Periodontitis is a highly prevalent oral microbial biofilm-driven chronic inflammatory disease. If unmanaged, periodontitis leads to progressive destruction of the ligamentous attachments of teeth to the alveolar bone and resorption of the alveolar bone. It eventually leads to tooth hypermobility and loss. Periodontitis commonly causes overlying maxillary sinus inflammation (mucositis), reflected on radiographic imaging as maxillary sinus mucosal thickening. While uncommon, advanced periodontitis (stage III/IV) or chronic perio-endo lesions can lead to purulent odontogenic sinusitis (ODS). This article describes periodontitis pathophysiology, diagnostic features, and its potential to cause ODS. Clinical practice guideline conform therapy is very successful in managing periodontitis and enabling long-term tooth retention. Localized tooth extration is reserved to end-stage disease.