According to the CDC, diabetes affects 14.7% of U.S. adults and 29.2% of those over age 65, making it the 8th leading cause of death.[1] Its annual economic burden is estimated at $413 billion, and rates are expected to rise with an aging population and increasing obesity, highlighting the need for early and coordinated care.
Chronic hyperglycemia leads to impaired wound healing, increased infection risk, and major microvascular and macrovascular complications, including nephropathy, neuropathy, retinopathy, cardiovascular disease, stroke, and higher rates of lower-limb amputation, while also promoting chronic inflammation and microbiome alterations [2]. Diabetes and oral health are bidirectionally linked: poor glycemic control increases the risk of periodontal disease, caries, mucosal lesions, infections, and delayed oral healing, while uncontrolled periodontal inflammation can further worsen glycemic control, underscoring the importance of coordinated medical and dental care.
Figure 1. Patient with type 2 diabetes diagnosed with Oral Lichen Planus.
The relationship between diabetes and periodontal disease is well established, with periodontitis recognized as the sixth complication of diabetes [3]. Diabetic patients have a threefold higher risk of periodontal disease. At the same time, periodontitis is associated with undiagnosed diabetes, increased risk of other diabetic complications, and worse cardiovascular outcomes, including higher rates of myocardial infarction and stroke [3–5]. Poor glycemic control and periodontal disease exacerbate each other, whereas periodontal treatment has been shown to improve HbA1c levels and reduce systemic inflammation; both conditions are linked to inflammatory burden and dysbiosis of the oral microbiome, contributing to insulin resistance, with non-surgical periodontal therapy reducing markers such as C-reactive protein [4, 6–8].
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Oral manifestations of diabetic neuropathy
Diabetic neuropathy is a common, length-dependent sensorimotor disorder caused by chronic hyperglycemia-related metabolic and microvascular injury, affecting up to 50% of patients and closely correlated with glycemic control, including in prediabetes [9]. Oral manifestations include xerostomia, glossodynia, dysgeusia, reduced salivary flow, and trigeminal pain and TMJD, with diminished taste, particularly for sweets, that progresses alongside neuropathy and predicts its onset in up to 88% of cases [9–11].
Diabetes and oral cancer
Multiple studies have shown a greater prevalence of benign oral mucosal lesions in patients with diabetes, particularly coated tongue, fissured tongue, migratory glossitis, and denture stomatitis, among other forms of candidiasis [12, 13]. Fissured tongue and migratory glossitis are strongly correlated, and both have both genetic and environmental etiologies. A coated tongue may be due to the salivary alterations mentioned in the previous section. The combination of xerostomia, elevated salivary glucose levels, decreased salivary pH, and reduced wound-healing capacity in diabetic patients alters the oral microbiome. It predisposes them to a variety of infections, particularly candida. Diabetic patients have higher rates of mucosal colonization with Candida species and a higher rate of denture stomatitis [12]. They may also present with erythematous or pseudomembranous candidiasis [13].
Aside from these, there are rarer cases of oral mucosal disorders that are important to note. Medications used to control glucose (i.e., oral hypoglycemics) can also cause oral lichenoid reactions, characterized by ulcerations, white lines, erythematous areas, and burning pain. They typically resolve with discontinuation of the drug [13, 14]. To further confuse the issue, diabetes also has a moderate association with oral lichen planus, particularly in European populations [15]. Moreover, there may be some association between various forms of autoimmune vesiculobullous disorders and diabetes – one study of pemphigus patients found that 18% of them were also diabetic [13].
Diabetes is associated with a significantly increased risk of developing numerous cancers as well as higher cancer-related mortality overall. Oral cancer represents another major global public health challenge, with incidence rising steadily each year. Notably, diabetic patients are 4.34 times more likely to present with oral leukoplakia with an estimated malignant transformation rate of approximately 1% per year [16]. As discussed previously, diabetes is also linked to a higher prevalence of oral lichen planus (Figure 1), another chronic inflammatory mucosal disease with documented malignant potential.
The interplay between insulin resistance, oxidative stress, chronic hyperglycemia, systemic inflammation, immune dysregulation, and altered microbial ecology likely contributes to the increased susceptibility to oral epithelial dysplasia and malignant transformation in this population. Epidemiologic studies consistently demonstrate that individuals with diabetes have a higher likelihood of developing oral tumors and experience poorer long-term outcomes once cancer occurs; in fact, cancer-related mortality is more than doubled, with a reported 2.09-fold increase in risk [16]. Importantly, these trends are observed across diverse geographic regions, suggesting that the association is not solely attributable to tobacco use patterns or environmental factors. Emerging evidence also indicates that diabetic patients face significantly higher recurrence rates of oral squamous cell carcinoma. Interestingly, this elevated risk may be mitigated by metformin treatment [17].
Conclusion
Diabetes has wide-ranging oral manifestations driven by chronic hyperglycemia, inflammation, and metabolic dysfunction, with a well-established bidirectional relationship between glycemic control and periodontal disease [18, 19]. Diabetic neuropathy, salivary dysfunction, microbiome alterations, and increased susceptibility to mucosal and potentially malignant disorders contribute to higher risks of infection, temporomandibular disorders, and oral cancer, underscoring the need for patient education, regular oral examinations, and integrated oral–medical care as part of comprehensive diabetes management.
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References
[1] Centers for Disease Control and Prevention. National Diabetes Statistics Report. https://www.cdc.gov/diabetes/php/data-research/index.html. Accessed December 9, 2025.
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