Anatomy, Embryology and Congenital Malformations in the development of the Oral Cavity

1. Oral Biology
Balidhawa Johnson
BDS, MAKchs

2. DEVELOPMENT OF THE SKULL
 The cartilaginous part –
forms bones of the
 The neurocranium has base of the skull.
two portions:
 The membranous
 The membranous part portion of the skull is
– consists of flat derived from neural
bones, which surround crest cells and paraxial
mesoderm.
the brain as a vault.
• Neurocranium

3. FACE DEV’T

4. NEW BORN SKULL
 At birth, separated from each
other by narrow seams of
connective tissue, the sutures.
•
Sigittal suture – from neural crest
cells
•
Coronal suture – from paraxial
mesoderm
 The anterior fontanalle, which is
the most prominent is found
where the two pariental and two
frontal bones meet.
 The bones of the vault continue to
grow, mainly because the brain
grows.

5. POSTNATAL GROWTH OF THE SKULL
•
Fibrous sutures of the
newborn calvaria permit the
brain to enlarge during
infancy and childhood
•
The increase in size of the
calvaria is greatest during the
first 2 yrs, the period of most
rapid postnatal growth of the
brain.
•
Most paranasal sinuses are
rudimentary or absent at birth.

6. VISCEROCRANIUM
 Consists of the bones of the
face
 Formed mainly from the first
two pharyngeal arches.
•
The first arch gives rise to a dorsal
portion,
•
The maxillary process, which
extends forward beneath the region
of the eye and gives rise to the
maxilla, the zygomatic bone and
part of the temporal bone.
•
The second pharyngeal gives rise
to the incus, malleous and stapes

7. CRANIOFACIAL DEFECTS
•
a) Cranioschisis
•
Cranial vault fails to form and the
brain tissue remains exposed
(anencephaly).
•
b) Meningocele
•
Skull forms but brain protrudes to
form a mass in the nape.

8. CRANIOFACIAL DEFECTS
•
c)
Scaphocephaly
Early closure of the sagittal
suture
•
d)
Plagiocephaly
•
Early closure of the coronal
and lambdoid sutures on one
side of the skull
•
e) Achondroplasia
Characterized by a large skull
with a small mid face

9. CRANIOFACIAL DEFECTS
Plagiocephaly
Achondroplasia
large skull with a small mid face
Early closure of the coronal and lambdoid sutures

10. CRANIOFACIAL DEFECTS
•
Craniosynostosis
Cranial abnormalities
caused by premature closure
of one or more sutures.
•
Examples;
•
- Apert syndrome
•
- Pfeiffer syndrome
•
- Crouzon syndrome
•
Microcephaly
-The brain
fails to grow and the skull fails
to expand

11. CRANIOFACIAL DEFECTS
Apert syndrome
Pfeiffer syndrome

12. DEVELOPMENT OF THE MANDIBLE
•
The mandible is the largest and
strongest bone of the face
•
i)
ii)
iii)
Represents the primitive vertebrate
mandible
 Meckel’s cartilage attains its full form
by the 6th week.
 The mandible is a membranous
bone.
•
BODY OF THE MANDIBLE
•
Ossification occurs in the 7th week in
the angle formed by the incisive and
mental nerves.
•
It is also the region of the future mental
foremen
ramus
•
•
body of the mandible
•
MECKEL’S CARTILAGE
3 Main parts form the mandible
•
•
alveolar bone

13. DEVELOPMENT OF THE MANDIBLE

14. THE ALVEOLAR BONE
•
As the enamel organs of
the decidous tooth germs
reach the early bell stage,
the bone of the mandible
begins to come into close
relationship to them.
•
This is brought about by
the upward growth on each
side of the tooth germs
then also the lateral and
medial plates of the
mandibular bone

15. THE RAMUS
•
The backward extension of the
mandible to form the ramus is
produced by a spread of
ossification from the
body, behind and above the
mandilular foremen,
 The ramus and its processes
are mapped by extension of
fibrocechular condensation.
 The formation of bone in this
tissue occurs rapidly so that
the coronoid and condylar
processes are to a large
extent ossified by the 10th
week.

16. THE FATE OF MECHEL’S CARTILAGE
• During
the later fetal
period nodules of
cartilage are seen in the
fibrous tissue of the
sympysis; (remnants of
the ventral end of
Mechel’s cartilage)
 The rest of Meckel’s
cartilage disappears
completely except for
apart of its fibrous
covering which persists
as;
• Spheno
mandibular and
spheno – malleolar
ligaments
• The
most dorsal part of
the cartilage ossifies to
form the incus and the
malleus.

17. THE MANDIBLE AT BIRTH
 Though perfectly
recognizable, it differs in
several respects from the
adult bones. The chief
differences are;
•
The wide angle, and small
size of the ramus compared
with the body.
•
The chin is usually poorly
developed, much of its growth
takes place after puberty.

