SYNCHONDROSIS IN ORTHODONTICS AND ITS SIGNIFICANCE IN GROWTH

SYNCHONDROSIS
1
-Aleena Iqbal; PG 1st
year; Batch
2023

CONTENTS:
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o INTRODUCTION
o HISTOLOGICAL STRUCTURE AND GROWTH MECHANISM
o EMBRYOLOGICAL DEVELOPMENT
o DIFFERENTIAL GROWTH IN SYNCHONDROSIS
o SYNCHONDROSIS AS GROWTH CENTERS
o ROLE OF SYNCHONDROSIS IN GROWTH
o ABNORMALITIES IN GROWTH
o CONCLUSION
o REFERENCES

INTRODUCTION:
Synchondrosis is defined as the development of a union between two
bones by the formation of either hyaline cartilage or fibro-cartilage.
3
• Temporary and exists during the growing phase
• Intervening cartilage becomes progressively thinner during skeletal
maturation
• Ultimately becomes obliterated and converted into bone before
adult life.
• Important growth centers of the craniofacial skeleton
• Last sites in the cranium to terminate growth
Essentials Of Facial Growth -D.H.ENLOW

INTRODUCTION:
4
In the cranial base, four types of
synchondroses are seen:
• Intersphenoidal
• Intraoccipital
• Sphenoethmoidal
• Sphenoccipital or Basioccipital

INTRODUCTION:
5

INTRODUCTION:
6
OSSIFICATION OF SYNCHONDROSIS:
Latham RA, 1972
• Intersphenoidal- At the time of
birth
• Intraoccipital- 3-5 years of age
• Sphenoethmoidal- 5-20 years of
age
• Sphenoccipital- 12-16 years for
females and 13-17 years in males
Cendekiawan T. et all Relationships Between Cranial Base Synchondroses and Craniofacial Development: A Review. The Open Anatomy

HISTOLOGICAL STRUCTURES OF
SYNCHONDROSIS:
7
• Morphologically, a synchondrosis is similar to the long bone
growth plate
• Except that growth at the synchondrosis is not unipolar but
bipolar
• Synchondrosis can be regarded as two growth plates positioned
back to back
• So that they share a common zone of actively proliferating
chondroblasts, or the “rest zone”

SYNCHONDROSIS:
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(A) Zone of vascular erosion and
invasion.
(B) Zone of matrix calcification.
(C) Zone of matrix production or
matrixogenic zone.
(D) Zone of cellular proliferation.
(E) Central zone or resting zone.
The different zones of the synchondrosis mirror each other
such that there is cartilage in the center and bone at each
end.

SYNCHONDROSIS:
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CENTRAL OR RESTING ZONE
• The central, or resting, zone is synonymous to the
reserve zone of the growth plate
• Chondrocyte precursors- direct the formation and
organization of a synchondrosis
• Much denser and smaller cells, not arranged in
columns
• Surrounded by a thicker layer of cartilage matrix

SYNCHONDROSIS:
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CENTRAL OR RESTING ZONE
Abad et all, 2002
• Resting zone cartilage makes important contributions to
endochondral bone formation, by providing stem-like cells to
produce proliferative chondrocytes
• Producing growth plate orienting factors (GPOF), which are
morphogens that control the alignment of the proliferative
clones into columns parallel to the long axis of the bone

SYNCHONDROSIS:
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ZONE OF CELLULAR
PROLIFERATION
• Region of active cell replication
• Chondrocytes are arranged in columns that are
parallel to the longitudinal axis of the bone- 10-20
columns
• Separated from each other by matrices containing
large amounts of collagen type II
• More the cells, greater the growth rate

SYNCHONDROSIS:
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ZONE OF CELLULAR
PROLIFERATION
• Multiple mitoses in the proximal portion of each column
• Because the two daughter cells line up along the long axis of the bone
when the chondrocytes divide- clones of chondrocytes are arranged in
columns parallel to this axis.
This spatial orientation directs growth in a specific direction and is thus
responsible for the elongate shape assumed by many endochondral bones

