Aim: To study the acidogenic response in human dental plaque in vivo with fresh orange juice compared to orange fruit drink with no added sugar and regular orange fruit drink that were currently available in the market.
 Materials and Methods: Ninety subjects aged 18-30 years were allocated randomly into 3 groups. 10 ml of each experimental drink was given to the subjects in each group and instructed to keep in mouth for 2 minutes before swallowing. Intrinsic pH of the test drinks was measured by the Digital pH meter. Plaque pH was measured at the baseline, immediately after consumption and at 1,15 and 30minutes post consumption.
 Result: Inter group comparison by ANOVA showed significant difference among mean pH values and time intervals. There was significant drop in plaque pH in all the three groups after 1minute. Tropicana group showed drop in pH even after 30 minutes while in other two groups, pH returned to initial levels at the end of 30minutes.
 Conclusion: The results of our study showed that, plaque pH dropped rapidly after 1 minute of consumption of all the three fruit juices. Plaque pH returned to initial levels in two groups while in tropicana group, it declined.