Theories of growth /certified fixed orthodontic courses by Indian dental academy


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  • Theories of growth /certified fixed orthodontic courses by Indian dental academy

    1. 1. INDIAN DENTAL ACADEMY Leader in continuing dental education
    2. 2. Genetic Epigenetic Sutural Cartilagenous Servosystem
    3. 3. INTRODUCTION Over many years various theories of growth have been proposed for the craniofacial complex. The Genetic theory, Epigenetic theory,Scott’s Cartilagenous Hypothesis, Sicher’s Sutural Dominance theory, attempt to explain the growth of the craniofacial complex with different growth determinants and have their own limitations. The Servo system theory of growth is based on a factorial qualitative analysis which takes into account various factors which determine a coordinated growth of the craniofacial complex as a whole. The Servo system theory attempts to explain craniofacial growth and the modus operandi of Functional appliances.
    4. 4. How does growth affect Orthodontics? Malocclusion Orthodontic Therapy Abnormal Growth Of Craniofacial bones Malfunction of The Orofacial neuromusculature
    5. 5. Malocclusion •Impaired Mastication •Unfortunate Esthetics Abnormal Growth Of Craniofacial bones Malfunction of The Orofacial neuromusculature •Dysfunction of the TMJ •Susceptibility to Periodontal diseases •Susceptibility to Dental Caries •Impaired speech due to malpositions of teeth
    6. 6. GROWTH THEORIES GENETIC CONTROL THEORY: • Genotype supplies all the information required for phenotype expression. • Does not address the question of local and general factors modifying gene expression.
    7. 7. MENDEL’S GENETIC THEORY Mendel, the father of genetics stated that the diploid expression of the chromosome is derived from two monoploids; one each from both the parents. The acquired characters are expressed by the offsprings due to mutations. The dominant characters are expressed where as the recessive are carried and expressed less often Unfortunately the undesired characters are dominant more frequently.
    8. 8. THEME OF GENETIC THEORY •Changing complexity •Shift from competent to fixation •Shift from dependent to independent •Ubiquity of genetic control modulated by environment at all levels the genetic control of development is constantly being modified by environmental interactions which persist through life.
    9. 9. GROWTH THEORIES EPIGENETIC THEORY Epigenetic factors are those which are determined genetically, and are effective outside the cells and tissues in which they are produced These occur only indirectly, due to reactions of the structures which they influence Van Limborg- they can have an effect on the adjacent structures such as local epigenetic factors (eg: embryonic induction influences brain,eyes,inner ear) or are produced at distance and exert a general epigenetic influence (eg: Sex and growth harmones)
    10. 10. GROWTH THEORIES SICHER’S SUTURAL DOMINANCE THEORY: • He believed that craniofacial growth occurs at sutures. • Paired parallel sutures which attach the facial bones to the cranial base and skull push the nasomaxillary complex forwards to compare with mandibular growth. • Acknowledges the genetic influence on growth at the sutures. • Transplantation of sutures to another site showed that there was no innate growth potential. •Doesn’t justify cases of Microcephaly and Hydrocephaly.
    11. 11. GROWTH THEORIES CARTILAGE DIRECTED GROWTH THEORY: • James Scott- 1953, 1954, 1967 • Cartilage has intrinsic growth potential. • Role of Periosteum and sutures are only secondary. • All cartilages through out the skull are primary centres of growth. • Growth of the maxilla is attributed to the growth of the Nasal septal cartilage. •Nasal septal cartilage is the pacemaker of growth for the nasomaxillary complex. •The mandible is like the diaphysis of a long bone bent with epiphyseal cartilages at both ends.
    12. 12. GROWTH THEORIES CARTILAGE DIRECTED GROWTH THEORY: • Epiphyseal cartilages transplanted to a different area will continue to grow - innate growth potential. • Nasal septal cartilages also grow when transplanted to another site. •Removal of nasal septal cartilages gives rise to retarded midface development. • Petrovic’s studies have shown that only primary cartilages grow in organ culture and not secondary cartilages.
    13. 13. SERVOSYSTEM THEORY AND CYBERNETICS Craniofacial growth is a multifaceted process where the connections and interrelationships are complex with interactions and feedbacks. The Servo system theory uses the Cybernetic language of information and communication as a tool to explain the influence of various factors - extrinsic and intrinsic on Craniofacial growth. “Cybernetics” derived from a greek word meaning ‘steersman’ by Dr.Rosenbleuth and Norbert Weiner and others in 1947.
    14. 14. SERVOSYSTEM THEORY AND CYBERNETICS CYBERNETICS: • Used to explain Systems and Circuit analysis. • Can also be used in biomedical sciences to explain negative and positive feedback loops, self regulation, gain and in the process explain physiological processes.
