Craniofacial height in relation to cross-sectional maxillary and mandibular morphology
Klinge et al. Progress in Orthodontics
Craniofacial height in relation to cross- sectional maxillary and mandibular morphology
Anna Klinge 0 2
Karin Becktor 1
Christina Lindh 0 2
Jonas P Becktor 0 2
0 Department of Oral and Maxillofacial Surgery and Oral Medicine, Faculty of Odontology, Malmö University , SE-205 06 Malmö , Sweden
1 Clinic for Orthodontics and Oral Surgery , Strandvejen 116A, 2900 Hellerup, Copenhagen , Denmark
2 Department of Oral and Maxillofacial Surgery and Oral Medicine, Faculty of Odontology, Malmö University , SE-205 06 Malmö , Sweden
Background: In order to gain a better understanding of how growth of the alveolar bone is linked to the vertical development of the face, the purpose of this study was to investigate if there is an association between the cross-sectional morphology of the maxillary and mandibular bodies with the craniofacial height, using images from cone beam computed tomography (CBCT). Methods: From 450 pre-treatment CBCT scans, 180 were selected to be included in the study. Lateral head images were generated from the CBCT scans and were used to categorise subjects into three groups based on their vertical craniofacial height. Cross-sectional images from CBCT volumes were reformatted of the maxillary and mandibular bodies at five locations in the maxilla and five in the mandible. Each image was measured at one height and two width measurements. Statistical analysis performed was the one-way analysis of variance with a Tukey post hoc test. A significance level of 5% was used in all comparisons. Results: Patients with large vertical craniofacial height had a significantly higher cross-sectional area both in the maxilla and in the mandible. In the same group, the cross-sectional area was significantly thinner in the mandible compared with the other two groups, especially in the anterior region. Conclusions: This study further highlights the close relationship between craniofacial height and alveolar bone dimensions and contributes with important knowledge for planning and follow-up of comprehensive dental- and orthodontic treatments.
Craniofacial development; Treatment planning; Treatment timing; Cephalometrics; Biological basis of orthodontics
Craniofacial growth is a complex process, and
understanding the factors involved is important in connection
with orthodontic treatment of children and adolescents.
The growth of the craniofacial complex can be divided
into four different components: (1) growth of the cranial
base, (2) growth of the maxilla, (3) growth of the
mandible and (4) growth of the dentoalveolar bone [
In the postnatal growth period, growth in the
sphenooccipital synchondrosis cartilage and the cartilage of the
condyle has a large influence on the vertical development
of the face, and adaptive growth of the maxillary sutures
and growth of the dentoalveolar bone will fill out the face
]. The link between the predominately genetically
determined growth of these two cartilages and growth of the
dentoalveolar bone is also known as the dentoalveolar
compensatory mechanism [
]. The factors that are
responsible for this dentoalveolar mechanism are not fully
understood. However, it has been demonstrated that
growth of the dentoalveolar bone is taking place in
connection with tooth eruption and is accordingly dependent
on a normal eruption process .
The vertical development of the face has a significant
impact on the direction and magnitude of tooth eruption
]. There is a noticeable variation in the eruption rate
of the teeth, with a peak in eruption velocity at the time
of the maximum pubertal rate of growth in body height
]. Assuming that continued eruption is a
compensatory mechanism for facial growth, it seems reasonable to
conclude that eruption follows the general pattern of
craniofacial growth [
The growth of the alveolar bone is less genetically
determined compared to the rest of the skeleton and can
be influenced by functional conditions and orthodontic
]. Accordingly, knowledge of the expected
growth pattern of the alveolar bone is important in
relation to orthodontic treatment of growing individuals.
