For years, periodontitis has been recognized as a gum disease that damages the tissues supporting the teeth. But something happens far beyond the gumline—in the submandibular salivary glands—that has largely escaped attention. Research by drg. Nunuk Purwanti, M.Kes., Ph.D., from the Department of Biomedical Sciences, Faculty of Dentistry, Universitas Gadjah Mada (UGM), together with colleagues from the University of Jember and UGM, addressed a long-standing question: what happens to salivary mucus production as periodontitis develops? The findings, published in Dental Journal (Majalah Kedokteran Gigi) in June 2018, revealed a pattern that is far from simple—and that is precisely what makes it interesting.
When Bacteria Enter, the Body Responds
Periodontitis is more than just bleeding gums. The disease involves an anaerobic bacterium called Porphyromonas gingivalis (Pg), which produces a substance called lipopolysaccharide (LPS). This substance triggers inflammation in the periodontal tissues, which support the teeth and keep them in place.
Interestingly, the effects of this bacterium do not stop at the gums. Previous research has linked periodontitis to various systemic diseases, including atherosclerosis, diabetes, preterm birth, and chronic kidney disease. This means that what happens in the mouth can have effects throughout the body.
This is where saliva becomes important. Saliva is not merely a fluid that keeps the mouth moist. It contains proteins, carbohydrates, and minerals that function as antibacterial, antifungal, antiviral, and tissue-protective agents. One of its main components is mucus, a thick, gel-like substance that coats the entire surface of the oral cavity and is produced in large quantities by the submandibular glands, the salivary glands located beneath the lower jaw.
An Unexpected Pattern in the Submandibular Glands
To investigate how mucus production changes as periodontitis develops, the researchers used 32 eight-week-old male Wistar rats. Half of the rats were injected daily with Pg bacteria in the mesial area of the upper first molar, while the other half received a placebo solution. Samples were collected on days 7, 14, 21, and 28 after injection and analyzed using a special staining technique called periodic acid-Schiff (PAS) to detect the presence of mucus.
The results were surprising. Mucus expression in the submandibular glands increased significantly on days 7, 14, and 21, before declining on day 28, when the periodontitis had become more severe. Mucus expression reached its peak on day 21.
At the same time, the thickness of the junctional epithelium (JE), the epithelial layer that serves as the first line of defense for periodontal tissues, continued to decrease over time. Thinning was first detected on day 14 and reached its lowest point on day 28. The thinner the JE became, the easier it was for bacterial products to penetrate deeper tissues.
Mucus: A Protector with Two Faces
These findings provide a new understanding of mucus, whose function is apparently not simply beneficial or harmful. When a bacterial infection begins, epithelial cells and goblet cells produce more mucus as a defense mechanism, preventing bacteria from colonizing further. This explains the increase in mucus expression from days 7 to 21.
On the other hand, mucus can also serve as a “stepping stone” for bacteria. Mucus facilitates bacterial attachment to epithelial surfaces. Thus, when mucus production increases, pathogenic bacteria may also benefit. Another study cited in the research reported that adolescents with high levels of dental caries had increased levels of MUC1 and MUC5B, while MUC7 levels decreased. This further supports the idea that changes in mucus composition and concentration may serve as indicators of oral health status.
The decline in mucus expression on day 28, when periodontitis had become more severe, likely involved signaling pathways different from those operating during the earlier stages. The researchers speculated that LPS from Pg activates the cholinergic system through NOS (nitric oxide synthase), which subsequently increases calcium concentrations in submandibular gland acinar cells and stimulates mucus secretion. However, as inflammation becomes more severe, this pathway may shift or become disrupted.
“The results of this study showed that mucus expression in the submandibular glands varied during the induction of periodontitis. Expression gradually increased with the duration of induction, reached its peak on day 21, and decreased on day 28.”
Paving the Way for New Biomarkers
The implications of this research extend beyond the laboratory rat model. If salivary mucus responds dynamically to the progression of periodontitis, mucus levels could potentially be developed as a non-invasive biomarker for diagnosing and monitoring periodontal therapy. Patients may no longer need complicated procedures to determine the severity of their periodontal disease. A saliva sample might be sufficient.
The study also raises an important follow-up question: which signaling pathways are specifically involved when mucus expression declines during the more advanced stages of periodontitis? Answering this question could open opportunities for new therapies that harness the natural defense system of saliva.
Saliva has often been regarded as something that is simply there. The research by drg. Nunuk Purwanti, M.Kes., Ph.D., and her team reminds us that behind that clear fluid lies a sophisticated protective system that works continuously, responds to threats, and contains information that we have yet to fully decipher.
Authors: Achmad Zam Zam Aghasy, DDS, M.Kes.; Hazra Alifia Muharam
Photo: Pexels
Sumber DOI: https://doi.org/10.20473/j.djmkg.v51.i2.p52–56