Evaluating the Dentin‐Adhesive Interface of a Nanoparticle‐Enhanced Universal Adhesive Using Scanning Electron Microscopy and Its Impact on <scp>μTBS</scp> and Degree of Conversion

Evaluation of the effects of various nanoparticles (NPs), titanium dioxide (TiO₂), cerium dioxide (CeO₂), and copper oxide (CuO), when incorporated into universal adhesive (UA), on the micro tensile bond strength (μTBS), degree of conversion (DC), adhesive interface, and resin tag assessment. Before incorporating nanoparticles (NPs) into UA, elemental analysis was conducted on all NP types using energy-dispersive spectroscopy (EDS). The study involved 48 intact human molars, divided into four groups based on UA modification with different NPs: Group 1 (Control), Group 2 (TiO₂NPs), Group 3 (CeO₂NPs), and Group 4 (CuONPs). Samples were restored with composite and light cured. All specimens underwent 10,000 cycles of thermocycling for aging, followed by μTBS testing and failure mode evaluation using a universal testing machine and stereomicroscope. Fourier transform infrared spectroscopy (FTIR) was employed to assess the DC. Scanning electron microscopy (SEM) was utilized to evaluate resin tag length and examine the adhesive interface. Statistical analysis involved one-way analysis of variance (ANOVA) with Tukey's post hoc test for multiple comparisons of μTBS, DC, and resin tag (p < 0.05). Group 3 (2% CeO₂NPs-UA) presented the maximum resin tag length (111.21 ± 2.81 μm) and highest μTBS (15.47 ± 0.88 MPa). However, the lowest bond integrity score (12.64 ± 0.5 MPa) and (76.29 ± 1.69 μm) was presented by Group 1 (0% NPs-UA) (12.64 ± 0.5 MPa) samples. Group 3 (2% CeO₂NPs-UA) (68.54 ± 6.77) adhesive showed DC comparable to 2% CuONPs-UA (67.58 ± 9.65) and UA-unmodified (74.33 ± 8.59) (p > 0.05). The UA enhanced with CeO₂NPs and CuONPs can be viewed as a viable option, given its improved μTBS and resin tag length as observed through SEM. Furthermore, the modification of UA using CeO₂NPs and CuONPs exhibits a DC comparable to that of the unmodified adhesive control.