Incorporation of epigallocatechin-3-gallate absorbed onto hydroxyapatite nanoparticles in dental adhesive: Impact on resin dentin-bonding, chemical, and mechanical properties

Abstract

To evaluate the resin-dentin bond strength, chemical and mechanical properties of experimental etch-and-rinse (E&R) and self-etch (SE) adhesives doped with epigallocatechin-3-gallate (EGCG) adsorbed on hydroxyapatite (HAp) nanoparticles. The groups were divided according to the concentration of HAp/EGCG (epigallocatechin-3-gallate adsorbed on hydroxyapatite nanoparticles) (% wt) and bonding strategies (E&R or SE): 1) Control SE (0 %), 2) Control E&R (0 %), 3) SE-HAp/EGCG 1 %, 4) E&R-HAp/EGCG 1 %, 5) SE-HAp/EGCG 5 % and 6) E&R-HAp/EGCG 5 %. Nanoparticles were incorporated into experimental adhesives. Bar-shaped specimens (n = 6) were prepared to assess flexural strength (FS) and elastic modulus (EM), and the degree of conversion (DC, n = 5) was assessed by Fourier transform infrared spectroscopy. Sixty human third molars were sectioned and restored for microtensile bond strength testing (μTBS, n = 10) at 24 h and 6 months in distilled water. Data were analyzed by three-way ANOVA (μTBS) or two-way ANOVA (DC, FS, EM) and Tukey's post-test (α = 0.05). FS and EM increased significantly in the 5 % SE-HAp/EGCG group compared to the control group (p < 0.05). EM decreased significantly in the 1 % SE-HAp/EGCG group, while FS increased in the E&R mode. The addition of HAp/EGCG increased the DC adhesives. For μTBS at 24 h, the E&R- HAp/EGCG 1 %–5 % groups displayed the highest values. After 6 months, HAp/EGCG 1 % (E&R and SE) maintained bond strength (p < 0.001), while the SE control group exhibited a significant decrease in μTBS values. Adhesive failure was predominant in all groups. Incorporating 1 % HAp/EGCG into E&R adhesives enhanced bonding performance, monomer conversion, and material strength, while the 5 % concentration compromised dentin bonding and physicochemical properties.