Lecture 14-18 Caries part 1

Question 1

Define dental caries

Answer 1

A disease of the mineralized tissues of teeth (enamel, dentin, and cementum) caused by the action of microorganisms on fermentable carbohydrates. It is characterized by demineralization of the mineral portion of these tissues, followed by disintegration of their organic matrix.

Question 2

T or F, In its early stages, caries can be arrested and remineralization can occur

Answer 2

True

Question 3

What is the acidogenic theory and when did was it proposed?

Answer 3

1897 - WD Miller
- Some plaque bacteria are capable of fermenting suitable dietary carbohydrate substrates to produce acid, causing plaque pH to fall below critical levels. Repeated exposure to acid pH in time may result in demineralization at susceptible sites on the tooth surface, thus initiating the carious process.

Question 4

The formation of carious lesions depends on a combination of four factors:

Answer 4

1. Microorganisms (Quality and number of bugs)
2. Metabolic Substances (Quant. & Qual. of sugars)
3. Teeth and their environment (Quality of teeth, saliva)
4. Time (Duration and Frequency)

Question 5

What is the Flouride anti caries mechanism? (2) How long is it good for?

Answer 5

1. Systemic
   - During tooth development
2. Topical (much more important because it lasts lifetime of tooth)
   - After tooth eruption

• This is only good until tooth eruption

Question 6

What makes up the organic matrix of tooth hard tissue:

Answer 6

• Protein (collagen, others) –> main component

- Other organic (mucopolysaccharides, chondroitin sulfate)

Question 7

What makes up the mineral portion of tooth hard tissue:

Answer 7

• Hydroxyapatite –> main component
  
  • (calcium, phosphate, hydroxyl formed into hard crystal lattice)
• Other positive ions: Lead, zinc, strontium, silver, nickel, iron
• Other negative ions: Carbonate, Fluoride

Question 8

Fluoride brings down the critical pH of hydroxyapatite to what?

Answer 8

pH 5.5 to a pH 4.9

Question 9

Cells in percent by weight within the composition of tooth hard tissue

Answer 9

Enamel:

• Organic (4%)
• Mineral (95%)
• Water (1%)

Dentin:

• Organic (20%)
• Mineral (70%)
• Water (10%)

Question 10

3 major ways that fluoride lowers caries risk

Answer 10

1. Most electronegative element
   - Holds hydroxyapatite structure more tightly together
   - Makes demineralization harder
   - Remineralization easier
2. Lower CO3(2-) content
   - More acid resistant
   - Lowers pH threshold of hydroxyapatite
3. Binds & Poisons key metabolic enzymes in bacteria
   - Lowers acid production

Question 11

Co3(2-) is what percentage the most common substitution

Answer 11

3% most common substition

Question 12

Hydroxyapatite is a structure held together by what bonds?

Answer 12

Ionic bonds (positive & negative charges)

Question 13

In hydroxyapatite crystal lattice, other ions of appropriate size and charge, can substitute for the various inorganic ions

• For Calcium
• For phosphate
• For hydroxyl

Answer 13

Calcium: Lead, Strontium, Radium, etc.
Phosphate: Carbonate, etc
Hydroxyl: Fluoride, etc

Question 14

The resistance of enamel to chemical attack depends (in part) on: (2)

Answer 14

1. The regularity with which the hydroxyapatite crystals line up. The more regular the alignment, the more stable the physical structure.
2. The presence of substitute ions that can either increase or decrease susceptibility to chemical attack, depending upon the particular substitution.

Question 15

T or F, The mineral lattice is completely non-porous so that free ions cannot diffuse into it.

Answer 15

False, It is porous so free ions can diffuse into it. Thus the composition of hydroxyapatite can vary from one part of a tooth to another

Question 16

T or F, Hydroxyapatite can be dissolved by acid; the reaction is irreversible

Answer 16

False, the reaction is reversible (pH dependent)

Question 17

2 general characteristics of caries-susceptible sites

Answer 17

1. Favorable for plaque retention (hard to mow lawn)

2. Limited access for saliva

Question 18

6 susceptible sites of caries

Answer 18

1. Pits and fissures
2. Approximal surfaces of adjacent teeth just cervical to the contact point
3. Cervical margin just coronal to the gingival margin
4. Exposed root surfaces
5. Margins of deficient restorations
6. Tooth surfaces adjacent to dentures and bridges

Question 19

What percent risk is there for white caries lesions under braces

Answer 19

80%

Question 20

T or F, The major caries-susceptible sites have limited saliva access, which favors plaque retention.

