Influence of Halloysite Nanotubes and Alkyltrimethylammonium Bromide Into Adhesive Resin

Objectives: The aim of this study was to develop and to characterize an experimental adhesive resin with halloysite nanotubes and a quaternary ammonium compound (alkyltrimethylammonium bromide).
Methods: The filler was formulated by mixing halloysite nanotubes with the quaternary ammonium compound (ratio 1:1) and absolute ethanol by a magnetic stirrer until the solvent vaporization. The experimental adhesive resin was formulated mixing 66.6 wt.% bisphenol A glycol dimethacrylate (BisGMA), 33.3 wt.% 2-hydroxyethyl methacrylate (HEMA) and photoinitiator system. The filler was incorporated in concentration of 5 wt.% in to the adhesive (G5) and a group without filler addition was used as control (G0). The filler was analyzed by scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS) and transmission electron microscopy (TEM). The adhesives were evaluated for microtensile bond strength (n=20), softening in solvent (n=5), antibacterial activity (n=3) through surface biofilm formation, degree of conversion (DC) in situ using bovine teeth (n=5) and in vitro (n=5) using resin samples and mineral deposition (n=3) by micro Raman spectroscopy. Data were analyzed by t test at 0.05 level of significance.
Results: There was no statistical difference on the microtensile bond strength, initial microhardness and softening in solvent test (p>0.05). The DC of the in vitro and in situ evaluation was 80.32 (± 3.25) and 85.20 (± 5.16), respectively, for G0 and 81.90 (± 3.44) and 87.35 (± 4.58), respectively, for G5, with no statistical difference in each test (p>0.05). G5 presented a reduction in bacterial growth compared to G0 (p<0.05) and showed mineral deposition on the adhesive interface after 30 days in simulated body fluid. SEM-EDS indicated the presence of the antibacterial agent and it was observed by TEM the incorporation in to the nanotubes.
Conclusions: It was concluded that the adhesive resin formulated with halloysite nanotubes and alkyltrimethylammonium bromide showed antibacterial activity and induced mineral deposition without changing the other tested properties.