Since the COVID-19 pandemic began, researchers have sought to identify the risk factors that contribute to infection, serious complications and death. Now, evidence is emerging to suggest that periodontal disease may be one such factor. Here, we discuss the latest findings and what they mean for dentists and patients.
Researchers from the UK’s University of Leeds conducted a study with 13,253 participants, 1,616 of whom had tested positive for COVID-19. They found insufficient evidence to link periodontal disease with increased risk of COVID-19, but in those who had been infected and had self-reported symptoms of periodontal disease, they observed a significantly higher mortality rate. They concluded that periodontal disease may be associated with the severity of COVID-19.
In a second study, researchers in Qatar looked at the dental and medical records of 568 patients who had tested positive for COVID-19, 258 of whom also presented with periodontitis. They found that the risk for severe COVID-19 complications, including ICU admission, ventilation and death, was significantly higher in those with moderate or severe periodontitis than in those with mild or no periodontitis.
What do the findings mean? In the University of Leeds study, the authors cited prior research showing dominant bacterial, viral and fungal co-infections in approximately 94% of COVID-19 cases. These same pathogens, they note, have also been identified in the oral biofilms associated with periodontal disease. Their findings support the suggestion that the oral microbiome and microbial load might be associated with severe COVID-19 complications.
In the Qatari study, the authors pointed to multiple studies showing that COVID-19 mortality was associated with higher blood levels of inflammatory markers like C-reactive protein and white blood cells. They noted that their COVID-positive participants with periodontitis showed significantly higher levels of inflammatory markers than those without periodontitis, suggesting that systemic inflammation may play a role in worsening disease outcomes.
The authors discussed several hypotheses that could potentially explain the strong connection:
- The oral cavity, and periodontal pockets in particular, could act as a viral reservoir and increase the individual’s viral load.
- The aspiration of periodontopathic bacteria could elevate inflammatory cytokines and SARS-CoV-2 receptor expression in the lower respiratory tract. This may contribute to the onset of the so-called “cytokine storm,” an aggressive immune response associated with severe COVID-19 complications and death.
- Severe periodontitis is associated with a strong lymphocyte response, which could also exacerbate the cytokine storm in COVID-19 patients.
Both studies show a strong correlation between periodontitis and the risk of COVID-19 complications and mortality. However, neither study establishes causality. We cannot say conclusively whether periodontal disease itself is responsible for the increased risk, or a third factor is driving both.
It is known that treating periodontitis improves levels of inflammatory markers, so if the hypothesized links between systemic inflammation and severe COVID-19 complications are correct, then periodontal therapy could theoretically improve COVID-19 outcomes. However, at this moment, those hypotheses remain unproven.
A key limitation affecting the UK study is the use of self-reported surrogates for periodontal disease (bleeding gums, sore gums and loose teeth). Self-reporting of those measures is vulnerable to bias, underestimation and error. On the other hand, the Qatari study used objective measures of periodontal disease, reaching a similar conclusion, however this study was a cross-sectional review of charts.
The UK research team identified further limitations, such as delayed reporting of hospital admissions and fatalities, and the inability to account for any periodontal treatment that may have taken place after the patient reported oral health measures.
Despite their limitations, both studies make a strong case for the active promotion of periodontal health. While it is not proven that periodontal disease causes COVID-19 complications, we can stress the importance of good oral hygiene and periodontal disease prevention.
With most dentists still operating at reduced capacity and routine care still interrupted, it is inevitable that cases of periodontal disease will go undetected. With this in mind, dentists must take every opportunity to cultivate awareness and encourage habits like thorough brushing and interdental cleaning via, for example, routine screening, remote consultations and patient outreach.
When doing so, it is important to present the facts in a balanced and non-alarmist manner. Acknowledge that your advice is based on ongoing research, but point out that the connection between periodontal disease and other systemic illnesses is well-established. Emphasize that, whatever the research ultimately concludes, there is much to be gained – and certainly nothing to be lost – by maintaining good periodontal health.