Background: Saliva contributes to oral homeostasis through lubrication, clearance and buffering of dietary acids. Acidic beverages can produce transient changes in salivary pH, although the magnitude and duration of the response vary with beverage composition and salivary factors. [¹, ⁶]

Aim: To compare changes in salivary pH after consumption of black coffee and lemon tea, using water as a control.

Materials and Methods: A three-arm, parallel-group randomised controlled trial was conducted among 90 healthy adults aged 20–30 years, with 30 participants in each group. Unstimulated whole saliva was collected at baseline, immediately after consumption of 20 mL of the assigned beverage, and 15 minutes later. Salivary pH was measured using a digital pH meter with a precision of 0.01. Between-group differences at each time point were assessed using one-way ANOVA followed by Tukey HSD post-hoc testing.

Results: Immediately after consumption, mean salivary pH decreased from 6.92 ± 0.25 to 6.11 ± 0.10 in the Black Coffee group and from 6.91 ± 0.27 to 5.62 ± 0.15 in the Lemon Tea group. In the Water group, pH increased slightly from 6.89 ± 0.26 to 6.94 ± 0.16. Between-group differences were significant immediately after consumption (F=672.506, p<0.0001) and at 15 minutes (F=72.899, p<0.0001). Repeated-measures ANOVA showed significant changes across the three time points in the Black Coffee group (F (2,58) =376.662, p<0.0001), Lemon Tea group (F (2,58) =1135.009, p<0.0001) and Water group (F (2,58) =4.232, p=0.019). At 15 minutes, pH had increased to 6.58 ± 0.10 after black coffee and 6.42 ± 0.11 after lemon tea, but remained below baseline.

Conclusion: Black coffee and lemon tea were associated with marked short-term reductions in salivary pH, with a greater reduction after lemon tea. Salivary pH showed partial recovery over 15 minutes but did not return completely to baseline.