Diabetes mellitus is a group of metabolic diseases that leads to high levels of blood glucose (hyperglycemia) and occurs when the body does not make any or enough insulin, or does not use insulin well. In 2020, it was estimated that 34.2 million people of all ages in the U.S. (i.e., 10.5% of the population) had some form of diabetes; of these, the disease was undiagnosed in 7.3 million adults, meaning that over 21% of adults with diabetes were undiagnosed.1 Because diabetes is a relatively common condition, practicing dentists are likely to encounter it frequently.2
Classification. Classification of diabetes is based on the pathogenic processes that can lead to either absolute or relative lack of insulin, resulting in hyperglycemia (high blood glucose).2 Insulin is a hormone produced by pancreatic islet beta cells, which is needed for the uptake of blood glucose by cells to produce energy. When there is a lack or absence of insulin, or when cells are insensitive to its actions, a high circulating level of blood glucose results (i.e., hyperglycemia).2 Although there are various causes for less common types of diabetes, including drug- or chemical-induced diabetes, exocrine pancreatic disease, or infections (e.g., cytomegalovirus), the two most common subtypes of diabetes are known as type 1 or type 2 diabetes.2
Type 1 diabetes, formerly known as juvenile diabetes, is a chronic autoimmune disease in which the beta cells in the pancreas create little to no insulin2, 3 and accounts for 5% to 10% of all diabetes cases.2 Autoimmune destruction of beta cells is the most common cause, although any loss of pancreatic tissue (e.g., pancreatitis, surgical removal of the pancreas) can lead to insulin dependence.2 Type 1 diabetes is generally diagnosed in younger individuals (usually younger than 25 years of age) and has a strong genetic predisposition.2 Exogenous insulin is needed to regulate blood glucose levels in people with type 1 diabetes.2
In contrast, type 2 diabetes accounts for 85% to 90% or more of diabetes cases and is one of the most common chronic diseases, as well as one of the leading causes of death and disability in the U.S.4 Type 2 diabetes is characterized by decreased response of target tissues to normal levels of insulin, requiring increasing levels of insulin for an adequate response, and a relative hyperinsulinemia and insulin resistance.2 Type 2 diabetes is associated with excess weight, physical inactivity, family history of diabetes, and certain ethnicities.5, 6 Although some people with type 2 diabetes can help improve their glycemic control with diet, exercise, and weight loss, patients may require insulin sensitizers that help peripheral tissues take up glucose (i.e., biguanides [metformin] or thiazolidinediones) or oral hypoglycemic agents that stimulate release of insulin (i.e., insulin secretagogues such as sulfonylureas).2
Another type of diabetes is gestational diabetes, a state of glucose intolerance that occurs in pregnant women who do not otherwise have diabetes.2 Occurring in the second half of a pregnancy, gestational diabetes is caused by placental hormones and results in insulin resistance and relative insulin deficiency.2 Although true gestational diabetes resolves during the postpartum period, those who have had gestational diabetes are at increased risk of developing type 2 diabetes later in life.2
The term “prediabetes” is used when blood glucose levels are higher than normal, but not high enough for a formal diagnosis of diabetes.5 Prediabetes means a person is at increased risk for developing type 2 diabetes, as well as at increased risk for heart disease and stroke.5 Although lifestyle modification involving weight loss and engaging in moderate physical activity can help people with prediabetes delay or prevent the onset of type 2 diabetes,5 it is estimated that as many as 90% of those with prediabetes are unaware that they have prediabetes.7 Assessment of risk for prediabetes can be conducted using printed or online versions of a seven-item questionnaire available through the American Diabetes Association, Centers for Disease Control and Prevention, and American Medical Association (links available in the “Other Resources” section).
Symptoms/Diagnosis. Initial symptoms of diabetes include increased thirst and urination. Other symptoms can include unexplained weight loss, fatigue, blurred vision, increased hunger, and sores that do not heal.
