Swishing with warm salt water may not help to prevent mouth disease in otherwise health individuals.
Salt water rinse can be used as adjunct to routine mechanical plaque
control for prevention of oral diseases.
The study participants would have experienced some improvement not
specifically associated with the therapeutic properties of the test
agent, but rather related to behavioral change known as Hawthorne
effect. (jisppd.com)
Swishing with warm salt water may help to prevent or cure mouth wounds in some conditions:
1) After tooth extraction
The instruction to use warm saline mouth rinse is beneficial in the
prevention of alveolar osteitis after dental extractions. There is no
significant difference in the efficacy of the twice-daily warm saline
mouth rinse regimen compared to the six times daily regimen. (Evidence-Based Dental Practice, 2015)
2) After surgery in the mouth, swishing warm salt water may help prevent infections:
Chlorhexidine, warm salt water and warm tap water averagely produced
the same number of colony forming units of bacteria, which shows that
the three different mouth washes are equally effective as
post-operative mouth rinses after oral surgery. (J Maxillofac Oral Surg., 2015)
3) After chemotherapy
Rinsing with a mixture of saltwater and 3% hydrogen peroxide. (The
mixture should have 2 or 3 times the amount of saltwater than hydrogen
peroxide.) To make the saltwater mixture, put 1/4 teaspoon of salt in
1 cup of water. This helps clean wounds in the mouth. (PDQ Cancer
Information Summaries, 2019)