Growth relativity hypothesis1 /certified fixed orthodontic courses by Indian dental academy

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Growth relativity hypothesis1 /certified fixed orthodontic courses by Indian dental academy

  1. 1. Growth relativity hypothesis -John voudouris, 2000 www.indiandentalacademy.com
  2. 2. INDIAN DENTAL ACADEMY Leader in continuing dental education www.indiandentalacademy.com www.indiandentalacademy.com
  3. 3. Growth relativity hypothesis Hypothesis presented for the mechanism of condylar-fossa growth modification with propulsive mandibular appliances, such as the Herbst & Twin-block www.indiandentalacademy.com
  4. 4. Growth relativity hypothesis Introduction Extensive use of orthopaedic appliances – Herbst, Twin-block & other auxiliaries “Why” & “How” www.indiandentalacademy.com
  5. 5. Growth relativity hypothesis  Normal C-GF growth  Condylar remodelling  Pathosis at the condyle …. adaptation www.indiandentalacademy.com
  6. 6. Growth relativity hypothesis Condylar modification Genetic theory– Genetic control  pre-natal  Effectiveness of orthopaedic appliances on condylar growth ?- Brodie www.indiandentalacademy.com
  7. 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 www.indiandentalacademy.com
  8. 8. Growth relativity hypothesis www.indiandentalacademy.com
  9. 9. Growth relativity hypothesis www.indiandentalacademy.com
  10. 10. Growth relativity hypothesis  LPM tendon – anterior border of fibrous capsule www.indiandentalacademy.com
  11. 11. 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
  12. 12. Growth relativity hypothesis Functional matrix hypothesis – influence of non-skeletal tissues Exact method of condylar growth stimulation? www.indiandentalacademy.com
  13. 13. 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
  14. 14. Growth relativity hypothesis  Evidence of decreased muscle activity – use of propulsive orthopaedic appliances  Cause for growth modulation? www.indiandentalacademy.com
  15. 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” www.indiandentalacademy.com
  16. 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 www.indiandentalacademy.com
  17. 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” www.indiandentalacademy.com
  18. 18. Growth relativity hypothesis 3 main foundations Displacement Viscoelasticity Referred force (transduction) www.indiandentalacademy.com
  19. 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 www.indiandentalacademy.com
  20. 20. Growth relativity hypothesis www.indiandentalacademy.com
  21. 21. www.indiandentalacademy.com
  22. 22. 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
  23. 23. www.indiandentalacademy.com
  24. 24. www.indiandentalacademy.com
  25. 25. Growth restriction-glenoid fossa  GF - posteroinferior growth – Bjork, P opovich & Thom pson  posteriorly directed viscoelastic tissues – effect condyle and GF  Reverse growth– relocation anteroinferiorly  Class II correction www.indiandentalacademy.com
  26. 26. Growth restriction-glenoid fossa www.indiandentalacademy.com
  27. 27. Light bulb analogy of condylar growth & retention www.indiandentalacademy.com
  28. 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 www.indiandentalacademy.com
  29. 29. Epiphysis Vs condyle www.indiandentalacademy.com
  30. 30. 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
  31. 31. Retention relapse  Deactivation of modification due to compression of retrodiskal tissues  Hence long term adaptation is not clinically significant www.indiandentalacademy.com
  32. 32. Retention relapse www.indiandentalacademy.com
  33. 33. Retention relapse www.indiandentalacademy.com
  34. 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. www.indiandentalacademy.com
  35. 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 www.indiandentalacademy.com
  36. 36. Clinical implications of viscoelasticity  Dentoalveolar changes  AP & vertical changes – differential eruption  Transverse changes  Buccal segment intrusion & extrusion www.indiandentalacademy.com
  37. 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 www.indiandentalacademy.com
  38. 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) www.indiandentalacademy.com
  39. 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 www.indiandentalacademy.com
  40. 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 www.indiandentalacademy.com
  41. 41. www.indiandentalacademy.com Leader in continuing dental education www.indiandentalacademy.com

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