This is known as a protein fallout reaction. A simple but elegant machine called a light densitometer is then used to measure the opacity of each serum-chemical mixture, and the chemical is then judged according to protocols originally developed by Dr. Hal Huggins and refined over decades of testing. For the dentist’s convenience the classifications “Highly Reactive,” “Moderately Reactive,” and “Least Reactive,” are used to aid in understanding the results. Each product on the test is then rated by the highest reactivity level among its component chemicals. This assures that only the products in which all components give the lowest reaction levels are termed “Least Reactive.”