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Aim: Bone healing is impaired after irradiation, and implant surgery in irradiated mandibles is associated with lower implant survival compared with normal bone. The aim of this study was to investigate irradiated mandibular bone and implant stability and osseointegration in such compromised tissues. Materials and methods: Thirty-one patients irradiated for head and neck cancer had 125 implants, one-stage with healing abutments installed as part of their oral rehabilitation. Bone biopsies were collected as part of the implant operation from 12 mandibles. All patients received adjunctive hyperbaric oxygen therapy pre- and post-operatively. Implant stability was measured during operation using a resonance frequency device, and for 16 patients, additional implant stability quotient (ISQ) values were recorded up to 20 weeks post-operatively. Results: All bone biopsies showed radiation tissue injuries with focal necrosis and fibrosis. ISQ recorded at the time of operation showed values within normal range, with two thirds above 70. Sixteen implants (12.8%) were lost at an early stage (average of 3 months post-operatively), despite good initial stability. Sixteen patients with 63 implants were followed post-operatively for another 20 weeks. Thirty-seven implants (58.7%) showed ISQ values above baseline, whereas 26 implants (41.3%) had lower values. Soft-tissue problems with prolonged healing around the implants were observed in 12 patients, two of whom developed osteoradionecrosis. Conclusion: Implant surgery in irradiated mandibles with poor bone quality is feasible but associated with increased soft-tissue complications and implant losses. The risk of such complications, however, is outweighed by the benefits of implants to enhance the outcome of oral rehabilitation of head and neck cancer patients. The dispersion of ISQ values makes implant loss in irradiated mandibles hard to predict from resonance frequency analysis alone. |
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