The only way to eliminate calculus build up is by brushing and flossing frequently. It takes pyhsical removal of the placque before it calcified into the hard tarter, or calculus. Some people will have more tendency to build up calculus because of the chemical composition of their saliva.
Brasso is a metal polish designed to remove tarnish from brass, copper, chrome and stainless steel. It is available either directly as a liquid or as an impregnated wadding pad.
Brass is made of copper and zinc. Bronze is made of copper and tin. These are nickel-free and beautiful all by themselves. Bare metals or oxidized metals are nickel-free, and beautiful to wear. Modern-day brass is not produced with lead, although it never hurts to ask.