An unusual case of an endodontic-periodontal lesion in a 29-year-old man resulting from a habit of opening beer bottle (metal) caps using his mandibular left molar is reported. The patient had been a chronic alcoholic with several emotional problems and was unaware of the injurious nature of his habit. Thus, the importance of a detailed case history and assessment of psychosocial aspects for an accurate diagnosis of such conditions is highlighted. Palabras clave: adventurous habit, bottle-cap opening, endodontic-periodontal, injurious habit, psychosocial, unusual