These Guidelines apply to products used to slow or arrest periodontitis. The periodontal diseases represent a wide array of infections characterized by variable microbial clusters and host susceptibility factors that may require different therapeutic approaches. There are two basic ways to control periodontitis: 1) target the putative microbial components with anti-infective strategies; or 2) strengthen or suppress the host response with host modulation agents. Products that are designed for the prevention and/or control of gingivitis are addressed elsewhere and are not considered in these guidelines.