The Oral Cavity as a Window to Systemic Disease: Diagnostic Clues and Pre-treatment Dental Management for...

The oral cavity frequently harbors the earliest clinical manifestations of systemic diseases, yet a persistent knowledge gap exists between dental and medical training programs regarding oral-systemic correlations. Simultaneously, pre-treatment dental evaluation before oncologic therapy and cardiac surgery remains an underutilized step that, when omitted, can lead to osteoradionecrosis, infective endocarditis, treatment delays, and increased morbidity. This narrative review aimed to catalog oral diagnostic clues, organized by organ system, and to synthesize current pre-treatment dental protocols for oncologic and cardiac surgical patients, targeting interdisciplinary trainees in dentistry and internal medicine. A literature search was conducted across PubMed/MEDLINE, Scopus, Web of Science, and the Cochrane Library. Clinical studies, systematic reviews, guidelines, and consensus statements published between 2000 and 2025 were included. Oral lesions may precede systemic symptoms in conditions including pemphigus vulgaris, Crohn's disease, leukemia, and Addison's disease. The bidirectional relationship between periodontitis and diabetes mellitus is supported by evidence demonstrating increased rates of type 2 diabetes among affected individuals. Current pre-treatment dental protocols endorsed by major professional organizations recommend comprehensive oral evaluation, elimination of active infection, and defined healing intervals before radiation therapy. Integrating oral examination into systemic disease screening and embedding standardized dental evaluation into oncologic and cardiac surgical pathways may improve early diagnosis, reduce complications, and enhance patient outcomes. Interdisciplinary education and standardized medical-dental consultation templates remain important priorities.