Comparison Of The Shaping Ability Of ProTaper Gold And WaveOne Gold Nickel-Titanium Rotary Instruments In Simulated S-shaped Root Canals

BackgroundS-shaped canal is also known as double curved canal.During the preparation of S-shaped canal,some procedural errors may occur,such as apical transportation,zip,ledge and danger zone,which may render endodontic treatment difficult.Gold terminal treatment of nickel titanium(NiTi)alloy produces a better arrangement of the crystal structure,thereby leading to increased flexibility and resistance to cyclic fatigue.Gold-wire NiTi instruments trend to display excellent performance when preparing curved canals.ObjectiveThe present study was designed to compare the shaping ability of two Gold-wire NiTi instruments in simulated S-shaped root canals.MethodsForty S-shaped canals in resin blocks were instrumented(20/group)with ProTaper Gold(PTG)and WaveOne Gold(WOG)respectively.Pre-and post-instrumentation images were taken using a dental surgery microscope.The curvature angle and curvature radius were measured before and after instrumentation using Photoshop CS6 software.Pre-and post-instrumentation images were superimposed,and the total amount of resin removed as well as centering ratio were calculated at 10 measuring points from apex point.The data were statistically analyzed with Mann-Whitney U Test,and the significance level was set at 0.05.ResultsNone of the files fractured during instrumentation.Canal aberrations was not observed in post-instrumentation of simulated root canals.At 0,3,6,7,and 9 mm points,PTG group resulted in a higher level of resin removal than WOG group,with significant differences(P<0.05).While at other points,there was no significant difference between two groups.At 0 mm point,the centering ratio of WOG group was less than that of PTG,and the difference between groups was statistically significant(P<0.05).While PTG group resulted in better centering ability than WOG group at 4-6 mm points,and the difference was significant(P<0.05).After prepared by two instruments,the curvature angle of S-shaped canals decreased,while the curvature radius increased.There was no significant difference between WOG group and PTG group at the change of the apical curvature(P>0.05).In the coronal curvature,the change of curvature angle and curvature radius of PTG group were[(5.07 ±1.12)°]and[(1.97±0.33)mm],which were significantly lower than that of WOG group[(8.12±1.94)°and(3.98±1.29)mm](P<0.05).ConclusionWithin the parameters of the present study,both instruments could maintain the morphology of simulated S-Shaped canals well.WOG instruments could retain more dental tissue and better maintain the apical anatomy,and PTG is more advantageous in retaining the crown curvature of S-shaped root canals.