OB P7- Bone and calcium Flashcards

1
Q

what are the functions of bone?

A
>  Skeletal :
– Protects organs
– Provides rigidity
– Allows attachment of muscles and teeth 
– Movements
>  Container for marrow   
> Ca2+ pool
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

why understand bone?

A
  • Regional differences in the mouth (Local anaesthesia)
  • Bone changes in the mouth (e.g. to extraction of teeth)
  • Orthodontic tooth movements - Osseointegration – implants
  • Bisphosphonates
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what is the bone composition?

A
60% mineral :
- Largely hydroxyapatite
25% organic :
-90% Type I collagen
- 10% grounds substance
  15% water
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

what does collagen do to bone?

A

collagen is a fibrous structural protein which gives elasticity to bone

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what are the 2 types of bone in the jaw?

A
  • Alveolar bone - contains the tooth

- Basal bone - basic structure of the jaw

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

why is fitting a lower denture difficult?

A

there is no ridge to fit the lower denture over as the bone resorbs away once teeth are removed

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

what makes a lower denture fit better/

A

2 implants inserted that the denture clips into

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

what are the two different types of bone around the tooth?

A
  • Cortical bone (compact bone - dense)

- Trabecular bone ( spongy , cancellous bone)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

why does the density and porosity affect local anaesthesia?

A

cortical bone is thin around the upper teeth and porous so anaesthetic will diffuse through

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

what layer of bone surrounds the tooth?

A

lamina dura (bundle bone - cribriform plate)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

why is it called lamina dura?

A

Due to radiographic appearmace - white ridge around teeth

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

what is the intraligamentary anaesthesia technique?

A

stick needle down PDL space between bone and tooth
inject small amount of anaesthetic -allows us to apply high pressure
(passes out of the holes and diffuses through trabecular bone and reaches apex

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

what are the 3 types of lamellae?

A
Circumferential
-Outside of most cortical bone   
Concentric
-Organised in Haversian systems / osteons   
Interstitial
- Remnants of old lamellae
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is found in the middle of the lamellae?

A

blood vessels

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

what lines are found in the lamellae?

A

cementing lines

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

what is important about osteocytes in lamellae that is different to cementocytes?

A

osteocytes have processes that go in both directions whereas cementocytes only have one process that points outwards

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

what are the two types of bone formation?

A
  • endochondral

- intramembranous

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Describe endochondral ossification.

A

Cartilage -> calcified cartilage -> bone

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Describe intramembranous ossification.

A
  • Condensation of mesenchymal cells
  • Osteoblasts – produce osteoid matrix
  • Woven bone
  • Primary osteon formation
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

what is woven bone?

A

when collagen is randomly organised

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Describe the formation of primary osteons.

A
  • connective tissue condensation around Blood vessels + advancing layer of osteoblasts laying down woven bone
  • as osteocytes advance, some surround the edge of the condensation and some advance still laying down woven bone
  • forms lamellae around the dental vessel
  • primary osteons surrounded by woven bone
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Describe osteoblasts.

A

– Mesenchymal or ectomesenchymal derived
– On bone surface (periostuem , endosteum )
– Produce osteoid matrix

23
Q

Describe osteocytes.

A
– Trapped osteoblasts
– (cf cementocytes)
– Cell processes
– Linked by gap junctions 
– Cells vital
24
Q

what are osteoclasts.

A

– Derived from haemopoietic source
• Macrophage/monocyte line
– Large multinucleate cells

25
where are osteoclasts found and what is their role?
– In Howships Lacunae: • Dissolve bone mineral – acid • Breakdown organic matrix - enzymes
26
How often is bone remodelled?
continuous
27
what occurs during the turnover of bone?
resorption and deposition
28
how often is bone completely replaced?
every 10 years: | – Keeps skeleton effectively engineered for its use – Helps maintain plasma Ca2+ levels
29
How is bone remodelled?
– Cutting cone - osteoclasts | – Filling cone – osteoblasts
30
what does bone turnover result in?
secondary osteons
31
How much calcium is in the Body?
>1Kg Ca2+ in body >99% in bones and teeth – Only 0.4% exchangeable >1% in body fluids
32
Can calcium be taken out of bone and teeth?
calcium can be taken out of bone in small amounts but NOT teeth
33
what can remove calcium from bone?
osteocytes and osteoclasts
34
what are the roles of Ca2+?
``` -Membrane permeability: > Decreases membrane permeability (esp PNa) > Decreases cell excitability > Low Ca2+ -> spontaneous APs - results in tetany - Excitation – contraction coupling - Excitation – secretion coupling - Hard tissue formation - Blood clotting - Enzyme reactions - Secretions – e.g. milk ```
35
what is quick Ca2+ regulation?
Rapid exchanges between bone and ECF
36
What is slow Ca2+ regulation?
– Intestinal absorption | – Renal excretion
37
what does the parathyroid hormone do?
- Essential for life - Release in response to falling [Ca2+]plasma - increases [Ca2+]plasma - Prevents hypocalaemia - Withdraws [Ca2+] from the bone bank
38
Describe the fast Ca2+ efflux to plasma.
– Small labile pool of Ca2+ in bone | – Involves osteocytes - osteocytic osteolysis
39
Describe the slow Ca2+ efflux to plasma.
– Bone dissolution – Shift remodelling to favour resorption – Involves osteoclasts
40
what effect does the parathyroid hormone have on the kidney?
Reduced excretion of Ca2+
41
what is caused by deficiency in the parathyroid hormone?
- Iatrogenic parathyroid gland damage - Tetany - Asphyxiation
42
what is caused by excess of the parathyroid hormone?
- Hyperplasia of PT gland - Tumours - Weak bones - Ectopic mineralisation
43
what are "C" cells on thyroid gland?
calcitonin
44
what is the role of calcitonin?
Prevents [Ca2+] plasma becoming high
45
what is the action of calcitonin?
- Reduce osteocyte activity - Reduce osteoclast activity - Reduce osteoclast numbers
46
what is essential for Ca2+ absorption In the intestine?
Vitamin D - Cholecalciferol
47
when is Vitamin D - Cholecalciferol produced?
Produced in skin in response to sunlight on a precursor
48
what is the action of vitamin D?
Increase Ca2+ absorption in the intestine
49
what does BRONJI stand for?
Bisphosphonate Related Osteonecrosis of the Jaws
50
what does MRONJ stand for?
Medication related osteonecrosis of the jaws (used now)
51
what are biphosphates used for?
– Osteoporosis – reduce fracture rates | – Bone metastases
52
how do biphosphates work?
Reduce osteoclast activity – reduce bone breakdown
53
How is MRONJ caused?
– Impaired bone turnover -> exposed bone after extraction