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Figure 1. Experimental set-up. (A) pH measurements (pH0) and titration of soft drink with 1 M NaOH to a pH above 5.5 (N = 20). From these data, the titratable acidity was determined in µL 1 M NaOH. (B) Addition of 50 mg of pure hydroxyapatite (HAp) crystals to the drink (N = 20), under constant stirring, and pH recordings every 15 sec (pH1–pH12). After the initial recordings, the drink was left with constant stirring until the last pH recording was obtained after 30 min (pH13). (C) Titratable acidity (from Fig. 1A) up to each pH value obtained over time in response to HAp dissolution in the drinks (from Fig. 1B). The amount (µL) of base (1 M NaOH) needed to obtain each pH value induced by HAp addition was used to calculate the amount of HAp crystals dissolved (mg) per sec per liter soft drink (N = 20). In (C), iEP denotes the initial erosive potential (i.e., during the first minutes of exposure), and eEP denotes the end erosive potential (i.e., after 30 min).
