Growth of Maxilla, Mandible, Soft Tissue, and Body (most ...

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Growth of Maxilla, Mandible, Soft Tissue, and Body (most ...

  1. 1. Growth of the Maxilla, Mandible, Soft Tissue and Body Adriana Da Silveira, DDS, MS, PhD ORTD 323 Summer 2003
  2. 2. Changes in Overall Body Proportions
  3. 3. Not all tissue systems of the body grow at the same rate Scammon’s Curve
  4. 4. Variability <ul><li>Not everyone is alike in the way that they grow </li></ul><ul><li>Percentile growth/ standard deviation to the norm </li></ul><ul><li>Racial and ethnic differences </li></ul><ul><li>Boys vs Girls </li></ul>
  5. 5. Growth Curves <ul><li>Boys reach most of their height at age of 17 whereas girls reach theirs at around 15. </li></ul>Boys: 2 to 18 years Girls: 2 to 18 years
  6. 6. Deviations from the norm in growth <ul><li>Sickness - nutrition </li></ul><ul><li>late/early maturers </li></ul><ul><li>problems with growth (hormones or genetics) </li></ul>
  7. 7. Why do we assess growth? <ul><li>To determine optimum time for treatment (growth modification and surgery) </li></ul><ul><li>to determine the amount of growth left </li></ul><ul><li>to determine type of growth </li></ul>
  8. 8. How to assess growth <ul><li>Hand wrist x-ray </li></ul><ul><li>sexual maturity: onset of menarche in girls, voice changes and facial hair in boys </li></ul><ul><li>lateral cephalogram tracings: superimpositions </li></ul>
  9. 9. Other indicators of growth <ul><li>Ask parents how much the child grew last year (height and shoe size) </li></ul><ul><li>look at parent’s phenotype: tall or short </li></ul>
  10. 10. Principles of Tissue Growth <ul><li>Hypertrophy </li></ul><ul><li>hyperplasia </li></ul><ul><li>increased production of extracellular matrix (cell independent) </li></ul>
  11. 11. Bone, muscle and soft tissue growth <ul><li>All are dependent on each other to some degree </li></ul>
  12. 12. <ul><li>Growth of the soft and cartilaginous tissues = interstitial growth </li></ul><ul><li>Growth of mineralized tissues = can be done in the surface only (periosteum)= surface apposition of bone </li></ul>
  13. 13. Growth of Cartilage/ Endochondral Ossification <ul><li>Long bones </li></ul><ul><li>Epiphyseal plate contains dividing cartilaginous cells </li></ul><ul><li>Rate of growth and maturation of cells need to be equal for growth to occur </li></ul>Proliferating cartilage Epiphyseal plate
  14. 14. Intramembranous Bone Formation <ul><li>Cranial Vault and jaws </li></ul><ul><li>Meckel’s cartilage will be transformed into middle ear ossicles and sphenomandibular ligament and is not involved with the bone formation of the jaws </li></ul>
  15. 15. The growing face 8 months, 6 y, 8 y and 20 y old
  16. 16. The Human Head Shape Brachycephalic Dolichocephalic <ul><li>short and wide </li></ul><ul><li>tall and narrow </li></ul>
  17. 17. Reasons for Describing Head and Face Shape <ul><li>The growth direction of the face and jaws is different in each type of head and/or face. </li></ul>
  18. 18. Reasons for Describing Head and Face Shape <ul><li>“ Brachy” tends to grow horizontally; “dolicho” tends to grow vertically. </li></ul><ul><li>Knowing the general pattern of growth and the expected direction can be helpful in orthodontic diagnosis and treatment planning. </li></ul>
  19. 19. Soft Tissue Profile Convex straight concave retrognathic orthognathic prognathic
  20. 20. Soft Tissue Changes with Growth <ul><li>Soft tissue profile tends to flatten with growth </li></ul><ul><li>Nose and chin growth at teenage years may change facial appearance </li></ul>Boy growing normally Black - 10 yo red - 14 yo
