The Sterilization of Carious Dentine

Abstract

A bacteriological investigation into the efficiency of over thirty agents as bactericides for carious dentine has been carried out. It has been shown that the soluble salts of the heavy metals, as a group, are most successful in the sterilization of carious dentine. Of these, silver nitrate, either in the anmmoniacal or the concentrated aqueous form, is the most effective. The soluble zinc salts such as zinc iodide and zinc chloride are not as efficient for sterilizing dentine but will not stain the tooth substance. Examination of histological sections of teeth in which cavities were prepared and which were treated with various bactericides shows that silver nitrate applied to exposed vital dentine produces a remarkably slight reaction in the pulpal tissues. This is due to the precipitation of the silver nitrate in a less toxic form by the tissue fluid chlorides, phosphates and proteins within the dentinal tubules. The precipitation results in diffusion currents carrying still further chlorides, phosphates and proteins into the affected dentinal tubules from the tissue fluid spaces of the pulp. In the majority of cases the silver nitrate is, therefore, unable to exert its toxic effect on the cells of the pulp as it is precipitated in insoluble and less toxic forms before it is able to reach them. These insoluble precipitates may be carried down the tissue fluid spaces of the pulp and peripherally into other dentinal tubules without causing gross damage to the cells with which they come into contact. wn cases of successful applications of the ammoniacal silver nitrate to exposed vital dentine, it is seen to penetrate the tissue fluid channels of the dentine, including the lateral communications of the dentinal tubules. Applied to carious dentine, the superficial layers of the caries become thoroughly impregnated with the silver salts; the deeper layers may also be seen to contain silver particles which, however, are thought to represent silver in a less toxic and bactericidal form. © 1949, The Royal Society of Medicine. All rights reserved.