Diabetes and its sixth complication

Dr Christopher Turner MSc, BDS, MDS, FDSRCS is a retired specialist in restorative dentistry. Here he discusses the direct relationship between periodontal disease and diabetes. On Dr Turner’s behalf his MP, Wera Hobhouse Liberal Democrat Shadow Leader of the House of Commons and MP for Bath, has this week (16th March) put forward a petition to the House of Commons. The petition urges the Government, and in particular the Department of Health and Social Care to add questions about dental care to the five diabetic risks already checked annually by doctors, and to require doctors to record the names of patient’s dentists in their notes and give them annual HbA1c results – and for dentists to send an annual summary of the Basic Periodontal Examination with an explanation of the scores to patient’s doctors.


Diabetes mellitus and periodontal disease are directly related, one affecting the other and vice versa although the exact mechanism is under debate and is probably associated with chronic inflammatory mediators. Periodontal disease is the sixth complication of diabetes and has received little recognition by doctors to date. Dental care is omitted from the NICE annual diabetic check list recommendations in the UK despite studies showing improvements in glycaemic control occur when periodontal disease is brought under control. Doctors need to identify patients not receiving dental care while doctors and dentists need to work more closely and share their respective clinical results to achieve better patient outcomes.


Doctors will recognise the well documented serious complication of diabetes mellitus including:

  • Cardiopathy
  • Micro and macro arterial disease
  • Nephropathy
  • Neuropathy
  • Retinopathy

The sixth complication is periodontal disease (1) first reported by Williams in 1928 (2). Xerostomia is another dental symptom. High blood glucose levels are associated with an increased incidence of oral thrush.

Periodontal disease may be defined as the loss of bony support to the teeth, increased pocket depth and inflammation of the surrounding tissues caused by the body’s reaction to toxins in plaque with reduced levels of tissue healing the severity and progression of which depend on the host response to the biofilm (3).

Recent research from many countries confirms the inter-relation between diabetes mellitus (DM) and periodontal disease (PD) (4), the one affecting the other and vice versa. DM and PD are biologically linked (5).

There is a common pathogenesis between diabetes and periodontal disease involving an enhanced inflammatory response at both local and systemic level. This is caused by the long-term effects of hyperglycaemia and the formation of advanced glycation products and lipids that promote the inflammatory response (6). Levels of cytokines and tissue necrosis factor are raised in DM (7) while raised interleukin 8 gives a potential contribution to cross-susceptibility (8). C-reactive protein is raised in both diseases (9). The chronic bacteriological challenge of periodontal disease is a persistent source of inflammatory mediators (10) and may lead to endothelial dysfunction (11).

Various mechanisms for this altered immune response in the periodontal tissues of diabetics have been put forward. None are proven. Periodontal disease results in the loss of bony support to the teeth and increased pocket depth caused by the body’s reaction to plaque (12), an abnormal immune response with reduced levels of tissue healing. Polysaccharides in Gram-negative bacteria in dental plaque stimulate the production of cytokines and oxidative stress is critical in the development of diabetic complications (6). It is the severity of hyperglycaemia that affects the periodontium most (13).

As PD and DM affect each other, there is some evidence to suggest that individuals with PD may be at risk of developing Type 2 diabetes (14) and pre-eclampsia (15). PD has an adverse but modifiable effect on glycaemic control (16). The overall management of DM may improve (17) because periodontal therapy improves metabolic control (18).

There are few studies in the literature looking at PD in relation to the known risks of DM.

Cardiopathy and arterial disease

Poor oral health is associated with atherosclerotic cardiovascular disease (19) while new cases of PD and not just pre-existing cases place women at significantly elevated risks for future cardiovascular events (20). This interaction raises cardiovascular morbidity fourfold and is associated with chronic infection, mediators from which may lead to the initiation of endothelial dysfunction (21). This interaction has not been a major focus in clinical cardiology to date and action is required (19).


Diabetics on haemodialysis are at greater risk of periodontal disease and other oral manifestations and have increased oral health problems (22). For severe periodontal disease there is a 2.6 times greater risk of macroglobulinaemia and 4.9 times for end stage renal disease (ESRD) (23) and a significantly higher index of decayed, missing or filled teeth (DMFT) (24).

In a Japanese study 40 per cent of dialysis patients had diabetic nephropathy, a lower glomerular filtration rate with a higher periodontal index (CPI) and a positive correlation between CPI score and serum creatinine (25). This study proposed that the CPI should be the periodontal index of choice given its World Health Organisation status (26) and universality. Helpfully they classified periodontal disease as low risk with a CPI score of 0 or 1, medium with a score of 2 or 3, and high with a score of 4 or 4*. This should be a benchmark for future studies.