Furthermore, the morphology of the alveolar bone in
three dimensions is important when it comes to the
planning of orthodontic tooth movement as well as in
connection with insertion of skeletal, temporary
anchorage devises (TADs) and dental implants for restorative
There are, however, only limited reports where the
craniofacial morphology has been used as a guideline for
evaluation of height and width of the alveolar bone. A
comprehensive thesis on the various facial anatomical
components and the relationship between them was
presented in 1966 by Solow [
]. In this thesis, a
nontopographical positive correlation between height of the
alveolar bone both in the maxilla and in the mandible,
in relation to craniofacial height, was demonstrated in
an adult sample. In more recent years, some studies have
reported height and width of either maxillary or
mandibular alveolar bone in relation to craniofacial height in
dry skulls [
] or patients [
Since its introduction in the late 1990s, cone beam
computed tomography (CBCT) has become a common
imaging modality that provides a three-dimensional data
set of the facial skeleton. To our knowledge, only one
study investigated the relationship between facial height
and alveolar bone morphology in the incisor and molar
regions of the maxilla and the mandible [
]. The aim of
this study was therefore, based on CBCT images of
subjects, to explore the association between the
crosssectional morphology of the maxillary and mandibular
bodies at several sites of the tooth-bearing regions and
The study is conducted in accordance with the
REporting of studies Conducted using Observational
Routinelycollected health Data (RECORD) guidelines [
This study was conducted on pre-treatment CBCT scans
collected from the archive at a private practice of
orthodontics in Scandinavia. Images were obtained from
patients, females over 15 years and males over 16 years,
which were referred for specialist orthodontic and
orthognathic treatment during 2008–2013.
CBCT scans from individuals with either missing
permanent teeth other than third molars, periodontal
disease visually detected on the radiographs, major
asymmetries of the jaws or who had previously
undergone orthodontic treatment were excluded.
Radiography and categorisation of craniofacial height
Radiography was performed using an i-CAT CBCT
(Imaging Sciences International, Hatfield, Pennsylvania,
USA). The patients were seated in an upright position,
with the head in natural head position. Field of view
(FOV) was 16 × 13 cm, acquisition time was 8.9 s with a
voxel size of 0.3 mm and exposure was set at 120 kVp
and 18.54 mAs with a total radiation dose of 458.6 mGy
cm2. Calibration of the i-CAT CBCT was performed
according to the manufacturer’s requirements twice a year.
Lateral head images were generated from the CBCT
scan using the i CAT software program. Cranio-facial
height was determined cephalometrically using the Total
Interactive Orthodontic Planning System (TIOPS)
The measurement used was the inclination of the
mandible in relation to the anterior cranial base. This is
the angle formed between the nasion-sella line (NSL)
and the mandibular line (ML), formed between menton
and gonion (Fig. 1). The subjects were categorised in the
three following groups: (i) a low angle (<27°), (ii) a
normal angle (27–37°) and (iii) a high angle (>37°).
Scans from 450 patients were available from CBCT
examinations performed during 2008–2013. After exclusion
due to criteria previously stated, craniofacial height was
cephalometrically determined for the rest of the scans.
After identifying 60 scans from low-angle subjects, this
number was set as the limit for the number of scans to be
consecutively included in the normal- and high-angle
groups for equal comparison. The number of individuals
in each group was consequently set at 60 subjects.
By using iCATVision™ software [
], a fully reconstructed
three-dimensional image with sagittal, coronal and axial
slices was generated. When measuring in the maxilla, the
nasion line (NL = a line from the anterior nasal spine
continuing posteriorly through the hard palate/nasal floor to
the posterior nasal spine) was used as the horizontal plane
and upper limit for vertical measurements in the maxilla.
When measuring in the mandible, the lower border of the
mandible was repositioned horizontally prior to
measurements. All measurements were performed by one of the
authors who only had access to the decoded CBCT scans and
blinded to all other patient information. Measurement
values were simultaneously recorded in a statistical spread
sheet by one of the other authors.
Measurements of the cross-sectional maxillary and mandibular height and width
Three-dimensional images were reconstructed by the
iCATVision™ software (version 126.96.36.199, Imaging Sciences
International) and saved in digital imaging [
Generation of cross sections: A curved line was mapped to fit
an axial CBCT section of the maxilla and mandible. Five
cross sections (facial-lingual) were generated on each
arch perpendicular to a tangent formed at these sites.
