The purpose of this laboratory study was to formulate and characterize the graphene oxide-poly(methyl methacrylate) resin composite with an intended use as bone cement. Graphene oxide was fabricated through ultrasonication route. The autopolymerization resin (Eco Cryl Cold, Protechno, Vilamalla Girona, Spain) was used to prepare the specimens of required dimensions for different testing parameters. The control group (C-group) was prepared as such. However, for GO1-group, 0.024 wt/wt.-% of graphene oxide was incorporated in a resin matrix and GO2-group was a composite with 0.048 wt/wt.-% of graphene oxide in a resin matrix. TEM examination of graphene oxide sheets demonstrated them in the range of ∼500 nm to ∼2 µm. The mechanical properties were characterized using three-point bending and wear resistance, while material properties were assessed through transmission electron microscope, scanning electron microscopy, Fourier-transform infrared spectroscopy, Raman spectroscopy, X-ray diffraction, differential scanning calorimetry and thermo-gravimetric analysis. The results suggest that 0.024 wt/wt.-% and 0.048 wt/wt.-% of loading of GO have no effect on the physiochemical characteristics. However, thermal characteristics might slightly be improved. According to the analysis of variance results (p < 0.05, n = 5), wear resistance and bending strength of both GO1 and GO2 groups significantly improved compared to C-group. The bending strength of GO2 improved to 87.0 ± 7.2 MPa from 65.9 ± 11.5 MPa of C-group. Scanning electron microscopy examination of the fractured surface demonstrated granule like structure where the graphene oxide sheets might be covered inside PMMA. The use of GO-PMMA composites favorably enhances the mechanical properties of bone cement.

The purpose of this laboratory study was to formulate graphene oxide (GO) nano-sheets and characterize composites of homogenously dispersed GO sheets in poly(methyl methacrylate) (PMMA) acrylic resin of two groups, i.e., with 0.025 wt/wt.% GO (GO1-group) and 0.05 wt/wt.% GO (GO2-group). A large array of surface, mechanical and dynamic mechanical properties, including creep, recovery, stress relaxation behaviour and temperature and frequency sweep of the formulated bone cements were further characterized. Analysis of variance test results (p = 0.05, n = 5) indicated that the nanohardness and elastic modulus of the experimental groups were not significantly different from those of the control. Micro-computed tomography results showed high porosity in the experimental groups. The compressive strength significantly increased both in GO1- and GO2-group under dry and wet storage conditions. The dynamic mechanical properties suggest a desirable role of GO in polymerization with PMMA. The produced GO-PMMA composites exhibited the expected characteristics, so their use in developing low-loading bone cement composites appears to be promising.

The objective of this study was targeted to synthesize and characterize a carbon nanotubes (CNTs) incorporated poly(methyl methacrylate) (PMMA)-based denture polymer. Two experimental denture base polymers were fabricated either by incorporating single-walled CNTs (SWCNTs) (SW-group) or multi-walled CNTs (MWCNTs) (MW-group). In both groups, 0.5 wt% of the CNTs were incorporated into MMA monomer. Using a commercially available heat-cured PMMA (Interacryl Hot, Interdent, Opekarniska, Slovenia), a polymer-to-monomer ratio of 3:1 was used to fabricate the specimens (14 × 14 × 3 mm3 in dimensions) of the control group (without CNTs) (C-group) and the experimental groups (either SWCNT–PMMA or MWCNT–PMMA) ( n = 30, N = 90). Physical, mechanical, thermal, and rheological attributes of the tested materials were assessed. The data were statistically analyzed using SPSS version 21.0 (SPSS®, Chicago, IL, USA) and results were explored with one-way ANOVA. Incorporation of CNTs changed the surface morphology and topography of the PMMA specimens. No thermal changes were observed among C-, SW-, and MW-groups. Conversely, the hardness, elastic modulus and wear resistance were improved in both SW-group and MW-group. Additionally, the dynamic mechanical analyzer showed improvement in storage modulus in SW-group, affirming the load transfer capability of SW–PMMA composite. The CNT–PMMA composite might favorably be used as a potential denture base polymer.

