Erbium laser energy considerations indicate which is true about caries ablation compared with enamel or dentin?

• A. More energy is required for caries ablation than enamel or dentin
• B. The energy required is the same for enamel and dentin
• C. Energy is not affected by tissue type
• D. Less energy is required to ablate caries than enamel or dentin

Answer: (D)

Erbium laser energy coupling depends on tissue composition, especially water content and porosity. Caries-affected tissue becomes demineralized and porous, with higher water content, so it absorbs laser energy more efficiently and reaches the ablation threshold at a lower energy per pulse. Enamel is highly mineralized with little water, making energy absorption less efficient and requiring more energy to ablate. Dentin falls in between, but caries-affected dentin is still more porous and water-rich than sound dentin, so the overall effect is that carious tissue ablates with less energy.