The inter-relationship between pulpal and periodontal diseases primarily occurs via the intimate anatomic and vascular connections between the pulp and periodontium. These inter-relationships have been traditionally demonstrated using radiographic, histologic and clinical criteria. Pulpal and periodontal problems are responsible for more than 50 % of tooth mortality.Diagnosis is often challenging because these diseases have been primarily studied as separate entities, and each primary disease may mimic clinical characteristics of the other disease. Periodontal disease has been shown to be related to pulpal disease, and pulpal disease may cause periodontal lesions that behave differently from chronic destructive periodontitis. Fortunately, the combined endodontic-periodontic lesions that affect a single tooth can now be diagnosed and treated successfully, with a predictable prognosis in most cases.