Aluminum zirconate nanoparticles in etch and rinse adhesive to caries affected dentine: An in-vitro scanning electron microscopy, elemental distribution, antibacterial, degree of conversion and micro-tensile bond strength assessment

To incorporate different concentrations of Al₂O₉Zr₃ (1%, 5%, and 10%) nanoparticles (NP) into the ER adhesive and subsequently assess the impact of this addition on the degree of conversion, μTBS, and antimicrobial efficacy. The current research involved a wide-ranging examination that merged various investigative techniques, including the application of scanning electron microscopy (SEM) for surface characterization of NP coupled with energy-dispersive x-ray spectroscopy (EDX), Fourier-transform infrared (FTIR) spectroscopy, μTBS testing, and microbial analysis. Teeth were divided into four groups based on the application of modified and unmodified three-step ER adhesive primer. Group 1 (0% Al₂O₉Zr₃ NPs) Control, Group 2 (1% Al₂O₉Zr₃ NPs), Group 3 (5% Al₂O₉Zr₃ NPs), and Group 4 (10% Al₂O9Zr3 NPs). EDX analysis of Al₂O₉Zr₃ NPs was performed showing elemental distribution in synthesized NPs. Zirconium (Zr), Aluminum (Al), and Oxides (O₂). After primer application, an assessment of the survival rate of Streptococcus mutans was completed. The FTIR spectra were analyzed to observe the characteristic peaks indicating the conversion of double bonds, both before and after the curing process, for the adhesive Etch and rinse containing 1,5,10 wt% Al₂O₉Zr₃ NPs. μTBS and failure mode assessment were performed using a Universal Testing Machine (UTM) and stereomicroscope respectively. The μTBS and S.mutans survival rates comparison among different groups was performed using one-way ANOVA and Tukey post hoc (p =.05). Group 4 (10 wt% Al₂O₉Zr₃ NPs + ER adhesive) specimens exhibited the minimum survival of S.mutans (0.11 ± 0.02 CFU/mL). Nonetheless, Group 1 (0 wt% Al₂O₉Zr₃ NPs + ER adhesive) displayed the maximum surviving S.mutans (0.52 ± 0.08 CFU/mL). Moreover, Group 2 (1 wt% Al₂O₉Zr₃ NPs + ER adhesive) (21.22 ± 0.73 MPa) samples displayed highest μTBS. However, the bond strength was weakest in Group 1 (0 wt% Al₂O₉Zr₃ NPs + ER adhesive) (14.13 ± 0.32 MPa) study samples. The etch-and-rinse adhesive exhibited enhanced antibacterial activity and micro-tensile bond strength (μTBS) when 1% Al₂O₉Zr₃ NPs was incorporated, as opposed to the control group. Nevertheless, the incorporation of Al₂O₉Zr₃ NPs led to a decrease in DC. Research Highlights: 10 wt% Al₂O₉Zr₃ NPs + ER adhesive specimens exhibited the minimum survival of S.mutans. 1 wt% Al₂O₉Zr₃ NPs + ER adhesive samples displayed the most strong composite/CAD bond. The highest DC was observed in Group 1: 0 wt% Al₂O₉Zr₃ NPs + ER adhesive.