Empm Jcmmal of Ortlndcmtta 17 (1995) 403-410
O 1993 European Orthodontic Society
Relationship between cranial base and maxillofacial
morphology
Kazutaka Kasai,Takashi Moro, Eisaku Kanazawa,* and Tadamasa Iwasawa
Departments of Orthodontics and "Anatomy, Nihon University School of Dentistry at Matsudo,
Japan
The aims of this study were to investigate the relationships between the cranial
base and maxillofacial morphology in Japanese crania, and to examine the differences
between Class I and Class II samples. Data were obtained from 46 male Japanese crania
from the collection of the Jikei University School of Medicine (Tokyo). The sample represents
populations which would have lived during the last 100 years.
A principal component analysis of linear and angular measurements showed that the
anterior and posterior cranial base, and the cranial base angle were associated in different
ways with different aspects of maxillofacial morphology. Variation in the anterior cranial
base was associated with differences in facial height, lower facial height, bicondylar breadth,
ramal height, and ramal width, while posterior cranial base length was correlated with
bizygomatic breadth. The cranial base angle was negatively correlated with SNA (r= —0.46)
and SNB (r= —0.59), and positively correlated with the palatal and occlusal plane angles.
There were significant differences between Class I and Class II specimens in palatal width,
SNA, ANB, and the palatal plane angle, but no significant difference in cranial base length
or angle.
The evidence suggested that cranial base shape and size was related to facial length,
inclination of the maxilla, and both maxillary and mandibular prognathism.
SUMMARY
ship between the length of the base and the
cranial base angle.
When considering the relationships between
maxillofacial morphology and the cranial base,
it is important to recognize that maxillary and
mandibular growth might be influenced in
different ways by the anterior and posterior
cranial bases, with the maxilla being more
closely related to the anterior cranial base and
the mandible being associated more with the
middle and posterior regions of the cranial base.
There is also evidence that the components
of the cranial base differ between populations.
Yamaki (1987) has shown that the anterior
cranial base in Japanese was shorter than that
in an American samples, while the posterior
cranial base in Japanese was larger than that
in Americans. Cranial base length is larger in
Australian Aboriginals than in Japanese (Kasai
et al., 1993).
The aims of this study were to investigate
the relationship between the cranial base and
maxillo-facial morphology in Japanese crania
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Introduction
It is generally accepted that cranial base growth
influences maxillofacial growth. Furthermore,
the possibility that cranial base growth is a
factor in the development of sagittal malpositions of the jaws cannot be ruled out. However,
few studies have considered cranial base flexure
in relation to occlusion in the sagittal plane and
no definite conclusions have been drawn regarding the influence of the cranial base on malocclusion. Hopkin et al. (1968) observed that cranial
base length and angle increased from Angle
Class III to Class I to Class II division 1
malocclusions. Similarly, Jarvinen (1984) reported a larger ArSN angle in Class II than in
Class III cases in a population of untreated
orthodontic patients. Hildwein et al. (1986),
however, found no significant difference in the
cranial base angle (BaSN) between Class II and
Class I individuals. Similarly, Anderson and
Popovich (1983), comparing children with large
and small cranial base angles, found no relation-
404
K. KASAI ET AL.
and to describe the differences between Class I
and Class II samples.
Table 1 Age distribution of cranial samples.
Age
Number of samples
16-30
31—45
46-60
Mean age
SD
28
13
5
28.8
10
Figure 1 Definitions of radiographic variables <J?>1. Anterior cranial base length, nasion-sella length
<A>. 2. Posterior cranial base length, sella-basion length
3. Cranial base length, nasion-basion length
>- 21. Cranial base angle, nasion-«ella-baiion angle <A>.
22. Gonial angle, the angle between ramus line (the line
through artkulart, tangent to the mandibular posterior
border at the angle region) and mandibular line (the line
through menton, tangent to the mandibular border at the
angle region) <.R>. 23. Symphysii angle, the angle between
chin line (infradentale-pogonion) and mandibular line <./?>•
24. SNA, sella-nasion-pomt A angle <.R>. 25. SNB, seJlanasion-point B angle <iJ>. 26. ANB, point A-nasion-point
B angle <£>• 27. SN-palatal, sella-nasion/anterior nasal
spine-posterior nasal spine angle <J?>. 28. SN-occlusal,
sella-nasion/midpoint of upper and lower incisors-midpoint
of upper and lower first molar angle </{>. 29. SN-mandibular, sella-nasion/mandibular line angle
Results
Tables 2 and"3 show means and standard
deviations for the linear variables, and for the
angular measurements of maxillofacial morphology. The results of the principal component
analysis of linear measurement parameters are
shown in Table 4. This analysis is one of the
multivariate statistical techniques commonly
used by biologists to summarize the information
from large numbers of correlated variables in a
smaller number of components describing
common sources of variation. As is commonly
the case, the first component represented overall
size. The second factor showed large positive
loadings on the thickness of the mandibular
body and the size of ramus, and negative loadings OB faeifll heights (facial height, upper facial
height, and symphysis height). This factor was
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Materials and methods
Data for this study were obtained from 46 male
dentate Japanese crania from the collection of
the Jikei University School of Medicine
(Tokyo). The samples represent recent populations which would have lived during the last
100 years. In these samples, the age and sex
were known from burial records (Table 1).
