Oral Micro: Microbiology Of Dental Caries

Front 1

Dental Caries

Back 1

disease of the mineralized tissue of teeth (enamel, dentin, and cementum) caused by fermentation of carbs

Front 2

4 Factors in the formation of carious lesions:

Back 2

1. microorganism:
-qualit: known group of bugs that cause caries
-quant:more in # = more infection
2. Metabolic substrates:
-qual: complex sugars vw/ simple sugars
-quant: more simple sugars = more infection
3.Teeth & their environment
-qual: environment (ex: use fluoride)
-quant: how many teeth, more # more caries can attack
4. Time
-qual: frequency (how often eating cookie, all at once or every couple hrs)
-quant: eaten sugary food & how long to develop

Front 3

What can be done to limit the 4 factors in formation of caries?

Back 3

1. Microorganism:
-add OHI
-xylitol
2. Metabolic substrates:
-limit soda and frequency
-OHI
-sugar substitues
3. Teeth & their environment:
-add fluoride
-sealants
-OHI
4. Time:
-eat 3 meals a day
-no snacking on simple sugars

Front 4

Structure & Composition of Tooth Hard Tissues

Back 4

1. Organic matrix: protein (collagen, other), and mucopolysaccharides
2. Mineral: hydroxyapatite
-Ca5(PO4)3(OH)2
3. Water
4. Cells (particularly in dentin)

Front 5

Enamel

Dentin

Back 5

Organic = 4
Mineral = 95
Water = 1

O = 20
M = 70
W = 10

Front 6

Fluoride

Back 6

-will bind to/replace missing OH-
-substitute for hydroxyapatite
-most electroneg. charge -1 in existence
-stronger magnet even tho same charge
-charge will hold structure together a little more firmly
-takes more H+ has more resistance to falling apart

Front 7

Positive Ions:

Back 7

-lead, zinc, strontium, silver, nickel, iron

-binds to Ca++ substitute

Front 8

CO3 Carbonate (-2)

Back 8

disadvantages:
-makes more sensitive to acid
~3% P substituted w/ CO3

advantages:
-kink: doesn't fit together perfectly
-if tooth fractures kinks give it a bit of flex (less fracture)

Front 9

What happens to Hydroxyapatite in presence of acid?

Back 9

-at neutral pH is insoluble
-dissolved; rxn is reversible
-acid = demineralization (structure held by ionized bond falls apart but reversible
-reverse = remineralization
Ca5PH4)3(OH)2 + 14H+
<-->
10Ca + 6(H2PH4) + 2H2O

Front 10

What is critical pH?

Back 10

pH below which dissolution predominates
~5.5

w/ fluoride critical pH = 4.9
stronger magnet, etc.

Front 11

Sites of Caries

Back 11

-gen. char: favorable plaque retention & limited access for saliva
1. pits and fissures
-occlusal surfaces of molars & premolars
-buccal pits of molars
(braces & limited saliva flow)
-palatal pits of maxillary incisors
2. Approximal surfaces of adj. teeth just cervical to contact point
3. Cervical margin just coronal to gingival margin
4. Exposed root surfaces
-in pt. w/ gingival recession
5. margins of deficient restorations
6. tooth surfaces adj to dentures & bridges

Front 12

Sequence of Plaque Development

Back 12

Salivary proteins
Pellicle
Plaque Biofilm
Calculus

Front 13

Pellicle

Back 13

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

Front 14

Characteristics of Pellicle

Back 14

-forms spontaneously on teeth
-bacteria not necessary for formation
-can be removed only by meticulous cleaning
-if removed rapidly forms again (min to hrs)
-protective fxns have suggested but not proben
-forms suitable environment for bacterial bioneer sps adherence & multiplication (plaque biofilm)

Front 15

Plaque Biofilm

Back 15

soft, non-mineralized bacterial deposit that forms on teeth
-suitable env. for acid producing bacteria & diminish saliva protection & mxn
-composition:
>plaque-tooth interface (generally pellicle)
>microbial layers and colonies
>intercellular matrix (insoluble)

Front 16

Calculus

Back 16

plaque biofilm in which inorganic deposits have caused mineralization
-greatly increased risk for developing periodontitis

Front 17

Role of Bacterial Metabolism
Identification of Cariogenic bugs in Gnotobiotic Mice

Back 17

-given human biofilm = caries
-given individual bugs at a time:
Required to cause caries:
>Strep mutans
>Strep
>Lactobacillus
>Actinomyces

Front 18

Characteristics that suggest Strep Mutans dominant cause of caries.

