Terminologies and basic concepts of growth and development /certified fixed orthodontic courses by Indian dental academy


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Terminologies and basic concepts of growth and development /certified fixed orthodontic courses by Indian dental academy

  1. 1. TERMINOLOGIES AND BASIC CONCEPTS OF GROWTH AND DEVELOPMENT. INDIAN DENTAL ACADEMY Leader in continuing dental education www.indiandentalacademy.com www.indiandentalacademy.com 1
  2. 2. “Growth was conceived by an anatomist, born to a biologist, delivered by a physician, left on a chemist’s door step and adopted by a physiologist. At an early age she eloped with a statistician, divorced him for a psychologist and is now being wooed, alternately and concurrently, by an endocrinologist, a pediatrician, a physical anthropologist, an educationalist, a biochemist, a physicist, a mathematician, an orthodontist, a eugenicist and the children’s bureau!” www.indiandentalacademy.com 2
  3. 3. INTRODUCTION Knowledge about normal growth and how it occurs is essential so that one can distinguish any deviation. To know about the timing of growth so that one can “Work with growth”. www.indiandentalacademy.com 3
  4. 4. Growth and development are closely related but not synonymous. What is growth? “Growth” is a general term implying simply that something changes in magnitude. How and what actually happens is explained by a more descriptive term development. www.indiandentalacademy.com 4
  5. 5.  “Growth refers to increase in size” Todd  “Growth may be defined as the normal change in the amount of living substance”Moyers  “Growth usually refers to an increase in size and number” – Proffit www.indiandentalacademy.com 5
  6. 6.    “Change in any morphological parameter which is measurable”- Moss. “Size development , progressive development (i.e, evolution, emergence, increase or expansion)”- Webster’s dictionary. “Self multiplication of living substance”J.S.Huxley. www.indiandentalacademy.com 6
  7. 7. Development Development= Growth + Differentiation: change from generalized cells/tissues + to more specialized kind Translocation: change in position www.indiandentalacademy.com 7
  8. 8. Development is a progress towards maturity” – Todd “Development refers to all naturally occurring progressive, unidirectional, sequential changes in the life of an individual from it’s existence as a single cell to it’s elaboration as a multifunctional unit terminating in death” – Moyers “Development connotes a maturational process involving progressive differentiation at the cellular and tissue levels” – Enlow www.indiandentalacademy.com 8
  9. 9. Major themes of development     Changing complexity Shifts from competent to fixation Shifts from dependent to independent Ubiquity of genetic control modulated by environment www.indiandentalacademy.com 9
  10. 10. Changing complexity    Takes place at all level of organization from the sub-cellular to the whole organism Normally complexity increases with development . Most complex period of developing dentition is transition of dentitions. www.indiandentalacademy.com 10
  11. 11. Shifts from competent to fixation  Undifferentiated cells once differentiated become fixed. Shifts from dependent to independent  Development brings greater independence at most levels of organization. www.indiandentalacademy.com 11
  12. 12. Ubiquity of genetic control modulated by environment  Genetic control of development is constantly being modified by environmental interactions www.indiandentalacademy.com 12
  13. 13. Correlation between growth and development Growth is largely an anatomic phenomenon and quantitative in nature. Development is a physiologic and behavioral phenomenon and qualitative in nature. The two processes rely on each other and under the influence of the morphogenetic pattern, “the three fold process”- self multiplication, differentiation, organization growth and development occurs, time being the fourth www.indiandentalacademy.com 13 dimension.