The maxillofacial morphology of subjects was
assessed by measurements recorded directly
from skulls and indirectly from standardized
radiographs. The radiographic reference points
and methods followed closely those defined by
Bj6rk (1960), Brown (1973), and Richards
(1985). The reference points and variables are
defined in Figures 1-6.
Radiographs were traced on acetate drafting
film, and selected angles and distances were
automatically obtained, and appropriate compensations for radiographic enlargements were
made (Richards, 1983). The reproducibility of
these methods has been described previously
(Richards, 1985). The sample was divided on
the basis of their ANB angle into the two
skeletal classifications: Class I (ANB <5
degrees) and Class II (ANB >5 degrees).
To assess the possible influence of differences
in the age distributions of the groups on the
observed differences in cranial and facial morphology, correlations between age and each of
the variables were calculated. The coefficients
were all small (r<0.32). The small number of
significant coefficients did not appear to reflect
any important biological relationships between
age and the variables considered. .
All statistical analyses in the study were
performed using appropriate SPSS 4.0 for
Macintosh routines.
405
CRANIAL BASE AND MAXILLOFACIAL MORPHOLOGY
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Figure 2 Definitions
of
craniometric
variables:
4. Mandibular length, menton-condylion length.
5. Mandibular body length, menton-gonion length. 6. Facial
length, basion-gnathion length. 7. Lower facial height,
gnathion-anterior nasal spine length. 9. Facial height,
nasion-gnathion length. 10. Upper facial height, nasionanterior nasal spine length. IS. Ramal height, the distance
between condylion and mandibular plane. 19. Coronoid
height, the Hi?tann» between coronion and mandibular
plane. 20. Minimum width of ramus, the least distance
between the anterior and posterior borders of the ramus.
Figure 4 Definitions of craniometric variables. 11. Palatal
length, the distance between prosthion and posterior nasal
spine. 12. Palatal breadth, the distance between bilateral
points endomolare.
14
Figures Definitions
of
craniometric
variables.
13. Bicondylar breadth, the distance between the lateral
surface of the mandibular condyks. 14. Bigonial breadth,
the distance between bilateral points gonion.
FlgoreS Definitions
of
craniometric
variables.
8. Bizygomatic breadth, the distance between bilateral
points zygion.
interpreted as reflecting the negative relationship between mandibular size and facial height.
For the third factor, facial breadths (bizygomatic and bigonial breadth) and palatal length
had positive loadings, while anterior cranial
base and ramal height showed negative loadings. This factor described the negative relationship between breadth of the mandible and the
height of the ramus. The factor loadings for the
fourth component demonstrated the independence of the observed variation in the anterior
and posterior cranial base lengths with a positive loading for posterior cranial base length
(0.62) and a negative loading for the anterior
base length (-0.34). The fifth factor, contribut-
406
K. KASAI ET AL.
Table 3 Mean and standard deviation of angular
measurements of craniofacial morphology.
Angular variables (degrees)
Mean
SD
Cranial base angle
Gonial angle
Symphysis angle
133.96
124.91
75.35
83.75
77.99
5.76
7.14
16.03
38.69
5.29
8.60
6.85
4.57
3.85
2.96
3.57
4.90
7.20
SNA
SNB
ANB
SN-palatal
SN-occlusal
SN-mandibular
Figure 6 Definition! of craniometric variables. 16. Symphysis height, the height from the lowest median point
on the mandible to the point infradentale. 17. Symphysis
thickness, the thickness of the median point on the mandible. 18. Corpus thickness, the thickness of the mandibular
body measured at the level of the second molar parallel to
the vertical axis of the body of mandible.
Table 2 Mean and standard deviation of linear
measurements of craniofacial morphology.
