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Alveolar Bone Structure and Function
- 1. 1 ALVEOLAR BONE Dr. Mrinalini Agarwal Senior Lecturer MDS- Department of Periodontology Subharti Dental College & Hospital Swami Vivekanand Subharti Universiy Meerut, U.P.
- 2. What is bone??????? Bone is a specialized mineralized connective tissue of the body. 2
- 4. C). Based on Histology 4 Mature bone Immature bone/ woven bone Compact bone/ cortical bone Cancellous bone/Spongy bone
- 5. The normal periodontium provides support necessary to maintain tooth in function. 5
- 6. It is the part of maxilla and mandible that forms and supports the sockets of teeth .( alveoli) ALVEOLAR PROCESS CEMENTUM ALVEOLAR BONE PDL ATTACHMENT APPARATUS 6
- 7. Alveolar process develop and undergo remodeling with tooth formation and eruption ,they are tooth dependent Structures. Schroeder H. , 1991 7
- 8. FUNCTIONS 1. Houses roots of teeth. 2. Helps to move teeth for better occlusion. 3. Helps to absorb and distribute occlusal forces.zz 4. Houses and protects developing permanent teeth, while supporting primary teeth. 5. Supplies vessels to PDL 6.Organizes eruption of permanent and primary teeth. 7.Acts as a reservoir for ions 8.Provide attachment to muscles 8
- 9. .zz 9.The most important biological property of bone is the plasticity which allow it to remodel according to the functional demand placed on it… 9
- 10. STRUCTURE OF ALVEOLAR BONE ALVEOLAR BONE ALVEOLAR BONE PROPER LAMELLATED BONE BUNDLE BONE SUPPORTING ALVEOLAR BONE CORTICAL PLATE SPONGY BONE 10
- 11. Alveolar Bone MANDIBLE WITH TEETH REMOVED TO DEMONSTRATE PARTS OF ALVEOLAR BONE: A-OUTER ALVEOLAR PLATE B-INNER ALVEOLAR PLATE C-CRIBRIFORM PLATE D-INTERDENTAL SEPTUM E-INTERRADICULAR SEPTUM 11
- 12. Thin lamella of bone that surrounds the root of teeth. Gives attachment to principal fibers of PDL Alveolar bone proper 12
- 13. Thin radio opaque shadow bounding the sound tooth socket. Wider and more dense in teeth with heavy occlusion. Lamina dura absent in case of diseased tooth. 13
- 15. 15
- 16. Lamina Dura Radiographically ,bundle bone referred to as lamina dura. 16
- 18. Thickest in mandibular PM buccal side. Thinner in maxilla than mandible. Anterior region of both jaws,supporting bone is very thin. 18
- 19. SPONGY BONE Fills the space between cortical plate and alveolar Bone proper Consists of large slender spicules, Trabeculae. Marrow spaces are large 19
- 20. SPONGY BONE Type I Type II RADIOGRAPHICALLY TYPE II TYPE I 20
- 23. BONE MEMRANES Periosteum OUTER CONDENSED FIBROCOLLAGEN LAYER. Outer fibrous layer Inner osteogenic layer Endosteum Delicate CT membrane covering internal surfaces . Covers trabeculae of spongy bone 23
- 25. INTERCELLULAR MATRIX ORGANIC 35% COLLAGEN 88% -89% NON COLLAGENOUS PROTEIN 11%- 12% INORGANIC 65% HYDROXYAPATITE CRYSTALS 25
- 26. MATRIX COMPONENTS Formed from a scaffold of interwoven collagen fibers. Uniform plate like crystals of carbonated hydroxyapatite (Ca10[PO4]6[OH]2 are deposited. 26
- 27. INORGANIC COMPONENT Principally composed Of ions- calcium,phosphate,hydroxyl, carbonate,citrate. Trace amounts of Na,Mg,F. GLIMCHER MJ. 1990 27
- 28. ORGANIC COMPONENT 95% TYPE I COLLAGEN TYPE V COLLAGEN (<5%) present TYPE III & TYPE XII also present 28
- 29. Comprises 11 -12 % of total organic component Glycoprotein – 6.5%- 10% Proteoglycans – < 10% Sialoprotein- 0.35% Lipids – 0.4% 29
- 30. In the maxilla the bone is usually thicker on the palatal than on the buccal side. • Mandible in general is thicker than the maxilla. • Alveolar bone varies in thickness from one jaw to the other and in the same jaw from one region to another. 30 OSSEOUS TOPOGRAPHY
