Successfully reported this slideshow.

Cybernetics /certified fixed orthodontic courses by Indian dental academy


Published on

The Indian Dental Academy is the Leader in continuing dental education , training dentists in all aspects of dentistry and offering a wide range of dental certified courses in different formats.

Indian dental academy provides dental crown & Bridge,rotary endodontics,fixed orthodontics,
Dental implants courses.for details pls visit ,or call

  • Be the first to comment

Cybernetics /certified fixed orthodontic courses by Indian dental academy

  1. 1. The unit within the system with the most behavioral responses available to it controls the system. 1st Law of Cybernetics INDIAN DENTAL ACADEMY Leader in continuing dental education
  2. 2. A Seminar on By Pavan
  3. 3. Contents Introduction Cybernetic features Understanding of cybernetics approach Servosystem theory Condylar cartilage Control of maxillary growth Control of mandibular growth Three level arborization Mode of action of functional appliances Conclusion
  4. 4. Introduction Last 10 years have seen an increasing awareness of potential of functional appliances as valuable tool in armamentarium of orthodontists. In late 1960’s Petrovic & co-workers produced first rigorous demonstration that condylar cartilage’s growth rate & amount can be modified by using appropriate functional & orthopedic appliances. Later he employed the model of cybernetics & control theory to describe craniofacial growth patterns & method of operation of functional & orthopedic appliances.
  5. 5. “Cybernetics is the study of communication and control within and between humans, machines, organizations and society.”
  6. 6. Cybernetics The term itself originated in 1947 when Norbert Wiener used it to name a discipline apart from, but touching upon, such established disciplines as electrical engineering, mathematics, biology, neurophysiology, anthropology, and psychology. Wiener, Arturo Rosenblueth and Julian Bigelow Greek word kybernetes meaning "steersman"
  7. 7. Cybernetics Cybernetics, interdisciplinary science dealing with communication and control systems in living organisms, machines, and organizations was first introduced by the mathematician Wiener in 1948, as the science of communication and control in the animal and the machine (to which we now might add: in society and in individual human beings). Shannon’s theory
  8. 8. Cybernetics Cybernetics developed from investigations into how information is transformed into desired performance
  9. 9. Cybernetics The principle, known as feedback, is the fundamental concept of automation. Purposive behavior in humans or in machines requires control mechanisms that maintain order by counteracting the natural tendency toward disorganization.
  10. 10. Cybernetics Cybernetic concepts are used to link biological and technological functions. The use of feedback information as an important part of system development, helps scientists in the field of biology and technology understand cause and effect.
  11. 11. Cybernetics This complex idea relating to feedback can be translated into simpler terms of input and output. Input and output are components of a completed cycle of feedback. Input is placed into a system in order to receive a predicted output. In biological terms this would mean that a certain stimuli is placed upon an organism with the intent of inducing a certain predictable response from that organism.
  12. 12. Cybernetics “A distinguishing feature of the broad based field of Cybernetics is the use of feedback information to adapt or steer the entity toward a goal.”
  13. 13. Cybernetics Cybernetic Approaches Cause System Effect Standard Approaches
  14. 14. Cybernetics Cybernetic Approaches The (practical) Cybernetic view
  15. 15. Cybernetics Petrovic’s four types of explanation on craniofacial growth & orthodontic influence- 1. Deductive: used for description & classification of observations & for forecast of future events, including degree of possibility. A deductive explanation requires a logically organized framewor of knowledge ( e.g. cybernetic diagram containing precise quantitative data) 2.Deductivoprobabilistic: used to assess the relationship between description, classification of observations & events to be explained. This type of explanation is most common in medicine & orthodontics .It forms basis of differential diagnosis & prognosis. e.g.-computer based orthodontics diagram 3.Functional: corresponds to goal seeking description of technological systems. Various components of system that control craniofacial growth & development interact & provide feedback in precise, causal interdependence & responsiveness.
  16. 16. Cybernetics 4.Phylogenetic: 1st step is setting out of a sequence of major events through which system has evolved. 2nd step is discovery of events that are casually pertinent for the transformation of system. 3rd step is presentation of reasons for transformation. 4th step is elucidating the successfulness of transformation.
