Dental Caries Flashcards by Alexa Breaux

a naturally occurring isomorphous mineral group which contains repeats of the same crystal lattice and molecular structure of Ca5(PO4)3X

apatite

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In the body, apatite is referred to as __________ and is a major component of tissues such as enamel, dentin, and bone.

biological apatite

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What can X be?

Ca5(PO4)3X

Hydroxyl (OH-) –> hydroxyapatite
Fluoride (F-) –> fluorapatite
Chloride (Cl-) –> chlorapatite

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Biological apatite is most commonly found as ________.

hydroxyapatite (HA)
Ca10(PO4)6(OH)2

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Hydroxyapatite has an atomic arrangement of _________ cells. In its pure form, it can be found as a _________ which is biocompatible for bone implants. However, it has a _________ bioresorption rate and it does not imitate the inorganic portion of our bones and teeth.

hexagonal / white powder / low

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a form of naturally occurring hydroxyapatite substituted with carbonate groups (CO3) and is the main component of enamel and dentin

carbonate-substituted hydroxyapatite (CHA)

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How does HA differ from CHA?

carbonate substitution increases the solubility of HA and makes it more susceptible to decay

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Tooth composition is _____% HA by volume or _____% by weight.

85% by volume
95% by weight

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During amelogenesis, ameloblasts stack HA unit cells on top of each other to form crystallites that create…?

long enamel rods or prisms

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orientation of enamel rods

keyhole pattern with a head and tail (tail has a higher organic composition with less mineral content, which makes it more susceptible to decay)

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part of an enamel rod that is more susceptible to decay

tail (higher organic composition and less mineral content)

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T or F: Enamel is structurally and compositionally the same from site to site.

False! Superficially, it has more fluoride substitution due to contact with fluoridated water and products. At the DEJ, it has a higher carbonate substitution. This means that the deeper a cavity penetrates, the more soluble enamel is due to the higher carbonate substitution.

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Describe the process of caries formation.

In the oral cavity, Ca2+ and PO43- are constantly being transferred between the HA of the tooth and free Ca2+ and PO43- ions in the mouth and/or plaque at equilibrium.

Cariogenic bacteria digest sugars via glycolysis –> produce lactic acid as a byproduct of fermentation –> H+ ions complex with the free PO43- ions to form phosphoric acid (H3PO4) –> drives the equilibrium towards dissolution of HA –> results in the loss of Ca2+ and PO43- from the tooth –> demineralization (tooth decay)

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The oral cavity provides an optimal environment with moisture and crevices for bacteria. This allows for growth of cariogenic bacteria which digest sugars via __________ and produce __________ as a byproduct of __________.

glycolysis / lactic acid / fermentation

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states that any alterations to a system of equilibria will result in predictable opposing changes in the system to achieve a new equilibrium state

Le Chatelier’s Principle

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other direct sources of acid (H+) in the mouth that can lower pH

food, drinks, gastric acid from GERD

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describes the change in the pH of the oral cavity which occurs during exposure to sugars and acids as a function of time

Stephan curve

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pH of the oral cavity at rest

What happens upon exposure to acid/sugars?

7 (neutral)

The oral pH decreases rapidly to reach a minimum value within 10 min of exposure.

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If plaque or oral pH reaches or falls below the ________, dissolution of tooth structure begins via demineralization.

critical pH

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critical pH of CHA, FA, dentin/cementum

CHA = 5.5
FA = 4.5
Dentin and cementum = 6.2-6.7

*The higher critical pH of dentin and cementum increases the susceptibility of exposed root surfaces to acid erosion and tooth decay.

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acts as a natural buffer for the acidity and will neutralize the pH

saliva

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How does saliva act as a natural protector against demineralization?

contains a weak base called bicarbonate (HCO3-) which complexes with H+ to form carbonic acid (H2CO3) –> this prevents the formation of phosphoric acid

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How long does it take for bicarbonate in saliva to neutralize the oral pH after exposure to acids or sugars?

30 min

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Saliva contains __________, which can drive the equilibrium towards HA formation (remineralization.)

Ca2+ ions

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This commercial product contains buffers and increases the concentration of free minerals in saliva to shift the equilibrium towards remineralization.

MI paste

Fluoride ions in saliva from fluoridated water or oral hygiene products promote tooth remineralization through the formation of __________.

fluorapatite

FA has a lower critical pH than HA. What does this mean?

a stronger acid challenge is required for tooth demineralization

Which is the more stable apatite crystal? HA or FA

FA (stronger bond to Ca2+, increasing tooth hardness and resistance to acid damage)

Factors that affect pH recovery after sugar or acid exposure:

- bicarbonate in saliva - chewing sugar-free xylitol gum, as it stimulates saliva secretion w/o a drastic pH decline due to the lack of sugar

Xerostomia patients may have a longer pH recovery time of _________ due to decreased saliva production.

over 1 hr

3 ways in which FA promotes tooth remineralization:

- shifting the equilibrium towards incorporation of Ca2+ and PO43- - decreasing enamel solubility with a lower critical pH - preventing the growth of cariogenic bacteria

Caries are the result of the interaction between three things:

- cariogenic bacteria (plaque) - tooth surfaces (host) - fermentable dietary carbohydrates (sugars)

model that incorporates several modifying factors which can affect caries development

Keyes-Jordan model

Progression of pit and fissure lesions? Smooth surface (and root) lesions? Dentinal lesions?

