Which imaging modality is used to obtain three-dimensional architecture and viability mapping of dental biofilms?

• A. Scanning electron microscopy
• B. Confocal laser scanning microscopy
• C. Atomic force microscopy
• D. Phase-contrast microscopy

Answer: (B)

Confocal laser scanning microscopy enables optical sectioning and 3D reconstruction of thick, hydrated biofilms while letting you map viability with fluorescent stains. By collecting fluorescence from successive thin focal planes (a z-stack) and using a pinhole to reject out-of-focus light, it builds a true three-dimensional image of the biofilm’s architecture. When combined with viability dyes (for example, live/dead staining that emits separate colors for live and dead cells), it provides a 3D map of which regions are viable throughout the biofilm depth. This approach preserves the biofilm’s natural hydrated state and penetrates beyond surface layers, unlike techniques that require dehydration or only image the surface.

In contrast, scanning electron microscopy gives detailed surface topography but requires fixing and drying and does not show viability or internal structure in 3D. Atomic force microscopy offers nanoscale surface details but is limited to small areas and does not readily provide whole-thickness viability maps. Phase-contrast microscopy shows live cells but lacks optical sectioning and 3D reconstruction needed to visualize architecture and viability throughout a thick biofilm.