Growth of Nasomaxillary Complex and Mandible Copyright by Ortho Department, Yangon

1. Growth of Nasomaxillary complex

2. Nasomaxillary complex.
Growth mechanisms of nasomaxillary complex :-
Bone deposition and resorption.
Displacement (primary and secondary displacements).
Remodeling.
Sutural growth.

4. Maxillary tuberosity.
It is one of the major sites of growth. Bone is deposited in
three directions on the posterior surface of maxillary
tuberosity.
It lengthens posteriorly along the arch by bone deposition on
its posterior facing surface.
It grows laterally and widens that part by deposition on its
buccal surface.
It grows downard by deposition of bone over the alveolar
ridge.
 Bone resorption occurs on the endosteal surface and
contributes to the enlargement of maxillary sinus.

6. Therefore bone deposition and resorption on the posterior
surface of maxillary tuberosity results in:-
Horizontal elongation of the maxillary alveolar arch.
Widens that part of tuberosity laterally.
Causes vertical growth of the alveolar bone.
Contributes to enlargement of the maxillary sinus.

7. Primary displacement.
The whole maxilla undergoes a simultaneous process of
primary displacement in an anterior and inferior direction as it
grows and lengthens at posterior and superior craniomaxillary
sutures and maxillary tuberosity.

8. The nasomaxillary complexas it emerges from beneath the
cranium

9. The nature of force that produce the displacement
movement has been a subject of controversy.
Push theory.
Nasal septum theory. (Scott)
Functional matrix theory. (Moss)

10. Functional matrix theory.
States that any given bone grows in response to
functional relationship established by the sum of all the soft
tissues operating in association with that bone.
Thus the nasomaxillary complex passively moves
along with the expansion of the facial soft tissues, including
muscles, subcutaneous tissues, submucosal tissues, oral
and nasal epithelium lining the spaces, the blood vessels,
nerves etc.

11. Secondary displacement.
The expansion of the middle cranial fossa has a major
secondary displacement effect on the anterior cranial base, the
nasomaxillary complex and the mandible.
The enlargement of the middle cranial fossa produced a
like amount of forward displacement for both the anterior cranial
fossa and the nasomaxillary complex.

12. Sutural growth.
The passive displacement of the maxilla triggers sutural
membrane to form new bone tissue at the sutures.
(frontomaxillary, zygotemporal, zygosphenoid, zygomaxilla,
ethmomaxilla, ethmofrontal, nasofrontal, frontolacrimal,
palatine and vomerine sutures)
The amount of primary displacement exactly equals the
amount of new bone deposition at the sutures and
growth at posterior surfaces of maxillary tuberosity.

13.  Therefore the overall size of the whole bone enlarges and
sustain constant bone to bone sutural contact.
 The direction of primary displacement is downward and
forward while the maxilla grows upward and backward by
sutural growth.

14. The placement of the various sutures

15. Growth at various craniomaxillary sutures.

16. Remodeling growth.
As the maxilla is displaced downward and forward its front
surfaces are simultaneously remodeled.
The bone is removed from most of the anterior surfaces of the
maxilla.
 Vertical crest just below the malar protuberance is the ‘key
ridge’.
Remodeling growth anterior to this ridge is resorptive and
posterior to this ridge is the area of periosteal deposition.

17.  Thus the surface mesial to the key ridge provides inferior
direction of arch growth by resorption while depository surface
distal to the key ridge grows downward by periosteal
deposition.

18. a = inferior direction of growth by periosteal deposition.
b = inferior direction of growth by periostea resorption.

19. Palatal and orbital floor.
The palatal and orbital floor are displaced downward and
forward by the process of primary displacement.
The extent of this downward displacement of palatal floor is
much greater than the displacement of the orbital floor
The palate grows downward by the periosteal resorption
on the nasal side and deposition on the oral side.
In addition the palate also moves downward passively together
with the primary displacement of the nasomaxillary complex.
The remodeling process serves to enlarge the nasal chamber
and relocate the palate downward.

20. Orbital floor.
Bone deposition takes place on the intraorbital side of the orbital
floor and resorption on the maxillary sinus side. This remodeling
process (cortical drift) moves the orbital floor upward.
The orbital floor also moves passively downward by the primary
displacement of the nasomaxillary complex.
The downward primary displacement of the maxilla is thereby
compensated by the upward remodeling growth to the amount
that is enough to accommodate the small enlargement of orbital
soft tissues.
Thus the orbital and palatal floor are displaced downward in the
same direction but they are undergo remodeling growth in the
opposite direction.

21. The alveolar bone and teeth.
Height.
The vertical drift or downward movement of the teeth in its
own socket is accomplished by the remodeling growth as the
socket drifts inferiorly by deposition and resorption.
As the whole maxilla is displaced downward the teeth, the
entire bony arch and the teeth sockets are passively displaced
downward together with the maxilla.
These growth movements occur in addition to tooth eruption
process.
Orthodontic treatment has the advantage of controlling the
downward movement of teeth by orthodontic and orthopaedic
means.

22. Width.
Alveolar remodeling contributing to vertical growth is also
important in attainment of width because of the divergence of
the alveolar process. As the alveolar bone grows vertically this
divergence increases the width.
Growth at median palatal suture is important in the
development of the width of the palate.
In addition transverse rotation of the maxillary halves results in
separation of the halves more at posterior than anterior.

23. Vertical remodeling growth contributes to increase in width.

24. The expanding 'V' in the
downward and forward growth
of the maxilla

25. Clinical importance.
Sutures are the sites where the growth of the nasomaxillary
complex can be influenced by orthodontic treatment. Eg.
Traction from extraoral head gear, reversed head gear and mid-
palatal expansion.
Sutures are the sites where the craniofacial anomaly
commonly occurs. Eg. Cleft palate
Altered function eg. oral respiration, tongue thrust swallowing,
influenced the growth of the associated skeletal structures.
Variations in the growth and morphology play important in role
in the development of dentofacial anomaly and malocclusion.

