Growth & development of cranial basae & vault

GROWTH AND DEVELOPMENT OF
CRANIAL BASE
&
CRANIAL VAULT
Seminar
on
www.indiandentalacademy.com

Contents
• Introduction
• Osteogenesis
• Prenatal growth
• Cranial base flexure
• Uneven nature growth of cranial base
• Postnatal growth
• Growth of cranial vault
• Cranial base
• Conclusion
• Bibliography

INTRODUCTION:
 Cranial base or Basicranium as it is known comprises of three
bones, namely ethmoid, sphenoid, and occipital bone. Internal
surface of the cranial base shows a natural division into anterior,
middle and posterior cranial fossae. It is very irregular owing, partly
to the impression for the cerebral gyri, which are especially
conspicious in the anterior and middle fossae, where they reflect
accurately the pattern of the surface of the corresponding parts of
the cerebrum.
 It is often assumed that the face is more or less independent of the
cranial base, that facial growth processes and the topograhic
features of the face are unrelated to the size and shape and growth
of the floor of the cranium. This is not the case at all, what happens
in the cranial base very much affects the structure, dimensions,
angles and placement of the various parts. The reason is that the
cranium is the template upon which the face develops.

 Skull is composed of neurocranium, face and masticatory
apparatus:
 NEUROCRANIUM CALVARIA
 CRANIAL BASE
 FACE ORO-GNATHO FACIAL
COMPLEX
 MASTICATORY
APPARATUS DENTITION
 Cranial base to some extent is shared by neurocranium and
facial elements.
 Masticatory apparatus is by facial and dental elements
 The total skull is thus a mosaic of individual component each of
which enlarges during growth in the proper amount and direction
to attain and maintain stability of the whole.
Introduction:

SKULL:
The skull can be divided into two parts;
Neurocranium which forms a protective case around the
brain, and the viscerocranium which forms the skeleton
of the face.
NEUROCRANIUM:
The neurocranium is most conveniently divided into two
portions
a) The membranous part: consist of flat bones, which
surrounds the brain as a vault, and
b) The cartilaginous part or chondrocranium- which
forms bones of the base of the skull.

Membranous neurocranium:
• The membranous portion of the skull is derived from
neural crest cells and paraxial mesoderm.
• Mesenchyme from these two sources invests the brain
and undergoes membranous ossification. The result is
formation of number of flat, membranous bones that are
characterized by the presence of needle like bone
spicules. These spicules progressively radiate from
primary ossification centers towards the periphery.
• With further growth during fetal and postnatal life, the
membranous bones enlarge by opposition of new layers
on the outer surface and by simultaneous osteoclastic
resorption from the inside.

Cartilaginous neurocranium/ chondrocranium:
 The cartilaginous neurocranium/ chondrocranium of the skull initially
consists of a number of separate cartilages.
 Those that lie in front of the rostral limit of the notochord, which ends
at the level of the pitutiary gland in the center of the sella turcica, are
derived from neural crest cells. They form the prechondral
chondrocranium.
 Those that lie posterior to this limit arise from paraxial mesoderm
and form the chondral chondrocranium. The base of the skull is
formed when these cartilage fuse and ossify by endochondral
ossification.
 The base of the occiptal bone is formed by the parachordal cartilage
and the bodies of three occipital sclerotomes.
 Rostral to the occipital base plate are the hypophyseal cartilage and
trabeculae cranii.

OSTEOGENESIS
 Bone forms in two basic modes named after the site of
appearance- cartilage / membranous connective tissue.
 A) Endochondral bone formation:
 During endochondral bone formation, the original mesenchyme
tissue first becomes cartilage. Endochondral bone formation is a
morphogenetic adaptation providing continued production of bone
in special regions that involve relatively high levels of compression.
 Thus it is found in the bones associated with movable joints and
some parts of the basicarnium. Cartilage cells hypertrophy, their
matrix becomes calcified, the cells degenerate, and osteogenic
tissue invades cartilage and replaces it.

