Saliva pH and Enamel Remineralisation: Exploring a Potential Contributor to Dental Caries

Transcription

Tooth decay is one of the most prevalent diseases worldwide, occuring during the demineralisation phase. This happens when salivary pH drops below the threshold for remineralisation, allowing hydroxyapatite to disperse from the enamel.

This project inversitages how two biologically relevant pH levels (6.2 and 7.2) impacted remineralisation as a model for male and female resting salivary pH. Changes in mineral content and structure were observed through transillumination as well as mass.

Results showed that the 6.2, or female group, consistently remineralised less efficiently than the 7.2 group, demonstrating a limited ability to recover from acid exposure.

These finding highlight a potential contributor to disparities in dental health outcomes for both individuals and the female demographic.

This project resulted from  personal frustrations regarding the development of caries with few suggestions for mitigation or explanation from dental professionals, besides simply being predisposed to tooth decay. This led to a pursuit of research beyond dental care routines and toward the biological factors that might influence tooth decay.

Through research, it was found that resting salivary pH plays a critical role in the remineralisation cycle of enamel. Acidic saliva promotes mineral loss, weakening enamel over time. It was also discovered that females often have a lower resting salivary pH on average, particularly during hormonal fluctuations or pregnancy, and that women experience higher rates of dental caries compared to males. Most studies describe this trend without investigating how these pH differences directly affect enamel repair or suggesting mitigations.

This project aims to address that gap by isolating salivary pH as a single variable in a controlled, in-vitro model. Differences in pH representative of males and females influence the rate and effectiveness of enamel recovery were tested as well as various novel toothpaste treatments ability to account for these disparities. In the primary experiment it was hypothesized that a lower pH environment would reduce enamel recovery and increase overall mineral loss. In the secondary experiment, it was hypothesised that both novel treatments would be able to mitigate the limitations presented by lower salivary pH in enamel remineralisation.

Understanding this relationship could help explain why some individuals and demographics are more prone to caries and support more personalized, preventative dental care.

To answer the primary questions, background research was conducted using trusted scientific articles, dental journals, university sources, along with the consultation of professionals within the practical and research fields. Research focused on studies surrounding salivary composition, pH, and tooth decay.

Two controlled lab experiments were then designed using samples made from the isolated primary mineral that enamel is composed from. These samples were placed in special liquids that mimic the most vital elements found in the mouth. First, a demineralization solution was used to simulate how acids weaken teeth. Then, samples were moved into artificial saliva with two different pH levels: slightly acidic (6.2) and neutral (7.2). These represented typical differences seen in men and women. Conditions, including temperature, timing and solution ingredients, were controlled, ensuring they remained the same were kept the same like temperature, timing, and solution ingredients, so that pH was the only variable affecting the recovery of the respective groups. In the secondary experiment, toothpaste treatments were added to the samples throughout the experimental period to measure their effectiveness at supporting remineralisation.

To collect data, samples were examined in two ways. First, mass was recorded using an extremely precise scale to track mineral loss. Second, a high powered light was shone through the bottom of the samples to view changes in internal structure, since more damage causes light to scatter differently. These differences were captured on camera and then quantified through image analysis software. Multiple samples in each group were measured to make sure the results were consistent and reliable.

At the end of the experiment, it was found that pH does affect how well enamel can repair itself. Having lower resting salivary pH negatively impacts the remineralisation cycle, impairing enamel recovery and promoting more severe demineralisation compared to the neutral pH group.

Light-based imaging techniques illuminated that both groups of samples degraded in overall structural integrity as time progressed. However, the samples in the more acidic environment (pH 6.2) showed a steadier and more severe decline in mineral content. This suggests that even small increases in acidity can make it harder for enamel to recover during the repair cycle.

Interestingly, the group at neutral pH (7.2) sometimes showed more variation and larger short term changes. This may be because enamel repair is not perfectly stable and can fluctuate. Nonetheless, overall patterns clearly indicate that lower pH environments created less favorable conditions for long-term enamel recovery.

Mass measurements supported this trend, but the changes were very small. It was determined that early enamel damage may not always be accurately detectable by weight alone, and imaging methods can be more accurate  when tracking internal changes.