Mean
SD
Anterior cranial base length
Posterior cranial base length
Cranial base length
Mandibular length
Mandibular body length
Facial length
Lower facial height
Bizygomatic breadth
Facial height
Upper facial height
Palatal length
Palatal breadth
Btcondylar breadth
Bigonial breadth
Ramal height
Symphysis height
Symphysis thickness
Corpus thickness
Coronoid height
Minimum width of ramus
62.52
43.37
101.65
108.26
66.39
99.26
105.28
133.49
119.97
71.12
49.67
40.06
119.41
97.34
51.74
35.68
14.14
16.68
62.10
34.04
3.70
3.33
5.53
6.06
4.38
6.06
6.77
6.49
7.57
4.42
4.21
3.47
6.48
8.83
8.23
3.11
1.50
1.70
6.14
3.04
ing only 6.0 per cent to the total observed
variation, described the palatal breadth.
Table 5 shows the result of the principal component analysis of the angular measurement
parameters. The first component was concerned
with horizontal growth of face and anteroposterior positioning of the jaws, with positive
factor loadings for cranial base angle and the
palatal, occlusal, and mandibular plane angles,
and negative loadings for the measures of maxillary and mandibular prognathism (SNA and
SNB). The second factor described the differ-
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T .inftfir dimensions (mm)
ences in the horizontal position of upper and
lower jaws, while the third factor described the
relationship between the mandibular symphysis
angle and the gonial angle. In summary, these
results indicated that the cranial base angle was
associated with the antero-posterior position of
the upper and lower jaws, and with the inclination of the horizontal facial planes.
Correlation coefficients describing the relationships between the linear and angular measurement are shown in Tables 6 and 7. Significant
relationships were noted between cranial base
length and the parameters describing the maxilla. Anterior and posterior cranial base lengths
were correlated differently with some parameters. Both anterior and posterior cranial base
lengths showed significant positive correlations
with mandibular length, mandibular body
length, facial height, upper facial height, and
symphysis height. Only the anterior cranial base
length was correlated with facial length, lower
facial height, palatal breadth, ramal height, and
ramal width, while only posterior cranial base
length showed a significant relationship with
bizygomatic breadth.
The cranial base angle was negatively correlated with both mandibular (r=—0.59) and
maxillary prognathism (r=—0.46), and positively correlated with the palatal and occlusal
plane angles. These results confirmed the conclusions derived from the principal component
analysis.
The means and standard deviations for
Class I and Class II samples are shown in
Table 8. There were significant differences
between the groups in palatal width, SNA, ANB
and palatal plane angle. However, there were
no significant difference in cranial base leagth
and angle between the groups.
407
CRANIAL BASE AND MAXILLOFACIAL MORPHOLOGY
Table 4 Principal component analysis of linear measurement
Anterior cranial base length
Posterior cranial base length
Cranial base length
Mandibular length
Mandibular body length
Facial length
Lower facial height
Bizygomatk breadth
Facial height
Upper facial height
Palatal length
Palatal breadth
Bicondylar breadth
Bigonial breadth
Ramal height
Symphysi* height
SymphysiB thickness
Corpus thickness
Coronoid height
Minimum width of ramus
Z2
Z3
Z4
Z5
0.68
0.52
0.75
0.89
0.78
0.73
0.81
0.70
0.71
0.68
0.40
0.35
0.64
0.46
0.46
0.61
0.33
0.29
0.55
0.49
-0.13
-0.34
-0.27
-0.17
0.03
-0.06
0.07
0.35
-0.56
-0.51
0.15
0.29
0.40
-0.11
0.25
-0.49
0.65
0.53
0.45
0.59
-0.40
0.04
-0.37
0.05
-0.05
-0.17
0.05
0.38
0.11
-0.14
0.56
-0.06
0.29
0.58
-0.61
0.20
0.02
-0.01
-0.04
-0.21
-0.34
0.62
-0.10
-0.03
0.08
-t).32
-0.26
0.21
0.03
0.22
0.06
-0.43
0.01
-0.16
0.26
-0.15
-0.18
-0.13
0.42
0.23
0.15
0.11
0.29
-0.16
-0.01
0.30
-0.10
-0.13
-0.16
-0.05
0.18
-0.67
-0.23
0.20
-0.21
-0.03
0.15
0.48
-0.11
0.15
7.58
37.9
37.9
2.78
13.9
51.8
1.70
1.37
1.19
8.5
6.9
6.0
60.3
67.2
73.1
Table 5 Principal component analysis of angular
measurement
Zl
Cranial base angle
Gonial angle
Symphysis angle
SNA