  14. 14. Morphogenesis – “A biologic process having an underlying control at the cellular and tissue levels.” Control process intervened at the right time and stage-augments, overpowers, replaces activities . Rate, timing, direction and magnitude are altered. Morphogenesis works towards a state of balance among all growing parts. www.indiandentalacademy.com 14
  15. 15. www.indiandentalacademy.com 15
  16. 16. Important concepts in growth and development    Pattern -Differential growth -Predictability Variability -Concept of normality -Age equivalence Timing www.indiandentalacademy.com 16
  17. 17. PATTERN   Pattern represents proportionality-not just proportional relationships at a point in time but change in these relationships over time. Can be defined as-a set of constraints operating to preserve the integration of parts under varying conditions or through time. www.indiandentalacademy.com 17
  18. 18. Cephalocaudal gradient of growth www.indiandentalacademy.com 18
  19. 19.   The accomplishment of normal human proportions is not merely due to a general slowing down. Different tissues grow at different rates at different times. The overall pattern of growth is a reflection of the growth of the various tissues making up the organism. www.indiandentalacademy.com 19
  20. 20. Differential growth   Scammon’s curves for growth. Gave a graph for four major tissues of the body. -lymphoid -neural -general -genital www.indiandentalacademy.com 20
  21. 21. Body Composition Changes with Age STRUCTURE FETUS NEW BORN ADULT Skin & fat 16 % 26 % 25 % Viscera 16 % 16 % 11 % Nervous system Muscle 21 % 15 % 03 % 25 % 25 % 43 % Skeleton 22 % 18 % 18 % www.indiandentalacademy.com 21
  22. 22. Predictability   Predictability of growth pattern is a specific kind of proportionality that exists at a particular time and progresses towards another, at the next time frame with slight variations. Any change in growth pattern would indicate some alterations in the expected changes in body proportions. www.indiandentalacademy.com 22
  23. 23. Variability  No two individuals with the exception of monozygotic twins are alike.  Clinically important to identify if an individual is at the extreme of normal variation or is outside the range.  What is normal? www.indiandentalacademy.com 23
  24. 24. Normality   Normality refers to that which is usually expected, is ordinarily seen or typical – Moyers Normality may not necessarily be ideal so rather than categorizing as normal or abnormal one can think of deviations from the normal pattern. www.indiandentalacademy.com 24
  25. 25.  One way to evaluate normality is using growth charts.  Used to determine if growth is normal in 2 ways- - location of the individual relative to the group. - follow a child’s growth to evaluate any unexpected changes. www.indiandentalacademy.com 25
  26. 26. www.indiandentalacademy.com 26
  27. 27. Age equivalence  Because of variability all individual at a given chronological age are neither of the same size or same stage of maturation.  It is better to compare biologic development.  “Developmental ages” –skeletal age and dental age are used. www.indiandentalacademy.com 27
  28. 28. Timing    One of the factors for variability in growth. Timing variations arise because biologic clock of different individuals is set differently. Timing-largely genetically controlled. -sex related differences -physical differences -environmental www.indiandentalacademy.com 28
  29. 29.  Variation in growth and development because of timing are evident in human adolescence.  Plotting change in weight or height shows the pattern of growth.  The distance and velocity graphs can be plotted and compared. www.indiandentalacademy.com 29
  30. 30.   Growth effects due to timing variation demonstrated using growth velocity curves. Time variability is reduced if graph plotted using developmental age. www.indiandentalacademy.com 30
  31. 31. Growth spurts    Periods of sudden acceleration of growth. Due to physiological alteration in hormonal secretion. Timing-sex linked. Normal spurts are  Infantile spurt – at 3 years age  Juvenile spurt – 7-8 years (females); 8-10 years (males)  Pubertal spurt – 10-11 years(females); 15- www.indiandentalacademy.com 18 years (males) 31
  32. 32. www.indiandentalacademy.com 32
  33. 33.  Pubertal growth spurt:  Important period for orthodontic treatment.  Initiated in the brain-secretion of releasing factors, pituitary gonadotropins.  Sex hormones released-physiological changes occur-classic growth cure pattern.  Timing -2 years earlier in girls.  Affected by genetic and environmental factors. www.indiandentalacademy.com 33
  34. 34. GIRLS Total development of adolescent growth- 3½yrs Stage 1 Beginning of adolescent growth Appearance of breast buds, initial pubic hair Stage 2 Noticeable breast development, axillary hair, dark/more abundant pubic hair. (12 months later) Peak velocity in height. Stage 3 (12-18 months later) Growth spurt ending. Menses, broadening of hips with adult fat distribution, breasts completed www.indiandentalacademy.com 34
