A 68-year-old woman received a formocresol pulpectomy of the right lower lateral incisor. The temporary restoration was lost within hours. The next day, the patient suffered continuous pain, the gingiva sloughed, and the alveolar bone was exposed. Four days after treatment, the patient complained of moderate pain. Six days after the pulpectomy, the tooth spontaneously exfoliated. At this time she was referred to our hospital. The clinical diagnosis was chronic alveolitis. Treatment consisted of irrigation of the area. Three weeks after the pulpectomy, the dull pain had subsided, but the alveolar bone of the area showed increased mobility. Five weeks after the pulpectomy, the mobility of the alveolar bone was more significant and a sequestrectomy was performed with the patient under local anesthesia. The sequestrum of necrotic bone was approximately 10 x 5 x 5 mm in size. The patient has been symptom-free for 2 years since the sequestrectomy.