In Vitro Evaluation of Apical Transportation Induced by Single- and Dual-Thermally Treated NiTi Instruments

Martensitic endodontic instruments, thanks to their flexibility, produce less apical transportation compared to austenitic instruments. Recently, a sequence of instruments featuring a dual thermal treatment applied separately to the tip and the shank was introduced with the aim of achieving a tip with enhanced cutting capacity and a more flexible body. The increased stiffness at the tip could potentially lead to greater apical transportation. The aim of this study was to compare apical transportation produced by SlimShaper (single thermal treatment) and SlimShaper PRO (dual thermal treatment) nickel-titanium (NiTi) instruments (Zarc4Endo, Spain) in standardized simulated canals.

Forty-four standardized J-shaped resin blocks were used, divided into two groups (n = 22): Group A (shaped with SlimShaper up to size 25/0.04) and Group B (shaped with SlimShaper PRO up to size 25/0.04). Each block was photographed before and after shaping, and the images were superimposed to evaluate apical transportation. Data normality was verified with the Shapiro-Wilk test, and homogeneity of variances was assessed with Levene's test. Since assumptions were met, comparisons between the two groups were performed using the independent Student's t test, with the level of significance set at p  < 0.05.

Mean apical transportation was 0.08423 mm (SD 0.01049) for SlimShaper and 0.08609 mm (SD 0.01102) for SlimShaper PRO, with no statistically significant difference between groups (p = 0.57).

Under the conditions of this study, the dual-thermally treated SlimShaper PRO instruments did not produce greater apical transportation than the single-thermally treated SlimShaper instruments.