Cybernetic theory of craniofacial growth /certified fixed orthodontic courses by Indian dental academy


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Cybernetic theory of craniofacial growth /certified fixed orthodontic courses by Indian dental academy

  1. 1. Cybernetic Theory of Craniofacial Growth INDIAN DENTAL ACADEMY Leader in continuing dental education
  2. 2. Petrovic 1977 • Demonstrate qualitative and quantitative relationship between observed and experimental findings. • Broader understanding of orthodontic problems, and action of appliances • Familiarity of orthodontists with cybernetics
  3. 3. Cybernetics Transfer of Information • Cybernetic systems operate through transfer of information • Physical, Chemical, Electromagnetic
  4. 4. Input Input Process Cybernetic System Transfer Function Output Output
  5. 5. Physiological cybernetic systems Open loop Closed loop Regulator Servosystem Comparator Feedback Peripheral Central Positive Negative
  6. 6. Open Loop Output has no affect on the input
  7. 7. Closed Loop Relationship maintained between input and output Input Comparator Feedback Loop Transfer function Output
  8. 8. Regulation Type of Closed Loop Input is constant Any change of the input will initiate a “regulatory process” Input Comparator Regulation of input Transfer function
  9. 9. Servosystem Type of Closed Loop
  10. 10. Components of a Servosystem COMMAND Reference Input Elements Actuator, Coupling System, Controlled System COMPARATOR Output (Controlled Variable) Central Comparator (sensory engram) Reference Input Deviation Signal Performance Analyzing Elements Performance
  11. 11. Growth of the Face According to the Servosystem Theory
  12. 12. Types of Cartilage Primary
  13. 13. Types of Cartilage Secondary
  14. 14. Primary Cartilage: Epiphysis, Synchondrosis, Nasal Septum, Ethmoid Sphenoid Secondary Cartilage: Condyle, Coronoid, Mid Palatal Suture, Fracture Callus
  15. 15. Factors influencing Primary Growth Cartilage Secondary Cartilage Hormones Yes Yes Local Factors No (Chondroblasts Yes (Pre- Orthopaedic appliances Only Direction Direction and Amount surrounded by matrix) chondroblasts not surrounded by matrix) Charlier, Petrovic, Stutzmann Strasburg, France
  16. 16. Role of Lateral Pterygoid and Retrodiscal Pad •Blood Supply •Bio-mechanic
  17. 17. Relationship Between Lateral Pterygoid, Retrodiscal Pad and Condyle MENISCUS LPM RDP
  18. 18. Stutzmann and Petrovic Proper function of Lateral Pterygoid and retrodicsal pad: • Excision of Lateral Pterygoid • Reduced function of the Retrodiscal pad (Rat experiments)
  19. 19. The Face as a Servosystem Input – Maxillary dental arch Output – Adjustment of the position of mandibular dental arch
  20. 20. Growth of the maxilla Growth in Length Growth in Width
  21. 21.
  22. 22. Growth in Length: Traction SeptoPremaxillary ligament Induction Growth of Nasal Septum Biomechanical Labio narinary Muscles Release of STH Somatomedin Thrust Growth of Pre Maxillary extremity Anterior shift Of premaxillary bones Growth of PremaxilloMaxillary suture Protrusion of Upper Incisors Increased size Of Tongue Thrust Protrusion of Lower Incisors Direct Action Growth of Maxillo Palatine suture
  23. 23. Growth in Width: Growth of Lateral cartilaginous masses of Ethmoid Release of STH Somatomedin Transverse Separation of premaxillae Outward growth Of maxillary bones Growth of cartilage B/w greater wings & body of sphenoid Increased size Of Tongue Outward shift of Alveolus and molars Direct effect Growth of inter Pre Maxillary suture Transverse Seperation of Horizontal Maxilla and Palatine plates Growth of mid Palatine suture Outward Appositional Bone growth
  24. 24. The Face as a Servosystem Release of Hormones (Command) LPM & RDP (Coupling system) Position of Maxillary Dental arch (Ref Input) Hormones Growth at condyle (Controlled System) OCCLUSION Output Periodontium, Teeth Musculature Joint Actuating signal Actuator (Motor Cortex) Brain (sensory engram) (Comparator) Deviation Signal Mastication (Performance)
  25. 25. Growth at the Posterior Border of the Ramus
  26. 26. Other Terms Related to a Servosystem Gain = Output Input Enhancement (Gain>1) Attenuatation (Gain <1) 1. Large amounts of TESTOSTERONE 2. Small or large amounts of 2. Small amounts of OESTROGEN TESTOSTERONE 3. Large amounts of 3. Very small amounts of CORTISONE OESTROGEN 1. STH – Somatomedin
  27. 27. Attractor Cusp to fossa relation Repeller Cusp to cusp relation Disturbances Abnormal tooth position Occlusal interferences Arthritis Muscle Inflammation Periodontitis, Pulpitis
  28. 28.
