Osteonecrosis involving the permanent tooth germ in primary dentition is a rare condition that can affect dental and maxillofacial development without correct intervention. This case report presents the successful recovery from drug-induced mandibular osteonecrosis involving the permanent tooth germ in a child. A healthy 4-year-old Chinese girl visited the clinic with an unhealed gingival wound and alveolar bone exposure of the missing primary molar area after 1-day arsenic trioxide sealing during pulp therapy. Radiographic examinations indicated inflammation and sequestrum formation in the jaw. The diagnosis was mandibular osteonecrosis. The treatment plans involved sequestrectomy without extended curettage and removal of the affected permanent tooth germ with systemic antibiotic therapy. A 6-year follow-up revealed no recurrence of the lesion or complications, a gradual increase in bone density of the osteonecrosis area and the development of adjacent permanent tooth germs. A conservative treatment regimen without extended curettage may be an option for young patients with jaw osteonecrosis.

Keywords: arsenic trioxide; deciduous teeth; osteonecrosis; sequestrectomy; tooth germ.

永久牙胚在乳牙列中发生骨坏死是一种罕见的状况，如果不进行正确的干预，可能会影响牙齿和颌面部的发展。本病例报告介绍了一名儿童因药物引起的下颌骨坏死并涉及恒牙胚的成功恢复案例。一名4岁的健康中国女孩因为一次使用三氧化二砷封药进行根管治疗后的一天内，乳磨牙缺失区域的牙龈伤口无法愈合，并且出现牙槽骨暴露而前来就诊。影像学检查显示下颌有炎症和死骨形成的情况。诊断为下颌骨坏死。治疗方案包括去除死骨（sequestrectomy）而不进行广泛的刮治术，并移除受影响的恒牙胚，同时全身使用抗生素治疗。六年的随访结果显示没有病变复发或并发症，且骨坏死区域的骨密度逐渐增加以及邻近恒牙胚正常发育。对于患有颌骨坏死的年轻患者来说，不进行广泛刮治术的保守治疗方法可能是一个选择。

关键词：三氧化二砷；乳牙；骨坏死；去死骨术；牙胚。