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Teeth Discoloration



The natural color of our teeth is light grey or light yellow. Teeth whitening solutions can help our teeth become whiter. However, some of the food and beverages we consume daily can stain and discolor our teeth. There are two types of teeth stains, namely intrinsic stain or extrinsic stain. Intrinsic stains are caused by age, malnutrition, infections or genetic reasons. Extrinsic stains are more manageable. They are caused by the food and beverages that we consume. These stains are merely cosmetic and can be removed by proper dental care.

Acidity is another cause of teeth staining. Acidic foods and beverages, promote staining by eroding the dental enamel, this softens teeth making it easy for chromogens to latch on. A food compound known as tannins promotes staining by further boosting the chromogens’ ability to attach to the enamel.


What effect does acidity level of one cup of tea (mint), coffee (black), and soda (Coca-Cola) have on the discoloration of an egg?


If a one hollowed egg was placed in a cup of mint tea, another egg was placed in a cup of black coffee and a third egg was placed in Coca-Cola soda, then the egg that was placed in Coca-Cola soda will have the most discoloration after a five day period because the soda has a higher acidity level then the other two beverages.


Level of acidity in three beverages


Color of egg




Teeth Discoloration


Type of beverages, egg


  • Three eggs (hallowed)

  • Black Coffee

  • Mint Tea

  • Coca-Cola Soda

  • Three large plastic containers

  • Ph Strip


  1. Fill three separate large containers with black coffee, mint tea, and Coca-Cola

  2. Measure the ph value

  3. Put at least one hollowed-out eggshell into each container

  4. Every day, fish out the egg and observe the progress of discoloration.

  5. Take some photos of the gradual changes. On the day when there is a discoloration, note that day.

  6. Record results and compare the effects of the three liquids.

Number of Trials

One trial (last 5 days)

Type of Data

  1. Table

  2. Charts

  3. Graphs

Method of Analyzing

Write down changes that happen during the five day period


Freeman, David. Foods and Habits That Stain Your Teeth. 10 November 2009. Article. 10 September 2015

PC, Sophia. Does Tea Stain your Teeth? 02 April 2014. Article. 10 September 2015

Friedman, Michael. Dental Health and Tooth Discoloration. 05 June 2014. Article. 10 September 2015

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