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  2. 2. Part IBONE 2
  3. 3. BONE TISSUE Bone tissue  2 Types of bone tissue:  is a specialized form of 1. Compact (Cortical) bone connective tissue and is the main element of the 2. Spongy (Cancellous) bone skeletal tissues.  is composed of cells and an extracellular matrix in which fibers are embedded.  is unlike other connective tissues in that the extracellular matrix becomes calcified. 3
  4. 4. OF BONE1. Support: provides framework that supports and anchors all soft organs.2. Protection: skull and vertebrae surround soft tissue of the nervous system, and the rib cage protects vital thoracic organs.3. Movement: skeletal muscles use the bones as levers to move the body.4. Storage: fat stored in the interior of the bones. Bone matrix serves as a storehouse for various minerals.5. Blood Cell Formation: hematopoiesis occurs within the marrow cavities of the bones. 4
  5. 5. CLASSIFICATION OF BONE Bone may be classified in several ways: Developmentally Histologically By shape Endochondral bone Compact (Cortical) Long bones Bone Intramembranous bone Spongy (Cancellous) Short bones Bone Flat bones Irregular bones 5
  6. 6. A. endochondral bone • Where bone is preceded by a cartilagenous model that is eventually replaced by bone In a process termed endochondral ossification.B. intramembranous bone • Where bone forms directly w/in a vascular, fibrous membrane. 6
  7. 7. “Oral Anatomy, Histology, and Embryology”CHEMICAL PROPERTIES OF BONE 60 % Inorganic material Composition of bones  is formed from carbonated hydroxyapatite. Inorganic Substances 25 % Organic Organic material Substances  mainly composed of Water Type I collagen.  The organic part is also composed of various growth factors:  15% Water  glycosaminoglycans, osteocalcin, osteonectin, bone sialo protein, osteopontin and Cell 7
  8. 8. ORGANIC MATRIX OF THE BONE Bone is formed by the Organic Components of the hardening of the Bone Matrix matrix, entrapping the cells. When these cells Collagen become entrapped from osteoblasts they become Non- osteocytes. collagenous proteins The organic matrix of bone is about:  90% collagen  10% non-collagenous proteins. 8
  9. 9.  Non-collagenous Proteins of Bone  are a heterogeneous group which vary from entrapped serum protein to glycoproteins  play a role in mineralization.  The main non-collagenous proteins comprise the:  Proteoglycans  Glycoproteins  Bone Gla-containing proteins  Serum proteins 9
  10. 10.  collagen.  Contributes towards the important biomechanical properties of tissue in terms of resisting loads and providing necessary resilience that prevents fractures.  The dominant collagen in bone is Type I.  Intrinsic collagen  collagen as secreted by osteoblasts.  Extrinsic collagen  Collagen formed by adjacent fibroblasts. 10
  11. 11. SHARPEY’S FIBERS Sharpeys fibers are the terminal ends of principal fibers (of the periodontal ligament) that insert into the cementum and into the periosteum of the alveolar bone. A study on rats suggests that the three-dimensional structure of Sharpeys fibers intensifies the continuity between the periodontal ligament fiber and the alveolar bone (tooth socket), and acts as a buffer medium against stress. 11
  12. 12. CELL TYPES IN BONE Osteoblasts  are mononucleate cells that are responsible for bone formation Osteocytes  When osteoblasts become trapped in the matrix they secrete, they become osteocytes. Bone-lining cells  Are inactive osteoblasts that cover all of the available bone surface and function as a barrier for certain ions Osteoprogenitor cells  relatively undifferentiated cells found on or near all of the free surfaces of bone, which, under certain circumstances, undergo division and transform into osteoblasts or coalesce to give rise to osteoclasts. Osteoclasts  is a type of bone cell that removes bone tissue by removing its mineralized matrix and breaking up the organic bone 12
  13. 13. RESORPTION AND FORMATION OF BONE DURINGREMODELLING Resorption Reversal Formation Resting 13
  14. 14. Also called Osteogenesis is the natural process of bone formation There are two processes resulting in the formation of normal, healthy bone tissue:  Endochondral (Intracartilaginous) Bone Ossification  The formation of bone in which a cartilage template is gradually replaced by a bone matrix, as in the formation of long bones or in osteoarthritic ossification of synovial cartilage.  Intramembranous Bone Ossification  thedevelopment of bone from tissue or membrane, as in the formation of the skull. 14
  15. 15.  Sutural Bone Growth  variable and irregularly shaped bones in the sutures between the bones of the skull. 15
  17. 17. BONE Also called as alveolar process The specialized bone structure that contains the alveoli or sockets of the teeth and supports the teeth. If the teeth are lost the alveolar process disappears It is composed mainly of two parts:  alveolar bone proper  Supporting bone
  18. 18. Alveolar Bone
  20. 20. DEVELOPMENT OF ALVEOLAR BONE Alveolar bone develops from the dental follicle The ectomesenchymal cells of the dental follicle differentiate into osteoblasts and lay down the matrix called osteoid Some osteoblasts become embedded in the matrix and are called osteocytes
  21. 21. Near the end of the 2ndmonth of fetal life, mandibleand maxilla form a groovethat is opened toward thesurface of the oral cavityAs tooth germs start todevelop, bony septa formgradually. The alveolarprocess starts developingstrictly during tooth eruption.
  22. 22. GROSS MORPHOLOGY OF BONEMorphology -is a branch of bioscience dealing with the study of the form and structure of organisms and their specific structural
  23. 23.  Alveolar Socket  Also called Dental alveolus  are sockets in the jaws in which the roots of teeth are held in the alveolar process with the periodontal Alveolar socket of the second premolar tooth in a bovine ligament. maxillary bone.
