Histopathology of caries

Question 1

Enamel characteristics

Answer 1

95% mineral, 5% water/organic material.
Derived from Ectodermal component
Critical pH: 5.5

Question 2

Enamel Structure

Answer 2

Crystals resemble calcium hydroxyapatite Ca10(PO4)6(OH)2
Carbonate, sodium, fluoride, and other ions make it impure form.
Hydroxyapatite has Knoop Hardness Number (KHN) of 430, while enamel has 370***** KHN.
Enamel crystals = 60-70 nm in width and 25-30 nm in thickness.

Question 3

Dentin and Dentin Structure

Answer 3

Mesenchymal origin
70% inorganic material (hydroxyapatite in form of small plates.
20% organic material: (90% collagen, type 1,3,5. 10% proteins and lipidis)
10% water.
Critical pH: 6.2

Question 4

Changes after 1 week

Macroscopically / Microscopically

Answer 4

Macro: No change visible

Micro: Dissolution of outer enamel surface
Increase in intercrystalline spaces
Increase in porosity, 20-100 um deep

Question 5

Changes after 2 weeks

Macroscopically / Microscopically

Answer 5

Macroscopically: Enamel changes visible after air-drying

Microscopically: Further increase in enamel porosity.

Question 6

Changes after 3-4 weeks

Macroscopically / Microscopically

Answer 6

Macroscopically: Whitish opaque change, Chalky change visible without air-drying

Microscopically: Subsurface lesion starts to form, Extensive loss
of mineral beneath the outer surface.

Question 7

Histology of White spot lesion zones / mineral loss

Answer 7

Surface zone: <5% mineral loss
Body of lesion: 5-30% mineral loss
Dark zone: 2-4% mineral loss
Translucent zone: 1% mineral loss

Question 8

Carious Dentinal Tubule:

Outer Lesion

Answer 8

Bacteria have penetrated this region known as the infected layer. Most of its structure has been lost due to demineralization produced by bacterial acids.

Question 9

Turbid Inner Lesion

Answer 9

The Turbid Zone has lost the peritubular dentin and the intertubular dentin and the intertubular dentin is mostly demineralized. No bacteria are present.

Question 10

Transparent Inner Lesion

Answer 10

The Transparent Zone retains its peritubular dentin and the tubule may be partially filled with minerals. These minerals are known as whitlockite crystals which have a low hardness and content of calcium than apatite.

Question 11

Sub-Transparent Inner Lesion

Answer 11

The sub-transparent zone presents granular shaped crystals and normal dentin is found beneath.