In general, stainless steel crowns are used for children's teeth because they don't require multiple dental visits to put in place and so are more cost- effective than custom-made crowns and prophylactic dental care needed to protect a tooth without a crown.
Phosphorus comes from many places. You might think that the biggest sources of phosphorus are the obvious onesâsewage treatment plants, chemical factories, and the like. But in fact, identifiable sources such as these contribute less than 20% of the phosphorus in the river.
Phosphorus is a chemical element with symbol P and atomic number 15. As an element, phosphorus exists in two major formsâwhite phosphorus and red phosphorusâbut because it is highly reactive, phosphorus is never found as a free element on Earth. At 0.099%, phosphorus is the most abundant pnictogen in the Earth's crust. With few exceptions, minerals containing phosphorus are in the maximally oxidized state as inorganic phosphate rocks. The first form of elemental phosphorus to be produced ...