Antibiotics in the treatment of periodontal diseases: microbiological basis and clinical applications.

The starting point for defining a therapy, whether in dentistry or the various areas of medicine, is to understand the aetiology and progression of the different illnesses. In this context, it is worth pointing out that periodontal diseases are a group of infections whose primary aetiological factor is the bacteria present in the oral cavity, especially those that colonize the supra- and subgingival tooth surfaces. Many advances, mainly those occurring over the last two decades, greatly facilitated understanding of the aetiopathogenesis of periodontitis, including the microbiota related to each type of disease and the host response. This knowledge has made it easier to indicate more specific therapy, including the use of systemic antibiotics. Systemically administered metronidazole, and especially the combination of metronidazole, amoxicillin and scaling and root planing (SRP) leads to a beneficial change in the composition of the subgingival microbiota by reducing pathogens and allowing the growth of host-compatible species. In addition, the combination of systemic antibiotics and a strict control of supragingival plaque during the active phase of therapy has been showing promising results in the treatment of chronic periodontitis.