SNB
ANB
SN-palatal
SN-occhisal
SN-mandibular
Eigen values
Contribution
Cumulative proportion
Z2
Z3
0.67
0.53
-0.39
-0.70
-0.91
0.10
0.63
0.79
0.81
-0.08
0.43
0.30
0.67
0.07
0.94
0.06
0.10
0.31
0.35
-0.65
0.68
-0.03
-0.21
0.22
0.42
-0.38
3.88
43.1
43.1
1.72
19.1
62.2
1.48
16.4
78.6
074
Discussion
Ford (1958) has suggested that, considered as
a whole, the cranial base grows in a fashion
intermediate between the growth of the cranium, which is dependent on the neural pattern
of early and rapid growth, and growth of the
face, which conforms to a general skeletal pattern of growth characterized by fairly even
growth from birth until the pubertal spurt. He
emphasized, however, that individual parts of
the cranial base manifest either a neural or
general skeletal rate, but not an intermediate
rate of growth. The sella to foramen caecum
region shows a neural pattern of growth compared with the foramen caecum to nasion and
basion to sella-skeletal regions which show a
skeletal pattern. Growth after birth occurs at
the spheno-occipital synchondrosis and the
spheno-ethmoidal and fronto-ethmoidal sutures. Neural-type growth changes in the cranial
base have been shown to be complete by about
7-8 years (de Coster, 1953; Stamrud, 1959). In
comparison, growth at the sutures is complete
by the end of the first decade, whereas growth
at the synchondroses continues until 12-16
years (Scott, 1967).
The normal variation in the cranial base angle
may fluctuate within a very wide range. The
cranial base angle shows great variability, with
a standard deviation of approximately five
degrees or more (BjOrk, 1955; Ricketts, 1961;
Solow, 1966; Bacon et al., 1983,1992; Anderson
and Popovitch, 1983; Jfirvinen, 1984; Cooke
and Wei, 1988; Kerr and Adams, 1986; Schmuth
et al., 1988). This relatively large variability
explains why significant differences in this
angle are rarely described in group comparisons
(Bacon et al, 1992).
Saito (1989) reported that the spheno-
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Eigen values
Contribution
Cumulative proportion
Zl
408
TaMe 6
K. KASAI ET AL.
Correlation coefficients between cranial base and craniofacial measurements.
Anterior cranial base length
Mandibular length
Mandibular body length
Facial length
Lower facial height
Bizygomatic breadth
Facial height
Upper facial height
Palatal length
Palatal breadth
Bicondylar breadth
Bigonial breadth
Ramal height
Symphysis height
Symphysis thickness
Corpus thickness
Coronoid height
Minimum width of ramus
>
•i <0.05;
Posterior cranial base length
0.48**
0.52* *
0.22
0.20
0.34*
0.49**
0.58"
0.19
-0.16
0.22
0.20
0.23
0.42**
-0.10
0.01
0.57**
0.54**
0.65**
0.54**
0.24
0.43"
0.50**
0.14
0.29*
0.22
0.22
0.34*
0.36*
0.13
0.15
0.22
0.33*
0.28
0.15
Cranial base length
0.64**
0.63"
0.70**
0.54**
0.29*
0.56**
0.60**
0.12
0.10
0.22
0.25
0.35*
0.43**
0.06
0.16
0.18
0.34*
**P<0.0l.
cranial
Cranial base angle
Gonial angle
Symphysis angle
SNA
SNB
ANB
SN-palatal
SN-occlusal
SN-mandibular
0.20
-0.08
-0.46"
-0.59**
0.06
0.44"
0.53"
0.29
occipital complex has a close relationship to the
skeletal facial pattern and contributes to the
pattern of facial growth. Under normal conditions cranial base angle correlates with facial
form: a more obtuse cranial base angle being
associated with a more divergent facial type
(Solow and Tallgren, 1976; Smahel and
Skvarilova, 1988; Bacon et al., 1989, 1992). In
this study variation in the cranial base angle
was associated with the antero-posterior position of the jaws, and the inclination of maxilla
as reflected by the palatal and occlusal plane
angles. This is consistent with the close relationship between cranial base angle and facial pattern described in previous studies.
Cranial base differences between Class I and
Class II malocclusion samples have been
described by a number of previous workers.
Kerr and Adams (1986) reported that the
cranial base angles in Class II cases were larger
than Class I cases. In a longitudinal study, Kerr
and Hirst (1987) observed a larger cranial base
angles in Class II than Class I subjects, but
whether or not the observed differences were
statistically significant is not known.
