Figure 3. Erosive potential and soft drink pH. (A) Relationship between the initial erosive potential (i.e., erosive potential during the first minutes of exposure) and the pH (open circles) for all drinks (N = 20). As shown, the initial erosive potential was almost a logarithmic function of the pH, increasing ten-fold for each one-unit decrease in pH. The erosive potential of the drinks was reduced, more so in drinks with low pH values and high initial erosive potential, when the HAp crystals were coated with human salivary proteins (bold circles), illustrated by the gray area between the lines (N = 20). (B) Corresponding relationship between the end erosive potential (i.e., erosive potential after 30 min) and the pH in the drinks (N = 20). Only a very limited effect was seen from the human salivary protein on the end erosive potential of the drinks, as illustrated by the reduction in size of the grey area compared with Fig. 3A (N = 20).