Place a small amount of four or five different brands of toothpaste into separate sterile petri dishes containing a culture medium. Expose the dishes to the air for thirty
minutes. Seal each lid with adhesive tape, and label it with the date and brand of toothpaste inside. Place the dishes in a warm, dark place.

In three days you will see which toothpaste contains chemicals that have the greatest effect upon bacterial growth.

Similarly, prepare the dishes with toothpaste samples, then use a toothpick to scrape some material from between your teeth, and make a line on each dish with the toothpick.

You can probably do the same thing with "antiseptic" mouth wash. Try it.

Some friends of mine, in a high school chemistry class, grew a cold culture in a very popular commercial brand of "antiseptic" mouthwash! Sometimes that particular mouthwash brand has ads that say that regular use of their product will help prevent catching a cold!