Osteogenesis
 Four fundamental ideas summarised the importance of the cartilage
bone interface seen in endochondral bone formation.
 I) Cartilage is rigid and firm, but not ordinarily calcified, thus providing
three basic growth functions.
 a) flexibility: yet support for appropriate structure (eg-nose)
 b) pressure tolerance : in specific sites where compression occurs ( eg-
articular cartilage and epiphyseal growth in long bones )
 c) A growth site: in conjunction with enlarging bones ( eg synchondroses
of the cranial base and the condylar cartilage )

Osteogenesis
 II) Cartilage grows both appositionally, by the activity of its
chondrogenic membrane, and interstitially, by cells divisions of
condrocytes and by addition to its intercellular matrix. ( whereas
interstitial growth of bone with its calcified matrix is of course,
impossible ).
 III) Bone, unlike cartilage, is tension adapted and cannot grow directly
in heavy pressure are because its growth is dependent upon its
vascular osteogenic covering membrane.
 IV) Growth of cartilages appear where linear growth is necessary
towards the direction of pressure, allowing the bone to lengthen
towards the force area .

B) Intramembranous bone formation:
 In intramembranous bone formation, the undifferentiated mesenchymal cells
of the membranous connective tissue change to osteoblasts and elaborate
osteoid matrix. The matrix or inter cellular substance becomes calcified and
bone results.
 Bone tissue laid down by the periosteum, endosteum, sutures, and the
periodontal membrane ( ligament ) are all intramembranous in formation.
Intramembranous ossification is the predominant mode of growth in the skull,
even in composite “ endochondral” elements, such as the sphenoid and
mandible, where endochondral and intramembraneeous growth occur in the
same bone. The basic modes of formation ( or resorption ) are similar,
regardless of the kind of membrane involved.
 Bone tissue sometimes is calcified as “periosteal” (or) “endosteal” according
to its site of formation. Periosteal bone always is of intramembranous origin,
but endosteal bone may be either intramembranous or endochondral in
origin, depending on the site and mode of formation.
Osteogenesis

 Intramembranous bone growth may be summarized by means of several
basic ideas:
 1) Intramembranous bone growth occurs in areas of tension. The membranes
( periosteum, sutures, periodontium ) have their own internal deposition of
remodelling processes.
 2) The membrane grows outward rather than just bulking off as bone is laid
down behind it. As it does so it undergoes extensive fibrous changes in
order to maintain continuity among the periosteum, muscle insertion, and the
bone itself. Therefore, there is constant deposition and resorption on the
bone surface as part of membranous remdoelling and relinking processes.
 3) The periodontal membrane converts the pressures exerted against the
teeth during occlusal functions into tension on the collagenous fibers
attaching the tooth to the alveolar bone. The position of teeth within the
alveolar process are altered during eruption, during mesial drifting, and as
they adapt to facial growth/ orthodontic forces. These changes are made
possible by constant remodelling and relinkage processes of the fibrous
attachments between the tooth and the bone.
Osteogenesis

PRENATAL GROWTH

Prenatal growth of cranial base:
• The bones of the skull are developed in the mesenchyme which is
derived from mesoderm. The mesenchymal cells have the ability to
form many different kind of cells that in turn give rise to various
tissues. Thus chondroblasts arising from mesenchymal cells form
cartilage, osteoblasts form bone so on and so forth.
• In the skull before osseous state is reached the cranium passes through
blastemal and cartilaginous stages like other parts of the skeleton.
• The blastmeal skull ( desmocranium mesenchymal primordium of
skull) appears at the end of first month of IUL as a condensation and
thicknening of the mesenchyme which surrounds developing brain.

• During 4th
week intrauterus mesenchyme condenses between
developing brain and foregut to form the basal portion of
ectomeningeal capsule and this condensation is evidence of skull
formation. However actual development of skull base occurs
later.
• Further the mesenchymal condensation extends forwards, dorsal
to pharynx, to reach the primodium of the hypophysis, thus
establishing the clinus of the cranial base of the dosum sellae of
feature sphenoid bone.
• Early in the second month it surrounds the developing stalk of
the hypophysis and extends toward the two halves of nasal cavity
where it forms the ethmoid bone and nasal septum.
• During 21-31 days period, the occipital mesenchyme concentrates
around notochord underlying the developing hind brain. From
this region the mesenchymal concentration extends cephalically
forming a floor for the developing brain.

