Adhesive bond integrity of Y-TZP post with calcium fluoride infiltrated resin dentin adhesive: An SEM, EDX, FTIR and micro-Raman study

The study aimed to synthesize calcium fluoride (CaF₂) nanoparticles and compare the push-out bond strength and viscosity of experimental adhesive (EA) and EA with 5 wt.% CaF₂ (CAF-5%). The CaF₂ nanoparticles were synthesized and then characterized with scanning electron microscopy (SEM)-energy-dispersive X-ray spectroscopy (EDX), Fourier transform infrared (FTIR), and micro-Raman spectroscopies. CaF₂ nanoparticles were incorporated in the adhesives to yield two groups; gp-1: EA-CAF-0% (control) and gp-2: CAF-5%. Canals of 20 teeth (N = 20) were prepared, and then yttria-stabilized tetragonal zirconia polycrystalline (Y-TZP) ceramic posts were cemented. Adhesives were assessed for push-out bond strength and rheology. CaF₂ filler was seen as irregularly shaped agglomerates on SEM. The EDX analysis demonstrated the presence of calcium and fluoride for the CAF-5% group. The FTIR indicated characteristic bands for CaF₂ containing materials. The micro-Raman spectra of CaF₂ nanoparticles demonstrated the presence of CaF₂ by showing strong bands at 840 cm⁻¹, 1380 cm^-1, and 1400 cm⁻¹ for fluorine and 950 cm⁻¹ and 1080 cm⁻¹ for calcium ions. The highest push-out bond strength values were obtained for CAF-5% group samples (cervical: 9.67 ± 1.46 MPa, apical: 8.66 ± 1.24 MPa), and both adhesives revealed adhesive-dentin interfacial fractures. The CAF-5% adhesive also revealed comparable rheological properties with the controls. The addition of CaF₂ nanoparticles in the adhesive improved its push-out bond strength to Y-TZP post and root dentin, although CAF-5% showed reduced viscosity on rheological assessment (compared with the controls).