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. Why - Since we deal most of the times with treatment of disproportionate jaws, it is necessary to learn how skeletal growth is influenced and controlled.
  3. 3. Scientific revolution – Carlson the representation of changes in normal science wrought by the introduction of new paradigms. Normal science – Kuhn the research findings generally agreed to be basic to a scientific field. Paradigm - the current conceptual frame work of a research field.
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  7. 7. INDEX Relevant terminologies Remodeling theory Genetic concept Sutural dominance hypothesis Scott’s hypothesis Functional matrix hypothesis FMH revisited Van –Limborgh’s concept Petrovics hypothesis Modern Composite
  8. 8. Terminologies Growth site: All surfaces of bones are covered by irregularly arranged growth fields. These can be either resorptive or depository. Growth fields having a special role in the growth of particular bones are C/as growth sites (e.g. mandibular condyle). Growth center: Growth centers are locations where growth takes place independently (mostly genetically controlled). They grow even when transplanted to other areas. They produce a tissue separating force, that facilitates bone deposition until the stretch is relaxed (tension created on the adjacent bones).
  9. 9. All growth centers are growth sites but the reverse is not true.
  10. 10. Remodeling theory Remodeling theory was proposed by Sanstedt (1980). It postulated that all of the craniofacial skeletal growth occurs exclusively by selective addition and resorption of bone.
  11. 11. The scientific basis : Bone grows appositionally at surfaces. Jaw growth characterized by deposition of bone on the posterior surfaces. Calvarial growth by deposition on ectocranial surface and resorption on endocranial surface.
  12. 12. Support Belchier, Duhamel, Hunter performed experiments involving vital dyes and concluded that growth of the maxilla and mandible takes place primarily by means of the addition of bone on their posterior aspects Against Stressed on the nature of bone growth rather than on craniofacial growth
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  14. 14. Genetic concept This concept originated with the advent of classical Mendelian genetics. Later with the blending of data from vertebral paleontology, the neoDarwinian synthesis was created, a currently accepted paradigm of phylogenetic regulation.
  15. 15. Genetic concept stipulates that the genotype supplies all the information required for phenotypic expression. Moss also stated in his thesis that the whole plan of growth, the various operations carried out, the order and site of growth and their co-ordination with other systems are all embossed in the nucleic acid message.
  16. 16. Support Brodie (1940) noted the persistent pattern of facial configuration and assumed it was under tight genetic control. Consistent with the above is the observation that it is possible to predict features of children from cephalometric data of parents. This was also supported by Weinmann and Sicher.
  17. 17. However Moyers maintained that there are primary controls for the initiation and formation of facial structures. Van Limborgh reports after conducting experimental studies on chick embryos that the intrinsic genetic information necessary for the differentiation of cranial cartilages and bone is supplied by neural crest cells. Bony initiation and formation neural crest cells Intrinsic genetic information Bony initiation and formation genes of muscles extrinsic genetic information
  18. 18. Against the highest correlation between parents and progeny is r=0.5 prediction of only 25% of variability “ Not more than 1/4th of the variability of any dimension in children can be explained by considering that dimension in parents. ( R.E.Moyers)
  19. 19. After the general assumptions were found to be flawed it was believed that some parts are genetically controlled while some are not or that certain parts are more controlled by heredity than the others. Later research was focused on identifying the growth sites under the genetic control. The sutures, craniofacial cartilages and periosteum were thought to be under the genetic control and act as growth sites
  20. 20. It was believed that the cartilages were under genetic control but the vault sutures were passive or the brain determined the vault dimensions. This thinking was termed as “Orthodontic Calvinism” by Wendel Wylie
  21. 21. These ideas were contested by Moyers via experiments with Electromyography studies of craniofacial musculature Animal studies carried out in neonatal rats
  22. 22. At the end of all this it is concluded that “ the inheritance of facial dimensions is polygenic” (R.E.Moyers) It is also pointed out that “ it is fallacy that the genome, the totality of DNA molecules, is the main repository for the developmental information i.e. there exists a genetic program or a blueprint theoretically capable of creating an entire organism” (A.J.O. 1995)
  23. 23. Sutural Dominance Theory This theory was proposed by Sicher and supported by Weinmann.
