibular plane angle
Deep bite
Crowded incisors
25. Long face type
Excessive lower anterior
facial height
Negative inclination of
palatal plane
Increased mandibular
plane angle
Anterior open bite
26. Forward rotation of maxilla
Proclination of incisors
Backward rotation of maxilla
Upright incisors
Forward rotation of mandible
Upright incisors and crowding
Backward rotation of mandible
Proclination of incisors
