[Prognosis and prognostic factors of endosseous implants in the irradiated jaw]

In comparison to tumor patients not receiving radiotherapy, the rehabilitation of masticatory function after head and neck irradiation is limited due to radiation-induced caries, radioxerostomia, and the risk of osteoradionecrosis. This study focused on implants in the irradiated jaw and on the evaluation of the prognosis and the effect of potential factors on the prognosis. The retrospective study covered 197 implants (47 patients) from 1988 to 1997. The implant prognosis was determined by implant survival statistics (Kaplan-Meier). Losses not related to the implants were censored. In addition, groups were formed according to factors potentially affecting the prognosis. The significance of differences in the groups relative to survival were tested using the log-rank test. Twelve (6.1%) implants from a total of 197 were lost due to peri-implantitis, and eight (4.1%) due to possible biomechanical stress. A total of 52 losses (26.4%) due to death of patients and two (1.0%) due to resection of the jaw were censored; 111 (56.3%) implants remained at recall and the average interval was 33 months. The rates of implant survival (Kaplan-Meier) after 1 and 2 years were 95%, after 3 and 4 years 92%, and after 5 and 6 years 72%. The univariate analysis of group comparisons showed a significantly lower rate of loss after perimplant flap reconstruction (p = 0.036). There was no effect due to the doses of irradiation (p = 0.16), chemotherapy (p = 0.90), or peri-implant osteoplasty (p = 0.84). Although none of the implants inserted before radiotherapy had to be explanted, the implant survival difference in the very heterogeneous groups was not significant (preirradiation, n = 29; postirradiation: n = 156; p = 0.13). According to the literature, the rate of survival of teeth which were sound before radiotherapy (1 year, 75%; 5 years, 45%) was distinctly lower than the survival of enossal implants (1 year, 95%; 5 years, 72%). The high-quality rehabilitation of masticatory function with implant-based protheses is the preferred method of treatment for irradiated tumor patients. In addition, contraindications for enossal implants were ruled out for all studied factors affecting prognosis.