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This in vitro study evaluated the effect of a prolonged erosive pH cycling on the superficial microhardness change (SMHC) and the erosive wear of different restorative materials. Eighty enamel specimens with prepared cavities of 1·5 × 1·5 mm were randomly divided into eight groups according to the restorative materials used for the fillings (RMGI – resin-modified glass–ionomer, CGI – conventional glass–ionomer, CR– composite resin, A – amalgam) and immersion media used (ERO – erosive medium or SAL – artificial saliva). During 35 days, half of the specimens were immersed in a cola drink (ERO), for 5 min, three times a day, and they remained in SAL between the erosive cycles. The other half of the specimens was immersed in SAL only, for the entire experimental period (control). Data were tested for significant differences byanova and Tukey’s tests ( P < 0·05). Scanning electron microscopy images were made to illustrate the enamel erosive wear and restorative materials alterations. The mean SMHC (%) and mean erosive wear (μm) of the materials were: RMGI-ERO (30/0·5); CGI-ERO (37/0·5); CR-ERO (−0·3/0·3); A-ERO (−4/0·3); RMGI-SAL (4/0·4); CGI-SAL (−6/0·4); CR-SAL (−3/0·2) and A-SAL (2/0·4). Scanning electron microscopy images showed pronounced enamel erosive wear on groups submitted to erosive pH cycling when compared with groups maintained in saliva. In conclusion, the prolonged pH cycling promoted significantly higher alterations (SMHC and erosive wear) on the glass–ionomer cements than the CR and amalgam. [ABSTRACT FROM AUTHOR]

This in vitro study evaluated the effect of erosive pH cycling on the percentage of surface microhardness change (%SMHC) and wear of different restorative materials and bovine enamel restored with these materials. Eighty enamel specimens were randomly divided into eight groups according to the restorative materials and immersion media used: GI/GV--resin-modified glass-ionomer, GII/GVI--conventional glass-ionomer, GIII/GVII--resin composite and GIV/GVIII--amalgam. Over a period of seven days, groups GI to GIV were immersed in a cola drink (ERO) for 5 minutes, 3x/day and kept in artificial saliva between erosive cycles. Groups GV to GVIII were immersed in artificial saliva (SAL) throughout the entire experimental period (control). Data were tested for significant differences using ANOVA and Tukey's tests (p<0.05). For %SMHC, considering the restorative materials, no significant differences were detected among the materials and immersion media. Mean wear was higher for the resin modified glass ionomer cement when compared to conventional cement, but those materials did not significantly differ from the others. For enamel analyses, erosive pH cycling promoted higher wear and %SMHC compared to saliva. There were no significant differences in wear and %SMHC of enamel around the different restorative materials, regardless of the distance from the restorative material (50, 150 or 300 µm). In conclusion, there were only subtle differences among the materials, and these differences were not able to protect the surrounding enamel from erosion. [ABSTRACT FROM AUTHOR]