Samples of carious dentine will be collected with sterile excavator before and after application of intervention/control agent. The dentine samples will be transferred to sterile container containing a 1mL thioglycollate medium used as a carrier, then this sterile container will be kept in an ice box and taken to the microbiology laboratory for processing, within an hour, by another examiner who is blinded to the type of agent applied after partial caries removal. Samples will be vortexed for two minutes, decimally diluted and 0.1 ml will be plated on Mitis Salivarius Bacitracin agar plates, these plates will be incubated anaerobically for 48 hour at 37ºC then aerobically for 24 hour at room temperature. The number of colonies will be expressed as colony-forming units (CFU/ml) compared before and after application of the antibacterial agent.