The provided line graph illustrates the fluctuations in the pH level in the mouth following the consumption of three types of sweet substances – fruit sugar, cane sugar, and honey – over a period of 40 minutes.
Overall, all three substances cause a sharp fall in pH shortly after being eaten before gradually returning to a neutral level. Among them, cane sugar results in the greatest and longest drop in pH, indicating a higher risk of tooth decay, while honey appears to be the least harmful.
Looking at the graph in detail, after the substances are consumed, the pH levels of all three drop significantly within the first five minutes. The most dramatic fall is seen in cane sugar, whose pH plunges to around 3.5, well below the threshold where tooth decay occurs. This low level persists for approximately 25 minutes before slowly increasing and returning to neutrality after about 40 minutes.
In contrast, fruit sugar and honey – both natural substances – experience less severe declines. At the five-minute mark, the pH levels reach roughly 4.25 for fruit sugar and 4.75 for honey. However, honey shows a quicker recovery, remaining stable between 5 and 10 minutes and then gradually rising to neutral (pH 7) by the 35th minute. Fruit sugar also recovers to the same neutral level but takes slightly longer, around 40 minutes in total.