mechanisms of bone loss Flashcards
(23 cards)
What is the alveolar process defined as?
The alveolar process is defined as that part of the maxilla and the mandibular bone that forms and supports the sockets of the teeth.
Parts of alveolar process
Outer cortical plate (buccal and lingual) A central spongiosa (Cancellous bone) Bone lining the socket (bundle bone) – radiographically lamina dura
Key functions of alveolar bone
Houses the roots of the teeth
•Anchors the roots of the teeth to the bone with the help of insertion of terminal periodontal ligament fibres known as Sharpey’s fibres
•Helps to absorb and distribute occlusal forces generated during mastication /tooth to tooth contact
•Provides blood supply to the periodontal ligament
Role of gingival cuff
-critical in maintaining the relationship between the gingiva and the tooth,
-protecting the deeper tissues of the periodontal ligament & alveolar bone
-numerous cell types act together in a coordination: maintain the status quo in terms of connective tissue and alveolar bone integrity.
Inorganic composition of bone?
67% inorganic – in the form of hydroxyapatite (Ca10 [PO4]6[OH]2) The inorganic component is in the form of small plates, most of which are interspersed between collagen fibrils
Organic composition of bone?
33% organic – 28% collagen and 5% non collagenous proteins such as bone sialoprotein, osteocalcin, osteopontin, growth factors and other proteins
Describe features of osteoblasts
- Mononucleated cells
- synthesise the organic matrix of the bone –rich in alkaline phosphatase,
- secretory products= lots of type I collagen, little amount of type V collagen, proteoglycans & several non collagenous proteins.
Describe features of osteoclasts
- Multinucleated, larger in size
- resorption of the bone; rich in acid phosphatase and other lysosomal enzymes.
- proton pump associated with ruffled border and pumps hydrogen ion into the sealed compartment adjacent to the bone surface where active resorption is taking place.
Where are osteoclasts usually situated?
resorption pits called Howship’s lacunae
Describe the features of osteocytes
osteoblasts trapped in the matrix they secrete. The number of osteoblasts that become osteocyte depends on the rapidity of bone formation
What is the bone turn over rate?
Bone turnover rates of 30 to 100% per year is common in developing children.
Where does bone turnover occur in?
occurs in focal, discrete areas involving group of cells called BMUs (Basic multi-cellular units)
Most important hormones in bone metabolism?
parathyroid hormone (PTH), 1,25-dihydroxyvitamin D, calcitonin, Oestrogen and the glucocorticoids.
What factors in bone remodelling are closely interlinked?
Physiology of calcium and phosphate metabolism, formation of bone and regulation of Vitamin D, parathyroid hormone(PTH) and calcitonin
Effect of dual action of parathyroid hormone and vit D?
Parathyroid hormone and Vit D actions are dual, enhancing bone resorption at high (Pharmacologic) concentrations and supporting bone formation at lower (Physiologic) concentrations.
Role of calcitonin and oestrogen?
inhibit bone resorption.
Role of glucocorticoids
inhibit primarily formation.
How do hormones effecting bone work?
Most likely thru altering the secretion of local cytokines and growth factors.
Factors regulation bone resorption? At a cellular level
• Interleukin – 1 (IL-1)
•Interleukin – 6 (IL-6)
•Tumour necrosis factor (TNF- α)
•PGE -2 (Prostaglandins E – 2) and arachidonic acid metabolites.
•Glucocorticoids / sex steroids such as androgens
Factors regulating bone formation: cellular level
• Platelet derived growth factor (PDGF)
• Transforming growth factor (TGF-β)
• Heparin binding growth factors
• Insulin-like growth factor
• Bone morphogenetic proteins
What bacterial induced local inflammatory response in the gingival soft tissue and periodontium produce?
The resultant influx of inflammatory cells produces a host of cytokines, for example, PGE2, IL-1, and RANK-L, that promote resorption through osteoclasts, the primary bone resorbing cell.
What is immunopathogenesis
In pathologic inflammatory conditions, inflamm cell products initiate osteoclast activity and disturb balance between protective and disruptive processes
What is immunopathogenesis termed as now ?
Osteoimmunology
