一位57 歲的男性病患被發現下顎骨性阻生的犬齒有不明原因的牙冠吸收。病患身體並無其他系統性疾病，而這顆阻生齒則是在治療下顎側門牙的不合牙冠時，於牙科X-光的檢查中發現的。在這篇病例報告中，將呈現臨床治療的照片以及阻生齒拔除後的病理切片，並探討發生所謂原發性牙冠吸收的可能原因。

A bony impacted mandibular canine in a 57-y/o male patient was found to have coronal resorption with unknown reason. The patient was healthy generally and the condition was found during radiographic examination performed when treating ill-fitting crown of mandibular lateral incisor. Clinical pictures and histological findings were presented and possible etiology was discussed in this case report.