Compact (Cortical) bone Spongy (Cancellous) bone Bone tissue is a specialized form of connective tissue and is the main element of the 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. http://en.wikipedia.org/wiki/Bone_tissue 3
Functions of Bone http://en.wikipedia.org/wiki/Haematopoiesis Support: provides framework that supports and anchors all soft organs. Protection: skull and vertebrae surround soft tissue of the nervous system, and the rib cage protects vital thoracic organs. Movement: skeletal muscles use the bones as levers to move the body. Storage: fat stored in the interior of the bones. Bone matrix serves as a storehouse for various minerals. Blood Cell Formation: hematopoiesis occurs within the marrow cavities of the bones. 4
Classification of Bone Bone may be classified in several ways: 5
Where bone is preceded by a cartilagenous model that is eventually replaced by bone In a process termed endochondral ossification.
Where bone forms directly w/in a vascular, fibrous membrane.
CHEMICAL PROPERTIES of Bone “Oral Anatomy, Histology, and Embryology” 60 % Inorganic material is formed from carbonated hydroxyapatite. 25 % Organic material mainly composed of Type I collagen. The organic part is also composed of various growth factors: glycosaminoglycans, osteocalcin, osteonectin, bone sialo protein, osteopontin and Cell Attachment Factor. 7
Organic Matrix of the bone 8
Structural Elements of Bone Bone Cells Odontoblasts – are mononucleatecells that are responsible for bone formation Osteocytes – When osteoblasts become trapped in the matrix they secrete, they become osteocytes. Osteoclasts – is a type of bone cell that removes bone tissue by removing its mineralized matrix and breaking up the organic bone Bone Matrix is the intercelluar substance of bone consisting of collagenous fibers ground substances & inorganic salts Sharpey’s Fibers Are a matrix of connective tissue consisting of bundles of collagenous fibers connecting periosteum to bone Blood vessels, nerves, lymph vessels 9
Sharpey’s fibers 10
Cell types in bone Osteoblasts are mononucleatecells 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 11
RESORPTION AND FORMATION OF BONE DURING REMODELLING Resorption Reversal Formation Resting 12
Ossification 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 the development of bone from tissue or membrane, as in the formation of the skull. http://en.wikipedia.org/wiki/Ossification 13
SuturalBone Growth variable and irregularly shaped bones in the sutures between the bones of the skull. 14
ALVEOLAR BONE http://www.answers.com/topic/alveolar-bone#ixzz12ko9kyTQ 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
Development of Alveolar Bone
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
Near the end of the 2nd month of fetal life, mandible and maxilla form a groove that is opened toward the surface of the oral cavity As tooth germs start to develop, bony septa form gradually. The alveolar process starts developing strictly during tooth eruption.
Gross Morphology of Bone Morphology -is a branch of bioscience dealing with the study of the form and structure of organisms and their specific structural
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 ligament. Alveolar socket of the second premolar tooth in a bovine maxillary bone.
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
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.
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
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 commonly appears as a dense white line. Lamina Dura Radiographic appearance of alveolar bone proper as ‘Lamina Dura’
Functions of the bone
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.
Structure of the Alveolar Bone Cortical Plate – outermost part Alveolar bone proper or lamina Spongiosa – spongy bone
a) outer cortical platesb) a central spongiosac) bone lining the alveolus (bundle bone)
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
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
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 …
VascuLAR Supply of ALVEOLAR BONE
Vascular Supply of Alveolar Process Alveolar process of the maxilla Anterior and posterior alveolar arteries (branch from the maxilla and infraorbital arteries) Alveolar process of the mandible Inferior alveolar arteries (internal) Periosteal branches of submental and buccal arteries (external)
PeriodonTal disease http://en.wikipedia.org/wiki/Periodontal_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.
Histological Arrangement of Mature Bone Mature bone is composed of: Compact bone Spongy Bone http://www.physioweb.org/skeletal/bone_tissue.html 39
Compact 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. 3Distinct Layering of Compact Bone: Circumferential lamella Concentric lamella Interstitial lamella Functions: facilitates to support the whole body protect organs provide levers for movement store and release chemical elements, mainly calcium. http://en.wikipedia.org/wiki/Bone_tissue 41
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 42
Spongy Bone Also called Cancellous bone orTrabecular 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. 44