Susceptibility of selected tooth-coloured dental materials to damage by common erosive acids

Erosive substances such as gastric acids, lemon juice and even the less erosive cola drinks have been extensively investigated for their destructive effects on enamel. However, their effects on the tooth-coloured restoratives has not been widely analysed. The objective of this study was to assess their effects on the more commonly used glass containing restorative materials in vitro.

Sixty-eight anterior and 24 molar tooth crowns had restorations placed of Fuji IX, Ketac Fil(+), Fuji II LC or Z100, and were painted with nail varnish to leave a 2 mm border around the restorations. Six ceramic crown surfaces were also included. The anterior crowns and porcelain samples were exposed to 0.113% HCl, 5.0% citric acid, 0.02% orthophosphoric acid or DDW for 2, 4, 8 or 16 hours at 37 degrees C. The molar restorations were exposed only for 16 hours. The surfaces of the anterior teeth were then examined by SEM to assess progressive stages of surface erosive etching. Depths of bulk loss of vulnerable restorative materials were measured in the remaining 24 molar teeth, and compared with depths of adjacent enamel loss, particularly at the margins, using Leika Microscope images of sections through these restorations.

The traditional glass ionomer cements (GICs) were severely eroded by the HCl and citric acid solutions even following two hours of exposure, with only minor damage from phosphoric acid at the concentration tested. These materials experienced considerable bulk loss by 16 hours, comparable to or greater than that in adjacent enamel. The margins of the GIC restorations experienced greater dissolution than the body of the restorations, particularly in citric acid. Z100 Resin Composite and porcelain restorations showed no effects at all, and Fuji II LC only minor damage.

The results demonstrate the effectiveness of porcelain and resin containing materials in providing protection of enamel in advanced cases of erosion. The traditional GIC materials are vulnerable to severe damage in patients experiencing strong citric acid or gastric acid induced erosion. However, there is evidence that protective benefits are still present and these materials should be used but only in closed sandwich restorations in such cases.