Extraoral Disk Implants' Stability in Irradiated and Nonirradiated Bone

Extraoral (EO) implants provide optimal retention for maxillofacial prostheses. One of the best options is disk implants. Often, the patients who required EO implant therapy were subjected to radiation therapy to avoid recurrence after resective surgery. Irradiated bone implantation is challenging due to the low quality of the irradiated bone and its susceptibility to infection. The hypothesis: the disk implant stability will be lower in irradiated bone than in nonirradiated bone. The aim of this prospective clinical study was to assess the differences in disk implant stability in irradiated versus nonirradiated patients. The results showed that disk implants had significantly higher stability in nonirradiated versus irradiated bone for all implant types. Over time, implant stability in nonirradiated bone was significantly higher in all time points with all implant types, while in irradiated bone, stability increased in the first 2 time point assessments, but subsequently it was not statistically significant. Orbital disk implants had significantly better stability in nonirradiated bone; in the nasal site, this was noticeable only for double disks. To summarize, disk implants' stability in nonirradiated bone was significantly better for all implant types. In nonirradiated bone, implant stability increase was noticeable throughout the follow-up period, while in irradiated bone, stability increase was significant only in the osseointegration period (first 2 measurements); subsequent stability changes were not significant. In site-dependent implant stability evaluation, significant stability differences between nonirradiated and irradiated bone were detected in all comparisons of orbital implants. With nasal implants, that difference was found only with double disks.