  17. 17. Cybernetic features
  18. 18. Cybernetic features Craniofacial growth is an extremely complex process. To explain method of operation of orthopedic & functional appliances, the following set of approaches is useful:
  19. 19. Cybernetic features Discoveries may be related by placing observations next to each other- outdated Diagrams displacing qualitative relations between observations can be constructed. Diagrams may be improved by using matrices in mathematical language. Cybernetics based on communication & information theory-based on feedback-useful approach
  20. 20. Catastrophe theory- Rene Thom (1972) A topologic concept to describe discontinuities. In cybernetics models ,discontinuities corresponds to sudden changes in references of control system.
  21. 21. • Catastrophe is defined as a sudden change or jump after a smooth progress. The theory therefore studies and classifies phenomena that are characterised by sudden shifts in behaviour arising from small changes in circumstances. These sudden changes are called "catastrophes" and the theory was developed as a method of analysing and classifying these changes. The catastrophe theory has been defined as a mathematical treatment of continuous actions producing a discontinuous result.
  22. 22.
  23. 23. Understanding of cybernetics approach Input & output- represented by arrows Each arrow represents a signal; at some point it may become a message.
  24. 24. Understanding of cybernetics approach The translation of message from one language to another is called transcodage % of data that are not indispensable to message but contribute to reliability of its transmission is called redundancy
  25. 25. Understanding of cybernetics approach Open loop No feedback loop Or Comparator Closed loop Regulator Main input constant Comparator detects disturbances It is –ve feedback system Servosystem or follow up system Main input not constant Physiologic system represented by black box
  26. 26. Input Orthodontic Functional & Orthodontic Appliances Output Correction Of Malocclusion And Intermaxillary Relation Genetically determined & cybernetically organized Biologic features of Phenomena characterizing, Inducing or controlling Spontaneous & appliance Modulated growth Relative primary to following: Mandible lengthening Maxillary lengthening Teeth movements Research design clinical versus biologic approach
  27. 27. Servosystem theory (Alexander Petrovic 1970)
  28. 28. Servosystem Theory It is considered to be the last major theory of craniofacial growth to emerge within 20th century, developed by Alexander Petrovic & his colleagues at University of Strasburg in 1970’s . Development of Servosystem theory was initiated because of interest in growth & development of connective tissue & effect of intrinsic & extrinsic factors particularly on condylar cartilage.
  29. 29. Servosystem
  30. 30. Servosystem Theory A further step in understanding mechanism of craniofacial growth was made when Charlier, Petrovic & Stutzmann detected in organ culture the following dissimilarities concerning different growth cartilages-
  32. 32. Servosystem Theory According to the Servosystem theory, the sagittal position of the upper dental arch is cybernetically the “constantly changing reference input”. This position depends on the growth in length of the upper jaw, which is controlled by STH and somatomedin as well as by septal cartilage growth and by tongue growth. The effect of septal cartilage growth on the forward growth of the maxilla is mediated through a direct thrust, through labionarinary muscles and through the superior labial frenum and septopremaxillary ligament.
