The mechanical behavior of nickel-titanium (NiTi) rotary instruments is strongly influenced by alloy composition, manufacturing processes, heat treatments, instrument geometry, and taper. Flexibility is considered one of the most important properties of modern endodontic instruments because it determines the ability of files to follow the original root canal anatomy while minimizing procedural errors. This study aimed to evaluate and compare the influence of instrument design, taper, and innovative manufacturing treatments on the flexibility of small-sized NiTi rotary instruments. Three groups of NiTi instruments designed for the preparation of narrow canals were evaluated: ZARC Slim Shaper 15/.04 (Simit Dental, Italy) and Onyx 15/.03 and 15/.04 (Edge Endo, USA). Ten instruments from each group were tested using a custom-made bending device. Flexibility was assessed at four different locations along the instrument (3, 5, 8, and 20 mm from the tip) using a 45° bending angle. Mean bending resistance and standard deviation values were calculated. Statistical analysis was performed using one-way ANOVA to identify differences among groups. ZARC 15/.04 showed the highest bending resistance at all measurement points, indicating lower flexibility compared with ONYX instruments. The difference increased progressively from the apical to the coronal portion of the instruments. ONYX 15/.03 demonstrated the lowest bending resistance, particularly at 3 mm from the tip. Increasing taper from .03 to .04 significantly increased instrument rigidity. ANOVA analysis showed highly significant differences among groups at all tested distances (p < 0.05). Instrument flexibility is strongly influenced by taper, design, and manufacturing treatments. Evaluating flexibility at multiple locations along the instrument provides additional information compared with conventional single-point bending tests.
Experimental Evaluation of New Rotary Instruments with Innovative Manufacturing Treatments Potentially Affecting Clinical Performance. Part 1: Flexibility
Testarelli L.Supervision
;
2026-01-01
Abstract
The mechanical behavior of nickel-titanium (NiTi) rotary instruments is strongly influenced by alloy composition, manufacturing processes, heat treatments, instrument geometry, and taper. Flexibility is considered one of the most important properties of modern endodontic instruments because it determines the ability of files to follow the original root canal anatomy while minimizing procedural errors. This study aimed to evaluate and compare the influence of instrument design, taper, and innovative manufacturing treatments on the flexibility of small-sized NiTi rotary instruments. Three groups of NiTi instruments designed for the preparation of narrow canals were evaluated: ZARC Slim Shaper 15/.04 (Simit Dental, Italy) and Onyx 15/.03 and 15/.04 (Edge Endo, USA). Ten instruments from each group were tested using a custom-made bending device. Flexibility was assessed at four different locations along the instrument (3, 5, 8, and 20 mm from the tip) using a 45° bending angle. Mean bending resistance and standard deviation values were calculated. Statistical analysis was performed using one-way ANOVA to identify differences among groups. ZARC 15/.04 showed the highest bending resistance at all measurement points, indicating lower flexibility compared with ONYX instruments. The difference increased progressively from the apical to the coronal portion of the instruments. ONYX 15/.03 demonstrated the lowest bending resistance, particularly at 3 mm from the tip. Increasing taper from .03 to .04 significantly increased instrument rigidity. ANOVA analysis showed highly significant differences among groups at all tested distances (p < 0.05). Instrument flexibility is strongly influenced by taper, design, and manufacturing treatments. Evaluating flexibility at multiple locations along the instrument provides additional information compared with conventional single-point bending tests.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
