mechanisms of bone loss

Question 1

What is the alveolar process defined as?

Answer 1

The alveolar process is defined as that part of the maxilla and the mandibular bone that forms and supports the sockets of the teeth.

Question 2

Parts of alveolar process

Answer 2

Outer cortical plate (buccal and lingual) A central spongiosa (Cancellous bone) Bone lining the socket (bundle bone) – radiographically lamina dura

Question 3

Key functions of alveolar bone

Answer 3

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

Question 4

Role of gingival cuff

Answer 4

-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.

Question 5

Inorganic composition of bone?

Answer 5

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

Question 6

Organic composition of bone?

Answer 6

33% organic – 28% collagen and 5% non collagenous proteins such as bone sialoprotein, osteocalcin, osteopontin, growth factors and other proteins

Question 7

Describe features of osteoblasts

Answer 7

• 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.

Question 8

Describe features of osteoclasts

Answer 8

• 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.

Question 9

Where are osteoclasts usually situated?

Answer 9

resorption pits called Howship’s lacunae

Question 10

Describe the features of osteocytes

Answer 10

osteoblasts trapped in the matrix they secrete. The number of osteoblasts that become osteocyte depends on the rapidity of bone formation

Question 11

What is the bone turn over rate?

Answer 11

Bone turnover rates of 30 to 100% per year is common in developing children.

Question 12

Where does bone turnover occur in?

Answer 12

occurs in focal, discrete areas involving group of cells called BMUs (Basic multi-cellular units)

Question 13

Most important hormones in bone metabolism?

Answer 13

parathyroid hormone (PTH), 1,25-dihydroxyvitamin D, calcitonin, Oestrogen and the glucocorticoids.

Question 14

What factors in bone remodelling are closely interlinked?

Answer 14

Physiology of calcium and phosphate metabolism, formation of bone and regulation of Vitamin D, parathyroid hormone(PTH) and calcitonin

Question 15

Effect of dual action of parathyroid hormone and vit D?

Answer 15

Parathyroid hormone and Vit D actions are dual, enhancing bone resorption at high (Pharmacologic) concentrations and supporting bone formation at lower (Physiologic) concentrations.

Question 16

Role of calcitonin and oestrogen?

Answer 16

inhibit bone resorption.

Question 17

Role of glucocorticoids

Answer 17

inhibit primarily formation.

Question 18

How do hormones effecting bone work?

Answer 18

Most likely thru altering the secretion of local cytokines and growth factors.

Question 19

Factors regulation bone resorption? At a cellular level

Answer 19

• 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

Question 20

Factors regulating bone formation: cellular level

Answer 20

• Platelet derived growth factor (PDGF)
• Transforming growth factor (TGF-β)
• Heparin binding growth factors
• Insulin-like growth factor
• Bone morphogenetic proteins

Question 21

What bacterial induced local inflammatory response in the gingival soft tissue and periodontium produce?

Answer 21

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.

Question 22

What is immunopathogenesis

Answer 22

In pathologic inflammatory conditions, inflamm cell products initiate osteoclast activity and disturb balance between protective and disruptive processes

Question 23

What is immunopathogenesis termed as now ?

Answer 23

Osteoimmunology