  34. 34. Servosystem Theory The sagittal position of the lower dental arch is cybernetically, “the controlled variable”
  35. 35. The “operation of confrontation” between the upper and lower dental arches is, cybernetically, the “peripheral comparator” of the Servosystem. Servosystem
  36. 36. With time, the increased activity of the lateral pterygoid muscle and, consequently, the amplified solicitation of the retrodiscal pad induces, first, a posterior growth rotation of the mandible and, second, a supplementary growth rate and amount of the condyle. Servosystem
  37. 37. During the facial growth, everything occurs as if, in the Servosystem controlling mandibular morphogenesis, the shape is – in cybernetic language – the “reference input,” and the rat and amount of growth are “controlled variables.” An important quantitative aspect of the functioning of the Servosystem should be pointed out: the greater relative retro position of the lower dental arch, i.e., the greater the “deviation” between the inferior and superior dental arches, the greater the “deviation signal” arising form the “peripheral comparator” and the “detectors” of occlusal adjustment. Servosystem
  38. 38. This increased deviation will, in turn, lead to increased supplementary activity of the lateral pterygoid muscle and of the retrodiscal pad and will result in increased supplementary growth of the condylar cartilage. Servosystem
  39. 39. The Servosystem controlling the growth of the condylar cartilage comprises, in addition to the “peripheral comparator” (occlusal relationship), a “central comparator” located in the central nervous system. Servosystem
  40. 40. In sum, “unlike what seems to occurs in the so-called primary cartilages, the physiologic effect of factors controlling the growth of the facial skeleton, especially of the condylar cartilage ( a secondary cartilage), is not limited to simple commands, but includes relays implying interactions and feedback loops, all of which form a structured system, a Servosystem, in which the position of occlusal adjustment plays the role of the peripheral comparator.” Servosystem
  41. 41. Condylar Cartilage Adaptive to both extrinsic & local biomechanical & functional factors
  42. 42. Reptiles Condylar Cartilage QuadratusArticular
  43. 43. IN MAMMALS- joint formed by 2 dermal bones Condylar Cartilage SquamosalDentary
  44. 44. Condylar cartilage growth is integrated into an organized functional whole that has form of Servosystem & able to modulate lengthening of condyle so that lower jaw adapts to upper jaw during growth Condylar Cartilage
  45. 45. Condylar cartilage in growing mammal is composed of the following zones: Zone of growth Zone of maturation Zone of erosion Zone of endochondral ossification Specific features of condylar Cartilage Condylar Cartilage
  46. 46. Condylar Cartilage
  47. 47. Condylar Cartilage
  48. 48. FACTORS AFFECTING CONDYLAR CARTILAGE GROWTH Lateral pterygoid muscle & retrodiscal pad tissue Effect of hormones Intrinsic regulation of condylar cartilage growth rate Other hormonal & humoral factors c-AMP
  51. 51. Resection of LPM & retrodiscal pad The interruption of circulatory dependence on the blood supply originating directly from LPM & indirectly through retrodiscal pad may contribute to inhibited differentiation of skeletoblasts. Experimental studies on juvenile rats were carried out in which LPM were resected. FACTORS AFFECTING CONDYLAR CARTILAGE GROWTH
  52. 52. It was observed that growth of condylar cartilage & lengthening of mandible continue but significantly decreased. FACTORS AFFECTING CONDYLAR CARTILAGE GROWTH
  54. 54. FACTORS AFFECTING CONDYLAR CARTILAGE GROWTH Intrinsic regulation of condylar cartilage growth rate
  55. 55. FACTORS AFFECTING CONDYLAR CARTILAGE GROWTH Effect of hormones • If blood levels of STH or testosterone increases , lengthening of mandible greater than maxilla. • Operation of confrontation then produces deviation signal that decreases activity of LPM & movements of retrodiscal pad , resulting in decrease in condylar cartilage growth rate. • If stimulation of retrodiscal pad is reduced dividing cells are relocated in less posterior direction resulting in vertical orientation of newly formed endochondral bone trabeculae producing closing of angle & anterior growth rotation. • If STH or testosterone decreases then optimum occlusal adjustment is maintained by opening of angle.
  56. 56. FACTORS AFFECTING CONDYLAR CARTILAGE GROWTH Effect of hormones • During transition phase as mandible is constantly moved : 1. Increased contractile activity of LPM. 2. Increase in no. of dividing cells in condylar cartilage. 3. Increased stimulation of retrodiscal pad. As a result dividing cells located in more posterior direction producing opening of angle or posterior growth rotation. 4. If suboptimal occlusal adjustment is achieved after jumping o bite angle closes again.
  57. 57. FACTORS AFFECTING CONDYLAR CARTILAGE GROWTH Effect of hormones If STH or testosterone level rises beyond certain hormonal level :“ Jumping of bite “ occurs.
  60. 60. FACTORS AFFECTING CONDYLAR CARTILAGE GROWTH Other hormonal & humoral factors Insulin, glucagon, parathormone, calcitonin , some mitogenic peptides which corresponds to fibroblast growth factor, endothelial cell derived growth, etc. have stimulating effect on condylar cartilage growth rate.
