White spot lesion histopathology — ORE Part 1 MCQ

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HardApplied Dental SciencesWhite spot lesion histopathologyORE Part 1

A teenager with recent debonding of fixed appliances has opaque white lesions on the labial enamel of upper incisors. The surface is intact and feels rough when dried. The lesions become less visible when wet. What is the correct anatomical/physiological explanation?

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Reveal the answer and explanation

Correct answer: C — A porous subsurface enamel lesion with relative surface layer preservation

Explanation lettering: B = shown as A · D = shown as B · E = shown as C · C = shown as D · A = shown as E

White spot lesions are subsurface demineralization of enamel representing early-stage caries. Histologically, they show a demineralized body beneath a relatively intact surface enamel layer. The opaque white appearance arises from changes in refractive index between the demineralized (porous) and sound enamel; when wet, water-filled pores reduce this mismatch, making the lesion less visible. The surface roughness reflects increased surface porosity. This structure explains why WSLs are remineralizable with fluoride therapy and resin infiltration—the surface layer is preserved, allowing subsurface mineral recovery. Cavitated lesions (A, B) show complete surface loss and are not remineralizable. Pulpal necrosis (C) and root resorption (D) are unrelated to surface caries lesions and have different aetiologies.

Reference: Al-Obaidi R, et al. (2018). Chemical & Nano-mechanical Study of Artificial Human Enamel Subsurface Lesions. Scientific Reports 8:5009. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5840409/ (with supporting evidence from Lopes et al. 2024 and Lee et al. 2009 regarding subsurface demineralization and intact surface layer preservation characteristic of natural white spot lesions)