Materials that have been finely ground or pulverized into very small, individual particles; the term typically refers to the polymer powders used to create acrylic (liquid/powder) systems; these substances are usually blends of finely ground methacrylate polymers. Acrylic powder was already in use in dentistry before it was ever applied to nails. Nail technicians began experimenting with these powders, but those who tried the dental powder-and-liquid combination often found the granules were too coarse; the resulting nails were too dense and yellowed easily. Some of the first acrylic formulas developed for nails contained MMA, which in 1978 the FDA deemed unsafe for use in nail products.