Radhika Bajaj, Year 2 Research.
Scientific research on teeth enamel is vital for improving dental care. However, using tooth extractions in studies carries issues regarding costs, convenience, safety, and consent. This experiment focuses on finding a substitution for teeth; it investigates the suitability of eggshells to demonstrate the effects of sugar and pH on tooth enamel demineralization as both eggshells and tooth enamel are composed of a calcium compound. Hollow eggshells were placed in substances with different pH levels and sugar concentrations. Thereafter, the intensity of light passing through them and their mass was measured periodically. A greater pH level and lower sugar concentration allowed greater light to pass through the eggshells, meaning a significant amount of decay. Furthermore, relatively, no significant change in mass was noted in both sets of data. This contradicts current research which demonstrates that acids are a causing factor of dental erosion, and sugar fosters dental caries.
Our teeth play an important role in our daily life; they are essential to our process of digestion as the oral cavity is the primary contact with food items and beverages. Furthermore, our tooth enamel, the hard outer layer of teeth, provides a protection and barrier for our teeth (Gil-Bona and Bidlack, 2020). It is composed of crisscrossing mineral rods bonded by proteins (Pro and Barthelat, 2019). Current studies illustrate the growing importance and demand of research related to tooth enamel. For example, one study discovered that there was a reduction of tooth enamel decay by 37% in12-year-old children in wards with water fluoridation (Jones and Worthington, 2000). In turn, the decay of tooth enamel is accompanied by complications such as tooth pain or sensitivity.
Research around tooth enamel is necessary for proper health. Yet, using actual teeth in research raises problems surrounding costs, convenience, accessibility, safety, and consent. For example, using extracted teeth exposes people to bloodborne pathogens (Berg, 2016). The use of extracted teeth carries difficulty and concerns about proper sterilization; autoclave sterilization and storage in 10% formalin solutions are common methods in today’s date for cleansing, however, they hold their own disadvantages (Nawrocka and Lukomska-Szymanska, 2019). In addition, another issue is needing consent from patients to use their extracted teeth for scientific research (Skene and Nisselle, 2002). This makes finding a substitution for teeth enamel (or teeth as a whole) in research a critical subject. This experiment focusses on the suitability of eggshells as a proxy for teeth. In specific, it investigates whether eggshells are able to demonstrate the effects of sugar and pH on tooth enamel demineralization. Eggshells could be a possible proxy for tooth enamel as they resemble each other in their chemical composition; they both are composed of calcium compounds. Tooth enamel consists of calcium-deficient carbonated hydroxyapatite (Featherstone and Lussi, 2006) whereas the mineral component of chicken eggshell consists of calcium carbonate (Sakai et. al, 2017).
Using eggshells as a model for tooth enamel, they will be placed in substances and ingredients of varying pH levels and sugar concentrations. After certain time periods, they will be taken out of the beverages to record any change in measurements, such as the intensity of light they allow to pass through or their mass. Eggshells will be used to test, specifically, their effectiveness in representing the effect of sugar and pH on teeth enamel because of former studies conducted in the area. Current research demonstrates that acids are a causing factor of dental erosion, as well as sugar causes dental caries (Moynihan and Petersen, 2004). The execution of this experiment is critical to find an appropriate substitution for teeth in scientific research, and as a consequence, for improving dental care.
Materials and Methods
To prepare the eggshells for the experiment, a push pin was used to poke a hole through the bottom of 11 eggs (Born 3 Eggs); the egg white and yolk were allowed to drain out so that a hollow egg remained (Figure 1). To test the effect of varying sugar concentrations, 20g, 40g, 60g, and 80g of granulated sugar (Rogers) was poured in 500ml of warm water and stirred in a container until it was fully dissolved. To test the effect of substances with varying pH levels, 500ml of Coca-Cola (Coca-Cola Original), white vinegar (Heinz), and Canola Oil (Sunfrie) was poured into separate containers. In another container, 50g of Baking Soda (Arm & Hammer) was dissolved into 450ml of water. Additionally, 15g of ground coffee (Salt Spring Metta Espresso) was boiled in 550ml of water and strained into a container. 500ml of water with 0g of sugar was also added in a container to be used in both experiments to test for both the effect of varying sugar concentrations and pH levels. Containers were labeled according to the substance they held (Table 1 shows the list of substances with different pH levels and Table 2 shows the list of substances with different sugar concentrations). Using pH strips the pH levels of Coca-Cola, vinegar, coffee, cooking oil, water, and dissolved baking soda were measured.
Figure 1: Hollowed eggshell
Table 1: Directory for Substances with varying pH Levels
Table 2: Directory for substances with varying sugar concentrations
The light intensity measuring device (Figure 2) was set up in a shoebox with black construction paper taped on all faces of the inside of the box. A lux meter (Pyle Digital Illumination Meter) was taped on one end of the box and a flashlight (Coast Inspection Light) on the other end so that the front of both the light and lux meter were separated by 11.0 cm. A white crayon was used to mark the spot where the eggshells would be placed which was 8.5 cm away from the light source. Measurements were taken with the lid of the shoebox closed.
