Lasers used for cavity preparation have what characteristic?

• A. They are diode-based lasers
• B. They produce no heat at all
• C. They have wavelengths of small penetration depths so no heat transfer to the pulp
• D. They cannot be used for caries removal

Answer: (C)

The important point is how laser energy interacts with tooth tissue. For cavity preparation, you want the energy to be absorbed mainly at the surface so you can remove material without pushing heat deep into the tooth. Lasers used for this purpose often have wavelengths that are rapidly absorbed by water and mineral components in enamel and dentin, giving a shallow penetration depth. That means the energy creates surface ablation while most of the heat stays near the outer layers, minimizing heat transfer to the pulp. In practice, this superficial interaction helps prevent pulpal injury during caries removal. Other statements don’t fit: lasers aren’t all diode-based, they do generate heat, and many lasers can be used for caries removal, so the best description is the shallow penetration that limits heat reaching the pulp.