Herrera D, et al. - Researchers performed a critical evaluation of the existing literature on acute lesions occurring in the periodontium (periodontal abscesses [PA], necrotizing periodontal diseases [NPD], and endo-periodontal lesions [EPL]) in order to determine the weight of evidence for the existence of specific clinical conditions that may be grouped together according to common features. Supporting an objective classification system was the ultimate goal of this work. As per findings, they recommend classifying PA according to the etiological factors involved, with the most frequent being those occurring in pre-existing periodontal pockets. NPD were noted to have clear association with the host immune response, which they recommend considering in the classification system for these lesions. They recommend classifying EPLs according to signs and symptoms that have direct impact on their prognosis and treatment, such as presence or absence of fractures and perforations, and presence or absence of periodontitis.