Artificial recurrent caries in glass ionomer-lined amalgam restorations

The purpose of this study was to examine artificial recurrent caries when a conventional glass ionomer liner was placed under amalgam restorations. An additional aim was to evaluate the effect of using an unfilled resin with or without etching on the margins of the amalgam restoration. Class V preparations in extracted third molars were used with gingival margins on root surfaces. Ten restorations were used for each of the following groups: 1) Amalgam alone; 2) Two layers of copal varnish and amalgam; 3) Glass ionomer, amalgam; 4) Glass ionomer, amalgam, unfilled resin; 5) Glass ionomer, amalgam, acid-etching, unfilled resin. The teeth were thermocycled and artificial caries were created using a liquid system acidified to pH 4.10 and saturated with HAP but without fluoride. The teeth were sectioned, polished and photographed using polarized light. Areas of recurrent caries were measured using a sonic digitizing pad. The data were analyzed using ANOVA and Duncan's Multiple Range Test. Areas for enamel lesions for the different groups were: 1) 1.29 +/- 0.41; 2) 1.61 +/- 0.49; 3) 0.92 +/- 0.26; 4) 0.87 +/- 0.31; 5) 0.99 +/- 0.39. Root lesions areas were: 1) 2.17 +/- 0.35; 2) 1.90 +/- 0.40; 3) 1.40 +/- 0.27; 4) 0.82 +/- 0.25; 5) 1.34 +/- 0.31. Duncan's groups for root lesions were A = B/ C = D/ and E separately. This study indicates that artificial recurrent caries under amalgam can be reduced with a conventional glass ionomer. An additional benefit was observed when unfilled resin was placed on the cavosurface margins but not when it was acid-etched first.