  21. 21. Theories of Craniofacial Growth <ul><li>Classical: bone growth is primary, soft tissues adjust to the growth of the bones. </li></ul><ul><li>Functional matrix: soft tissue functional demands are primary, bones grow in response to functional demands. </li></ul>
  22. 22. Principles of Growth <ul><li>Resorption </li></ul><ul><li>apposition </li></ul><ul><li>surface remodeling of a bone in the opposite direction to that in which it is being translated by growth of adjacent structures </li></ul>
  23. 23. Growth of the Craniofacial Complex <ul><li>Cranial Vault </li></ul><ul><li>Cranial Base </li></ul><ul><li>Maxilla </li></ul><ul><li>Mandible </li></ul>
  24. 24. Cranial Vault Growth <ul><li>Apposition of bone in the cranial sutures accounts for growth after birth. </li></ul><ul><li>Pressure from the growing brain promotes resorption of bone in the inner surfaces of the cranial vault = remodeling allows for changes in the contour. </li></ul>
  25. 25. Growth of the Cranial Base <ul><li>The cranial base is composed mostly by bones formed by endochondral ossification. </li></ul><ul><li>Bands of cartilage are formed between centers of ossification called synchondrosis: </li></ul><ul><li>Spheno-occiptal synchondrosis </li></ul><ul><li>intersphenoid synchondrosis </li></ul><ul><li>spheno-ethmoidal synchondrosis </li></ul>
  26. 26. Growth of the Cranial Base <ul><li>Cranial base grows by endochondral ossification that occurs at both margins of the synchondrosis. </li></ul>
  27. 27. Growth of the Maxilla <ul><li>Remodeling of the palatal vault moves it in the same direction as it is being translated </li></ul><ul><li>bone is removed from the floor of the nose and added to the roof of the mouth </li></ul>
  28. 28. Growth of the Maxilla <ul><li>On the anterior surface, bone is removed, partially cancelling the forward translation. As the vault moves downward, the same process of bone remodeling also widens it. </li></ul>
  29. 29. Growth of the Maxilla <ul><li>Growth of the surrounding soft tissues translates the maxilla downward and forward, opening spaces in the sutures where bone is added. </li></ul>
  30. 30. Growth of the Maxilla <ul><li>Midpalatal suture is opened until teenage years. </li></ul><ul><li>Apposition of bone in the molar area accounts for space for the third molars. </li></ul>
  31. 31. Growth of the Maxilla <ul><li>Summary: </li></ul><ul><li>growth of the maxilla occurs in 2 ways: </li></ul><ul><li>by apposition of bone in the sutures that connect the maxilla to the cranial base </li></ul><ul><li>by surface remodeling. </li></ul>
  32. 32. Growth of the Mandible <ul><li>Remodeling is done by resorption in the anterior part of the ramus and deposition in the posterior part of the ramus </li></ul>
  33. 33. Growth of the Mandible <ul><li>Overall growth direction results in a downward and forward displacement with most of growth occurring in the ramus. </li></ul>
  34. 34. Growth of the Mandible <ul><li>Mandibular symphysis is closed by age of 1 year. </li></ul><ul><li>Late mandibular growth: </li></ul><ul><li>can occur in the late teenage years or adulthood </li></ul><ul><li>most often seen in asians and males </li></ul><ul><li>can cause incisor crowding when there is a tight occlusion (overbite/overjet) </li></ul>
  35. 35. When things go wrong <ul><li>Congenital craniofacial malformations: cleft lip/palate, syndromes (Apert, Crouzon, etc..), craniosynostosis </li></ul><ul><li>Non-syndromic craniosynostosis </li></ul><ul><li>Trauma </li></ul><ul><li>Ankylosis </li></ul><ul><li>Juvenile rheumatoid arthritis </li></ul>
  36. 36. When things go wrong <ul><li>Blow to one side of the mandible may fracture the condylar process on the opposite side </li></ul><ul><li>pull of the lateral pterygoid muscle distracts the condylar fragment including all the cartilage = resorption occurs </li></ul>Trauma

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