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FIGURE 33.8
Adolescent with type I OI with agenesis of the permanent maxillary right canine, but no DI.
(From ref.
48
)
Waltimo speculated that the sphenoid bone shape
was altered due to the deformation of the bones under
the strain of the brain, stating that “the craniofacial
form was altered as a result of differential growth defi-
ciency and bending of the skeletal head structures. We
found strong support both for an abnormally ventral
position of the sella region due to bending of the cranial
base, and for a closing mandibular growth rotation.”
52
This effect on craniofacial growth and development
would then contribute to the mandibular prognathic
(Angle Class III) malocclusion.
at the craniofacial level as they seem to present basi-
cally the same alterations on a continuum.
54
Types V and VI are dominantly inherited, while types
VII and VIII are autosomal recessive, and either moder-
ate, severe or lethal in the case of type VIII. Types V and
VI do not involve collagen-related genes.
Type I OI patients usually present an almost nor-
mal craniofacial development when compared to non-
affected individuals, with a tendency for a slight decrease
in the size of the jaws but still within normal variation
(
Figures 33.8 and 33.9
). DI may be present (
Figure 33.10
),
but is not as prevalent in type I as in type II, III or IV.
52,53
The number of class III malocclusions is still overly rep-
resented in the OI type I population but the expression of
the malocclusion is less severe (
Figure 33.11
).
12
As already noted, types III and IV present more
severe alterations of the development of the cranial
base. The base of the cranium is flattened, and the max-
illa is posteriorly inclined and retrusive. The anterior
cross-bite in Class III malocclusion in OI patients is
associated with a short maxilla and an increase in man-
dibular depth.
55
OI patients usually present an edge-to-edge occlu-
sion in the primary dentition, which evolves during
growth as the mandible exhibits an increased progna-
thism of variable severity into a negative anterior over-
jet and a Class III malocclusion (
Figure 33.12
).
56
This
malocclusion is usually associated with an anterior
cross-bite and affects over 60% of the OI population,
particularly those with OI types III and IV.
3
Craniofacial Manifestations by OI Type
Type I has fairly short stature and multiple frac-
tures. DI is present in 30% of the Montreal Children's
Hospital (MCH) population observed. Mild to
moderate craniofacial and occlusal alterations are
observed, but are somewhat comparable to the general
population.
53
Type III is the most severe type of the disease besides
type II, which is fatal in the neonatal period.
50
Patients
are very short in stature, present with very severe bone
fragility (multiple fractures) and are oftentimes wheel-
chair bound. Facially, they present a triangular face,
severe dentoalveolar anomalies, multiple impacted
teeth and very severe malocclusions.
50
Type IV is the most variable group and is close in
appearance to type III but manifestations are usually
less severe.
4
The two types are difficult to differentiate