 During fifth week- mesenchyme around the
developing hypophyseal stalk, which is forming
the rudiment of the post sphenoid part of the
sphenoid bone. Spreads out laterally to form the
future greater wing of this element. Smaller
processes neutral to this indicated the sites of the
lesser wings of the sphenoid, while other
condensation reach the sides of the nasal cavity
and also blend with each other, they also extend
towards and reach the base of the skull, which
will become part of the chondro-cranium.
 From 40th day intrauterine onward conversion of
mesenchyme into cartilage constitute the
beginning of the chondrocranium.

• From around the 40th
day onwards, this ectomeningeal
capsule is slowly converted into cartilage. This herads
the onset of cranial base formation the convertion of
mesenchymal cells into cartilage or chondrification
occurs in 4 regions.
Parachordal:-
The condrification centers forming around the cranial end
of the notochord are called parachordal cartilage.

Hypophyseal:
• Cranial to the termination of notochord, ( which is at the level of the
oro-pharyngeal membrane ) the hypophyseal pouch develops which
gives rise to the anterior lobe of the pituitary gland.
• On either side of the hypophyseal stem two hypophyseal / post
sphenoid cartilage develop. These cartilages fuse together and form
the posterior part of the body of sphenoid.
• Cranial to the pituitary gland, two presphnoid or trabecular
cartilages develop which fuse together and form the anterior part of
the body of sphenoid. Anteriorly, the pre-sphenoid cartilage forms a
vertical cartilaginous plate called mesethmoid cartilage which gives
rise to the perpendicular plate of ethmoid and cristagulli.
• Lateral to the pituitary gland chondrification centers are seen which
form the lesser wing ( orbito-sphenoid) and greater wing ( Ali-
sphenoid) of sphenoid.

Nasal:-
• Initially during development, a capsule is seen around the nasal sense
organ. This capsule chondrifies and forms the cartilages of the nostrils
which fuse with the cartilage of the cranial base.
Otic:-
• A capsule is seen around the vestibulo cochlear sense organ. This capsule
chondrifies and later ossifies to give rise to the mastoid and petrous
portion of the temporal bone. The otic cartilage also fuse with the
cartilages of the cranial base.
• The initially separate centers of cartilage formation in the cranial base,
fuse together into a single irregular and greatly perforated cranial base.
The early establishment of the various nerves, blood vessels etc., form and
to the brain results in numerous perforations/ foramina in the developing
cranial base. The ossifying chondro-cranium(cranial base) meets the
ossifying desmocranium ( cranial vault ) to form the neurocranium.

 OCCIPITAL BONE
The occipital bone shows both endochondral and intramembranous
ossification.Seven ossification centers are seen, two intramembranous and five
endochondral.
 i) The supranuchal squamous part ossifies intramembranously from one pair of
ossification centers which appear in the eighth week of intrauterine life.
 ii) The infranuchal squamous part ossifies endochondrally from two centers
which appear at the tenth week of intrauterine life.
 iii) The basilar part ossifies endochondrally from a single median ossification
center appearing in the eleventh week of intrauterine life. This gives rise to the
anterior portion of the occipital condyles and the anterior boundary of foramen
magnum.
 iv) A pair of endochondral ossification centers appear in the twelfth week
forming the lateral boundary of foramen magnum and the posterior portion of
occipital condyles.
CHONDRO – CRANIAL OSSIFICATION
The cranial base which is now in a cartilaginous form undergoes ossification.The
bones of the cranial base undergo both endochondral as well as intramembranous
ossification.

TEMPORAL BONE
 The temporal bone ossifies both endochondrally and
intramembranously from eleven centers – five intramembranous and
six endochondral.
 Squamous part of the temporal bone ossifies from a single
intramembranous center that appears in the 8th week of intrauterine
life.
 The Tympanic ring ossifies from 4 Intramembranous centers that
appear in the 12th week of intra uterine life.
 The petrous part of temporal bone ossifies from 4 endochondral
centers that appear in 5th month of intra uterine life.
 Styloid process ossifies from 2 endochondral centers.

Ethmoid bone
 This bone shows only endochondral
ossification. It ossifies from 3 centers.
 One center located centrally that forms the
median floor of the anterior cranial fossa.
 Two lateral centers in the nasal capsule

Sphenoid Bone :
Sl. No Region Types of ossification Ossification centre
1 Lesser wing Endochondrally Orbitosphenoid
cartilage
2 Part of greater wing Endochondrally A lisphenoid cartilage
3 Medial pterygoid plate Endochondrally Humular process from
secondary cartilage
4 Body of sphenoid
anterior part
Endochondrally Presphenoid cartilage
5 center ( 2 paired + 1
median)
5 Posterior part Endochondrally Pre and post sphenoid
This bone ossifies both intramembranously and endochondrally.
There are 15 ossification centers with only 2 intramembranous
ossification centers in 8th
week of intrauterine for small part of greater
Wing of Spenoid and lateral pterygoid plate.

