25,26 From the present study, green mango juice provided customer review the greatest titratable acidity and also degraded the restorative materials tested (except Valiant-Ph.D. amalgam) more than the other storage media. Although pineapple juice had a lower pH value (3.68) than citrate buffer solution (5.00), the pineapple juice had a lesser titratable acidity than the citrate buffer solution. Therefore, pineapple juice seemed to be less effective in degrading the materials. Another possible explanation might be that pineapple contains some components that may provide a protective effect against erosion. This explanation is consistent with the SEM photomicrographs which observed a ��plaque-like�� covering layer. Therefore, further investigation regarding this phenomenon is required.
In this present study, after Ketac-S was immersed for 2 days or more in green mango juice, it became increasingly soft until the hardness could no longer be measured. This may result from extensive dissolution of this material by acid attack at the interfacial bonding between the silver alloy fillers and the polyacrylate matrix.27 These results suggest that in clinical decision-making, this material may not be suitable for patients who have the habit of eating sour fruits, which has acidic ingredients, like green mangoes. With Fuji II LC, the reduction in surface hardness may be caused by a selective attack on the polysalt matrix among the residual particles.28 The polysalt matrix of the set cement results from the formation of contact cation-anion ion pairs or complexes between the carboxylic groups of the polyalkenoic acid and metallic ions, especially trivalent aluminium, leached from the glass particles.
Another possible explanation is that resin-modified glass ionomer cement may release additional fluoride after immersion in acidic environments. This can result from the dissolution of matrix-forming constituents within the restorative material.28 However, some research indicates that it may also resist acid better than a conventional glass ionomer cement, as was found in studies by Shabanian and Richards,12 McKenzie et al13 and Aliping-McKenzie et al.29 As regards Filtek Z250 resin composite, the deterioration of its physical and mechanical properties could be due to a hydrolytic breakdown of the bond between silane and the filler particles, filler-matrix debonding, or even hydrolytic degradation of the fillers.
30,31 Alternately, it could be due to chemical degradation occurring via hydrolysis. Progressive degradation altered the microstructure of the composite bulk through the formation of pores.31 In this present study, Filtek Z250 resisted acid solution better than Drug_discovery did Fuji II LC, which is consistent with the results found in other studies.12,15,32,33 Here in this study, surface hardness results showed that amalgam was harder than the other materials in all storage solutions after immersion for all evaluated time periods.