Criteria for the Assessment of Adverse Effects of Chemotherapy on the Oral Microflora

Any assessment of an antimicrobial agent for the prevention of dental caries must include a consideration of its possible adverse effects on the oral flora. It must include an examination of the resistance developed by the target pathogens and either developed by, or inherently present in, microorganisms that are known to cause opportunistic infections (yeasts, enteric organisms, Pseudomonas, clostridia, and Staphylococcus aureus). Streptococcus pyogenes should also be included. Insofar as possible, these assessments should be done in preliminary experiments, both in vitro and clinical, rather than in caries trials, so that the large numbers of subjects will not be submitted to unnecessary exposure to the formulation. It must be recognized that some combinations of agent, vehicle, and frequency are more prone than others to cause adverse effects on the oral flora, and will also influence the length of the test period that should be utilized. The microbial assessments should be done on subjects prior to use of the agent, at appropriate frequencies during therapy, and approximately 2 months after the cessation of therapy. Currently, requirements to assess the state of gingival or periodontal health by microbiological examination seem unjustified, because of the relative lack of strong evidence for their diagnostic or predictive value (Ranney, 1989) and because of the ease with which direct measurements of clinical signs and symptoms can be made. Consequently, only the latter should be required.