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15 Cards in this Set
- Front
- Back
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1. What is the composition of bone?
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1. Collagen protein matrix
2. Hydroxyapatite **calcium phosphate **provides hardness and brittleness to bone |
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2. What type of collagen is in bone?
What does it provide? Why is collagen in bone stronger than other collagen? |
Type I collagen
Provides mechanical strength and shape There is H-bond between hydroxyproline and lysine cross-links |
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3. How does bone formation occur?
Four steps... |
1. Osteoblasts synthesize and secrete collagen (pro-collagen)
2. Pro-collagen forms fibrils in EC space 3. Crystallization of CaPO4 occurs at gaps between tropocollagen molecules within the fibrils 4. Proteoglycans and associated water are replaced by the mineral phase as the crystals grow |
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4. What provides highly localized concentrations of calcium and phosphate for the mineralization process?
What are the nucleation sites in bone formation? |
Osteoblasts
Holes between tropocollagen molecules |
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5. Which is more soluble biological apatite or pure mineral hydroxyapatite?
How is the solubility calculated? |
Biological due to presence of proteins, carbs, and lipids
The produce of the concentration of Ca and PO4, mainly in the form of HPO4^2-, in solution **This product must exceed the solubility constant (Ksp) for the given set of conditions |
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6. What control is Ca and HPO4^2- under?
How does pH affect bone absorption? Is the formation of hydroxyapatite favored under physiological conditions? Why or why not? |
Ca: hormonal control
HPO4^2-: hormonal and pH control Low blood pH means would break down bone (bone lose) Yes Plasma is supersaturated w/ Ca and PO4 and product of two exceed solubility constant |
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7. Why don't hydroxyapatite crystals form in plasma and throughout the body?
Two reasons? What do osteoblasts produce that is important to crystallization? |
1. Crystal formation is strongly promoted by nucleation centers or "seeds"
2. Presence of inhibitors of crystalization (pyrophosphate) block crystallization at undesirable sites Pyrophosphatase (hydrolyzes the inhibitor pyrophosphate) |
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8. In addition to collagen, what are two other components of the organic matrix that are important in crystallization?
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1. Osteopontin
modulates growth of CaPO4 crystals 2. Osteocalcin |
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9. What is dental calculus?
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Plaque mineralized by deposition of Ca and PO4 resulting from interactions between the oral microbial plaque flora and components of oral fluids
Doesn't have same structure or composition as biological apatite |
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10. What are the important cells in bone resorption?
What roles does osteopontin play in bone remodeling? (two roles) What are osteocytes? What do they do? |
Osteoclasts
1. Anchors osteoclasts to bone 2. Activates osteoclasts (increase intracellular Ca+ levels) Osteoblasts entrapped in bone as it forms Play a role in bone resoprtion |
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11. What hormone do osteocytes respond to?
What do they do? How does this affect Ca? Which type of bone has higher remodeling rate? |
Parathyroid hormone
Secrete degradative enzymes that result in dissolution of the mineral and matrix in the immediate vicinity Ca can be rapidly mobilized from bone Trabecular bone |
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12. How is tooth development under hormone control?
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Ameloblasts and odontoblasts are target cells for 1,25-dihydroxy-vitamin D
This turns on calbindin protein express which may transport Ca to the forming dentin and enamel matrices |
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13. What are contributing factors to bone loss (esp in postmenopausal women)?
Four things... |
1. Low estrogen levels
2. Low Ca and vitamin D levels 3. Low physical activity 4. Genetics |
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14. What does estrogen repress the expression of?
What happens after menopause? How does this affect bone? |
Interleukin-6 gene
Increased production of interleukin-6 which promotes development of immature osteoclasts into mature ones Shift balance towards bone resoprtion (bone loss) |
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15. How is osteoporosis related to dentistry?
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Leads to increased tooth loss in people with periodontal disease
**due to decreased maxillary bone mass and density Tooth loss may signal the onset of osteoporosis **Bones are more porous and thus weaker (subject to fracture) |
