Rec_WZ_Logo_Slogan.png One file endodontics Wave one…. The instrument releases within the elastic phase Instrument is first driven in a cutting direction The subsequent reverse rotation releases the instrument This allows the instrument to advance automatically towards the apex. 10 reciprocation cycles per second correspond to approx. 300 rpm. One complete rotation of 360° is completed in three reciprocating movements. Elastic Limit Dr. Ghassan Yared, Canada Reciprocation - benefits NiTi instruments in reciprocation Plastic phase Explanation of the graph: If an instrument binds in the root canal and is further rotated, it will be subjected to stress in torsion, torque. The structure of the metal will undergo changes. These changes can be reversible or irreversible depending on the amount of the rotation when the instrument is binding. In this example, any rotation between 0 and 400 degrees will not cause irreversible changes to the structure of the metal. Any rotation beyond 400 degrees when the instrument is binding will cause irreversible changes in the structure of the metal. In the end, the instrument in this example fractures at approximately 1100 degrees of rotation. This zone between 0 and 400 degrees where the changes are reversible is called the elastic phase. The zone from 400 degrees to the point of fracture at around 1100 degrees is to the plastic phase. The point of transition between the elastic phase and the plastic phase is called the elastic limit. In this example the elastic limit is at approximately 400 degrees. If a rotary instrument engages dentine and the motor keeps rotating it, the metal of the instrument will undergo irreversible changes. This happens a first time, a second time and a third time and so on... every time the metal will undergo irreversible changes which will cause torsional fatigue and eventually lead to fracture. In reciprocation, the clockwise and counterclockwise angles of rotation should preferably be set at a level lower than the elastic limit (at a level which will not subject the instrument to a torque / stress exceeding the elastic limit). The lower the angles of rotation the safer the procedure, as long as the instrument can still cut dentine, advance apically in the canal and remove the cutting debris in a coronal direction). • • • • • The instrument works within its elastic phase, and so, therefore, relatively stress-free. Due to the fact that the angle in the cutting direction is greater than the reverse angle, the instrument progresses from apically almost automatically. Causes for instrument fractures are: Torsional stress Cyclic fatigue caused by tension and compression The angles of reciprocation are specific to the design of the RECIPROC® instrument so that the instrument does not rotate past its individual elastic limit. • Simplicity •Ony one instrument for one tooth •Sterile – single use •Safety • Minimized risk of fracture • No risk of contamination •Users friendly Reciprocation - benefits No need to worry about when to change to the subsequent instrument Easy to learn (own tests under standard conditions with 13 users working on 520 plastic blocks showed that, after a short training period, 92% of the users were able to prepare three consecutive plastic blocks without procedural errors with RECIPROC, compared to 31% using a leading rotary NiTi system). Reduced risk of instrument fracture thanks to: a. Single use – no risk of over-use b. Reciprocation - the instrument does not rotate past its individual elastic limit thanks to its specific motor settings c. Improved material - M-Wire offers greater resistance to cyclic fatigue than traditional nickel-titanium Thanks to single-use, cross-contamination among patients is eliminated and cross-contamination involving the staff is minimised Less procedural errors compared to rotary preparation (own tests) •Regressive taper • Wave One Instrument050.png Instrument025.png Instrument040.png RECIPROC® Sizes/taper: working part: 16 mm R25 – ISO 25 taper .08 R25 – ISO 25 taper .08 R50 – ISO 50 taper .05 Regressive taper A regressive taper allows for coronal shaping without unnecessary loss of tooth substance, compared to instruments with constant taper such as e.g. Mtwo (25/.06 has a diameter at the end of the working part of 1.21 mm, WaveOne 25/.08 measures 1.22 mm at the end of the working part) Info buttons: Left: dimensions RECIPROC / Mtwo Right: dimensions RECIPROC / WaveOne No additional coronal enlargement necessary with RECIPROC (e.g. with a Gates Glidden drill) Importance of the three peck movement Difference to rotary preparation: The three peck movement is important for practitioners switching from rotary to reciprocating systems. The amplitude of the in-and-out movement should not exceed 3 mm. The instrument should be cleaned after three pecks. Reasons: The instrument does the job of 4-5 rotary instruments and works from crown towards apex without instrument change. If the instrument is not cleaned regularly as it works towards the apex, the flutes will become blocked due to the high cutting efficiency. Friction would increase and the instrument would not be able to work adequately within the canal. This is the reason why the instrument needs to be cleaned in the interim stand after 3 pecks at the latest. Important! Even if the practitioner is of the opinion that the instrument advances easily within the canal, the instrument needs to be cleaned regularly. This is contrary to rotary preparation, whereby the instrument is often allowed to continue to work and penetrate as deeply into the canal as it can advance automatically. With rotary preparation, the instrument is only withdrawn to prepare the canal walls with lateral brushing movements (e.g. Mtwo or ProTaper). Checking if the canal is free with an hand instrument: A hand instrument is inserted to max. 3 mm past the prepared length of the canal. Especially at the beginning of a root canal preparation, the length has not yet been determined. Therefore, the instrument should not be brought to working length. In the majority of cases, the hand instrument is only inserted to full length for exact working length determination after preparation of approx. 2/3 of the estimated working length! Basic rules of power driven endodontics - reciprocation •Movement in amplitudes: up/down 3 mm • •Cleansing of instruments each 3amplitudes • •Reach the apical constriction and go out !