Page 18 - Craniomaxillofacial Implant Surgery - Jeroen P.J. Dings

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Chapter 1
The accuracy of guide systems is of significant concern, as computer-planned implant surgery involves a sequence of diagnostic- and therapeutic steps. The overall transfer accuracy of planned implant positions reflects the sum of errors from preoperative scan, digital processing of information through virtual planning software, and the implant installation procedure itself42,46,50,51. Suboptimal placement of implants may induce damage to vital anatomical structures (e.g. nerves, adjacent roots of teeth or even, intracranial tissues)52. The limits of the guided surgery systems are set by the maximum deviations between planning and postoperative position of CMF implants53. However, 3D-printing technologies continue to improve in accuracy, material selection and lower costs.
3.2 Survival rate and timing of placement of implants
As reported in literature, failure rates for CMF implants reveal an overall risk of 5.5%2. However, earlier studies report a wide variety of survival rates for CMF implants. This wide variation can be explained by differences in treatment techniques, used implant types, duration of follow-up, patient factors and criteria for implant success2,6. Implant survival is reported to be site-specific, and among others, related to associated stress distribution, irradiation dose and fractionation5,54,55. However, no clear relationship between radiation treatment and implant survival is established in literature2,6,56. Furthermore, many aspects in relation to oncology therapy remain controversial, such as favorable time of placement and the role of hyperbaric oxygen in case radiation therapy is applied2.
Some studies suggest that pre- and postoperative HBO therapy may improve the eventual success rate of endosseous implants57,58. The studies indicate that there is some benefit in revitalizing the bone through improvement of the tissue oxygen level, thereby increasing collagen synthesis, neovascularization and activation of osteoblasts and osteoclasts in irradiated tissue59. However, results from recent meta-analyses comparing implant survival of dental implants placed in irradiated fields ‘with and without’ the use of HBO showed no statistically significant difference2,60. Careful indication and surgery are required for patients who were exposed to radiotherapy.
Another controversial issue in literature is the influence of timing of placement of CMF implants. A systematic review on the effects of pre- versus post-implantation irradiation therapy on dental implant failure could not establish a significant difference in survival rate61,62.