Growth relativity hypothesis -John voudouris, 2000
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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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Growth relativity hypothesis Introduction Extensive use of orthopaedic appliances – Herbst, Twin-block & other auxiliaries “Why” & “How” www.indiandentalacademy.com
Growth relativity hypothesis Normal C-GF growth Condylar remodelling Pathosis at the condyle …. adaptation
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Growth relativity hypothesis Condylar modification Genetic theory– Genetic control
pre-natal
Effectiveness of orthopaedic appliances on condylar growth ?- Brodie www.indiandentalacademy.com
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 www.indiandentalacademy.com
Growth relativity hypothesis
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Growth relativity hypothesis
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Growth relativity hypothesis ď Ż LPM tendon – anterior border of fibrous capsule
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Growth relativity hypothesis Whetten & johnston
– LPM traction .. Little effect on condylar growth
Permanently implanted longitudinal muscle monitoring techniques – postural & functional LPM activity Studies on humans-Auf der maur -Pancherz -Anchus pancherz www.indiandentalacademy.com
Growth relativity hypothesis Functional matrix hypothesis – influence of non-skeletal tissues Exact method of condylar growth stimulation?
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Growth relativity hypothesis Increased vertical dimension & decreased LPM activity
Condylar pull “stress” – mandibular growth
Condylar compression - C-GF modification – Graber & Joho
vertical dimension - postural masticatory muscle activity – EMG records by Storey et al www.indiandentalacademy.com
Growth relativity hypothesis
Evidence of decreased muscle activity – use of propulsive orthopaedic appliances
Cause for growth modulation? www.indiandentalacademy.com
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” www.indiandentalacademy.com
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 www.indiandentalacademy.com
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” www.indiandentalacademy.com
Growth relativity hypothesis 3 main foundations Displacement Viscoelasticity Referred force (transduction) www.indiandentalacademy.com
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 www.indiandentalacademy.com
Growth relativity hypothesis
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Growth relativity hypothesis Mandibular advancement(displacement) Synovial fluid dynamics Influx of nutrients
Engorged blood vessels
Stretch of non – muscular viscoelastic tissues transduction
New bone formation www.indiandentalacademy.com
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Growth restriction-glenoid fossa GF - posteroinferior growth – Bjork, Popovich & Thompson posteriorly directed viscoelastictissues– effect condyleand GF Reversegrowth– relocation anteroinferiorly ClassII correction www.indiandentalacademy.com
Growth restriction-glenoid fossa
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Light bulb analogy of condylar growth & retention
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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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Epiphysis Vs condyle
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Epiphysis Vs condyle Condyle dissimilar to epiphysis …functionally …anatomically …immunologically …chemically & …ontogenetically condyle does not act like an epiphysis during orthopaedic treatment www.indiandentalacademy.com
Retention relapse ď Ż Deactivation of modification due to compression of retrodiskal tissues
ď Ż Hence long term adaptation is not clinically significant www.indiandentalacademy.com
Retention relapse
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Retention relapse
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conclusion No measurable long -term benefits for the mandible are derived from the first phase of “functional � appliance therapy in a two phase www.indiandentalacademy.com
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 www.indiandentalacademy.com
Clinical implications of viscoelasticity Dentoalveolar changes AP & vertical changes – differential eruption Transverse changes Buccal segment intrusion & extrusion www.indiandentalacademy.com
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 www.indiandentalacademy.com
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) www.indiandentalacademy.com
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 www.indiandentalacademy.com
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 www.indiandentalacademy.com
www.indiandentalacademy.com Leader in continuing dental education
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