Wet cutting in enamel should be used during restorative procedures. According to evidence reported here, dry cutting can induce sufficiently high thermal stresses to fracture the enamel. Temperatures resulting from dry cutting in dentin are high enough to cause biologic pulp damage if the cutting is within 1 to 2 mm of the pulp. Cracks induced in the cavity walls by dry cutting may eventually contribute to marginal failure. A hand-held syringe directing a small, high-velocity stream of water into the cutting region is a more effective cooling technique than an air-water spray.