Progression of Carious Lesions

Question 1

How much of enamel is inorganic, water and other by weight?

Answer 1

96% IO, 3% water, 1% other

Question 2

How much of dentine is inorganic, water, and organic by weight?

Answer 2

70% IO, 20% O, 10% water

Question 3

What direction does carious dissolution of enamel always follow?

Answer 3

follows the direction of enamel rods (least resistance)

Question 4

A scientist uses solution A to soak a ground section of enamel for histological studies. The scientist then uses the same ground section of enamel, after solution A was dried from the enamel, and soaks it in solution B.

Solution A has a different refractive index than enamel however, solution B has the same refractive index as enamel.

Explain why the scientist would use solution B.

Answer 4

Imbibition of white spot lesions with different solutions allows the visualization of different features.

Solution A, having a different refractive index than enamel will clearly show the surface zone and body of lesion.

Solution B however, having the same refractive index as enamel will also show the dark zone and translucent zones of enamel.

Question 5

Name a compound that has the same refractive index as enamel.

Answer 5

Quinoline

Question 6

The body of a white spot lesion has _______ porosity compared to the dark zone. The dark zone has a _____ porosity when compared the translucent zone.

Answer 6

Lower, Lower

Question 7

What are the differences in non-cavitated carious lesions vs cavitated carious lesions in terms of demineralization patterns?

Answer 7

Non-cavitated = caries doesn’t spread at the DEJ

Question 8

What’s happening here?

Answer 8

Bacterial invasion into dentine tubules

ZB- zone of bacteiral invasion
ZD- Superficial zone of destruction

Question 9

What is a foci of liquefaction?

Answer 9

a coalescence of empty tubules that is caused by rapid lesion progression that destroys odontoblastic processes before tubular sclerosis occurs

Question 10

Reactive dentine only forms if there is bacterial invasion into dentine. True or false?

Answer 10

False

Question 11

What are the zones of a cavitated smooth surface lesion?

Answer 11

1. Outer carious Dentine has the necrotic zone of destruction and Zone of bacterial Invasion
2. Inner carious dentine has the zone of demineralization and sclerotic reaction/translucent zone

Question 12

Are transluscent zones in cavitated smooth surface lesions hypominerazlied? If so, explain why.

Answer 12

False, they are hypermineralized as they are the sclerotic zone whereas odontoblastic processes laid down minerals into the tubules

Question 13

What zone do you expect soft dentine to be in?

How about leathery dentine?

What is leathery dentine?

Answer 13

Soft: Necrotic, contaminated, or demineralized zones

Leathery: Demineralized or translucent zone

Leathery is a tactile manifestation of dentine

Question 14

Where does occlusal caries usually initiate?

Answer 14

Places of plaque accumulation and stagnation:

1) Deep part of groove-fossa system

2) Entrance to deep fissures

Another acceptable answer is
“in a fossa, particularly where 2 interlobal grooves meet”

Question 15

What are 3 factors that influence plaque stagnation and accumulation?

Why do these factors influence plaque stagnation?

Answer 15

Stage of eruption - oreintation of teeth
Functional usage - chewing disrupts plaque; occlusion
Tooth anatomy - pits and fissure variation

Question 16

What shape is formed when carious lesions on the enamel start to increase in size?

Answer 16

Cone shaped, base towards DEJ

Question 17

In a carious lesion, where is the deepest part of the lesion? Explain why this is the case.

Answer 17

Entrance of lesion due to metabolically active plaque

Question 18

A non-cavitated lesion shows no spread along the DEJ. True or false?

Answer 18

True

Question 19

Why does Frank Cavitation cause demineralization spread laterally of the DEJ? What other patterns of demineralization would you see in Frank Cavitation that you wouldn’t see in non-cavitated teeth?

Answer 19

The surface layer no longer regulates the demineralization process, allowing more ions to escape. As well, bacterial invasion causing a signficant increase in metabolically active biofilms within the teeth. Retrograde enamel demineralization can occur as a result.

Question 20

What happened here?

Answer 20

Micro cavitation