The document presents the 'Growth Relativity Hypothesis' by Dr. Vipul Gupta, which explores theories of condylar growth, including the Functional Matrix Hypothesis and its constraints. It posits that growth is influenced by the relative positioning of the condyles, the mechanical properties of surrounding tissues, and functional appliances. The hypothesis concludes that condylar growth can be modified through external forces applied during orthodontic treatment, with implications for clinical practice and long-term outcomes.

1. GROWTH RELATIVITY
HYPOTHESIS
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Presented by- Dr. Vipul Gupta
(MDS 1st
year)

2. CONTENTS
• History
• Functional matrix hypothesis
• Constraints of functional matrix hypothesis
• Functional matrix hypothesis revisited
• Growth relativity hypothesis
• Introduction
• Growth stimulus
• Conclusion
• Clinical implication
• References
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3. HISTORY
• Over the years, several theories have emerged attempting to shed light on
condylar growth.
• One of the earliest theories, the genetic theory, suggests the condyle is
under strong genetic control like an epiphysis that causes the entire
mandible to grow downward and forward.
• The theory does indirectly question the effectiveness of orthopedic
appliances in condylar growth as proposed by Brodie
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4. • Several long-term investigations actually showed clinically insignificant
condylar growth modification after continuous mandibular advancement
with a reasonable retention period in human beings although the initial
treatment results appeared encouraging.
• This leads to the conclusion that the general growth of the condyle appears
relatively unalterable in long-term studies.
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5. • A second hypothesis based on the earliest available acute and blind EMG
monitoring technique, suggests that hyperactivity of the lateral pterygoid
muscles (LPM) promotes condylar growth.
• Rees reported that other muscles and tendons, including those of the deep
masseter and temporalis, also attach to the articular disk region.
• Attachments of the LPM to the condylar head or articular disk may be
expected to cause condylar growth, but anatomic research has not found
evidence that significant attachments actually exist
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6. • LPM tendon is observed attaching, however, to the anterior border of the fibrous
capsule that in turn attaches to the fibrocartilage of the condylar head and neck
anteriorly.
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7. • By using LPM myectomy in rats, which may have disrupted condylar
blood supply, Whetten and Johnston found little evidence that LPM
traction had any pronounced effect on condylar growth
• More recently, permanently implanted longitudinal muscle monitoring
techniques have found that the condylar growth is actually related to
decreased postural and functional LPM activity.
• This notion was also supported in human studies.
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8. FUNCTIONAL MATRIX
HYPOTHESIS
• Melvin Moss introduced the functional matrix hypothesis in 1962
• While granting the innate growth potential of cartilages of the long bones, his theory holds
that neither the cartilage of the mandibular condyle nor the cartilaginous nasal septum is a
determinant of jaw growth.
• Instead, he theorized that growth of the face occurs as a response to functional needs and
neurotrophic influences and is mediated by the soft tissue in which the jaws are embedded.
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9. • Functional Matrix Hypothesis is stated as:
The origin, form, position, growth and maintenance of all skeletal tissues and organs
are always secondary, compensatory and necessary responses to chronologically and
morphologically prior events or process that occur in specifically related non- skeletal
tissues, organs or functional spaces.
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10. FUNCTIONAL CRANIAL
COMPONENT
• Operationally, the head is a region within which certain functions occur. Every
function is completely carried out by a functional cranial component.
• Each such component, in turn, is composed of two parts:
Functional matrix
Tissues And spaces that completely
performs the function
Skeletal cranial unit
A skeletal unit whose biomechanical
role it is to protect, and/or support
its specific functional matrix

11. FUNCTIONAL UNIT
• The tissues, organs, spaces, and skeletal parts necessary to carry out a given
function were termed collectively, a ‘functional cranial component’. On the basis of
their relation to transformative and translative growth, the soft tissues of a functional
component were classified as either ‘periosteal’or ‘capsular’ functional matrices.
• Most orthodontic therapy is based firmly on the fact that when this functional matrix
grows or is moved, the related skeletal unit (the alveolar bone) responds
appropriately to this morphogenetically primary demand.
• However , the term functional matrix is more inclusive still.
• There exists a further group of matrices among which the functioning spaces of the
oronasopharyngeal cavities figure importantly.

12. SKELETAL UNIT
• Skeletal units may be composed variably of bone, cartilage, or tendinous
tissues.
• When a “bone” consists of a number of skeletal units, it’s called the micro-
skeletal units; that is, both the maxilla and the mandible are formed of a
number of such contiguous microskeletal units.
• When adjoining portions of a number of neighboring “bones” are united to
function as a single cranial component, we term this a macroskeletal unit;
e.g : the endocranial surface of the calvaria

