Principles of growth and development


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by - Dr.chiranjeev singh
pg orthodontics
a complete seminar covering every point. in growth & dev.

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Principles of growth and development

  1. 1. GROWTH & DEVELOPMENT 1 1Theories , Concept & principles
  2. 2. 2 CONTENTS1. Introduction2. Goals3. Objectives4. Definitions5. Theories6. Types of growth7. Themes of development8. Methods of studying growth9. Types of growth10. Methods of gathering growth data11. Mechanism of bone growth12. Factors affecting growth
  3. 3. 3 Aim3 To understand the  1. basic growth concepts.  2. growth and development of the main craniofacial components.  3. tissues involved in facial growth.
  4. 4. 44  4. differences in facial form and patterns.  5. major deformities of growth.
  5. 5. 55  6. why and how knowledge of facial and somatic growth and development is critical
  6. 6. 66
  7. 7. 77
  8. 8. 8 Definition of Growth8  “Growth usually refers to an increase in size and number” – Proffit .1986  “Self multiplication of living substance”- J.S.Huxley
  9. 9. 99  “Growth may be defined as the normal change in the amount of living substance- moyers 1988  “Growth refers to increase in size” - Todd 1931  “Change in any morphological parameter which is measurable”- Moss.
  10. 10. 10 Definition of Development10 Development is a progress towards maturity” – Todd- 1931 “Development connotes a maturational process involving progressive differentiation at the cellular and tissue levels” - Enlow
  11. 11. 11 •“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 is increase in complexity- Profitt 198611
  12. 12. 12 Key Definitions12 Morphogenesis – “A biologic process having an underlying control at the cellular and tissue levels” Differentiation – “It is a change from generalized cells or tissues to a more specialized kinds during development”
  13. 13. 13 •Maturation – “It is the emergence of personal characteristics and behavioral phenomenon through growth processes”13
  14. 14. 14Theories14
  15. 15. 1515 The major theories explaining growth are 1.Genetic Theory 2.Sutural Theory 3.Cartilageneous Theory 4.Functional matrix Theory 5.Van Limborgh‟s Theory
  16. 16. 1616  Other theories related to craniofacial growth are –  Enlow‟s expanding „V‟ principle
  17. 17. 17 GENETIC theory Growth iscontrolled bygenetic influenceand is preplanned.17
  18. 18. 18 Sutural dominance theory SICHER 1940 – stated that cranio facial growth occurs at sutures.  sutural growth is the proliferation of the connective tissue between the two bones.18
  19. 19. 1919  Growth of the cranial vault – expansive proliferative growth by sutural conn ective tissue that forces the bones of the vault away from each other.
  20. 20. 20 Points against sutural theory1. Lack of innate growth2. Growth takes place even in absence of sutures .CONCLUSION: Sutures are growth sites not centers.
  21. 21. 21 Cartilaginous theory21 The Irish anatomist, James H. Scott, proposed an explanati on, the nasal septum theory or Scotts hypothesis  sutures play little or no direct role in the growth of the craniofacial skeleton.  Rather, sutures are secondary, and compensatory sites of bone formation and growth.  Scott concluded :- that the nasal septum is most active and important for crani ofacial skeletal growth late prenatally and early post natally , through approximately three to four years of age in humans.
  22. 22. 22SCOTT‟S HYPOTHESIS: Intrinsic growth-controlling factors are in cartilage & periosteum. Sutures are secondary & dependent on extrasutural influences. Cartilaginous part of skull must be recognized as primary centers of growth, with nasal septum being a major contributor in maxillary growth.
  23. 23. 23Nasal septal cartilage Primary mechanism for growth of nasomaxillary complex. Experimental excision of the nasal septum affects the growth of the upper face considerably . Nasal septum – acts as central support for the upper facial area, and its loss results in a predictable collapse in the area.