Facial-lingual = width and vertical long axis = height.
The height and width of the maxillary and mandibular
cross sections where measured between the dentition at
ten locations, five in the maxilla and five in the
mandible. Each cross-sectional slide was measured at three
sites, including one height and two width measurements
(Fig. 2). The sites were named according to location in
the following way: upper or lower jaw (UP or LO), molar
(MOL), premolar (PRE) and midline (MID) and finally
right (R) or left (L). Accordingly, UP-MOL-R stands for
upper molar on the right side, height (H) (total length of
the cross section), coronal width (W1) and apical width
(W2) (Fig. 2).
The height was determined and measured by a line
drawn through the long axis of the maxillary- or
mandibular cross-sectional area. When measuring in the
maxilla, the line was drawn perpendicular from the
alveolar crest to the NL which was set as the upper limit.
When measuring in the mandible, the line was drawn
perpendicular from the alveolar crest to the ML. The
height measurements then represented a total height,
which included both alveolar bone and basal bone. The
width measurements were recorded perpendicular to the
long axis line at two locations. One line was drawn at a
distance of one third and the other at two thirds of the
alveolar length. Fifteen measurements were performed
in the maxilla and mandible, respectively, giving a total
of 30 measurements (Fig. 2).
Measurements were performed by one observer. To
calculate intra-observer agreement, expressed as
intraclass-correlation (ICC), the observer re-measured 20% of
the sites in all the subjects after approximately 2 months.
These sites were chosen by using random sampling.
All statistical analysis was performed using IBM SPSS
software (version 22.0; IBM Corp Armonk, NY, USA).
For all variables, the three groups (low, normal, high)
were compared using a one-way analysis of variance
with a Tukey post hoc test. A significance level of 5%
was used in all comparisons.
The study was conducted in accordance with the ethical
principles of the World Medical Association Declaration
of Helsinki (2008 version), approved by the Regional
Ethical Review Board, Lund, Sweden (8 May 2014, Dnr
2014/288), the Danish Health and Medicines Authority,
Denmark (20 July 2015, Sagsnr. 3-30-13-877/1/), and the
Danish Data Protection Agency, Denmark (7 July 2015,
In both the maxilla and in the mandible, there was an
increase in height from the molar region to the incisal
region (midline) in all three groups. This increase was
more pronounced in the high-angle group (displaying a
steeper curve) and less pronounced in the low-angle
group (a flatter curve) (Fig. 3a).
The midline area (UP-MID), the premolar area
(UPPRE) and the molar area (UP-MOL) of the maxillary
cross section were significantly higher in the high-angle
group compared to the normal- and the low-angle
groups (Table 1).
The midline area (LO-MID) and the premolar area
(LO-PRE) of the mandibular cross section were
significantly higher in the high-angle group compared to the
normal- and the low-angle group. However, in the molar
region, there were no significant differences between the
groups (Table 1).
The range in height of the bone in the midline area
was between 11.6 mm (low angle) and 28.4 mm (high
angle) in the maxilla (Table 1).
The range in height of the bone in the midline area
was between 24.7 mm (low angle) and 42.1 mm (high
angle) in the mandible (Table 1).
Concerning the cross-sectional coronal width
measurements in the maxilla, Fig. 3b shows a V-shaped pattern,
meaning that there was a decrease in width of the
alveolar bone towards the midline area in all three groups.
This decrease was more pronounced from the molar to
premolar region for all three groups. Concerning the
apical width measurement, the figure showed that the
cross section was narrower in the premolar region
compared to the molar and midline area (Fig. 3b).
Concerning the cross-sectional coronal width
measurements in the mandible, Fig. 3c showed a V-shaped
pattern, meaning that there was a decrease in width
towards the midline area in all three groups. With
reference to the apical width measurement, the figure
showed that the cross section was significantly wider in
the midline area compared to the premolar and molar
area in all three groups (Fig. 3c).
