Dental Tribune United Kingdom Edition

Experience some of the world’s greatest speakers in a breathtaking setting Innovate with a brand new format of lectures Network with your peers and speakers over a fantastic lunch and drinks reception The conference will be held in the exclusive Altitude 360° Altitude 360°, 29th Floor, Millbank Tower, 21-24 Millbank, London, SW1 4QP Book now to secure your place Places are limited, book now with Smile-on on call 020 7400 8989 or email info@smile-on.com G. John Schoeffel Gary Glassman Simon Cunnington Gianluca Gambarini First 50 delegates to sign up enjoy the ultimate lunch and learn with our speakers Friday 1st February 2013 the UK’s Premium Endodontic Conference Early Booking price £199 (usual price £249) Influence of a novel reciprocation movement on cyclic fatigue of Twisted Files (TF) instruments 21ClinicalOctober 22 - 28, 2012United Kingdom Edition N ickel-titanium (NiTi) rotary endodontic in- struments offer greater flexibility (Xu 2006) and their super-elasticity reduces the re- storing force, thereby allowing improved canal shaping and re- duced canal transportation (Gergi et al. 2010). However, separation via tor- sional and cyclic fatigue is still a risk with NiTi instruments (Yared 2004, Pruett et al. 1997). Cyclic fa- tigue occurs when a metal is sub- jected to repeated cycles of ten- sion and compression that causes its structure to break down, ulti- mately leading to fracture (Para- shos et al. 2004). Torsional fatigue is the twisting of a metal about its longitudinal axis at one end, while the other end is in a fixed position (Sattapan et al. 2000). Cy- clic fatigue is most apt to occur in a canal with an acute curve and a short radius of curvature, as de- fined by Pruett et al. (1997) and is the leading cause of NiTi instru- ment separation. Increasing the resistance to file separation has been a focus in new NiTi rotary instrument manufacture and de- sign (Tripi et al. 2006). Instruments have been tra- ditionally used with a continu- ous motion, but recently a new approach to the use of NiTi in- struments in a reciprocating movement has been introduced (Yared 2008). ). In the proposed technique, only one F2 ProTaper NiTi rotary instrument is used for the canal preparation in a clock- wise (CW) and counterclockwise (CCW) movement. The CW and the CCW rotations used by Yared were four-tenth and two-tenth of a circle respectively and the rota- tional speed was 400 rpm (Yared 2008). The concept of using a sin- gle NiTi instrument to prepare the entire root canal is interest- ing, and it is possible due to the fact that reciprocating motion is thought to reduce instrumenta- tion stress. Recent literature data show that reciprocating motion can extend cyclic fatigue resist- ance of NiTi instruments when compared to continuous rotation (De Deus et al. 2010; Yu et al. 2010). These preliminary positive results need further studies, be- cause many different reciprocat- ing movement and many different instrument designs can be used in clinical practice, thus affecting the overall results. The aim of present study was to compare cyclic fa- tigue resistance of Twisted files (TF, Sybron Endo, Glendora, Ca) instrument using new innovative angles of reciprocation to evalu- ate if the new reciprocating mo- tion could affect the lifespan of tested instruments. The null hy- pothesis is that there is no differ- ence in fatigue resistance related to the different rec. Material and methods 20 TF tip size 25 taper .08 NiTi instruments were randomly di- vided in two groups (n=10 each). All instruments had been in- spected by using an optical stereo- microscope with 20x magnifica- tion for morphologic analysis and for any signs of visible deforma- tion. If defective instruments were found, they were discarded. All instruments were submit- ted to cyclic fatigue tests. Group Gianluca Gambarini discusses increasing the resistance to file separation page 22DTà