  24. 24. 2424
  25. 25. 25Condylar cartilage Growth of the condylar cartilage is responsible for the anteroposterior growth of the mandible- primary growth centre. Growth of the mandible- a bent long bone, with the mandibular condyar cartilage being equivalent to the epiphyseal plates of long bones whose growth forces the mandible downward and forward, away from the cranial base
  26. 26. 26 Scott stated that :- If the condylar cartilage is transplanted to a relatively nonfunctional site, such as the subcutaneous or brain tissue, it does not maintain its structure and does not behave like the condylar cartilage in situ. Bilateral condylectomy, congenital absence of the cartilage appreciable effect on the growth of the rest of the mandible in humans.
  28. 28. 28INTRODUCTION Given by MELVIN MOSS IN 1969 and reviewed by him in 1990s Worked on the concept put by VAN DER KLAAUW of FUNCTIONAL CRANIAL COMPONENT The origin, growth and maintenance of all skeletal tissues and organs are always secondary, compensatory and obligatory response to all the temporally and operational prior events and processes that occur in specifically related non- skeletal tissues, organs or functional spaces
  29. 29. 29INTRODUCTION MOSS said that head and neck region consist of number of functions• Digestion• Respiration• Speech• Olfaction• Balance• Vision
  30. 30. 30INTRODUCTION  Each of these function is completely carried out by FUNCTIONAL CRANIAL COMPONENT  Each functional cranial component consists of all the tissues ,organs, spaces and skeletal parts necessary to carry out a given function. The functional cranial component is divided into 1.functional matrix 2.skeletal unit.
  31. 31. Skeletal unit 31 Composed of –bone, cartilage and tendinous tissue MICROSKELETAL UNIT bones consisting of number of small skeletal unitsMAXILLA1. orbital2. pneumatic3. palatal4. basalMANDIBLE-1. coronoid2. angular3. alveolar4. basal
  32. 32. 3232 MACROSKELETAL UNIT- when adjoining portions of number of neighboring bones carrying out a single function
  33. 33. 33FUNCTIONAL MATRICES This consist of soft tissue- muscle,gland,nerve,vessels,fat and teeth as well as non skeletal cartilages DIVIDE INTO TWO TYPES- Periosteal matrices Capsular matrices
  34. 34. 34PERIOSTEAL MATRICES All non skeletal functional units adjacent to skeletal unit . act by bringing transformation of the related skeletal units . Functional hypertrophy/hyperactivity- increase in size and change in shape
  36. 36. 36 Each of these capsules is an envelop containing functional cranial component Sandwiched between two covering layers Capsules expands due to volumetric increase of capsular matrix This results in the translative movement of the embedded bones
  37. 37. 37 NEUROCRAINAL CAPSULE Sandwiched between-skin and dura mater Consists of-1. skin2. Connective tissue3. Apo neurotic layer4. Loose connective tissue5. Periosteum6. bone(base of skull)7. two layer dura mater
  38. 38. 38 The volumetric increase cause compensatory expansion of surrounding capsule. Later the calvarial functional cranial component as a whole are passively and secondarily translated.
  39. 39. 39 ORO FACIAL MATRIX Surround and protect oronasopharyngeal space. Surrounded by skin and mucous membrane on either side. Volumetric growth of these spaces is the primary morphogenetic event in facial skull growth
  40. 40. Van Limborgh’s theory 4040  By Van Limborgh in 1970  He combines all the existing theories  He supports the functional matrix theory , acknowledges some aspects of Sutural theory, and doesn‟t rule out the genetic involvement .  Suggested the following five factors that he believed controls growth. 1. Intrinsic genetic factor. 2. Local epigenetic factor.
  41. 41. 4141 3. General epigenetic factor. 4. Local environmental factor. 5. General environmental factor.