SYNCHONDROSIS:
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ZONE OF MATRIX
PRODUCTION
• The matrix is synthesized in the lower half of the
proliferating layer by an extensive network of
chondrocytes
• These chondrocytes have large amounts of rough
endoplasmic reticulum
• Chondrocytes mature and enlarge
• Increase in intracellular volume by 5 to 10 times
• Initiates ossification, which prepares the matrix for

SYNCHONDROSIS:
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ZONE OF MATRIX
CALCIFICATION
• Interface between cartilage and bone
• Contains dead chondrocytes
• Attracting vascular and bone-cell
invasion from the adjacent bone
• Responsible for bone elongation

EMBRYOLOGICAL DEVELOPMENT OF
SYNCHONDROSIS:
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Anterior cranial base is derived from neural crest mesoderm,
the posterior cranial base is developed from paraxial
mesoderm
CARTILAGINOUS
TEMPLATE
BON
E
Endochondral
ossification
Craniofacial Embryology - G.H.SPERBER

SYNCHONDROSIS:
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Pairs of templates from caudal to
rostral region:
1. Sclerotome cartilage
2. Parachordal cartilage
3. Hypophyseal
cartilage
4. Presphenoid cartilage
5. Orbitosphenoid
cartilage
6. Alisphenoid cartilage
7. Mesethmoid cartilage

SYNCHONDROSIS:
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Ossification from the posterior to the anterior and finally fuses into a
single, irregular and much-perforated base plate, known as the
chondrocranium.
• The chondrocranium then undergoes further progressive
ossification.
• Large areas of the cranial base remain cartilaginous throughout early
fetal life
• While many cartilages persist into the third trimester and postnatal

SYNCHONDROSIS:
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• The basioccipital ossification center was the first to form,
starting at 14 days post coitum (dpc),
• Followed by paired exoccipitals and basisphenoid
• The presumptive sphenooccipital synchondrosis was found
at 15 dpc
• The presphenoid formed between 16 and 17 dpc.
• On 18 dpc, the entire presumptive cranial base was
cartilaginous

SYNCHONDROSIS:
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• Throughout the first week of postnatal
development growth and ossification of the
cranial base accelerates
• By the fourth day after birth, the basioccipital-
basisphenoid and basisphenoid-presphenoid
synchondrosis had reached full development, in
analogy to mirror-image epiphyses.

DIFFERENTIAL GROWTH IN
SYNCHONDROSIS:
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Enlow, 1968
• Growth occur at different rates and to different extents on
opposite sides of the plate
• In the spheno-occipital synchondrosis, the greater part of this
lengthening occurs on the occipital side

DIFFERENTIAL GROWTH IN
SYNCHONDROSIS:
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Hoyte, 1968
Growth in the basiscranial synchondroses is symmetric
at each site but vary in patterned sequence between
sites
• Found a caudo-rostral gradient of growth rates in
the cranial base cartilages
• The highest rates in the basioccipital and lowest in
the rostral edge of the presphenoid

SYNCHONDROSIS AS GROWTH
CENTERS:
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Scott, 1967
Hypothesized that cranial synchondroses by virtue of their interstitial
growth, turgidity and resistance to deforming forces can separate
growing bones at sutures
Contemporary orthodontics- W.R.PROFFIT

SYNCHONDROSIS AS GROWTH
CENTERS:
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Servoss, 1973 and Kuroda et
all, 1981
• Experiments indicate that cranial base synchondroses are
endowed with an independent growth potential
• Comparable to epiphyseal plates with regards their tissue-
separating capacity
• Their growth continues for a longer duration than that of the
brain
• Which means the growth of the cranial base and the brain is not
closely interdependent

ROLE OF SYNCHONDROSIS IN
GROWTH
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• Integrated growth occurs through many mechanisms, the most
important of which are sutural expansion, synchondrosis
deposition, drift and flexion.
• As the basicranium grows, it elongates and flexes in the spheno-
ethmoid, mid-sphenoid, and spheno-occipital synchondrosis.

