1. Prediction of growth type and rotations of facial skeleton
1. Cross-sectional studies / growth templates
Several cross-sectional studies collating cephalometric data from groups of patients. All have
limitations, such as small samples, not adequately matched for age, sex, racial group. Give
information only on mean changes and do not take account of individual variation.
Examples - Bolton Brush (Broadbent 1975), Michican (Riolo 1974), Burlington (Popovic &
Thompson 1977). Templates derived from growth studies data (Ricketts 1972, Johnson 1975)
can be used to indicate average anticipated changes, but do not produce a prediction on an
individual basis.
2. Longitudinal method.
Bjork 1969 Serial cephalometric films could be superimposed on stable structures (Bjork
1951) to establish pattern of growth (eg direction of growth rotation) and this would indicate
future growth direction. However, Bjork & Palling 1985 found relationship between past and
future growth low - not of predictive value.
3. Mixed studies
4. Metric method
Bjork 1969 suggested that measurements from a single headfilm could indicate future growth
pattern. However, no such predictive measurement found.
5. Structural method
Bjork 1969 proposes another method which predicts the direction of mand growth according
to these features:
1. Inclination of the condylar head;
2. Curvature of the mandibular canal;
3. Shape of the lower border of the mandible;
4. Inclination of the mandibular symphysis;
5. Interincisal angle;
6. Interpremolar and intermolar angles;
7. Anterior lower face height.

2. Mandibular growth rotations are a reflection of differential growth in anterior and posterior
face height (Houston 1988). The anterior face height is affected by eruption of teeth and
vertical growth of the soft tissues including suprahyoid musculature and fasciae, which are in
turn influenced by growth of the spinal column. The posterior face height is determined by
condyles’ growth direction, vertical growth at spheno-occipital synchondrosis and the
influence of mastication muscles on the ramus. The overall direction of growth is thus the
result of the growth of many structures (Mitchell 2007).
Three different types of mandibular growth rotation were originally described by Björk and
Skieller, with the terminology associated with these different rotations being later simplified
by Solow and Houston (Björk and Skieller, 1983; Solow and Houston, 1988):
a) Total rotation(Bjork and Skieller 1983) or true rotation (Solow and Houston 1988) referring
to the rotation of mandibular body and is measured by change in inclination of implant line
or stable trabecular reference line in mandibular corpus, relative to anterior cranial base.
When the implant line or reference line rotates forward relative to nasion-sella line during
growth, the total rotation is designated as negative and vice versa.
b) Matrix rotation (Bjork and Skieller 1983) or apparent rotation(Solow and Houston 1988)
referring to the rotation of soft tissue matrix (or tangential line of lower mandibular border)
relative to anterior cranial base. It is recorded as negative when the tangenial line rotates
forward relative to nasion-sella line and positive when the line rotates backward relative to
nasion-sella line. The matrix sometimes rotates forwards and sometimes backwards in the
same subjects during the growth period with the condyles as the centre of rotation and this is
called pendulum movement.
c) Intramatrix rotation (Bjork and Skieller 1983) or angular remodelling of mandibular border
(Solow and Houston 1988) referring to the difference between total rotation and matrix
rotation. It is the expression of the remodelling of the lower border of the mandible and is
defined by the change in the inclination of an implant or reference line in mandibular corpus
relative to tangential mandibular line. The centre of intramatrix rotation is in mandibular
corpus and not at condyles.
Type of rotation
Bjork and Skieller 1972 reported that there were 80 % of people are “forward” or anterior
rotators and 20% backward or posterior rotators.

3. 1. For those anterior rotators:
 The centre of rotation:
a) Type I: point of rotation about the condyle - resulting in a deep bite and reduced lower face
height.
b) Type II: point of rotation located at the incisor edge of the lower incisors - resulting in
marked development of the posterior face height and normal anterior face height.
c) Type III: Shown in cases with large overjets/ reverse overjets, the point of rotation is at the
level of the premolars - the anterior face height becomes underdeveloped and the posterior
face height increases with a basal deepbite.
 It increase in overbite which is difficult to reduce and associated with slower space closure.
 Possibly with low FMPA.
 They will become more progeny rotation of “B” point forward.
 It may also develop increasing lower incisor crowding due to LLS trapping behind ULS.
 Correction of class II malocclusion will be helped by forward growth rotation
 Structural feature:
(1) The condyle is inclined forward;
(2) The mandibular canal has a curvature greater than the mandibular contour;
(3) The lower border of the mandible is rounded anteriorly and concave at the angle, due to
bony deposition along the anterior region and symphysis, and resorption below the angle;
(4) The symphysis is inclined forward within the face and the chin is prominent;
(5) The interincisor angle increased
(6) Interpremolar and intermolar angles are all increased;
(7) The anterior lower face height is reduced with a tendency towards an increased overbite.
2. Subjects with posterior rotation of mandible
 The centre of rotation:
a) Type I: point of rotation about the condyle - resulting in an increased anterior face height.

4. b) Type II: point of rotation around the most distal occluding molar.
 Develop increase anterior vertical face height and “long face appearance”, and AOB with
space easily to close
 Possibly with high FMPA.
 They will become more class II with the rotation as “B” point moves backwards.
 It may also develop increasing lower incisor crowding due to retoclination of LLS as a
normal compensatory movement.
 Correction of class II malocclusion more difficult by backward rotation
 Structural feature:
(1) A backward inclination of the condyles;
(2) A flat mandibular canal;
(3) A lower border that is thinner anteriorly and convex, due to minimal remodelling along
the lower border of the mandible and bony deposition at the posterior border of the ramus;
(4) The symphysis is inclined backward within the face and the chin is receding; (5) the
interincisor angle decreased
(6) Interpremolar and intermolar angles are all decreased;
(7) the lower anterior face height is increased and there is an anterior open bite.