We are all aware that organisms which produce disease vary greatly in the amount and severity of their virulence. Because teeth are relatively small, it is also generally believed that when a tooth has a properly treated root canal filling, it is impossible for an infection there from to overwhelm the patient. Furthermore, many express the opinion that the organisms which cause dental infections are low in virulence and the occurrence of any systemic involvement is unlikely or, at best, of minor significance.

One of the first of numerous experiments by Dr.Price was to withdraw the moisture content of an extracted tooth in a drying chamber. Measuring the amount of dehydration showed that roughly five percent of the volume of every root filled tooth is a fluid which can quite readily become a culture medium that can become easily saturated with abundant bacteria.

In another experiment, a root filled tooth was taken from a patient suffering acute endocarditis. The tooth was crushed and the particles washed.The settled wash liquid was then injected into a rabbit. The weight of the organisms injected was determined by counting the number present in the dilution; the actual amount the rabbit received was only a millionth part of a gram. Still, the rabbit became seriously ill with endocarditis. With such a small amount of bacteria involved, the question arose as to whether something more than the bacteria could be the causative agent.

To answer this question, the same crushing and washing of extracted root-filled teeth was undertaken, but the liquid was centrifuged, thereby removing the bacteria. Now the one cubic centimeter remaining of bacteria free water-like appearing liquid was injected into rabbits and they too developed heart lesions, even more severely than did rabbits injected with bacteria cultures alone.

In view of the fact it was believed the only injurious substance in infected teeth were bacteria, Price concluded that: "Infected teeth may contain, in additon to microorganisms, toxic substances which produce very profound effects upon experimental animals and which tend to prepare the tissues of the host, at least in some cases, for a more ready invasion by the organisms growing in that tooth." He found that by extracting infected teeth, crushing them, and then washing the powder, bacteria could still be found in the liquid. When he put the liquid in a centrifuge, the centrifugal force spun off the bacteria and sediment, leaving a clear liquid. When Dr. Price injected a small amount of this clear liquid into a rabbit, it lost 25 percent of its weight in four weeks and it died in the fifth week. Its brother rabbit, used as the control animal and not injected, continued to thrive and gain weight.