What is the primary mechanism by which lasers ablate dental hard tissue?

• A. Thermal ablation due to water absorption
• B. Photochemical etching
• C. Mechanical cutting with blade
• D. Ionization and plasma formation

Answer: (A)

The main idea is that laser removal of dental hard tissue happens primarily through heating water inside the tissue. Dental enamel and dentin contain water, and when the laser’s energy is absorbed by that water, it heats up rapidly and boils into steam. The rapid vaporization creates a micro-explosion that disrupts and blows away a thin layer of tissue — a thermomechanical form of ablation. This is why wavelengths strongly absorbed by water (such as those used in common dental lasers) are so effective for precise ablation with limited thermal spread.

Other mechanisms exist, like photochemical effects seen with some UV lasers or plasma formation with very high-peak-power pulses, but they are not the typical primary driver of hard-tissue removal in routine dental laser treatments.