  35. 35. BOYS Total development of adolescent growth- 5 yrs Stage 1 Beginning of adolescent growth Stage 2 (12 months later) Fat spurt, weight gain, feminine fat distribution Redistribution or reduction in fat, pubic hair, growth of penis Height spurt beginning Stage 3 (8-12 months later) Peak velocity of height. Stage 4 (15-24 months later) Growth spurt ending Facial hair appears on upper lip only, axillary hair, muscular growth with, harder/more angular body form Facial hair on chin and lip, adult distribution/colour of pubic and axillary hair, adult body form. www.indiandentalacademy.com 35
  36. 36. Velocity curves in for growth at adolescence shows difference in timing between boys and girls. www.indiandentalacademy.com 36
  37. 37.  Growth of the jaws correlates with physiologic events of puberty –same as height. www.indiandentalacademy.com 37
  38. 38.    But correlation is not perfect –juvenile acceleration of jaw growth occurs. Sex hormones are produced in adrenals by 6 years- ‘adrenarche’. More prominent in girls due to greater adrenal component. www.indiandentalacademy.com 38
  39. 39.  Important clinically-careful assessment of physiologic age-plan orthodontic treatment.  Treatment must begin during  mixed dentition-for girls.  Near completion of permanent dentition-for boys-Proffit.  But according to Graber, boys have a greater tendency for 3 peaks than girls-very few girls show the mixed dentition growth spurt. www.indiandentalacademy.com 39
  40. 40. Nature of skeletal growth  At cellular level there are three mechanisms for growth. –Hyperplasia –Hypertrophy –Secretion of extracellular matter www.indiandentalacademy.com 40
  41. 41. Mechanism of growth in soft tissues  In soft tissues growth occurs mainly by a combination of two mechanisms namely: Hyperplasia-increase in the number of parenchymal cells. Hypertrophy-increase in size of parenchymal cells. Secretion of extracellular material also contributes to growth-but different from hard tissue growth as it does not mineralize. www.indiandentalacademy.com 41
  42. 42.    Hyperplasia is the main mechanism hypertrophy occurring secondarily. Interstitial growth-growth occurring at all points in a tissue. Also occurs in uncalcified cartilage.  Abnormalities in soft tissue growth-  Metaplasia  Dysplasia -disordered cellular development. www.indiandentalacademy.com 42
  43. 43. Mechanism of hard tissue growth    Two mechanisms Endochondral bone formation: Process of converting cartilage into bone Intramembranous bone formation: Process of bone formation from undifferentiated mesenchymal tissue. www.indiandentalacademy.com 43
  44. 44. Endochondral bone growth  Chondrogenesis- starts around 2-18 weeks. -Thin plate of cartilage extends from nasal cavity to foramen magnum. -4th month in-utero ingrowth of vascular elementscenters of ossification appear. -occurs till the rate of mineralization exceeds the rate of proliferation -Growth cartilages appear where linear growth of bone towards the force area occurs. www.indiandentalacademy.com 44
  45. 45. www.indiandentalacademy.com 45
  46. 46. Primary cartilage-local factors do not influence as there is a cartilagenous matrix-spheno-occipital synchondrosis, nasal septal cartilage. Secondary cartilage-local factors modulate growthcondylar and coronoid cartilage. www.indiandentalacademy.com 46
  47. 47. Comparison of physiologic properties of bone and cartilage        Characteristic cartilage Calcification Non calcified Vascularity Avascular Surface membrane Nonessential Pressure resistance Tolerant Rigidity Flexible Modes of growth Interstitial and appositional www.indiandentalacademy.com bone Calcified Vascular Essential Sensitive Inflexible Appositional 47
  48. 48.          Endochondral bone growth occurs in areas of increased compression It does not form directly from cartilage but replaces it. Steps in bone formation: Hypertrophy of chondrocytes and matrix calcifies Cells degenerate Invasion of blood vessels and connective tissue cells. Osteoblasts differentiate and produce osteoid tissue. Osteogenic tissues replace degenerating cartilage. osteoblastic tissue calcifies. www.indiandentalacademy.com 48
  49. 49. www.indiandentalacademy.com 49
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  51. 51. www.indiandentalacademy.com 51
  52. 52. Intramembranous bone growth     Occurs in areas of tension. The membranes have their own internal deposition and remodeling mechanism. Formed entirely by apposition of new bone to free surfaces. Any change is through resorption and apposition. Seen in areas like  Cranial vault  Maxilla  Mandible except condylar cartilage www.indiandentalacademy.com 52
  53. 53. Steps in intramembraneous bone growth         Undifferentiated connective tissue undergoes series of changes. Some cells develop into osteoblasts. Osteoblasts produce osteoid tissue. Cells and blood vessels are encased. Osteocytes are formed Osteoid tissue continues to be produced by membrane cells. Osteoid calcifies. Essential membrane covers bone. www.indiandentalacademy.com 53
