Question

The nature of toothpaste is ______:
A. Acidic
B. Basic
C. Neutral
D. None of the above

Answer 1

Hint: The action of bacteria inside the mouth occurs inside an acidic medium, and for any kind of toothpaste to be even the slightest bit effective, it would have to neutralise this medium of action.

Step-by-Step Solution:
Let us in detail try and understand the nature of toothpastes, why it is so and the compounds that make up the composition of the toothpaste and their action on teeth.
Toothpastes are usually weakly basic in nature. PH of saliva is 7.4, which is basic too. An acidic environment will cause teeth enamel to corrode, and will ultimately weaken them.
So, the two ingredients giving toothpaste a basic nature are:
The sequestering agent tetrasodium pyrophosphate (TSPP) which removes calcium and magnesium from the saliva, so they can't deposit on teeth as insoluble deposits called tartar, (calcified plaque).
In this respect it acts as a water-softening agent. It won't remove tartar that already exists. Tooth brushes provide the mechanical force and vehicle to remove the deposits physically, to be rinsed out.
TSPP is slightly alkaline, and has a bitter taste, therefore additional flavourings are required to mask it. Also, additional detergents must be added to keep it in solution.
Therefore, through this analysis and information we can easily conclude that the answer to this question is b)

Note: Bear in mind that the knowledge of either the acidic nature of the mouth or the basic nature of the saliva is not enough for you to be able to solve this question effectively. The knowledge of the composition of toothpaste is also very important to understand the chemistry and the resultant action of toothpaste.