In this study, there were no significant differences in cranial base length and angle between
the Class I and Class II samples. However,
cranial base angle was correlated strongly with
mandibular prognathism (r= — 0.59). Kerr and
Adams (1988) have shown that the relationship
between cranial base angle and SNB was very
strong (r= —0.70). They concluded that cranial
base size and shape influenced mandibular prognathism by determining the relative anteroposterior position of the condyle. In the
Japanese sample this relationship was not as
strong as that described in Caucasians. This is
consistent with previously described differences in cranial base morphology between
populations.
There were a number of significant relationships between cranial base form and maxillofacial morphology in the Japanese sample
described in this study. Cranial base length was
related to mandibular length and facial height.
In particular, the anterior cranial base length
was correlated with facial length and lower
facial height, whereas the posterior cranial base
length was associated with bizygomatic breadth.
Th» cosult of principal component analysis
provided good evidence that the anterior and
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Table 7 Correlation coefficients between
base angle and angular measurements.
409
CRANIAL BASE AND MAXILLOFACIAL MORPHOLOGY
Table 8 Mean and standard deviation of Class I and Class II groups.
Class I (n = 17)
Class II (n =29)
t-te-et
Mean
Anterior cranial base length
Posterior cranial base length
Cranial base length
Mandibular length
Mandibular body length
Facial length
Lower facial height
Bizygomatk breadth
Facial height
Upper facial height
Palatal length
Palatal breadth
Bicondylar breadth
Bigonial breadth
Ramal height
Symphysis height
Symphysis thickness
CoTDUS thirVnwK
Cranial base angle
Oonial angle
Symphysis angle
SNA
SNB
ANB
SN-palatal
SN-ocdusal
SN-mandibular
Mean
SD
63.03
43.10
101.75
108.64
67.51
97.81
105.66
134.21
118.37
69.72
49.54
41.63
120.82
99.12
52.08
35.28
14.61
16.60
62.64
34.50
2.53
3.44
4.40
5.10
4.37
4.93
6.34
6.94
6.44
2.72
4.54
3.06
7.39
8.42
8.59
3.21
1.72
1.85
6.56
3.56
62^2
43.54
101.59
108.04
65.74
100.11
105.06
133.07
120.90
71.93
49.73
39.14
118.58
96.30
51.54
35.92
13.87
16.72
61.79
33.77
4.26
3.32
6.18
6.64
4.33
6.57
7.11
6.31
8.11
5.04
4.11
3.40
5.86
9.03
8.16
3.09
1.31
1.65
5.98
2.72
133.53
123.94
73.90
81.29
78.65
2.64
5.66
14.30
37.19
5.56
10.26
7.65
2.93
3.06
1.22
3.68
5.54
7.55
134.21
125.47
76.19
85.19
77.60
7.59
8.00
17.04
39.56
5.22
7.61
6.32
4.78
4.25
1.97
3.27
4.27
6.96
••
**
#*
**
•*P<0.01.
posterior cranial base were associated in different ways with different aspects of facial morphology. The analysis suggested that a component
of the observed variation in posterior cranial
base length was independent of overall cranial
base length and anterior cranial base length.
This might be explained by the different growth
patterns and anatomical relationships between
the structures, since the maxilla is associated
with the anterior cranial base, while the mandible is related to the posterior cranial base.
In orthodontic treatment careful attention
should be paid to a patient's maxillofadal
growth. The result of this study provided the
possibility of prediction of directional growth
of the skeletal points, although it is difficult to
quantify the growth of both maxilla and mandible. The relationship between cranial base and
maxillofadal morphology shown in this study
might help in prediction of the growth of a
Class LI patient's mandible which is an important factor in orthodontic treatment planning.
In summary, the results of this study provide
further evidence of the way in which the components of the cranial base vary independently
and, in turn, are associated in different ways
with the observed variation in maxillofadal
morphology. Furthermore, significant assodations between cranial base angle and inclination of the maxilla, and both maxillary and
mandibular prognathism supported the view
that the pattern of cranial base growth is related
to variation in maxillofadal form. Despite the
significance of the cranial base in aspects of
fadal growth, Class I and II samples did not
show significant differences in cranial base form,
reflecting the complexity of the factors involved
in the development of malocclusion.
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Coronoid height
Minimum width of ramus
SD
410
Address for correspondence
Dr Kazutaka Kasai
Department of Orthodontics
Nihon University School of Dentistry at
Matsudo
2-870-1 Sakaecho-nishi
Matsudo, Chiba 271
Japan
Acknowledgements
We are indebted to Professor H. Yamashita,
Assistant Professor S. Kato and Dr S. Takeuchi,
Department of Anatomy, Jikei University
School of Medicine (Tokyo) for making the
collections available.
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