Brain abscesses caused by odontogenic infection are a rare and life-threatening condition. When dental patients show neurological symptoms such as decreased consciousness, a brain abscess should be considered as a possible diagnosis. We reported that a 65-year-old man visited the emergency room because of left facial edema, high fever, limitation of mouth opening and decreased consciousness. CT, bone scan, and microbiologic examination revealed that the brain abscess originated from left mandibular osteomyelitis with an apical lesion in tooth #36. It was hard to diagnose the location of odontogenic infection. Because there were no evidence of submandibular abscess which is a common path of mandibular posterior infection, early diagnosis was difficult. MRI and radiographs such as facial CT and brain CT revealed procedure that inflammatory findings progressed through the coronoid process, the temporal space, into the subdural space. We compared the present case to previous cases, articles published after the year 2000 in Korea and abroad were investigated. The patient was treated successfully with extraction of causative teeth, drainage surgery, intravenous antibiotics by collaboration between the department of oral maxillofacial surgery and neurosurgery. It is difficult to diagnose brain abscess because central nervous system can be infected by various pathway. As shown in this case, patients with a brain abscess caused by a dental infection should be diagnosed and treated with a multidisciplinary approach. Key words : Brain abscess, Odontogenic infection, Osteomyelitis

Recently, a number of recent reports have reported cases of bone marrow defect (BMD) in the mandible. Among the diseases seen by BMD in radiographs, focal osteoporotic bone marrow defect(FOBMD) is asymptomatic, which is discovered incidentally and localized radiolucency. Because it varies in size, shape, trabeculae and border definition, it needs to biopsy to differential diagnose other intraosseous lesions that show radiological bone marrow defects. This cases report discusses the pre-operation considerations in patients planning to implant the mandible and suspected to have FOBMD in radiographs. The following 4 cases in Dental Hospital of Wonkwang University were taken in panoramic and Cone beam computed tomography(CBCT). In all cases, there were radiolucent lesion diagnosed with FOBMD under radiologic differential diagnosis. In three of cases the implant were placed without treatment plan change and one case changed the treatment plan with removable partial denture. BMD is anatomical state that can affect primary stability of implant fixture. During implant placement, it can lead to unexpected results that fixture is fallen into BMD and the nerve may be damaged after implant fixture removal to cause hyperesthesia. Preoperative diagnosis of these lesions by differential diagnosis with panoramic and CBCT can prevent the complications by changing the treatment plan or paying attention to the manipulation during surgery. Key words : Bone Marrow Diseases, Mandibular Prosthesis Implantation, Differential Diagnosis