  54. 54. www.indiandentalacademy.com 54
  55. 55. Bone metabolism     Biomechanical response to altered function and applied loads depends on the metabolic status of the patient. Biomechanical manipulation of bone is the physiologic basis of orthodontics. 99% of calcium is stored in the skeleton. Endocrine, biomechanical and cell level control factors maintain serum calcium at 10mg/dl www.indiandentalacademy.com 55
  56. 56. Calcium homeostasis  Orthodontics is bone manipulative therapy-favorable calcium metabolism is important. www.indiandentalacademy.com 56
  57. 57.  Calcium homeostasis is supported by 3 mechanisms :  Rapid instantaneous flux of calcium from bonefluid (seconds) by selective transfer of calcium ions into and out of bone fluid-PTH and vit D  Short term control of serum calcium levels affects rates of bone formation and resorptionPTH,1,25 DHCC and calcitonin. www.indiandentalacademy.com 57
  58. 58.  Long term regulation of metabolism have effects on skeleton. Clinical correlation is the high bone remodeling rate seen at the interface of a titanium implant used for anchorage in adults. www.indiandentalacademy.com 58
  59. 59. Types of Bones      Woven bone – The first bone formed in response to orthodontic loading usually is the woven type. It is weak, disorganized, and poorly mineralized Lamellar bone – a strong, highly organized, wellmineralized tissue. Makes up 99% of adult human skeleton. secondary mineralization takes 1 year. Full strength of bone not achieved till a year after orthodontic treatment. www.indiandentalacademy.com 59
  60. 60.     Composite bone – is an osseous tissue formed by the deposition of lamellar bone within a woven bone lattice, a process called Cancellous compaction. This is the quickest means of producing relatively strong bone. Important type in physiologic response to orthodontic loading. Bundle bone - is a functional adaptation of lamellar structure to allow attachment of tendons and ligaments’ Sharpey’s fibers. www.indiandentalacademy.com 60
  61. 61. www.indiandentalacademy.com 61
  63. 63. Mechanisms of Bone Growth and Growth Movements.      Remodeling. -Cortical drift. Displacement . Combination of remodeling and displacement. Modeling. Rotation. www.indiandentalacademy.com 63
  64. 64. Remodeling   It is a differential growth activity involving deposition at one end and resorption at the other. It is a basic part of growth process. www.indiandentalacademy.com 64
  65. 65. Functions of Remodeling 1. 2. 3. Sequentially relocate each component of the whole bone Progressively change the shape of the bone to accommodate its various functions Progressively change the size of whole bone www.indiandentalacademy.com 65
  66. 66. 4. Progressive fine tune fitting of all the separate bones to each other and to their contiguous growing, functioning soft tissues . 5. Carry out continuous structural adjustments to adapt to the intrinsic and extrinsic changes in conditions. www.indiandentalacademy.com 66
  67. 67.  Natural perception of growth-  But a generalized growth does not occurRemodeling in specific areas causes change in shape and size. www.indiandentalacademy.com 67
  68. 68. Deposition and Resorption •Bone produced by covering membrane-periosteal bone comprises about half of the cortical bone tissue. Bone laid down by the lining membraneendosteal bone makes up the other half. •Rotations occur if the rates of deposition and resorptions are unequal. www.indiandentalacademy.com 68
  69. 69.  Cortical drift. Drift •It occurs during remodeling, resulting in movement of bone towards the depository surface. Vertical drift- - Helps to anatomically place teeth as maxilla and mandible enlarge. - This vertical positioning of teeth is in addition to eruption and not part of it. www.indiandentalacademy.com 69
  70. 70. Enlow’s “V” principle   Most useful and basic concept in facial growth as many facial and cranial bones have a Vshaped configuration. Bone deposition(+) occurs on the inner side and resorption (-) occurs on the outer surface. www.indiandentalacademy.com 70
  71. 71. The direction of movement is towards the wide end of ‘v’. Simultaneous growth movement and enlargement occurs. Conversion of a more wider part to a narrower one. www.indiandentalacademy.com 71
  72. 72. Example with V oriented vertically and horizontally  When bone added on lingual side of coronoid process, growth proceeds and this part of the ramus increases in vertical dimension. Same deposits of bone also bring about a posterior direction of growth movement. This produces a backward movement of coronoid processes even though deposit is on the lingual side. www.indiandentalacademy.com 72
  73. 73. ‘V’ principle applied to the mandible causes increase in both posterior and superior directions. Causes an increase in the transverse dimension of the maxilla .Increases the airway space. www.indiandentalacademy.com 73
