Page 128 - Craniomaxillofacial Implant Surgery - Jeroen P.J. Dings

126
Chapter 7
a mean follow-up of 35-months (range 8-156 months) was 90.0% for the orbital region and 93.5% for the nasal region. The survival rate of the AA-implants for the orbital and the nasal region was 82.8% and 61.5%, respectively. In concordance with similar studies, implants that remained buried or were removed due to misplacement were considered as successful with regard to their osseointegration32,33.
A systematic review by Chrcanovic et al. on the survival rate of CMF implants revealed an overall risk of 5.5% on CMF implant failure. Similar to our results, the probability of implant failure for the nasal and orbital region was comparable33,34. Implants in the auricular region are shown to have the best prognosis due to the quality and volume of bone, surrounding immobile soft tissues, local hygiene and lower frequency of radiation therapy33,35,36. In contrast, the orbital- and nasal region exhibit limited volume of dense cortical bone and loose trabecular bone structure, respectively16. Orbital location is suggested to have an impact on implant survival with the lateral portion of the supraorbital rim and the lateral rim of the orbit being favorable with regard to implant survival34. A possible explanation for the higher loss in the infraorbital rim is the increased skin mobility leading to soft tissue reactions and subsequent infections, bone loss and implant failure37. However, in our study no relationship between orbital location and loss of implants was found. Toso et al. described a high rate of orbital implant failures shortly after placement attributed to non-osseointegration37. In contrast, Nishimura et al. indicated that longer follow-up periods may lead to an increase in failure rate due to impaired osseous remodeling capacity and peri-implant soft tissue complications38. In concordance with aforementioned systematic review by Chrcanovic et al. (2016), no clear relation was found in our study between the duration of the follow-up period and proportion of implant failures33. Overall patient mortality following oncological surgery in the head- and neck region may lead to overestimation of CMF implant survival. Furthermore, due to the heterogeneous data in literature and multitude of factors influencing implant survival, definitive conclusions have to be drawn carefully.
Surprisingly, no statistic significant difference in implant survival could be established in our study between implants installed in irradiated and non-irradiated bone (p = 0.225). Although, an increased risk on impaired osseointegration due to radiation therapy with subsequent reduced vascularization is widely shown in literature18. Implant surgery in irradiated tissues increases the risk of implant failure and risk of complications33,34.