The document details the developmental processes of the mandible and maxilla, explaining that the mandible forms by intramembranous ossification and is influenced by Meckel’s cartilage. It outlines the stages of mandible development, including the body proper, alveolar process, and ramus, emphasizing the role of secondary cartilage and bone deposition in growth. For the maxilla, it describes its formation from two bones and the effects of sutural growth and various bone deposition methods on its size and shape.

1. Development of mandible
and maxilla
By : Dr/ Hanaa Salem Moubarak
Lecuturer of Oral Biology
Minia University

2. Anatomy of mandible

3. Development of mandible
• Develops in mandibular process of the
1st arch by intramembranous
ossification
• Preceded by Meckel’s cartilage
• Meckel’s cartilage on both sides
extends from otic capsule to midline &
joined by mesenchyme and covered by
thick fibro-cellular tissue.
• At that time Meckel’s cartilage has
close relationship to mandibular nerve
forming skeletal support for it & its
branches.

4. • At junction of dorsal and middle
thirds of Meckel’s cartilage
mandibular nerve is divided into:
• Lingual nerve runs medial to the
cartilaginous rod.
• Inferior alveolar nerve run lateral &
parallel to the upper rod margin,
terminates by dividing into incisive and
mental branches
• The incisive n. continues to the cartilage
end.

5. Development of mandible
Mandible development occurs through intramembranous
ossification in 3 steps :
1. Development of body proper
2. Development of alveolar process
3. Development of ramus

6. Development of body proper (neural element)
• Start by appearance of dense fibrocellular band on
lateral aspect of Meckel’s cartilage.
• At about 7 W.I.U.L, a center of intramembranous
ossification appears as condensed band of fibrocellular
tissue at the angle between incisive and mental nerves.
• Ossification spreads from this center in different
directions:
• Backward below mental n. forming a groove then
surround the nerve forming the mental foramen.
• Forward under incisive n. forming a trough of bone
extending to the midline to meet the one of opposite side.
• Backward along the lateral aspect of Meckel’s cartilage
proceeding to point of mandibular n. division, forming a
trough.
Both troughs are converted into canals by formation of
lateral & medial plates that unit above the incisive n.
(incisive canals) & inferior alveolar n. (inferior alveolar
canal).

7. • The ossification stops at the site of future lingula.
• By these processes, the primary center of ossification produces
the body of the mandible as far backward as mandibular
foramen and far forward as the symphysis menti which remain
separated by fibrous tissue.
At this stage, the
developing tooth germs
lie with little distance
superficial to the
developing mandible &
not contained in its
bony.

8. 2- Development of alveolar process
• Median and lateral plates of alveolar bone grow upward to
include developing tooth germs.
• So, the germs become contained inside a trough of alveolar
bone.
• Bony septa are formed to divide the trough into compartments
each contain single tooth germ (bony crypt formation).

9. 3- Development of ramus
• The ramus & its process are mapped out by extension of
mesenchymal condensation in which intarmembranous
ossification occurs
• Spread of ossification rapidly occurs behind and above the
mandibular foramen.
• Coronoid and condyloid processes are ossified at 10 W.I.U.L
N.B mandible is formed by intramembranous ossification with no
direct involvement of Meckel's cartilage TILL 10 W.I.U

10. Further growth of mandible is modified by appearance of
3 cartilagenous centers called ( secondary or accessory
cartilage)

11. SECONDARY CARTILAGE :
• These are 3 accessory cartilages appear in the developing mandible
• They are not part & no connection with Meckel’s cartilage
• Histologically: large cells & less intercellular matrix than hyaline c. of
primary skeleton.
Symphsial

12. Condylar cartilage
• First to appear and largest one.
• Appears at 12 W.I.U.L on bone of the small condyle
• Carrot shaped mass occupying most of developing ramus
• This mass is converted to bone by endochondral ossification.
• Gives rise to head & neck of condyle and posterior half of
ramus above mandibular foramen
• Remains active till 20 years of age

13. Coronoid cartilage
• Appears at 14th W.I.U.L as a strip of cartilage above the anterior border and top of
coronoid process.
• Gives rise to coronoid process & anterior half of ramus above mandibular foramen.
• Disappears long before birth (6 M.I.U)
Symphysial cartilage
• Appear at about 16th W.I.U at the symphyseal end
of each half of the body of mandible.
• Cartilage of both sides are connected to each
other connective tissue.
• Osseous union of the two mandibular halves by
the end of the 1ST year of life or at the beginning
of the second year.
• Enable mandible to grow in width

