Methods: Suspensions at an appropriate turbidity of the three standard bacterial cultures (Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli) were separately streaked in at least three directions over the surface of Mueller-Hinton agar plates to obtain uniform growth. Then six disks with each of the following medicaments were placed on the plates (two experimental and one control per plate): ciprofloxacin (positive control), 20% ferric sulfate (experimental), chlorhexidine 2% with Portland cement suspension (experimental), dilute Buckley's formocresol (clinical standard), 20% ferric sulfate with 1.2% chlorhexidine (experimental) and distilled water (negative control). Following overnight incubation, the diameter of the zone of growth inhibition around each disk was measured to the nearest whole mm.
Results: The dilute formocresol disks inhibition zones were less than the zones measured for the positive control by a factor of 50 %. The 2%chlorhexidine and Portland suspension disks had less than moderate zones of inhibition with Pseudomonas aeruginosa compared to the positive control and were more effective in inhibiting bacterial growth than the clinical standard, dilute Buckley's formocresol. However, the 2% chlorhexidine and Portland disks were as effective in inhibiting S. aureus as the positive control disks. The ferric sulfate disks had similar zones of inhibition to the negative control and were less effective in inhibiting bacterial growth than the clinical standard, dilute Buckley's formocresol.
Conclusion: The tested pulpotomy medicaments varied in their ability to inhibit bacterial growth with the 2%chlorhexidine and Portland cement group demonstrating greater effectiveness than the ferric sulfate and dilute formocresol groups. The 2% chlorhexidine and Portland cement group had almost as much effectiveness as the positive control, ciprofloxacin. Disks with a 50% mixture of ferric sulfate (ViscoStat) and 1.2% chlorhexidine (Peridex) zones of inhibition were as effective as formocresol.