1. Effectiveness of Mouthwash
Megan DiGuiseppe
Academy of Notre Dame

2. Purpose
The purpose of this experiment was to test the effectiveness of Listerine Antiseptic, a mouthwash that contains alcohol, and Crest Pro-Health, a mouthwash that does not contain alcohol, on oral bacteria. Not only was the effectiveness of each mouthwash observed, but also how long each rinse is effective.

3. Background
The active ingredients in Listerine Antiseptic are eucalyptol, methyl salicylate, thymol, and menthol. Ethanol (grain alcohol) is 26.9% of the product’s concentration
The active ingredient in Crest Pro-Health is 0.07% cetlyperadium chloride, which is a bacterial agent that attracts the bacteria in your mouth.
The oral cavity is home to hundreds of bacteria, viruses, protozoa, and fungi. However, of all the types of microbes, bacteria are the most numerous.
It has been estimated that there are over 100 million bacteria in every milliliter of saliva.

4. Hypothesis
The hypothesis was that Listerine Antiseptic mouthwash will kill the most oral bacteria immediately after use and be effective the longest because of the active ingredient of alcohol.

5. Materials Listerine Antiseptic Mouthwash Crest Pro-Health Mouthwash
32 Easy Gel Total Count agar vials and treated Petri dishes
Sterile cotton swabs
Sterile 20 ml measuring cups
Tap water
Incubator
Timer

6. Procedure Subjects rinsed with 20ml of tap water for 30 seconds
The inside of the subjects’ cheeks were swabbed
The swabs were mixed with agar vials and the mixture was poured into the dishes
Subjects rinsed their mouths with 20ml of Listerine Antiseptic mouthwash for 30 seconds
The swabs were mixed with the agar vials and the mixture was poured into the dishes
Waited 30 minutes
The subjects again swabbed the inside of their cheeks
The swabs were mixed with the agar vials and the mixtures were poured into the dishes
Waited 30 minutes
Their cheeks were swabbed once more and the mixtures were poured into the dishes
The dishes were incubated for 48 hours and the bacterial colonies were counted
The entire procedure was repeated again a week later using the Crest Pro-Health mouthwash

7. Variables Independent Variable: The brand of mouthwash
Dependant Variable: The number of bacterial colonies after each swabbing
Control: The swabbing after the mouths were rinsed with tap water
Constants: The amount of mouthwash and water, source of water, rinsing time, incubation time,

8. Graphs and Data

9. Graphs and Data

10. Summary Graph

11. Problems and Limitations
The results are limited because they only apply to high school-aged, Caucasian girls.
Because this experiment used human subjects, there were some minor timing and participation problems.

12. Further Studies
The same experiment could be conducted again using different brands of mouthwashes or toothpaste.
The effectiveness over a longer period of time could be tested.
This experiment could also be repeated using people of different ages, ethnicities, and gender

13. Conclusion
The first part of the hypothesis that Listerine would kill more bacteria immediately after use was rejected; however, the portion of the hypothesis that Listerine would be effective the longest was supported.

14. Work Cited
Arnold, P. (2010, July 22). Mouth Bacteria. It’s a Jungle in There. American Journal . Retrieved from
Bowers, C. (2010). Mouthwash Review: Crest Pro Health Rinse Vs. Listerine Antiseptic. Retrieved from Associated Context, Inc. website: =5
Colihan, K. (2008, October 7). Mouthwashes really do fight bad breath. WebMD Health News. Retrieved from breath
Gutundo, P. (2010). Mouth Bacteria . Retrieved from Bacteria&id=
Halitosis treatments: Using mouthwashes and mouth rinses to get rid of bad breath. (2010). Retrieved from Animated-Teeth website:
Listerine Antiseptic Mouthwash: Original . (n.d.). Retrieved from McNeill-PPC Inc.: Johnson and Johnson Healthcare Products Division website:
A mouthful on mouthwash. (n.d.). Retrieved from PlantetRx website:
Mouthwash. (2008). Retrieved from Cosmetic Dentistry Guide website:
Rosenberg, M., M.D. (2010). The Truth about Mouthwash . Retrieved from Ezine Articles