    15. 15. SERVOSYSTEM THEORY AND CYBERNETICS CYBERNETICS: • A Cybernetically organized system operates through signals transmitting information. • Signals can be physical, chemical or electromagnetic in nature and of low energy. NorbertTr - RH Weiner TSH THYROXINE T3,T4
    16. 16. 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
    17. 17. Cybernetics Transfer of Information • Cybernetic systems operate through transfer of information • Physical, Chemical, Electromagnetic
    18. 18. Input Input Process Cybernetic System Transfer Function Output Output
    19. 19. Physiological cybernetic systems Open loop Closed loop Regulator Servosystem Comparator Feedback Peripheral Central Positive Negative
    20. 20. Open Loop Output has no affect on the input
    21. 21. Closed Loop Relationship maintained between input and output Input Comparator Feedback Loop Transfer function Output
    22. 22. 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
    23. 23. Servosystem Type of Closed Loop
    24. 24. 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
    25. 25. Growth of the Face According to the Servosystem Theory
    26. 26. Types of Cartilage Primary
    27. 27. Types of Cartilage Secondary
    28. 28. Primary Cartilage: Epiphysis, Synchondrosis, Nasal Septum, Ethmoid Sphenoid Secondary Cartilage: Condyle, Coronoid, Mid Palatal Suture, Fracture Callus
    29. 29. Factors influencing Primary Growth Cartilage Secondary Cartilage Hormones Yes Yes Local Factors No (Chondroblasts Yes (Pre- surrounded by matrix) chondroblasts not surrounded by matrix) Only Direction Direction and Amount Orthopaedic appliances Charlier, Petrovic, Stutzmann Strasburg, France
    30. 30. Role of Lateral Pterygoid and Retrodiscal Pad •Blood Supply •Bio-mechanic
    31. 31. Relationship Between Lateral Pterygoid, Retrodiscal Pad and Condyle MENISCUS LPM RDP
    32. 32. Stutzmann and Petrovic Proper function of Lateral Pterygoid and retrodicsal pad: • Excision of Lateral Pterygoid • Reduced function of the Retrodiscal pad (Rat experiments)
    33. 33. The Face as a Servosystem Input – Maxillary dental arch Output – Adjustment of the position of mandibular dental arch
    34. 34. Growth of the maxilla Growth in Length Growth in Width
    35. 35. 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
    36. 36. 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
    37. 37. 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)
    38. 38. Growth at the Posterior Border of the Ramus
    39. 39. 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
    40. 40. Attractor Cusp to fossa relation Repeller Cusp to cusp relation Disturbances Abnormal tooth position Occlusal interferences Arthritis Muscle Inflammation Periodontitis, Pulpitis
    41. 41.
    42. 42. Peripheral Comparator Before development of Occlusion:•Sensory engram not developed •Servosystem does not operate •Genetic influence on mandibular growth •Anodontia is not explained After Development of Occlusion:•Sensory engram forms •Peripheral comparator controls growth
    43. 43. Failure of Servosystem to Control Growth • Peripheral comparator faulty – Caries, Mutilated dentition. •Discrepancy between rotation pattern (Anterior or Posterior) and location of comparator.
    44. 44. Discontinuities • DISCONTIUITIES as seen above are important points in control of cranio-facial growth, and should always be taken into consideration during growth prediction, treatment planning and decision making. As mentioned earlier, a given occlusal pattern can be formed due to any number of causes. But once it is established, it remains relatively stable, as any local changes are minimized by the regulatory process
    45. 45. Discontinuities Stable Unstable Catastrophe Theory Stable
    46. 46. Importance of Discontinuities •Growth prediction , treatment planning , decision making •Stability of occlusion after it is established •Genotype does not directly influence the phenotype
    47. 47. Bifurcation
    48. 48. Catastrophe Theory • Another characteristic of the peripheral comparator is the existence of DISCONTINUITIES. Between two stable points (intercuspation) there is an area of instability (cusp to cusp relation). • So a stable phase can never be changed to another stable phase without an unstable phase. • This forms the basis of the CATASTROPHE THEORY
    49. 49. Catastrophe Theory
    50. 50. The Sensory Engram • Collection of feedback loops • Blueprint of ideal muscular function/position • CNS tends to operate along these feedback loops
    51. 51. Optimality of Function •Minimum deviation signal •CNS always tries to revert back to optimal position •Observation of Chain gang prisoners by Jacobs (1968)
    52. 52. Development of Skeletal Malocclusion According to the Servosystem Theory
    53. 53. For every unit of Growth hormone released, the amount of growth in the maxilla is less than that in the mandible.
    54. 54. Increase in length LPM(max) LPM(norm) LPM(min) MAX Retrognathism Prognathism L1 N L2 Hormone levels
    55. 55. Action of Functional Appliances
    56. 56. Two Types of Functional Appliances: 1) Activator, Postural hyperpropulsor, Frankel appliance, Twin block, Bionator, Class II Elastics(?) 2) Herren activator, LSU activator, Harvold-Woodside activator, Extra oral traction on the mandible.