Figure 2: Luxmeter setup for measuring the intensity of light
The mass of the eggshells was recorded along with the amount of light (lux) passing through them. They were then submerged in the appropriate substances. For every three days over the course of three weeks, the eggshells were taken out to record the mass of the eggshells and the intensity of light passing through; any substance which had filled them while being drowned was allowed to drain out. Qualitative changes (such as in texture or appearance) were also noted. An eggshell that wasn’t dipped in any substance was used for control and the average of three separate measurements was taken.This experiment was repeated a second time and an additional drink, 500 ml Gatorade (Frost Glacier Cherry), was added in. This was due to the staining observed with coloured drinks like Coca-Cola and coffee which prevented any light from passing through and affected the accuracy of the measurements; the Gatorade was a clear drink with a lower pH close to that of Coca-Cola and coffee.
The relationship between the intensity of light passing through eggshells placed in substances of varying pH levels for the first trial is shown in Table 3 and for the second trial is shown in Table 4. Figure 3 (trial 1) and Figure 4 (trial 2) illustrate an overall increase in the amount of light passing through for greater pH levels.
Table 3: Data for Intensity of Light Through Eggshells Placed in Substances of Different pH Levels Over Days (Trial 1).
Table 4: Data for Intensity of Light Through Eggshells Placed in Substances of Different pH’s
Figure 3: Intensity of Light Through Eggshells Placed in Substances of Different pH Levels Over Days (Trial 1). Vinegar (pH 3), then water (pH 7) allowed the greatest amount of light to pass through while Coca-Cola (pH 3), cooking oil (pH 6), dissolved baking soda (pH 9), and coffee (pH 6), respectively caused the most decrease in the amount of light passing through.
Figure 4: Intensity of Light Through Eggshells Placed in Substances of Different pH Levels Over Days (Trial 2). Vinegar, then water caused the greatest increase in lux again, and Gatorade (pH 4), cooking oil, dissolved baking soda, and Coca-Cola caused the greatest decrease in lux, correspondingly.
The relationship between the mass of the eggshells and the different pH levels of substances were recorded in Table 5 (trial 1) and Table 6 (trial 2) which show that the eggshells either maintained a constant mass, returned to their original mass, or changed in mass by an insignificant amount with the exception of the one submerged in Vinegar.
Table 5: DataforMass of Eggshells Placed in Substances of Different pH Levels Over Days (Trial 1). The eggshells either maintained a constant mass or returned to their original mass with the exception of the one submerged in Vinegar.
Table 6: DataforMass of Eggshells Placed in Substances of Different pH Levels Over Days (Trial 2). The eggshells in coffee and baking soda increased by 1g and the eggshells in Gatorade and Cooking oil increased by 2g. The mass of all other eggshells remained the same except for the one in vinegar.
The measurements for the intensity of light passing through eggshells placed in substances of varying sugar concentrations were noted in Table 7 for the first trial and in Table 8 for the second trial. While testing the impact of different sugar concentrations, Figure 5 (trial 1) and Figure 6 (trial 2) portray that as the molarity of the solution increased the intensity of light passing through the eggshells increased.
Table 7: Data forIntensity of Light Through Eggshells Placed in Varying Sugar Concentrations Over Days (Trial 1)
Table 8: Data forIntensity of Light Through Eggshells Placed in Varying Sugar Concentrations Over Days (Trial 2)
Figure 5: Intensity of Light Through Eggshells Placed in Varying Sugar Concentrations Over Days (Trial 1). As the molarity of the solution increased, the intensity of light passing through the eggshells increased.
Figure 6: Intensity of Light Through Eggshells Placed in Varying Sugar Concentrations Over Days (Trial 2). 0M, 0.12M, and 0.23M of sugar, caused the greatest increase in the amount of lux, correspondingly, while the eggshell subjected to the substance with 0.47M followed by 0.35M of the solution caused the greatest decrease in lux.
The mass of the eggshells remained constant in trial 1 (Table 9) and had small changes in trial 2 (Table 10).
Table 9: Data forMass of Eggshells Placed in Varying Sugar Concentrations Over Days (Trial 1). The mass of the eggshells remained constant.
Table 10: Data forMass of Eggshells Placed in Varying Sugar Concentrations Over Days (Trial 2). The mass of the eggshells remained constant except for the ones with OM and 0.23M of sugar which increased the mass by 1g.
An important observation noted during the trials was that the eggshell placed in Cocacola and coffee had been stained so that it was a dark colour (Figure 7). The eggshell in vinegar had completely disintegrated, leaving only the internal membrane (Figure 7). The eggshells in substances of different pH levels and sugar concentrations both had a slimy surface covering the eggshell after being placed in the fluids (Figure 7, Figure 8, Figure 9).
