ROEN0110

I 09 special _ endo-implant algorithm I roots1_2010 Cone-beam computed tomography (CBCT) pro- duces up to 580 individual projection images with isotropicsub-millimetrespatialresolutionenhanced byadvancedimagereceptorsensors.Itisthusideally suited for dedicated dento-maxillofacial CT scan- ning.Whencombinedwithapplication-specificsoft- ware tools, CBCT can provide a complete solution for performingspecificdiagnosticandsurgicaltasks.The imagescanbere-slicedatanyangle,producinganew set of reconstructed orthogonal images, and studies haveshownthatthescansaccuratelyreflectthevol- ume of anatomical defects. The limited volume CBCT scanners best suited for endodontics require an ef- fective radiation dose comparable to two or three conventional peri-apical radiographs and as such are set to revolutionise endodontics (Fig. 6).15,16 Three-dimensional pre-surgical assessment of the approximation of root apices to the inferior dental canal, mental foramen and maxillary sinus are es- sential to treatment planning. The ability of CBCT to diagnose and manage dento-alveolar trauma using multiplanarviews,thedeterminationoftheroot-canal anatomy and number of canals, the detection of the truenatureandexactlocationofresorptivelesionsand the discovery of the existence of vertical and horizon- tal fractures outweigh concerns about the degree of ionisingradiationandtherisksposed.17 ProvidedCBCT isusedinsituationsinwhichtheinformationfromcon- ventional imaging systems is inadequate, the benefits areessentialforoptimisationofthestandardofcare. Patel reported that peri-apical disease can be de- tected sooner and more accurately using CBCT com- pared with traditional peri-apical views and that the true size, extent, nature and position of peri-apical and resorptive lesions can be accurately assessed.18 Usinganewperi-apicalindexbasedonCBCTforiden- tification of apical periodontitis, peri-apical lesions were identified in 39.5% and 60.9% of cases by ra- diography and by CBCT, respectively (p < 0.01). Simonetal.comparedthedifferentialdiagnosisof large peri-apical lesions with traditional biopsy. The resultssuggestedCBCTmightprovideafastermethod to differentially diagnose a solid from a fluid-filled lesionorcavity,withoutinvasivesurgery.19,20 Inspiteof thepresenceofartefacts,thelearningcurverelatedto imagemanipulationandthecost,CBCTwillinvariably betheacceptedstandardofdiagnosticcareandtreat- ment planning in endodontics in the very near future. _Access An improperly designed access cavity will ham- per facilitation of optimal root-canal therapy. If the orientation, extension, angulations and depth are in- accurate,retentionofthenativeanatomyoftheroot- canalspacebecomesprecarious.Therequirementsof access cavity design can be achieved by conceptual and technical regression of the existing configura- tiontothatwhichonewouldlogicallyexpecttohave seen prior to the insults of restoration, function and ageing.Iftertiarydentinewereperceivedofas‘irrita- tionaldentine’ordystrophiccalcificationconsidered ‘decay’, the chamber outline could be used to blue- printaninlayconfigurationfortheaccessdesignthat literally replicates the virgin tooth (Fig. 7). Removal of the existing restoration in its entirety and/or preliminary preparation of the coronal tooth structure for the subsequent full coverage restora- tionwillidentifydecay,fractures,unsupportedtooth structure and expose the anatomy of the underlying Fig. 4a_Panel of anatomic preparations from the classic work by Walter Hess (The Anatomy of the root canals of teeth of the permanent dentition, London, 1925). Fig. 4b_In order to determine the number of root canals and their different morphology, ramifications of the main root canals, location of apical foramina and transverse anastomoses, and frequency of apical deltas, 2,400 human permanent teeth were decalcified, injected with dye and cleared (Vertucci FJ, 1984). Fig. 4a Fig. 4b

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