    57. 57. 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.
    58. 58. CELLULAR LEVEL 1. Precursor Skeletoblast – pleuripotent, fibroblast like. 2. Prechondroblast – faster cell cycle, matures into Chondroblast
    59. 59. Chondroblasts lost Increased multiplication of prechondroblasts (hypertrophy, surgically removed) Local control prechondroblasts over multiplication of Originates from chondroblastic layer •Stutzmann and Petrovic (1982, 1990)
    60. 60.
    61. 61. 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.
    62. 62. Reduced negative feedback signal reaching prechondroblasts Increased growth at the condyle
    63. 63. Cytoplasmic junctions between skeletoblasts reduce. Transmission of inhibitory factors reduce. Increased mitotic rate and rate of differentiation into prechondroblasts.
    64. 64. 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
    65. 65. 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
    66. 66. Action of first group while appliance is worn Action of second while appliance is not worn group
    67. 67. CLINICAL IMPLICATIONS 1) Principle of optimality of function :Less relapse tendency if post orthodontic treatment muscular activity produces a lower deviation signal.
    68. 68. 2) Removal of functional appliance – when growth is complete. 3) If removed when growth not complete – Proper intercuspation will be hindered.
    69. 69. 4) Understanding of when, and for how long a particular functional appliance should be worn. First group – Full time Second group – Part time
    70. 70. 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.
    71. 71. Drawbacks 1) Lot of importance on condyle: Fracture? 2) Peripheral comparator (occlusion) discrepancies may be overcome by Dentoalveolar changes. 3) Occurrence of Class II end on relation is seen often? 4) Action of reverse pull headgear on maxilla (primary cartilage)
    73. 73. APPLICATION OF THE SERVOSYSTEM THEORY IN CLINICAL ORTHODONTICS POSTURAL HYPERPROPULSOR: • Simulates a more anterior position of the upper dental arch. • A deviation signal is produced which increases LPM and retrodiscal pad activity. TWIN BLOCK: • Alters the occlusal inclined planes. • 70 degree inclined planes alter the sensory engram and provide a horizontal component of force.
    74. 74. APPLICATION OF THE SERVOSYSTEM THEORY IN CLINICAL ORTHODONTICS CLASS II ELASTICS: • Act primarily through the retrodiscal pad rather than the LPM. • Alters the intrinsic regulation of prechondroblast multiplication . • Enhance the rate of hypertrophy of Functional chondroblasts so that the decreased amount of Functional chondroblasts enhance prechondroblast replication. • Similar to the effect of Thyroxine.
    75. 75. APPLICATION OF THE SERVOSYSTEM THEORY IN CLINICAL ORTHODONTICS HERREN(L.S.U.) ACTIVATOR: • Acts when the appliance is not worn. •Action not mediated to through the LPM but through the Retrodiscal pad. • Shortening of the LPM when the appliance is worn when compared to other muscles. • A new sensory engram is produced. • The mandible closes in a more anterior position. •Stimulation of the retrodiscal pad and alteration of intrinsic regulation of the cartilage similar to the Class II elastics.
    76. 76. APPLICATION OF THE SERVOSYSTEM THEORY IN CLINICAL ORTHODONTICS EFFECT OF CHIN CUP THERAPY: • Retropulsion of the mandible results in reduction in the number of dividing cells. • Dividing cells if any are found anteriorly. • Resulting in anterior growth rotation and decreased mandibular length.
    77. 77. CLINICAL VERSUS BIOLOGIC APPROACH INPUT Orthodontic, Functional and Orthopedic appliances to correct disturbances BLACK BOX Genetically determined and cybernetically organized biologic features of phenomena characterizing, inducing or controlling spontaneous and appliance-modulated growth relative primarily of the following: •Maxilla lengthening and widening •Mandible lengthening •Teeth movements OUTPUT Correction of malocclusion and intermaxillary malrelation
    78. 78. CONCLUSION Understanding growth is difficult, yet fruitful to the Orthodontist. A better treatment is rendered by predicting,modifying,correcting or intercepting growth. At times Orthodontist takes advantage of growth. All this is beneficial to the patient which would otherwise cause delay or produce a different outcome.
    79. 79. References • Hand book of facial growth Enlow • Dentofacial orthopedics • Orthodontics; Current principles and Techniques Petrovick Graber& Vanersdall • Hand book of Orthodontics Moyer • Contemporary Orthodontics Proffit •Color atlas of Dental Medicine Orthodontic Diagnosis Rakosi
    80. 80. References • Craniofacial Growth Series – Monograph 23 (Craniofacial Growth Theory and Orthodontic Treatment – Edited by Carlson) •Treatment objectives and case retention: Cybernetic and myometric considerations R.M. Jacobs Am J Orthod, 58:552-564, 1970 •Grant’s Atlas of Anatomy
    81. 81. THANK YOU