Abstract
The study aimed to synthesize, characterize, and assess dentin bonding, ion-release, and degree of conversion (DC) of experimental adhesive (EA) with and without 5 wt% and 10 wt% calcium fluoride (CaF2) nanocrystals. The CaF2 nanocrystals were synthesized and characterized with scanning electron microscopy (SEM), line-Energy Dispersive X-Ray (EDX) spectroscopy, Fourier-transform infrared (FTIR).and micro-Raman spectroscopy techniques. Adhesives were characterized using micro-tensile bond strength test (mu TBS), SEM-EDX spectroscopy, inter-facial failure investigation, adhesive-dentin interface examination, ion release measurements, FTIR, and DC analysis. One hundred five (n = 105) teeth were collected, their dentinal tissue was exposed, and the adhesives were applied pre-characterization of the adhesives. On SEM, CaF2 nanocrystals were seen as irregularly shaped agglomerates. The EDX mapping demonstrated calcium and fluoride's presence for the CAF-5% and CAF-10% groups. The FTIR and micro-Raman spectra indicated characteristic bands for CaF2 containing materials. For the NTC samples, the highest mu TBS (33.87 +/- 3.26 MPa) was observed for CAF-10%. For the TC samples, the highest mu TBS (30.48 +/- 3.41 MPa) was observed for CAF-10%. Adhesive type failures were most common and the CaF2 containing adhesives revealed comparable resin tag formation to the controls. The presence of calcium and fluorine on EDX analysis was observed for CaF2 adhesives. For the CaF2 adhesives, an increased release of both ions was seen with a lowering pH and a lower DC was observed. Reinforcing of EA with CaF2 filler improves its mechanical properties. Further studies exploring the effect of diverse filler concentrations on different properties of the adhesive are warranted.