Dentifrices containing amorphous silica

A dental cream composition compatible with the surface of an unlined aluminum container and contained in said container, comprising a dental vehicle and dispersed therein about 10-35% by weight of a polishing agent consisting essentially of synthetic precipitated silica essentially free of alumina which silica has a wet cake moisture content of less than about 75%, an oil absorption of less than about 125 cc/gm, a pack density of more than about 12 pounds/cubic foot, a valley abrasion of more than about 5.0 mg wire loss, a surface area of less than about 120m.sup.2 /gm, an aggregate particle size of about 2 to 20 microns and an essentially amorphous x-ray structure, a compound which provides fluorine in amount of about 0.01 to 1% by weight and a water-soluble calcium salt selected from the group consisting of chloride, bromide, iodide, acetate and nitrate in amount to provide at least about 0.01% to about 0.3% by weight of calcium ion in water, said dental cream otherwise being substantially calcium free and causing formation of gas pockets on an aluminum container surface, air on wall and substantially etching and swelling of the container when the amount of the calcium salt is such that less than about 0.01% calcium ion is solubilized in water and compatibility with said aluminum container being substantially lost at substantially higher amount of calcium than about 0.3% by weight of calcium ion in water.