Description
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.
LEARNING OBJECTIVES:
- 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.
Contributors
-
Dr. Hugo De Clerck
Dr. Hugo De Clerck is a graduate of the Rijksuniversiteit Gent’s orthodontic program. He received his PhD in 1986 and maintains a private practice in Brussels. He served as Professor and Chair of the Department of Orthodontics at the Université Catholique de Louvain from 1989 to 2006. Currently he is an Adjunct Professor at the University of North Carolina at Chapel Hill. Dr. De Clerk is a former President of the Belgian Orthodontic Society and Fellow of the Royal College of Surgeons of England.