The evaluation of dental adhesives augmented with magnetic nanoparticles

An important challenge in today's dentistry is to create sturdy and aesthetic restorations. Dental research aims to create restorations with long-term durability and optical properties similar to healthy natural teeth. Recent works have shown that the magnetic handling of a dental adhesive doped with magnetic nanoparticles (MNPs) improves the adhesion between the composite and the dentin. This study presents the preparation of dental adhesives loaded with iron oxide (Fe3O4) NPs incorporated in SiO2 shells, and their applications in the creation of dental veneers. Extracted incisors were prepared for veneering and divided in two groups: Group A was bonded with normal adhesive and Group B was bonded with the augmented adhesive, in the presence of a permanent magnet. The samples were analyzed using stereomicroscopy, optical coherence tomography (OCT), and scanning electron microscopy (SEM), the latter combined with energy dispersive analysis of X-rays (EDAX). All techniques enabled the visualization of the veneer-adhesive and adhesive-dentin interfaces: (i) stereomicroscopy demonstrated that the adhesive layer was thinner for Group B and revealed conglomerates of MNPs in the adhesive layer; (ii) OCT enabled a visualization of the marginal closure, as well as of defects in the two interfaces; (iii) SEM provided a high-resolution image of the adhesive layer, whereas EDAX furnished an elemental analysis of the augmented adhesive. In conclusion, under the action of an external magnetic field, MNPs can penetrate deeper into the demineralized structure of the tooth, reducing the thickness of the adhesive layer and, thereby, decreasing the probability of microleakage.