Question

Why does the medium become acidic in mouth what is its illeffects?

Answer 1

Saliva is basic so your mouth is basic when you not brush it happens

Answer 2

saliva is basic so mouth should be basic but if you dont brush your teeth bacteria attacks and due to their presence mouth becomes acidic . the saliva helps to neutralize but u need to brush.
if it becomes acidic then not only it attracts more bacteria but also speeds up enamel decay
hope it helps comment if any doubt