Amalgam (dentistry) Amalgam (dentistry) Dental amalgam is a liquid mercury and metal alloy mixture used in dentistry to fill cavities caused by tooth decay. Low-copper amalgam commonly consists of mercury (50%), silver (~22–32%), tin (~14%), copper (~8%) and other trace metals. Dental amalgams were first documented in a Tang Dynasty medical text written by Su Gong 苏恭 in 659, and appeared in Germany in 1528. In the 1800s, amalgam became the dental restorative material of choice due to its low cost, ease of application, strength, and durability. There are, according to Geir Bjørklund, indications that dental amalgam was used in the first
Real element formula_1, Every involution is strongly real. Furthermore, every element that is the product of two involutions is strongly real. Conversely, every strongly real element is the product of two involutions. If and formula_1 is real in formula_2 and formula_30 is odd, then formula_1 is strongly real in formula_2. The extended centralizer of an element formula_1 of a group formula_2 is defined as making the extended centralizer of an element formula_1 equal to the normalizer of the set The extended centralizer of an element of a group formula_2 is always a subgroup of formula_2. For involutions or non-real elements, centralizer and