18. DEVELOPMENT OF THE TEMPORAMANDIBULAR JOINT
 The constituent features of
the temporamandibular joint
include;
•
Articular surface of the
mandibular condyle
•
Articular surface of the
temporal bone
•
Articular disc
•
Joint capsule
•
Joint cavities
•
Articular ligaments

19. Temporarmandibular joint
•
•
•
Formation of the
temporarmandibular joint is first
indicated by the growth of tissue
condensation of the developing
mandible.
Which everywhere precedes
ossification, towards a
corresponding condensation in
the temporal region (12th week
in utero).
The mandibular condensation
maps out the shape of the
condyle.
 A strip of dense tissue above
the upper surface of the
condyle appears.
 It is then connected to the
lateral pterygoid muscle and
the strip of tissue becomes the
articular disc.
 Formation of joint cavities
occurs as the condyle
becomes approximated to
temporal element of the joint.
 Joint cavity development is
virtually complete between the
17th and 18th week.

20. CLINICAL ASPECTS
 Dislocation of the
temporomandibular joint
•
When opening the mouth, the
condylar head of the
mandible & articular disc
move anteriorly up to the
articular tubercle of the
zygomatic process of the
temporal bone.
•
During excessive opening of
the mouth, the condylar head
& articular disc of one or both
sides goes anteriorly beyond
the articular tubercle into the
infratemporal fossa.
•
As a result, there is inability to
close the mouth which
remains open.
•
Excessive opening of the
mouth can happen during
yawning, laughing or even
during tooth extraction.

21. CLINICAL ASPECTS
• Operations
of the temporomandibular joint
• During
operations of the TMJ, care should be taken
to preserve the branches of the facial nerve which
are closely related to it.
• If
the branches of the facial nerve are cut, facial
paralysis will result.

22. CLINICAL ASPECTS
•
Failure of growth of the condylar cartilages
•
Bilateral failure of growth of the condylar cartilages leads to
gross underdevelopment of the lower jaw.
•
Unilateral growth failure produces marked assymmetry of
the lower part of the face.

23. DEVELOPMENT OF THE MAXILLA
•
Each maxilla consists of;
i)
A body
ii)
A zygomatic process
iii)
A frontal process
iv)
An alveolar process
v)
Palatine process

24. DEVELOPMENT OF THE MAXILLA
 The maxilla proper is
developed in the maxillary
process of the mandibular
arch.
 Ossification of the maxilla
starts slightly later than in
mandible, in the 7th week.
•
The centre of ossification first
appears in a band of
fibrocellular tissue which lies
outer side of the cartilage of
the nasal capsule.
•
The ossification centre lies
above that part of the canine
from which develops the enamel
organ of the canine tooth germ.
•
Early in development, the
developing maxilla forms a body
trough for the infra orbital nerve
•
About the 8th week, a mass of
secondary cartilage appears to
form the zygomatic process.

26. THE FATE OF THE NASAL CAPSULE
•
 In the lower portions of the
lateral walls of the capsule, the
inferior turbinate bones
(conchea) develop.
Is the primary skeleton of the
upper face & analogous to
Meckel’s cartilage in the lower
part of the face
 In the upper portion of the
lateral wall of the cartilage, the
facial part of the ethmoid bone
develops.
 The two portions of the
ethmoid are united after birth
by the ossification of the
cribriform plate in the roof of
the capsule.
•
The intermediate region of the
capsule between the facial
ethmoid and inferior turbinate
atrophies.
 It is in this region that the
maxillary sinus extends
outwards from the nasal cavity
to invade the maxillary bone.
NB: The front of the nasal
septum remains cartilaginous
throughout life.

27. Clinical aspects:
• By
comparison with the • If teeth do not develop,
development of the
the alveolar processes
mandible which begins
are not formed.
earlier in the 6th week
and that of the maxilla,
7th week, even eruption
of teeth begins in the
lower jaw.

28. THE MAXILLARY SINUS
 First appears about the 4th month of fetal life as a small out-pocketing
of the mucosa from the lateral wall of the nasal cavity.
 Separated from the developing maxilla by the cartilage of the nasal
capsule and only comes into direct relationship with the bone after
the cartilage has a trophied.
 Gradual extension, the sinus comes into relation with the maxilla
above the level of the palatal process and hollows out the interior of
the bone.
 This leads to separation of its upper orbital surface from its lower
dental region.
 The final height of the maxilla is not reached until near the time of the
complete eruption of the permanent teeth.

29. CLINICAL ASPECTS
• An
inferior extension of the sinus into the base of the
alveolar process is of special practical significance;
 It establishes a closer relation of the sinus with the root
apices of the maxillary premolars and molars.
 In extreme cases the sinus even extends into the
alveolar process between the roots of the teeth so that
their sockets protrude into the cavity.
 The body floor of the sinus may even become
defective above the apices of the roots.

30. CLINICAL ASPECTS
•
As a result, the following
dangers are posed;
During
and molars can pass into
and infect the maxillary
sinus.
tooth extraction
(premolars and molars) the NB: Under development
maxillary sinus floor can be or even absence of the
damaged thereby creating maxillary air sinuses does
an oro-antral
not appear to affect the
communication.
size of the maxilla.
Infection
originating in the
root apices of premolars

31. DEVELOPMENT OF THE PREMAXILLA
 Formed in the region of
the junction of the
maxillary and frontonasal processes.
 A heavy trabecularized
network of bone appears on
the labial aspect of the
canine alveolus
 On the facial aspect, the
suture between the
premaxilla and maxilla can
still be seen until after birth
extending from the region of
the incisive foramen forward
to the alveolar process
between canine and the
lateral incisor.
 At
weeks of age, a
separate centre of
ossification appear for
the premaxilla.
7th
•

32. The End
Balidhawa Johnson
BDS, MAKchs