The use of a caries detector dye during cavity preparation: a microbiological assessment.

During cavity preparation conventional tactile and optical criteria are used to assess the caries status of the enamel-dentine junction, cavity preparation being considered complete when this area is hard to a sharp probe and stain free. In the present study 201 cavities were prepared under rubber dam. When caries removal was considered complete using the conventional tactile and optical criteria, a caries detector dye (1% acid red in propylene glycol), which is claimed to stain 'infected' tissue red, was applied. Fifty-two per cent of cavities showed caries dye stain in some part of the enamel-dentine junction. Subsequent microbiological sampling of dye-stained and dye-unstained sites resulted in the recovery of low numbers of bacteria and revealed no difference in the level of infection of the two sites. It is concluded that the conventional tactile and optical criteria are satisfactory assessments of the caries status of tissue during cavity preparation and that subsequent use of a caries detector dye on hard and stain-free dentine will result in unnecessary tissue removal.