Gingivitis associated with dental plaque only a. without other local contributing factors b. with local contributing factors (See VIII A) 2. eCollection 2020. AAP DISEASE CLASSIFICATION (1999) Free Access. These papers are developed by an appointed committee of experts, and the documents are reviewed and ap- proved by the AAP Board of Trustees. Aust Dent J. Clipboard, Search History, and several other advanced features are temporarily unavailable. However, practitioners have difficulty in distinguishing these types because they show similar symptoms. Consequently, a new classification was developed at the International Workshop for a Classification of Periodontal Diseases and Conditions in 1999. In 1997 the American Academy of Periodontology responded to this need and formed a committee to plan and organize an international workshop to revise the classification system for periodontal diseases.