Periodontitis predicts the development of overt nephropathy and ESRD in a dose dependent manner in individuals with little or no pre-existing kidney disease (23). Periodontal management can contribute to the prevention of severe renal disease (25).


Neuropathy is a microvascular complication (26). Only neuropathy is associated with the other dental manifestation of DM, xerostomia (27). That can affect over 40 per cent of diabetics resulting in a significant inverse relationship between salivary flow and HbA1c levels and may be due to disturbances in glycaemic control (28). Other oral symptoms are burning mouth and impaired taste or smell that contribute to morbidity and a low quality of life and can be overlooked (29).

Diabetics with xerostomia have a lower buffering capacity and are at greater risk of developing caries. Oral bacteria metabolise sucrose into acids within a few minutes of intake. pH levels of 2 are commonly reached within 2 0r 3 minutes and can last for twenty minutes as described in the Stephan curve, before returning to normal. These patients may benefit from chewing gum that must be xylitol based as his 5-carbon compound is not metabolised in the mouth.


There are very few studies with no consistent choice of periodontal index to allow a meta-analysis. In one study of 100 type 2 diabetics there was a definite association (30). An increase in the severity of diabetic retinopathy is associated with the components of periodontal disease including the plaque index and gingival index (31).


The links between DM and PD cannot be ignored although the National Institute for Clinical Excellence in the UK has yet to include dental checks on its list for doctors with checks for other five diabetic complications, a serious omission. Many doctors are unaware of this relationship, for example only 5.7 per cent were in a recent study in Hong Kong (32).

However, both periodontal disease and caries, the most common diseases known to mankind, are preventable and treatable allowing patients to retain an intact dentition if they can access dental care.

Both diseases are related to dental plaque. Prevention requires thorough daily plaque control to reduce the numbers of bacteria and biofilm both supra- and sub-gingivally using toothbrushes and interspace brushes first, then possibly mouthwashes. This is the patient’s responsibility supplemented by dental appointments to remove calculus and biofilm by ultrasonic scaling, teaching about brushing techniques and educational reinforcements at intervals determined by the periodontal status. Diabetics have learned to control their blood sugar levels following suitable education. Therefore the vast majority should be capable of managing and controlling their plaque.

Doctors could ask the following simple questions when they review their diabetic patients:

Q1. Do you have regular dental care?

If the answer is ‘Yes’ the then ask…

Q2. Do you have gum disease and is it under control?
Q3. Who is your dentist?

If the answer is ‘No’ then ask…

Q2. Do your gums bleed when you brush your teeth?
Q3. Are you gums receding and your teeth getting loose? (33).

Gingivitis can develop after just seven days of missing plaque removal in an area of the mouth (34). Bleeding gums are never normal and recession and loosening are pathognomonic for periodontal disease. These patients should be advised to seek dental care.

At first sight question 3 seems unnecessary. In their medical record questionnaires dentists always ask patients who is their General Practitioner. The reverse does not happen routinely. However, in the light of the evidence, there is a greater need for co-operation and cross-referral and the sharing of test and examination results between the two professions than has generally been the case to date (35). Doctors aim to keep the HbA1c level below 6.5; dentists aim to achieve a zero score in each sextant of the mouth as shown by the CPI score.

The CPI score is the recommended periodontal measurement for future studies because of its World Health Organisation credentials and universality. The examination by probing of periodontal pockets using a colour-coded measuring instrument looks at the worst score in each sextant of the mouth, molars and premolars on each side, canines and incisors, and scored in both mandible and maxilla. For the purposes of easy comparisons the highest score in the worst sextant is the measurement of choice for both studies and inter-professional sharing.

At present, the CPI score (Basic Periodontal Examination score in the UK NHS) is not collated with the HbA1c level and there is an absence of inter-professional collaboration between doctors and dentists while managing patients with DM (36). By relating HbA1c levels to CPI scores doctors and dentists should be able to establish better treatment protocols. Diabetics are at 3 to 4 times greater risk of developing periodontal disease than non-diabetics. For diabetics who smoke the risk is 10 times greater (37).

There is a need for:

  • Doctors to be aware of the two-way relationship between DM and PD.
  • Sharing of test results.
  • Doctors to advise diabetics not attending for dental care about their increased risks of complications.
  • NICE to include dental care on its annual check list for doctors.


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