Effect of Acid Beverage on the Microhardness of Primary Tooth Enamel In Vitro

Purpose: To assess the effects of a soft drink, a soybean-based apple juice and strawberry juice on the superficial and deep microhardness of primary tooth enamel.
Methods: Sixty primary teeth were divided according to the beverages and a control group (artificial saliva). Immersion cycles were carried out under agitation (five minutes three times a day over 60 days). Superficial microhardness measurements were taken after seven, 15, 30, 45, and 60 days. Teeth were cut for deep microhardness evaluation. Analysis of variance and Tukey's test (95 percent confidence interval) were used for data analysis. Teeth were scanned by electron microscopy for quantitative analysis.
Results: The soybean drink led to a significant decrease in the superficial microhardness ( P <0.05) at all tested times. The decrease for the strawberry juice was steeper than for the soybean drink and the soft drink significantly decreased the superficial microhardness at all times. The soybean drink recorded lower surface deep microhardness values while the juice presented similar results to the soybean drink at a depth of up to 200 μm. There was a gradual and statistically significant increase at a depth of up to 300 μm with the soft drink. Scanning electron microscopy evaluation showed that all beverages had gradual demineralization, being evident on the 60th day; the soft drink showed the greatest overall loss of enamel.
Conclusion: All beverages affected the microhardness of primary teeth enamel. The soft drink was the most harmful to enamel among the assessed beverages.