The patients received 1 Mega unit (0.7 g) propicillin orally as oblong tablets one or two hours before surgery.

Mixed continuous cultures of periodontal bacteria were obtained from the enrichment of subgingival plaque by using human serum as a growth medium. After stabilization of the culture by 15 volume changes, a single dose of propicillin, which was dissolved in 0.5 ml of water to give a final concentration of 1 mg/liter in the vessel, was added to the experimental culture. Two subsequent doses of 1 mg/liter were given at 24-h intervals, that is, after 2.4 volume changes, during which the concentration of propicillin in the vessel dropped by dilution until it was approximately 10o of the original value. One day (24 h) after the last addition, a sample was taken from the culture for microbiological analyses. Higher concentrations of propicillin were tested in experimental cultures that were obtained by transferring 2.5 ml from the control culture to a new vessel and then adding serum to a final volume of 5 ml. After batch growth for 24 h, the culture was switched to continuous growth, and after stabilization for 5 to 10 volume changes, the culture was exposed to 5, 10, or 50 mg of propicillin per liter added in a single dose. The addition of antibiotic was repeated after 24 h. Samples for microbiological analyses were taken 24 h after the second addition of propicillin.