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Flashcards in L10 Deck (62)
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1
Q

A. Bone Structure and Composition

A

Cortical (compact) bone
Trabecular (cancellous or spongy) bone

Periosteum
Endosteum
Neurovascular supply
Marrow space

2
Q

The Haversion System (Secondary Osteon):

Main Functional Unit of Cortical Bone

A

The wall: concentric lamellae
The central canal: Haversian canal, nerve and blood supply
Main cell component: Osteocytes
Separation between osteons: Interstitial lamellae
Connection between osteons: Volkmann’s canals

3
Q

Osteons, Lamellae and Lacunae/Canaliculi

A

Primary osteon
Secondary osteon

Concentric lamellae Circumferential lamellae Interstitial lamellae

Lacunae
Canaliculi

4
Q

Bone Matrix

A

Inorganic matrix: mainly in the form of hydroxyapatite

Organic matrix: mainly collagen I

5
Q

Bone Cells 2 lineages

A

Mesenchymal lineage

Hematopoietic lineage

6
Q
  1. Mesenchyme Stem Cells (MSC)
A

Also referred as colony-forming fibroblast (CFU-F), or marrow stromal cells

Potential to differentiate into multiple cell types

Morphological features: small cell body, few cell processes

7
Q

Confirmation of MSC Identity

A

Ability of osteogenic, chondrogenic and adipogenic differentiation

8
Q

Our findings are consistent with reports from many others and support that

A

local delivery of MSCs can enhance bone regeneration.

9
Q

MSCs info

A
  1. Derived from pigs
  2. Have been used in human surgeries to stop bleeding
  3. Recently have been used in a few in-vivo animal studies and showed promising results in carrying cells for bone regeneration
  4. Commercially available and sterile
  5. Easy to fit into a mandibular distraction site and fast biodegradable
  6. Our preliminary experiments have shown good cell integration and infiltration with this material and all procedures can be handled in strictly sterile environment
10
Q

A Commonly Held Mechanism:

A

Empower local bone regeneration by providing a large source of MSCs, hence boosting or bypassing the slow MSC recruitment process

11
Q
  1. Osteoblasts: Bone-forming Cells
A

Basic characteristics:

- Located on bone surface 
- Generally cuboidal shape
- Mononucleated
- HE staining: basophilic cytoplasm (large quantity of   rough endoplasmic reticulum)
12
Q

Major Functions of Osteoblasts

A

1.Synhesize and secret extracellular matrix

13
Q

Collagen related proteins:

A

Collagen type I, III, V

14
Q

Glycoproteins:

A

Alkaline phosphatase

Osteonectin

15
Q

Glycoaminoglycan-containing proteins:

A
Aggrecan
       Versican
       Decorin 
       Biglycan
       Hyaluran
16
Q

(MEPE):

A

Matrix extracellular phosphoglycoprotein

17
Q

RGD-containing glycoproteins:

A

Thrombospondins
Fibronectin,
Vitronectin
Fibrillin 1 and 2

18
Q

Small insulin-binding N-linked glycoproteins (SIBLING):

A

Osteopontin

Bone sialoproteins

19
Q

gamma-Carboxy glutamic acid-containing proteins:

A

Matrix Gla protein

Osteocalcin

20
Q
  1. Regulate matrix mineralization
A

Inside the vesicles, calcium and phosphorous can reach high concentrations without being saturated.

21
Q

TNAP:

A

Tissue non-specific alkaline

phosphatase

22
Q

NPP1:

A

Nucleotide pyrophosphatase

phosphodiesterase

23
Q

NTP:

A

Nucleoside triphosphates

24
Q

ANK:

A

Ankylosis protein

25
Q

BSP:

A

Bone sialoprotein

26
Q
  1. Regulate Osteoclasts through Molecular Interactions
A

The OPG/RANKL/RANK system:
RANKL: stimulate osteoclast differentiation and maturation
OPG: bind to RANKL and indirectly inhibit osteoclast differentiation

27
Q
  1. Osteocytes:
A

Bone-maintaining Cells

28
Q

Osteocyte Basic characteristics

A
  • Derived from osteoblasts when buried in the matrix
    • Located in laculae inside the matrix
    • Most abundant cell type in bone
    • Mononucleated
    • Multiple dendritic processes
29
Q

Main Functions of Osteocytes

A

Regulate osteoblasts & osteoclasts through cell processes

 - Maintain bone vitality and function
 - Sense mechanical loading
30
Q

After sensing loading, osteocytes regulate bone formation/resorption mainly through the

A

sclerostin-OPG/RNAKL system

31
Q

Sclerostin (SOST) is only expressed in

A

osteocytes, not in any other bone cells

32
Q
  1. Osteoclasts: Bone-resorption Cells
A

Basic characteristics

  - Largest of all bone cell types
  - Often located on bone surface (Howship’s lacunae)
  - Multinucleated
  - Tartrate resistant acid phosphatase (TRAP) positive cytoplasm
33
Q