  24. 24.  Interdental Septa  “Septa” – in Latin, it means “fence” or “wall”  Are plates of bone that separate each individual sockets from one another. Interradicular Septa  Are thin plates of bone that separate the roots of multi-rooted teeth
  25. 25.  Cribriform Plate  also called as bundle bone  Is the compact layer of bone lining the tooth socket (alveolar socket)  Reflects the sieve-like appearance produced by numerous Volkmann’s canals passing from the alveolar bone to the PDL (periodontal ligament).  Numerous Sharpey’s Fiber pass through it.
  26. 26. ALVEOLAR PROCESS is the thickened ridge of bone that contains the tooth sockets on bones that bear teeth. The alveolar process contains a region of compact bone adjacent to the periodontal ligament called Lamina dura. Maxilla and Mandible  Are the tooth-bearing bones
  27. 27.  Lamina Dura  this part which is attached to the cementum of the roots by the periodontal ligament.  Is the bone lining the alveolus  In clinical radiographs, it Lamina Dura commonly appears as Radiographic appearance of alveolar bone proper as ‘Lamina a dense white line. Dura’
  29. 29. FUNCTIONS OF ALVEOLAR BONE Protection  Alveolar bone forms and protects the sockets for the teeth. Attachment  It gives the attachment to the periodontal ligament fibers, which are the principle fibers. These fibers which enter the bone are regarded as Sharpey’s fibers. Support  It supports the tooth roots on the facial and on the palatal/lingual sides. Shock-absorber  It helps absorb the forces placed upon the tooth by disseminating the force to underlying tissues.
  30. 30. FOHWIN%2Funit2%2F_ii-01.html&docid=VZHNS3piimFp2M&w=300&h=452&ei=x1WATpi2BoTBiQf3_-STRUCTURE OF THE ALVEOLAR BONEW3Dg&zoom=1&iact=hc&vpx=89&vpy=48&dur=483&hovh=100&hovw=64&tx=101&ty=176&sqi=2&page=1&tbnh=100&tbnw= 64&start=0&ndsp=12&ved=1t%3A429%2Cr%3A0%2Cs%3A0 Cortical Plate Spongiosa / Spongy Bone
  31. 31. a) outer cortical platesb) a central spongiosac) bone lining the alveolus (bundlebone)
  32. 32. CORTICAL PLATE Outer bony plate of varying thickness, which is the outside wall of the maxilla and mandible, covered with periosteum Continuous with the lamina cribriformis at the orifice of the alveoli – alveolar crest Consists of haversian systems (osteons) and interstitial lamellae Thicker in the mandible than maxilla Generally greater on the lingual than on the buccal/facial
  33. 33. ALVEOLAR BONE PROPER OR LAMINA An inner, heavily perforated bony lamellae, forming the alveolar wall In radiograph, appears as radioopaque line distinct from the adjacent spongiosa – Lamina Dura Contains osteons like other cortical bone, but is distinguished by the presence of Bundle Bone
  34. 34. SPONGIOSA Are spongy (or cancellous/trabecullar) bone between the 2 bony plates and between the lamina cribriformis of adjacent teeth or roots Consists of delicate trabeculae, between which are marrow spaces, filled mostly with fatty marrow Regions of maxillary tuberosity and the angle of mandible, erythropoietic …
  36. 36. VASCULAR SUPPLY OF ALVEOLAR PROCESS Alveolar process of the maxilla  Anteriorand posterior alveolar arteries (branch from the maxilla and infraorbital arteries) Alveolar process of the mandible  Inferioralveolar arteries (internal)  Periosteal branches of submental and buccal arteries (external)
  38. 38. DISEASE Periodontal disease is a type of disease that affects one or more of the periodontal tissues:  Alveolar bone  Periodontal ligament  Cementum  Gingiva While many different diseases affect the tooth- supporting structures, plaque-induced inflammatory lesions make up the vast majority of periodontal diseases and have traditionally been divided into two categories:  gingivitis or  periodontitis
  39. 39. HISTOLOGICAL ARRANGEMENT OF MATUREBONE  Mature bone is composed of:  Compact bone  Spongy Bone 40
  40. 40. 41
  41. 41. BONE Also called as Cortical bone As its name implies. . .  “cortical” bone forms the cortex or outer shell of most bones.  “compact” bone is much denser than cancellous bone. Furthermore, it is harder, stronger and stiffer than cancellous bone. The primary anatomical and functional unit of cortical bone is the osteon. 3 Distinct Layering of Compact Bone:  Circumferential lamella  Concentric lamella  Interstitial lamella Functions:  facilitates to support the whole body  protect organs  provide levers for movement 42  store and release chemical elements, mainly calcium.
  42. 42. 3 DISTINCT LAYERING OF COMPACT BONE:  Circumferential Lamellae  enclose the entire adult bone, forming its outer perimeter  Concentric Lamellae  make up the bulk of compact bone and form the basic metabolic unit of bone, the osteon  Interstitial Lamellae  interspersed between adjacent concentric lamellae and fill the spaces between them 43
  43. 43. 44
  44. 44. SPONGY BONE Also called Cancellous bone or Trabecular bone Compared to compact bone, cancellous bone has a higher surface area but is less dense, softer, weaker, and less stiff. Cancellous bone is highly vascular and frequently contains red red bone marrow where hematopoeisis occurs. The primary anatomical and functional unit of cancellous bone is the trabecula. 45