prenatal and postnatal growth of the human maxilla

1. Growth of the Maxilla
‫الرحيم‬‫الرحمن‬‫هللا‬ ‫بسم‬
Mohanad Elsherif
BDS (U of K), MFD RCSI, MFDS RCPS(Glasg), MSc (Orthodontics), M.Orth. RCSEd
University of Khartoum
Faculty of Dentistry
Department of Orthodontics

2. Outlines
 Introduction.
 Embryonic background.
 Anatomy of the maxilla.
 Prenatal development of the maxilla.
 Postnatal growth of the maxilla.
 Summery.
 References.

3. Introduction
 The nasomaxillary complex forms the middle part of the facial
skeleton and is dominated by the orbits, nasal cavity, upper jaw
and zygomatic processes.
 A number of bones make contributions to this region, including
the frontal, sphenoid, zygomatic, lacrimal, nasal, maxillary,
palatine, ethmoid and vomer.
 The maxilla grows downwards and forwards in relation to the
anterior cranial base, accompanied by the orbits and nasal cavity,
with all three regions increasing in volume as they grow.

4. Embryonic origins of the head
and neck
 The early embryo is derived from three primary germ layers of
tissue:
 Ectoderm (first germ layer).
 Endoderm (second germ layer).
 Mesoderm (third germ layer).
 There is also a further contribution from the neural crest (or
fourth germ layer).

8. The pharyngeal arches
 In humans there are six pharyngeal arches, which appear
progressively during the fourth week of embryonic
development.
 Each arch is covered externally by ectoderm and internally
by endoderm, whilst a core of mesodermal tissue exists within.
 As development proceeds, this central core becomes
infiltrated by cranial neural crest cells that migrate into the
arches from their site of origin adjacent to the roof of the
neural tube.

10. The pharyngeal arches
 The embryonic tissue components within each arch give rise to
specific structures:
 Ectoderm produces the skin and sensory neurons of the lower face
and neck.
 Endoderm forms the mucosal lining of the pharynx and associated
endocrine organs (thyroid, parathyroid and thymus) of the neck.
 Cranial neural crest cells produce most of the skeletal and connective
tissues within the head and neck.
 Mesoderm produces the associated craniofacial musculature, cardiac
outflow tract and endothelial cells of the pharyngeal arch arteries.

11. Anatomy of the maxilla
 The maxilla consist of:
1. body: large and pyramidal in shape.
2. Four processes:
 Frontal process.
 Zygomatic process.
 Palatine process.
 Alveolar process.
 The maxilla also houses the largest sinus
of the face, the maxillary sinus.

12. Prenatal development of the
maxilla
 The maxilla develops from the maxillary prominence
which extend ventrally from the dorsal aspect of much
larger mandibular swelling.
 The primary ossification centre appears for each maxilla
in the 7th week of IUL just above the part of the dental
lamina that form the deciduous canine tooth.
 The secondary ossification center appears at the
zygomatic, nasopalatine and orbitonasal areas.

13. Postnatal growth of the maxilla
 The postnatal growth of the maxilla occurs by three
mechanisms:
A. Displacement.
B. Sutural growth.
C. Surface remodeling.

14. Displacement
 The whole maxilla undergoes a simultaneous process of
primary displacement in an anterior and inferior direction.
 The nature of the force that produces this anterior movement
has, historically, been a subject of great controversy.
 One early theory (long since abandoned) suggested that
additions of new bone on the posterior surface of the elongating
maxillary tuberosity "push" the maxilla against the adjacent
muscle-supported pterygoid plates. This idea was now aborted.
Why?

15. Displacement
 Another theory held that bone growth within the various
maxillary sutures produces a pushing-apart of the bones, with a
resultant thrust of the whole maxilla anteriorly (and inferiorly as
well). Although this old explanation is still sometimes heard, it
has also been soundly rejected. Why?
 It is believed that the stimulus for sutural bone growth
(remodeling) relates to the tension produced by the
displacement of that bone.

16. Displacement
 An early explanation for maxillary displacement is the now famous "nasal septum"
theory, The hypothesis was soon adopted by many investigators around the world
and became more or less the standard explanation for a number of years.
 The basis for the "septal“ theory is that the pressure-accommodating expansion of
the cartilage in the nasal septum provides a source for the physical force that
displaces (pushes) the whole maxilla anteriorly and inferiorly.
 This sets up fields of tension in all the maxillary sutures. The bones then
secondarily, but virtually simultaneously, enlarge at their sutures in response to the
tension created by the displacement process.
 However recent experiments showed that the septum functions essentially to
support the roof of the nasal chamber, but does not actively participate in the
displacement movements of the palate itself.

17. Displacement
 A notable advance was made with the development of the functional matrix
concept, largely by Moss.
 The functional matrix concept also comes into playas a source for the
mechanical force that carries out the process of displacement.
 As the soft tissues continue to grow, the bones become passively (i.e., not of
their own doing) carried along (displaced) with the soft tissues attached to the
bones by the Sharpey fibers.
 Thus, for the nasomaxillary complex, the growth expansion of the facial
muscles, the subcutaneous and submucosal connective tissues, the oral and
nasal epithelia lining the spaces, the vessels and nerves, and so on, all
combine to move the facial bones passively along with them as they grow.