  42. 42. 42 Timing and sequential change a. Prenatal growth b. Postnatal growth c. Maturity d .Old age42
  43. 43. 43 Timing and sequential change •Prenatal growth- rapid increase in cell no. •Postnatal growth- till 20 yrs- growth starts declining & increasing maturation pickup speed. •Maturity-period of stability •Old age •death43
  44. 44. 44 GROWTH SPURTS44 Sudden increase in growth Is termed "growth spurt". Periods when A sudden acceleration Of growth occurs.
  45. 45. 4545 Physiological alteration in hormonal secretion cause for Growth Spurts. TIMINGS OF GROWTH SPURTS. a. Just before birth b. One year after birth c. Mixed dentition growth spurt  Boys : 8-11 years  Girls : 7-9 years d. Pre-Pubertal growth spurt  Boys : 14 - 16 years  Girls : 11-13 years
  46. 46. 46 Different types of growth46  Size change • Functional change  Positional change • Maturational change  Proportional • Compositional change change
  47. 47. 47 Proportional change Eg-Head of the infant Functional change Eg- production of enzymes, hormones47
  48. 48. 48 Size change- height, weight, volume Positional change- •Migration of neural crest cells •Eruption of teeth •Dropping of diaphragm48
  49. 49. 4949 Maturational change stability and adulthood Compositional change Eye pigmentation
  50. 50. 5050 Major themes of development  Changing complexity  Shifts from competent to fixation  Shifts from dependent to independent  Ubiquity of genetic control modulated by environment
  51. 51. 5151 Changing complexity  At all level of organization i.e sub-cellular to whole organism  Complexity is increase in development
  52. 52. 52 Shifts from competent to fixation52  Undifferentiated cells once differentiated become fixed. Shifts from dependent to independent  Development brings independence at most levels of organization.
  53. 53. 53 Ubiquity of genetic control53 modulated by environment  Genetic control of development is constantly being modified by environmental interactions
  54. 54. Importance of growth and 5454 development to orthodontist  Etiology of malocclusion  Health and nutrition of children  comparison of growth
  55. 55. 55  identification - abnormal occlusal55 development at an earlier stage  use of growth spurts  Surgery initiation
  56. 56. Normal features of 5656 Growth & Development  pattern -Differential Growth -cephalocaudal gradient of growth  Variability  Predictability  Normality  Timing, rate & direction
  57. 57. PATTERN 5757  Pattern in growth represents proportionality .It refers not just to a set of proportional relationships at a point in time but to change in these proportional relationships over time  In orthodontics , use of word pattern has both a morphological and a developmental application
  58. 58. 5858 DIFFERENTIAL GROWTH Different organs grow at different rates amount and at different times.  Scammon‟s curve of growth -Richard scammon
  60. 60. 60 conclusion60 Each tissue grows at different rate
  61. 61. 61 CEPHALOCAUDAL GRADIENT OF GROWTH61 • Axis of increased growth
  63. 63. 63 Growth of head and face63
  64. 64. 64 •It illustrates the change in overall body proportions during normal growth and development. •Imp aspect of pattern is its predictability.64
  65. 65. 65 Predictability65  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.  Change in growth pattern indicates some alteration in the expected changes in body proportions.
  66. 66. 66 Variability66  No two individuals with the exception of siamese twins are like.  Hence it is important to have a “normal variability” before categorizing people as normal or abnormal.
  67. 67. 67 Normality67 Normality refers to that which is usually expected, is ordinarily seen or typical – Moyers Normality may not necessarily be ideal. •
  70. 70. Timing of growth 7070  One of the factors for variability in growth.  Timing variations arise because biologic clock of different individuals is different.