There were no statistically significant differences in
width measurements in the maxilla when comparing the
three groups, neither in the coronal nor in the apical
width measurements (Table 2).
In the coronal and apical midline area in the mandible
(LO-MID), the bone was significantly narrower in the
high-angle group compared to the normal- and the
lowangle groups. In the molar area, there were no statistically
significant differences in the coronal or in the apical width
measurements between the three groups (Table 2).
The range in width, of the cross sections in the
coronal midline area, was between 4.1 mm (low angle) and
10.5 mm (high angle/low angle) in the maxilla (Table 2).
The range in width of the coronal part of the cross
section in the midline area was between 2.5 mm (high angle)
and 12.1 mm (low angle) in the mandible (Table 2).
In a majority of the cross-sectional measurements (73%),
significant differences were evident; male subjects tended
to have wider and higher cross sections compared to
female subjects. Males displayed approximately 1 mm larger
dimension of the maxillary and mandibular bone both in
vertical and horizontal measurements (Table 3).
One thousand eighty (20%) out of 5400 measurements
were randomly selected for re-measurement, and
intraclass correlation (ICC) was calculated for intra-observer
agreement. The correlation in height measures were
between 0.858 and 0.989. The correlation in width I
measures were between 0.762 and 0.944, and the correlation
in width II measures were between 0.696 and 0.923.
As CBCT is a rather new imaging modality, introduced
in the late 1990s, there were no European guidelines on
the use of CBCT for different dental- and maxillofacial
conditions at the time when the majority of images used
in this study were obtained. In 2012, European
guidelines for the use of CBCT were published [
] and there
is a continuous interest in stating precise selection
criteria following the principle of As Low As Reasonable
Achievable (ALARA) for the use of X-rays [
selection criteria for performing CBCT were
craniofacialand skeletal deviations, impacted teeth, patients planned
for orthognathic surgery and trauma patients, none of
which can be specifically disputed. It might be, however,
if a study like this should be performed prospectively
that selection criteria might be adjusted. Having access
to these retrospectively collected images, from which a
selection was used for this study, we considered it
unethical not to obtain clinically valuable data. Ethical
approval was obtained for the use of these available CBCT
images for research purpose.
Craniofacial height was determined cephalometrically
using the Total Interactive Orthodontic Planning System
(TIOPS) program [
] by one of the authors, a specialist
in orthodontics. This analysis is a standard tool in
orthodontic assessment and treatment planning. Observer
reliability of this technique has shown to be high, both in
(See figure on previous page.)
Fig. 3 Cross-sectional height and width morphology measurements of the maxilla and mandible in the three groups (low-, normal- and high angle).
UP-MOL-R (upper molar right), UP-PRE-R (upper premolar right), UP-MID (upper midline), UP-PRE-L (upper premolar left), UP-MOL-L (upper molar left),
LOMOL-R (lower molar right), LO-PRE-R (lower premolar right), LO-MID (lower midline), LO-PRE-L (lower premolar left), LO-MOL-L (lower molar left). Y-axis
(mm). a Height (H) measurement at five cross-sectional sites in the maxilla and five in the mandible. b Width (W) measurement at five cross-sectional
sites in the maxilla. W1 demonstrates the coronal width measurements, and W2 demonstrates the apical width measurements. c Width (W)
measurement at five cross-sectional sites in the mandible. W1 demonstrates the coronal width measurements, and W2 demonstrates the apical width
measurements. a Height in maxilla and mandible. b Coronal width. c Apical width
conventional lateral radiographs and in CBCT scull
]. Height and width measurements of the
maxillary and mandibular bodies was repeated at 20% of
the sites showing a moderate to almost perfect
agreement interpreted according to Landis and Koch .
