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Dental Tribune Asia Pacific Edition | 3/2017 TRENDS & APPLICATIONS 15 A very effective solution is to use an ultrasonically energised K-type-file (UEKF), the very instru- ment that was discarded after the problems identified with ultra- sonic instrumentation in the 1980s. The difference between then and now is that, in conjunc- tion with the operating micro- scope, the instrument can be used with a great deal of control. Fur- thermore, power settings have been considerably reduced to min- imise the possibility of instru- ment separation. In many situa- tions, the UEKF overcomes many of the limitations presented by other ultrasonic instruments. The file can be curved in mul- tiple directions so that the head of the ultrasonic handpiece does not impair visual access and the file can be shaped to follow the curva- ture of the canal. When used in conjunction with the operating microscope, the file can be di- rected to the part of the canal that has not been prepared by the ro- tary files. A size 20 UEKF with a 2 % taper is an optimal size, although a larger file may occasionally be used. Because 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 easily be pre-curved to follow the canal curvature and can be used as either a cutting in- strument by engaging the tip or as a planing instrument by using the flutes along its working length. When used as a planing instru- ment, it can be used with variable pressure against the walls of the canal, such as in an oval canal ex- tension or in an isthmus. The greater the pressure applied, the more effectively the file cuts den- tine, in the same way as a hand file, at the expense of the ultra- sonic effect. As the pressure on the file is reduced, so the ultra- sonic effect is increased, achiev- ing the benefits of PUI. The effec- tiveness of this technique is en- hanced both by the flexibility of the K-type-file so that it can be pre-curved and by its rigidity so that it can cut efficiently into a tar- geted area. The instrument can be used in both modes interchangea- bly just by varying the lateral pressure placed on the ultrasonic handpiece. In endodontic retreatment cases, both the UEKF and the dedicated ultrasonic tips can be used to great effect to remove endodontic obturation materi- als, separated instruments and posts using minimally invasive techniques. While the UEKF has to be used at low power settings to minimise the possibility of fracture, it allows for excellent visual control. Dedicated ultra- sonic tips, such as the Endo- Sucess ET 25 tip (Satelec), can be pre-curved to improve visual ac- cess and can be used at higher power settings. It is, however, only effective at its end. This tip is particularly useful for remov- ing separated instruments. Other ultrasonic tips that cannot be pre-curved can only be used in straight parts of the canal. The removal of gutta-percha from oval canals often presents a challenge, as rotary instruments are not completely effective. A rigid ultrasonic tip is more likely to plas- ticise the gutta-percha, while the UEKF, with its increased tip ampli- tude, fragments the material. Conclusion Both ultrasonics and the micro- scope have become essential parts of the armamentarium in endodontics. When used together, they can pro- duce minimally invasive prepara- tions, which produce cleaner canals in both primary and retreatment cases. Conventional irrigation strate- gies should always be employed, par- ticularly in those areas of the canal system that cannot be visually in- spected with the operating micro- scope, such as in the curved apical third. However, the technique de- scribed in this article can aid in the reduction of the bacterial load within the canal system and this can result in more predictable outcomes. Editorial note: This mrticle wms first published in Roots—internmtionml mmgmzine of endodontics, Issue 4/2016. A list of references is mvmilm- ble from the publisher. Dr Anthony C.S. Druttman Endodontic spe- cialist Dr Anthony C.S. Druttman is a past president of the British En- dodontic Society and an active member of the European Society of Endodontology. He runs a pri- vate practice in the West End of London. AD 201720172017 Hong Kong International Dental Expo HKIDEAS And Symposium 4 – 6 AU G U ST Hong Kong Convention and Exhibition Centre www.hkideas .org C A L L F O R A B S T R A C T Deadline: 15 April 2017 E A R LY - B I R D R E G I S T R A T I O N Deadline: 15 May 2017 P R E L I M I N A R Y F A C U LT Y Professor Patrick Allen (Singapore) – Geriatric Dentistry Dr. Yu-chih Chiang (Taiwan) – Restorative Dentistry Dr. Jeanette Chua (Malaysia) – Periodontics Dr. Peter Pospiech (Germany) – Prosthodontics Professor Iain Pretty (United Kingdom) – Preventive Dentistry Dr. Alan Reid (Australia) – Medical Emergency N E W H O R I Z O N I N D E N T I S T R Y N E W H O R I Z O N I N D E N T I S T R Y N E W H O R I Z O N I N D E N T I S T R Y N E W H O R I Z O N I N D E N T I S T R Y N E W H O R I Z O N I N D E N T I S T R Y N E W H O R I Z O N I N D E N T I S T R Y N E W H O R I Z O N I N D E N T I S T R Y N E W H O R I Z O N I N D E N T I S T R Y N E W H O R I Z O N I N D E N T I S T R Y N E W H O R I Z O N I N D E N T I S T R Y N E W H O R I Z O N I N D E N T I S T R Y N E W H O R I Z O N I N D E N T I S T R Y N E W H O R I Z O N I N D E N T I S T R Y N E W H O R I Z O N I N D E N T I S T R Y N E W H O R I Z O N I N D E N T I S T R Y N E W H O R I Z O N I N D E N T I S T R Y N E W H O R I Z O N I N D E N T I S T R Y N E W H O R I Z O N I N D E N T I S T R Y N E W H O R I Z O N I N D E N T I S T R Y N E W H O R I Z O N I N D E N T I S T R Y N E W H O R I Z O N I N D E N T I S T R Y Organizer