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CHAPTER
33
Oral-Facial Aspects of Osteogenesis
Imperfecta
Jean-Marc Retrouvey
1
, Stéphane Schwartz
2
and
James K. Hartsfield3
3
1
Montreal General Hospital and the Montreal Children's Hospital, Montreal, QC, Canada,
2
McGill University and Montreal Children's Hospital, Montreal, QC, Canada,
3
University of Kentucky,
Lexington, KY, USA, Indiana University School of Dentistry and Indiana University School of
Medicine, Bloomington, IN, USA, University of Illinois-Chicago College of Dentistry,
Chicago, IL, USA
INTRODUCTION
THE DE
NTITION IN CHILDREN W
ITH OI
Osteogenesis imperfecta (OI) is a connective tissue
disease most commonly involving type I collagen that
affects many organs in the body, and has a profound
effect on the skeleton.
1
Clinical management of OI is
multidisciplinary, including physical rehabilitation and
surgical procedures, as well as management of hearing,
pulmonary, dental and other abnormalities.
2
In addi-
tion to dental abnormalities including dentinogenesis
imperfecta (DI) and/or other anomalies, craniofacial
variations are also reported including maxillary hypo-
plasia and mandibular prognathism.
3
Sillence described the clinical classification of OI
in four distinct types, which are not in order of sever-
ity. Type I is the most benign, type II is typically lethal
at birth, type III is the most severe group who survive
birth, and type IV is the most clinically diverse.
4
Rauch
and Glorieux presented an update of this classifica-
tion in 2004, adding more types to the Sillence initial
classification.1
1
Advances in mutation analysis have
expanded the clinical designation to eight OI types, two
of which, types VII and VIII, are recessively inherited
(see Chapter 2). In general, the more prevalent autoso-
mal dominant types (I-IV) of OI are caused by primary
defects in type I collagen, whereas autosomal recessive
forms are caused by deficiency of proteins that interact
with type I procollagen for post-translational modifica-
tion and/or folding.
2
At the 28th day of embryonic development, the first
branchial arches develop bilaterally into maxillary and
mandibular arches. In the following 18 to 24 days, the
dental lamina is formed from ectoderm. The primary
dentition dentin starts its formation at 18 weeks
in utero
,
and the permanent dentition dentin at 32 weeks (end
of the bell stage). Except for enamel, the entire tissue
of the tooth and its supporting network consist of con-
nective material derived from ectomesenchyme, where
the prevailing cells are the fibroblasts. These cells play a
paramount role in the development, structure and func-
tion of the tooth.
5,6
Collagens are extracellular molecules synthetized
by fibroblasts. Type I collagen is abundant in dentin,
periodontal ligament, cementum and most other con-
nective tissues. It represents 86 to 90% of the organic
content of the dentin and 90% of its cementum. This is
the reason why it occupies such a prominent part of this
text.
6,7
Ninety percent of cases of OI are of type I, II, III,
IV and V. Except for type V, type I collagen is the faulty
element in all of them, but at different levels of severity.
Type I OI depicts a milder phenotype of the syndrome
and, even though the defects are present, they are not
striking because the affected individuals' dentitions do
not look much different from those of the general pop-
ulation. In type I OI, the collagen is affected quantita-
tively instead of qualitatively. The dental abnormalities