Craniofacial morphogenesis evolves through an
interaction between the development of the facial tissue and
that of the supporting skeletal framework. In the present
study, focus has been on an aspect of craniofacial
morphogenesis, which is known as the dentoalveolar
compensatory mechanism. The present study indicates that
in a high-angle craniofacial pattern, the bone in the
mandibular midline is high and narrow, whereas in the
low-angle morphology, the bone is shorter and wider.
Gracco et al. showed no statistical difference in the midline
area of the maxilla between high-, normal- and low-angle
subjects on CBCT images. However, they investigated only
the anterior region of the maxilla [
]. These results are
not in agreement with our findings, which could be due to
that growing individuals (12–40 years) were part of the
study and some changes of the morphology of the
maxillary bone must be anticipated to occur as the individuals
]. The differences could also be due to a slightly
different measuring technique. In a recent investigation by
Sadek et al. [
], a significant difference in height of the
maxillary cross-sectional sites in the midline area was also
reported. However, no significant differences were found
in the molar region.
The subjects with the high-angle morphology revealed a
significant higher mandibular cross section in the midline
and premolar region when compared to the other groups.
These results are in accordance with Sadek et al. [
almost in accordance with the findings by Swasty et al.
]. The only difference was that Swasty et al.
demonstrated a negative correlation of the mandibular body in
the molar region, where the high-angle group had a
shorter body in the molar region compared to the
lowangle group [
]. The same feature was also described by
Kohakura et al. [
]. However, in the present investigation,
we could not demonstrate a statistical difference in height
in the molar region when comparing the groups. The
difference between the findings can be explained by the fact
that individuals who were still growing were included in
the Swasty study [
UP-MOL-R upper molar right, UP-PRE-R upper premolar right, UP-MID upper midline, UP-PRE-L upper premolar left, UP-MOL-L upper molar left, LO-MOL-R lower
molar right, LO-PRE-R lower premolar right, LO-MID lower midline, LO-PRE-L lower premolar left, LO-MOL-L lower molar left, x mean value
*Statistically significant difference (p value < 0.05)
at least in height of the bone, there seems to be a
midline. The same feature was described by Swasty et al.
]. In the alveolar coronal region, the mandible was
significantly thinner in the midline and premolar region
in all three groups. This is in accordance with the results
of both Swasty et al. and Sadek et al. [
Concerning the apical measurement, the cross section was
significantly wider in the midline area compared to the
premolar and molar area in all three groups (Fig. 3c).
This could be due to the anatomy of the mental spine
and the base of the mandible in the front region.
A general pattern was displayed, where the males
presented a greater height and width compared to the
females. Swasty et al. [
] described that there was no
statistical differences in cortical bone thickness between
the genders. However, they found a statistical difference
in height of the cross sections between males and
females. Accordingly, it seems reasonable to conclude that
The results of this investigation may support the fact
that the dentoalveolar compensatory mechanism aims to
maintain a functional occlusion in connection with
craniofacial growth. In the high-angle group, the alveolar
bone had to grow more in order to compensate or partly
compensate for the vertical craniofacial growth, and
therefore, the bodies of the maxilla and mandible
became higher. The fact that the arches became
narrower in the midline of the mandible might be due to
the difference in loading. It can be hypothesised that the
alveolar bone in the high-angle subjects are less loaded
than the bone in the low-angle group. In the low-angle
group, the root resides in most of the arch, whereas in
the high angle group, the root resides only in part of the
body, which according to Wolff ’s law will result in a less
developed bone [
In orthodontic treatment, it is very important to
understand how the development of the lower third of
the face is closely linked to the dentoalveolar
compensatory mechanism, because the dentoalveolar
compensatory mechanism can be influenced in connection with
Also during active orthodontic treatment, knowledge
of the morphology of the alveolar bone is important. In
thin ridges, the buccal and lingual cortices can contact
or be in close approximation with very little cancellous
bone. The risk for root resorption increases if the roots
are torqued into the cortex. In addition, there is a risk
for moving teeth out of alveolar bone that has a narrow
In connection with insertions of skeletal TADs, the
difference in the morphology of the cross section of the
maxillary and mandibular bodies in different growth
patterns is valuable information for therapy planning and
adequate therapy. It has been proven that in many
situations, the palate is an ideal area for screw insertion
where the screw is inserted at the third rugae with the
tip in an anterior direction [
]. However, knowledge
of the anatomy at the insertion site is important, and the
present study has demonstrated that the alveolar bone is
short in the mid-palatal area in the low-angle face
compared to the normal- and high-angle cases, with less
space superior to the apex of the incisors. Accordingly,
an increased risk of root damage and insertion of the
screw into the nasal cavity can be expected in low-angle
Likewise, during treatment planning for growing
patients with congenital missing teeth, the decision to
replace missing teeth with implants or by orthodontic
closure could be influenced by the expected development
of the dentoalveolar compensatory mechanism. The risk
of infra-occlusion of the implant supported crowns might
be higher in the high-angle group, where the incisors seem
to erupt more.