  61. 61. FACTORS AFFECTING CONDYLAR CARTILAGE GROWTH c-AMP • Inverse relationship between it & growth rate of skeletoblasts & prechondroblasts observed. • Does not directly inhibits cell multiplication but appears to be amplifier of still unknown inhibitory signal. • It also has a direct effect on the cell cycle • A brief surge of endogenous c-AMP involved with surge of Calcium in initiating the cell division process (Stutzmann & Petrovic 1982 )
  62. 62. Correlation between growth direction of condyle & sagittal distribution of dividing cells in condylar cartilage
  63. 63. • A histologic & radioautography study was made of distribution of dividing cells in a sagittal section of condylar cartilage of juvenile rats. • Condylar cartilage divided into 4 equal sections from anterior to posterior & cells counted.
  64. 64. Each experimental group was subjected to specific orthopedic treatment.
  65. 65. • Results showed that both treatment with the postural hyperpropulsor & with the growth hormone produced significant increase in growth rate of condylar cartilage to control group (Charlier et al, 1968, 1969a; Petrovic et al , 1975b)
  66. 66.
  67. 67.
  68. 68. • Stutzmann angle- the angle formed between main axis of endochondral bone trabeculae in condyle with mandibular plane as viewed on lateral cephalogram. • In anterior growth rotation there is closing of angle as seen in treatment with growth hormone. • In posterior growth rotation there is opening of angle as seen in treatment with postural hyperpropulsor
  69. 69.
  70. 70. Condylar growth is not exclusively a result of the lengthening of pre-existing endochondral bone trabeculae under condylar cartilage but also a result of growth of bone trabeculae that are formed in parallel & posteriorly oriented in condylar cartilage.
  71. 71. Control of maxillary growth • Increase in length of maxilla • Increase in width of maxilla
  72. 72. Control of maxillary
  73. 73. Control of Mandibular growth Responsive to changes in lengthening of maxilla
  74. 74. Control of Mandibular growth Upper dental arch -- constantly changing reference input Lower arch -- controlled variable.
  75. 75. Control of Mandibular growth “ Operation of confrontation “ between dental arches in certain cases elicits deviation signal that modifies activity of LPM & other muscles of mastication , allowing mandible to adjust to optimal occlusal position This change in LPM activity probably influences growth of condylar cartilage.
  76. 76. Control of Mandibular growth • In anterior growth rotation - Subperiosteal ossification rate & alveolar bone turn over is increased • In posterior growth rotation - Decreased
  77. 77. Control of Mandibular growth Peripheral comparator maintains optimal to suboptimal occlusal relationship. If it is disturbed can lead to topologic bifurcation type instability.
  78. 78. Control of Mandibular
  79. 79. Three level arborization The first level, based on the quantitative determination of the difference between maxillary and mandibular sagittal growth, likewise has three main branches •The second level based on variations in the direction of mandibular and maxillary growth, affects each of the three main branches •The third level, based on the occlusal relationship that functions as the peripheral comparator of the Servosystem, has subdivisions representing either an aggravation or a melioration of malocclusions resulting from the first two arborizational levels.
  80. 80. Mode of action of functional appliancesPostural Hyperpropulsor • Appropriate functional appliances that place the rat mandible in forward postural position increases condylar cartilage growth rate & amount. • Periodic increase in thickness of postural hyperpropulsor, produces increase in LPM activity & of retrodiscal pad, consequently increasing rate & amount of condylar cartilage growth.
