Dental amalgam controversy of mercury released from amalgam restorations, especially during placement and removal, has not been shown to cause any other adverse health effects." The paper goes on to say that there have been "no controlled studies published that show adverse systemic effects" from amalgam restorations and there is no evidence that removing amalgam restorations relieves any general symptoms. More recently, FDI has published a resolution confirming that their position on the safety and effectiveness of amalgam has not changed despite the phasing-down in some countries In the United States, numerous respected professional and non-profit organizations consider amalgam use to be safe
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