  74. 74. Transverse histologic section of bone: A. Periosteal surface reorptive, endosteal surface depository. B. New endosteal bone added on inner surface. C. Endosteal layer produced covered by periosteal layer following outward reversal. D. Cortex made entirely of periosteal bone. outer surface depository and inner surface resorptive. www.indiandentalacademy.com 74
  75. 75. Types of remodeling. 4 types1.Biochemical remodeling-molecular levelmaintains calcium levels. 2.Secondary reconstruction of bone-by Haversian systems and rebuilding of cancellous bone. 3.Pathologic remodeling-occurs after disease or trauma. 4.Growth remodeling  www.indiandentalacademy.com 75
  76. 76. Displacement     Displacement is a physical movement of the whole bone as it remodels. Occurs in conjunction with remodeling where joints are present. Articulations are areas ‘away’ from which the displacement movements occur as the bone enlarges. Amount of enlargement equals extent of displacement. www.indiandentalacademy.com 76
  77. 77. www.indiandentalacademy.com 77
  78. 78.    There are 2 types of displacement. Primary displacement-the process of physical carry takes place in conjunction with bone’s own enlargement. The amount of displacement exactly equals amount of new bone deposition. www.indiandentalacademy.com 78
  79. 79.   Secondary displacement-movement of bone occurring due to growth elsewhere. E.g.-growth of the middle cranial fossa and the temporal lobes secondarily displaces the nasomaxillary complex anteriorly and inferiorly. www.indiandentalacademy.com 79
  80. 80.  “Domino effect”growth changes can be passed on from region to region having effect at a distant site. www.indiandentalacademy.com 80
  81. 81. Combination of remodeling and displacement.   Multidirectional growth movements involve remodeling ,primary and secondary displacement. Comparable results can be produced by different combinations. www.indiandentalacademy.com 81
  82. 82. As the bone remodels, though the outer surface is resorptive it is being carried forward by primary and secondary displacement. www.indiandentalacademy.com 82
  83. 83. Principle of ‘Area relocation’ Both remodeling and displacement together cause a shift in the existing position of a particular structures with reference to another. www.indiandentalacademy.com 83
  84. 84. Translation and Transformation www.indiandentalacademy.com 84
  85. 85. Modeling    According to Roberts et almodeling and remodeling are 2 distinct phenomena. In bone modeling independent sites of resorption and formation change the form (shape, size or both) of a bone. Bone remodeling is a specific, coupled sequence of resorption and formation occurring to replace previously existing bone. www.indiandentalacademy.com 85
  86. 86.     Bone modeling is the dominant process of facial growth and adaptation to applied loads such as headgears, rapid palatal expansion, and functional appliances. Modeling changes can be seen on cephalometric tracings. Remodeling changes are apparent only at microscopic level. The mechanism for internal remodeling of dense compact bone is through axially oriented cutting and filling cones. www.indiandentalacademy.com 86
  87. 87. Cutting and filling cones www.indiandentalacademy.com 87
  88. 88. Frost’s Mechanostat Theory.  This concept is based on a idea that bone adaptive response is modulated by mechanical environment with several different mechanical usage windows. www.indiandentalacademy.com 88
  89. 89. Controlling factors for modeling  Mechanical Peak load in µE 1. Disuse atrophy <200. 2. Bone Maintenance 200—2500. 3. Physiological Hypertrophy 2500—4000. 4. Pathological Overload >4000. Endocrine. 1.Bone metabolic hormones-PTH,Vit D,Calcitonin. 2.Growth Hormones-Somatotropin,IGF -1,IGF -2. 3.Sex steroids-Testosterone, Estrogen. www.indiandentalacademy.com 89
  90. 90.  Paracrine and Autocrine-wide varity of local agents. Control factors for bone remodeling.  Metabolic a. PTH-increases activation frequency. b. Estrogen- decreases activation frequency.  Mechnical a.<1000 µE, more remodeling b. >2000 µE, less remodeling  www.indiandentalacademy.com 90
  91. 91. Counter part principle  Growth of any given facial or cranial part relates specifically to other structural and geometric counterparts in the face and cranium” - Enlow www.indiandentalacademy.com 91
  92. 92. Growth equivalent principle This principle proposed by Hunter & Enlow relates the effects of cranial base growth on the facial bone Growth. www.indiandentalacademy.com 92
  93. 93. www.indiandentalacademy.com 93
  94. 94. Growth rotation   Phrase introduced by Bjork in 1955. 2 basic categories of rotations-Remodeling rotations. - www.indiandentalacademy.com 94
  95. 95. Displacement rotations. Whole nasomaxillary complex rotates clockwise or counterclockwise depending on the activities of the overlying basicranium.  Mandible also rotates in accordance to the nasomaxillary positions.  Adjustive remodeling rotations is simultaneously occurring.  www.indiandentalacademy.com 95
