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This laboratory investigation aimed to synthesize and characterize micron-sized Gum Arabic (GA) powder and incorporate it in commercially available GIC luting formulation for enhanced physical and mechanical properties of GIC composite. Oxidation of GA was performed and GA-reinforced GIC in 0.5, 1.0, 2.0, 4.0 & 8.0 wt.% formulations were prepared in disc-shaped using two commercially available GIC luting materials (Medicem and Ketac Cem Radiopaque). While the control groups of both materials were prepared as such. The effect of reinforcement was evaluated in terms of nano hardness, elastic modulus, diametral tensile strength (DTS), compressive strength (CS), water solubility and sorption. Two-way ANOVA and post hoc tests were used to analyze data for statistical significance (p < 0.05). FTIR spectrum confirmed the formation of acid groups in the backbone of polysaccharide chain of GA while XRD peaks confirmed that crystallinity of oxidized GA. The experimental group with 0.5 wt.% GA in GIC enhanced the nano hardness while 0.5 wt.% and 1.0 wt.% GA in GIC increased the elastic modulus compared to the control. The CS of 0.5 wt.% GA in GIC and DTS of 0.5 wt.% and 1.0 wt.% GA in GIC demonstrated elevation. In contrast, the water solubility and sorption of all the experimental groups increased compared to the control groups. The incorporation of lower weight ratios of oxidized GA powder in GIC formulation helps in enhancing the mechanical properties with a slight increase in water solubility and sorption parameters. The addition of micron-sized oxidized GA in GIC formulation is promising and needs further research for improved performance of GIC luting composition.

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This study aimed to determine the reinforcing effect of two weight ratios of Gum Arabic (GA) natural biopolymer, i.e., 0.5% and 1.0% in the powdered composition of glass ionomer luting cement. GA powder was oxidized and GA-reinforced GIC in 0.5 and 1.0 wt.% formulations were prepared in rectangular bars using two commercially available GIC luting materials (Medicem and Ketac Cem Radiopaque). The control groups of both materials were prepared as such. The effect of reinforcement was evaluated in terms of microhardness, flexural strength (FS), fracture toughness (FT), and tensile strength (TS). The internal porosity and water contact angle formation on the study samples were also evaluated. Film thickness was measured to gauge the effect of micron-sized GA powder in GA–GIC composite. Paired sample t-tests were conducted to analyze data for statistical significance (p < 0.05). The experimental groups of both materials containing 0.5 wt.% GA–GIC significantly improved FS, FT, and TS compared to their respective control groups. However, the microhardness significantly decreased in experimental groups of both cements compared to their respective control groups. The addition of GA powder did not cause a significant increase in film thickness and the water contact angle of both 0.5 and 1.0 wt.% GA–GIC formulations were less than 90o. Interestingly, the internal porosity of 0.5 wt.% GA–GIC formulations in both materials were observed less compared to their respective control groups. The significantly higher mechanical properties and low porosity in 0.5 wt.% GA–GIC formulations compared to their respective control group indicate that reinforcing GA powder with 0.5 wt.% in GIC might be promising in enhancing the mechanical properties of GIC luting materials.

Objective: This study was aimed at including 2.5 wt.% of carbon nanoparticles (CNPs) and graphene oxide NPs (GNPs) in a control adhesive (CA) and then investigate the effect of this inclusion on their mechanical properties and its adhesion to root dentin. Materials and methods: Scanning electron microscopy and energy dispersive X-ray (SEM-EDX) mapping were conducted to investigate the structural features and elemental distribution of CNPs and GNPs, respectively. These NPs were further characterized by Raman spectroscopy. The adhesives were characterized by evaluating their push-out bond strength (PBS), rheological properties, degree of conversion (DC) investigation, and failure type analysis. Results: The SEM micrographs revealed that the CNPs were irregular and hexagonal, whereas the GNPs were flake-shaped. EDX analysis showed that carbon (C), oxygen (O), and zirconia (Zr) were found in the CNPs, while the GNPs were composed of C and O. The Raman spectra for CNPs and GNPs revealed their characteristic bands (CNPs-D band: 1334 cm−1, GNPs-D band: 1341 cm−1, CNPs-G band: 1650 cm−1, and GNPs-G band: 1607 cm−1). The testing verified that the highest bond strength to root dentin were detected for GNP-reinforced adhesive (33.20 ± 3.55 MPa), trailed closely by CNP-reinforced adhesive (30.48 ± 3.10 MPa), while, the CA displayed lowest values (25.11 ± 3.60 MPa). The inter-group comparisons of the NP-reinforced adhesives with the CA revealed statistically significant results ( p < 0.01). Failures of adhesive nature were most common in within the adhesives and root dentin. The rheological assessment results demonstrated a reduced viscosity for all the adhesives observed at advanced angular frequencies. All the adhesives verified suitable dentin interaction shown by hybrid layer and appropriate resin tag development. A reduced DC was perceived for both NP-reinforced adhesives, compared to the CA. Conclusion: The present study’s findings have demonstrated that 2.5% GNP adhesive revealed the highest, suitable root dentin interaction, and acceptable rheological properties. Nevertheless, a reduced DC was observed (matched with the CA). Prospective studies probing the influence of diverse concentrations of filler NPs on the adhesive’s mechanical properties to root dentin are recommended.

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This laboratory investigation was designed to test the influence of a novel bleaching formulation based on phthalimidoperoxycaproic acid (PAP) with additives on the surface and mechanical properties of nano- and micro-hybrid restorative composites. Twenty-four bar-shaped and twelve disk-shaped samples from each restorative composite were prepared. The samples from each restorative composite were randomly divided into two groups according to the treatment, i.e., experimental and control. The treated groups went through the bleaching process: by Opalescence Regular or novel PAP+-containing gel (HiSmile™). The treated group underwent a bleaching process for seven consecutive days (a 10-min session of bleaching application every day) before the properties were tested. A paired sample t-test was performed to compare the results between the experimental and the control groups. The level of significance was set at 0.05. The surface roughness of the nanohybrid composite using Opalescence Regular (p < 0.05) was significant. Additionally, a significant difference in nanohardness and elastic modulus between the experimental and the control groups of the microhybrid composite using Opalescence Regular was observed: p = 0.041 and p = 0.023, respectively. While a marked difference in flexural strength was observed in the experimental and control groups using Opalescence Regular, Hismile™ bleaching gel caused a diminutive and insignificant reduction in tested properties (p > 0.05). It was found that Opalescence Regular bleaching gel affects the surface and bulk properties of restorative composite materials, whereas the novel PAP+ formulation has no deleterious effect on either nano- or micro-hybrid restorative composites.

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