Effectiveness of Mouthwash

Megan DiGuiseppeAcademy of Notre Dame

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.

BackgroundThe 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.

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.

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

Procedure1. Subjects rinsed with 20ml of tap

water for 30 seconds

2. The inside of the subjects’ cheeks were swabbed

3. The swabs were mixed with agar vials and the mixture was poured into the dishes

4. Subjects rinsed their mouths with 20ml of Listerine Antiseptic mouthwash for 30 seconds

5. The inside of the subjects’ cheeks were swabbed

6. The swabs were mixed with the agar vials and the mixture was poured into the dishes

7. Waited 30 minutes

8. The subjects again swabbed the inside of their cheeks

9. The swabs were mixed with the agar vials and the mixtures were poured into the dishes

10. Waited 30 minutes

11. Their cheeks were swabbed once more and the mixtures were poured into the dishes

12. The dishes were incubated for 48 hours and the bacterial colonies were counted

13. The entire procedure was repeated again a week later using the Crest Pro-Health mouthwash

VariablesIndependent 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,

Graphs and Data

Graphs and Data

Summary Graph

Problems and LimitationsThe 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.

Further StudiesThe 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

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.

Work Cited Arnold, P. (2010, July 22). Mouth Bacteria. It’s a Jungle in There. American Journal .

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