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OB > Periodontium L7-9 > Flashcards

Periodontium L7-9 Flashcards

1
Q

Functions of bone (x3)

A
  1. Skeletal - protects organs; provides rigidity; allows attachment of muscles and teeth; movements
  2. Container for marrow
  3. Calcium pool
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2
Q

How is bone involved in dentistry? (x5)

A
  1. Regional differences in the mouth - local anaesthesia
  2. Bone changes in the mouth - to extraction of teeth
  3. Orthodontic tooth movements
  4. Osseointegration - implants
  5. Biphosphonates
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3
Q

Composition of bone

A

60% mineral (largely hydroxyapatite); 25% organic substance; 15% water

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4
Q

Breakdown of organic substances in bone

A

90% Type I collagen

10% ground substance

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5
Q

Which bone is resorbed when the tooth is extracted?

A

Alveolar bone is resorbed

Basal bone stays

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6
Q

Is the alveolar bone or the basal bone more suited for placement of dentures?

A

Alveolar bone - provides stability

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7
Q

What is the outer layer of bone?

A

Cortical / Compact bone

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8
Q

What is the inner layer of bone?

A

Trabecular bone / Spongy / Cancellous bone

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9
Q

Name the 3 types of lamellae

A
  1. Circumferential lamellae
  2. Concentric lamellae
  3. Interstitial lamellae
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10
Q

Describe circumferential lamellae

A

Outside of most cortical bone; near the surface

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11
Q

Describe concentric lamellae

A

Organised in Haversian systems/osteons; around a vascular core

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12
Q

Describe interstitial lamellae

A

Remnants of old lamellae

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13
Q

Name the 2 types of bone formation

A
  1. Endochondral ossification

2. Intramembranous ossification

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14
Q

What is endochondral ossification?

A

Cartilage –> Calcified cartilage –> Bone

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15
Q

What is intramembranous ossification?

A
  • Condensation of mesenchymal cells
  • Osteoblasts - produce osteoid matrix
  • Woven bone
  • Primary osteon formation
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16
Q

Role of osteoblasts

A

Produces osteoid matrix which then mineralizes

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17
Q

What are osteocytes?

A

Trapped osteoblasts that are linked together by gap junctions

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18
Q

Where can osteoclasts be found?

A

In howships lacunae

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19
Q

Role of osteoclasts (x2)

A
  1. Dissolves bone mineral - acid

2. Breakdown of organic matrix - enzymes

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20
Q

Describe the roles of calcium in the body (x7)

A
  1. Membrane permeability - decreases membrane permeability; decreases cell excitability; low calcium results in tetany
  2. Excitation-contraction coupling
  3. Excitation-secretion coupling
  4. Hard tissue formation
  5. Blood clotting
  6. Enzyme reactions
  7. In secretions - e.g. milk
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21
Q

Mechanism of fast regulation of calcium

A

Rapid exchanges between bone and extracellular fluid

22
Q

Mechanisms of slow regulation of calcium (x2)

A
  1. Intestinal absorption

2. Renal excretion

23
Q

When is the parathyroid hormone (PTH) released?

A

PTH is released in response to falling calcium level in plasma, increasing calcium levels by withdrawing calcium from the bone bank to prevent hypocalaemia.

24
Q

Describe the regulation of calcium levels by PTH

A
  1. Fast calcium efflux to plasma from the small labile pool of calcium in bone - involves osteocytes - osteocytic osteolysis
  2. Slow calcium efflux to plasma, involving bone dissolution - shifts remodelling to favour resorption and involves osteoclasts
  3. Acts on kidneys to reduce excretion of calcium
25
Q

Describe the regulation of calcium levels by calcitonin

A 
"C" cells act on thyroid gland and prevents calcium plasma levels from becoming high.
Actions:
- Reduce osteocyte activity
- Reduce osteoclast activity
- Reduce osteoclast numbers
26
Q

How does Vitamin D help in the regulation of calcium levels?

A

It increases absorption of calcium in the intestines

27
Q

Name a condition impacting the bones related to dentistry caused by medicines

A

Biphosphanates Related Osteonecrosis of the Jaws (BRONJ)

- caused by consumption of biphosphanates

28
Q

What are biphosphanates used for? (x2)

A
  1. Osteoporosis - reduce fracture rates

2. Bone metastases (secondary tumours in bone)

29
Q

Define tooth eruption

A

Tooth eruption is the movement of a tooth from its developmental position in the jaw to its functional position in occlusion in the mouth

30
Q

What are the two types of eruption?

