Answer:
Warm salt water has some quality of disinfectant. Some researchers shows that rinsing mouth from warm salt water can give relief from the inflamed gums caused by gingivitis.
It helps in rinsing the bacteria out of the mouth which can cause gum swelling and sore throat. It is also seen that warm salt water helps in killing some bacteria and do not allow pathogenic bacteria to accumulate in gums.
This is the reason why high salt concentration is used in pickles because it acts as a bactericidal agent