Science experiment, mouth wash?

Question

how can i measure the efficacy of a mouth wash??

Answer 1

Well, if the mouthwash is supposed to kill germs - that's the "effect" it's supposed to have, so that's what you would want to measure - then you could take a swab inside your mouth before and after rinsing with the mouthwash, and test the swabs for germs.

This is traditionally done using something called a "growth medium."  You can probably just use plain gelatin (the unflavored kind) to make that at home.  You can buy powdered plain gelatin at the grocery store (Knoxx is the brand I'm familiar with).  Dissolve the gelatin in a minimal amount of hot water, pour it into a mould (a pickle jar lid or something, as long as it's clean).  Make two of these, one for each swab (labelled properly, i.e., "before mouthwash" and "after mouthwash.")  When they're set, prepare the swabs, then wipe them across their respective gelatin surface.  Cover with plastic wrap and let them sit undisturbed for a few days or until you see some bacterial colonies growing.

You will want to write down your procedure in detail.  As in, enough detail so that someone could redo the exact same experiment just using your notes.

You will also need to decide on a way to measure the amount of bacteria from each swab - maybe you could take pictures and then measure how much of the surface area is covered by bacteria on each one.  If more is covered on the "before mouthwash" one, then you can conclude that the mouthwash was effective (to some extent).  If they are the same, then the mouthwash was not effective.

Good luck!

Edited to add:  before you try this at home, talk to your science teacher about safety.