Lecture 3 - Bone And Tooth Structure

Question 1

Bone mineral is

Answer 1

Calcium and phosphate laid down as hydroxyapetite crystal

• gives compressive strength

Question 2

What has a high proportion of trabecular bone

Answer 2

Spine + pelvis

Question 3

What has a high proportion of cortical bone

Answer 3

Bones of arm, femur

Question 4

Bone matrix composition

Answer 4

COLLAGEN

• gives tensile strength
• type I

NON COLLAGENOUS PROTEINS

• alkaline phosphatase
• proteoglycans
• growth factors in bone matrix

BONE MINERAL

Question 5

Osteoblasts

Answer 5

• bone forming cells
• line bone surface
• active synthesis of matrix
• involved in mineralisation

Question 6

Lining cells

Answer 6

• flattened osteoblasts lining bone surface

Question 7

Osteocytes

Answer 7

• osteoblasts embedded in bone matrix
• connected by canaliculae
• involved in sensing mechanical forces
• make up 90% of bone cells and are long lived

Question 8

Bone resorbing cells: osteoclasts

Answer 8

• multinucleated giant cells
• secrete acid and proteolytic enzymes
• dissolve mineral and degrade protein
• release embedded growth factors

Question 9

Activity of osteoblasts or osteoclasts depends on

Answer 9

• number of cells formed
• activity of cells
• lifespan of cells

Question 10

3 reasons why bone turnover happens

Answer 10

• shape changes of bone
• in response to changing load
• repair of microdamage

Question 11

Osteoclast induced osteoblast differentiation

Answer 11

Osteoclast release TGFb, BMP and IGF during resorption, which induces chemotaxis, proliferation and differentiation of osteoblasts, leading to mineralization

Question 12

Osteoblast-induced osteoclast differentiation

Answer 12

Osteoblast express RANK-L on their surface

• binds to RANK ligand on a preosteoclast
• this interaction results in osteoclast differentiation
• osteoblasts can also produce osteoprotegerin to prevent this interaction

Question 13

Tooth specialized cells

Answer 13

• Ameloblast: lay down enamel, very dense matrix resistant to acid attack. Closely packed collagen and HAP crystals
• Odontoblasts: lay down dentine. Collagen fibres in dentine extend to alveolar bone
• osteoblasts and osteoclasts involved in alveolar bone remodeling

Question 14

Caries

Answer 14

Bacteria + food -> anaerobic acid release -> dissolves mineral
- also proteolytic enzymes -> break down matrix

Question 15

Assessing bone: bone densitometry

Answer 15

• assume normal mineralisation
• no osteophytes
• consider aortic calcification

Question 16

Other methods of assessing bone

Answer 16

• ultrasound
• bone biopsy - very invasive
• other: bone quality - microarchitecture/fractures/ cell death/ rates of bone turnover

Question 17

Osteoporosis

Answer 17

• low trauma fracture

- bone mineral density

Question 18

T score and Z score

Answer 18

• T score: compared with mean peak bone mass - assesses what is desirable, used to assess fracture risk
• Z score: compared with age and gender matched controls - assesses what is expected. USed to determine if bone mass is unusually low

Question 19

T score and disease category

Answer 19

Normal: -1 and above
Osteopenia: -1- - 2.5
Osteroporosis: