[Osteoradionecrosis and dental implants]

Osteoradionecrosis (ORN) is a severe complication of radiation therapy (RT). A triggering factor is frequently present. It is often a dental, periodental, or surgical traumatism. We report the case of a bilateral ORN: the first lesion appeared 3months after the end of RT around the osteosynthesis plate and was treated by mandibular resection. The second lesion appeared 40months after RT on the opposite side, due to peri-implantitis. Dental implants had been inserted 10years before cancer therapy. No case of ORN in post-implantation RT had been previously reported.

A 75-year-old woman was admitted for a squamous cell carcinoma of the right cheek extending to the intermaxillary commissure, the maxillary tuberosity, the soft palate, the lingual junction, and the vestibule up to the second premolar area. There was no suspicious lymph node. She had undergone dental implant procedure 15 and 10 years before, respectively, one in the second premolar position of the right maxilla and four in the premolar and molar left mandible area. All of them were osseo-integrated and charged. A trans-mandibular buccopharyngectomy with modified radical neck dissection was performed, completed by RT. The total dose of irradiation was 65Gy in the oral cavity and 45Gy on cervical and supraclavicular areas. Delayed mucosal healing was observed on the right mandible and ORN appeared in this area 3months after the end of irradiation. Mandibular resection was necessary. Later, the right maxillary implant was lost, and multiple dental extractions were required. Forty months after RT, peri-implantitis was observed on the left side of the mandible, complicated by ORN and pathological fracture. No surgical reconstruction could be performed because of the patient's age and state. The patient was carrying a complete removable maxillary prosthesis on latest follow-up.

This was the first case of ORN on dental implants placed before RT. RT is a risk factor of implant failure, a relatively rare and unpredictable event. Most often, it causes implant loss and exceptionally ORN. In our case, ORN was bilateral. The first lesion was probably due to surgical trauma. The second one, on the opposite side, was caused by peri-implantitis. Irradiation overdose on the alveolar mandibular ridge, close to the implant, may have been the cause. In our case, there was no severe pain, and slow evolution led to a pathological fracture.