Cranial base flexure:-
• During embryonic and early fetal period the cranial base becomes
flexed in the region between pituitary fossa and spheno-occipital
junction. So that the developing face becomes tucked under the
cranium.
• If a short piece of adhesive tape is affixed, to a rubber balloon and
the balloon is then inflated, it will expand in a curved manner. The
balloon bends because it enlarges around the non expanding
segment. The enormous human cerebrum similarly expands a much
lesser enlarging midneutral segment ( the medulla, pons,
hypothalamus, optic chiasma). This causes a bending of the whole
underside of the brain. The flexure of the cranial base results.

• The expansion of the frontal lobes displaces the frontal bone
upwards and outwards. This results in the distinctive, bulbous
upright forehead of the human face.
• The cranial base flexure alters the direction of the foramen
magnum from the horizontal to the vertical orientation and the
neurocranial capacity increases. These two factors are features of
an upright bipedal stature of man.
• The flexure in a 10 week fetus before ossification has an angle
of 65 degree between anterior and posterior parts of
chondrocranium but subsequently opens out to a less acute at
birth. www.indiandentalacademy.com

Uneven Nature Growth of Cranial Base
• The growth of the cranial base is highly uneven. This is attributed
to the uneven nature of growth seen in the different regions of the
brain. Thus the cranial base growth resembles the growth of the
ventral surface of the overylying brain.
• The anterior and posterior parts of the cranial base grow at
different rates. Between the 10th
and the 40th
weeks of intra-uterine
life, the anterior cranial base increases in length and width by 7
times while, during the same period the posterior cranial base
increases only five fold

POST NATAL GROWTH:
 Mechanism and sites:
 Growth of the cranial base post natally occurs by a complex interlay
between
 elongation at synchondroses,.
 sutural growth
 extensive cortical drift and remodeling
This provides:
 1. Differential growth enlargement between the cranial floor and the
clavaria.
 2) Expansion of confined contours in the various endocranial fossae.
 3) Maintenance of passages and housing for vessels and nerves and
such appendages as the hypophysis.

• The bony surface of the whole cranial floor is
predominantly resorptive in nature.
• This is in contrast to the endocranial surface of the
calvaria (skull roof), which is predominantly depository.
• The reason for this major difference is that:
the inside (meningeal surface) of the
skull roof is not compartmentalized into a series of
confined pockets.
• The cranial floor, in contrast, has the endocranial fossae
and other depressions, such as sella turcica and the
olifactory fossae.

• As the brain expands, the separate bones of the calvaria are
correspondingly displaced in outward direction .
• The primary displacement (due to brain expansion) causes tension
in the sutural membranes; respond immediately by depositing new
bone on the sutural edges, each separate bone thereby enlarges in
circumference. At the same time, the whole bone receives a small
amount of new deposition on the flat surface of both the ectocranial
and endocranial sides.
• The endosteal surface of the inner and outer cortical tables is
resorptive. This increases the thickness of the bone and expands the
medullary space between the inner and outer tables.
• The arch of curvature of the whole bone decreases and the bones
becomes flatter.
• The outward movement of each bone is caused by the expansion of
the brain. As this happens each bone also simultaneously changes
curvature by the remodeling process.

 As long as the frontal lobe of the crebrum grows, the inner table of
the forehead correspondingly drift anteriorly, when frontal lobe
enlargement slows and largely ceases some times before about the
sixth / seventh year, the growth of the inner table stops with it. The
outertable, however, continues to drift anteriorly. This progressively
separates the two tables and an enlarging frontal sinus results.

CRANIAL FLOOR:
 The cranial floor requires an entirely different mode of
growth because of its topograhic complexity and the tight
curvature of its fossae.
 The endocranial side (in contact with the dura that
functions as a periosteum) is characteristically resorptive
in most areas.
 The reason for this is that the suture cannot provide for
the entire process of growth enlargement.
 The system of sutures inherited from our mammalian
ancestors cannot fully accommodate the markedly
deepened endocranial fossae of the human basicarnium,
and additional widespread remodeling of the cranial floor
is required.

