Developmental
abnormalities of the face, palate, jaws and teeth
Treacher
Collins’ syndrome (Fig. 37.14)
Treacher Collins’ syndrome or mandibular
facial dysostosis has a variable presentation. The cardinal features are of an
Crouzon’s
disease (Fig. 37.15)
This is also known as craniofacial dysostosis
and may occur together with syndactyly. This is a genetic disease characterised
by protruberant frontal bones, a hypoplastic maxilla with relative mandibular
prognathism. The hypoplasia may be so severe that the globes of the eye are
protruberant to a degree that corneal ulceration and loss of sight can occur.
There may well be a hyperteliorism and divergent strabismus. Most patients have
a normal cerebral function.
Pierre
Robin’s syndrome
This condition is characterised by
micrognathia (small lower jaw) and glossoptosis. There is almost always a cleft
palate. The overall impression is of bird faces. It does not appear to be an
inherited syndrome and it has been thought that extreme flexion of the neck
during foetal life may contribute
Hemifacial
microsomia (first arch syndrome —Fig.
37.16)
In this condition tissues which seem to have
been derived from the first branchial arch are deficient. A better understanding
of the embryology, and experimental work by Poswillo, have indicated that
there may be haemorrhage from the stapedial artery around the sixth week of
intrauterine development. Tissues that were in development at that time are
damaged by the haemorrhage and the subsequent reorganisation so that tissues
are smaller or fail to develop completely. The expression is variable but there
is always hypoplasia or absence of the mandibular condyle and part of the ramus
of the mandible. The masticatory muscles are deficient, and the external, middle
and inner ear may fail to develop. Thus, there is the appearance of hypoplasia
or the affected side of the face and head with the pinna absent and the external
auditory meatus rudimentary or absent. Skin tags over the side of the face
beneath the ear are common. The child is
Maxillomandibular
disproportion
Angle, an American orthodontist, put the
occlusion of the teeth into three classes:
•
class I — normal relationship of the lower to the upper teeth in the
molar area;
•
class II — the lower molar teeth are placed posterior to the normal
position;
•
class III — the posterior molar teeth are placed anterior to the normal
position.
This
classification has been extended to include the facial skeleton such that:
•
skeletal II — small mandible is placed posterior to the normal position
in relation to the maxilla;
•
skeletal III — mandible is placed anterior to the norms position
relative to the maxilla.
It is a helpful description of a facial
skeletal deformity, but it only describes the mandible in relation to the maxilla
which itself may be hyperplastic or hypoplastic. Thus, the. ‘Hapsburg jaw’
which described the familial features of the royal houses of Europe in the
nineteenth century describes large lower jaw, a hyperplastic mandible, which is
frequently associated with a hypoplastic maxilla which accentuates the deformity
in the mandible.
The
most common deformity of the facial skeleton in the Caucasian is the hypoplastic
mandible — skeletal class II -which gives the impression of a hyperplastic
maxilla as the upper teeth are very prominent. A hyperplastic maxilla alone is
very unusual. Bimaxillary protrusion is a racial characteristic of the African
races. Occasionally the mandible may grow large and asymmetric owing to
hyperplasia of the mandibular condylar neck. Rarely, a hemimandible may be
hypoplastic.
Orthognathic
surgery
Orthognathic surgery is the term given to the
correction of deformities of the teeth and jaws. It should always be undertaken
in close co-operation with consultant orthodontists and consultant oral and
maxillofacial surgeons. Correction of maxillomandibular disproportion is
frequently directed towards changing the position of both the maxilla and the
mandible, usually at the end of the growth period. It is essential that there
should be a team approach, with treatment planning usually commencing at the age
of 12—13 years. Treatment of the syndromes, some of which are described above,
may require much earlier treatment (see below). The orthodontist prepares the
dental arches for their new position preoperatively, and continues
postoperatively with the ultimate goal of a perfect dental occlusion within 6
months of the surgery.
The
orthognathic surgery is generally carried out through incisions within the mouth
avoiding skin incisions where possible. The upper and lower jaws are mobilised
individually and fixed by means of small stainless steel or titanium plates
and fixed by means of stainless steel or titanium miniplates. Splinting of the
upper and lower teeth by various means is undertaken intraoperatively to achieve
an accurate and planned occlusion. Usually it is possible to leave the mandible
free for the mouth to be opened at the dangerous times in the first 24 hours
postoperatively. An example of maxillomandibular disproportion may be seen in
Fig. 37.17, with the effect of bimaxillary surgery in Fig.
37.18.
Craniofacial
surgery
Craniofacial surgery is undertaken in a few
designated centres in the UK where the team of an orthodontist and a
New
developments in osteogenic distraction in the early growth period in the severe
abnormalities may greatly change and reduce the major surgery that is currently
undertaken on patients with facial deformity.