  71. 71. 7171  It is influenced by:  genetics  sex related differences  physique related  environmental influences
  73. 73. 73 • Longitudinal growth studies • Methods of studying bone growth • Types of growth data • Methods of gathering growth data73
  74. 74. 74 Types of .growth data  Opinion  Observations.  Ratings and rankings.  Quantitative measurements. direct data. indirect data. derived data.74
  75. 75. 75 Types of growth data. • Opinion clever guess based on experience. crudest form of scientific knowledge. • Observations: for studying all or none phenomenon limited use . quantitative data is needed.75
  76. 76. 7676  RATING - comparison  RANKING -value
  77. 77. 77 Quantitative measurements Includes expressing a fact as a meaningful quantity or numbers. • Direct data: measurements ,living persons or cadaver -measuring device. • Indirect data: images or reproductions of actual person. • Derived data comparing at least two measurements.77
  78. 78. 78 Methods of gathering growth data. • Longitudinal studies . • Cross sectional studies. • Overlapping or semi longitudinal studies.78
  79. 79. 79 Longitudinal studies. • measurements of same person or group- regular intervals through time. • Advantage: temp. problems are smoothed with time, Variability, serial comparison makes study of specific developmental pattern of individual possible. Disadvantages: time consuming, expensive, sample loss or attrition, averaging.79
  80. 80. 80 Cross sectional studies80 Measurment of different individuals or different samples & studied at different periods ADVANTAGES  repeating  Quicker  Less costly  Statistical treatment made easier DISADVANTAGES  Variation amongst individuals cannot be studied
  81. 81. 81 Semi longitudinal studies. Merger of either studies81
  83. 83. 83 CRANIOMETRY. •measurements of skull • Neanderthal and Cro-Magnon skull. •Found in 18th century in Europe • information of extinct population ,growth pattern.Advantages: Precise measurements.Disadvantages: All data is cross sectional.83
  84. 84. 84 ANTHROPOMETRY: • soft tissue pts over bony landmarks- living individuals. • variation in soft tissue thickness –leads to different results • Measured at a point at the bridge of nose to a point at the greatest convexity of the rear of skull • individual growth directly measured • Produce longitudinal data84
  85. 85. • CEPHALOMETRIC RADIOGRAPHY: 85 • direct measurement - bony skeletal dimensions follow up same individual over time . • Disadvantages •precise orientation of head ,precise control of magnification.85 • 2D of 3D structure
  86. 86. 86 Mineralized sections. • Special stains • Thin sections- quench- rapidly86
  87. 87. 87 Micro radiography. • High resolution of images of bone sections • Differential density between primary and secondary bone. • Bone strength -proportional to degree of mineralization. • secondary bone has more strength than primary bone.87
  88. 88. 88 Magnetic Resonance Imaging Depicts- soft tissue growth contrast with hard tissue.88
  89. 89. 89 Bimetric tests E.g. Skeletal maturation & ossification89
  90. 90. 90 Fluorescent labels. • in vivo calcium binding labels • anabolic time markers of bone formation. • Mechanism of bone growth determined by analysis of label incidence and interlabel distance. • Sequential use of different colored labels assess bone growth, healing and functional adaptation. • Tetracycline,calcein green,xylenol orange, alizarin complexone,demeclocycline and oxytetracycline90
  91. 91. 91 Radioisotopes. • Radioisotopes of certain elements or compounds are often used as in vivo markers • labeled material injected and located within the growing bone by auto radiographic techniques. 1. Technetium 99 2. Calcium 45 3. Potassium 3291
  92. 92. 92 Autoradiography. • Histological sections are coated with a nuclear track emulsion to detect radiographic precursor for structural and metabolic material. • Specific radioactive labels for protein carbohydrates or nucleic acids are injected.92
  93. 93. 93• Commonly used auto radiographic labels are:• A. 3 H thymidine.• B. 3 H proline.• C. Bromodeoxyuridine.93
  94. 94. 94 Vital staining • John Hunter- alizarin dye • Other dyes : tetracycline trypon blue lead acetate procion lead acetate94 alizarin red 5
  95. 95. 95 • Vital staining aids in studying: •Manner in which bone is laid down • site of bone growth •the direction and amount of growth • the timing and relative duration of growth at different sites.95
  96. 96. 96 Natural markers. • developmental features - serial radiography. • cephalometric landmarks.96
  97. 97. 97 Implant markers. • By arne bjork at royal dental college in copenhagen • biologically inert alloys into growing bone – • radiographic reference markers for serial cephalometric study. • The method allows precise orientation of serial cephalograms and information on the amount and97 sites of bone growth.
