Comparative ex vivo evaluation of mechanical properties of three orifice openers

Abstract

Introduction: Orifice openers are routinely used in endodontic practice to facilitate straight-line access, reduce coronal interference, and protect apical shaping files. Their mechanical properties—flexibility, cyclic fatigue resistance, and cutting efficiency—directly influence both procedural safety and clinical outcomes. This study aimed to compare the flexibility, cyclic fatigue resistance, and operative torque (as an indirect measure of cutting efficiency) of three widely used orifice openers: EdgeOne Onyx 9/.09 (EdgeEndo, Albuquerque, NM), EdgeTaper Platinum SX (EdgeEndo), and ProTaper Gold SX (Dentsply Sirona, Ballaigues, Switzerland).

Methods: Thirty-six novel instruments of each brand were randomly assigned to three subgroups (n = 12 per test). Flexibility was evaluated through load-deflection testing at 45° utilizing a universal testing machine. Cyclic fatigue resistance was assessed by determining the number of cycles to failure (NCF) within a stainless-steel artificial canal featuring a 60° curvature and a 5 mm radius. Cutting efficiency was indirectly gauged by recording the operative torque during a 5 mm apical progression in a standardized three-dimensional artificial tooth model. Data were subjected to analysis through one-way ANOVA followed by Tukey's post hoc test (α = 0.05).

Results: EdgeOne Onyx 9/.09 demonstrated significantly superior performance in all three tests: highest flexibility (0.85 ± 0.06 N), greatest cyclic fatigue resistance (1450 ± 120 NCF), and lowest operative torque (0.85 ± 0.19 Ncm). EdgeTaper Platinum SX showed intermediate performance, while ProTaper Gold SX exhibited the lowest values in all parameters. All pairwise differences were statistically significant (p < 0.05).

Conclusions: The outstanding mechanical properties of EdgeOne Onyx 9/.09 across flexibility, fatigue resistance, and cutting efficiency indicate that proprietary heat treatment technologies can substantially improve orifice opener performance. These findings have potential implications for decreasing iatrogenic errors and instrument fractures during coronal flaring procedures. Additional clinical studies are necessary to validate the laboratory observations.