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Science Project

What is the Effect of Phosphoric Acid
on the Loss of Tooth Enamel?

Researched by Elisa B.


The purpose of this experiment was to determine what the effect of different levels of phosphoric acid is on tooth enamel.

I became interested in this idea when I heard that the ingredients in soft drinks could decay
teeth if they were not brushed. Then I learned that phosphoric acid was a component in soft drinks such as Coke and Pepsi. So I wanted to find out if Phosphoric acid was one of the major ingredients in pop that can decay teeth.

The information gained from this experiment might help develop a new type of soft drink that is healthier for teeth. This information can also serve as a ëwarningí or to parents whose children are asking for a pop.


My hypothesis is if the concentration of the mixture is stronger, more tooth enamel
will be lost.

I base my hypothesis on my research. My research told me that people in the dental industry use phosphoric acid to etch away at tooth enamel. That led me to assume that the solution with the highest concentration of phosphoric acid would etch away the most tooth enamel.


The constants in this study were:
- type of tooth (wisdom teeth)
- length of time teeth were exposed to solutions
- size of the container solution was in (between 100 and 150 mL)
- total quantity of solution in each container -- 80 mL per container

The manipulated variable was the amount of concentration in each acid solution. There were three experimental groups (A, B, and C) each containing the five different strengths of phosphoric acid solutions.

The responding variable was how much tooth enamel remained. The total remaining enamel was weighed before and after a seven day trial period. To measure the responding variable, I weighed each tooth (to the nearest tenth of a milligram) before the experiment. After the trials I dried the teeth in the vacuum oven for six hours ­ 82°. Then I weighed the teeth to find the results.





100 - 150 mL glass containers


wisdom teeth


355 mL can of Pepsi


355 mL can of Coca-Cola


pH meter


MagneStir  Mixing bar


 analytical balance (Metler-Toledo)


drying oven


vacuum oven






 all safety clothing (i.e. latex gloves, lab coat, tweezers or tongs)


1. Autoclave teeth for 30 minutes at 93.3 °C
2. Put on Latex gloves.
3. Mark drying dishes for five teeth # 1-5 A, five teeth # 1-5 B, and five teeth #1-5 C. Dry in drying oven 1 hour. Cool in desiccator.
4. Weigh each drying dish. Record weights to the nearest tenth of a milligram.
5. Place one tooth in each drying dish.  Dry in vacuum oven 6 hours at 82 °C. Remove with tongs and place in desiccator until cool.
6. Weigh each tooth in its drying dish. Record weights to the nearest tenth of a milligram.
The tooth weight is the difference between weights in steps 3 and 5.

7. Test Coca-Cola phosphoric acid level with sodium hydroxide titration Method.
8. Repeat test with Pepsi.
9. Take average of results of steps 1 & 2 (value A).
10. Separate fifteen  -- 100-150 mL glass containers.
Mark five containers # 1-5 A, five containers # 1-5 B, and five containers #1-5 C.

11. Wear lab coat. Lab coats are optional, but they are helpful when handling
phosphoric acid ( for safety).

12. Mix five strengths of phosphoric acid solutions as follows:
  Zero strength -- Control -- group 1 (Replications A, B, C)
  Half of value A -- group 2
  Value A -- group 3
  1.5  times value A -- group 4
  Two times value A -- group 5
13. Measure the different mixtures of acid levels into containers. Use 80 mL per container.

14. Using gloves and tweezers / tongs, put one tooth into each mixture (according to labels that were marked on drying dishes and jars).
15. Leave teeth in solutions for 7 days.

16. Remove teeth (gently) with tweezers, from containers. Rinse with hot tap water and deionized water. Place teeth back into the original drying dishes.
17. Dry in a vacuum oven for four hours at 82 °C.

18. Let teeth cool in desiccator for one hour.
19. Weigh cooled teeth. Record to the nearest tenth of a milligram.

20. Clean up harmful substances after trials.
21. Put results into graphs
22. Add Coke and Pepsi values to a graph to see how much tooth enamel would be lost to the phosphoric acid levels in Coke and Pepsi.
23.Take at least two pictures of trials.


The original purpose of this experiment was to find out how much tooth enamel would be lost to different levels of Phosphoric Acid in water solutions.

