Objectives: This study aim to evaluate the effect of Greek yogurt on the tooth surface by comparing it with liquid fermented milk. Methods: After purchasing Greek yogurt available on the domestic market and measuring pH and titratable acidity, Greek yogurt was selected as the Greek yogurt group, Jeju Samdasoo as themineral water group, and liquid fermented milk as the liquid fermented milk group. The specimens were treated with the experimental drinks for 30 minutes. Afterwards, the change in surface microhardness of the tooth surface was measured and the surface change was observed. Results: The pH of the experimental beverage was slightly higher in the Greek yogurt group than the liquid fermented milk group. In the effect of Greek yogurt on tooth surface hardness, there wasa statistically significant difference in surface microhardness before and after immersion in the liquid fermented milk group, but there was no significant difference between the mineral water group and the Greek yogurt group. When comparing the surface microhardness change values among groups, the difference in surface microhardness (△VHN) between before and after 30 minutes of immersion showed a statistically significant difference between the liquid fermented milk group and the mineral water group and ...