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14 TRENDS & APPLICATIONS Dental Tribune Asia Pacific Edition | 3/2017 Among the numerous irriga- tion techniques that have also been proposed, there are those that make use of ultrasonic en- ergy. Ultrasonics have played a role in endodontics for many years. Initially, ultrasonic canal preparation was introduced by Richman in 1957,16 and in subse- quent years, there was a vogue for using the ultrasonically energised file to cut dentine in root canals. The technique fell out of favour because lack of control produced ledges, apical perforations and instrument separation.17 In the 1980s, research showed that passive ultrasonic irrigation (PUI) cleaned canals more effectively than ultra- sonic irrigation with simultaneous instrumentation (UI), where the file is intentionally brought into con- tract with the canal wall.18, 19 PUI uses an ultrasonically energised file to irrigate the canal and to remove debris utilising a combination of acoustic micro-streaming and cavi- tational energy (Fig. 4).19–22 ardising the position of the instru- ment in the centre of the canal.24 PUI was found to be effective in apical parts of curved canals and in the isthmus area between two canals. The technique has been shown to remove tissue more ef- fectively than hand irrigation and does not cause damage to the canal wall.23 Variation in the efficacy of PUI reported in some studies was explained by difficulties in stand- Since the introduction of the operating microscope, it has been possible to carry out endodontic treatment at varying magnifica- tions, up to approximately 25 ×, with the aid of direct light that can penetrate into the depths of the root canal. This means that visual inspection of the prepared root canal is possible. Once the canal AD The 65th Annual Meeting of Japanese Association for Dental Research JADR 2017 [ Dates ] Date [ Venue ] 11 / 18 (Sat.) - 19 (Sun.) , 2017 SHOWA UNIVERSITY, Tokyo, Japan Them Forefront of Dental Science [ Theme ] - Toward the Global Standard in Medical Science - Toward the Global Standard in Medical Science - Toward the Global Standard in Medical Science - Toward the Global Standard in Medical Science [ U R L ] U RU RU R h t t p : / / j a d r 6 5 . u m i n . j p h t t p : / / j a d r 6 5 . u m i n . j p h t t p : / / j a d r 6 5 . u m i n . j p h t t p : / / j a d r 6 5 . u m i n . j p h t t p : / / j a d r 6 5 . u m i n . j p [ Congress President ] Ryutaro Kamijo Department of Biochemistry, School of Dentistry, Showa University has been shaped by conventional techniques and dried, the canal can be visually inspected both apically and laterally into the ex- tensions of the canal. Straight ca- nals can be inspected to the apical constriction. Since rotary files straighten the coronal and middle thirds of curved canals, most of these prepared canals can be in- spected to within a few millime- tres of their full working length. Inspection through the micro- scope at about 10× and above can identify those parts of the canal system that have not been touched by the rotary files and contain re- sidual tissue (Fig. 5). These are usu- ally the extensions of oval and flattened canals, isthmuses and fins. The challenge is to prepare these areas to produce a smooth, predictable shape without remov- ing excessive tissue, allowing irri- gants to penetrate into the canals more fully and therefore produc- ing cleaner canals. Our expecta- tions are that delivery into these parts of the canal anatomy of irri- gants and medicaments using a variety of techniques will digest residual tissue material and en- tomb remaining bacteria, render- ing them ineffective. While they have undeniable advantages in the parts of the canal system that cannot be inspected under the mi- croscope, a significant part of the bacterial load within the canal can be removed by the use of a cutting instrument directed towards a specific part of the root canal, such as a fin or isthmus. In the cor- onal part of the canal, this can be done with either a long-shank rosehead bur or a dedicated ultra- sonic instrument. Long-shank burs are very limited in their use, however, because of the length of the shank, relatively large diame- ter of the bur, lack of visual access and their limitation to use in the straight part of the canal. In the deeper parts of the canal, ultra- sonically activated instruments can be used to great effect. [ Congress Secretariat ] Department of Biochemistry, School of Dentistry, Showa University 1-5-8 Hatanodai, Shinagawa-ku, Tokyo 142-8555, Japan TEL: +81-3-3784-8163 FAX: +81-3-3784-5555 [ Management Secretariat ] [ Management Secretariat ] Japanese Association for Dental Research Academic Square Co., LTD. 2-348-302, Ryogae-machi, Fushimi-ku, Kyoto 612-8082, Japan TEL: +81-75-468-8772 FAX: +81-75-468-8773 E-MAIL: jadr65@ac-square.co.jp Fig. 6: An ultrasonically energised K-type-file used to prepare an isthmus under the operating microscope.