By Dr. Mohamed Tarek Galal
The connection between the oral cavity and the digestive tract is undeniable. There have been countless studies suggesting that the two cavities are closely related, and what happens in one of them can quickly affect the other. However, most of the studies suggest that a problem with the oral cavity can adversely affect the gut, the simplest example being that an edentulous person would have trouble chewing the food, and thus would often suffer from indigestion, but what if the other way around has an effect as well? What if the gut bacteria can have an effect not only on the bacteria of the mouth but on the alveolar bone as well?
The Connection Between Gut Flora and the Bones
The bacteria of the gut have always been connected to various problems that can happen inside the body, particularly within the bones. Gut microbiota has been proven to increase the rate of turnover for the bones by modulating the immune system and causing the release of a large amount of inflammatory mediators, thereby disrupting the balance between bone-forming cells (Osteoblasts) and bone degrading cells (Osteoclasts).
These bacteria have also been associated with some well-known bone diseases such as Osteoporosis, Osteopenia, as well as the most destructive disease of the joints, Osteoarthritis. The mechanism behind the association is still under a lot of research, but a clear change in the number of gut bacteria and the amount of their metabolites is evident in most of these patients.
Recent Discoveries That Formed a Connection Between Gut Flora and Oral Bone Health
Periodontitis is one of the most common conditions to affect the mouth. The mechanism behind its onset has always been connected to the oral microbiota. However, some other conditions of the body may alter its intensity and pathogenesis, such as obesity and diabetes.
There was always the knowledge that gut bacteria are also involved with periodontitis, but a clear and direct connection has never been established, until recently. One of the most recent studies performed by an association of dentists and physicians in MUSC found a most fascinating connection directly between gut flora and the alveolar bone. The study involved the introduction of a certain bacteria known as segmented filamentous bacteria (SFB) - a threadlike bacteria that is normally found in the healthy gut flora of human beings and some animals – into the gut of mice raised in a completely germ-free condition to witness their effect on the oral cavity as a whole, and the alveolar bone in particular.
The results of that experiment were fascinating, to say the least. The alveolar bone of the subject mice showed significant degradation around the teeth six weeks after the bacteria were introduced.
With further research, the mechanism behind such change began to be revealed. SFB seems to trigger an immune response inside the bone marrow (including the alveolar bone) leading to the release of Tumor Necrosis Factor (TNF). TNF is a known inflammatory mediator that leads to the disruption in the Osteoblast\Osteoclast balance, resulting in a higher amount of Osteoclasts, which could explain the quick bone degradation.
What This Evidence Suggests
Some inflammatory conditions affecting the bowel – particularly Crohn’s disease – have always been associated with periodontal conditions and alveolar bone loss, but no one really understood why this connection exists. This recent study may help to shed the light on the matter. SFB is found in abundance in all inflammatory bowel conditions, which denotes that this particular form of bacteria may be responsible for the inflammatory mediators – TNF – Osteoblast\Osteoclast imbalance cascade, ultimately leading to alveolar bone loss.
In addition, this study also suggests that if the gut flora can be controlled or adjusted, it would have a positive effect on the bones in general and the alveolar bone in particular. The gut flora – much like the oral flora – is a delicate balance between harmful and useful bacteria and other microorganisms, effectively canceling each other out under normal conditions. Prebiotics – which is a group of chemical ingredients present in certain foods such as garlic, chickpeas, broccoli, and some types of fish – have been shown to have the ability to alter the gut microbiota, and have been suggested to be used in some other conditions affecting the bones.
Every day science and research reveal new information and help us to better understand the human body and how every part of it is connected to the other. The connection between the gut cavity and the oral cavity has been well-established in the past, but who knew that such a specific connection between a specific type of bacteria and the alveolar bone actually existed?
- Algate, K., Haynes, D. R., Bartold, P. M., Crotti, T. N., & Cantley, M. D. (2016). The effects of tumour necrosis factor-α on bone cells involved in periodontal alveolar bone loss; osteoclasts, osteoblasts and osteocytes. Journal of periodontal research, 51(5), 549–566. https://doi.org/10.1111/jre.12339
- Carly A.R. Zanatta, BSc, ; Wendy E. Ward, BArts&Sci, MSc, PhD: Prebiotics: Not Only For Gut Health?
[Available online: https://www.oralhealthgroup.com/features/prebiotics-not-only-for-gut-health/]
- Hathaway-Schrader, J. D., Carson, M. D., Gerasco, J. E., Warner, A. J., Swanson, B. A., Aguirre, J. I., Westwater, C., Liu, B., & Novince, C. M. (2022). Commensal gut bacterium critically regulates alveolar bone homeostasis. Laboratory investigation; a journal of technical methods and pathology, 102(4), 363–375. https://doi.org/10.1038/s41374-021-00697-0
- Jia, X., Yang, R., Li, J., Zhao, L., Zhou, X., & Xu, X. (2021). Gut-Bone Axis: A Non-Negligible Contributor to Periodontitis. Frontiers in cellular and infection microbiology, 11, 752708. https://doi.org/10.3389/fcimb.2021.752708
Author: Dr. Mohamed Tarek Galal BDS, MFDS RCSEd, Member of AACD is a practicing dentist, the founder and owner of Confidental clinic in Cairo, Egypt. He graduated from the faculty of dentistry, Ain Shams University, the highest-rated dental school in Egypt, obtaining his Bachelor of Dental Surgery (BDS) in 2010 and has been practicing ever since. He acquired a postgraduate diploma of Oral Surgery in 2013 from the same university. In 2014, He acquired the membership of faculty of dental surgery (MFDS) from the Royal College of Surgeons of Edinburgh (RCSEd), one of the highest honors in professional dentistry. In 2016, He became a member of the American Academy of Cosmetic Dentistry (AACD), the highest recognized institution in the world pertaining to cosmetic dentistry and beauty. He has also been in the writing and research business for over 5 years and has written more than 700 pieces on many different medical and dental topics for various websites, blogs and medical pages.