ALVEOLAR BONE, composition, functions.pptx

The ppt covers entire alveolar bone

1. ALVEOLAR PROCESS

2. PURPOSE STATEMENT Student should understand : Structure, composition and role of alveolar process as part of supporting structures of periodontium Relation of alveolar process with other supporting structure of the periodontium

3. LEARNING OBJECTIVES Sr no LO Domain Level 1 Explain parts of alveolar process Cognitive Must know 2 Explain cells and intercellular matrix of alveolar bone Cognitive Must know 3 Explain composition of alveolar bone Cognitive Must know 4 Explain remodelling of alveolar bone Cognitive Must know 5 Explain Fenestration and dehiscence Cognitive Must know

4. Sr no Learning Objective Domain Level 6 Explain development of alveolar bone Cognitive Must know 7 Explain physiological mesial migration Cognitive Must know 8 Explain effect of external forces on alveolar bone Cognitive Must know

5. Definition: Alveolar process is the portion of maxilla and mandible that Forms and supports the tooth sockets (alveoli) Morphology: Depends on Size Shape Function of teeth INTRODUCTION

6. DEVELOPMENT Intramembranous ossification within the ectomesenchyme surrounding the developing tooth. First formed- Woven bone Lamellar bone As the tooth root forms & surrounding tissues develop, alveolar bone merges with basal bone.

7. FUNCTIONS Protection- Forces on tooth Attachment- Insertion of PDL fibers Support- Support for tooth roots Shock absorber- Forces to underlying tissues, tooth protection from direct stress or tension

8. STRUCTURE 1. Alveolar Bone Proper ( Cribriform plate ) Many foramina perforate it. Bundle Bone- Provides attachment to Sharpey’s fibers Lamina dura - Thin radio-opaque line surrounding roots of teeth

9. 2. Supporting Alveolar Bone- Encircles alveolar bone & provides support to tooth socket Cortical Plates- Compact bone- Outer and inner plates Spongy Bone- Cancellous bone- Between alveolar bone proper and cortical plates 3. I nterdental septum Cancellous supporting bone enclosed within compact bone

10. Distance between crest of alveolar bone and CEJ: Young adult : 0.75 – 1.49 mm (1.08 mm avg ) Increases with age: 2.81 mm average Mesio -distal & facio -lingual dimensions & shape of interdental bone is governed by: Size and convexity of crowns of two approximating teeth Position of teeth Degree of eruption

11. SOCKET WALL Consist of Dense lamellated bone arranged in haversian system Bundle bone Bundle bone Bone adjacent to PDL with grater no of S harpey’s fibers Characterized by thin lamellae arranged in layer with Intervening appositional lines It is localized within alveolar bone proper

12. In addition bones of jaw includes basal bone Facial and lingual portion of socket is formed mostly by compact bone Cancellous bone surrounds lamina dura in Apical, apicolingual and interradicular areas

13. OSSEOUS TOPOGRAPHY Normally- Bone contour confirms to the prominence of the roots. Labial version- Margin of labial bone is located farther apically Lingual version- Facial bony plate is thicker than norma l

14. COMPOSITION Cellular components Osteoclasts Osteoblasts Osteocytes Extracellular matrix O rganic 35% Inorganic 67%

15. EXTRACELLULAR MATRIX Inorganic- Calcium, phosphate, hydroxyl, carbonates, citrates, traces of sodium, magnesium and fluorine Organic- Collagen (28%)- Mainly type I, type III, type V, type XII and type XIV Non- collagenous proteins (5%)- Osteonectin , osteopontin , bone sialoprotein , oesteocalcin , bone proteoglycan, biglycan , bone proteoglycan II decorin and BMPs.

16. Osteoblasts Cuboidal, elongated Produce organic matrix of bone Produce type I collagen and non-collagenous proteins Produce cytokines & growth factors Functions Synthesizing organic matrix Cell to cell communication Maintenance of bone matrix cells

17. Osteocytes Enclosed within space called lacunae Extend processes into canaliculi Flattened, elongated, spindle shaped cells

18. Osteoclasts Multinucleated giant cells Oval, club shaped Found in Howship’s lacunae Enzymes released- Acid phosphatase, arylsulfatase , B glucoronidase , cathepsin B & L, TPA, MMP-1, lysozomes .