Answer 20

True

Question 21

Pits and fissures that are considered susceptible sites to caries can be found where?

Answer 21

1. Pits and fissures on occlusal surfaces of molars and premolars
2. Buccal pits of molars and palatal pits of maxillary incisors

Question 22

What is the sequence to plaque development:

Answer 22

Salivary proteins –> Pellicle –> Plaque biofilm –> (Calculus)

Question 23

Pellicle defintion:

Answer 23

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

Question 24

6 characteristics of Pellicle

Answer 24

1. Forms spontaneously on teeth
2. Bacteria not necessary for formation
3. Can be removed only by meticulous cleaning
4. If removed, rapidly forms again (minutes to a few hours)
5. Protective functions have been suggested but not proven
6. Forms suitable environment for bacterial pioneer species adherence and multiplication –> Plaque biofilm

Question 25

Plaque biofilm definition:

Answer 25

soft, non-mineralized bacterial deposit that forms on teeth

Question 26

Composition of plaque biofilm

Answer 26

1. Plaque-tooth interface (generally pellicle)
2. Microbial layers and colonies
3. Intercellular matrix (insoluble)
   - Carbs (primary component of matrix)
   - Protein

Question 27

T or F, As the plaque thickens, the effects of saliva decrease, making the acid accumulation more pronounced

Answer 27

True

Question 28

Definition of Calculus:

Answer 28

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

Question 29

What is a gnotobiotic offspring

Answer 29

Animals used in experiments with known oral flora

Question 30

What is an add-back experiment

Answer 30

In the experiment talked about in class, bacteria capable of causing caries was identified and added after oral flora in experimental animals was known

Question 31

What were the 3 scenarios described in the add back experiment with gnotobiotic mice

Answer 31

1. Non infected animals were added to the same cage as infected animals = Both became carious
2. Non infected animals were inoculated with S. mutans = became carious
3. Non infected animals were given a smear with plaque or feces containing cariogenic bacteria from the infected animals = Became carious

Question 32

What was the main information identified in the add back experiment

Answer 32

1. That caries is an infectious disease
2. Both sugar and plaque bacteria - most specifically s. mutans, Lactobacillus, and Actinomyces are required to cause caries.

Question 33

Name 6 properties to Mutans Streptococci

Answer 33

1. Sugar transport good at low pH
2. Acid production = Homolactic fermenter (only Lactic acid)
3. Aciduricity = Ability to live in acid in decreased pH
   - Acidophilic = Grows well at low pH
4. Produces insoluble Glucan (Mutan) to protect from saliva
5. Utilize extra fructose to make extracellular levans, which they use as snacks between meals.
6. Bacteriocins

Question 34

What is the most virulent factor for S. mutans

Answer 34

The polysaccharide chain or the branched mutan that is made by Glucosyl-transferase to protect the bacteria from saliva and other antibiotic substances.

Question 35

What enzyme in S. mutans has the highest affinity for Sucrose?

Answer 35

Invertase. If there is a large concentration of sucrose, it will also be delivered to Fructosyl transferase and Glucosyl transferase

Question 36

T or F, The branched mutan chain that is made by S. mutans to protect it from saliva is insolubale

Answer 36

True

Question 37

T or F, Fluoride inhibits PEP which decreases the amount of lactic acid produced, why?

Answer 37

True, this occurs by decreasing enolase activitity. The glycolytic pathway is “poisoned” and thus wounds S. mutans

Question 38

What enzyme is used to break down Levan for S. mutans to be able to use it as snack food

Answer 38

Levanase

Question 39

Lactic acid is used by what bacteria?

Answer 39

it is a fuel source for secondary feeders such as Neisseria and Veillonella

Question 40

T or F, Most bacteria will use excess sugars to form extracellular, non-branched, soluble, polysaccharide chains including S. mutans

Answer 40

False, not S. mutans. S. mutans is different and makes branched, insoluble, extracellular, polysaccharide chains that forms a protective dome over the S. mutan micro-colonies within plaque biofilm and also localizes their acid production for longer periods of time on the tooth surface

Question 41

T or F, S. mutans is a homolactate fermentor - it produces 3 lactic acid molecules for every monsaccharide it ferments

Answer 41

False, 2 lactic acid molecule for every monosaccharide it ferments

Question 42

Acidophillic definition:

Answer 42

Competes well in acidic environments

Question 43

Aciduric definition:

Answer 43

relatively resistant to acid

Question 44

What molecule does a similar thing to fluoride by “poisoning” the glycolytic pathway and decreasing the amount of lactic acid produced by S. mutans

Answer 44

Xylitol