Histopathology of enamel caries

Four zones are clearly distinguishable, starting from the inner advancing front of the lesion. These are the (1) translucent zone, (2) dark zone, (3) body of the lesion and (4) surface layer.

Zones of enamecarieTranslucenzone {TZ)

First recognizable zone of alteration

Advancing front of the lesion

Half the lesions demonstrate TZ, not always present

Seen in longitudinal ground sections in clearing (quinoline – RI – 1.62)

TZ appears structureless

Pore volume – I% (compared to 0.1 % of sound enamel)

Dark zone

Lies adjacent and superficial to the translucent zone Positive zone

Shows positive birefringence (in contrast to sound enamel.

Pore volume of 2-4% (polarized light)
Presence of small pores; large molecules of quinoline are unable to penetrate
Micropore system – gets filled with air and becomes dark
Medium like water may penetrate

Body othlesion

Between unaffected, surface and dark zone
Area of greatest demineralization
Pore volume – 5% in periphery and 25in centre
Quinoline imbibition – body appears transparent
Water imbibition – positive birefringence compared to sound enamel Striae of Retzius – prominent

Surfaczone

Quantitative studies – partial demineralization of 1-10% • Pore volume – less than 5% of the spaces

Negative birefringence – water imbibition

Positive birefringence – porous subsurface
All the four zones of enamel caries cannot be seen with same immersion medium.

REFERENCE – Shafers textbook of oral pathology 8th edition

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