Effectiveness of Various Toothpastes on the Bacteria on Teeth


The purpose of this experiment was to determine the effectiveness of various toothpastes in reducing the bacteria on teeth.

I became interested in this idea when I was brushing my teeth. I started wondering if the brand of toothpaste I was using was sufficiently removing the bacteria in my mouth. I knew that bacteria on teeth are the main cause of plaque, so reducing bacteria should improve the health of my teeth.

The information gained from this experiment could help dentists and consumers in our society to choose the type of toothpaste that would reduce bacteria best, thus improving dental health.


My hypothesis was that Colgate Total would reduce the amount of bacteria most.

I based my hypothesis on the fact that Colgate Total has the ingredient Triclosan, a strong antibacterial/antimicrobial agent.


The constants in this study were:

•  Time between brushing and swabbing

•  The teeth brushing method used by subjects

•  Bacteria sampling method

•  Time frame project was conducted

•  Amount of time teeth were swabbed

•  Type of toothbrush used

•  Type of swab used

•  Type of agar

•  Type of Petri dish

•   Incubation Time

•  Type of incubator

•  Incubation temperature at 35 degrees Celsius 

•  Students used daily for testing

•  Amount of toothpaste on each toothbrush

The manipulated variable was the type of toothpaste.

The responding variable was the change in the amount of bacteria on the teeth before and after brushing.

To measure the responding variable, I counted the bacteria colonies visible on the agar plates after incubation.


Item Description
Container of Colgate Total with Triclosan Toothpaste
Container of Tom’s of Maine Natural Antiplaque Toothpaste
Container of Crest Dual Action Whitening Toothpaste
Western Family Medium Toothbrushes
Pieces of Parafilm
Pair of Gloves
Lab Coat
Sterile Swabs
10 µ Syringe
Syringe Tips
Test Tubes
Giant Pipette
Blood Agar Dishes
Bio-containment Hood
Incubator that keeps contents at 35 degrees Celsius


I.  Start of the experiment

a)    Collect the signed permission forms from the volunteers

b)    Obtain the materials

c)    Gather the subjects

II. Water Rinse Test

a)    Fill each cup with water.

b)    Swish in mouth for about 5 to 10 seconds.

c)    Spit the water out in the sink and open the swab 

d)    Swab the teeth in slow motions reaching each surface on the teeth.

e)    Put each sterile swab in the sterile carrying case, label with the subject, and “WR” for water rinse written in black pen.

III. Test Colgate Total with Triclosan Toothpaste

a)    Direct the student to their stations

b)    Answer any questions being asked.

c)    Apply the toothpaste to the toothbrush

d)    Instruct the subjects in brushing their teeth for two minutes.

e)    Have each subject swab the rows of teeth, top and bottom, left and
right, in slow motions.

f)    Place the sterile swabs in the sterile carrying case, with the following information written in black pen on the container,

•    The subject number

•    “CT” for Colgate Total

IV. Test Tom’s Of Maine Fluoride-Free Antigingivitas Toothpaste

a)    Repeat steps II.

b)    Repeat steps III. a-e using Tom’s of Maine Fluoride-Free Toothpaste

)    Place the swabs in the sterile carrying case with the following information written in black pen,

•    The subject number

•    “TM” for Tom’s of Maine

V.  Test Crest Cool Mint Toothpaste

a)    On the following day (after the testing of Tom’s Of Maine) repeat steps II. 

b)    Repeat Steps III. a-d

c)    Place the swabs in the sterile carrying case with the following information in black pen or marker in the name and specimen section;

•    Name- Subject number

•    Specimen- “CR”

•    Date

VI. Incubate the Bacteria Samples

a)    Go to the hospital laboratory, preferably the same day, with the
sterile swabs in the carrying cases.

b)    Put on the lab coat, and gloves.

c)    Receive the test tubes.

d)    Label the test tubes with the subject and name (toothpaste; “CT” for Colgate Total, “Cr” for Crest, and “Tm” for Tom’s of Maine; or the water     rinse and date)

e)    Fill each test tube with 1 ml of water.

f)    Place each swab in the 1 ml of sterile water.

g)    Cover each test tube with parafilm.

h)    Vortex (mechanically mix) each test tube for 5 seconds.

i)    Label each plate with the following information,

•    Number of the subject

•    Type of toothpaste or water rinse

•    The measurement; 10 micro liters or 10 µ

•    The date for water rinses.

j)    By using a 10 µ syringe put 10 µ on one Petri plate.

k)    Spread evenly across the plate.

l)    Incubate the plates for 24-48 hours at 35 degrees Celsius.

m)    Wash hands.

VII. Measure and Compare the Results

a)    Return to the lab 24- 48 hours later.

b)    Put on the lab gear.

c)    Count the number of visible colonies on the Petri plates, with the unaided eye under a white light.

d)    Record the number of colonies on a data table.

e)    Have the designated supervisor autoclave all dishes and swabs.

The original purpose of this experiment was to determine the effectiveness of various toothpastes in reducing the bacteria on teeth.

The results of the experiment were Colgate Total, on average, removed the most bacteria by about 121, 667 colonies of bacteria. On average, Tom’s of Maine removed the second most bacteria colonies by about 117,356. Crest Dual Action Whitening toothpaste removed the least amount of bacteria, 24, 167, and all water rinses produced about 200,000 bacteria colonies or more.


My original hypothesis was that Colgate Total would reduce the amount of bacteria most.

The results indicate that this hypothesis should be accepted, because Colgate Total reduced the bacteria more than any other brand of toothpaste.

After thinking about the results of this experiment, I wonder if…

•    The amount of toothpaste would affect the removal or reduction of bacteria.

•    Various brands of mouthwash would reduce bacteria more efficiently than toothpastes.

•    Different toothbrushes affect the amount of bacteria on teeth.

•    Electric toothbrushes remove more bacteria than manual ones.

If I were to conduct this project again I would have…

•    Either swabbed the subject’s mouth myself or had them swab their mouths with me monitoring their technique.

•    Put more milliliters of sterile water into the test tubes to reduce the initial concentration of bacteria used to inoculate the agar.

•    Tested more subjects to even out the average.

Researched by --- Rainan V


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