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CDEN0310

18 I I clinical report _ imaging cosmeticdentistry 3_2010 and increased competition. There are currently at least 20 CBCT scanners available in the US, with more undergoing the FDA approval process. AllCBCTunitsprovide3-Dinformation;however, each manufacturer approaches the project differ- ently regarding its choice of patient positioning, scanning parameters and viewing software. CBCT unitsaremostcommonlycategorisedbytheirX-ray detection system, image-intensifier detector (II) or flat panel detector (FP). IIs are an older and less ex- pensive technology that generally result in more noise than FPs and need to be preprocessed to re- duce geometric distortions inherent in the detector configuration. The radiation beam is 3-D in shape and similar to photon energy used in digital or con- ventional dental radiology. The receptor captures 2-D images either directly through the FP, which absorbs the photons that are converted to an electric charge, which is measured by the computer or with the II, which captures the photons and converts them to electrons that con- tact a fluorescent screen that emits light captured byachargecoupledevicecamera.Thesoftwarethen reconstructs the sum of exposures using propri- etary algorithms calculated by the manufacturers into as many as 512 axial-slice images. Many CBCT units have a variable field of view (FOV) that allows the clinician to limit the radiation exposure to the region of interest. The limiting fac- tor is the size of the image detector, which comes in a number of sizes depending on the manufacturer, butforthesakeofsimplicitywewillcategorisethem into small (<15 cm), medium (15 cm), large (23 cm) and extra-large (30 cm) FOVs. The maximum image of a small FOV usually can accommodate most of the adult dentition. The maximum medium FOV can accommodatealltheadultdentitionextendinginto the condyles and sinuses. The maximum large FOV imageencompassesthemaxillo-facialanatomy,in- cluding the condyles and most of the orbits. Finally, the extra-large FOV can accommodate the full skull in most cases. Regardless of the volume capacity of the unit, it is important to restrict the FOV for the region of interest, which has a significant effect on the amount of radiation absorbed. DICOMformatimagesarestandardforhandling, storing, printing and transmitting information in medicalimaging,includingthosefromCBCT.In3-D imaging, this becomes a great asset in exporting this data set to third-party software programs that will facilitate image renderings, implant-planning programs and making surgical guides to assist in implant placement (Figs. 4a–c). Fig. 6a_Pre-op CBCT scan with radiographic guide. Fig. 6b_NobelGuide guided surgery plan. Fig. 6c_Post-op implants seated with surgical guide prior to seating laboratory-processed provisional. Fig. 6d_Post-op CBCT scan with implants and immediate provisional prosthesis. Fig. 7a_Prosthodontic simulation using Dental GPS. Fig. 7b_Models being waxed up in the laboratory using Dental GPS. Fig. 7c_Finished provisional restorations using Dental GPS. Fig. 7d_Competed provisional reconstruction. Fig. 7b Fig. 6a Fig. 6b Fig. 6c Fig. 6d Fig. 7c Fig. 7d Fig. 7a Before After