Chlorhexidine as a recurrent marginal caries inhibitor : a televison microscope evaluation

Abstract

This study investigated the effectiveness of chlorhexidine and a cavity varnish in reducing the incidence of recurrent caries around amalgam restorations in vitro. This was accomplished by: (1) inserting amalgam restorations into Class V preparations to which a varnish (Copalite), a 1 percent chlorhcxidine gluconate solution, or chlorhexidine followed by the varnish were applied; (2) exposing the teeth with the restorations to a severe ciogenic challenge; and (3) measuring with the television microscope instrumentation the changes which occurred in the width of the gap between the amalgam and the cavity wall. Four groups of 12 intact bicuspids, previously extracted for orthodontic purposes and mounted in squares of self-curing resin, were used. Upon completion of the Class V Cavity preparations, the three treatments performed, and the cavity restored with amalgam, the teeth were exposed to a cariogenic challenge for six weeks, with a weekly change in the "artificial plaque" created by Streptococcus mutans. A group of teeth which received no treatment before the restoration was inserted served as controls. The television microscope measurement instrumentation which allowed a magnification of 250 X and measurements as small as one micron were used to identify and measure the width of the gap between the amalgam and the cavity wall before and after the teeth were exposed to the cariogenic challenge. The conclusions of this study were: (1) The use of chlorhexidine or a varnish or a combination of both produced a significantly smaller enlargement of the amalgam-cavity wall gap width when no treatment was performed before the insertion of the restoration. (2) Chlorhcxidine by itself or in combination with the varnish did not prove to be more effective in preventing the enlargement of the gap than the varnish. (3) The experimental model in which a cariogenic challenge was developed produced decalcifications that closely resembled those produced in the mouth situation. (4) The television microscope measurement instrumentation accurately measured the amalgam-cavity wall gap widths. (5) The evaluation did not permit a correlation between the increase in gap width and the carious process. It is the author's suggestion that for this purpose, future studies should be performed with histologic evaluations of enamel ground sections as one of the evaluation methods. (6) Before recommending the clinical use of chlorhcxidine as a recurrent marginal caries inhibitor, further research is necessary.