14. Mental ossicles
• They are 2 or 4 nodules of cartilage
• Appear in the c.t of symphysis at 7 M.I.U
• Remenant of Meckel’s cartilage
• Ossify & enlarge and fuse with each other & with mandible to
form mental protubrance

15. Fate of Meckel’s cartilage
• Anterior part : mental ossicles
• Posterior part:incus& mallus bone
• Middle part: lingula of mandible
• Fibrous capsule: sphenomandibular ligament

16. Growth of the mandible

17. 1. Secondary cartilages
2. Subperiosteal bone deposition
3. Development and growth of alveolar
process
Mandibular growth occur through :

18. Secondary cartilages
• The most important of them is the condylar cartilage
• Condylar cartilage grows in upward and backward direction so shift
mandible in downward and forward direction
• Increases the length of ramus & overall length of mandible
• Increases intercondylar distance

19. Development and growth of alveolar process
• Deposition of bone in the fundus of
socket and at the crest of alveolar
process increases the height of
mandibular body.

20. Subperiosteal bone deposition and resorption
• Bone deposition on surface of mandible
increase its overall size.
• On the posterior border of ramus with resorption on
the anterior border ++ length of the
dental arch
• On the lower border of the body ++ the height of
mandible.
• At the angle of mandible (& resorption from inner
side) ++ the transverse distance posteriorly
• On the external surface of mandible: ++ thickness of
the body.
• In the chin region influenced by sexual & genetic

23. Development
of maxilla

24. Anatomy of maxilla

25. Maxilla is formed or 2 bones, maxilla proper and premaxilla
Development of maxilla
Development of maxilla proper:
• Develops in maxillary process of mandibular arch by
intramembranous ossification
• Centre of ossification appears as band of fibrocellular
tissue at the outer side of cartilaginous nasal capsule
lateral and slight below infraorbital nerve where it
gives off ASA n.
• This center of ossification lies above the dental lamina
of the deciduous canine.

26. 1. Backward below orbit & toward zygomatic
bone to forming zygomatic process of
maxilla
2. Forward toward the premaxilla
By backward & forward extension of ossification a
trough is formed below infraorbital nerve that is
converted to bony canal which opens by infraorbital
foramen
3. Upward to form frontal process of maxilla
4. Downward to form outer alveolar plate
The inner alveolar plate develops later
from junction of palatal process with body of
maxilla
5. Inward to form palatal process (forming the
hard palate)
From this center ossification spreads in different directions :

27. GROWTH OF MAXILLA
1- Sutural growth
• Intramembranous bone growth is
achieved through bone formation within
a periosteum or by bone formation at
sutures.
• Sutures are formed during embryonic
development at the sites of
approximation of the membranous
bones of the craniofacial skeleton. They
serve as the major sites of bone
expansion during postnatal craniofacial
growth.

28. 4 main sutures are present in maxilla
parallel to each other:
1. Fronto-maxillary suture.
Between the frontal process of the maxilla & the
frontal bone.
2. Zygomatico-maxillary suture.
Between the zygomatic bone & maxilla.
3. Zygomatico-temporal suture.
Between the temporal process of the zygomatic
bone & the zygomatic process of the temporal
bone.
4. Pterygo-palatine suture.
Between the pyramidal process of the palatine
bone & the pterygoid process of sphenoid bone.
1
2 3
4

29. Growth of these sutures will displace the maxilla
downwards & forwards

30. 2- Sub-periosteal bone deposition:
overall increase in size of maxilla.
3- Bone ++ in the tuberosity region: increase
in anteroposterior dimension of maxilla.
4- Development & growth of the alveolar
process: increase in the height of the maxilla.
5- Growth of the maxillary sinus:
By bone resorption from inside the sinus & bone
deposition on the facial surface of the maxilla
(Pneumatization)

31. 6- bone deposition in the floor of
the orbit: increase in the height of the
maxilla.
7- Bone deposition in the oral
surface of the hard palate with
resorption at the floor of the nasal
cavity, leading to increase in the height
of the maxilla.
8- bone deposition at the median
palatine suture. increases the width
of the palate.

32. 9- Appearance of secondary (accessory)
cartilage:
• Has little effect on growth of maxilla (the opposite
with mandible)
• During early development of maxilla (8 W.I.L),
mass of cartilage appear in the zygomatic process
(zygomatic or malar cartilage)
• May appear along the growing margins of
alveolar plate