- 31. In mandible incisor and premolar region the bone is thicker on the lingual side, however in the molar region the bone is thicker on the buccal side 31 • The height and thickness of the facial and lingual bony plates are affected by the - • alignment of the teeth • angulation of the root to the bone • occlusal forces
- 32. BONE CELLS OSTEOGENIC CELLS 1)OSTEOPROGENITOR CELLS 2) OSTEOBLASTS 3)OSTEOCYTES 4) BONE LINING CELLS OSTEOLYTIC CELLS OSTEOCLASTS 32 CELLULAR ELEMENTS- BONE CELLS
- 33. Bone marrow Hematopoietic stem cell Osteocyte Osteoblast Lining cell osteoclast Monocyte/macrophage stem cell Mesenchymal progenitor cell Osteo chondrogenic progenitor cell Osteoclast progenitor cells Mesenchymal stem cell 33
- 34. Eventually give rise to OSTEOBLASTS. Fibroblast like cells, elongated nucleus and few organelles. Stem cells of mesenchymal origin. OSTEOPROGENITOR CELLS 34
- 35. OSTEOBLASTS • Mononucleated cells, synthesize & secrete collagenous and non collagenous bone matrix protein. Plump, cuboidal cells (when active). Flattened cells (when inactive). • Exhibits high level of alkaline phosphatase. • Arise -Pluripotent stem cells, mesenchymal origin 35
- 36. Functions of osteoblasts • Formation of new bone via synthesis of proteins. • Regulation of bone remodeling and mineral metabolism. • Secretion of osteoid and mineralization of bone. • Secretion of type I collagen, osteocalcin. • Small amount of Type V collagen, osteonectin, osteopontin, OPG, RANKL,BMP 36
- 37. BONE LINING CELLS Osteoblasts flatten and extend along the bone surface Contain very few organelles, but retain gap junctions with osteocytes. 37
- 38. Osteoblast that become entrapped in the matrix they secrete- osteocytes More no. of osteocytes in woven and repairing bone. OSTEOCYTES 38
- 39. Osteocytic lacunae Canaliculi – narrow extensions Canaliculi penetrate the bone matrix and permit the diffusion of nutrients ,gases, waste products between osteocytes and blood vessels. Osteocytes also sense change in environment and send signals that affect response of other cells involved in bone remodeling. Maintains bone integrity and vitality. Burger et al. 1995; Marotti 2000 39
- 40. OSTEOCLASTS Derived from the Greek words meaning “ bone and broken “ Multinucleated giant cells,40- 100 μm. diameter. Lie in resorption bays “ HOWSHIP’S LACUNA” reflecting their activity and mobility during active resorption. 15-20nuclei closely packed. Rodan 1992;Vaananen 2008 40
- 41. Adjacent to tissue surface, cell membrane of osteoclast is thrown into several deep folds forming RUFFLED BORDER. Cathepsin containing vacuoles and vesicles near ruffled border indicate resorptive activity of theses cells. ACTIVATED OSTEOCLAST 41
- 42. Inferior and superior alveolar arteries for mandible and maxilla, respectively . BLOOD SUPPLY TO ALVEOLAR BONE 42
- 43. • Labial aspect of maxillary incisors, canines & premolars is innervated - superior labial branches from the infraorbital nerve. Buccal aspect of maxillary molar regions innervated - branches from the posterior superior dental nerve. Palatal aspect by greater palatine nerve, except for incisor which is innervated by long sphenopalatine nerve. NERVE SUPPLY 43
- 44. • Lingual aspect in mandible - lingual nerve • Labial aspect of mandibular incisors & canines - mental nerve. • Buccal aspect of the molars - buccal nerve. • The nerve enters the periodontal ligament through Volkmann's canal of alveolar bone 44
- 45. BONE RESORPTION Is the removal of mineral and organic components of extracellular matrix of bone under the action of osteolytic cells. 45
- 46. SEQUENCE OF EVENTS FORMATION OF OSTEOCLASTS ALTERATION IN OSTEOCLASTS REMOVAL OF HA DEGRADATION OF ORGANIC MATRIX & REMOVAL OF PRODUCTS 46
- 47. BONE REMODELLING Bone formation and bone resorption are processes that are “COUPLED “ Osteoclasts resorb an area of bone & osteoblasts are signaled to come in and form the bone Raisz ,2005 47
