Evaluation of antibacterial efficacy of laser-assisted and passive ultrasonic irrigation methods in disinfection of post space and effects on bond strength of glass fiber posts to radicular dentin.

The aim of this study was to evaluate the antibacterial efficacy of various irrigation activation methods and their effects on the push-out bond strength (PBS) of glass fiber posts (GFP) to radicular dentin in teeth with post spaces infected with E. faecalis. Sixty human mandibular premolar teeth were decoronized. All root canals were shaped using a similar protocol and sterilized in an autoclave. Sterilization was confirmed in 10 randomly selected samples. 50 root canals were obturated. Post spaces were prepared in all samples, and root canals were contaminated with E. faecalis and incubated for 4 weeks. Bacterial growth was confirmed in 10 randomly selected samples. Samples were randomly divided into four groups according to irrigation activation methods (n = 10): Standard needle irrigation (SNI), passive ultrasonic irrigation (PUI), photon-induced photoacoustic streaming (PIPS), and shock wave-enhanced emission photoacoustic streaming (SWEEPS). CFU levels were recorded before and after disinfection by taking samples from the root canals with paper points. GFPs were cemented with self-adhesive resin cement. 2 mm thick sections were taken from the apical, middle, and coronal parts of GFPs, and a push-out test was performed with a universal testing machine. Failure modes were examined under a stereomicroscope (40×). Data were analyzed statistically. None of the irrigation methods tested achieved complete bacterial elimination. However, PIPS and SWEEPS achieved significantly greater bacterial reduction than SNI (ΔCFU [S1-S2], mean: PIPS 0.097; SWEEPS 0.090; SNI 0.045; P < .05). No significant differences were observed in PBS among groups (P > .05); values were generally higher coronally than apically (e.g., SNI 79.1 ± 50.1 vs. 34.1 ± 26.7 MPa), regardless of irrigation method. Adhesive fractures were dominant in all sections in SWEEPS, cohesive fractures were dominant in SNI, and mixed fractures were dominant in PUI. PIPS and SWEEPS are more effective than SNI in reducing bacterial load in the post space; however, this superiority is not reflected in bond strength. Irrigation activation method may affect the dentin surface and fracture type but does not make a decisive difference on PBS.