The DIAGNOdent laser fluorescence device is designed to detect which class of caries?

Correct answer: A. Occlusal pit-and-fissure caries (Class I)

• A. CORRECT. DIAGNOdent uses a 655 nm diode laser and measures the FLUORESCENCE emitted by bacterial porphyrins in carious tooth structure. Its geometry requires the probe tip to sit perpendicular to the surface being examined, which restricts it to accessible OCCLUSAL pits and fissures — Class I caries.
• B. Anterior proximal surfaces are assessed by direct vision, transillumination and radiographs.
• C. Root caries is diagnosed by visual and tactile examination — the device is not designed for this.
• D. Proximal surfaces cannot be reached by the probe tip; bitewing radiography and transillumination remain the tools for Class II detection.

Note: Its weakness is FALSE POSITIVES: stain, calculus, plaque, prophylaxis paste and even hypomineralised enamel all fluoresce. Use it as an adjunct that supports a clinical decision, never as a stand-alone reason to place a restoration.