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Growth and development

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Orthodontics - Growth and Development Part 1

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Growth and development

  1. 1. Growth and Development Dr.Saurabh Goel Monday, September 1, 2014 1
  2. 2. Contents • Introduction • Definition • Physiology of Growth • Factors affecting • Pattern of Growth • Variability of Growth • Timing of Growth • Modes of Growth • Characteristics • Sites and Types of Growth • Methods of studying Growth Monday, September 1, 2014 2
  3. 3. What exactly does the term “growth” imply to you? Monday, September 1, 2014 3
  4. 4. To understand this you must first know what do you mean by growth and development? • Development connotes a maturational process involving differentiation at the cellular and tissue levels, thereby focusing on actual biological mechanism that accounts for overall growth. Monday, September 1, 2014 4
  5. 5. Definition of Growth ( Learn any two ) • Todd – Growth is an increase in size • Huxley – Self multiplication of living substance • Krogman – Increase in size, Change in proportion and Progressive complexity. • Meridith – Entire series of sequential anatomic and physiologic changes taking place from beginning of prenatal life to senility (senility means old age in simpler words) • Moyers – Quantitative aspect biological development per unit of time • Moss – Change in any morphological parameter which is measurable Monday, September 1, 2014 5
  6. 6. Definitions of Development (Any two) • Todd – It means progress towards maturity. • Moyers – All naturally occurring unidirectional changes in the life of an individual from its existence as a single cell to its elaboration as a multifunctional unit terminating in death. • Profitt – Increase in complexity • Carlson – Its a life long process that encompasses all structural and functional changes that takes place from conception through maturity. Monday, September 1, 2014 6
  7. 7. Negative Growth • Generally we equate growth with enlargement but there are instances in which growth results in decrease in size. • Examples of Negative Growth – Thymus gland Monday, September 1, 2014 7
  8. 8. Flashback of Growth - Physiology • It is continuous interaction between endocrine and skeletal systems • Key factor in Growth – GH (Growth Hormone) secreted by Anterior Pitutary ( Somatotrophic cells ) • Release of GH is regulated by Hypothalamic hormones. Monday, September 1, 2014 8
  9. 9. Factors affecting Physical Growth • Heredity • Nutrition • Illness • Race • Socio economic status • Family size • Birth order • Secular trends • Climactic and seasonal effects • Exercise • Physiological disturbances Monday, September 1, 2014 9
  10. 10. Some concepts of growth • Rhythm of growth- Human growth is not a steady and uniform process wherein all parts of body enlarge at same rate. • There are waves of growth seen in both sexes and these waves are more intense and rapid in first two years. • Growth Spurts- Sudden increase in growth is termed as “Growth Spurt” • Timings of growth spurts are- 1. Just before birth 2. 1 year after birth 3. Mixed dentition growth spurt 4. Pre-pubertal growth spurt Monday, September 1, 2014 10
  11. 11. Differential Growth • Different organs grow at different rates , to a different amount and at different times • Two important aspects of differential growth- 1. Scammon’s growth curve 2. Cephalo- caudal gradient Monday, September 1, 2014 11
  12. 12. Scammon’s Growth Curve Monday, September 1, 2014 12
  13. 13. Cephalo-caudal gradient Monday, September 1, 2014 13
  14. 14. Methods of gathering growth data • Longitudinal Studies • Cross sectional Studies • Semi Longitudinal Studies Monday, September 1, 2014 14
  15. 15. Longitudinal Studies • A longitudinal study is a correlational research study that involves repeated observations of the same variables over long periods of time — often many decades. It is a type of observational study. Monday, September 1, 2014 15
  16. 16. Advantages and Disadvantages of Longitudinal Studies • Specific development pattern of individual can be studied and compared • Variation in development among individuals within the sample can be studied • Long periods • Require maintenance of data • Risk of sample size reducing due to change in place etc. Monday, September 1, 2014 16
  17. 17. Cross-sectional Studies • Cross-sectional studies (also known as cross-sectional analyses, transversal studies, prevalence study) are one type of observational study that involves data collection from a population, or a representative subset, at one specific point in time. • Advantages- • Short Duration • Possible to get a large sample as duration of study is short • Possible to repeat the study in case of a flaw Monday, September 1, 2014 17
  18. 18. Semi-longitudinal Studies • Combination of longitudinal and cross sectional methods so as to derive advantages of both systems Monday, September 1, 2014 18
  19. 19. Methods of studying growth 1. Bimetric tests 2. Vital staining 3. Radio-isotopes 4. Implants 5. Radiographic techniques 6. Natural markers 7. Comparative anatomy Monday, September 1, 2014 19
  20. 20. Mechanisms of Bone-growth • Bone growth occurs by a process called Bone remodeling • Bone remodeling involves 1. Bone Deposition 2. Bone Resorption • Changes that both these processes can bring in are – 1. Change is size 2. Change in shape 3. Change in proportion 4. Change in relationship of bone with adjacent structures Monday, September 1, 2014 20
  21. 21. Important Topics • Cortical Drift- Interplay of Bone Deposition and Bone Resorption wherein growth movement occurs towards the deposition side • Displacement- Movement of whole bone as a unit is known as Displacement. It can be of two types 1. Primary 2. Secondary Monday, September 1, 2014 21
  22. 22. Theories of growth 1. Genetic Theory 2. Sutural Theory by Sicher (1940) 3. Cartilaginous Theory by James Scott 4. Functional Matrix Concept by Melvin Moss (1969) 5. Von Limborgh’s Theory (1970) 6. Enlow’s expanding V-Principle (Continued in next lecture) Monday, September 1, 2014 22

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