Influence of graphene oxide filler content on the dentin bond integrity, degree of conversion and bond strength of experimental adhesive. A SEM, micro-Raman, FTIR and microtensile study

Abstract

The study aimed to evaluate the effect of graphene oxide (GO) nano-filler content in experimental dental adhesive on its degree of conversion (DC), microtensile bond strength (μTBS) and structural reliability, using Fourier transform infrared spectroscopy (FTIR), Micro-Raman spectroscopy and Scanning electron microscopy (SEM). A resin adhesive was fabricated (control adhesive - CA) and fabricated GO nano-particles were added at 0.5% and 2.0% (m/m) to produce adhesives GOA1 and GOA2 respectively. One hundred and two teeth (specimens) were prepared for dentin exposure and conditioned with 36% phosphoric acid. Specimens in each group (n = 34) were treated with formulated adhesives (CA, GOA1 & GOA2) and photo-polymerized for 20 s followed by composite build up. Sixty specimens were used for μTBS testing in the adhesive groups (CA, GOA1 & GOA2), with half exposed to thermocycling (TC) whereas the remaining half (n = 10) stored in distilled water. Seven specimens each were assessed using SEM and Micro-Raman spectroscopy, in each adhesive group (n = 7). DC for the adhesives was assessed using FTIR. The means of μTBS and DC were analyzed using ANOVA and post hoc Tukey multiple comparisons test. GO nano-filler content showed significant influence on the adhesive μTBS in comparison to controls (p < 0.01). Ageing (TC) revealed significant reduction in the μTBS, except in GOA2 specimens, which showed comparable outcomes among TC and non-TC specimens (p > 0.05). DC was significantly higher in control adhesive [46.8 (3.6)%] compared to GOA2 [37.7 (4.2)%] specimens, however DC was comparable among GOA1 [42.3 (2.9)%] and GOA2 [37.7 (4.2)%] specimens (p > 0.05) respectively. GO exhibited interaction within adhesive and tooth dentin comparable to control adhesive. Increasing GO content showed increase in μTBS of adhesive to dentin, but a decrease in degree of conversion. Under ideal conditions, experimental adhesive with 2% GO content showed acceptable bond strength and DC; and should be further assessed under dynamic conditions to recommend clinical use.

Influence of Different Conditioning Treatments on the Bond Integrity of Root Dentin to rGO Infiltrated Dentin Adhesive. SEM, EDX, FTIR and MicroRaman Study

“…DC of the two adhesive groups was also evaluated in our study, and although the results demonstrated comparable DC for both adhesive groups, still, higher DC values for EA-rGO-0% adhesive were seen compared with rGO-5% adhesive. Earlier, Bin-Shuwaish et al also reported an inverse positive linear relationship between increasing GO content and DC [ 32 ], and our results agree with their findings. Aside from rGO, researchers have also previously incorporated various other inorganic fillers like hydroxyapatite and silica in the adhesive and reported a similar trend (DC decreases linearly with the increasing filler content) [ 27 , 47 ].…”

“…The rGO nanoparticles, when observed on the SEM, revealed flake-shaped morphology, and this finding is consistent with several previous studies [ 25 , 32 ]. In general, the reduction process to yield GO nanoparticles produces flake-shaped sharp-edged sheets due to the presence of oxygen groups in the oxide sheets [ 33 ].…”

Dentin Bond Integrity of Hydroxyapatite Containing Resin Adhesive Enhanced with Graphene Oxide Nano-Particles—An SEM, EDX, Micro-Raman, and Microtensile Bond Strength Study

“…This loss of bond leads to the formation of nano-gaps resulting in bond failure and development of secondary caries [ 6 ]. To overcome failure of adhesion over time, addition of inorganic fillers in adhesives is promoted to improve dentin interaction of adhesive resins and possibly minimize dentin-adhesive degradation [ 7 ]. Previous studies have shown that addition of fillers in adhesives can reduce water sorption and solubility [ 8 ], in addition to enhancing its mechanical properties [ 9 ].…”

Evaluation of Synergic Potential of rGO/SiO2 as Hybrid Filler for BisGMA/TEGDMA Dental Composites

“…The polymer/graphene based nanocomposite has been an interesting research area for many years and various polymers have been intermingled with graphene [ 15 , 16 , 17 , 18 , 19 ]. The incorporation of graphene has greatly improved the mechanical properties of the polymers.…”