To analyze the results, percent changes of demineralised areas identified by the image analysis software were compared over time and looked at as complete trends instead of just single measurements. This allowed an understanding of how enamel changed throughout the full cycle, rather than at just one moment.

Conclusively, the results support the idea that lower resting salivary pH can reduce the effectiveness of enamel repair. This offers a potential explanation as to why some people and demographics may be more prone to caries, even when sufficient dental care is present.

Phase 2 results will be presented at the fair but are not included here due to ongoing data collection.

The conclusions of this project suggest that even small differences in salivary pH can significantly influence how well enamel repairs itself over time. The more acidic environment consistently created less stable conditions for remineralization and could not recover nearly as efficiently as the neutral group. This supports the idea that pH is not just a background factor, but an active driver in the balance between enamel loss and repair.

Early enamel damage is complex and inconsistently visible through mass measurements. The imaging results revealed significant patterns, highlighting the importance of using multiple that focus on structural variation when studying dental health. It was also found that rudimentary experimental models can be highly effective for dental research despite the limited equipment and budget.

These findings help explain why some people may be more prone to caries, despite following proper oral hygiene routines. If someone naturally has a lower salivary pH due to biological factors such as hormones, they may be at a disadvantage when it comes to enamel repair. This suggests that a “one-size-fits-all” approach to dental care may not be effective for everyone and more research is required to properly individualise preventative care.

This research could potentially support more personalized dental treatments, such as pH targeted products or preventative strategies. It also highlights the need for research into biological differences, especially those affecting women, in dental health. This project reinforces the importance of shifting dentistry toward prevention and understanding individual risk factors, rather than only treating problems after they occur.

If this project were to be continued, it would be optimal to increase the number of samples to improve reliability and reduce variation between trials. Testing a wider range of pH levels to better understand where enamel repair begins to significantly decline is also a priority. Alternatively, exploring the aspect of salivary flow rate is another possibility for this experimental model.

In the future, this research could expand into clinical studies to explore how individual biology affects caries risk and how dental care can become more personalized.

It is imperative to acknowledge the many experts inside and out of the field of dental research who have been indispensable in making this project possible. This includes Dr. Sana Umar of Kincardine Dentistry, who provided primary feedback; Victoria Hisko, M.Sc and Nisa Halsy of Vice President, Nuclear Equipment & Tooling who offered their time and professional advice in overcoming many technical issues; Dr Glasser, Dr. Chung, Dr. Duronio, Dr. Quinonez, Prof. Frank Lippert, and Prof. Elbert de Josselin de Jong, were also kind enough to lend their expertise in dental research; Prof. Paul Anderson of Queen Mary University of London also provided me with his scientific opinion and played a significant role in the development of the experimental model. Lastly, I would like to thank each member of the Bluewater Regional Science Fair team, including Diane Wall and Heather Christie, whose support, guidance and encouragement were both incredibly appreciated.

Disclaimer! This is not a complete list of every source used, but includes the most important to this project's development and concepts. A completed reference list will be provided at the fair.

References

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Arnold, W. H., Haase, A., Hacklaender, J., Gintner, Z., Bánóczy, J., & Gaengler, P. (2007). Effect of pH of amine fluoride-containing toothpastes on enamel remineralization in vitro. BMC Oral Health, 7(1). https://doi.org/10.1186/1472-6831-7-14

Clift, F. (2021). Artificial methods for the remineralization of hydroxyapatite in enamel. Materials Today Chemistry, 21, 100498. https://doi.org/10.1016/j.mtchem.2021.100498

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Nizami, M. Z. I., Xu, V. W., Yin, I. X., Chu, C.-H., & others. (2021). Metal and metal oxide nanoparticles in caries prevention: A review. ResearchGate. https://www.researchgate.net/figure/Mechanism-of-a-demineralisation-and-b-remineralisation-of-the-tooth-surface_fig1_357184589

Zhang, D., Wang, X., & Chen, J. (2022). Saliva: Properties and functions in food oral processing. Royal Society of Chemistry, 1–24. https://doi.org/10.1039/9781839160622-00001

UFO Themes. (2015). Dental caries. Pocket Dentistry. https://pocketdentistry.com/15-dental-caries/