Blood tests are generally used in the diagnosis of diabetes and prediabetes.5 Tests used include measurement of hemoglobin A1c (HbA1c), which is a measure of glycosylation of the hemoglobin molecule, fasting blood glucose measurement, and/or an oral glucose tolerance test.8 The American Diabetes Association provides recommendations for classification and diagnosis of diabetes.
Complications. Over time, individuals with diabetes sustain progressive damage to nerves and blood vessels due to elevated levels of circulating glucose, which can increase the incidence and severity of complications such as heart disease, stroke, kidney disease, retinopathy, neuropathy, dental disease and amputations.9, 10 Additionally, diabetes may increase susceptibility to other diseases, impair mobility, contribute to depression, and cause problems during pregnancy.11
Three common complications that can occur when glucose levels are not well controlled are hypoglycemia, hyperglycemia and diabetic ketoacidosis.
Hypoglycemia. Hypoglycemia is a condition in which blood glucose levels drop below normal. For many people with diabetes, this means a blood glucose level of 70 milligrams/deciliter (mg/dL) or less.12, 13 Hypoglycemia also may be referred to as “insulin shock” or “insulin reaction.” Untreated hypoglycemia can result in unconsciousness, coma or death.
Several situations can lead to hypoglycemia:12
Symptoms. Symptoms of hypoglycemia may include changes in mental state or emotions, or physical symptoms.
Shakiness
Sweating
Fast or irregular heartbeat
Dizziness or lightheadedness
Hunger
Nervousness
Change in behavior or personality
Tingling or numbness of the lips or tongue
Treatment. If hypoglycemia is suspected, immediate treatment should be implemented.
(*NOTE: People who have concomitant kidney disease should not drink orange juice for their 15 grams of carbohydrates because of the high potassium content.12 Apple, grape, or cranberry juice cocktail are good alternatives.)
In severe cases, hypoglycemia can cause unconsciousness, seizures or coma. If the dental patient is not awake and/or unable to eat or drink, emergency medical help should be summoned.13 Injectable glucagon, available by prescription, signals the liver to release glucose into the bloodstream, and can help restore blood glucose levels to normal in emergencies. Glucagon may be administered while waiting for help to arrive.14
Hyperglycemia. Hyperglycemia occurs when blood glucose levels are abnormally high. This can occur anytime there is not enough insulin in the bloodstream or the body is not using insulin properly.
Several conditions can lead to hyperglycemia (e.g., pancreatitis, Cushing’s syndrome, pancreatic cancer, adrenal hormone insufficiency), but it is a primary symptom of diabetes. Untreated hyperglycemia can damage the cardiovascular, circulatory or nervous systems, the kidneys or vision.15 It can also result in delayed wound healing.16 In more serious cases, extreme or prolonged hyperglycemia, can cause a life-threatening condition called ketoacidosis (see below for further discussion).
A number of circumstances can lead to hyperglycemia in people with diabetes:17
Symptoms. Symptoms of hyperglycemia include:
Treatment. Lifestyle changes, like increased exercise or eating a healthy, well-proportioned diet,18 may help control hyperglycemia. (NOTE: People with diabetes whose glucose level is above 240 mg/dL are advised to check their urine for ketones. If ketones are present, they should not exercise and should consult their physician for other ways to reduce their blood sugar levels.17) If these changes do not help resolve hyperglycemia, a physician may recommend adjusting current medications or prescribing new or additional medication to better manage glucose levels.
Diabetic Ketoacidosis. Diabetic ketoacidosis is a serious condition that can develop when there is not enough insulin to help the body adequately use glucose.
