Pg 117 - 129 Flashcards
- What two experiments have shown that appropriate bacteria must be present to produce caries?
- Germ-free animals do not develop caries even when fed a highly cariogenic diet
- Add-back experiments): Through tests on animals with known flora (gnotobiotic animals), bacteria capable of causing caries can be identified (strep mutans, lactobacillus spp, actinomyces spp.)
- List the six characteristics that implicate “mutans” Strepococci as the dominant cause of caries at most tooth sites
- Sugar transport?
- Lactic acid?
- Do they like acid?
- How do they use excess glucose?
- How do they use excess fructose?
- What kind of “factors” do they have to resist saliva washing?
- Excellent sugar transport at low pH (most do not)
- Homolactic acid fermentors (Produce two lactic acid for every sucrose fermentation)
- They are aciduric (tolerant) and acidophilic (grow well)
- They utilize extra glucose to make insoluble glucans, protecting them from saliva and increasing acid levels
- They utilize extra fructose to make extracellular levans (snack-food)
- Attachment factors - Attach to tooth surface
- Strep mutans is special in how it handles excess glucose. What properties of the polysaccharide chains that it makes are unique compared to normal bacteria?
Strep mutans makes branched and insoluble EC polysaccharide chains
Normal bacteria make non-branched and soluble EC polysaccharide chains
- Define acidouricity
Highly resistant to acid - enables acidophilicity of strep mutans
- Define acidophilic
Able to compete well in acidic environments (due to acidouricity)
- Define acidogenic
Produces acids (strep mutans produces lactic acid)
- What are examples of bacterial succession?
- Glucose levels
- pH levels
A diet high in sugar can select for aciduric bacteria (able to tolerate high acid environments).
Example 1: Strep, Lacto, and Actino are all found in high levels after glucose rinses.
Bacteria that can tolerate certain environments will have an advantage at competing in those environments.
Example 2: Strep mutans and S. sorbinus can metabolize and produce significant acid even at a lower pH.
- What are the six major sites of plaque-related diseases and what bacteria are typically responsible at each site?
- Pits and fissure caries (s. mutans)
- Smooth-surface caries (s. mutans)
- Dentin lovers (s. mutans, lacto, and actinomyces)
- Root caries (s. mutans, lacto, and actinomyces)
- Endodontic infections (mixed gram- anaerobic)
- Gingivitis and perio (gram- anaerobic)
- What is the Stephen curve?
It describes the change in dental plaque pH in response to a challenge, such as glucose rinse or gum-chewing
- Stephen curve
Which type of environment will lead to a tooth being below the critical pH for an extended period of time and why?
- Caries-Free tooth or Rampant caries tooth
How can brushing the teeth help?
Rampant caries tooth - since it has a much lower “resting” pH.
By brushing the teeth, the amount of acid is greatly reduced (mowing the lawn).
- What two factors govern the effectiveness of a given carbohydrate in promoting caries?
- Ability of cariogenic to metabolize the carb
2. Ability of carb molecule to diffuse into plaque
- Which type of sugars are more effectively metabolized by plaque bacteria - simple or complex?
Which is more important in terms of promoting caries - frequency or amount of sugar consumption? Why?
Simple
Frequency - Longer duration below critical pH
- List the major functions of saliva
- Swallowing/digesting food
- Chemical barrier / thermal insulator
- Reduce caries tendency
- What are the five ways that saliva reduces caries tendency?
- Flushes away carbs
- Contains Ca and PO4 for tooth remineralization
- Contains antimicrobial agents (lysozyme and Ab)
- Chemical buffer (bicarbonate buffer system)
- Source of recycled topical fluoride
- What are the five effects of a lack of saliva (xerostomia, dry mouth)?
- Oral ulceration
- Difficulty swallowing dry foods
- Thermal and chemical sensitivity
- Altered taste
- Increased caries tendency
