Radiation therapy is an important treatment for oral cancer as it can be the primary treatment of curative therapy and also be used as part of adjuvant therapy. However, serious complications from radiation can occur not only in the cancer cell but also in the normal tissue around the cancer. Tissue density is an important factor to determine the radiation resorption. Bone is 1.8 times more organized than the soft tissue. Also, the maxilla is less dense than the mandible and osteoradionecrosis is more commonly observed in the mandible than in the maxilla. In this study, all patients had been diagnosed of osteoradionecrosis in the mandible. There are many different alternatives for osteoradioecrosis treatment and oseoradionecosis has been defined in many ways. Marx’s classification has been generally accepted method. Marx described osteoradionecrosis as a delay of advanced wound healing protocol due to the failure of wound healing response. According to Marx’s classification, there are 3 stages in osteoradionecorsis; stage 1, the presence of exposed alveolar bone without signs of pathologic fracture, which responds to hyperbaric oxygen (HBO) therapy; stage 2, disease does not respond to HBO, and requires sequestrectomy and saucerization; stage 3, involves full thickness bone damage or pathologic fracture, usually requires complete resection and reconstruction with free tissue [2-4]. Recently, the Notani classification by inferior alveolar canal in radiation picture is accepted to all cases of mandibular osteoradionecrosis. Class I refers to when osteoradionecrosis is limited to dentoalveolar bone. Class II refers to when necrosis progress above inferior alveolar canal. Class III is when oseteoradionecrosis progress to inferior alveolar canal or pathologic fracture occur [7]. Conservative treatments including antibiotic treatment, gargling or enhancing oral hygiene are the basic treatment for osteoradionecrosis. Various treatments have been used in osteoradionecrosis. However according to Happnen et al., 25 ~ 46% of patients have failed the long-term antibiotic treatment and had to receive mandibular resection due to the progression of necrosis [8]. In the study of Weissman and Rankow (1971), patients took a one-year non-surgical treatment such as antibiotic treatment and removal of the oral cavity stimulating factor, but 25% of failed patients still had to receive hemi-mandibulectomy [9]. In study of Drane and Daly, they repeated sequestrectomy to osteoradionecrosis patients and 64% of the patients had to receive segmental mandibulectomy [10]. Thereafter, ultrasonic, high-frequency electromagnetic stimulation and hyperbaric oxygen therapy which can accelerate the formation of new blood vessels and cells were introduced. Marx et al. have proposed a treatment protocol which is a basic requirement to use HBO therapy before and after the surgery combined with surgical debridement [2,4]. Hyperbaric oxygen therapy has been regarded as the effective treatment, but there is still ongoing debate about its effectiveness. Study by Annane et al. showed no benefit of hyperbaric oxygen therapy over placebo [11]. When conservative treatments are unsuccessful, surgical treatment is needed for the management of stage 2 and stage 3 osteoradionecrosis. Resection of wide range of tissue and reconstruction with free flap are the commonly suggested surgical intervention. Aggressive surgical approach is more effective when bone necrosis is advanced [6]. Fibular free flap provide support for dental implantation and denture which helps in recovery of occlusal function. Since a donor site is away from a receiving site, 2 team approaches are available. It is known to have a very high success rate and useful in the reconstruction of mandible. In addition, fibular free flap can provide sufficient amount of bone and soft tissue for mandible reconstruction with a minor risk of donor site complications [12]. Blood vessels harvesting procedure is required for fibular free flap to suppy the tissue at the recipient site and an appropriate length of the blood vessles must be selected to provide anastomosis with no tension. However, the recipient vessels may be available for anastomosis due to a prior neck dissection surgery and a prior radiation therapy. Vein grafts are occasionally required under certain circumstances. Vein grafts from the saphenous vein is considered to be the most versatile and reliable vein graft for an interposition. However, vein graft is known for high risk of thrombosis and hemorrhagic complications. Vein graft should be used carefully [13]. This study demonstrates that fibula free flap is a safe and reliable method for comprehensive functional and esthetic mandibular defect reconstruction. All patients showed the good functional results related to the pain, trismus and chewing. In the study of Lin Wang et al., mandible reconstruction with fibula free flap effectively eliminated pain and trismus, whereas there were no significant improvement of swallow, speech and xerostomia [14]. Our study showed similar result to Lin Wang et al. Furthermore, improvement in occlusal function can be expected through the dental implant installation. Through the long term follow up study, we observed the panoramic view of the miniplate fracture and the bone loss in the mandible ramus and fibular bone junction (Figure 5). In addition, patients showed trismus and incisor deviation. All patients had the occlusal function through non-surgical side of teeth. Since occlusal load was concentrated in the opposite site of teeth after the surgery, stress was concentrated in the ramus fibular bone junction which generated bone resorption and miniplate fracture [15]. To overcome this stress barring effect, more stress shielding methods in the mandible ramus and fibula junction were required, such as increasing miniplate unit. However, further studies are needed on this topic.