Surface Hardness of Restorative Materials Exposed to Sour Thai Fruit

Objective: Little has known about the effect of consumption sour fruit on the restorative materials. The aim of this study was to investigate the erosive potential of sour Thai fruit juice on surface hardness of the four restorative materials. Method: Twenty specimens (12mm diameter, 2.5mm height) of four restorative materials; a conventional glass-ionomer cement (Ketac-s), a resin-modified glass-ionomer cement (Fuji II LC), composite resin (Filtek) and amalgam (Valiant) were prepared and stored for 1 h at 37oC after mixing. Specimens were divided into 4 groups: deionized water (control), citrate buffer pH 5 (comparator), green mangoes and pineapple juices. These juices were prepared using a juicer machine and then filtered with a thin cloth. The pH of storage media was determined using pH meter (ORION 520A). Microhardness testing (Micromet II) were performed prior and after immersed at each interval time. The hardness values were compared using ANOVA (repeated measurement) and multiple comparison test. Result: The pH of green mango and pineapple juice were 2.5 and 3.6 respectively. The means of surface hardness (kg/mm²) at 1h prior transferring to storage media were as follow: Fuji II LC=50.5±0.9, Ketac-s=53.5±1.0, Filtek=83.4±2.0 and Valiant=100.4±2.7. The greatest reduction in surface hardness was found in all materials immersed in green mango juice. On immersion in deionised water, little change was noted over the test period. The reduction in surface hardness of Fuji II LC, the trend was similar to Ketac-s. Valiant showed a few changes in hardness when exposed to various storage media. Conclusion: These results indicate that sour Thai fruits have an influence on the surface hardness of restorative materials over test period. The green mango juice produced the most marked reduction in surface hardness to materials.