Because of the confounding factors, additional criteria have been developed by the U.S. public health service for pit-and-tissue caries diagnosis. Which one of the following is NOT a factor of these criteria?
Softening at the base of the pit or fissure
Opacity surrounding the pit or fissure
Softening enamel that may be flaked away by the explorer
Discoloration of pit and groves, limited to the depth of the fissure or pit.