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Oral Micro Exam 3 > Oral Micro Exam 3 Review > Flashcards

Oral Micro Exam 3 Review Flashcards

1
Q

What are some of the factors that result in dental caries?

A

(1) Microorganisms, (2) metabolic substrates, (3) teeth and their environment and (4) time. Take away any one of these four factors and you can significantly decrease if not entirely prevent caries.

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2
Q

What is the chemical formula of hydroxyapatite?

A

Ca_10(PO_4)6(OH)2

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3
Q

How do ion substitutions affect hydroxyapatite tooth structure?

A

Fluoride can substitute at the hydroxyl group and strengthen enamal (thereby effectively decreasing effective pH) Carbonates usually substitute for the phosphates.

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4
Q

What is critical pH of enamel?

A

The pH below which dissolution predominates in the oral cavity is about 5.5; this is termed the critical pH.

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5
Q

What are some of the key elements of the sucrose pathway?

A

Invertase breaks sucrose into fructose and glucose, fructosyl tranferase creates levans “snack food” as an extracellular insoluble polysaccharide chain and glucosyl transferse creates a “gum drop dome” out of glucose monomers

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6
Q

What is the acidogenic theory of caries formation and the role of sucrose in the process?

A

Some plaque bacteria are cabable of fermenting carb substrates to produce acid, causing plaque pH to fall < critical levels. Repeated exposure–>demineralization @ susceptible sites on tooth surface.

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7
Q

What are the differences between the terms aciduricity, acidophilic, and acidogenic?

A

Aciduricity is the ability to withstand low pH, acidophilic refers to bacteria that grow well in acidic environments and acidogenic refers to bacteria that metabolize products resulting in acidic byproducts

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8
Q

What are some of the differences between hetero-fermenters and homo-fermenters?

A

Homolactic fermenters produce two molecules of lactic acid per molecule glucose while heterolactic bacteria produce lactic acid and something else (such as ethanol, CO2 or acetic acid from one molecule of glucose)

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9
Q

What is the concept behind replacement therapy?

A

The idea is that by inoculating with genetically modified, less pathogenic S. mutans strains patients can avoid developing caries.

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10
Q

How might probiotic therapies someday impact caries development and treatment?

A

We could promote the colonization of benign bacteria to take up space and prevent the infiltration of pathogenic strains of bacteria like Strep. Mutans, actionmyces, and lactobacillus.

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11
Q

How may STAMP someday impact caries develompent and treatment?

A

In vitro biofilms treated with S. mutans (STAMP=Specifically-targeted anti-microbial peptides) resisted recolonization with S. mutans. Once established an ecosystem resists change.

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12
Q

How might Biofilm interference someday impact caries development and treatment?

A

Biofilm interference could inhibit biofilm formation or obstruct quorum sensing.

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13
Q

What is the relationship between critical pH and carbonate content in enamel?

A

Carbonate allows our teeth to flex a little and be more resilient to stress. The more carbonate present–>the less acid requied for it to reach the critical pH.

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14
Q

Which ions can substitute for calcium in hydroxyapatite?

A

Lead, strontium, radium, etc.

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15
Q

Which ion can substitute for phosphate in hydroxyapatite?

A

Carbonate

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16
Q

Which ion can substitute for the hydroxyl group in hydroxyapatite?

A

Fluoride

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17
Q

Which sites in the oral cavity are generally most susceptible to developing caries?

A

Pits and fissures, approximal surfaces of adjacent teeth, cervial margin just coronal to the gingival margin, exposed root surfaces, margins of deficient restorations and tooth surfaces adjacent to dentures and bridges

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18
Q

What are two general characteristics of caries-susceptible sites?

A

Favorable for plaque retention (hard to ‘mow the lawn’ and limited access for saliva

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19
Q

What is the progressive development for plaque deposits in the oral cavity?

A

Salivary proteins–>pellicle–>plaque biofilm–>calculus

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20
Q

What is the pellicle?

A

Acellular, homogeneous, organic film that forms on enamel and other hard surfaces by selective adsorption of salivary proteins and glycoproteins

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21
Q

What characteristics typify the pellicle?

A

Forms spontaneously on teeth, bacteria are not necessary for formation, can be removed only by meticuluous cleaning, reforms in a few hours and it forms an environment suitable for bacterial pioneer species adherence and multiplication

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22
Q

What is plaque biofilm?

A

Soft, non-mineralized bacterial deposit that forms on teeth

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23
Q

What is plaque biofilm composed of?

A

Plaque-tooth interface (generally pellicle), microbial layers and colonies and intercellular matrix (insoluble).

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24
Q

What are the main parts of the insoluble intercellular matrix of plaque biofilm?

A

Carbohydrates: glucans, fructans and other polysaccharides (primary component of the matrix) and protein.