Pit and fissure lesions- widen into inverted V-shape as they progress deeper Smooth surface (and root surface) lesions- wider on surface and narrows as it penetrates enamel as a V-shape Dentinal lesions- widens again due to the higher penetrability of dentin and narrows as it deepens to form V-shape within the dentin

most common location of smooth surface lesions

M/D surfaces at interproximal contacts

This type of lesion can be remineralized when intact and is classified as a reversible white spot lesion.

enamel surface lesion

An unmanaged white spot lesion may become cavitated after how long?

1-2 years

A _________ lesion is classified as irreversible and requires restorative treatment.

cavitated

- bacteria loaded, superficial, mushy, soft, wet, and necrotic - must be completely removed prior to restoring

infected dentin

- deeper, dry, demineralized, leathery affected by bacterial toxins/acids but not invaded by bacteria - does NOT have to be removed during restoration as it does not contain bacteria

affected dentin

caries progression

enamel demineraliation --> dentin demineralization --> enamel cavitation --> dentin cavitation

Caries can be classified based on their progress (extent): On smooth surface, appears white and opaque when air-dried and cannot be detected when wet. Occurs during enamel demineralization and some dentin demineralization stage.

Incipient/reversible

Caries can be classified based on their progress (extent): Enamel surface not intact and the lesion can progress into dentin. Occurs during enamel cavitation to dentin cavitation stage

Cavitated/irreversible

Caries can be classified based on their location: Simple- Compound- Complex- Primary- Secondary/recurrent- Residual-

Simple- includes 1 surface of a tooth (occlusal most common) Compound- includes 2 surfaces of tooth Complex- includes 3 or more surfaces of a tooth Primary- original caries lesion which occurs on virgin tooth surface Secondary/recurrent- occurs at junction of tooth and restoration including small leakage under restoration, marginal gap between the tooth and restoration must be minimized to reduce bacterial penetration Residual- caries that remain even after a tooth preparation is completed

Caries can be classified based on progression rate: - immediately damages tooth structure - light-colored - very infectious - soft

acute/rampant

Caries can be classified based on progression rate: - demineralized tooth structure that has nearly remineralized - discolored - hard

chronic/slow

Caries can be classified based on progression rate: - completely arrested caries - brown/black - it becomes caries-resistant when exposed to fluoride - often accompanied by sclerotic dentin that prevents bacterial ingress

arrested

Arrested caries are often accompanied by _________ dentin that prevents bacterial ingress.

sclerotic

hypothesis that describes caries progression that states that only specific (cariogenic) bacteria in oral cavity can lead to caries development

specific plaque hypothesis

gram-positive cocci that is thought to be a major contributor to enamel caries

Streptococcus mutans

S. mutans produces __________, which converts sucrose into extracellular polysaccharides (glucans and fructans) that aid with bacterial adherence to tooth.

glucosyltransferase (GTF)

3 mechanisms in which S. mutans causes caries:

- produces GTF - produces bacteriocins - acidogenic & aciduric

S. mutans produces ___________ which kill off competing microbes. This allows for cariogenic biofilm (plaque) accumulation on the tooth surface which can promote caries development.

bacteriocins

S. mutans is also _________, as it produces lactic acid from sucrose via fermentation. It is also ________, meaning it can also handle acidic environments without damage.

acidogenic / aciduric

By the specific plaque hypothesis, the following bacteria are thought to be the main cause of:

Streptococcus mutans --> enamel caries Lactobacillus --> dentinal caries Actinomyces --> root caries

Saliva contains several components which help to naturally protect teeth against caries. Which is this? Dilute bacterial acid byproducts to drive equilibrium towards remineralization

urea and other buffers

Saliva contains several components which help to naturally protect teeth against caries. Which is this? Large molecules that string bacteria together to aid in their elimination during swallowing

glycoproteins

Saliva contains several components which help to naturally protect teeth against caries. Which is this? Actively binds and sequesters iron required for bacterial enzymes and function

lactoferrin

Saliva contains several components which help to naturally protect teeth against caries. Which is this? Breakdown bacterial cell walls

lysozyme

Saliva contains several components which help to naturally protect teeth against caries. Which is this? Inactivates certain bacterial enzymes

lactoperoxidase

Saliva contains several components which help to naturally protect teeth against caries. Which is this? Salivary antibodies which bind bacteria

sIgA (salivary IgA)

Saliva contains several components which help to naturally protect teeth against caries. Which is this? Used for tooth remineralization

Ca2+ / PO43- / F- ions

Saliva contains several components which help to naturally protect teeth against caries. Which is this? Proteins used for remineralization

statherin, cystatin, histatin, and proline rich