  96. 96. Growth Fields    Inside and outside of every bone are covered by an mosaic like pattern of ‘growth fields’. Both depository and resorptive surfaces are present-if a given periosteal area is resorptive then the opposite endosteal surface will be depository. These combinations produce the characteristic drift. www.indiandentalacademy.com 96
  97. 97.    The irregularity is a response to the varied functions imposed on the bone by various attachments. The operation of the growth fields is carried out by membranes surrounding the hard tissue. The various depository and resorptive fields do not have the same rate of activity. www.indiandentalacademy.com 97
  98. 98.   The growth movement of the bone follows the pace setting movement of the overall growth field. Important to understand the plan of distribution of the major growth fields as these patterns can show us if we are working with or against growth. www.indiandentalacademy.com 98
  99. 99.   Ex. Distalization of maxillary molars putting them into a depository field or labial placement of lower anteriors into a resorptive field. Variations in the facial structure can be due to a change in-Pattern of the fields. -Placement of the boundaries. -Rates and amounts of deposition and resorption. -Timing of growth activity among different fields. www.indiandentalacademy.com 99
  100. 100. Growth Site and Growth Center    A site of growth is merely a location where growth occurs. Center is a location where independent growth occurs. All centers of growth are also sites, but the reverse is not true. www.indiandentalacademy.com 100
  101. 101. Growth sites  Growth fields having special role in the growth of the particular bone are called growth sites . www.indiandentalacademy.com 101
  102. 102. E.g. mandibular condyle, maxillary tuberosity, synchondrosis of the basicranium, sutures and the alveolar process.   Such special sites do not carry out the entire growth process for the particular bone associated with them. All other surfaces also actively participate. www.indiandentalacademy.com 102
  103. 103. Growth Center  Force, energy or motor for a bone resides primarily within its growth centre.  According to Baume it can be described as ‘Places of endochondral ossification with tissue separation force’. www.indiandentalacademy.com 103
  104. 104.   This concept especially when applied to the craniofacial region is not completely accepted. Mandibular condyle and synchondroses of the cranial base are still controversial. www.indiandentalacademy.com 104
  105. 105. GROWTH STUDIES AND METHODS OF STUDYING GROWTH.  Types of growth data.  Methods of gathering growth data.  Longitudinal growth studies.  Methods of studying bone growth. www.indiandentalacademy.com 105
  106. 106. Types of growth data.  Opinion  Observations.  Ratings and rankings.  Quantitative measurements.  direct data.  indirect data.  derived data. www.indiandentalacademy.com 106
  107. 107.    Opinion . Not based on no quantitative data. They are the crudest form of scientific knowledge.  Observations: They are useful for studying all or none phenomenon .They are used in a limited way when more quantitative data is available. E.g. congenital absence of teeth. www.indiandentalacademy.com 107
  108. 108.     Ratings and rankings: Certain data is difficult to quantify and thus may be compared to conventional rating scale . Ratings make use of comparisons with such scales. Rankings array data in ordered sequence according to value. www.indiandentalacademy.com 108
  109. 109.      Quantitative measurements: Includes expressing an idea or fact as a meaningful quantity or numbers. Direct data: Derived from measurements taken on living persons or cadaver with a measuring device. Indirect data: Derived from measurements taken from images or reproductions of the actual person. Derived data: Obtained by comparing at least two other measurements. www.indiandentalacademy.com 109
  110. 110. Methods of gathering growth data.  Longitudinal studies .  Cross sectional studies.  Overlapping or semi longitudinal studies. www.indiandentalacademy.com 110
  111. 111. Longitudinal studies        These are measurements made of the same person or group at regular intervals through time. Advantages : Variability in development within a group is put in proper perspective Serial comparison makes study of specific developmental pattern of individual possible. Temporary temporal problems in sampling are smoothed with time. Disadvantages : Time consuming, expensive, sample loss or attrition, averaging. www.indiandentalacademy.com 111
  112. 112. Cross sectional studies.       These are measurements made of different samples or different individuals and studied at different periods. Advantages: Quicker, less expensive, statistical treatment of data is easier. Studies can be readily repeated. Method can be used in archeological data. Disadvantages :It must be assumed that groups being measured and compared are similar. Cross sectional group averages tend to obscure www.indiandentalacademy.com 112 individual variations-Esp. timing variation.