This study analyzed the effect of grit blasting pressures on resin cement to zirconia (ZrO2) adhesion using enclosed mold shear bond test (EM-SBS). ZrO2 blanks were pre-treated with Rocatec ™ Soft as follows: group 1: control, group 2: specimens treated at 80 kPa, group 3: at 180 kPa, group 4: at 280 kPa, and group 5: at 380 kPa. Monobond ® N and Multilink ® Speed were used as the silane and resin cement, respectively. Next, the blanks were assigned into three subgroups (n=8, N=108) according to storage conditions. A non-linear relation was observed between EM-SBS and contact angle versus grit blasting pressure (r=−0.542, p=0.01). According to ANOVA (p<0.05), the EM-SBS values with both 180 kPa (17.4±6.7 MPa) and 280 kPa (19.4±4.8 MPa) were statistically higher after 12,000 thermo-cycles. Relatively equal thermo-cycled bond strength might also be achieved with intermediate (180 kPa) grit blasting pressure instead of the recommended 280 kPa.

No abstract

Articular cartilage is a tissue specifically adapted to a specific niche with a low oxygen tension (hypoxia), and the presence of such conditions is a key factor in regulating growth and survival of chondrocytes. Zinc deficiency has been linked to cartilage-related disease, and presence of Zinc is known to provide antibacterial benefits, which makes its inclusion attractive in an in vitro system to reduce infection. Inclusion of 1% zinc oxide nanoparticles (ZnONP) in poly octanediol citrate (POC) polymer cultured in hypoxia has not been well determined. In this study we investigated the effects of ZnONP on chondrocyte proliferation and matrix synthesis cultured under normoxia (21% O2 ) and hypoxia (5% O2 ). We report an upregulation of chondrocyte proliferation and sulfated glycosaminoglycan (S-GAG) in hypoxic culture. Results demonstrate a synergistic effect of oxygen concentration and 1% ZnONP in up-regulation of anabolic gene expression (Type II collagen and aggrecan), and a down regulation of catabolic (MMP-13) gene expression. Furthermore, production of transcription factor hypoxia-inducible factor 1A (HIF-1A) in response to hypoxic condition to regulate chondrocyte survival under hypoxia is not affected by the presence of 1% ZnONP. Presence of 1% ZnONP appears to act to preserve homeostasis of cartilage in its hypoxic environment.

No abstract

Graphene is an excellent filler for the development of reinforced composites. This study evaluated bone cement composites of graphene oxide (GO) and poly(methyl methacrylate) (PMMA) based on the proliferation of human bone marrow mesenchymal stem cells (hBMSCs), and the anabolic and catabolic effects of the incorporation of GO on osteoblast cells at a genetic level. Surface wettability and roughness were also evaluated at different GO concentrations (GO1: 0.024 wt% and GO2: 0.048 wt%) in the polymer matrix. Fabricated specimens were tested to (a) observe cell proliferation and (b) identify the effectiveness of GO on the expression of bone morphogenic proteins. Early osteogenesis was observed based on the activity of alkaline phosphatase and the genetic expression of the run-related transcription factor 2. Moreover, bone strengthening was determined by examining the collagen type 1 alpha–1 gene. The surface roughness of the substrate material increased following the addition of GO fillers to the resin matrix. It was found that over a period of ten days, the proliferation of hBMSCs on GO2 was significantly higher compared to the control and GO1. Additionally, quantitative colorimetric mineralization of the extracellular matrix revealed greater calcium phosphate deposition by osteoblasts in GO2. Furthermore, alizarin red staining analysis at day 14 identified the presence of mineralization in the form of dark pigmentation in the central region of GO2. The modified GO–PMMA composite seems to be promising as a bone cement type for the enhancement of the biological activity of bone tissue.