The main objective of dentofacial orthopedics is an
improvement of the anteroposterior relation between upper
and lower jaw. However, in tooth born class III orthopedics
a canting of the occlusal plane due to upper molar extrusion
often results in a posterior and downward rotation of the
mandible and an increase of the vertical dimension of the
face. This reduces the prominence of the chin and may be
wrongly interpreted as a growth restriction of the mandible.
A canting of the occlusal plane may also be the result of a rotation of the maxilla and the palatal plane. Since the line of force of conventional class III orthopedics passes below the hypothetical center of resistance of the zygomaticomaxillary complex, the direction of the rotation usually is anterior or counter-clockwise with downward displacement of the molars.
Maxillary rotations can be altered by changing the angulation of the orthopedic force and its perpendicular distance to the center of resistance or by adding an extra moment of force.
The moment-to-force ratio of the resulting orthopedic force system applied to the upper jaw will determine the direction of the maxillary rotation and the subsequent rotations of the occlusal plane and the mandible.
- Rotations of the occlusal plane and palatal plane by different class III orthopedics.
- Biomechanics of maxillary rotations.
- Effect of a canting of the occlusal plane on mandibular rotations.