  113. 113. Semi longitudinal studies  Longitudinal and cross sectional studies can be combined to seek the advantages of both.  In this way one might compress 15 years of study into 3 years of gathering growth data.  Each sub sample including children studied for same number of years but started at different ages. www.indiandentalacademy.com 113
  114. 114. Evaluation of growth data.   Working knowledge of statistics is very important. Cephalometrics -Developed and used in order to study growth-day to day use in research and practice best way to evaluate growth. www.indiandentalacademy.com 114
  115. 115. LONGITUDINAL GROWTH STUDIES. Bolton brush growth study. Burlington growth study. Michigan growth study. Denver child growth study. Iowa child welfare study. Forsyth twin study. Meharry growth study. www.indiandentalacademy.com 115
  116. 116.        Montreal growth study Krogman Philadelphia growth study Fels growth study Implant studies The Mathews implant collection The Hixon Oregon implant study Cleft palate study www.indiandentalacademy.com 116
  117. 117. Bolton Brush growth study.     The Brush enquiry was initiated in 1926 by Prof. T. Wingate Todd with a aim of studying skeletal development . The Bolton study was initiated concurrently by Dr. Holly Broadbent Sr. in 1929,which focused on normal development of facial skeleton and dentition. Sample size:5000 normal healthy children. Records: Series of x-rays, casts, dental and medical examination and psychological tests. www.indiandentalacademy.com 117
  118. 118.    The two collections merged officially in 1970. In 1975 the Bolton standards of dentofacial developmental growth were published by Dr Holly Broadbent jr. These standards are a series of averages that represent optimum facial and developmental growth and form a baseline for understanding and assessing craniofacial growth. www.indiandentalacademy.com 118
  119. 119. Burlington growth study    The aim of the study was to learn more about malocclusion, evaluate preventive and interceptive orthodontic treatment, and obtain a set of growth records as a database for future studies. Sample Size:1632 subjects followed longitudinally. Records :Series of x-rays, casts, photographs, height and weight records and medical examination. www.indiandentalacademy.com 119
  120. 120.     The original concept for the study was presented by Robert Moyers& the records were gathered under Frank Popovich. More than 247 investigations &322 studies are based on this growth study. Longitudinal studies by Thompson & Popovich to derive cephalometric norms of a representative sample was based on 210 children followed for 15 years at the Burlington growth center. Age, sex and growth type specific craniofacial templates were derived and static and dynamic analysis were proposed on the basis of this study. www.indiandentalacademy.com 120
  121. 121. TWIN STUDIES Forsyth twin study-414 pairs. BASED ON ORIGIN CLEFT PALATE Implant STUDIES studies. Denver growth Lancaster PA The study. Hospital for sick Mathews children-Toronto implant Michigan collectionstudy. Center for 36 craniofacial Iowa study. Childrenanomalies Fels studyBjork type. -Chicago European  The Krogman population Meharry study- The Krogman The Hixon Philadelphia Philadelphia Oregon African growth studygrowth study implant American. mixed study-270 subsample with subjects, www.indiandentalacademy.com 121 410 pairs of Bjork type
  122. 122. IMPORTANCE OF GROWTH STUDIES.    Norms for normal growth. When a new study is taken up, the results of the previous studies can be used as control. Teleradiology Universal method of storing and transporting digital images that can be read between locations. www.indiandentalacademy.com 122
  123. 123. Methods of studying bone growth Experimental approaches Measurement approaches - Craniometry - Anthropometry -Comparitive anatomy - Cephalometry Microscopic Macroscopic -Implants -Mineralized sections -Polarized light -Finite Element -Fluorescent labels Modeling -Microradigraphy -Autoradiography -Microelctrodes -Nuclear volume morphometry -Natural markers www.indiandentalacademy.com 123
  124. 124.     CRANIOMETRY. Involves measurements of skull found among human skeletal remains. It was originally used to study the Neanderthal and Cro-Magnon skull. It can give information of extinct population and pattern of growth . Advantages: Precise measurements can be made. Disadvantages: All growth data is cross - sectional. www.indiandentalacademy.com 124
  125. 125.    ANTHROPOMETRY :Includes measurements using soft tissue points overlying bony landmarks in living individuals. It can also be done on dried skulls but variation in soft tissue thickness would produce different results. Possible to follow the growth of an individual directly by making the same measurements repeatedly at different times , thus producing longitudinal data. www.indiandentalacademy.com 125
  126. 126. Comparative anatomy:    Basic principles common to growth in all species are first recognized and defined by studies in comparative anatomy. Comparisons with such species can lend significant contributions to our knowledge about human facial growth. Information about phylogeny of the anatomic components comprising the head has been derived from comparative studies of fossils and present www.indiandentalacademy.com day species. 126
  127. 127.  CEPHALOMETRIC RADIOGRAPHY:   Combines the advantages of cephalometry and craniometry. It allows direct measurement of bony skeletal dimensions and also allows the same individual to be followed over time. Disadvantages: Depends upon precise orientation of head before taking radiographs. Requires precise control of magnification  Since it is a 2D representation of 3D structure all www.indiandentalacademy.com measurements are not possible. 127