  98. 98. 98
  99. 99. 99 Mechanisms of bone growth99  Deposition and resorption  Growth fields  Modelling  Remodelling  Growth movements drift displacement
  100. 100. 100 Deposition and resorption100  Bone sides which face the direction of growth are subject to deposition (+) and those opposite to it undergo resorption(-) The surface principal  The surface facing towards the direction of progressive growth receives new bone deposition & surface facing away undergoes resorption. The result is the process termed cortical drift, a gradual movement of the growing area of the bone.
  101. 101. Deposition and resorption101  Changes are:- a. Change in shape b. Change in size c. Change in proportion d. Change in relationship of the bone with adjacent structures
  102. 102. Growth fields102  Inside and outside of every bone is covered by growth fields which control the bone growth.  They are both resorptive and depository types..
  103. 103.  About one half of the bone is periosteal and the other half endosteal.103 If endosteal surface is resorptive then periosteal surface would be depository. it provides two growth functions:1. Enlargement of any given bone.2. Remodelling of any given bone.
  104. 104. Growth sites104  Growth fields having special role in the growth of the particular bone(grows fast) are called growth sites ;  e.g. mandibular condyle, maxillary tuberosity, synchondrosis of the basicranium, sutures and the alveolar
  105. 105. Growth sites105
  106. 106. Growth centers106  Special areas which are believed to control the overall growth of the bone e.g.mandibular condyle.  Force, energy or motor for a bone resides primarily within its growth centre.  But according to recent studies these centers do not control the whole growth process.
  107. 107. MODELING107  Bone modeling involves independent sites of resorption and formation that change the size and shape of a bone.
  108. 108. Remodelling108  Required differential growth activity required for bone shaping.  It involves deposition and resorption occurring on opposite ends  Four types  Biochemical remodelling  Haversian remodelling  Pathologic remodelling  Growth remodelling
  109. 109. 109 1. Biomechanical- continuous deposition & removal of ions to maintain mineral homeostasis 2. Growth remodelling- constant replacement of bone during childhood 3. Haversian remodelling- secondary process of cortical reconstruction as primary vascular bone is replaced. 4. Pathologic remodelling- regeneration & reconstruction of bone during & following trauma.
  110. 110. 110  E.g. The ramus moves posteriorly by the combination of deposition and resorption.  so the anterior part of the ramus gets remodeled into a new addition for the mandibular corpus.
  111. 111. Functions of Remodeling111 1. Progressively change the size of whole bone 2. Sequentially relocate each component of the whole bone 3. Progressively change the shape of the bone to accommodate its various functions
  112. 112. 112 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 .
  113. 113. Drift113  It is remodeling process and a combination of deposition and resorption.  If an implant is placed on depository side it gets embedded. Eventually marker becomes translocated from one side of cortex to other.
  114. 114. Displacement114  Displacement is a physical movement of the whole bone as it remodels caused due to surrounding physical forces  Two types: 1. primary displacement 2. secondary displacement
  115. 115. Primary displacement115  It is a physical movement of a whole bone and occurs while the bone grows and remodels by resorption deposition. As the bone enlarges it is simultaneously carried away from the other bones in direct contact with it.  E.g. in maxilla
  116. 116. Secondary displacement116  It is the movement of a whole bone caused by the separate enlargement of other bones.  Example- growth in the middle cranial fossa results in the movement of the maxillary complex anteriorly & inferiorly
  117. 117. Rotation117 According to Enlow, growth rotation is due to diagonally placed areas of deposition and resorption Two types  Remodelling rotations  Displacement rotations
  118. 118. Principle of „Area relocation‟118 Both remodeling and displacement together cause a shift in existing position of a particular structures with reference to another
  119. 119. Enlow‟s V principal119  Most useful and basic concept in facial growth as many facial and cranial bones have a V- shaped configuration.  Bone deposition(+) occurs on the inner side and resorption (-) occurs on the outer surface.
