Dental Caries

Question 1

Apatite

Answer 1

Naturally occurring isomorphous mineral group that has repeats of Ca5(PO4)3X

5 of Ca (2+)= +10
3 of PO4 (3-) = -9

So… X must have a net charge.

X can be….

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

Question 2

Hydroxyapatite

Answer 2

Ca10(PO4)6(OH)2

Atomic arrangement of hexagonal cells. Can be found as a white powder in its pure form, which is biocompatible for bone implants.

Low bioresorption rate and does not imitate the inorganic portion of our bones and teeth

Question 3

Carbonate-Substituted Hydroxyapatite (CHA)

Answer 3

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

Carbonate substitution increases the solubility of hydroxyapatite and makes it more susceptible to decay

Question 4

Tooth composition is ___% hydroxyapatite by volume, or ___% by weight

Answer 4

85% hydroxyapatite by volume

95% hydroxyapatite by weight

Question 5

Enamel Rods

Answer 5

Made by ameloblasts stacking HA units on top of each other to form crystallites

Enamel rods have a keyhole pattern with a head and a tail

The tail has a higher organic composition with less mineral content– tail is MORE SUSCEPTIBLE TO DECAY

Question 6

Enamel Composition variability based on site

Answer 6

Superficial enamel– more fluoride substitution due to contact with fluoridated water and products

At DEJ– more carbonate substitution
- so, the deeper a cavity penetrates, the more soluble enamel is because there is higher carbonate substitution

Question 7

Lactic Acid effect on phosphate ions

Answer 7

H+ ions from lactic acid complex with the (PO4)3- ions to form phosphoric acid (H3PO4). This drives equilibrium towards the dissolution of hydroxyapatite due to Le Chatlier’s

Question 8

Critical pH

Answer 8

pH at which dissolution of tooth begins via demineralization

Carbonate-substituted hydroxyapatite (CHA) has a critical pH of 5.5

Fluoroapatite has a critical pH of 4.5

Dentin and cementum have critical pH of 6.2-6.7

Question 9

Salivary Buffering

Answer 9

Saliva contains weak base called bicarbonate (HCO3-) which complexes with H+ to form carbonic acid (H2CO3)

This prevents formation of phosphoric acid, which allows the oral pH to neutralize 30 minutes after exposure to acids or sugars

Question 10

Remineralization

Answer 10

Saliva contains Ca2+ ions– drives the equilibrium towards hydroxyapatite formation

Ca2+ and (PO4)3- are reincorporated into tooth structure

Products like MI paste contain buffers that increase the concentration of free minerals in saliva to shift towards reminaralization

Question 11

Fluoroapatite

Answer 11

Ca5(PO4)3F

More stable apatite crystal, stronger bond to calcium ion

Increases tooth hardness and resistance to acid damage

Critical pH is 4.5

Shifts equilibrium towards incorporation of Ca2+ and (PO4)3-. Decreasing enamel solubility (lower critical pH)

Question 12

Enamel Surface Caries Zone

Answer 12

When intact, lesion can be remineralized and is classified as a reversible white spot lesion

White spot lesions may become caveated after 1-2 years, and would be irreversible, requiring restoration.

Question 13

Infected Dentin Caries Zone

Answer 13

bacteria loaded, superficial, mushy, soft, wet, necrotic

Infected dentin must be completely removed

Question 14

Affected Dentin Caries Zone

Answer 14

deeper dry, demineralized, leathery

affected by bacterial toxins/acids, but not invaded by bacteria

Affected dentin does NOT have to be removed during restoration because it does not contain any bacteria

Question 15

Incipient Caries

Answer 15

Reversible

On a smooth surface it will appear white and opaque when air dried

Cannot be detected when wet

Occurs during enamel demineralization and some dentin demineralization stages

Question 16

Cavitated Caries

Answer 16

Irreversible

Enamel surface no intact and the lesion can progress to dentin

Occurs during enamel cavitation to dentin cavitation stage

Question 17

Simple Caries

Answer 17

one surface of a tooth (occlusal most common)

Question 18

Compound Caries

Answer 18

2 surfaces of a tooth (ex. DO)

Question 19

Complex Caries

Answer 19

3 or more surfaces of a tooth (ex. MOL)

Question 20

Acute/Rampant Caries

Answer 20

immediately damages tooth structure

light-colored, very infectious, soft

Question 21

Chronic/Slow Caries

Answer 21

demineralized tooth structure that has nearly remineralized, discolored, and is hard

Question 22

Arrested Caries

Answer 22

brown/black

Becomes caries resistant when exposed to fluoride

Arrested caries often accompanied by sclerotic dentin that prevents bacterial ingress

Question 23

Streptococcus Mutans

Answer 23

Gram Positive Cocci

Acidogenic (makes lactic acid from sucrose by fermentation)

Aciduric (can handle acidic environments without being harmed)

produces glucosyltransferase (GTF) which converts sucrose to extracellular polysaccharides (gluons and fructans) that aid in adherence

produces bacteriocins– kill of competing microbes

Question 24

Bacteria responsible for caries lesions in different locations (Specific Plaque Hypothesis)

Answer 24

Streptococcus Mutans– enamel caries

Lactobacillus– dentinal caries

Actinomyces– root caries

Question 25

Saliva Components

Answer 25

Urea and other buffers

Glycoproteins– string bacteria together to aid in elimination during swallowing

Lactoferrin– binds and sequesters irons that bacterial enzymes need

Lysozyme– breakdown bacterial cell walls

Lactoperoxidase– inactivates certain bacterial enzymes

sIgA– salivary antibodies that bind bacteria

Ca2+/PO4 3-/F ions– remineralization

Statherin, cystatin, histamine, proline rich proteins– proteins used for remineralization