CAD/CAM international magazine of digital dentistry No. 4, 2016

| cone beam supplement use of CBCT in dental implantology 34 CAD/CAM 4 2016 surgery. Ultimately, they also lead to better restora- tiveoutcomes(Busenlechneretal.,JClinPeriodontol. 2015). A recent study to assess prospective implant sites using panoramic radiography versus panoramic scans combined with CBCT imaging revealed that CBCT increases the accuracy of treatment planning as it makes it possible to predict the actual im- plant dimensions required at surgery (Mello et al., BrazOralRes.2014).Furthermore,performingaCBCT scan during the planning phase increases accurate prediction of implant length as well. The overall out- come is a more predictable surgical and restorative result. Superior visualization of anatomical structures Digital imaging can offer clinicians and technicians ahighlyaccuratediagnosticandtreatment-planning toolwiththepotentialtoreformatthescandataand createvirtualmodelsofthepatient’sanatomy.There is also the distinct advantage of accurate measure- ment in any dimension. The generated 3-D volumetric data sets are essen- tiallydistortion-freeandcanprovideprimaryrecon- struction images in multiple planes. One of the main characteristicsofCBCTistheabilitytodepictthefine details of bony structures. It is therefore particularly suited to head and neck diagnostics and dental applications in order to: · Assess the anatomy, available bone height, width, and relative quality for implant surgery planning, and in the management of suspected implant treatment complications. · Determine the three-dimensional topography of the alveolar ridge. · Localize vital anatomical structures in close prox- imity to the planned surgery sites, i.e., the inferior alveolar nerve, mental foramen, incisive canal, maxillary sinus, sinus ostia and nasal cavity floor. · Assess the presence of dentoalveolar pathology in thejawsanddentitionoreventemporomandibular joint (TMJ) pathology that could not be or was not adequately assessed using 2-D radiographic techniques. The reliability of dimensional measurements is clini- cally relevant. Conventional radiological data acqui- sition can lead to millimetre-range deviations from anatomicalreality,whileCBCThasnotonlyshownthe ability to provide sub-millimetre measurements at much higher accuracy, it also provides segmentation accuracy that allows for the creation of accurate 3-D models.Inaddition,CBCTimagingofferspotentialfor implant follow-up, as it produces considerably fewer metal artefacts than MSCT. Parameters that affect radiation dose In practice, higher resolution of bone structures can be obtained with CBCT than with MSCT. Radiation exposure from CBCT is typically considered to be lower than that incurred from common spiral and multi-slice protocols. Depending on the geometrical configuration and the exposure parameters of the system, there is significant variability in the effective radiation dose delivered by CBCT machines. Dose reductioncanbeachievedbyadjustingoperatingpa- rameters. Crucial parameters include exposure time, tubecurrent,thesizeofthefieldofview(FOV)andthe angular degree at which the gantry rotates around the patient’s head._ Table I: Imaging modalities recommended by The American Academy of Oral and Maxillofacial Radiology. Preoperative planning Postoperative implant assessment Initial evaluation Panoramic radiograph,followed by intraoral radiographs to obtain supplemental information. Use of cross-sectional imaging discouraged. Immediate post-op evaluation Intraoral radiographs are recommended in the absence of clinical signs or symptoms.Cross-sectional imaging—particularly CBCT— should only be used immediately postoperatively if the patient presents with implant mobility or altered sensation. Radiographic exam of implant sites Include cross-sectional imaging orthogonal to the site of interest. CBCT considered the imaging modality of choice. Follow-up examination CBCT to be considered if implant retrieval is anticipated.Should not be used for periodic review of clinically asymptomatic implants. Instead,intraoral and,in some cases,panoramic images are adequate for postoperative implant monitoring. Bone augmentation CBCT if augmentation procedures or site development before placing dental implants are required,and if bone reconstruction and augmen- tation procedures have been performed prior to implant placement. Statement on the use of CBCT for research purposes Applicable to all scanning procedures.Adhere to the principle of keeping radiation dosesAs LowAs ReasonablyAchievable (ALARA). Editorialnote:Acompletelist ofreferencesisavailable fromthepublisher. Thisarticleoriginallyappeared inNobelBiocareNews2/2016. Findthefulljournalreferencesat: nobelbiocare.com/news 42016

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