13. CONSTRAINTS OF FUNCTIONAL MATRIX
HYPOTHESIS
• FMH provided only qualitative narrative descriptions of the biologic dynamics
of cephalic growth, at the gross anatomic level, and it had two explanatory
constraints:
a) Methodologic
b) Hierarchical
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14. METHODOLOGIC CONSTRAINT
• Macroscopic measurements, which use the techniques of point mechanics
and arbitrary reference frames, was removed by the continuum mechanics
techniques of the finite element method (FEM) and of the related macro
and boundary element methods
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15. HIERARCHICAL CONSTRAINT
• Second constraint of FMH doesn't explain how the extrinsic, epigenetic
functional matrix stimuli are transduced into regulatory signals at the
cellular, multicellular or molecular levels.
• FMH versions were suspended or sandwiched as it were between these
two hierarchical levels
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16. FUNCTIONAL MATRIX HYPOTHESIS
REVISTED
• REVISITED- 1997 by Melvin L. Moss
FMHR 1- The role of mechanotransduction.
FMHR 2- The role of an osseous connected cellular network.
FMHR 3- The genomic thesis.
FMHR 4- The epigenetic antithesis and the resolving synthesis
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The periodic incorporation of advances in the biomedical, bioengineering, and
computer sciences allows the creation of increasingly more comprehensive revisions
of the functional matrix hypothesis
The FMH revisited Includes two new topics,
• The mechanisms of cellular mechanotransduction.
• Biologic network theory.

18. WHAT SPECIFICALLY AFFECTS THE
GROWTH AT THE CONDYLAR HEAD?
• Functional matrix theory, postulates the principal control of bone growth is not
the bone itself, but rather the growth of soft tissues directly associated with it.
• Although this was supported in part by investigations testing the different growth
and developmental responses between the condyle and epiphysis, there has been
no explanation as to exactly how condylar growth would be stimulated.
• Thus, this theory’s validity has been questioned. One of the reasons was that
there was little explanation of the specific mechanism by which the condyle was
stimulated to grow.
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19. • Endow and Hans presented an excellent overall perspective suggesting that
mandibular growth is a composite of regional forces and functional agents
of growth control that interact in response to specific extra-condylar
activating signals.
• These extrinsic signals are the foundation of the growth relativity
hypothesis.
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20. GROWTH RELATIVITY HYPOTHESIS
John C Voudouris 2000
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21. INTRODUCTION
• Growth relativity refers to growth that is relative to the displaced condyles from
actively relocating fossae
• When the condyle is displaced by functional appliances , the bone architecture is
influenced by the neuromusculature and the contiguous , non-muscular, viscoelastic
tissues anchored to the glenoid fossa and the altered dynamics of the fluids enveloping
bone.
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THE THREE STIMULUS FOR GROWTH
Displacement of condyle
Nonmuscular viscoelastic tissue stretch
Force transduction beneath the
fibrocartilage of the glenoid fossa and
condyle

23. GROWTH STIMULUS
• Modification first occurs as a result of the action of anterior orthopedic
displacement.
• Second, the condyle is affected by the posterior viscoelastic tissues anchored
between the glenoid fossa and the condyle, inserting directly into the condylar
fibrocartilage.
• Finally, it is hypothesized that displacement and viscoelasticity further stimulate
(or turn on the light switch for) normal condylar growth by the transduction of
forces over the fibrocartilage cap of the condylar head
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Mandibular
Advancement
(Displacement
)
• Synovial Fluids Dynamics
• Engorged blood vessels
Stretch Of Non–Muscular
Viscoelastic Tissue
• Transduction
New Bone
Formation
• Influx Of Nutrients

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When the growing condyle is continuously advanced, it lights up like a light bulb
on a dimmer switch. When the condyle is released from the anterior
displacement, the reactivated muscle activity dims the light bulb and returns it
close to normal growth activity.

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29. CLINICAL IMPLICATION
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• The condyles and fossae in individuals with average FMA grow generally in a
posterior and inferior direction based on the cranial base superimposition.
• That means the posteriorly directed forces of the viscoelastic tissues may affect
the advanced condyle and fossa at a time when the glenoid fossa should actually
be moving naturally in a posteroinferior direction.
• However, the fossa is reported to grow in the reverse direction, relocating
anteroinferiorly to meet active condylar modification and to restore normal
function during orthopedic treatment.

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• Modification of the GF can be clinically significant whenever the 2 structures,
the condyle and the fossa, are separated.
• In young growing subjects, reciprocal forces of the viscoelastic tissue between
the fossa and the condyle can change C-GF growth directions to our advantage
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31. CONCLUSION
• The condyle appears to act like a light bulb on a dimmer switch. It lights up during
advancement, dimming back down to near normal levels in retention.
• Its growth potential diminishes with age, whereas the glenoid fossa remodeling
“lighting” potential lasts long into adulthood
• Several investigations of relapse have lead to the conventional wisdom that C-GF growth
modification cannot be maintained.
• This does not prove, however, that growth of the condyle is strongly predetermined by
genetic factors, like an epiphyseal growth center.
• The condyle can restore its relational position within individual limits.
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32. REFERENCES
• CONTEMPORARY ORTHODONTICS – WILLIAM R. PROFFIT
• The primary role of functional matrices in facial growth [Am. J. Orthodontics June
1969 vol 55 no 6]
• Improved clinical use of Twin-block and Herbst as a result of radiating viscoelastic
tissue forces on the condyle and fossa in treatment and long-term retention: growth
relativity. American Journal of Orthodontics and Dentofacial Orthopedics. 2000 Mar
1;117(3):247-66.
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33. THANKYOU
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