Effect of stem cells combined with a polymer/ceramic membrane on osteoporotic bone repair

Abstract Cell therapy associated with guided bone regeneration (GBR) can be used to treat bone defects under challenging conditions such as osteoporosis. This study aimed to evaluate the effect of mesenchymal stem cells (MSCs) in combination with a poly(vinylidene-trifluoroethylene)/barium titanate (PVDF-TrFE/BT) membrane on bone repair in osteoporotic rats. Osteoporosis was induced in female rats by bilateral removal of the ovaries (OVX) or sham surgery (SHAM), and the osteoporotic condition was characterized after 5 months by microtomographic and morphometric analyses. Calvarial defects were created in osteoporotic rats that immediately received the PVDF-TrFE/BT membrane. After 2 weeks, bone marrow-derived MSCs from healthy rats, characterized by the expression of surface markers using flow cytometry, or phosphate-buffered saline (PBS) (Control) were injected into the defects and bone formation was evaluated 4 weeks post-injection by microtomographic, morphometric, and histological analyses. A reduction in the amount of bone tissue in the femurs of OVX compared with SHAM rats confirmed the osteoporotic condition of the experimental model. More bone formation was observed when the defects were injected with MSCs compared to that with PBS. The modification that we are proposing in this study for the classical GBR approach where cells are locally injected after a membrane implantation may be a promising therapeutic strategy to increase bone formation under osteoporotic condition.

Model resin composites incorporating ZnO-NP: activity against S. mutans and physicochemical properties characterization

Abstract Although resin composites are widely used in the clinical practice, the development of recurrent caries at composite-tooth interface still remains as one of the principal shortcomings to be overcome in this field. Objectives To evaluate the activity against S. mutans biofilm of model resin composites incorporating different concentrations of ZnO-nanoparticles (ZnO-NP) and characterize their physicochemical properties. Materials and Methods Different concentrations of ZnO-NP (wt.%): E1=0, E2=0.5, E3=1, E4=2, E5=5 and E6=10 were incorporated into a model resin composite consisting of Bis-GMA-TEGDMA and barium borosilicate particles. The activity against S. mutans biofilm was evaluated by metabolic activity and lactic acid production. The following physicochemical properties were characterized: degree of conversion (DC%), flexural strength (FS), elastic modulus (EM), hardness (KHN), water sorption (Wsp), water solubility (Wsl) and translucency (TP). Results E3, E4, E5 and E6 decreased the biofilm metabolic activity and E5 and E6 decreased the lactic acid production (p<0.05). E6 presented the lowest DC% (p<0.05). No significant difference in FS and EM was found for all resin composites (p>0.05). E5 and E6 presented the lowest values of KHN (p<0.05). E6 presented a higher Wsp than E1 (p<0.05) and the highest Wsl (p<0.05). The translucency significantly decreased as the ZnO- NP concentration increased (p<0.05). Conclusions The incorporation of 2 - 5 wt.% of ZnO-NP could endow antibacterial activity to resin composites, without jeopardizing their physicochemical properties.

Evaluation of antibacterial properties of Barium Zirconate Titanate (BZT) nanoparticle

So far, the antibacterial activity of some organic and inorganic compounds has been studied. Barium zirconate titanate [Ba(Zr xTi1-x)O3] (x = 0.05) nanoparticle is an example of inorganic materials. In vitro studies have provided evidence for the antibacterial activity of this nanoparticle. In the current study, the nano-powder was synthesized by sol-gel method. X-ray diffraction showed that the powder was single-phase and had a perovskite structure at the calcination temperature of 1000 ºC. Antibacterial activity of the desired nanoparticle was assessed on two gram-positive (Staphylococcus aureus PTCC1431 and Micrococcus luteus PTCC1625) and two gram-negative (Escherichia coli HP101BA 7601c and clinically isolated Klebsiella pneumoniae) bacteria according to Radial Diffusion Assay (RDA). The results showed that the antibacterial activity of BZT nano-powder on both gram-positive and gram-negative bacteria was acceptable. The minimum inhibitory concentration of this nano-powder was determined. The results showed that MIC values for E. coli, K. pneumoniae, M. luteus and S. aureus were about 2.3 µg/mL, 7.3 µg/mL, 3 µg/mL and 12 µg/mL, respectively. Minimum bactericidal concentration (MBC) was also evaluated and showed that the growth of E. coli, K. pneumoniae, M. luteus and S. aureus could be decreased at 2.3, 14, 3 and 18 µg/mL of BZT. Average log reduction in viable bacteria count in time-kill assay ranged between 6 Log10 cfu/mL to zero after 24 h of incubation with BZT nanoparticle.

Effect of filler particles on surface roughness of experimental composite series

OBJECTIVE: The purpose of this study was to evaluate the effect of different filler sizes and shapes on the surface roughness of experimental resin-composite series. MATERIAL AND METHODS: Thirty-three disc-shaped specimens of the series (Spherical-RZD 102, 105, 106, 107, 114 and Irregular-RZD 103, 108, 109, 110, 111, 112) were prepared in a split Teflon mold and irradiated with an halogen light-curing unit (450 mW/cm² for 40 s) at both top and bottom surfaces. The specimens were stored for 3 months in distilled water. The surface roughness values in form of surface finish-vertical parameter (Ra), maximum roughness depth (Rmax) and horizontal roughness parameter (Sm) were recorded using a contact profilometer. The data were analyzed by one-way ANOVA and the means were compared by Scheffé post-hoc test (a=0.05). RESULTS: The lowest surface roughness (Ra) was observed in S-100 (0.079±0.013), while the roughest surface was noted in I-450/700/1000 (0.125±0.011) and I-450/1000 (0.124±0.004). The spherical-shape series showed the smoothest surface finish compared to the irregular-shape ones with higher significant difference (p>0.05). The vertical surface roughness parameter (Ra) values increased as the filler size increased yielding a linear relation (r²=0.82). On the contrary, the horizontal parameter (Sm) was not significantly affected by the filler size (r²=0.24) as well as the filler shape. CONCLUSIONS: Filler particle's size and shape have a great effect on the surface roughness parameters of these composite series.

Morphological analysis of glass, carbon and glass/carbon fiber posts and bonding to self or dual-cured resin luting agents

OBJECTIVE: The aim of this study was to evaluate the morphology of glass (GF), carbon (CF) and glass/carbon (G/CF) fiber posts and their bond strength to self or dual-cured resin luting agents. MATERIAL AND METHODS: Morphological analysis of each post type was conducted under scanning electron microscopy (SEM). Bond strength was evaluated by microtensile test after bisecting the posts and re-bonding the two halves with the luting agents. Data were subjected to two-way ANOVA and Tukey's test (α=0.05). Failure modes were evaluated under optical microscopy and SEM. RESULTS: GF presented wider fibers and higher amount of matrix than CF, and G/CF presented carbon fibers surrounded by glass fibers, and both involved by matrix. For CF and GF, the dual-cured material presented significantly higher (p<0.05) bond strength than the self-cured agent. For the dual agent, CF presented similar bond strength to GF (p>0.05), but higher than that of G/CF (p<0.05). For the self-cured agent, no significant differences (p>0.05) were detected, irrespective of the post type. For GF and G/CF, all failures were considered mixed, while a predominance of adhesive failures was detected for CF. CONCLUSION: The bonding between fiber posts and luting agents was affected by the type of fibers and polymerization mode of the cement. When no surface treatment of the post is performed, the bonding between glass fiber post and dual-cured agent seems to be more reliable.