  120. 120. Example with V oriented vertically120  bone deposition on lingual side of coronoid process , growth proceeds and this part of the ramus increases in vertical dimension.
  121. 121. V oriented horizontally121  Same deposits of bone also bring about a posterior direction of growth movement.  .
  122. 122. 122  This produces a backward movement of coronoid processes even though deposit is on the lingual side
  123. 123.  Same deposits carry base of bone in medial direction .123 So, the wider part undergoes relocation into a more narrow part as the whole v moves towards the wide part .
  124. 124. VARIOUS FACTORS AFFECTINGGROWTH AND DEVELOPMENT-pre-natal factorsCausing INTRAUTERINE GROWTH RETARDATION (IUGR)-1. Chromosomal abnormalities2. Teratogens – a. Infectious agents b. Physical agents c. Chemical agents d. Hormones
  125. 125. 3 Congenital infections- a. Rubella . b. Toxoplasmosis c. Syphilis d. HSV, HIV4. Poor Maternal health- hypertension, renal & cardiac disease5. Mother’s nutritional status/ Socioeconomic status6. Mother’s use of alcohol, cigarettes, drugs etc7. Placental insufficiency8. Multiple births
  127. 127. Natal causes127 Growth can be affected by injuries during birth- 1. Intrauterine molding  Arm pressed against the face -maxillary deficiency  Head flexed against the chest- mandibular deficiency. 2. Trauma to mandible during birth process – forceps delivery
  128. 128. Post-natal factors GENETICS/HEREDITY: GENERAL EPIGENETIC FACTORS: a. Hormonal factors b. Neural control c. General body growth LOCAL EPIGENETIC FACTORS: a. Function b. Muscles
  129. 129.  GENERAL ENVIRONMENTAL FACTORS: a. Nutrition b. Illness c. Race d. Climate and seasonal effects e. Exercise f. Family size & birth order g. Psychological disturbance h. Socioeconomic factors LOCAL ENVIRONMENTAL FACTORS: a. Habits
  130. 130. Genetic / hereditary factors Potential for growth is genetic. Actual outcome of growth - Genetic potential combined with Environmental influences Advanced rate of maturity in females than males – delaying action of „Y‟- chromosome.
  131. 131.  Genetic control seen in- a. body size, shape, deposition of fat b. patterns & rate of growth c. onset of growth events- menarche, -eruption of teeth, -ossification of bones, -beginning of adolescent growth spurt
  132. 132. Hormonal factors HORMONES LOCAL GENERAL(ENDOCRINE) Ex. Acetyl choline NON-SPECIFIC SPECIFIC Secretin (all body cells) (target) organs) ex. Growth hormone ex. ACTH Thyroid hormones LH, FSH Insulin
  133. 133. Hormones affecting growth1. Growth Hormone2. Thyroid Hormones3. Parathyroid Hormone4. Calcitonin5. Insulin6. Adrenocortical hormones
  134. 134. Growth hormone/ somatotropin Secreted by- ACTIONS INDIRECT DIRECT Protein synthesis synthesis & secretion Lipolysis of IGF Protein breakdown Use of glucose for ATP production Increases size & number of cells Converts chondrocytes into osteogenic cells Deposition of proteins by chondrocytic and osteogenic cells
  135. 135. nutrition Proteins ( 9 essential amino acids), carbohydrates, fats. Ca, Mg, Mn, , Vit D – bone & tooth Fe- Hb formation Vit A- activities of osteoblasts & osteoclasts Vit B complex- DNA formation & cell maturation Vit C- collagen formation Oxygen – cardiac anomalies – stunted growth Teeth- bone- soft tissues
  136. 136. Effects of malnutrition Delays growth, adolescent spurt Affects size of body parts, proportions & chemistry Quality & texture of tissues – bone & teeth If period of malnutrition short – “catch-up growth” Girls better buffered against malnutrition &
  137. 137. illness Minor childhood illnesses – not much effect. Serious, prolonged, illnesses – marked effect Disease decreased GH. Cartilage cell growth stopped temporarily. Catch up growth – brings child back on predetermined genetic curve.