  128. 128.     Measurement data can be represented in different ways Graphs can be plotted –velocity and distance curves. Based on increase in number and weight. To interpret the data the mode of mathematical transformation should be known. www.indiandentalacademy.com 128
  129. 129. Mineralized sections     Fully mineralized sections are superior to demineralized specimens as there is less processing distortions and both organic and inorganic matrix can be studied simultaneously. Cellular details and resolutions can be enhanced by reducing the thickness of the sections. Specific stains can be used to enhance both cellular and extra cellular details. Thin sections can however quench more rapidly. www.indiandentalacademy.com 129
  130. 130. Polarized light.      The lamellar fringe pattern of the bone revealed with polarized light indicates the orientation of collagen fibers within the bone matrix. Most lamellar bone has alternating layers of collagen fibers oriented at right angles. However 2 other configurations can also be noted: Longitudinally aligned-Resist tension. Transverse / circumferential fibers supporting compression. www.indiandentalacademy.com 130
  131. 131.   Loading condition at the time of bone formation dictate the orientation of collagen fibers . Thus bone formation can adapt to different loading conditions by changing the internal lamellar organization of bone tissue. www.indiandentalacademy.com 131
  132. 132. Fluorescent Labels/Vital Stains.   Originated by John Hunter. Dye marks the location where active growth is occurring. Administered in vivo calcium binding labels are anabolic time markers of bone formation. Mechanism of bone growth is determined by analysis of label incidence and interlabel distance. www.indiandentalacademy.com 132
  133. 133.   Sequential use of different colored labels can be used to assess bone growth, healing and functional adaptation. Tetracycline, calcein green, xylenol orange, alizarin complexone, demeclocycline and oxytetracycline are some commonly used labels. www.indiandentalacademy.com 133
  134. 134. Microradiography.    This gives high resolution of images of bone sections and show differential density between primary and secondary bone. Strength of the bone is directly related to the degree of mineralization. Thus secondary bone has more strength than primary bone. Secondary mineralization process takes about 8 months to form and hence the minimum retention period after active orthodontic correction should be 6-8 months. www.indiandentalacademy.com 134
  135. 135. Autoradiography.    In this method radioactive precursors for structural and metabolic materials are detected within tissue by coating histological sections with a nuclear track emulsion. Localization of radioactive disintegration reveals the location of the precursors. Specific radioactive labels for protein carbohydrates or nucleic acids are injected at known interval prior to tissue sampling. www.indiandentalacademy.com 135
  136. 136.      Quantitative and qualitative assessment of the label uptake is a physiologic index of cell activity. Commonly used autoradiographic labels are: A. 3 H thymidine. B. 3 H proline. C. Bromodeoxyuridine. www.indiandentalacademy.com 136
  137. 137. Nuclear volume morphometry    It is a cytomorphometric procedure which measures the nuclear size for assessing the stages of differentiation of osteoblastic precursor cells. Pre osteoblasts have significantly larger nuclei than their committed osteoprogenitor precursors or their osteoblast progeny. The method is used in determining the relative differentiation of PDL and other bone living cells. www.indiandentalacademy.com 137
  138. 138.    Natural markers. The persistence of certain developmental features has led to their use as natural markers by means of serial radiography. Eg: trabaculae,nutrient canals and lines of arrested growth can be used for reference to study deposition, resorption and remodeling. Certain natural markers are used as cephalometric landmarks. www.indiandentalacademy.com 138
  139. 139. Implants   Bjork devised a method of implanting tiny bits of tantalum or biologically inert alloys into growing bone which served as radiographic reference markers for serial cephalometric study. The method allows precise orientation of serial cephalograms and information on the amount and sites of bone growth. www.indiandentalacademy.com 139
  140. 140. Finite element modeling (FEM).    It is a analytical method for calculating stresses and strain within mechanically loaded structures by breaking the structure down into group of small elements of known mechanical behavior so that the response of the entire structure to loading is estimated. The method requires accurate and precise measurements of known landmarks in the system. It utility in analysis of growth and development has not been tested except to compare its findings with conventional methods. www.indiandentalacademy.com 140
  141. 141. Microelectrodes    Thin tungsten or glass electrodes are inserted into the PDL. The changes in electrical potential are measured in the extra cellular space during initial response to orthodontic treatment In general widened areas have negative electrical potential and compressed positive. www.indiandentalacademy.com 141
  142. 142. Thank you For more details please visit www.indiandentalacademy.com www.indiandentalacademy.com 142