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23 Cards in this Set
- Front
- Back
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1. What is enamel made up of?
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Biological apatite
Structure is based on crystalline calcium hydroxyapatite BUT differs... 1. Substitution of ions other than Ca, PO4, and OH 2. Porosity |
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2. When does demineralization occur?
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If ion concentration in solution falls below the solubility product, the rate of recrystalization will drop below the rate of solubilization
Net loss of crystall mass |
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3. What inhibits crystal growth at the outer tooth surface?
How does pH affect remineralization and demineralization? |
Proteins in the acquired pellice and in solution in saliva
Above pH of 5.5 (critical pH) have remineralization Below, net demineralization will occur |
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4. What does general oral acidity arise from?
What are 3 common causes? |
Acids that originate outside the oral cavity
1. Dietary acids 2. Regurgitation of stomach acids 3. Chronic occupational exposure to volatile acids |
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5. What does localized oral acidity arise from?
In order to survive in the mouth, what must bacteria do? |
Metabolic acids generated by anaerobic bacteria residing in dental plaque
Attach to stable surfaces and construct a protective shell around themselves to block access of salivary proteins **Flushing and antibacterial properties of saliva are sufficient to prevent proliferation of most bacteria in oral cavity |
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6. What are the steps in the formation of dental plaque?
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1. Deposition of the acquired pellicle
2. Newly formed pellicle is quickly invaded by bacteria in saliva and from surrounding surfaces **llipoteichoic acid aid in attachment 3. Initial stage of bacterial growth produces a thing aerobic lawn of bacteria in a protein matrix 4. Formation of mature plaque -sticky gelatinous polysaccharide matrix |
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7. As the plaque becomes thicker, what happens in the interior?
What are plaque polysaccharides composed principally of? What is the most abundant polymer in plaque? What linkage predominates in mutans? What are the fructose polymers called? |
The interior becomes increasingly anaerobic
Glucose polymers Dextrans (α-1,6 linkage predominates, also have branch points) Levan (aka fructan) 1,3 linkage |
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8. What is the function of fructose polymers in plaque?
What is the function of glucose polymers in plaque? |
Extracellular carbohydrate depot for bacteria in the plaque
**They are rapidly degraded Form the permanent structure of the plaque matrix |
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9. Where are plaque glucans and frucans formed?
What does dextran sucrase do? What does fructan sucrase do? |
Outside the bacterial cell by extracellular sucrases
Adds glucose unit of sucrose to a glucan polymers releasing the fructose unit as free fructose Adds the fructose unit to a growing fructan polymer, releasing the glucose unit as free glucose |
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10. Why is sucrose the only dietary carbohydrate that can support the formation of dextrans and fructans in dental plaque?
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1. Substrate specificy of the enzymes secreted by plaque bacteria
2. Sucrose is a high energy hexose donor (thermodynamic reason) |
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11. Why is sucrose different from other carbohydrates?
What does this do to the glycoside bond? What energy do dextran and fructan sucrases use? |
α-1,2 glycoside linkage involves 2 hemiacetal carbons
Makes the bond very unstable The energy of hydrolysis of the α-1,2 bond in sucrose to drive the formation of the α1,6 bonds in dextran **hydrolysis of bond in sucrose is -6 kcal/mmole |
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12. What is the rate limiting step in the growth and expansion of dental plaque?
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Dextran formation
**Availability of dietary sucrose in mouth determines how fast plaque develops on susceptible surfaces |
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13. What are the alternative sugar sweeteners (non-plaque forming) that partially replace sucrose?
Three... |
1. Corn syrup or corn sweetener
(high-fructose corn syrup) 2. Honey 3. Malt sugar or malt |
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14. What is the environment like at the underlying surface of the tooth in fully develop dental plaque?
How do they generate energy? What is the end products? What kind of environment is produced at the surface of the tooth and why? |
Anaerobic microenvironment
Anaerobic glycolysis Lactic acid or other organic acid Acidic environment b/c salivary buffers cannot diffuse into plaque fast and metabolic acids cannot diffuse out quickly |
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15. How do the various carbohydrates contribute to acid production via anaerobic glycolysis?
Glucose Other sugars (fructose, sucrose, etc) Starch Plaque fructans Which type of sugars produce the biggest drop in pH? |
1. Taken up by plaque bacteria and metabolized directly
2. Taken up by plaque bacteria and rapidly converted to glucose or glycolysis intermediates 3. Partially digest by salivary amylase and converted by plaque bacteria to maltose 4. Converted to fructose **Simple sugars b/c they are metabolized rapidly |
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16. What is a Stephan curve?
When will demineralization occur? What is the amount of demineralization proportional to? |
Plot of pH changes within dental plaque as a function of time after ingestion of glucose (or any other carb)
During the period time that the pH is below 5.5 Area between the curve and pH 5.5 (shaded area) |
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17. When glucose levels are high, what is the predominate end product of anaerobic glycolysis?
Why is this especially deleterious to dental enamel? What species of bacteria is responsible for the burst of lactic acid production? |
Lactic acid production
Has a very low pKa and creates a very low pH Streptococcus species b/c they have adaptations that enable them to metabolize glucose rapidly in an acidic environment |
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18. What are the adaptations of Streptococcus species?
(two things) What does the Veilonella species do? |
1. Very active glycolysis pathway
2. Two glucose transport systems (high affinity and low affinity transporter) Provides a protective action by converting lactate to acetate and propionate |
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19. Where does remineralization tend to occur?
How o the reformed hydroxyapatite crystals differ from biological apatitie? How is dental calculus formed? How is the precipitated calcium phosphate in dental plaque? |
Near the surface of the tooth producing a layer of remineralization on top of an underlying zone of incomplete remineralization
Less ordered (net progressive weakening of enamel) Precipitation of calcium phosphate in dental plaque **calculus blocks nutrient diffusion to bacteria so have a dead region of calcified plaque surrounded by non-calcified living plaque Heterogeneous |
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20. What do fluoride ions do?
How much of the hydroxide ions are replaced by fluoride ions? How does the increasing substitution of hydroxyl ions w/ fluoride ions decrease the solubility of biological apatite? (two ways) |
Take the place of hydroxide ions in the crystal structure of biological apatite
**Provide protection against caries b/c calcium fluoroapatite is extremely hard insoluble mineral Small amounts 1. Decreases the effect of pH on the solubility of biological apatite (more resistant to acid) 2. Decreases the level of carbonate in enamel (carbonate increases enamel solubility) |
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21. Fluoride concentrations up to what in drinking water dramatically reduce the overall incidence of dental caries?
When is the protective effect of fluoride against caries the greatest? What doe fluoride ions at the enamel surface do? How does cooking surface affect fluoride level? |
1 ppm
When fluoride is present during maximal tooth formation (i.e during the first 8 yrs of childhood) Increase the rate of remineralization Cooking on teflon increases it, cooking on aluminum surfaces decreases it |
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22. How is fluoride metabolized?
Where is long term uptake and retention proportional to total intake found? |
Rapidly taken up by stomach and to lesser extent the intestine
After fluoride dose, plasma levels rise over the first half hour then decline as fluoride is taken up by muscle and liver Primarily in bone and teeth |
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23. When will children develop fluorosis?
When will fluoride toxicity occur? What are the safe and adequate ranges of dietary fluoride? What is the standard for fluoridation of drinking water? |
Ingest excess fluoride (2 - 8 ppm)
Years of daily exposure to 20 -80 mg/day of fluoride 0.1 - 1.0 mg/day in 1st yr of life 0.5 - 1.5 mg/day in 2nd yr of life 1.5-4.0 mg/day for adults 1 ppm |
