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 formsâ white phosphorus and red phosphorus âbut due to its high reactivity, phosphorus is never found as a free element on Earth.Instead phosphorus-containing minerals are almost always present in their maximally oxidised state, as inorganic phosphate rocks.he glow of phosphorus itself originates from oxidation of the white (but not red) phosphorusâ a process now termed chemiluminescence. Together with nitrogen, arsenic, and antimony, phosphorus is classified as a pnictogen. Phosphorus is essential for life.