Purpose: To report a rare and dramatic complication following immediate dental implant placement in a heavy smoker, who had a delayed diagnosis of uncontrolled diabetes. Materials and methods: In this case report we present the dramatic course of a 64-year old female patient treated with five immediate post-extractive dental implants in the mandible, who developed osteomyelitis, which manifested initially as local peri-implant inflammation and progressed into a spontaneous jaw fracture, despite repeated surgical interventions and antibiotic courses over a 3-year period, until diabetes was diagnosed. Results: A symptom-free status could be achieved only after partial mandibulectomy, treatment of diabetes and reconstruction with a microvascular fibula free flap. Conclusion: In the presence of mandibular osteomyelitis refractory to therapy, yet undiagnosed underlying pathologies, such as diabetes, should be investigated and treated urgently. Keywords: fibula free flap, immediate dental implant placement, osteomyelitis, uncontrolled diabetes