This document presents the Growth Relativity Hypothesis proposed by John Voudouris in 2000. The hypothesis aims to explain the mechanism by which orthopedic appliances like Herbst and Twin-block can modify condylar-fossa growth. It suggests that displacement of the condyle from its fossa leads to changes in synovial fluid dynamics and stretching of viscoelastic tissues surrounding the joint, transmitting forces that stimulate new bone formation and growth modification. The hypothesis is based on three main foundations: displacement of the joint components, viscoelastic properties of soft tissues, and referred force transmission.
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3. Growth relativity hypothesis
Hypothesis presented for the
mechanism of condylar-fossa growth
modification with propulsive
mandibular appliances, such as the
Herbst & Twin-block
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5. Growth relativity hypothesis
Normal C-GF growth
Condylar remodelling
Pathosis at the condyle …. adaptation
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6. Growth relativity hypothesis
Condylar modification
Genetic theory– Genetic control
pre-natal
Effectiveness of orthopaedic appliances on
condylar growth ?- Brodie
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7. Growth relativity hypothesis
cybernetic theory – hyperactivity of LPM
anatomic research – no significant
attachment of LPM to the condyle
other muscle & tendon attachments – deep
masseter , temporalis - Rees
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14. Growth relativity hypothesis
Evidence of decreased muscle activity – use
of propulsive orthopaedic appliances
Cause for growth modulation?
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15. Growth relativity hypothesis
Mandibular growth is a composite
of regional forces & functional agents
of growth control that interact in
response to specific extracondylar
activating signals – Endow & Hans
Extrinsic signals – basis of “Growth
relativity theory”
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16. Growth relativity hypothesis
Growth relativity – growth that is relative
to the displaced condyles from actively
relocating glenoid fossa
Growth – long term retention results
short term treatment outcomes
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17. Extension of Wolff’s law
Growth relativity states that –
“with orthopaedically displaced condyle , the bone
architecture is influenced by the neuromusculature & the
contiguous, non – muscular , viscoelastic tissues anchored
to the glenoid fossa & the altered dynamics of the fluids
enveloping bone”
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18. Growth relativity hypothesis
3 main foundations
Displacement
Viscoelasticity
Referred force (transduction)
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19. Growth relativity hypothesis
Viscoelasticity
-applied to elastic tissues – muscles
In G R it applies to all non – calcified tissues
Elasticity of --retrodiskal tissues
--fibrous capsule
-- Synovial fluid flow
-- LPM perimycium
-- TMJ tendons & ligaments
-- Other soft tissues
-- Body fluids
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27. Light bulb analogy of condylar
growth & retention
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28. Discussion
Epiphysis
Vs
Tissue separating forces
condyle
No significant tissue separating
forces
Ephiphyseal cartilages - little
Significant short term adaptation
short term adaptation potential potential
No fibrocartilagenous cap
Presence of fibrocartilagenous
cap
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30. Epiphysis Vs condyle
Condyle dissimilar to epiphysis
…functionally
…anatomically
…immunologically
…chemically &
…ontogenetically
condyle does not act like an
epiphysis during orthopaedic
treatment
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31. Retention relapse
Deactivation of modification due to
compression of retrodiskal tissues
Hence long term adaptation is not
clinically significant
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34. conclusion
No measurable long-term benefits for the
mandible are derived from the first phase of
“functional” appliance therapy in a two phase
treatment.
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35. Future studies
Synovial fluid dynamics
Study conducted on primates – using
full occlusal coverage herbst block &
twin block appliances – hence
oppurtunity to use
cephalometric
histomorphometric
electromyographic methods
to investigate observed changes
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37. Bibliography
1. Contemporary orthodontics –
william R.Proffit ; 3rd edn
2. Orthodontics – Principles and practice
-T.M.Graber ; 3rd edn
3. The primary role of functional matrices in
facial growth – AJO-DO 1969 jun :(20-31)
4. The doctrine of functional matricesAJO-DO 1969 july; 56:no.1
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38. Bibliography
5.
Twenty years of functional cranial
analysis – AJO-DO 1972 may;61:no.5
6. The role of functional matrix in
mandibular growth – AJO-DO 1968
apr;38:no.2
7. The capsular matrix –AJO-DO 1969
nov;56:no.5
8. Genetics , epigenetics and causationAJO-DO 1981 oct;(366-75)
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39. Bibliography
The functional matrix hypothesis revisited
9. The role of mechanotransduction – AJO-DO
1997 July;112:8-11
10.The role of an osseous connected cellular
network- AJO-DO 1997 Aug;112;221-26
11.The genomic thesis – AJO –DO 1997
Sep;112:338-42
12.The epigenetic antithesis and the resolving
synthesis – AJO-DO 1997 oct;112:410-7
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40. Bibliography
13.Factors affecting the growth of the midface
–The functional matrix hypothesis :
reflections in a jaundiced eye – Lysle
E.Johnston Jr
GROWTH RELATIVITY HYPOTHESIS
14. Improved clinical use of Twin-block and
Herbst as a result of viscoelastic tissue
forces on the condyle and fossa in
treatment and long – term retention :
Growth relativity
AJO-DO 2000 Mar;117:247-66
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