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25
Q

What may happen when dietary carbohydrates, especially simple sugars are fermented by some plaque bacteria?

A

They produce acid (H+) and extracellular polymers (glucans and fructans). As the plaque thickens, the effects of saliva decrease, making the acid accumulation more pronounced. If too much acid is produced and accumulates, caries may form.

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26
Q

What is calculus?

A

Plaque biofilm in which inorganic deposits have caused mineralization. Calculus greatly increases risk for developing periodontitis

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27
Q

What evidence indicates that caries is an infectious disease?

A

Experiments conducted with gnotobiotic animals have shown that caries is an infectious disease. These experiments have also shown that both sugar and plaque bacteria (specifically. Strep. Mutans, Lactobacillus and Actinomyces) are required to cause disease.

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28
Q

What are some properties that make Streptococcus mutans so cariogenic?

A

(1) Excellent sugar transport @ low pH, (2) acid production (it is a homolactic fermenter), (3) aciduricity and acidophilic, (4) produces insoluble glucan and (5) produces intracellular polysaccharide (“snacks”) extracellular levan

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29
Q

What two common names are used for glucose polymers?

A

Glucans and dextrans

30
Q

What are levans?

A

Levans are fructose polymers. Sometimes they are called fructans.

31
Q

What are bacteriocins?

A

Bacterocins are very small MW antibiotic proteins produced by lactobacillus and Strep. Mutans as well as actinomyces that kill other bacteria but are very self-promoting. This is partially why cariogenicity propagates.

32
Q

What is the most cariogenic sugar?

A

Sucrose (sucrose=fructose + glucose)

33
Q

What is invertase?

A

Invertase is an enzyme that breaks down sucrose into glucose and fructose and imports them into the cell. It has a very high affinity for sucrose (much higher than glycosyl or fructosyl transferase) meaning that if you eat a small amount of sucrose, all will be metabolized rather than building the “gumdrop” dome and “snack food” polysaccharides.

34
Q

What does the enzyme levanase do?

A

Levanase cuts off the far end of the fructose chain and “feeds” it through the glycolytic fermentation pathway.

35
Q

What is a MAJOR virulcence pathway unique to Strep. Mutans?

A

Glucosyl transferase

36
Q

What features of glucosyl transferase make it so cariogenic?

A

Glycosyl transferase has an affinity for sucrose and creates glucose polymers. It cracks sucrose in 2 and fructose enters the cell. The glucose polymer is highly insoluble creating a safe-house for bacteria because saliva cannot reach inside the polymer dome of protection (it excludes oxygen, saliva, etc.)

37
Q

What is the function of fructosyl transferase?

A

Fructosyl transferase creates an extracellular matrix fructose polymer rather than taking the monomers directly into the cell. These fructose chains serve as storage for bacterial snack foods.

38
Q

Which group of mice would produce the greatest amount of lactic acid? High fructose corn syrup or Sucrose?

A

High fructose corn syrup because all of the byproducts make it through the processes that result in lactic acid. However, this lactic acid will not be as concentrated for as long because ther is no “gumdrop” dome and snack food as associated with sucrose.

39
Q

Which type of bacteria are known for eating the garbage “byproducts” of Strep. Mutans?

A

Veillonella and Neisseria

40
Q

Give an example of a typical composition of high fructose corn syrup.

A

High fructose corn syrup 50%/50%. These percentages refer to glucose/fructose and is one of the more common forms compositions of sucrose BUT the monomers are not covalently linked whereas they are in sucrose.

41
Q

Why is Streptococcus mutans the major pathogen of caries formation?

A

The bacteria form branched, insoluble, extracellular, polycaccharide chains (protective dome), localize acid production over longer periods of time, form levans, are homolactic fermenters and compete well in acidic environments.

42
Q

Which disaccharide does Glucosyl transferase require to form the “gumdrop” protective dome of extracellular insoluble polycaccharide chains?

A

Sucrose

43
Q

What features of Xylitol make it somewhat specific for Streptococcus mutans?

A

Xylitol is a non-fermentable sugar, it stimultes saliva flow, looks like fructose (ending in a fruit-less loop: ATP used to pump it into the cell and back out)

44
Q

What happens if saliva does not contain necessary buffering capability?

A

Without buffers, if you feed bacteria sugars, the pH will become more acidic and will begin to select for cariogenic bacteria.

45
Q

What is an example of bacterial succession?

A

There is a higher percentage of mutans Streptococcus, Actinomyces spp and Lactobacillus (bacteria that succeed at more acidic pH) in plaque taken from active caries sites that replace bacteria that succeed at more neutral pH.

46
Q

Where are the four major locations where caries form?

A

(1) pits and fissures-strep mutans, (2) smooth-surface caries-strep mutans, (3) dentin-actinomyces and lactobacillus, (4) root caries-lactobacillus and actinomyces

47
Q

What is the strongest acid in the oral cavity?