Characteristics of osteoclasts

A

Abundant mitochondria

- Vesicles: acid phosphatase 
- Sealing zone: attachment and sealing 
- Ruffled border: pump H+ (for demineralization), release enzymes (for organic matrix degradation)
34
Q

Main Functions of Osteoclasts

A

Demineralize bone

 - Degrade organic matrix
 - Endocytosis of degraded products
35
Q
  1. Bone Lining Cells: Inactive Osteoblasts (?)
A

Basic characteristics

- Flattened spindle shape 
- Located on bone surface 
- Ovoid mono-nucleus
- Few organelles 
Function
    - Uncertain
    - May be induced to proliferate and   differentiate into osteoblasts
    - May be involved in smoothening 
    osteoclast lacunae
36
Q

C. Bone Modelling and Remodelling

A

There are two processes for bone formation:
A. Endochondral ossification: form cartilage first
B. Intramembranous ossification: directly from periosteum
C. Sutural bone formation: a special intramembranous process through sutural matrix

37
Q

Bone Formation Processes underlying
Jaw Bone Growth

Mx

A

intramembranous (surface and sutures)

38
Q

Bone Formation Processes underlying
Jaw Bone Growth

Mn

A

Mn – endochondral (condyle) & intramembranous (surface)

39
Q

Modeling:

A

change of overall bone size and shape; bone

formation and resorption happen at different locations

40
Q

Remodeling:

A

Replacement of existing bone; bone
formation and resorption at the same location but at
different times

41
Q

Secondary Osteons Are Important for

A

Cortical Bone Remodeling

42
Q

Trabecular bone remodelling

starts at

A

bone surfaces

43
Q

General Characteristics of Bone Remodeling

A

Cycle duration: formation > resorption
Remodeling rate: children > adults, trabecular bone > cortical bone
Osteoporosis: unbalanced formation/resorption  net bone loss
Regulation: Multiple factors (gene, hormone, mechanical loading, metabolism, etc.)

44
Q

Mesial-distal section:

A

Interdental septum has two layers: bundle bone and supporting bone

45
Q

Bundle bone: Sharpey’s fiber

A

inserted to this layer

Other names: Alveolar bone proper, cribiform plate, lamina dura

46
Q

Bundle bone-PDL fibers-Cementum

A

Cells between Sharpey’s fibers:

  • Fibroblasts
  • Mesenchymal stem cells and osteoprogenitors
  • vascular cells

Cell on bone surfaces:

  • Osteoblasts
  • Bone lining cells
47
Q

Embryonically, most craniofacial bones have

a different

A

tissue origin than long bones

48
Q

Jaw bone mesenchyme is developed from

A

neural crest

(1st branchial arch) and mesoderm

49
Q

Postnatal growth of the

A

alveolar process is highly correlated with tooth eruption

50
Q
  • Tooth agenesis –>
A
  • Tooth agenesis  poor development of alveolar bone
51
Q

Modeling takes place during alveolar bone growth

A

Bone formation: Vertically at crests along with tooth eruption; transversely at buccal surface and lingual bundle bone along with buccal expansion
Bone resorption: Lingual surface and buccal bundle bone

52
Q

Alveolar Bone Loss: Risk Factors

A

Periodontal disease

 - Tooth loss
 - Pathology
 - Systemic disease
 - Side effects of medication
 - Trauma, parafunction, excessive orthodontic force
53
Q

Techniques for alveolar bone preservation or augmentation

A

Guided bone regeneration with bioabsorbable membranes

 - Bovine-derived bone graft
 - Mineralized human allograft
 - Bioactive glass material
 - Synthetic alloplast 
 - Autogenous bone graft
 - Decoronation and submergence of roots
 - Immediate implants
 - Orthodontic tooth movement
 - Distraction osteogenesis  
 - Stem cell assisted treatment
54
Q

Alveolar Bone Changes In Response to Loading:

A

Orthodontic Tooth Movement

Tooth movement —- a modeling process of the alveolar bone

55
Q

Due to resorption on one side, formation on the other, the

A

interdental septum is relocated, but not removed during tooth movement

56
Q

PDL fiber attachment adapts to

A

bone modeling during orthodontic tooth movement

57
Q

PDL Bone resorption side:

A

Detachment → → → → attachment reconstitution

58
Q

Bone formation side:

A

Thickening of bundle bone → → → → remodeling of bundle bone from the endosteum (the opposite side of the PDL)

59
Q

Source of osteoclasts on the resorption (compression) side:

A
  • Normally, osteoclasts are not present in the PDL.
  • Upon receiving compressive force, they are recruited from the blood flow (light pressure) and/or the bone marrow of the adjacent alveolar process (heavy pressure)
60
Q

Heavy pressure

A

occludes blood vessels

61
Q

In response to heavy pressure, osteoclasts were recruited from

A

bone marrow, the opposite side of the PDL undermining resorption

62
Q

Source of osteoblasts on the formation (tension) side:

A

Possible sources of osteoblasts:

Osteoblasts already present at the bone surface
 MSCs in the PDL
MSCs in the bone marrow
Bone lining cells