Vaccinating Against Dental Cavities

According to the Global Burden of Disease Study in 2016, dental caries, more commonly known colloquially as dental cavities or "tooth decay", remains the most prevalent disease globally since both the 2006 and 1990 surveys. Interestingly, there is no disproportionate decline in this disease among the developed, industrialized countries, a trend that is more commonly observed for other diseases due to improvements in public health with the accessibility and advancements in healthcare.

To understand dental caries, it is important to understand how the disease develops. Unlike most tissues in humans, teeth are primarily comprised of an inorganic, highly mineralized material, yielding a relatively hard surface that is capable of withstanding the forces involved with chewing (Gutiérrez-Salazar & Reyes-Gasga, 2003). Most importantly, this mineral layer is not static, but rather exists in a fluctuating state of remineralization (minerals deposited onto the hard tissue layer) and demineralization (minerals dissolving into solution). Healthy humans who produce enough saliva have a high concentration of these ions in solution, which favors remineralization in teeth and maintains this hard tissue layer. However, if this balance is disrupted, the setting for the formation of dental caries is established. Acidic pH denotes an increase in the concentration of hydrogen ions that is dissolved in solution. At a chemical level, these hydrogen ions interact and bond with the crystal structure in teeth, favoring demineralization into solution and causing teeth to slowly dissolve and lose its hard mineral layer (Daws, 2003).

Acidic pH can be caused by multiple factors. The culprit is typically the consumption of foods high in processed sugars, a diet that is often readily available in industrialized countries. Bacteria, primarily Streptococcus mutans and lactobacilli, consume these sugars through a process called lactic acid fermentation, making energy to grow while producing an acidic oral environment. The addition of fluoride, a mineral, to our community water sources and to products such as toothpaste have contributed to a decline in the frequency of dental cavities in the United States (American Dental Association, 2018). The fluoride mineral, when introduced through these methods, binds and is incorporated into the tooth mineral structure; however, the fluoridated crystal structure is less vulnerable to demineralization and, unlike untreated teeth, can remain in its hard mineral form at more acidic environments before dissolving into solution.

While fluoridation has been a major achievement in public health for its reduction of dental caries, once someone does develop "tooth decay", it often requires drilling and restoration to halt the progression of the disease. However, because the pathology of dental caries is microbial in nature, researchers have begun exploring the idea of a "dental caries vaccine".

Vaccines work by producing acquired immunity in patients. The immune system is responsible for recognizing cells that are part of an organism from foreign invaders. Immunoglobulins are antibodies, proteins with an incredibly specific structure that allows them to bind to foreign invaders, and allow the body to detect these invaders. A specific form of the immunoglobulins, called secretory IgA, is found on a lot of mucous surfaces of our body, which are in contact with the outside environment and is often the first place where our bodies encounter unwanted foreign invaders (Woof & Kerr, 2006).

The dental caries vaccine works by having the body make enough of this secretory IgA in saliva (IgA is the most common form in saliva), and to make it specific to the Streptococcus mutans and lactobacilli bacteria (Shanmugam et al., 2013). If successful, the binding of this secretory IgA would make it very hard for the bacteria to stick to teeth and grow, meaning that it is less likely that they would set up shop inside a patient's mouth and produce enough acid to become pathogenic.

Dental caries has been shown to be correlated with an increase in heart-valve related issues, where the strains of Streptococcus mutans that are involved in forming dental caries have been found in heart valve and plaques (Nakano et al., 2006). While research is ongoing, many modern studies have shown that the maintenance of oral health is related to maintaining good health systemically. With the introduction of a dental caries vaccine into dentists' tools of care, one could see the potential to not only solve the issues of painful drilling and teeth extractions, but also for reducing more serious issues related to the onset of dental pathology.



References:

American Dental Association. (2018). Fluoridation Facts. Retrieved from https://www.google.com/books/edition/Fluoridation_Facts/_p1qDwAAQBAJ?hl=en&gbpv=1

Daws, C. (2003). What Is the Critical pH and Why Does a Tooth Dissolve in Acid? Journal of the Canadian Dental Association, 69(11), 722-724. 

GBD 2016 Disease and Injury Incidence and Prevalence Collaborators. Global, regional, and national incidence, prevalence, and years lived with disability for 328 diseases and injuries for 195 countries, 1990-2016: a systematic analysis for the Global Burden of Disease Study 2016. Lancet. 2017;390(10100):1211-1259.

Gutierrez-Salazar, M.D.P., Reyes-Gasga, J. (2003). Microhardness and chemical composition of human tooth. Materials Research, 6(3), http://dx.doi.org/10.1590/S1516-14392003000300011

Nakano, K., Inaba, H., Nomura, R., Nemoto, H., Takeda, M., Yoshioka, H., Matsue, H., Takahashi, T., Taniguchi, K., Amano, A., Takashi, O. (2006). Detection of Cariogenic Streptococcus mutans in Extirpated Heart valve and Atheromatous Plaque Specimens. Journal of Clinical Microbiology, 44(9), 3313-3317. doi: 10.1128/JCM.00377-06

Shanmugam, K.T., Masthan, K.M.K., Balachander, N., Sudha, J., Sarangarajan, R. (2013). Dental Caries Vaccine - A Possible Option?. Journal of Clinical and Diagnostic Research, 7(6), 1250-1253. doi:10.7860/JCDR/2013/5246.3053

Woof, J.M. and Kerr, M.A. (2006), The function of immunoglobulin A in immunity. J. Pathol., 208, 270-282. doi:10.1002/path.1877