Nanotechnology is a rapidly advancing field with significant potential. Nanoparticles (NPs) are very small in diameter, ranging from 0.1 to 100 nm , and silver nanoparticles (AgNPs) have unique antimicrobial, optical, and biological properties, along with high electrical conductivity. AgNPs are widely used in many fields, including medicine, food, and industry . Therefore, assessing the risks and safety of AgNPs is very important. In this review, we discuss the double-edged sword of AgNPs and clarify the different cellular responses as determined by their characteristics. Coating, size, and concentration are critical factors that affect cellular uptake and AgNP interactions. Different NP coatings affect the agglomeration and dissolution rate, which then affect cellular responses, revealing that uncoated AgNPs are more toxic than those that are coated. Also, smaller NPs have a higher surface area, ionization rate, and cytotoxic effects. The cellular uptake of AgNPs occurs in a concentration-dependent manner, which also affects cellular responses. Taken together, we conclude that specifying AgNP characteristics is vital to understanding the cellular responses that they might induce.
After orthodontic treatment has been completed, we consider fluorescent imaging to be one of the most effective solutions for secure removal of colorless residual adhesives from tooth surfaces using cutting instruments. Nanoscale Y2O3:Eu3+ particles were synthesized using the homogeneous precipitation method with two different starting concentrations of urea aqueous solutions, followed by firing at 1000°C. These particles exhibited narrow size distribution (approx. 200-300 nm) and sharp crystallinity regardless of the urea concentration. Moreover, their photoluminescence peak corresponded well with the typical 4f-4f transitions of Eu3+. The Y2O3:Eu3+ particles were almost uniformly dispersed and retained in the monomer blends and polymerized bulk bodies. Photoluminescence measurement is a valid detection method and can be useful for future studies on dispersion control. We conclude that the crystalline Y2O3:Eu3+ particles could be applicable for further development of fluorescent orthodontic adhesives.
Rotary cutting instruments for dental restoration, such as tungsten carbide burs and diamond points, are frequently used in the oral cavity; however, minute tungsten and diamond fragments may influence biological safety. To compare 3-dimensional culture methods, pig-derived type I collagen gel and glass fibers not influenced by protein contained in collagen were exposed to debris from burs and points. The embryotoxicity of chemical substances influencing the normal birth of humans is an important index. The differentiation of ES-D3 cells, an important index, was also compared. The variation in cell differentiation on glass fibers was slightly smaller than that on collagen gel, demonstrating a slightly stronger influence. In addition, the influence of the tungsten carbide bur was slightly weaker than that of the diamond point. The influence of LDH on cells was similar. The plating of the diamond point was considered to have been eluted, thereby increasing the influence. Glass fibers may be used to construct a 3-dimensional culture environment to investigate embryotoxicity using ES-D3 cells in a long-term environmental study, which is difficult with systems using collagen gel, i.e., it may be useful for long-term measurement of the embryotoxicity of environmental chemical substances. The test method using glass fibers may be applicable to biological safety in addition to embryotoxicity.
Although nano-sized titanium dioxide is used in many quasi-drugs, its biological safety remains unclear. To examine the effects of nano-sized titanium dioxide on cell viability, we examined it, cell membrane damage, and oxidative stress by three-dimensional culture with tilapia scale collagen. The cell viability was significantly reduced with a stock solution, as demonstrated by the MTT method. In addition, a large amount of the oxidative stress marker 8-OHdG was observed. All of the endpoints gradually became closer to those of the control group at a higher dilution rate of the test solution. These results were consistent with those obtained from the conventional three-dimensional culture with swine collagen, demonstrating the feasibility of the three-dimensional culture with tilapia scale collagen.