Back 18

S. mutans & S. sobrinus
-attach supra-gingival plaque
-sugar transport good at low pH
-acid production = homoplactic fermenter
-aciduricity = acidophilic (grows well at low pH)
-provides insoluble glucan (mutan) decrease buffer increase acid
-produce intracell polysacharide (snack) extracell levan (fructose polymers)

Front 19

What do plaque bacteria use in our modern diet?
What do they do with it?

Back 19

-sucrose=major consumed in our diet (dissach: glucose & fructose)
1. Invertase: breaks sucrose
-high affinity
2. can undergo glycolytic pathway -> Lactic Acid
3. Fructosyl-transferase
-low affinity
-fructose added to growing chain Levan
-snack food
4. Glucosyl-transferase
-low affinity
-glucose makes insoluble

Front 20

What does Glucan or Dextran do?

Back 20

makes insoluble
-difficult for saliva to wash away
-excludes saliva:
>keeps pH lower longer
>keep Ca & P away (difficult to remineralize)

Front 21

What does Xylitol do?

Back 21

non-metabolized sweetner
-bring X thru bacterial pores
-adds P doesn't metabolize
-bacteria needs to pump out or else toxic (use ATP)

Front 22

How pH affect S mutans & L. Casei?

Back 22

-poor competitor @ pH 7
-good competitor @ pH 5
(most extreme when buffer excluded = xerostomic)

Front 23

Oral bacteria acid production based on pH

Back 23

-pH 7 everyone produces acid
-pH 5 only cariogenic bacteria metabolize

Front 24

Major bacterial sps responsible for these caries in major locations:
1. pits & fissures
2. smooth-surface (enamel)
3. dentin
4. Endodonic
6. Gingival & Perio

Back 24

1. S. mutans
2. S. mutans
3. **Lactinobacilli, Actinomyces, S. mutans
4. Similar to dentin
-S. mutans, A. viscosus, A. ondontolyt. Lactobacilli
5. Gram neg rods (BPB - bacteriodes)
6. gram neg rods facultative & anaerobic

Front 25

Role of dietary carbs in relation to caries.

Back 25

-WWII down bc imported from denmark
-rised when sugar increased in diet
-down because of fluoride
-rise in US because diet

Front 26

List acids produced by bacteria strongest to weakest:

Back 26

1. Lactic acid (lowest pKa)
2. Formic acid
3. Succinic acid
4. Acetic acid
5. Popionic acid

Front 27

Stephan Curve

Back 27

-presence in diet of certian dietary cars leads to rapid & sustained pH drop
-when drops below critical pH w/ caries tooth = demineralization

Front 28

What causes changes in pH below critical value?

Back 28

-presence of plaque
-1st glucose rinse = pH drops dramatically in both w/ plaque
-1 person brushes teeth 2 doesn't
-1: in glucose rinse, mowed the lawn -> pH drop is less dramatic (not at critical pH)
-2: drop still the same

Front 29

Effectiveness of given carbs in promoting caries depends on:

Back 29

1. ability of cariogenic bacteria to metabolize the carb
2. ability of carb molecule to diffuse into plaque
3. frequency more important than amt
-higher freq: higher drop in critical pH more often

Front 30

Saliva
-regulation

Back 30

secretion of salivary glands (main source) & minor glands of the oral mucosa (minor source)
1. activated by autonomic reflexes
-para: increase flow, watery
-symp: low flow, thick
2. flow stimulated by: sight, smell, food in mouth, in stomach
3. flow rate
-stim 1-2 ml/min
-bw meals = small
-sleep: very small

Front 31

Major Fxns of Saliva:

Back 31

1. Aid in swallow/digest of food:
-lubricate food to swallow
-dissolve food = stim of taste bud sensory
-digest foods
2. Protective (chemical & thermal barrier)
-mucoid coating on oral mucous mem
-hot drink = mixes w/ acid & temp dispersed -> not as hot as compared to dry epith (skin)
3. Reduce tendency of caries
-flush away carbs
-contain Ca & P for remineralization
-antimicrobial agents
-acts as chemical buffer (maintain pH)
-source of recycled fluoride

Front 32

Xerostomia

Back 32

dry mouth, effects of lack of saliva:
-tendency to oral ulceration
-difficulty in swallow dry foods
-thermal & chemical sensitivity
-altered taste
-increased tend to caries

Front 33

Why Xerostomia causes increased tendency to caries:

Back 33

-disease
-drugs
-irradiation
-age
-sleep

Front 34

Treatment for lack of saliva:

Back 34

-artificial saliva
-increased oral hygiene
-dietary control (decreased sugars)
-fluoride therapy