In searching for foci of infection as a cause of systemic disease, the teeth are most often suspected. Satisfactory roentgenograms, together with careful direct inspection and tests for vitality, make an evaluation of the teeth as sources of infection less difficult than is the case with the other common foci. However, there is a surprising lack of agreement as to which teeth are to be considered foci of infection. Often the condition is obvious, but difficulty arises in deciding the fate of (1) pulpless teeth showing roentgenographically extremely little or no change at the root, (2) root fragments left from previous attempts at extraction which are roentgenographically negative, (3) so-called residual areas of bone condensation or rarefaction at the site from which a tooth has been removed, and (4) teeth that respond to the electric current and have only slight changes at the tip and about the shafts in films.
ROENTGENOGRAPHICALLY NEGATIVE PULPLESS TEETH AS FOCI OF INFECTION. JAMA. 1933;100(12):974–975. doi:10.1001/jama.1933.02740120112016