A

Lactic acid

48
Q

A strong acid will have a very high or a very low pKa?

A

The LOWER the pKa, the STRONGER the acid

49
Q

What do Stephan cruves illustrate?

A

The pH drop in plaque that accompanies a glucose rinse. Plaque associated with rampant caries start at a much lower ‘resting’ pH than does ‘healthy’ plaque on a caries-free tooth. This allows the pH to drop below the criticla pH for an extended period of time in the plaque associated with rampant caries.

50
Q

What does the effectiveness of a given carbohydrate in promoting caries depend upon?

A

(1) The ability of cariogenic bacteria to metabolize the carbohydrate and (2) the ability of the carbohydrate molecules to diffuse into plaque.

51
Q

Which is more important–the amount of sugar consumed or the frequency thereof?

A

The frequency of sugar consumption is more important

52
Q

Name several desirable features of saliva?

A

It aids in swallowing and digesting food, serves as a chemical and thermal barrier, reduces tendency to develop caries, flushes away food and bacteria, contains antimicrobial agents, and acts as a buffer to maintain nuetral pH.

53
Q

How would you describe the concentrations of calcium and phosphate in saliva? (super-saturated or under-saturated)

A

Super-saturated. Since saliva has super-saturated concentrations of calcium and phosphate it aids in tooth remineralization

54
Q

Name several deleterious effects of hyposalivary secretion (xerostomia).

A

Tendency to oral ulceration, difficulty in swallowing dry foods, thermal and chemical sensitivity, altered taste, increased tendency to caries.

55
Q

If a patient insists on brushing teeth only ONCE per day, when should he/she do so?

A

During the evening. Salivary secretions decrease significantly at night so oral hygiene before going to sleep will help reduce some of the negative effects of xerostomia.

56
Q

What are some treatments available for the lack of saliva?

A

Aritifical saliva, increased oral hygiene, dietary control (decrease sugars), and fluroide therapy.

57
Q

Which is more important–systemic fluoride treatment or topical application after teeth erupt?

A

Topical application is more important

58
Q

What is the highest-substituting ion in hydroxyapatite?

A

Carbonate–fluoride drives out a significant amount of carbonate furthering strengthening the crystalline structure of enamel.

59
Q

What do DALY, YLD and YLL refer to and how are they related?

A

DALY=YLD+YLL Disability adjusted life years = years of life lost to disability + years of life lost (death)

60
Q

What are the top two preventative procedures reducing the development of caries?

A

Sealants (72%) and chlorohexadine (46%)

61
Q

What are some microbiological techniques that may reduce the effects of Strep. Mutans?

A

over-express glucosyl transferases, insert extra genes for the production of bacterocins, remove lactate dehydrogenase and replace with alcohol dehydrogenase

62
Q

What three elements make up the basic structure of STAMPS (specifically-targeted antimicrobial peptides)?

A

(1) a targeting region, (2) linker region and (3) antimicrobial region

63
Q

What are three major ways fluoride lowers caries risks?

A

(1) It is the most electronegative element so it holds hydroxyapatite structure more tightly together and makes demineralization harder and remineralization easier. (2) It lowers CO2 content and (3) binds and poisons key metabolic enzymes in bacteria lowering acid production

64
Q

What are the mechanisms whereby probiotics may function to reduce the risk of caries in the future?

A

Competitive exclusion of pathogens, inhibit growth of pathogens, optimize immune response and restore normal flora after treatment.

65
Q

What are two inhibitory effects associated with probiotic mechanisms?

A

Inhibition can occur via competition for nutrients and releasing toxic substances like bacterocins

66
Q

What are four areas in which probiotics have decreased mobidity and mortality?

A

Neonatal necrotizing enterocolitis, antibiotic-associated dirrhea, clostridium dificile-associated diarrhea and irritable bowl syndrome (IBS).

67
Q

What are some of the effects of treating neonatal necrotizing enterocolitis with probiotics?

A

Impressive results: probiotics lower 15-20% mortality to about 5%. This is not becoming standard of care.

68
Q

What are some of the effects of treating antibiotic-associated diarrhea with probiotics?

A

Modest improvements, but consistently good results; probiotics lower the chance of developing diarrhea and cause the effects to be less severe

69
Q

What are some of the effects of treating clostridium dificile-associated diarrhea with probiotics?

A

Modest but consistently good results; lowers chance of developing C. diff. and it is less severe if it develops

70
Q

What are some of the effects of treating irritable bowl syndrome (IBS) with probiotics?

A

IBS is theh most commonly-diagnosed GI pathology. Supportive evidence for probiotics, which lessen symptoms.

71
Q

What are three bacteria commonly found in yogurt?

A

Lactobacillus, Bifidobacterium and Streptococcus

Oral Micro Exam 3 (1 decks)

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