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In-vitro gravimetric analysis of the effect of pH on enamel erosion using acidic beverages

Yezi Cho, Serene Elmusharaf

American Community School of Abu Dhabi

This experiment measures the effect of pH by experimenting with different acidic beverages on enamel erosion by experimenting with premolars.

The premolars were extracted for orthodontic reasons and used within two weeks post-extraction. Prior to the experiment, the mass of the premolars and pH of six types of common beverages (water, apple juice, orange juice, lemon juice, Pepsi, and Coca-Cola) were measured. The experiment was conducted at room temperature for ten days, and the premolars were dried and weighed twice, at five-day intervals.

Figure 1. Experimental Set-up

Below are the results of leaving each premolar in a beverage for ten days, lightly washed and dried.

Figure 2. Natural Water (pH = 5.66)
Figure 3. Natural Water (pH = 5.66)

Figure 4. Orange Juice (pH = 3.80)
Figure 5. Orange Juice (pH = 3.80)

Figure 6. Apple Juice (pH = 4.03)
Figure 7. Apple Juice (pH = 4.03)

Figure 8. Lemon Juice (pH = 2.50)
Figure 9. Lemon Juice (pH = 2.50)

Figure 10. Coca-Cola (pH = 2.52)
Figure 11. Coca-Cola (pH = 2.52)

Figure 12. Pepsi (pH = 2.65)
Figure 13. Pepsi (pH = 2.65)

Qualitative Observations

The colors of the surface of the most premolars noticeably changed:

  • In natural water, the color of the teeth remained the same.

  • In orange and apple juice, the teeth became yellow-orange and developed a white cast.

  • In 100% lemon juice, the teeth developed a significant white cast.

  • In Coca-Cola and Pepsi, the teeth were browned at the top of the pre-molars and developed a strong stain.

  • In Coca-Cola, the browning was significant on the bottom half of the tooth (below a distinct line) while in Pepsi the tooth browned evenly. This observation may be due to the integrity of each individual tooth.

Quantitative Observations:

The mass percent loss percentage (%) was calculated as the following:

  • Water: 0.50

  • Orange juice: 2.72

  • Apple juice: 1.18

  • Lemon juice: 8.95

  • Coca-Cola: 2.63

  • Pepsi: 1.78.

Below is the acidity of the solutions from most acidic to most basic:

Lemon Juice (pH 2.50) > Coca-Cola (pH 2.52) > Pepsi (pH 2.65) > Orange Juice (pH 3.80) > Apple Juice (pH 4.03) > Water (pH5.66)

While there is a general correlation between acidity and percent loss of mass, it is notable that the type of beverage influenced the percent loss greater than the pH level. This is due to the different types of acids, including but not limited to citric acid, phosphoric acid, carbonic acid, and malic acid that the beverages contain.

In this study, the structure, surface area, and individual differences of each premolar were not uncontrollable variables. Further studies investigating the effect of acid type, titratable acidity, and using more kinds of beverages are needed for deeper analysis. In addition, the actual detrimental effects of acidic beverages differ in an actual human oral environment, where the enamel is constantly remineralized and salivary functions cannot be neglected.

As for ethical and safety concerns, the teeth were extracted by a medical professional for orthodontic reasons. After the experiment was concluded, the teeth and all scientific apparatus used were either thoroughly sterilized or disposed of in medical waste containers.

Special thanks to Ariane Spruit, Emily Shin, Eshaal Aziz, Marium Devji, Sua Kim, and Jonah White, who engaged in the experiment above.


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