Page 74 - Craniomaxillofacial Implant Surgery - Jeroen P.J. Dings

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Chapter 4
sessions34,36,37. However, optimal timing of inserting implants remains controversial with literature debating advantages in secondary placement including more accurate patient assessment or implant placement and less risk of interference with oncological therapy32,34,37. Disadvantages include placing implants in irradiated tissues with decreased vascularisation and regenerative ability. Collected data in this study significantly show favorable clinical outcomes for implants that are placed during ablative surgery (p = 0.044).
Irradiation of the bone is the most well-known cause of implant failure8,34. Ablative oncology almost inevitably requires adjunctive radiotherapy and hence poses patients to known negative vascular and cellular side effects. As a result, the rate of remodeling of periimplant bone decreases, thereby compromising the bone–implant contact. This usually occurs during the early stage of the osseointegration process36,38-42. Subsequent failure of extra-oral implants seldom leads to osteoradionecrosis34,43. Some studies suggest recovery of bone perfusion 6–12 months after radiotherapy30,43. This study shows a slight favorable outcome for implants being placed in non-irradiated bone compared to implant inserted in irradiated bone with a mean time of 69 months (range 12– 300 months) between irradiation and placement of implant (Table 1). Presumably, if initial healing is already commenced in a nonirradiated osseous environment, a higher bone–implant contact can be achieved. Due to the size of the cohorts and length of observation, our analysis could not lead to significant differences in survival of implants placed in irradiated versus non-irradiated bone. As this cohort is further enhanced with more patients, implants and longer follow-up, future data should employ to verify how irradiation influences (long-term) survival of extra-oral implants.
The relevance of HBO therapy as a requirement for successful maxillofacial implantation remains controversial16,44-47. Pre- and post-operative HBO therapy may improve the success rate of endosseous implants4,8,10,13,17,41,44. It is claimed to revitalize the bone through improvement of the tissue oxygen level, thereby increasing collagen synthesis, neovascularization, and activation of osteoblasts and osteoclasts in irradiated tissue16,41,44-48. The results of this study, however, could not ascertain an additive value for the already irradiated patients receiving HBO treatment.
Favorable locations for orbital prostheses are the lateral portion of the supraorbital rim and the lateral rim due to local increased thickness and bone quality6,12. In this study, no relationship between loss of implants and maxillofacial location could be established.