Newly Devised Caries Susceptibility Tests and their Clinical Application for Restorative Dentistry

Abstract

When cavities are prepared in clinical practice, the outline form is generally established by following the law of extension for prevention advocated by G.V. Black, who placed stress on the unclean area and immune area of tooth surfaces. In this case, not much consideration has so far been given to caries immunity of the oral environment, that is, caries susceptibility. So it seems to be reasonable that the concept of caries susceptibility is introduced into the conventional cavity preparation.The purpose of this study is to investigate the proper testing methods for determining individual caries susceptibility which could be an effective measure when preparing the cavity under the law of extension for prevention. Thus, attention was focussed on the acid buffering property of saliva as an environmental factor and the acid solubility of enamel as a host factor.In this article, the effect of storage conditions of saliva on acid buffering capacity was first studied and then a unique method for the buffering capacity test was devised and its availability was examined.The results were as follows;1. Saliva stored for 3 hours in air showed considerably higher pH and acid buffering capacity than saliva stored for 3 hours without air or saliva immediately after collection. In the conventional measurement of the buffering capacity in air, pH values of the salva increase depending upon the amount of stirring and subsequent standing time, and are unstable. A quasi-anaerobic measurement of the buffering capacity was therefore designed.2. A special apparatus with a Beckman pH combination electrode fitted in the piston of the injection syringe was devised. In the measurement, pH of the saliva (1ml) sucked through the injection needle was read (initial pH) and then was again read after suction of 0.1ml of lactic acid and stirring (final pH). Final pH/initial pH was expressed as the value of the acid buffering capacity.3. According to the new method, the pH and the buffering capacity of the same individual were stable with several measurements of different saliva.4. The pH and the buffering capacity of saliva stored for 3 hours without air were the same as those of saliva immediately after collection.5. When the pH and the buffering capacity of saliva of the same individual were determined in the spring and autumn, the values of both salivas did not show any difference.The new method presents good reproducibility of the pH value of the saliva, and proves to be available for the buffering capacity test.