The results of the experiment were when the solution with the most reactant (solution/ group # 5) was tested against the teeth, more tooth enamel was etched away, compared to the solutions/ groups or one or two. Also the teeth in Group 5 weighed less than the teeth in Group 2. See the table and graph below.


My hypothesis was that concentration of the mixture is stronger, more tooth enamel
will be lost. The results indicate that this hypothesis should be accepted. The results of the experiment were when the solution with the most reactant (solution/ group # 5) was tested against the teeth, more tooth enamel was etched away, compared to the solutions/ groups or one or two. Also the teeth in group 5 weighed less than the teeth in group 2.

Because of the results of this experiment, I wonder if a soda pop with less Phosphoric acid in it could be made, so it would not decay the teeth as much. If I were to conduct this project again I would take pictures that showed more of the activity, so that the reader could better understand what was happening. I would also be even more precise about my timing (in getting things in & out of the autoclave/vacuum oven/drying oven) so as not to effect the weights of the teeth. 



A lot of people in our society drink soda pop. Many soft drinks that are colas (like Coke and Pepsi) have phosphoric acid added to them. Phosphoric acid is added to them for flavoring.

ìPhosphoric Acid is a clear colorless liquid, H3PO4, used in fertilizers,
soaps and detergents.î
-- The American Heritage Dictionary


Tooth Terms: a glossary - parts of a tooth

The Pulp Cavity is located in the center of the tooth. It contains the arteries, veins and nerves. Blood Vessels carry nutrients to the tooth. The Root Canal is the canal in the root of the tooth where the blood vessels and nerves travel through. The Nerves relay signals such as pain to and from your brain. Cementum is the layer of hard tissue covering the root of the tooth. The Cemento-enamel Junction is where the enamel and cementum intersect. Enamel is the hard, white outer layer of the tooth. Dentin is the firm, yellow tissue underlying the enamel and cementum, making up the basic bulk of the tooth. The Crown is the part of the tooth that emerges above the gum tissue that you can see. Gingiva is the gum tissue surrounding the tooth. The Peridontal Ligament is the tissue under the gum that surrounds the tooth and connects it to the bone. The Alveolar Bone (or Jawbone) forms the tooth socket and provides it with support.


Mineral Acids
Some examples of Mineral Acids are Sulfuric, Nitric, Phosphoric, and Hydrochloric acids.

Organic Acids
Organic Acids contain carbon. Tartaric and Citric are two examples of Organic Acids.


Most acids will etch away at the tooth enamel, making the tooth weaker, and after time defenseless. One would experience toothaches often that would be caused by acids and/or sugars directly contacting the Dentin surface of the tooth. The dentin surface is the layer surrounding the pulp cavity. If the enamel was not there protecting the Dentin layer one would experience pain.


Teeth are very important to humans. They help us bite/chew our food, enable us to rip packages open and do other every day things we do not realize are very important. If a person lost their teeth they would not be able to do those things. Luckily, man has come up with the invention of Dentures and false teeth.

It is important to keep our teeth healthy so we do not loose them. People who do not brush their teeth often enough, wold likely get cavities. Cavities are like little ìtooth wormsî that bore holes through the layers of the tooth straight to the pulp. If you feel a cavity you should see a dentist.

There are many products that are sold in grocery stores to aid you in keeping your teeth healthy. The most commonly used items are toothbrushes, tooth paste and dental floss. It is recommended you visit a dentist every six months. Dentists do a special brushing job and make sure your teeth are healthy.


American Heritage Dictionary ìPhosphoric Acidî New York, New York, Dell Publishing Co. ©1988

Knapp, Brian - B.Sc., Ph.D. Hydrogen and the Noble Gasses. Europe: Atlantic Europe Publishing Co. Ltd. © 1996. Danbury, CT: Grolier Educational. Pp. 18 and 19

Knapp, Brian - B.Sc., Ph.D. Nitrogen and Phosphorus. Europe: Atlantic Europe Publishing Co. Ltd. 1996. Danbury, CT: Grolier Educational © 1996. Pp. 38 ­ 44

ìPhosphoric Acid, î Microsoft Encarta ë98 Encyclopedia. ©  1993-1994 Microsoft Corp.

ìThe Anatomy of a Toothî The Wisdom Tooth Home Page [Online] Available  ©1997


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