 For eg., in diagram (a) sutures are located at 1 and 2 and
these produce growth in the direction of the arrows. However,
the two sutures present cannot produce the growth for the
other directions also needed to accommodate brain
expansion, as shown in diagram (b).

 Growth is accomplished by direct cortical drift, involving deposition on the
outside with resorption from the inside; it is the key remodling process that
provides for the direct enlargement of the various endocranial fossae in
conjunction with sutural growth.
 The various endocranial compartments are separated from one another by
elevated bony partitions. The middle and posterior cranial fossae are divided by
the petrous elevation.
 The olifactory fossae are separated by the cristal gelli; the right and left middle
fossae are separated by the longitudinal midline sphenoidal elevation just below
the sella turcica and right and left anterior and posterior cranial fossae are
divided by a longitudinal midline bony ridge.
 All these elevated partitions are depository in nature
 the reason simply, is that as the fossae expand outward by resorption, the
partitions between them must enlarge inward, in proportion, by deposition.

 The anterior cranial fossa enlarges in
conjunction with the expansion of the frontal
lobes. Wherever sutures are present, they
contribute to the increase in the circumference
of the bones involved.
 Thus, the sphenofrontal, frontotemporal,
sphenoethmoidal, frontoethmoidal, and
frontozygomatic sutures participate in a
traction adapted bone growth response to
brain and other soft tissue enlargement. The
bones all become displaced as a
consequence. This is a primary type of
displacement, because the enlargement of
each bone is involved/
 Together with this the component bone i.e.,
sphenoid, ethmoid, temporal also grow
outward by ectocranial deposition and
endocranial resorption, the composite of all
these processes produce the growth changeswww.indiandentalacademy.com

 The cranial bones increase
in size by sutural bone
growth as the forehead
becomes displaced
anteriorly.
 The nasomaxillary complex
is carried anteriorly as well.
Note that the maxillary
tuberosity now lies ahead of
the vertical reference line.
 The tuberosity, however,
simultaneously grows
posteriorly by an equivalent
amount.
 The floor of the anterior
cranial fossa and the bony
maxillary arch are counter
parts.

As long as the frontal lobe of the crebrum grows, the inner table of the forehead
correspondingly drift anteriorly, when frontal lobe enlargement slows and
largely ceases some times before about the sixth / seventh year, the growth of the
inner table stops with it. The outertable, however, continues to drift anteriorly.
This progressively separates the two tables and an enlarging frontal sinus results.

Sella turcica:-
 The activity of bone lining the sella turcica, however, is
quite variable and can be either depository/ resorptive in
different areas. Several reasons contribute to this,
 1) varying degree of cranial base flexure and the
 2) variable amounts of downward and forward
displacement of the midventral segments of the whole
basicranium by the different shapes and proportionate
size of the cerebral lobes.
 The sella turcica, must remain in contact with the pituitary
gland and also adjust to the variable size of the growing
gland itself. www.indiandentalacademy.com

 If the pituitary fossa is carried downward by whole basicranial
displacement disproportionately to the pituitary gland itself, the floor of the
sella will correspondingly rise by surface deposition to maintain contact
with the pituitary, or the floor may be partly/ entirely resorptive in other
individuals to adjust the balance between cranial base displacement and
hypophyseal contact.
 A common combination is a resorptive posterior lining wall of the
hypophyseal fossa and depository surface on the spinoidal part of the
clivus. This causes a backward flare of the dorsum sellae to accommodate
a pituitary gland that is being displaced to a lesser extent than the
spinoidal body below it.
 The anterior wall of sella turcica is stable by 5-6 years, its posterior wall
and its floor till about 17 years and also because of variable remodelling.
Sella cannot be regarded as a stable point till after puberty.

 The midventral segment of the cranial floor grows much more slowly than the
floor of the laterally located fossae. This accommodates the slower growth of
the medulla, pons, hypothalamus, optic chiasma and soforth; in contrast to
the massive rapid expansion of the hemispheres.
 A markedly decreasing gradient of sutural growth occurs as the midline is
approached, but direct remodeling growth occurs to provide for the varying
extent of expansion required among the different midline parts themselves
and between the midline parts and much faster growing lateral regions.