  81. 81. Mode of action of functional appliances If appliance removed after growth completed – little or no relapse If removed before growth completed- no relapse if good intercuspation Postural Hyperpropulsor
  82. 82. Mode of action of functional appliances Postural Hyperpropulsor If good intercuspation not achieved- then comparator of Servosystem imposes an increased or decreased growth rate until state of good intercuspation achieved
  83. 83. Mode of action of functional appliances Postural Hyperpropulsor
  84. 84. Mode of action of functional appliances Postural Hyperpropulsor
  85. 85. Mode of action of functional appliances Class II elastics • It is seen that they are not only orthopedic devices capable of moving teeth but also functional appliances capable of stimulating growth rate & amount of condylar cartilage. • Mechanism of action- Through mainly retrodiscal pad
  86. 86. Mode of action of functional appliances Class II elastics
  87. 87. Mode of action of functional appliances HERREN (L.S.U) ACTIVATOR (Louisiana state university) • It opens the construction bite beyond the postural rest position. • Acc. To Herren (1953) & Auf der maur (1978) the wearing of appliance does not bring about any increased activity of LPM as no free movement of mandible possible- Should be worn part time
  88. 88. Mode of action of functional appliances HERREN (L.S.U) ACTIVATOR 2 STEP ACTION- 1. when appliance is worn- Forward positioning of mandible is the cause of reduced increase in length of LPM 2. When appliance is not worn- New sensory engram Mandible functioning in more forward position More stimulation of retrodiscal pad activity • Repetitive activity of pad leads to earlier onset of condylar chondroblasts hypertrophy • Decrease in no of functional chondroblasts • Decrease in prechondroblasts multiplication restraining signal • Increase in condylar cartilage growth
  89. 89. Mode of action of functional appliances FRANKEL LATERAL VESTIBULAR SHIELD • The appliance acts by stimulating midpalatal suture growth & to lesser extent by increasing bone apposition on external subperiosteal layer of maxilla • Buccal shield --- eruptive pathway of teeth
  90. 90. Mode of action of functional
  91. 91. Effect of various functional appliances on growth of rat mandible
  92. 92. Summary of method of operation of functional appliances 1. Class II elastics, postural hyperpropulsar, frankels regulator, Balters’ bionator , Clark twin block all exert effects mainly through movement of mandible. Their stimulating effects are produced mainly during wearing of appliance. 2. Herren & L.S.U activators & extraoral forward traction on mandible seem to exert their effects mostly through sagittal repositioning of mandible.
  93. 93. Summary of method of operation functional
  94. 94. Summary of method of operation functional appliance Regardless of differences in mode of action, the following causal chain is involved- Functional appliance Increase contractile activity of LPM Intensification of repetitive activity of retrodiscal pad
  95. 95. Summary of method of operation functional appliance Increase in growth stimulating factors: 1. Enhancement of local mediators 2. Reduction of local mediators (factors causing negative feedback effects) • Change in condylar trabecular orientation • Additional growth of condylar cartilage • Additional subperiosteal ossification of posterior border of mandible Supplementary lengthening of mandible
  96. 96. Active retropulsion of mandible (chin caps) • More orthopedic than functional. • If growing rats subjected to active retropulsion with chin cap therapy- • No. of dividing cells in mandibular condylar cartilage decreases • Direction of growth becomes more vertical • Closing of Stutzmann's angle • Decrease in length of mandible markedly
  97. 97. Are these experimental findings relevant to humans?
  98. 98. CONCLUSION • Rat, mouse, guinea pig, rabbit, monkey, human. • Any claim that the responsiveness of the condylar cartilage to functional appliances is different in growing laboratory animals from that in the child is, for the time being, biologically unsupported.
  99. 99. CONCLUSION • Interindividual heterogeneity in human mandibular tissue growth and responsiveness originates from distinct quantitative differences at the tissue, cell, and molecular level. • Six biological levels and 11 corresponding rotational types.
  100. 100. CONCLUSION These results demonstrate that a methodologically rigorous evaluation of the effectiveness of a functional appliance must take into account the biologic heterogeneity of the human mandibular tissues.
  101. 101. CONCLUSION So previously reported negative results in the literature may be due not only to the characteristics of the appliance used, but also to errors in identifying biologic growth category and inappropriately selected control.
  102. 102. "The simplest schoolboy is now familiar with truths for which Archimedes would have sacrificed his life." — Ernest Renan (1823- 92), French philosopher
  103. 103. All human actions have one or more of these seven causes: chance, nature, compulsion, habit, reason, passion, and desire.
  104. 104. Thank you For more details please visit