Vertical control is a common treatment approach in
high-angle cases, and appliances such as skeletal
anchorage devices are described as very useful [
considering the A-shaped morphology (Fig. 3a) of the
maxillary body in the vertical dimension, this treatment
approach will actually accentuate the difference in height
between the molar and incisor region. In orthognathic
surgery, the aim is to increase the vertical dimension in
the posterior region, which will flatten the same curve.
How this difference in treatment strategies, aiming to
solve the same problem, will influence final stability,
airways and function should be investigated further.
In treatment with dental implants, a careful
preoperative evaluation is important in order to achieve a
predictable, successful aesthetic outcome. The buccal bone
wall thickness is of crucial importance when it comes to
selection of appropriate treatment approach [
overall width of the mandibular body in a high-angle
subject tend to be thinner, which probably gives a
thinner alveolar bone. In the present study, the range in
width of the coronal part of the cross section in the
midline area was between 2.5 mm (high angle) and 12.1 mm
(low angle) in the mandible (Table 2). As suggested by
Buser et al., to achieve an aesthetic and functional
success in dental implant treatment, it is important to take
into account the three-dimensional aspect of the alveolar
]. It is recommended that the dental implant
should be placed inside the biological envelope of the
alveolar bone in order to obtain the best conditions for
The main findings of the present study were:
(1) The high-angle group had a significantly longer
cross-sectional area of the maxillary and mandibular
body compared to the other two groups.
(2) The high-angle group also had significantly
narrower mandibular cross-sectional body compared to the
other two groups, especially in the anterior region.
In this retrospective study, it has been demonstrated
that there is a close link between vertical craniofacial
development and the morphology of cross-sectional sites of
the maxillary and mandibular bodies for patients referred
for orthodontic and orthognathic treatment.
Understanding this biological link is important in connection with
many comprehensive dental- and orthodontic treatments.
There are no acknowledgements.
JB and KB have made substantial contributions to the conception and
design of the study. Acquisition of data and analysis and interpretation of
data have been made by JB, KB and AK. JB, KB, CL and AK have been
involved in drafting the manuscript or revising it critically for important
intellectual content. JB and CL also contributed to the general supervision.
All authors contributed significantly to this manuscript and have given final
approval of the version to be published.
Ethics approval and consent to participate
The study was conducted in accordance with the ethical principles of the
World Medical Association Declaration of Helsinki (2008 version), approved
by the Regional Ethical Review Board, Lund, Sweden (8 May 2014, Dnr 2014/
288), the Danish Health and Medicines Authority, Denmark (20 July 2015,
Sagsnr. 3-30-13-877/1/), and the Danish Data Protection Agency,
Denmark (7 July 2015, J.nr. 2015-41-4117).
Consent for publication
Not applicable. This manuscript has not been published elsewhere in part or
in entirety and is not under consideration by another journal.
The authors declare that they have no competing interests.
Springer Nature remains neutral with regard to jurisdictional claims in
published maps and institutional affiliations.
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