Application of β-Tricalcium Phosphate in Adhesive Dentin Bonding

The study aimed at synthesizing beta-tricalcium phosphate (beta-TCP) nanoparticles and comparing the mechanical properties and dentin interaction of two adhesives: experimental adhesive (EA) and EA with 5 wt.% beta-TCP nanoparticles (beta-TCP-5%). These filler nanoparticles were synthesized and then characterized with scanning electron microscopy (SEM) and micro-Raman spectroscopy. The beta-TCP nanoparticles were incorporated in the adhesives to form two groups: gp-1: EA (control) and gp-2: beta-TCP-5%. These adhesives were characterized by SEM, energy-dispersive X-ray (EDX) spectroscopy and were also assessed for their micro-tensile bond strength (mu TBS) with (TC) and without thermocycling (NTC). Fourier Transform Infrared (FTIR) spectroscopy was performed to evaluate the degree of conversion (DC) of two adhesives. The beta-TCP filler was seen as irregularly shaped agglomerates on SEM. The micro-Raman spectra revealed characteristic peaks associated with beta-TCP nanoparticles. Both adhesives presented suitable dentin interaction, which was demonstrated by the formation of resin tags of variable depths. The EDX analysis verified the existence of calcium (Ca) and phosphate (P) for the beta-TCP-5% group. The greatest mu TBS values were shown by beta-TCP-5% group samples when they were non-thermocycled (NTC) (beta-TCP-5%-NTC: 34.11 +/- 3.46) followed by the thermocycled (TC) samples of the same group (beta-TCP-5%-TC: 30.38 +/- 3.66), compared with the EA group. Although the DC presented by beta-TCP-5% group was comparable to the EA group, it was still lower. The addition of beta-TCP nanoparticles in the adhesive improved its mu TBS and resulted in a suitable dentin interaction, seen in the form of hybrid layer and resin tag formation. Nonetheless, a decreased DC was observed for the beta-TCP-5% adhesive. Future studies probing the effect of different filler concentrations on various properties of the adhesive are warranted.

Automated summary

The study showed that the addition of beta-TCP nanoparticles improved the mechanical properties and dentin interaction of the adhesives. While the beta-TCP-5% group exhibited higher mu TBS values, its degree of conversion was still lower compared to the control group.