  24. 24. Sicher called it the sutural theory even though he held sutures cartilages periosteum responsible for facial growth and assumed that all these were under tight intrinsic genetic control.
  25. 25. “The primary event in sutural growth is the proliferation of the connective tissue between the two bones. If the sutural connective tissue proliferates, it creates the space for appositional growth at the borders of the two bones”. After his many studies using vital dyes he maintained that sutures have autonomous growth potential Are growth centers Act as independent growth centers
  26. 26. Support Sicher and Weinmann explained that growth of nasomaxillary complex in a downward and forward direction is due to growth at sutures which attach the complex to cranium which are parallel and oblique Sutures: Frontomaxillary Zygomaticomaxillary Zygomaticotemporal Pterygopalatine
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  28. 28. Against 1.Sutures and periosteal tissues are not primary determinants of growth Transplantation studies When the suture was transplanted into a different tissue the suture doesn’t continue to grow as assumed earlier that they had an innate growth potential. Growth at sutures responds to outside influences Microcephaly Hydrocephaly Anencephaly Sutures must be considered areas that react not primary determinants.
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  30. 30. 2. Sicher’s theory that bones are pushed apart by connective tissue growth at the sutures was contested by Babula, Dixon and Smiley. Bone membrane is pressure sensitive Bone-bone push causes compromised blood supply Necrosis of osteogenic membrane Actual stimulus for bone growth is the tension created by functional matrices which are expanding and hence deposition takes place at the sutures which are tension adaptive and responds by bone deposition.
  31. 31. 3. Rumlink (1988) pointed out that all the sutures are not parallel and oblique.
  32. 32. Cartilaginous Dominance Theory Proposed by James Scott an Irish Anatomist
  33. 33. Intrinsic growth controlling factors are present in Cartilage Periosteum And sutures are only secondary and dependent on extrasutural influence
  34. 34. Cartilaginous parts of skull are responsible for cranial growth Nasal septum a major contributor in maxillary growth Condyle determines growth of the mandible Cranium Nasomaxillary Cranial base Synchondroses Nasal septum Complex Mandible Condyle Pacemakers/ Growth Centers
  35. 35. In case of the mandible this can be explained by visualizing it as the diaphysis of a long bone bent into a horse shoe shape with the epiphysis removed, so that there is cartilage representing half an epiphyseal plate at the ends representing the mandibular condyles.
  36. 36. Support Pressure and tension have little effect on cartilaginous growth. On the contrary, intramembranous bone is immediately responsive. Hunter and Enlow – growth equivalent theory relatively lesser response of the endochondral cranial base as opposed to immediate response of the intramembranous cranial vault to external influences Experimental research on rats by Ohyama removal of cartilage produces significant effect on growth. Also supported by research of Sarnat, Burdi, Baume, Petrovic et al
  37. 37. Expt. by Sarnat, Burdi, Baume and Petrovic
  38. 38. Achondroplasia Cebocephaly Henrichson’s research on palatal splitting Midface deficiency Severe Midface def. Largely adjusted and adaptive compensatory reaction of sutural connective tissue and immediate and sensitive response of membranous bone to tensional forces
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  40. 40. Against Two studies were carried out by Gilhus-Moe and Lund in Scandinavia in 1960’s showed that there are excellent chances that condylar process would regenerate to approx. its original size after trauma In a few there was even a overgrowth of condyle. In a few children there is a reduction in growth after injury maybe due to the trauma to the soft tissues / scarring Therefore Scott’s hypothesis does not hold true completely.