Diabetic ketoacidosis develops when the balance between glucose and insulin levels is not well controlled. The body typically metabolizes glucose to generate energy. When insulin levels are too low, the body begins to break down fat cells for energy instead, which results in the production of acidic ketones in the blood. Buildup of ketones in the blood can be toxic. Without intervention, which usually must be done in a hospital, coma or death can occur.19
Symptoms. The following symptoms may indicate diabetic ketoacidosis:19
Treatment. If ketoacidosis is suspected, the symptomatic person should be taken to the nearest emergency room or that person’s physician should be immediately contacted.19
Monitoring Glucose Levels. Blood-glucose levels can be checked chairside using a drop of blood. Glucometers designed for use in a variety of settings, such as nursing homes, health fairs or dental clinics, are available by prescription. Because they are intended for use by multiple individuals, they are designed to facilitate thorough cleaning and disinfection between uses to help prevent the spread of bloodborne pathogens.20 After each use, the device must be cleaned and disinfected according to the manufacturer’s instructions.20,21
Staff should be familiar with glucometer use to help avoid errors that could affect glucose readings, such as improper use, problems with the device or reagents used with the device, or environmental problems like lighting.20
Periodontal disease is commonly seen in people with diabetes,22-24 and is considered a complication of diabetes.2, 22, 23, 25, 26 The relationship between diabetes and periodontal disease is often described as being two-way or bidirectional, meaning that hyperglycemia affects oral health while periodontitis affects glycemic control (e.g., increased HbA1c).26-31 Research also suggests that periodontitis is associated with poor glycemic regulation,2, 23, 28 but the evidence is inconsistent,22, 23 particularly in patients with type 1 diabetes.25, 28 Most research indicates an association between periodontal disease and increased risk of diabetes-related complications.25, 27, 28
A 2018 systematic review and meta-analysis update of a 2012 review confirmed findings that periodontitis is associated with (1) higher HbA1c levels in persons without diabetes and persons with type 2 diabetes, (2) worsened complications from diabetes in people with type 2 diabetes, and (3) a higher prevalence of complications in persons with type 1 diabetes.25 The study also found that periodontitis is associated with higher prevalence of prediabetes, and that severe periodontitis is statistically significantly associated with an increased risk of developing diabetes.25
Diabetes and smoking are both considered risk factors for periodontitis.32, 33 There is some evidence that smoking and diabetes may have a synergistic effect, although the mechanism(s) responsible are unclear as changes to the oral microbiome,32 inflammatory response, and even periodontal health34 are not consistently reported to be altered when comparing people with diabetes who do and do not smoke.35
Periodontal Treatment and Glycemic Control
There is inconsistent, but suggestive, evidence that periodontal treatments, including scaling and root planing, may result in improvement of glycemic control.23, 27, 28, 36-38 A 2018 systematic review of observational studies found “insufficient evidence to evaluate the impact of periodontitis on glycemic control” in persons with type 1 diabetes, but that periodontitis is associated with higher HbA1c and worse diabetes-related complications in persons with type 2 diabetes.25 A 2018 systematic review of meta-analyses of randomized controlled trials (RCTs) reaffirmed earlier findings that periodontal treatment (i.e., scaling and root planing) significantly reduces HbA1c levels at 3 months, with even more reduction after 6 months.37 Results from RCTs, however, are not entirely consistent: a 2013 study of patients with type 2 diabetes found no improvement in glycemic control following periodontal therapy,39 and a 2018 study found no significant change in glycemic control in patients with type 1 or type 2 diabetes.40 Despite lack of a consensus on treatment outcomes in controlling glycemic levels, it is generally agreed that patients with diabetes benefit from periodontal therapy in conjunction with good oral health maintenance at home.26-28, 41
Diabetes can arise in individuals at any age. As with all patients, it is recommended that dentists review the patient’s medical history, take vital signs, and evaluate for oral signs and symptoms of inadequately controlled diabetes, which may be common.42 Oral manifestations of uncontrolled diabetes can include xerostomia, burning sensation in the mouth (which may possibly be related to neuropathy), impaired/delayed wound healing, increased incidence and severity of infections, secondary infection with candidiasis; parotid salivary gland enlargement; gingivitis and/or periodontitis.22, 42
