Brushing Teeth Improperly Linked to Increased Cancer Risk

Author: Jiang Yongyuan, Master's degree in Internal Medicine from the Third Military Medical University. Reviewer: Pan Zhanhe, Chief Physician of the Oncology Department at Zhongshan Hospital Affiliated to Xiamen University, Vice Chairman of the Oncology Popular Science Professional Committee of the Fujian Anti-Cancer Association. Planning: He Yumeng. Editor: He Yuming. Proofreading: Xu Lai, Zhang Linlin. Source: Popular Science China WeChat Official Account. The cover image of this article and the images within are sourced from a licensed image library. Reproducing this content may lead to copyright disputes.

Who could have thought that failing to brush one's teeth properly could actually facilitate the spread of cancer cells? In December 2025, a research team from Wuhan University published a noteworthy study, revealing that a common periodontal pathogen—Porphyromonas gingivalis—may influence the metastatic process of esophageal squamous cell carcinoma by releasing tiny vesicles. In simple terms, this study uncovers a potential biological mechanism: bacterial products originating from the mouth may enable a more efficient spread of cancer cells via a series of intracellular signaling changes.

However, before succumbing to anxiety, it is crucial to place these findings back into a scientific context, allowing for a clear understanding of what these studies convey and what they do not. The evidence linking "oral bacteria" to "tumor metastasis" continues to grow. A study from Wuhan University first discovered that the abundance of Porphyromonas gingivalis in esophageal squamous cell carcinoma tissues is markedly higher than in adjacent normal tissues. Additionally, greater mean abundances of this bacterium correspond to later stages of cancer, increased lymph node metastases, and shorter survival times for patients.

Further cell and animal experiments have established that the extracellular vesicles released by this bacterium can enhance the migration and invasion abilities of tumor cells, thereby promoting metastasis. This is not an isolated discovery. Another study utilizing transcriptome data indicated that infection with Porphyromonas gingivalis can significantly alter the expression profile of inflammation-related genes in esophageal squamous cell carcinoma. Patients with a pronounced infection-related gene profile exhibited shorter overall survival times.

Based on the expression levels of genes associated with Porphyromonas gingivalis infection, researchers classified patients into groups of high and low expression levels, allowing for a comparison of the overall survival rates of the two cohorts. These findings support the hypothesis at the molecular level that chronic oral infections may modify the tumor microenvironment through inflammation and signaling pathways, ultimately influencing disease progression.

Epidemiological studies corroborate this conclusion. A retrospective analysis comparing 60 patients with esophageal squamous cell carcinoma to 178 healthy controls found that individuals experiencing more severe periodontal attachment loss and a greater number of missing teeth were more frequently observed among the esophageal squamous cell carcinoma patients.

Furthermore, among patients who underwent esophagectomy for cancer, those with preoperative moderate to severe periodontal disease had significantly lower long-term survival compared to those with healthy periodontal conditions. Similar correlations have been seen in other regions and across various gastrointestinal tumors. A large case-control study in the Kashmir region revealed that patients with esophageal squamous cell carcinoma were significantly less prevalent among those who occasionally practiced tooth cleaning, compared to those who never did.

Additionally, a nested case-control study in Southwest China indicated that the prevalence of esophageal and colorectal cancer among individuals suffering from periodontitis was about twice that of their periodontally healthy counterparts. In certain tumor types, this was also associated with a higher incidence of metastasis.

It is important to note that correlation does not equate to causation. How should we interpret these findings? Observing these results, many individuals instinctively ponder: Does having periodontal disease guarantee the development of gastrointestinal tumors? The answer is no.

Current research primarily suggests correlations, rather than definitive causal connections. Periodontal diseases frequently coexist with factors such as smoking, alcohol consumption, dietary habits, and socioeconomic status—each being significant contributors to gastrointestinal tumors. Moreover, even when adjustments are made in statistical analyses, it remains impossible to entirely isolate the impacts of all confounding factors. Compared to individuals who neglect oral hygiene, the proportion of esophageal squamous cell carcinoma cases is significantly reduced among those who clean their teeth at least occasionally.

Furthermore, the progression from mechanistic studies to practical real-world applications remains lengthy. The investigations conducted at Wuhan University provide us with a coherent molecular explanatory framework; however, this does not imply that Porphyromonas gingivalis will necessarily incite tumorigenesis via the same pathway among the general population. In many cases, it may merely play a role within a prolonged inflammatory network rather than acting as a singular switch.

As such, a more rational interpretation is that periodontal disease may serve as a contributing risk factor for the onset and progression of gastrointestinal tumors rather than being a definitive cause. While we should not instigate panic, we also must not neglect the significance of these findings.

What can regular individuals do? These studies remind us that oral health is intrinsically linked to other bodily systems and that a prolonged inflammatory state can significantly impact overall health in diverse ways.

For most people, this does not imply necessitating frequent cancer screenings or correlating every dental issue with cancer. Instead, what holds true importance is the integration of oral health into the holistic management of one’s overall health.

Routine brushing, use of dental floss, and minimizing long-term experiences of gum bleeding and periodontal infections can notably enhance quality of life and potentially mitigate the burden of chronic inflammation in the long run.

What is most meaningful is the incorporation of oral health into daily health management practices.

For those already diagnosed with gastrointestinal tumors, these studies provide significant clinical insights. Multiple investigations have demonstrated that implementing standardized oral assessments and treatments prior to surgery or therapy correlates with improved prognoses.

However, this does not insinuate that "addressing oral health will cure cancer"; instead, the objective is to alleviate the burden of infection and inflammation to allow the body to be in a more advantageous state during treatment.

The true value of science is manifested in aiding us to make informed choices. The relationship between periodontal disease and gastrointestinal tumors is gradually being elucidated; our actions, however, should remain rooted in the most fundamental and reliable behaviors—viewing our daily oral hygiene as a long-term health investment.

References

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Haque T, Nabhan AB, Akhter F, et al. The analysis of periodontal diseases and squamous cell esophageal cancer: a retrospective study. Saudi Dent J. 2023;35:714–719.

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Luo T, Li J, Pu K, Yang G. Association between periodontitis and the risk and prognosis of gastrointestinal cancer: evidence from a nested case-control study in Southwest China. Eur J Med Res. 2025;30:225.