  138. 138. Race Racial differences-climatic, nutritional or socioeconomic. Gene pool differences – North American blacks are ahead of whites in skeletal maturity at birth & for at least first 2 yrs of life. Calcification & eruption of teeth 1 yr earlier than whites.
  139. 139. Climate & seasonal effects Cold climates- increased adipose tissue. Increased height – in spring than autumn. Increased weight - in autumn than spring. Growth in height & eruption of teeth – more at night than day. Fluctuations in hormone release.
  140. 140. Family size & birth order First-born children – weigh less at birth, ultimately less stature. Sizes, maturation, intelligence of individuals- has no correlation with size of family. EXERCISE Effects on growth is not proved. but Development of motor skills, in muscle mass, fitness, general well-being.
  141. 141. Psychological disturbances  Psychological abuse adversely affects growth-  accidental discovery in 1948 by German physician. Ht. & wt. gain of children in 2 German orphanages for 1 yr.  Orphanage governed by harsh headmistress – grew less in ht. & wt. though 20% extra calories.  Because of Inhibition of growth hormone.  Catch-up growth.
  142. 142. Socioeconomic factors Favorable socioeconomic status--different type of growth-variation in timing of growth Positive relationship associated with socioeconomic “class” ; not family income.
  143. 143. Habits Habits are learned patterns of muscle contraction of a very complex nature.1. Thumb-sucking2. Tongue-thrusting3. Mouth-breathing
  144. 144. Thumb-suckingBegins at birth and outgrown by 3-4 years.Through sucking child obtains- feelingsof euphoria, sense of security and feelingof warmth.Maxillary constriction- not due to negativepressure.
  145. 145.  Mandible positioned in a downward manner to145 accommodate the interposed thumb- causing increased eruption of posterior teeth.  Tongue is lowered which decreases the pressure on the upper posterior teeth.  Imbalance between tongue & cheek pressures.  Cheek pressure increased as buccinator muscle contracts during suckling
  146. 146. Tongue-thrusting Tongue thrust is forward placement of the tongue between the anterior teeth & against the lower lip during swallowing- Schneider (1982). Tongue thrusting results due to lack of anterior seal. Skeletal open bite Steep mandibular plane. Increased anterior facial height.
  147. 147. Mouth-breathing  Breathing through the mouth alters equilibrium of the jaws & teeth.  Lowering of the mandible & tongue & extension of the head is seen.
  148. 148.  „Adenoid facies‟-separated lips, small nose, nostrils poorly developed, pout in the lower lip, vacant facial expression. downward & backward rotation of mandible & increased lower facial height.
  149. 149. REFERENCES:149  Proffit:contemporary orthodontics.  T.M.Graber: Orthodontics Principles And Practice 3rd edition  Moyers:handbook of orthodontics.  Donald H. enlow: facial growth 2nd edition  An inventory of United states and Canadian growth record sets.S.Hunter , Baumrind S AJO 1993.
  150. 150. References150  Growth changes in the nasal profile from 7-8 yrs AJO 1988:94 Meng H ,R Nanda  Lewis A B, Roche AF pubertal spurts in cranial base & mandible AJO 1985:55  Baumrind S,Korn EL,quantitation of maxillary remodeling. AJO 1987:91  10.Sarnat: Growth pattern of the mandible; AJO-DO 1986: 90;221-233
  151. 151. 151