  41. 41. Experiments Transplantation: Not all skeletal cartilages act the same when transplanted Epiphyseal cartilage Synchondroses independent growth centers Nasal septum less independent growth potential Mandibular condyle little or none
  42. 42. Evaluation of effect of removal of cartilage on growth: The impact on a growing rabbit of removing a segment of cartilage is a deficit in midface growth Setback The surgery itself Accompanying interference with blood supply
  43. 43. Inference from these experiments Except the mandibular condyle all other cartilages act as growth centers
  44. 44. Functional Matrix Theory Melvin Moss based on original concept of Van Der Klaaus. (1969)
  45. 45. Succintly stated the theory is as follows: “There is no direct genetic influence on the size and shape, or position of skeletal tissues, only the initiation of ossification. All genetic skeletogenic activity is primarily dependent upon the embryonic functional matrices”
  46. 46. Concept Circumstances appropriate Environmental influence DNA of bone cells set into motion Genetic influence ossification Effect Tissues and functions Differentiation
  47. 47. Functional Cranial Component One function Skeletal tissue Neural tissue Muscle tissue Functional Cranial Component Vascular tissue
  48. 48. Functional Cranial Component Tissues and spaces that completely perform a function A related skeletal unit that acts biomechanically to protect and/or support its functional matrix Functional matrix Skeletal cranial component
  49. 49. Periosteal Matrix Relates the matrix to those tissues that influence the bone directly through the periosteum Muscles Blood vessels and nerves lying in grooves or entering or exiting through foramina Affects a microskeletal unit, sphere of influence is usually limited to a part of one bone Temporalis – coronoid process Tooth - alveolar bone
  50. 50. Capsular Matrix Included in this matrix are those masses and spaces that are surrounded by capsules. Neural mass with scalp and dura. Orbital mass with supporting tissues of the eyes. Capsules tend to influence macroskeletal units which means portions of several bones are simultaneously affected Inner surface of calvarium. This sharing of reaction by several adjacent bones constitutes a macroskeletal unit.
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  52. 52. Moss contends, then, that all loci of new bone formation Sutures Periosteum Spheno-occipital synchondrosis Nasal cartilage Condyles are all growth sites and not growth centers. None of these sites contains genetic information that can determine their ultimate form; they are at the disposal of the functional matrices related to them.
  53. 53. Support Anencephaly Microcephaly Hydrocephaly Normal growth manifested by patients from whom the condyles have been removed due to trauma pathology Experimental studies with cast gold bite planes contd.
  54. 54. Natural translation Growth site Cartilage cells have genetic information that enables them to be responsive to pressure only Experimental displacement Capacity to determine its own size FUNCTIONAL MATRIX
  55. 55. Against Spheno-occipital synchondrosis Demonstrates autonomous growth Nasal cartilage Scott- midfacial growth not responsive to external influence Removal - deficient growth Destruction of cell proliferation potential without cicatrization – Deficient growth Craniostenosis – premature stenosis of sutures inhibits growth – sutures have some capacity to regulate the activity of functional matrix
  56. 56. Clinical applications of Moss’s theory
  57. 57. Clinical practices that reflect functional matrix modification Enucleated orbit. Widening midpalatal sutures Repositioning of maxillary segments of cleft patients Bilateral condylectomy Oblique bite planes Monobloc functional therapy
  58. 58. Van Limborgh’s Compromise theory Three major viewpoints considered: Sicher’s Scott’s Moss’s
  59. 59. New concepts Anatomic Division Factors that control Growth
  60. 60. Anatomic Division Endochondral ossification Chondrocranium Cartilaginous base Desmocranium Intramembranous ossification Calvarium Nasal capsule Middle face Otic capsule Mandible
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  62. 62. Sicher’s view Cartilage Sutures Periosteum Are all growth centers
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  64. 64. Scott postulates Intrinsic genetic factors affect Cartilage Periosteum while sutures are passive n reactory.
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  66. 66. Moss is felt to have erred in denying any intrinsic genetic factors in the control of chondrocranial growth and… restricting the control of sutural growth to local epigenetic and environmental factors.
  67. 67. Fails because Microcephaly and Hydrocephaly Orbital response Primordia of eye can be manipulated Eye enucleation without replacement ceases expansion contd.
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  69. 69. Van Limborg’s Compromise Chondrocranial growth is controlled by intrinsic genetic factors Desmocranial growth is controlled mainly by local epigenetic factors Desmocranial factors is also controlled by local environmental factors General epigenetic and general environmental factors have very little role to play.
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  71. 71. Independence of skull growth cannot be consistently demonstrated
  72. 72. Modern Composite Because Van Limborgh used a few terms to describe embryologic entities that are novel, and he fails to classify the controlling factors for the mandible a ‘Modern Composite’ of craniofacial growth is offered by Ranly
  73. 73. Embryologic Classification Desmocranium Cranial vault Middle face Splanchnocranium Mandible Spheno-occipital syn. Chondrocranium Nasal cartilage
  74. 74. Modern Composite
  75. 75. Thank you For more details please visit