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ePaper created 2016-11-22, 09:52:12 | version 1.38.0
role of the microscope industry report | 43 roots 4 2016 A very effective solution is to use an ultrasonically energised K-file (UEFK), the very instrument that was discarded after the problems identified with ultra- sonic instrumentation in the 1980s. The difference betweenthenandnowisthatinconjunctionwiththe use of the operating microscope the instrument can be used with a great deal of control. Also power set- tingshavebeenconsiderablyreducedtominimisethe possibility of instrument separation. In many situa- tions the UEKF overcomes many of the limitations presented by other ultrasonic instruments. The file can be curved in multiple directions so that the head oftheultrasonichandpiecedoesnotimpairvisualac- cessandthefilecanbeshapedtofollowthecurvature of the canal. When used in conjunction with the op- eratingmicroscope,thefilecanbedirectedtothepart of the canal that has not been prepared by the rotary files.Asize20UEKFwitha2 %taperisanoptimalsize although occasionally a larger file may be used. Be- cause the file is relatively flexible and removes only 0.2 mm of tissue, unnecessary removal of dentine is kept to a minimum (Fig. 6). The file works in multiple ways; it can be easily pre-curvedtofollowthecanalcurvatureandcanbe usedaseitheracuttinginstrumentbyengagingthe tip or as a planning instrument by using the flutes along its working length. When used as a planning instrument, it can be used with variable pressure against the walls of the canal such as in an oval ca- nalextensionorinanisthmus.Thegreaterthepres- sure applied, the more effectively the file cuts den- tineinthesamewayasahandfile,attheexpenseof the ultrasonic effect. As the pressure on the file is reduced, so the ultrasonic effect is increased, achieving the benefits of PUI. The effectiveness of this technique is enhanced by both the flexibility of the k-file so that it can be pre-curved and by its ri- gidity so that it can cut efficiently into a targeted area. The instrument can be used in both modes interchangeably just by varying the lateral pressure placed on the ultrasonic handpiece. In endodontic retreatment cases both the UEKF and thededicatedultrasonictipscanbeusedtogreateffect toremoveendodonticobturationmaterials,separated instruments and posts using minimally invasive tech- niques.WhiletheUEKFhastobeusedatlowpowerset- tingstominimisethepossibilityoffracture,itallowsfor excellent visual control. The dedicated ultrasonic tips such as the EndoSucess ET 25 tip can be precurved to improvevisualaccessandcanbeusedathigherpower settings. It is however only effective at its end. This tip is particularly useful for removing separated instru- ments.Otherultrasonictipsthatcannotbepre-curved canonlybeusedinstraightpartsofthecanal. The removal of gutta-percha from oval canals of- tenpresentsachallengeasrotaryinstrumentsarenot completelyeffective.Arigidultrasonictipismorelike toplasticisethegutta-percha,whiletheUEKFwithits increased tip amplitude, fragments the material. Conclusion Both ultrasonic and the microscope have become an essential part of the armamentarium in endodon- tics. When used together they can produce minimally invasive preparations, which produce cleaner canals inbothprimaryandretreatmentcases.Conventional irrigation strategies should always be employed, par- ticularlyinthoseareasofthecanalsystemthatcannot be visually inspected with the operating microscope such as in the curved apical third. However, the tech- nique described above can aid in the reduction of the bacterialloadwithinthecanalsystemandthiscanre- sult in more predictable outcomes._ Editorial note: A complete list of references are available fromthepublisher. about Dr Anthony S.C.Druttman, MSc,BSc,BChD – specialist in endodontics.Dr Druttman is a past president of the British Endodontic Society and is an active member of the European Society of Endodontology. Fig.5: Inspection of a prepared oval shaped distal canal of a lower molar reveals residual debris apically. Fig.6: Ultrasonically energised K-file used to prepare an isthmus under the operating microscope. Fig.6 Fig.5 42016