- 48. Bone remodeling is a major pathway by which bone 1) Changes shape 2) Resists occlusal forces 3)Repairs wounds 4)Maintains Ca & P Homeostasis 48
- 50. REVERSAL LINE : cement line which is a thin layer of glycoprotein comprising of bone sialoprotein & osteopontin. Acts as a cohesive mineralized layer between the old bone & new bone to be secreted 50
- 51. RESTING LINES : Periodic bone apposition alternating with periods of quiescence . Denotes period of rest during bone formation. 51
- 52. CUTTING CONE : Also called as resorption tunnel. FILLING CONE : Area where active bone formation takes place. 52
- 53. FACTORS REGULATING BONE REMODELLING • LOCAL FACTORS : • 1) Functional requirement of tooth. • 2) age related changes in bone cells • SYSTEMIC FACTORS: • 1)PTH • 2)CALCITONIN • 3)VIT D metabolites. • 4)Growth factors- TGF α ,TGF β 53
- 54. ALVEOLAR BONE IN IMPLANT DENTISTRY • Misch,1988 - bone can be classified in to four macroscopic decreasing density group • 1. Dense Compact (D-1) • 2. Porous Compact (D-2) • 3. Coarse Trabecular (D-3) • 4. Fine Trabecular (D-4) 54
- 55. 55 Dr. Mrinalini Agarwal Email id: mrinaliniagarwal1@gmail.com
Editor's Notes
- It makes up the body of skeleton and is one of the hardest structures of the body. It possess certain degree of toughness and elasticity.
- Compact bone also c/a cortical bone ,contains tightly packed osteons or haversian sytsems,also c/a lamellar bone as bone mass arranged in layers. Spongy bone has honey comb lyk struc.large marrow cavities. woven bone fist formed bone, irregularly arranged collagen fibres.seen in alv bone and healing #
- It consists of 4 principal components : gingiva, pdl ,cementum , and alveolar bone. All these components function as a single unit.
- Gradually diminishes in height with loss of teeth.
- Increased radiopacity due to presence of thick bone without trabeculations that the x rays must penetrate and not due to any increased mineral content .
- Contains fewer fibrils in inter cellular sub than lamellated bone and hence appears dark in h&e stained sections . Mostly seen in areas of recent bone apposition. Lines of rest are also seen .
- SURROUNDS THE alveolar bone proper and gives support to the socket. CONSISTS of compact bone and form outer and inner plates of alv process. Spongy bone fills the area btwn the cortical plates and alv bone proper.
- in the max cortical bone is perforated by many small openings through which blood and lymph vessels pass. Spongy bone is absent in anterior region and cortical bone is fused with alveolar bone proper.
- TYPE I- INTERRADICULAR AND INTRDENTAL TRABECULAE ARE HORIZONTAL AND REGULAR IN STEP LADDER LIKE ARRANGEMENT. MOSTLY IN MANDIBLE. TYPE II- IRREGULARLY ARRANGED,NUMEROUS DELICATE INTERDENTALAND INTERRADICULAR ARRANGEMENT OF TRABECUAE. MORE COMMON IN MAX. In max. trabeculae are less prominent because of proximity of nasal cavity & max sinus.
- Both the cribriform plate and cortical plate are COMPACT BONE separated by spongy bone. Lamellae arranged in parallel layers surounding bony susrface –circumferential Deep to it lamellae arranged in small concentric layers –concentric Btwn osteons interstitial lamellae that are remenants of osteon left behind during remodeling.
- Havesian canal –central vascular canal Adjacent haversian canal interconnected by VOLKMANS CANAL. These are channels that contain blood vessels ,creating a rich vascular network.
- Outer aspect of compact bone is surrounded by condensd fibrocollagen layer. Double-layered protective membrane, outer layer is fibrous and inner layer contains bone cells , their precursors. supplied with nerve fibers, blood, and lymphatic vessels entering the bone via nutrient foramina.
- BONE is a connective tissue composed of cells ,fibers & ground substance. .
