Cyctic Fatigue Resistance of Four different Nickel-Titanium Rotary lnstruments in Continuous or Reciprocating Motion

INTRODUCTIONManufacturers have recentty introduced new atloys and/or reciprocating motion to improve fracture resistance of nickeltitanium(NiTi) rotary fites (r-l). Recently, two different reciprocating systems were introduced: Reciproc and Wave0ne (4).Manufacturers recommended the use of these fites with a specific motor and the unchangebte and appropriated setting(Reciproc fites with the "RECIPROC ALL" mode and Wave0ne with the "WAVEONE ALL" mode) (5).These two types of presetted reciprocating motion have different angles of rotation and velocity (6).0BJECTTVEAim of the study was to evaluate the resistance to flexuraI fatigue of Reciproc Rz5, Wave0ne Primary, Mtwo and Twisted FiteNiTifites used in continuous rotation or in two different reciprocating motion.MATERIALS & METHODSA total of r8o fites from four brands of NiTi fites marketed two for use in reciprocating motion (Reciproc Rz5 and WaveOnePrimary) and two for use in continuous rotation (Mtwo and Twisted Fite both taper (.06/0.25 tip diameter) were tested.Fourty-five instruments for each brand were divided into three groups (n=r5) on the basis of the motion tested: continuousrotation (group 1- 30o rpm); reciprocaI motion (group z'"ReciprocALL" mode); reciprocatmotion (group 3 - "WaveOneALL" mode). Resistance to cyclic fatigue was determined by counting the numbers of cycles to failure in a 6oo curve with a5-mm radius. Data were anatyzed by two-way analyses of variance.RIESULTSCyclic fatigue resistance of the two type of reciprocating motion "Reciproc ALL" (group z) and "WaveOne ALL" (group 3)was significant higherthan continuous rotation (group r) in every brand (P0.05).When considering the appropriate clinical motion for every brand no significant difference was found in cyclic fatiguebetween Twisted File, Mtwo and Reciproc Rz5, white the cyctic fatigue resistance of WaveOne was [ess than otherthreebrands (P