Some discolored spots on the teeth may indicate decay, but not all of them. The dentist may use an explorer, a metal instrument with a sharp tip, to probe for possible decay. Healthy tooth enamel is hard and will resist pressure by the explorer. Decayed enamel is softer. The instrument will stick in it slightly. This is often repairs with a simple filing. White or amalgam are available. White is prettier and amalgam lasts longer. Both have benefits.
Dr. James L. Johnson