  29. 29. Peripheral Comparator Before development of Occlusion:•Sensory engram not developed •Servosystem does not operate •Genetic influence on mandibular growth •Anodontia After Development of Occlusion:•Sensory engram forms •Peripheral comparator controls growth
  30. 30. Failure of Servosystem to Control Growth • Peripheral comparator faulty – Caries, Mutilated dentition. •Discrepancy between rotation pattern (Anterior or Posterior) and location of comparator.
  31. 31. Discontinuities Stable Unstable Catastrophe Theory Stable
  32. 32. Bifurcation
  33. 33. Catastrophe Theory
  34. 34. Importance of Discontinuities •Growth prediction , treatment planning , decision making •Stability of occlusion after it is established •Genotype does not directly influence the phenotype
  35. 35. Height of Bifurcation OR
  36. 36. The Sensory Engram • Collection of feedback loops • Blueprint of ideal muscular function/position • CNS tends to operate along these feedback loops
  37. 37. Optimality of Function •Minimum deviation signal •CNS always tries to revert back to optimal position •Observation of Chain gang prisoners by Jacobs (1968)
  38. 38. Development of Skeletal Malocclusion According to the Servosystem Theory
  39. 39. For every unit of Growth hormone released, the amount of growth in the maxilla is less than in the mandible.
  40. 40. Increase in length LPM(max) LPM(norm) LPM(min) MAX Retrognathism Prognathism L1 N L2 Hormone levels
  41. 41. Action of Functional Appliances
  42. 42. Two Types of Functional Appliances: ) Activator, Postural hyperpropulsor, Frankel appliance, Twin block, Bionator, Class II Elastics(?) ) Herren activator, LSU activator, Harvold-Woodside activator, Extra oral traction on the mandible.
  43. 43. FIRST GROUP: Position mandible Forward Increased activity of LPM and RDP Less fatigable fibres in LPM •Oudet et al (1988) •Carlson et al (1990) LPM “helped to contract more” by Functional appliances.
  44. 44. CELLULAR LEVEL 1. Precursor Skeletoblast – pleuripotent, fibroblast like. 2. Prechondroblast – faster cell cycle, matures into Chondroblast
  45. 45. Chondroblasts lost Increased multiplication of prechondroblasts (hypertrophy, surgically removed) Local control prechondroblasts over multiplication of Originates from chondroblastic layer •Stutzmann and Petrovic (1982, 1990)
  46. 46.
  47. 47. Functional appliances (especially Class II elastics) Increased activity of RDP Increased nutrients and growth factors supplied and inhibitors removed. Increased mitoses and earlier hypertrophy of chondroblasts.
  48. 48. Reduced negative feedback signal reaching prechondroblasts Increased growth at the condyle
  49. 49. Cytoplasmic junctions between skeletoblasts reduce. Transmission of inhibitory factors reduce. Increased mitotic rate and rate of differentiation into prechondroblasts.
  50. 50. SECOND GROUP: Position mandible forward , open in beyond rest position. No increase in activity of LPM •Herren (1953) •Auf der Maur (1978) Yet there was an increase in growth
  51. 51. wo steps: ) While appliance is worn:Forward position Reduction of length of LPM New sensory engram ) While appliance is not worn:New sensory engram Functioning in anterior position Increased activity of RDP
  52. 52. Action of first group while appliance is worn Action of second while appliance is not worn group
  53. 53. CLINICAL IMPLICATIONS 1) Principle of optimality of function :Less relapse tendency if post orthodontic treatment muscular activity produces a lower deviation signal.
  54. 54. 2) Removal of functional appliance – when growth is complete. 3) If removed when growth not complete – Proper intercuspation.
  55. 55. 4) Understanding of when, and for how long a particular functional appliance should be worn. First group – Full time Second group – Part time
  56. 56. 5) Proper functioning of LPM and RDP important for growth – Proper parent counseling. 6) Sensory engram poorly developed in younger children. 7) Utilization of high hormonal activity at puberty.
  57. 57. Drawbacks Lot of importance on condyle: Fracture? Peripheral comparator (occlusion) discrepancies may be overcome by Dentoalveolar changes.
  58. 58. Occurrence of Class II end on relation is seen often? Action of reverse pull headgear on maxilla (primary cartilage)
  59. 59. References Dentofacial Orthopedics with Functional Appliances Graber, Rakosi, Petrovic Craniofacial Growth Series – Monograph 23 (Craniofacial Growth Theory and Orthodontic Treatment – Edited by Carlson)
  60. 60. Treatment objectives and case retention: Cybernetic and myometric considerations R.M. Jacobs Am J Orthod, 58:552-564, 1970 Grant’s Atlas of Anatomy
  61. 61. Thank you For more details please visit