What is the mechanism of action of lasers in dental hard tissue?

• A. Thermal ablation: energy delivered by laser is absorbed by water in dental tissues, the water reaches its boiling point causing microexplosions in the tooth
• B. Photochemical reaction
• C. Mechanical cutting
• D. Ionization

Answer: (A)

Lasers remove hard dental tissue mainly through a photothermal mechanism. The energy is absorbed largely by the water in enamel and dentin, causing a rapid temperature rise to the boiling point. The sudden vaporization of water creates a microexplosion that disrupts and ejects a thin layer of tissue—that’s thermal ablation. Wavelengths with strong water absorption, such as Er:YAG or CO2 lasers, produce precise, controlled ablation with minimal heat spread when paired with appropriate pulse durations. Other mechanisms like photochemical reactions, mechanical cutting, or ionization (plasma formation) are not the primary means by which lasers ablate hard tissue in typical dental practice.