Lateral and axial cutting efficiency of instruments manufactured with conventional nickel-titanium and novel gold metallurgy

AimTo isolate the effect of metallurgy in lateral and axial cutting efficacy against plastic and bovine dentine substrates by comparing two rotary systems with identical design but manufactured with either conventional nickel-titanium or heat-treated gold alloy. MethodologyA total of 258 ProTaper Universal (PTU) and ProTaper Gold (PTG) Shaping instruments were used. Bending behaviour was assessed to determine the appropriate displacement associated with a 2N force in lateral cutting. Ten instruments of each type were used in lateral action for 60s against bovine dentine or plastic substrates four consecutive times producing four notches in each specimen. Ten further instruments of each type were used in on axial action in four standardized simulated root canals fabricated from 4-mm thick plastic or dentine discs. Both tests were performed at 300rpm in a computer-controlled testing platform. Notch area and torsional load were compared with Student's t-tests. Repeated measures ANOVA was used to compare cutting efficiency across the four different time-points. Pearson correlation coefficients between substrates were also determined. ResultsFor lateral action, all three PTG instruments cut significantly more effectively (P<0.05) than PTU on the plastic substrate. S1 and S2 PTG cut significantly more after 120and 180s (P<0.05) on bovine dentine substrate. For axial action, S1 and S2 PTG were significantly more efficient in cutting at 180s on plastic and 120s on bovine dentine (P<0.05). ConclusionInstruments made from heat-treated nickel-titanium gold alloy had equal or greater cutting efficiency when compared to those made from conventional nickel-titanium.