Figure 7 Qualitative Analysis of Eggshells Placed in Substances of Varying pH levels
Figure 8 Qualitative Analysis of Eggshell Placed in Water (pH 7, 0M)
Figure 9 Qualitative Analysis of Eggshell Placed in Substances of Varying Sugar Concentrations
In general, greater pH levels resulted in more light passing through due to greater decay. However, this could have been affected by major sources such as the fact that Coca-Cola and coffee stained the eggshell and obstructed any light from shining through, or the extra film of slime covering the eggshells could’ve hindered any light from passing through the eggshells or caused slight changes in mass. There was a relatively insignificant change in mass with the exception of vinegar. The shell dipped in vinegar disintegrated, leaving only the membrane behind, and allowing all the light to pass through and a significant decrease in mass. This can be explained by the following chemical reaction that takes place: CaCO3+ 2H+ -> Ca+2 + H2O +CO2 (Chiaet, 2016).
The greater the sugar concentration the less decay it caused in the eggshell by causing a lower intensity of light to pass through. This can be seen through both trials where 0M, 0.23M, 0.35M, and 0.47M of sugar, correspondingly, resulted in the greatest increase in the amount of light passing through. Furthermore, there was an insignificant change in the mass of eggshells. However, these results could have been affected by the observation that an extra film of the substances adhered to the shells.
Current research shows that acids are a causing factor of dental erosion, as well as sugar causes dental caries (Moynihan and Petersen, 2004) which was contradictory to the findings in this experiment. This incongruity between results indicated that the eggshells weren’t able to effectively model the effects of sugar and pH on tooth enamel demineralization.
More research would be needed in this area to confirm the results because of several sources of error. The limitations of this experiment included that the fact that the substances used to test the relationship between the pH of substances could contain other ingredients and have a different chemical composition which could affect the results in other ways. In addition, instrumental errors such as the scale and lux meter could have impacted the measurements. For example, the light source was noticed to grow dimmer by the end of the second trial. The staining of the eggshells in Coca-Cola and Coffee also created a discrepancy in the results as they didn’t let any light pass through by the end of both trials. Lastly, there was a slimy layer noticed on the eggshells after being placed in the substances which could have increased the mass of the eggshells and hindered any light to pass through.
If the experiment was to be done again, one could incorporate only clear drinks to remove the confounding variable of staining and include a washing step before taking measurements to avoid the effect of an extra layer of substances around the shell. Future areas of studies could include using eggshells as a model for tooth enamel testing the effects of other chemicals such as sodium or fluoride on eggshells to model tooth enamel decay.
Berg, Joel. “Safe Handling of Extracted Teeth.” UW School of Dentistry, UW School of Dentistry, 2 July 2019, dental.washington.edu/policies/clinic-policy-manual/safe-handling-extracted-teeth/.
Chiaet, Julianne, and Daniel Duan “The Chemistry Behind the Egg Shell and Vinegar Experment: Videos.” Labroots, Labroots, 15 May 2016, https://www.labroots.com/trending/videos/9787/the-chemistry-behind-egg-shell-vinegar-experiment-1
Featherstone, J D B, and Adrian Lussi. “Understanding the chemistry of dental erosion.” Monographs in oral science vol. 20 (2006): 66-76. doi:10.1159/000093351
Gil-Bona, Ana, and Felicitas B Bidlack. “Tooth Enamel and its Dynamic Protein Matrix.” International journal of molecular sciences vol. 21,12 4458. 23 Jun. 2020, doi:10.3390/ijms21124458
Jones, C.M., and H. Worthington. “Water Fluoridation, Poverty and Tooth Decay in 12-Year-Old Children.” Journal of Dentistry, vol. 28 (2000): 389–393. doi:10.1016/s0300-5712(00)00005-1.
Moynihan, Paula, and Poul Erik Petersen. “Diet, nutrition and the prevention of dental diseases.” Public health nutrition vol. 7,1A (2004): 201-26. doi:10.1079/phn2003589
Nawrocka, Agnieszka, and Monika Łukomska-Szymańska. “Extracted human teeth and their utility in dental research. Recommendations on proper preservation: A literature review.” Dental and medical problems vol. 56,2 (2019): 185-190. doi:10.17219/dmp/105252
Pro, J William, and Francois Barthelat. “Discrete element models of tooth enamel, a complex three-dimensional biological composite.” Acta biomaterialia vol. 94 (2019): 536-552. doi:10.1016/j.actbio.2019.04.058
Sakai, Seigo et al. “Effects of Eggshell Calcium Supplementation on Bone Mass in Postmenopausal Vietnamese Women.” Journal of nutritional science and vitaminology vol. 63,2 (2017): 120-124. doi:10.3177/jnsv.63.120
Skene, Loane, and Paul Nisselle. “Use of Extracted Teeth in Research.” Medicine and the Law, vol. 3 (2002): 55–57.
“Tooth Enamel: Loss, Erosion, and Repair” Crest, Crest, 25 Mar. 2021, https://crest.com/en-us/oral-health/conditions/tooth-enamel/tooth-enamel-loss-erosion-repair