GROWTH
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as the brain expands
generates tension along the endocranial surface of the
neurocranial cavity
activating osteoblast deposition within the intra-sutural
periosteum throughout the upper portion of the vault
drifting in the lower portions of the vault and cranial base
endochondral growth within certain synchondroses

GROWTH
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THE INTERSPHENOIDAL
SYNCHONDROSIS:
• Between the presphenoid and
basisphenoid
• Fuses around the time of birth in
humans
THE INTRAOCCIPITAL
SYNCHONDROSIS:
• Fuses from 3-5 years of age
• Does not contribute to postnatal
growth
Coben SE. The spheno-occipital synchondrosis: the missing link between the profession’s concept of craniofacial growth and orthodontic treatment. American journal of orthodontics

GROWTH
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THE SPHENO-ETHMOIDALAL
SYNCHONDROSIS:
• Most active with respect to growth of the
cranial base through approximately 7 to 8
years of age in humans.
• After that the spheno-ethmoidal
synchondrosis loses its cartilage phenotype
• Once that transition occurs, growth of the
anterior cranial base is essentially complete

GROWTH
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THE SPHENO-OCCIPITAL
SYNCHONDROSIS:
• The spheno-occipital synchondrosis a
focus point for craniofacial growth
• The posterior cranial base becomes
longer primarily due to growth at the
spheno-occipital synchondrosis

GROWTH
29

GROWTH
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SYNCHONDROSIS:
• Smaller linear and angular dimensions have been shown in
class III patients
• Class II subjects demonstrate an increased cranial base angle
that leads to a more posterior position of the mandible
• The anterior cranial base and the middle cranial fossa have
also been reported to be longer in individuals with class II
malocclusion

GROWTH
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SYNCHONDROSIS:
• Synchondrosis growth translated the upper face and
maxillary complex almost completely forward, increasing the
depth of the upper face with little change in height.
• The mandible grows downward and forward away from the
cranial base, maintaining a constant sagittal relationship with
the foramen magnum
• The symphysis moved downward and only slightly forward

ABNORMALITIES IN GROWTH AND
DEVELOPMENT
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• Synchondrosis is an important link between the
development of the cranial vault and that of the facial
skeleton
• Premature growth arrest of the cranial base is widely
regarded as the primary abnormality in syndromic
forms of craniosynostosis
Various syndrome involved are:
Klinefelter syndrome, Williams syndrome,
Cretinism Syndrome, Turner Syndrome, and
Down’s syndrome

DEVELOPMENT
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KLINEFELTER SYNDROME & WILLIAM’S
SYNDROME
The major craniofacial changes are located in the
cranial base
• Skeletal disproportion
• Mandibular prognathism
• Upward slant of the palpebral fissure
• Depressed nasal bridge
• Cleft Palate

DEVELOPMENT
34
DOWN SYNDROME & TURNER
SYNDROME
The craniofacial structure is characterized by a short
retrognathic face owing to reduced cranial base length
and increased angulations
• Brachycephalic skull
• Open metopic suture
• Hypoplastic maxilla
• Flat nasal bridge, orbital ridges
• Delayed eruption of teeth

CONCLUSION:
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• Cranial base synchondroses, with their unique bipolar growth, are a
fundamental part of craniofacial development.
• They are the Important growth centers of the craniofacial skeleton
and the last sites in the cranium to terminate growth.
• Growth of the spheno-occipital synchondrosis, like a phantom,
influences all growing faces and is a factor in the treatment of all
children.
• The interrelation of craniofacial growth and orthodontic treatment is
equally important.
• Abnormalities in their development have serious consequences

REFERENCES:
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• Craniofacial Embryology - G.H.SPERBER
• Essentials Of Facial Growth -D.H.ENLOW
• Contemporary orthodontics- W.R.PROFFIT
• Orthodontics principles and practice -T.M. GRABER
• Coben SE. The spheno-occipital synchondrosis: the missing link
between the profession’s concept of craniofacial growth and
orthodontic treatment. American journal of orthodontics and
dentofacial orthopedics. 1998 Dec 1;114(6):709-12.
• Cendekiawan T. et all Relationships Between Cranial Base
Synchondroses and Craniofacial Development: A Review. The Open

SYNCHONDROSIS IN ORTHODONTICS AND ITS SIGNIFICANCE IN GROWTH

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