- The intercellular substance of bone consists of inorganic & organic substance. The inorganic par is composed of bone minerals. i.e. the HA crystals. While the oraganic part also known as otsteoid is made up of colaagenous and non- collagenous proteins.
- The bone matrix is formed from..
- Type I collagen(>95%) is the principal collagen in mineralized bone together with Type V (5%) forms heterotypic fibre bundles that provide the basic structural integrity of connective tissue. Type III and XII fibres are also present. Sharpey’s fibres contain type iiiand I TYPE XII IS expressed under conditions of mechanical strain. In woven bone fibers are interwoven with great amount of interfibrillar space, while in mature bone fibers are arranged in organized sheets, with little interfibrillar space.
- Non collagenous protein comprise of remaining 10% of the total organic content of bone matrix. Most are endogenous protein produced by bone cells while some like albumin are derived from other sources like blood and become incorporated in bone matrix during osteosynthesis. Bone proteoglycans. Diagrammatic representation of the major proteoglycans in bone matrix are shown. All are characteristically chondoitin sulfate proteoglycans (CS-PGs) with one or more chondroitin sulfate glycosaminoglucuronoglycan side chain (green) attached to a single protein core. Biglycan and decorin belong to a family of small leucine-rich proteins and have similar structure; the leucine-rich segments shown as boxes. At the C-terminus are N-linked polysaccharides and a cystine bridge (yellow) linking a terminal loop. The protein core of chondroitin sulfate proteoglycan III is acidic and binds to bone mineral crystals (HA), but its structure is unknown. The large versican-like molecule is present in the unmineralized bone matrix.
- Core binding factor 1 also called as “ OSTEOGENIC MASTER GENE “s essential for osteoblast differentiation and bone formation.
- Most active secretory cells of bone.
- OPG IS A potent inhibitor of osteoclast formation. RANKL is a membrane bound TNF , that is expresseD by osteoblasts .its presence is vital in osteoclast differentiation.
- When bone is not forming , cover most but not all quiescent bone surfaces decreased protein secretion relative paucity of organelles Quiescent surfaces are known to be a primary site of mineral ion exchange between blood and adult bone.
- The number of osteoblasts that become osteocytes depend upon the rapidity of bone formation.
- Within the matrix osteocytes decrease in size and create space around them called as lacunae. Narrow extensions of these lacunae form channels called canaliculi. Osteocytic processes are present within them. Osteocytes possess ellipsoid cell body with oval nucleus. Contain few organelles bjt enough RER and golgi suggesting that these cells are capable of keeping bone matrix in good state of repair.
- Ruffled border is thesite of ion transport +protein secretion. CLEAR ZONE- CONTAINS NO ORGANELLES SEALING ZONE : Peripheral region of apical membrane is tightly juxtaposed to the matrix. BASOLATERAL MEMBRANE : MAJOR SITE FOR RECEPTION AND INTEGRATION OF REGULATORY SIGNALS
- reaches PDL from three sources; apical vessels, penetrating vessels from the alveolar bone and anastomosing vessels from gingiva.
- Alteration in osteoclasts- formation of ruffled border, osteoclasts arrive at the resorption site and attach at the sealing zone by cell membrane proteins INTEGRIN αVβ3. SEALING ZONE CREATES isolated acidic microenvironment by action of protein pump. Decreased ph 2.5 -3.5 im resorption space . Leads to demineralization of bone and exposes organic matrix. Degradation of organic matrix b cathepsin K ,COLLAGENOLYTIC ENZYME AND MMP ,ACID PHOSPHATASE. Removal of products by endocytosis into osteoclasts ,packed in vesicles and by exocytosis in extracellular space away from bone.
- BONE IS HIGHLY DYNAMIC c.t. with the capacity to remodel continuously. Osteoblasts and osteoclasts are the major effectors in turnover of bone matrix.
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- Bone remodeling. Resorption -when osteoclasts resorb bone mineral and matrix.osteoclasts tunnel into bone surface for 3 wks. Reversal --Mononuclear cells prepare the resorbed surface for osteoblasts, Formation- osteoblasts generate newly synthesized matrix as they differentiate. Matrix mineralization and the differentiation of some osteoblasts into osteocytes completes the remodeling cycle.
- It marks the limit of bone erosion prior to the formation of osteon. The line is highly irregular and formed from scalloped outline of howship’s lacunae.
- Differs from reversal line in more regular appearance.