Background <p>Foreign body aspiration is an uncommon but important cause of localized acquired bronchiectasis in adults and is frequently overlooked in the absence of a clear aspiration history. Retained dental prostheses are particularly hazardous foreign bodies and may remain undetected for decades, leading to irreversible pulmonary damage. We report an exceptionally rare case of long-standing denture aspiration presenting as focal bronchiectasis after a diagnostic delay of 38 years.</p> Case presentation <p>A 67-year-old man presented with a 38-year history of chronic productive cough and progressive dyspnea, refractory to repeated medical therapy. Serial chest imaging over several decades demonstrated cystic bronchiectasis confined to the right lower lobe. Despite extensive investigations, including two fiberoptic bronchoscopies performed abroad, no definitive diagnosis was established. Reevaluation at our institution raised suspicion of an endobronchial lesion. Repeat fiberoptic bronchoscopy suggested a retained foreign body, which was subsequently confirmed and successfully removed by rigid bronchoscopy. The foreign body was identified as a partial denture lodged in the right lower lobe bronchus. Following removal, the patient recalled losing his denture while swimming in 1987, without recognizing aspiration. Post-procedural chest radiography demonstrated improved aeration of the affected lobe, and the patient recovered uneventfully.</p> Conclusions <p>This case represents one of the longest reported retention periods of an aspirated denture and highlights the diagnostic challenges of occult foreign body aspiration in adults. Persistent or unexplained localized bronchiectasis should prompt careful history-taking and thorough bronchoscopic evaluation, even in the absence of a recalled aspiration event. Early recognition and appropriate intervention are essential to prevent irreversible pulmonary sequelae.</p>