Growth&dev ii /certified fixed orthodontic courses by Indian dental academy

Growth & DevelopmentGrowth & Development
Part IIPart II
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INDIAN DENTAL ACADEMY
Leader in continuing dental education

Hypothesis of craniofacial
growth
• Genetic theory
• Sicher’s suturalHypothesis
• Scott’s cartilagenous hypothesis
• Moss’ Hypothesis
• Petrovic’s Hypothesis
• Van limborgh Hypothesis

Genetic theory
• What we sometimes assume to be genetic
may be acquired and superimposed on a
genetic foundation comman to parents and
progeny.

• There is evidence to support polygenic
inheritance greatly limiting our ability to
explain facial dimension from study of
parents.

• The old argument about heredity versus
environment has changed from the question
of which is more important to how,and in
what we way does environment alter the
original form laid down by heredity.

• Even if the size of facial bones were
inherited in a medelian fashion,that
inherited pattern is altered by environmental
influences,some epigeniticepigenitic and some
general to such an extent that in the patient
the underlying genetic features cannot be
easily detected.

Sicher’s Hypothesis
(Sutural dominance theory)
• Sicher deduced from the many studies using
vital dyes, that the sutures were causing
most of the growth, he said infact “ …. The
primary event in the sutural growth is
proliferation of the connective tissue
between the two bones.
• If the connective tissue proliferates it
creates the space for the appositional
growth at the borders of the two bones.www.indiandentalacademy.com

• Replacement of the connective tissue was
necessary for functional maintenance of the
bones.
• He said sutures of the nasomaxiallary and
vault produced forces which separated the
bones ,just as the synchondrosis expanded
the cranial base and the epiphyseal plates
lengthened long bones.

Disadvantages
• Primarily because translatory growth of the
bones continue normally either in the
absence of sutures or through extirpation in
experimental animals
• In untreated cleft palates though suture is
not present growth still takes place.

Scott’s Hypothesis
(Cartilagenous theory)
• Scott noting the prenatal importance of
cartilagenous portions of the head ,nasal
capsule ,mandible and cranial base feeling
that this development is under the intrinsic
genetic control
• He specially emphasized how the cartilage
of the nasal septum during its growth paced
the growth of the maxilla.

• Sutural growth ,Scott felt came in response
to the growth of the other structures
including cartilagenous elements,brain, the
eyes, and so forth..

Cartilagenous growth

Moss hypothesis
• Moss feels that the bone and cartilage lack
growth determination and grow in response
to intrinsic growth of associated
tissues,noting that the genetic coding of
craniofacial skeletal growth is outside the
bony skeleton.

• He terms the associated tissues,
“Functional matrices” ,Each component of
a functional matrix performs a necessary
service- such as respiration, mastigation,
speech -while the skeletal tissues support
and protect the associated functional
matrices.

• Moss divides the skull into series of discrete
functional components each comprised of a
functional matrix and an associated skeletal
unit,designing the functional matrices as a
either periosteal or capsular.

• He stress the dominance of non osseous
structures of the craniofacial complex over
the bony parts. Moss claims that the growth
of the skeletal components whether
endochondral or intramembranous in origin
is largely dependent on the growth of
functional matrices.

Functional cranial comp.Functional cranial comp.
Functional matricesSkeletal unit
Micro sk.unit Macro sk.unit
Periosteal M Capsular M

• Each functional cranial component has a
skeletal and functional matrices.
• Skeletal unit’s biomechanical role is to
protect and or support its specific functional
matrix.Each skeletal unit is further divided
into microskeletal and macroskeletal.

• Functional matrix actually carries out the
function .Ex. Muscle,gland,teeth,etc.
Functional matricies are futher divided into
periosteal matrices and capsular matrices.

• Mandible is a Macro skeletal unit.Coronoid
process,condyle, angle of the mandible are
all micro skeletal units.
• Periosteal matrices includes muscles and
teeth ; act on the microskeletal units directly
and they bring about transformation or
active growth. Their net effects is to alter
the form (size and shape) of their respective
units. www.indiandentalacademy.com

• Capsular matrices act on the macroskeletal
unit I.e whole mandible and they bring
about translation or passive growth. They
do so by changing the volume of the
capsule within which the functional cranial
components Eg.oral cavity has inner oral
epithelium and skin outside.Mandible is
translated passively.

Anacephaly & Hydrocephaly

Petrovic’s hypothesis
( Servosystem)
• Using the language of cybernatics,cybernatics,
Petrovic, reasoned that it is the interaction
of a series of causal change and feed back
mechanisms which determines the growth
of the various crainofacial regions.
• According to the servosystem theory of
facial growth, control of primary cartilages
takes a cybernatic form of command
whereas in contrastwww.indiandentalacademy.com

the secondary cartilages is comprised not only
of direct effect of cell multiplication but
also of indirect effects
• In his experiments petrovic detected no
genetically predetermined final length for
the mandible.
• The direction & magnitude of condylar
growth variation are perceived as
quantitative responses to the lengthening of
the maxilla www.indiandentalacademy.com

Petrovic’s Hypothesis

Changing concepts of
craniofacial growth

Van limbrough Hypothesis
• Intrinsic Genetic factors- Genetics factors
inherent to the skull tissues
• Local epigenetic factors- Genetically
determined influences originating from
adjacent structures(brain, Eyes etc)
• General Epigenetic factors- Genetically
determined influences originating from
distant structures (Sex hormones)

• Local environmental factors- local non
genetic influences originating from the
external environment (local external
pressure, muscle forces)
• General environment factors -General non
genetic influences originating from external
environment (food, oxygen supply).

Van limbrogh Hypothesis

• Growth of the cranium occurs almost
entirely in reponse to growth of the brain
• Growth of the cranial base is primarily the
result of endohondral growth and bony
replacement at the synchondrosis and
perphaps influenced by the growth of the
brain

• Growth of the maxilla and its associated
structures occurs from a combination of
growth at sutures and direct remodelling of
the surfaces of the bone.
• Growth of the mandible occurs by both
endochondral proliferation at the condyle
and apposition and resorption of bone at
surfaces.

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Growth&dev ii /certified fixed orthodontic courses by Indian dental academy

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