Erbium wavelength has an affinity for the water content of hard tissue, enabling less laser energy to ablate caries than enamel or dentin. This statement is:

• A. True
• B. False
• C. Not related
• D. Only for soft tissue

Answer: (A)

Erbium (Er:YAG) laser energy is strongly absorbed by water, so the amount of water in the tissue largely governs how easily it can be ablated. Caries-affected hard tissue tends to have higher water content and greater porosity than sound enamel or dentin, which lowers the energy needed to vaporize and disrupt that tissue. In other words, tissues with more water absorb the Er:YAG energy more efficiently, allowing ablation with less energy. Enamel, being relatively dry, requires more energy, and dentin, while wetter than enamel, is still typically less water-rich than caries-affected tissue. This is why caries can be removed with less laser energy compared to sound enamel or dentin. The property is specific to hard tissue interactions with water-rich tissue, not limited to soft tissue, so the statement is true.