26. Growth of Mandible

27. Mandible.
Growth of the mandible involves :-
remodeling growth
bone deposition and resorption ( cortical drift)
Cartilagenous growth
Displacement

28. Remodeling growth.
The bony maxillary arch lengthens by deposition of bone on its
posterior facing surfaces of maxillary tuberosity.
This calls for the lengthening of the mandibular corpus to an
extent that matches its counterpart – the maxillary tuberosity.
Therefore the posterior growth of the mandibular bony arch
must proceed into a region already occupied by the ramus.
This requires a remodeling conversion from ramus to
mandibular corpus.
The whole ramus relocated posteriorly and the former anterior
part of the ramus is structurally converted into an addition for the
corpus and thus lengthened by remodeling process.

30. Lingual tuberosity.
Bone deposition occurs on the posterior facing surface of the
lingual tuberosity.
It grows in an almost directly posterior direction with only a
relatively slight lateral shift.
Below the lingual tuberosity is an area of bone resorption and
this resorptive field produces a sizable depression, the lingual
fossa.

32.  Together with the bone deposition on the posterior facing
surface of the lingual tuberosity, that part of the ramus just
behind the tuberosity grows medially by bone deposition.
 This produces the medial direction of drift that shifts this part
of the ramus into alignment with the axis of the arch and thus
become a part of the corpus.

34. The bony arch length has been increased and the corpus length
has been lengthened by :-
 deposition on the posterior surface of the lingual tuberosity
and the contiguous lingual side of the ramus.
 a resultant lingual shift of this part of the ramus to become
added to the corpus.
 Except for the resorptive zone on the lingual side the
remainder of the perimeter of the mandibular corpus
receives progressive deposits of bone.
 This enlarge the length of each side of the corpus.

37. Anterior and posterior border of ramus.
The remodeling resorption on the anterior border of the ramus
and the simultaneous deposition on its posterior border results
in progressive relocation of the entire ramus in a posterior
direction.
The growth of the posterior border of the ramus necessarily
keeps pace with any given amount of condylar growth.
Together they represent the most active area during
mandibular growth.

38. Coronoid process.
Bone deposition occurs on the posterior, superior and medially
facing surface of the coronoid process.
Because of growth at superior and medial facing surface of
coronoid process that part of the ramus becomes lengthens
vertically.
Growth at posterior facing surface of also produces a backward
movement of the two coronoid processes.
The buccal surface of coronoid process has a resorptive type of
periosteal surface.

39.  The remainder of most of the superior part of the ramus , the
area below the sigmoid notch and the superior portion of the
condylar neck grows superiorly by deposition on the lingual
side and resorption from the buccal side.
 The lower part of the ramus below the coronoid process has
a depository type of surface on buccal side and the opposite
lingual side has resorptive type.

40. Mandibular foramen.
While the whole ramus grows posteriorly and superiorly, the
mandibular foramen drifts backward and upward by deposition
on the anterior and resorption from the posterior part of the its
rim.
This maintains the constant position midway between the
anterior and posterior borders of the ramus.

41. Antegonial notch.
The surface resorption on the inferior edge of the mandible at
the ramus and corpus junction forms the antegonial notch.

42. The mandibular condyle.
The condyle is a major site of growth having considerable clinical
significance.
However, it is not a master center of growth and all the other
growth fields are not dependent upon it for direct control.
 The condylar cartilage is a secondary type of cartilage.
 It does not developed by differentiation from the established
primary cartilages of the skull.

43.  It is believed that the unique connective tissue covering of the
condyle is actually an original periosteum.
 Its undifferentiated connective tissue stem cells develop into
chondroblast rather than osteoblast because of the
compressive forces acting on the membrane.
 Therefore, adventitious type of secondary cartilage develops
instead of bone because of the functional and developmental
condition imposed upon it.

46.  The function of condylar cartilage is to provide regional adaptive
growth to maintain the condylar region in proper anatomic
relationship with the temporal bone as the whole mandible is
simultaneously being carried downward and forward.
 The proliferative process at condylar cartilage produces the
upward and backward growth movement of the condyle.

47.  While this is going on the periosteum and the endosteum
are active in producing the cortical bone that enclosed the
medullary core of endochondrial bone tissue.
 The anterior edge of the condylar neck is depository and
forms part of the sigmoud notch.
 The posterior edge is also a depository and blends with the
posterior border of the ramus which grow posteriorly.

50. The alveolar bone.
The growth and remodeling changes of the ramus and middle
cranial fossa produce the lowering of the mandibular arch.
To bring the upper and lower teeth into occlusion, the
mandibular teeth drifts upward vertically.
The amount of upward mandibular tooth drift is much less than
the downward drift and displacement of the maxillary teeth.

52.  During the vertical drift of mandibular teeth, the anterior
mandibluar teeth simultaneously drift lingually and
posteriorly.
 The remodeling process that bring about this involves the
periosteal resorption on the labial side of the labial bony
cortex, deposition on the alveolar surface of the labial
cortex, resorption on alveolar surface of the lingual cortex
and deposition on the lingual side of the lingual cortex.

54. Displacement.
The physical force that carry the forward and downward primary
displacement of the mandible is a matter of controversy.
The growth of condylar cartilage against the articular contact
surface pushes the whole mandible.
Functional matrix theory.
The mandible is carried downward and forward in conjunction
with the growth expansion of the soft tissue matrix associated with
it.
As the mandible is displaced away from its articular contact the
condyle secondarily grows toward the articular contact thereby
closing the potential space without an actual gap being created.