implants - international magazine of oral implantology

I industry report technician,radiologist,whererelevantand,ofcourse, thepatient.TheCTVsystemprovidesconvenientlyfor this type of cooperation in planning and carrying out treatment, including the documentation of the re- sponsibilities,concisetreatmentcounsellingwiththe patient and, last but not least, success evaluation. _Error analysis Errors during 3-D-based navigation-guided im- plant placement may have a multitude of causes. As in all error analyses, one must differentiate between coincidental and systematic errors. It can be seen from the principal procedure for template-guided navigated implantation (Fig. 2) and from the number of its sub-stages and different persons involved that errors can—and do—occur in this working process. When analysing errors, it must be kept in mind that navigatedimplantsurgeryinvolvesplanningandop- eratingwithintherangeofmillimetresorevenbelow. In addition, errors during the sub-stages may have grave consequences for the ensuing stages. It is therefore advisable to analyse precisely and develop procedures for avoiding these errors. Errors with the longest-lasting consequences haveturnedouttooccurduringimpression-takingof the jaw planned for implant placement, when taking the3-Dradiographaswellaswhenretransferringthe planned virtual implant position to the model or sur- gical navigation template. The quality of the 3-D radiographic dataset is de- pendent on the image-taking procedure selected, be it CT, CBCT or truncated CBCT. Also, regardless of the machine used, all radiographs are subject to the laws of optics and exhibit distortion, interference and dif- fractionphenomena.Apartfromthat,theimagemay be blurred if the patient moves while it is taken. The actual pixel size in the image sensor of the unit also has an effect, as does the algorithm used for recon- structingtheimageintheX-raymachine.Lastbutnot least, correct setting of the parameters and position- ing the patient properly in the machine are also deci- sive for the quality. Assuming that the impression of the jaw was taken correctly and the planning tem- platewasfabricatedproperly,incorrectpositioningof the template in the patient’s mouth during image- taking also leads to far-reaching planning and trans- fererrors.Errorsduringanddueto3-Dimage-taking are always coincidental and therefore irreparable – which rules out compensating for them with diag- nostics and planning. OncetheradiographhasbeentakenwithanX-ray machine, which is subject to quality management based on the (German) radiation act, during the fol- lowingimage-processing,oftentoolittleattentionis paid to retaining the information included in the pri- mary image data. These processes are often not ade- quately certified and mostly do not comply with the radiationact.Inaddition,alossofdetail/structuralin- formation is thoughtlessly taken into account. The difference between the patient’s position whentheradiographwastakenandtheactualmodel of the jaw is especially crucial for retransferring the virtual implant positions to the model of the jaw. Re- transferring with the various compensation mecha- 38 I implants3_2013 Model mesh with z-level-cut. Rendered model with virtual (inside X-ray-date-file) planned implants. Stl-data (mesh) in connection with picture of alveolar ridge cut and plannes implants with abutments. Stl-data (rendered) in connection with picture of alveolar ridge cut, z-level-picture, planned implants including abut- ments an rd reconstructed channel of N. mandibularis. Figs. 3a–b & 4a–b_A selection of the options for merging the optical scan of the model with 3-D radiological planning data. Figs. 5a–d_Merging the optical scan of the model (red) with an aesthetic set-up (green) using 3-D radiological planning data. Fig. 3a Fig. 3b Fig. 4a Fig. 4b Fig. 5a Fig. 5b Fig. 5c Fig. 5d