Comparison of the cyclic fatigue resistance of original and replica-like files: a systematic review and meta-analysis

Objectives: This systematic review and meta-analysis aimed to evaluate the existing literature and quantitatively analyze the cyclic fatigue resistance of original and replica-like nickel-titanium endodontic files. Methods: A comprehensive search was conducted across four electronic databases up to July 6, 2025, following PRISMA guidelines (PROSPERO: CRD420251086699). The methodological quality of included studies was assessed using criteria adapted from previous in vitro systematic reviews. Publication bias was evaluated using Egger's test and the trim-and-fill method. A random-effects meta-analysis was performed to compare the cyclic fatigue resistance of original and replica- like files using time to fracture (TTF) and number of cycles to fracture (NCF) as outcomes. These were expressed as standardized mean differences (SMDs) with 95% confidence intervals (CIs). Heterogeneity was analyzed using the I² statistic. Results: A total of 14 studies involving 1,276 endodontic files (nine original and 31 replica-like types) were included. Based on TTF values, replica-like files showed significantly greater cyclic fatigue resistance than original files (SMD, -0.845; 95% CI, -1.268 to -0.423; p < 0.001). However, NCF-based analysis revealed no statistically significant difference (SMD, -1.532; 95% CI, -3.615 to 0.550; p = 0.149). Conclusions: Replica-like files exhibited cyclic fatigue resistance comparable to original instruments and may be considered potential alternatives. However, due to high heterogeneity and methodological variability, these findings should be interpreted with caution.