A systematic study and effect of PLA/Al2O3 nanoscaffolds as dental resins: mechanochemical properties.

One of the major and important challenges in dental composite resin and restoration is the mechanical performance and property of materials. Nanotechnology can produce nanoscale materials that are used in dentistry to help stabilize and strengthen the dentistry. In this work, we study the synthesis and characterization of PLA/Al2O3 nanoscaffold in different conditions such as concentration, temperature, pH, microwave power and irradiation time. PLA/Al2O3 nanoscaffolds were prepared by a micelle-assisted hydrothermal method. Durability, stability and biodegradable nature of nanopolymers have created the much-applied potential for using this structures in many fields such as dental resin composites. Products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transition electron microscopy (TEM), Fourier transformed infrared spectrum (FT-IR), Dynamic light scattering (DLS) and atomic force microscopy (AFM). The synthesis factors were designed by Taguchi technique to control the process systematically. It was found that the intermolecular crosslinks between PLA and Al2O3 nanoparticles cause significant improves in the mechanical properties of PLA/Al2O3 nanoscaffold as dental nanocomposites. The flexural strength (88.0 MPa), modulus (7.5 GPa) and compressive strength (157.2 MPa) were calculated for PLA/Al2O3 nanoscaffolds loaded in Heliomolar Flow composite resins at 80 ppm (wt) concentration.

Antimicrobial activity of Bacillus sp. strain FAS1 isolated from soil.

During screening for antibiotic producing microorganisms from environmental soil samples, the supernatant of a bacterial isolate was found to have antibacterial and antifungal activity on the standard indicator species. The standard cylinder-plate method was used to determine the inhibitory effect of the crude supernatant of each isolate on 6 bacterial and 3 fungal standard strains by measuring the diameter of inhibition zone. The highest inhibition zone on Aspergillus niger belonged to culture broth of isolate FAS1 by 25 mm, and this isolate was the most efficient microorganism to inhibit standard bacterial and fungal species. Based on morphological and biochemical properties as well as 16S rDNA gene analysis, the selected isolate (isolate FAS(1)) belonged to Bacillus genus. Investigation on the ability of different culture media for antibiotic production led to select Luria-Bertani media for further studies. Treatment of the culture broth of the isolate FAS(1) using typical protease didn't decrease the antimicrobial activity of the supernatant. After extracting of culture broth of the selected isolate by ethyl acetate as an organic solvent, the inhibitory effect was mainly increased. More investigation was done by bioautography method where the ethyl acetate fraction of the broth culture was separated on TLC by chloroform:methanol, 60:40 as mobile phase and R(f) were calculated for inhibition spots.