Comparative evaluation of apical pressure generated by EDDY, GentleWave G4, and passive ultrasonic irrigation: A 3D-printed root canal model

Abstract

Aim: This in vitro study compared the mean and peak apical pressures generated by EDDY, GentleWave G4, and passive ultrasonic irrigation (PUI) in a standardized 3D-printed root canal model.

Methodology: A standardized straight root canal model (apical diameter 0.25 mm, 4% taper, 16 mm working length) was fabricated by resin-based stereolithographic printing. Apical pressure was measured with a validated setup comprising a piezoresistive pressure transducer (PXM409-350; Omega), a DAQ board (USB6008; National Instruments), and LabVIEW software. Distilled water served as the irrigating medium. Twenty measurements were performed per group (n=20, 60 total), with each recording 12,020 data points over 12 seconds. EDDY was activated with a TA-200 air scaler (power level 2, #25/.04 tip); GentleWave G4 was operated per the manufacturer's protocol; and PUI was performed with a Newtron P5 XS ultrasonic unit (power level 6, IrriSafe #20 tip, 2 mm short of the working length). Normality was confirmed by the Shapiro-Wilk test, and group comparisons were performed using Welch ANOVA with Games–Howell post hoc comparisons. The study followed PRILE 2021 reporting guidelines.

Results: Significant differences were observed across all groups for both mean and peak apical pressures (p < 0.001). EDDY produced the highest mean (16.03 ± 4.04 mmHg) and peak (35.53 ± 2.84 mmHg) apical pressures, exceeding the safety threshold in every measurement. GentleWave G4 yielded a negative mean apical pressure (−15.60 ± 7.96 mmHg) and a mean peak of 8.00 ± 6.76 mmHg, remaining below the threshold throughout. PUI generated near-zero mean apical pressure (−0.07 ± 0.05 mmHg) and a mean peak of 2.27 ± 0.05 mmHg, consistently below the critical threshold. All pairwise comparisons were significant (p < 0.001), including GentleWave G4 vs. PUI for peak pressure (p = 0.003).

Conclusion: GentleWave G4 and PUI produced apical pressures below the established safety threshold, whereas EDDY exceeded it in all measurements, indicating a higher risk of periapical irrigant extrusion. Further ex vivo and in vivo studies with anatomically complex geometries are warranted.