• Unlike the skull roof, the floor of the cranium provides for the passage of
cranial nerves and the major blood vessel, because the expansion of the
hemispheres would cause marked displacement movement of the bones in the
cranial floor if only a sutural growth mechanism were operative, the process of
remodeling growth in the cranial base provides for the stability of these nerves
and vascular passage ways.
• That is, they do not become disproportionately separated because of the
massive expansion of the hemispheres of the brain, as would happen if the
bones enlarged primarily at the sutures.
• The foramen enclosing each nerve blood vessel also undergoes its own drift
process to constantly maintain proper position.

Synchondrosis
 The cranial base grows by primarily by cartilage growth in the
spenoethmoidal, intersphenoidal, speno-occipital and interoccipital
synchondroses, mostly following the neural growth curve, but
partially the general growth curve.
 Activity at the interspenoidal synchondrosis disappears at birth
 The intra occipital synchondrosis closes in the third to the fifth year
of life.
 The speno-occipital synchondrosis is a major contributor;
endochondral ossification does not stop here unlike the twentieth
year of life.

 The middle of the cranial base is characterized by the presence of synchondroses.
They are ‘left over’ from the primary cartilages of the early cartilagenous cranial base
after the endochondral ossification centers appear during fetal development.
 A number of syncondroses are operative during the fetal and early postnatal periods.
During the childhood period of development, however, it is the spheno-occipital
synchondrosis that is the principal “growth cartilage” of the cranial base.
 Like all “growth cartilages” associated directly with bone development, the spheno-
occipital synchondrosis provides a pressure-adapted bone growth mechanism. This
is in contrast to the tension-adapted sutural growth process.
 Compression is involved in the cranial base, unlike the clavaria, presumably
because it supports the weight of the brain and the face, which bear down on the
fulcrum like synchondrosis in the midline part of the cranial floor.

 The spheno-occipital synchondrosis is retained through the childhood growth period
as long as the brain and cranial base continue to grow and expand. It ceases to be
active at about 12 to 15 years of age, and the sphenoid and occipital segments then
become fused in this midline area before about 20 years of age.
 The presence of the spheno-occipital synchondrosis provides for the elongation of
the middle portion of the cranial base by its pressure adapted mechanism of
endochondral ossification.
 The floor of the cranium also has sutures in the lateral areas but
 (1) the force of compression is accommodated by the synchondrosis, not the suture
and
 (2) the expansion of the laterally located hemispheres produce tension in these
lateral sutural areas, unlike the slower growing midline part of the cranial base not
related directly to the hemispheres.
 Sutures are connective tissue membranes that provide tension adapted sites of
intramembranous bone growth.

 Historically, the synchondrosis has been regarded as the growth “center” and
pacemaker of the cranial base. This overly simplistic notion, however, as with the
mandibular condyle, is a conceptual anuchronism.
 The development of basicranium is quite multifactorial and not merely the product
of localized, midline cartilages that do not relate to the many regional growth
circumstances throughout the basicranium as a whole. Only a very small
percentage of the actual bone of the cranial floor is formed in conjunction with the
synchondrosis.
 The structure of the synchondrosis is similar to basic plan for all primary types of
growth cartilages, in contrast to the secondary variety, which is basically different.
 Like the epiphyseal plate of long bones, the synchondrosis has a series of “zones”
including the familiar reserve, cell division, hypertrophy and calcified zones. Like
the epiphyseal plate but unlike the condylar cartilage, the condroblasts in the cell
division zone are aligned in distinctive columns that point towards the line of
growth.
 Unlike the epiphyseal plate, the synchondrosis has two major directions of liner
growth. Structurally, the synchondrosis is essentially two epiphyseal plate
positioned back to back and separated by a common zone of reserve cartilage.

 Subsequent research by Koski, transplanting pieces of cranial base from different
sutures, showed little growth of the transplant. Since subcutaneously transplanted
synchondroes showed little/ no growth, a repeat experiment was done on 166
specimens, this time transplanting into brain issue most of the transplants did not
increase in size. However, summarizing the work that Koski and Ronning have
done together, “cartilaginous epiphyses transplanted into brain tissue
differentiated into normal, growing long bones, whereas condylar cartilages of the
mandible similarly transplanted rapidly lose their structure and evidently do not
continue promote bone growth.
 Cranial base synchondroses thus seem to represent an intermediate form of so-
called growth cartilage between those two ( epiphysis of long bone and condylar
cartilage )in that they appear to possess on inherent bone growth promoting
potential which is greater than that of condylar cartilage but not as great as that of
epiphyseal cartilages of long bones. The functional matrix theory is thus strongly
supported.

