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Alveolar bone (process) Dr /Abdel-latif Galal Lecturer of oral Medicine& Periodontology  Alveolar bone (process) Cusp C R Enamel...

Alveolar bone (process) Dr /Abdel-latif Galal Lecturer of oral Medicine& Periodontology  Alveolar bone (process) Cusp C R Enamel O W Dentin N Gum Pulp Cementum R O Periodontal O ligament T S Alveolar bone Apex Alveolar bone( process) This bone is also known as the "Alveolar Process"; It includes sockets which are designed to accommodate the roots. Is a highly specialized, hard connective tissue of complex structures and functions. Alveolar bone forms the primary support structure for teeth. Alveolar bone develops from the dental follicle, the ectomesenchymal cells of the dental follicle differentiate into osteoblasts and lay down the matrix called osteoid. If the teeth are lost the alveolar process disappears ; If teeth congenitally missing a lveolar bone not developed Structural Elements of Bone : bone consist of :cells , Ground substance ,fibers and minerals. Bone Cells : Their are 4 types of cells in bone tissue: 1- Osteoprogenitor cells : These are undifferentiated mesenchymal cells in origin, they divided by mitosis to give any type of bone cells. 2- Osteoblasts : Are a mononucleated, elongated cells with basophilic cytoplasm that are responsible for bone formation ,osteoblast are responsiple for secretion of osteoid tissue which will be later mineralized by osteoblast to form bone tissue. strong alkaline phosphatase activity shown in their cytoplasm. 3- Osteocytes : When osteoblast become trapped in bone tissue, the cell bodies of osteocyte are located in lacunae. 4- Osteoclasts : They are located on the surface of bone tissue ,and responsible for resorption of bone. These are large cells multinucleated having 15-20 nuclei; Always found in concave areas know as "Howship's lacunae Derived from monocytes - macrophages Contain acid phosphatase enzyme  Chemical properties of the bone: 67 % Inorganic material Is formed from hydroxyapatite crystals. 33 % Organic material Mainly composed of Type I collagen fibers.  Functions of alveolar bone : 1. Anchors the teeth with the help of sharpy's Alveolar crest fibers. Alveolar 1. Protect the developing tooth bud. bone proper 2. Supply blood to periodontal ligaments. Supporting 3. Absorb and distribute the occlusal forces. bone Cementum Structure of alveolar bone It consist of an outer (buccal or lingual ) cortical plate , a central spongiosa , and bone lining the alveolus( alveolar bone). The cortical plate and alveolar bone meet at the alveolar crest ( usually 1.5 to 2 mm below the level of the C.E.J. of the tooth ). Physiologically the alveolar process consist of two parts: The alveolar bone proper. The supporting alveolar bone.  Alveolar bone proper This part form the inner wall of the sockets ,directly facing the roots and it’s main function is to furnish a medium for the attachment of the periodontal fibers. This part of alveolar process consist of two types of bone: 1- bundle bone 2- lamellated bone 1- bundle bone : Is the inner most type & it developed from dental follicle. Part of the alveolar bone where periodontal ligament fibers are inserted (attached).  Radiographically is more radiodense due to presence of thick bone without trabeculations and is called as "lamina dura". Alveolar bone proper has many openings for blood vessels and nerves and is called as "cribriform plate" * Lamina Dura this part is attached to 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 2- lamellated bone : It's thicker layer of lamellar bone formed of longitudinal lamellae. It's lies between the bundle bone and the supporting spongiosa. Supporting alveolar bone : Anatomically it is the bone that forms the labial and lingual covering of the alveolar bone proper. It consists of two parts - - Cortical plates (Outer and inner) - Spongy bone. Alveolar bone Cortical plates: -these are made up of compact bone & form the outer(labial or Labial cortical baccal) and inner( lingual) plates of the alveolar bone. plate lingual plate -varies in thickness in different areas , it is thicker in the Body of mandible mandible than in the maxilla ; and thicker in the premolar and molar regions than in the anteriors.  Generally greater on the lingual than on the buccal/facial In the maxilla the outer cortical plate is perforated by many small openings through which blood and lymph vessels pass. No spongy bone is found in the region of the anterior teeth of both jaws  2- spongy bone or cancellous (supporting spongiosa): It occupying the central part of the alveolar process. It fills the area between the cortical plates and the alveolar bone proper. It contains trabeculae of bone and marrow spaces. Types of spongy bone (spongiosa) Type I: The trabaculae are regular and arranged in horizontal ladder like fashion. This is seen most commonly in the mandible. Type II: Irregularly arranged delicate and numerous trabeculae. This is seen most commonly in the maxilla. The spongy bone is very thin or absent in the anterior regions of both the jaws. ✓Histologically the bone trabeculae of spongy bone include irregular medullary cavities which containing bone marrow(red). ✓This red bone marrow will be transformed into fatty marrow by age but it persist only in the distal part of the last upper molar in the tuberosity region , head of the condoyle and mandibular angle. Ossification of bone: (Also called Osteogenesis) is the natural process of bone formation ,human bones grow until about age 25 years. There are two processes resulting in the formation of normal, healthy bone tissue: 1- 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 ossification of synovial cartilage. 2- Intramembranous bone ossification The development of bone from tissue or membrane, as in the formation of the skull.  Bone resorption : occurs as three processes taking place by osteoclasts which are: 1- Decalcification of inorganic material: This is achieved by osteoclast which secreted organic acids mainly citric acid and lactic acid that increase solubility of hydroxyapatite. 2- Degradation of organic matrix : This occur by the activity of lysosomal acid protease and collagenase enzymes take place. these enzymes are secreted by osteoclasts which cause break down the collagen fibers. 3- Transport of soluble products: The soluble products will be transported to the extracellular fluid or to blood vascular system. Remodeling of alveolar bone:- Alveolar bone undergoes constant physiologic remodeling (resorption and formation)in response to external forces specially occlusal forces. Thus osteoclast cells produce bone resorption in areas of pressure on the mesial surface and osteoblast cells with new bone formed in areas of tension on the distal surface. This process of resorption and formation of bone is called bone remodeling and it is important in the orthodontic treatment. Incremental lines in bone: Resting line: these lines correspond to the resting period of osteoblast during bone formation. Reversal line: when a period of bone resorption is followed by bone formation, a dark line is seen which separates the new bone from old bone. Foramen between periodontal ligament and bone marrow Tooth root V' Periodontal rr : ♦ < r & ligament :>r Alveolar bone proper Supporting Bone bone marrow , Alveolar bone with.* * incremental >. / ne Copyright © 2006 by Mosby, Inc Age changes in alveolar bone: Brittleness due to decreased water content Sponge bone become thin trabecula , wide marrow spaces Red bone marrow become fatty Osteoporosis Alveolar crest slope distally due to mesial tilting of teeth