RETRACTED: Synthesis and characterization of graphene-modified experimental adhesive system for bonding two-piece zirconia abutments: Electron microscopy and Raman spectroscopic analysis

Abstract This study aimed to synthesize and characterize graphene oxide (GO) nanoparticles and study the spectral, microbiological, and mechanical analysis of GO in two types of resin adhesives bonded to two-piece zirconia abutments. GO was synthesized and the nanoparticles were characterized using a scanning electron microscope (SEM). Four experimental groups were formed based on weight percentage (0.25 wt% and 0.5 wt%) of GO added in conventional chemically activated resin cement and the other two groups with dual-cure cement. Two non-modified adhesive groups served as the control groups. Sixty sets of zirconia abutments cemented to screwed titanium bases of implants analogs were divided into 6 groups. Spectral analysis and degree of conversion (DC) were performed using micro-Raman and Fourier-transformed infrared spectroscopy (FTIR). Bacterial viability was studied using the 3-(4,5-dimethylthiazole-2-yl)-2,5-diphenyltetrazoli-umbromide (MTT) assay over the implant. On SEM analysis, GO (thickness of 1–2 nm thick flakes) nanoparticles were uniformly dispersed throughout the adhesive matrix. Raman and FTIR analysis confirmed the presence of D and G bands. Implant specimens treated with 0.5 wt% GO-modified dual-cure adhesive demonstrated the lowest mean score of DC (38.75 ± 6.37). After 1 day and 30 days of incubation with dental adhesives, 0.5 wt% GO-modified chemically activated adhesive specimens showed high antibacterial activity; only 23% and 30% of Streptococcus mutans were able to survive after treating with 0.5 wt% GO-modified chemically activated adhesive, respectively. In conclusion, incorporation of 0.5 wt% of GO in both chemically activated and dual-cure adhesive produced superior antimicrobial and physical characteristics for bonding two-piece zirconia abutments to screwed titanium bases.