 According to some authors, the sphenomesethmoidal synchondrosis and the
cartilage between the mesethmoidal and frontal bones are equally important. In
addition, there is the growth of the frontal bone itself, increasing in thickness
through penumatization and creation of the frontal sinus. All except the frontal bone
portion develop in the chondrocranium. Just when the sphenoethmoidal
synchondrosis close is not definitely known. Claims range from 5-25 years of age. It
is likely, however, that its major contribution has been made by the time the first
permanent molar erupts. Recent research indicates that growth/ lack of growth at
the spheno-ethmoidal synchondrosis may have important ramification in cleft palate
rehabilitation.

 Endochondral bone growth by the spheno-occipital synchondrosis relates to primary
displacement of the bones involved. Thus the sphenoid and the occipital bones
move apart by the primary displacement process. At the same time, new
endochondral bone is laid down in the medullary regions of each bone, and cortical
bone tissue is formed by the periosteum and / or the endosteum around this core of
endochondral bone tissue. Each whole bone ( the sphenoid and the occipital)
thereby becomes lengthened.
 Both bones also increase in girth by periosteal and endosteal activity.
 The interior of the sphenoid bone becomes hollowed to form the sizable sphenoidal
sinus. This sinus is just behind and in direct line with the bony nasal septum of the
nasomaxillary complex.
 As the midface is displaced forward and downward, the sphenoid retains contact
with it, and the sphenoidal sinus is drawn out by the enlargement of this part of the
sphenoidal body.
 Shenoidal sinus expansion does not “push” the maxilla, however. The sinus is
secondarily formed as the body of the sphenoid bone expands keeping constant
relationship with the midface.

 As the horizontal enlargement of the middle cranial fossa advances the nato-maxillary
complex by forward displacement, the horizontal span of the pharynx correspondingly
increases.
 The skeletal dimension of the pharynx is established by the size of the middle cranial
fossa. The ramus of the mandible bridges the pharynx, and as this space enlarges,
the ramus increases to an equivalent extent to maintain the same facial form.
 The effective horizontal dimensions of the ramus and the middle cranial fossa ( not
their respective oblique dimensions ) and direct counterparts of each other.
 One structural function of the ramus, in spanning the middle cranial fossa, is to
provide a growth capacity for whatever adaptation is required to place the corpus /
body in continuously functional position relative to the maxillary arch.
 If this is successful, a normal / class I occlusion is achieved in a given individual. If
less than adequate, the greater/ lesser degree of failure of its adaptive or
compensatory function contribute in part, to the basis for a malocclusion.
 As the ramus becomes relocated posteriorly by its own growth movement. The
purpose is to horizontally lengthen the corpus / body and to displace it anteriorly.
While this occurring, the middle cranial fossa is also enlarging, however, so that now
the ramus correspondingly increases in breadth to equal it, this is done by the same
process that carried out stages 3 and 4 except that the amount of posterior ramus
growth now exceeds the aount of anterior resorption. The horizontal breadth (PA) of
the ramus is thereby increased.

CONCLUSION:
Yes, cranial base is the template for facial growth. Since
not visible to orthodontist as facial profile and occlusion.
The basic knowledge of growth of cranial base is
imperative.
The extent of cranial base can be known and evaluated
by certain cephalometric analysis such as Schwarz linear
analyses etc.
Also the effect of different treatment modalities on the
cranial base need an attention.

Bibliography
• Handbook of facial growth. IInd Edition, Donald H.Enlow
• Contemporary Orthodontics. William Proffit.
• Current principles and techniques. T.M Garber.
• Langmans Medical Embryology, Ninth Edition. T.W. Sunder
• Handbook of Orthodontics. Robert E. Moyers.
• Practice of Orthodontics J.A. Salzman
• Text book of Orthodontics. Bishara. N.

Growth & development of cranial basae & vault

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Growth & development of cranial basae & vault