18. Displacement
 There are two basic reasons why this problem hobbled on unresolved, and why
such divergent opinions were inevitable:
 The first is that the source of maxillary displacement is multifactorial in nature.
 The second reason is that experimental studies usually involve surgical removal
of parts (such as the septum) to presumably test the nature of their functional
roles in growth. Such studies simply cannot account for the multiple variables
introduced by the experimental procedure itself, such as the destruction of
tissues, blood vessels, and nerves playing a role in the growth process.
 A basic point is usually not acknowledged: if one experimentally changes some
structure, as by surgical deletion, and this, in turn, affects the growth process,
one simply cannot thereby conclude that this structure, thus, "controls the
growth process."

19. Sutural growth
 During periods of sutural growth, the particular sutures that are
believed to contribute predominantly to maxillary growth are
those articulating with the frontal, zygomatic, ethmoid, and
palatine bones.
 Most sutures in the facial complex do not simply grow in
directions perpendicular to the plane of the suture itself.
 As the whole maxillary complex is displaced downward and
forward, or as it remodels by deposition and resorption, it
undergoes a frontal slide at sutural junctions with the lacrimal,
zygomatic, nasal, and ethmoidal bones.

20. Sutural growth
 The sutures do not represent special "centers“ of growth (and old but now obsolete theory).
A suture is just another regional site of growth adapted to its own localized, specialized
circumstances, just as all the other parts of the bone have their own regional growth
processes.
 Another old but invalid idea is that "the suture growth system closes down at a given age,
but the bone continues to enlarge simply by generalized surface deposition.“ Why?

21. Surface remodeling
 As the growing maxilla increases in size, there is a companion
process of remodeling which functions to maintain the constant
proportions of the bone’s shape and the relative positions of its
component parts.
 The different parts of the maxilla are growing and moving in a
complex variety of mesial (anterior), distal (posterior), superior,
inferior, medial (palatal or lingual), and lateral (buccal or labial)
directions.
 Therefore the over-all plan of maxillary growth is much more
complex than the simplified idea that maxilla grows ‘(downward
and forward by a process of bone deposition on posterior and
superior surfaces.

22. Surface remodeling

23. Surface remodeling

24. Summery
 The postnatal growth of the human maxilla parallels that
of the mandible in that forward and downward movement
of the growing bone as a whole is the net result.
 As the maxilla increases in size, its various parts and
regions come to occupy, in sequential order, new positions
in the bone.
 Therefore growth of the maxilla takes place in all Three
planes of space.

25. A-p direction (length)

26. Vertical direction (Height)

27. Transverse direction (width)
 Growth in the midpalatal suture.
 Remodeling at the lateral surface of the
alveolar process.

28. References
 Growth and remodeling of the human maxilla,
Enlow and Bang, Am. J. orthodontic 1965.
 Essentials of facial growth, Enlow and Hans, 1996.
 Handbook of orthodontics, Cobourne and DiBiase,
first edition, 2010.

29. Declaration
 The author wish to declare that; these presentations are his original work, all
materials and pictures collection, typing and slide design has been done by the
author.
 Most of these materials has been done for undergraduate students, although
postgraduate students may find some useful basic and advanced information.
 The universities title at the front page indicate where the lecture was first
presented. The author was working as a lecturer of orthodontics at Ibn Sina
University, Sudan International University, and as a Master student in Orthodontics at
University of Khartoum.
 The author declare that all materials and photos in these presentations has been
collected from different textbooks, papers and online websites. These pictures are
presented here for education and demonstration purposes only. The author are not
attempting to plagiarize or reproduced unauthorized material, and the intellectual
properties of these photos belong to their original authors.

30. Declaration
 As the authors reviews several textbooks, papers and other references during
preparation of these materials, it was impossible to cite every textbook and journal
article, the main textbooks that has been reviewed during preparation of these
presentations were:
Contemporary Orthodontics 5th edition; Proffit, William R, Henry W. Fields, and
David M. Sarver.
Handbook of Orthodontics. 1st edition; Cobourne, Martyn T, and Andrew T. DiBiase.
Clinical cases in orthodontics; Martyn T. Cobourne, Padhraig S. Fleming, Andrew T.
DiBiase, Sofia Ahmad
Essentials of orthodontics: Diagnosis and Treatment; Robert N. Staley, Neil T. Reske
Orthodontics: Current Principles & Techniques 5th edition; Graber, Lee W, Robert L.
Vanarsdall, and Katherine W. L. Vig
Evidence based Orthodontics; Greg J. Huang, Stephen Richmond, Katherine W.L. Vig.

31. Declaration
 For the purposes of dissemination and sharing of knowledge, these
lectures were given to several colleagues and students. It were also
uploaded to SlideShare website by the author. Colleagues and students
may download, use, and modify these materials as they see fit for non-
profit purposes. The author retain the copyright of the original work.
 The author wish to thank his family, teachers, colleagues and students
for their love and support throughout his career. I also wish to express
my sincere gratitude to all orthodontic pillars for their tremendous
contribution to our specialty.
 Finally, the author welcome any advices and enquires through his
email address: Mohanad-07@hotmail.com

32. Thank You