A dentist may want to ask a patient with diabetes questions such as:42
In general, morning appointments are advisable for patients with diabetes since endogenous cortisol levels are typically higher at this time; because cortisol increases blood sugar levels, the risk of hypoglycemia is less.43, 44 For patients using short- and/or long-acting insulin therapy, appointments should be scheduled so they do not coincide with peak insulin activity, which increases the risk of hypoglycemia.43 It is important to confirm that the patient has eaten normally prior to the appointment and has taken all scheduled medications.43 If a procedure is planned with the expectation that the patient will alter normal eating habits ahead of time (e.g., conscious sedation), diabetes medication dosing may need to be modified in consultation with the patient’s physician.43 Patients with well-controlled diabetes can usually be managed conventionally for most surgical procedures.42 If the patient’s food consumption will be affected after oral or dental surgery, a plan to balance the patient’s diabetes medications and food intake should be established in advance.42
When treating patients with marginally or poorly controlled diabetes, elective dental treatment may need to be delayed until the patient’s diabetes is considered stable or better controlled.42
Dental implant placement is generally safe and reliable in patients with properly controlled diabetes, and possibly in those with moderately controlled disease. Two recent systematic reviews concluded that implants in patients with diabetes have predictably high survival rate at least within the first three years, provided that the patients maintain good glycemic control,45 and that implant procedures are safe and predictable in patients with well-controlled diabetes.46 However, systematic reviews have also advised that clinicians consider HbA1c values for risk assessment of patients with diabetes prior to implant placement (and throughout the implant’s lifespan), and to consider hyperglycemia as a significant risk factor associated with peri-implant inflammation.45, 47 In patients with poorly controlled diabetes, implant placement may have an unpredictable prognosis, delayed osseointegration and higher risk of failure.42, 46
Coordination with the patient’s physician may be necessary to determine the patient’s health status and whether planned dental treatment can be safely and effectively accomplished.42 Physicians should make laboratory test results available to the dentist upon request, and inform the dentist of any diabetic complications of relevance to the individual patient prior to dental procedures.42 The physician may need to adjust the patient’s diabetes medication to help ensure sustained metabolic control, before, during, and after surgical procedures.42 Patients with diabetes should obtain regular medical and dental care, including regular dental visits for full evaluation of their dental and periodontal condition.28
Emergency Management. Although patients with diabetes often recognize signs and symptoms of hypoglycemia and self-intervene before changes in or loss of consciousness occurs, they may not be fully cognizant of such signs.2 As a result, a hypoglycemic event may arise in a clinical setting without any initial signs or visible indications from the patient with diabetes. Training staff to recognize signs of hypoglycemia (e.g., mood changes, unusual behavior or profuse sweating), and to use a glucometer to test a diabetic patient’s blood glucose levels can help prevent hypoglycemic episodes.2, 44 Every dental office is advised to have a protocol for managing hypoglycemia in conscious and unconscious patients.2 Having snack foods or oral glucose tablets or gels available, especially in practices where a large number of surgical procedures are performed, is also prudent.2
Professional Resources
ADA Oral Health Topics: Oral-Systemic Health
Search JADA for articles related to diabetes
ADA Store
ADA Library Services
Patient Resources
JADA “For the Patient” pages
ADA MouthHealthy.org pages
American Diabetes Association
National Institute of Dental and Craniofacial Research
National Institute of Diabetes and Digestive and Kidney Diseases
Prediabetes Risk Assessment Questionnaires
National Clinical Care Commission–Report to Congress on Leveraging Federal Programs to Prevent and Control Diabetes and Its Complications (2021)
U.S. Food and Drug Administration: How to Safely Use Glucose Meters and Test Strips for Diabetes
Last Updated: January 24, 2022
Prepared by:
Department of Scientific Information, Evidence Synthesis & Translation Research, ADA Science & Research Institute, LLC.
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