Scanning Electron Microscopic Evaluation of Indocyanine Green-Loaded Cerium Oxide Nanoparticle-Mediated Photodynamic Therapy and Potassium Titanyl Phosphate Laser as Post-Space Disinfectant: Effects on Smear Layer Removal and Bond Strength.

This study evaluated the efficacy of novel post space disinfection protocols-indocyanine green-loaded cerium oxide nanoparticle-mediated photodynamic therapy (ICG-CeO₂NPs-PDT), sodium hypochlorite (NaOCl), and potassium titanyl phosphate (KTP) laser irradiation-combined with ethylenediaminetetraacetic acid (EDTA) chelation on smear layer (SL) removal and push-out bond strength (PBS) of glass fiber posts (GFP) to root canal dentin. Forty-eight extracted human premolars underwent standardized endodontic treatment and post-space preparation. Specimens were randomly allocated to four groups (n = 12): Group 1 (saline + EDTA control), Group 2 (2.5% NaOCl + EDTA), Group 3 (KTP laser + EDTA), and Group 4 (ICG-CeO₂NPs-PDT + EDTA). SL removal was quantified using scanning electron microscopy with a four-point scoring system. Following GFP cementation and thermocycling (10,000 cycles), PBS was measured at cervical, middle, and apical regions. Failure modes were classified as adhesive, cohesive, or mixed. Data were analyzed using one-way ANOVA and Tukey's post hoc test (α = 0.05). Groups 2 and 4 demonstrated significantly superior SL removal (scores 1.12-2.45 and 1.17-2.20, respectively) compared to Groups 1 and 3 (3.31-3.99 and 3.40-3.99, p < 0.05). Correspondingly, Groups 2 and 4 achieved 40%-60% higher push-out bond strength (6.71-7.88 MPa and 7.02-8.45 MPa) versus Groups 1 and 3 (4.51-5.27 MPa and 4.73-5.48 MPa, p < 0.05). Groups 2 and 4 exhibited predominantly cohesive failures (50%-80%), while Groups 1 and 3 showed adhesive failures (60%-90%). ICG-CeO₂NPs-PDT demonstrates efficacy equivalent to conventional NaOCl-EDTA irrigation for optimizing glass fiber post adhesion, outperforming KTP laser and saline protocols, warranting clinical evaluation.