Intraoral transmission of Streptococcus mutans by a dental explorer.

A streptomycin-resistant strain of S. mutans was introduced into the mouth as adherent growth on an artificial fissure (AF). A second AF, which was initially sterile, was placed in a crown on the opposite side of the dentition. The labeled strain was not found in 8 initially-sterile AFs which were left in vivo for 2 to 6 days and were not examined with a dental explorer. The labeled strain was detected in 7 of 9 initially-sterile AFs which were probed with the dental explorer.