A

Passive and active

31
Q

What is active eruption?

A

Bodily movement of the tooth

32
Q

What is passive eruption?

A

Uncovering of the tooth by apical gingival migration

33
Q

Describe the pre-eruptive movement of a tooth

A

The permanent successor starts off from a lingual/palatal position and move between the roots of its deciduous predecessors.

34
Q

What are the stages of eruption?

A
  1. Pre-eruptive movements
  2. Eruptive movements
  3. Bloodless eruption
  4. Deciduous exfoliation
35
Q

List the theories for tooth eruption (x7)

A 
PUSH:
1. Root formation
2. Pulp proliferation
3. Bone formation
4. Fluid pressure
PULL:
1. Collagen contraction
2. Fibroblast contraction
3,. Fibroblast migration
36
Q

Discuss evidence for and against root formation providing a “push” force for tooth eruption

A

for: Roots normally form during eruption
against:
- some teeth have eruption paths longer than root length (e.g. canines)
- impacted teeth with fully formed teeth can erupt of impaction released (wisdom teeth)

37
Q

Discuss evidence for and against bone formation providing a “push” force for tooth eruption

A

for: Bone forms under an erupting tooth
against: root is resected as teeth erupts and bone fills in as tooth moves away

38
Q

Discuss evidence for and against hydrostatic pressure providing a “push” force for tooth eruption

A

for:

  • periodontal vasculature
  • cervical sympathetic stimulation: vasoconstriction; cessation of eruption; reversible on cessation
  • sympathectomy: vasodilation - increased tissue pressure; increase eruption rate
    against: root resected rodent incisor erupt normally
39
Q

Which is the most plausible “push” factor for tooth eruption?

A

Hydrostatic pressures

40
Q

Which is the most plausible “pull” factor of tooth eruption?

A

PDL Fibroblasts

41
Q

Discuss evidence for and against collagen contraction providing a “pull” force for tooth eruption

A

for: collagen can contract in vitro
against: no proof that collagen contracts in vivo (i.e. in the mouth)

42
Q

Discuss evidence for and against fibroblast migration/contraction providing a “pull” force for tooth eruption

A

for: fibroblasts show motility when cultured and they move cervically on eruption
against: PDL fibroblasts do not have organelles for motility and there is no evidence that they can exert eruptive forces

43
Q

Describe the process of bloodless eruption

A

REE proliferates –> Fusion of oral epithelium and REE –> Epithelial cell death –> Epithelial pathway –> REE forms junctional epithelium

44
Q

Describe the process of deciduous exfoliation

A

Deciduous tooth must be resorbed to facilitate successional eruption. The pressure of tooth on bone results in resorption. Deciduous teeth are resorbed by odontoclasts (multinucleated osteoclast like cells derived from monocytes)

45
Q

Compare the tooth movements on loading between the horizontal and vertical plane

A
  • greater movement of 100um in the horizontal plane

- lesser movement of 10um in the vertical plane

46
Q

What is the term used to describe tooth movement in response to load?

A

Visco-elastic system

47
Q

Maximum clenching forces between molars

A

500-700N

48
Q

State two factors that contribute to the viscosity in the visco-elastic tooth support

A
  • ECM/ground substance

- periodontal fluids

49
Q

Name two factors that contribute to the elasticity component of the visco-elastic tooth support

A
  • collagen

- bone

50
Q

Factors affecting tooth movement (x4)

A

Rate of load - slow rate, greater movement
Longer the tooth is loaded - slower the rate of return to original position, more mobile it becomes
If tooth is not loaded, becomes less mobile
The more often the tooth is loaded, the more the tooth is displaced, the less mobile it becomes

51
Q

Features of the PDL supporting how it is like a tension bearing system x4

A
  • oblique fibre orientation
  • sharpey fibres
  • fibroblast shape and orientation
  • chemistry of GAGs
52
Q

Features of PDL showing why it is unlike a tension bearing system x3

A
  • small diameter of collagen fibres
  • sparsity of sharpey fibres in some parts of the lamina dura of the socket
  • quantities of ground substances (>50%)

OB (7 decks)

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