19. Forms an anastomising system Brings oxygen and nutrients to osteocytes through blood Removes metabolic waste products Haversian system (osteons) Found primarily in Outer cortical plate Alveolar bone proper Brings vascular supply to bone too thick to be supplied by only surface vessels Canaliculi HISTOLOGY

20. Periosteum : Blood vessels branch extensively and travel through periosteum Endosteum : Lies adjacent to marrow vasculature Bone growth: Occurs by apposition of an organic matrix

21. COMPOSITION Calcium Phosphate Hydroxyl Carbonate Citrate Sodium Magnesium Fluorine Other ions Hydroxyapatite crystals Inorganic matter (two third) collagen Non- collagenous compounds Cell adhesion proteins Paracrine factors Type-I (90%) Osteocalcin Osteo pontin Cytokines Osteonectin Bone sialo protein Chemo kines Bone morphogenic proteins Growth factors Phospho proteins proteoglycans Organic matter ( one third)

22. REMODELLING Remodelling is the major pathway of bony changes in Shape Resistance to forces Repair of wound Calcium and phosphate homeostasis in body Regulation of bone remodelling Involves hormones and local factors

23. Systemic factors: Parathyroid hormone Calcitonin Vitamin D3 Local factors: Prostanoids Lipoxygenase metabolites IL-1 IL-6 TNF-alpha & beta

24. Growth factors: TGF- alpha & beta EGF PDGF Bacterial factors: LPS Lipoteichoic acid Peptidoglycans Bone is remodelled throughout life by bone resorption and bone deposition

25. Sequence of events (Ten C ate) Osteoclasts get attached to mineralized surface of bone PP’s action creates sealed acidic environment causing demineralization of bone & exposure of organic matrix Organic matrix breaks down into amino acids Mineral ions & amino acids gets sequesters within the osteoclasts

26. Coupling

27. CANCELLOUS PORTION OF ALVEOLAR BONE Consist of trabeculae which encloses marrow spaces Matrix of trabeculae consist of lamellae seperated by Incremental and resorption lines which indicate previous bone activity Predominantly in: Interradicular bone Interdental space Small amount: Facially and Lingually except in palate Maxilla contains more cancellous bone than mandible

28. BONE MARROW Red hematopoeitic marrow: Present in all bones in new born and embryo Adults: Ribs Sternum Vertebrae Skull Humerus Foci of red marrow ocassionally seen in jaws: Maxillary tuberosity Maxillary and mandibular premolar areas Mandibular symphysis Ramus angle Fatty /yellow inactive marrow: Present in adults

29. PERIOSTEUM AND ENDOSTEUM Periosteum : covers outer surface of bone Inner layer: Composed of osteoblasts surrounded by osteoprogenitor cells Have potential to differentiate into osteoblasts Outer layer: Rich in blood vessels and nerves Contains fibroblast and collagen fibers Endosteum : tissue lining internal bone cavities Composed of single layer of osteoblasts and sometimes Small amount of connective tissue Inner layer: Osteogenic Outer layer: fibrous

30. FENESTRATION AND DEHISCENCE Fenestration: Isolated areas in which root is denuded of bone and root surface is covered by periosteum and overlying gingiva Marginal bone is intact

31. Dehiscence: Denuded areas extend through marginal bone More often on facial bone & anterior teeth Frequently bilateral Causes : not clear Predisposing factors: Prominent root contour Malposition Labial protrusion of root combined with thin bony plates

32. Detection Methods Tactile method Bone sounding/ Transgingival probing Radiographs

33. Clinical importance Root exposure Mucogingival surgery Gingival grafting Abutment tooth loss

34. DEVELOPMENT OF ALVEOLAR PROCESS Osteoblast produce matrix vesicles which contains enzymes Start nucleation of HA crystals Crystals grows & coalesce To form bone nodules Alveolar bone develops from its own dental follicle After root formation alveolar bone merges with basal bone Neural crest ectomesenchyme forms alveolar bone &basal bone Mandibular basal bone begin mineralization at exit of mental nerve from mental foramen Maxillary basal bone begins mineralization at exit of infraorbital nerve from infraorbital foramen

35. SUMMARY Alveolar bone is an important component of periodontium It provides attachment to S harpey’s fibers and manages occlusal forces It has regenerative capacity Its remodelling capacity allows othodontic treatment

36. APPLIED ASPECT Biologic plasticity of bone that enables in moving teeth without disrupting the relationship to alveolar bone Increased occlusal forces may cause TFO therefore etiology of TFO shoud be removed as soon as possible Abnormalities of remodeling in metabolic and inflammatory bone disorders

37. EXPECTED QUESTIONS LAQ: Describe in detail role of alveolar bone in health and periodontal disease SAQ: Fenestration and dehiscence Write briefly about alveolar bone

38. REFERENCES Carranz’s clinical periodontology Jan Lindhe clinical periodontology and implant dentistry