Periodontal Disease: A Co-Morbidity Factor in Diabetes Mellitus

Turner C

Published on: 2025-04-17

Abstract

In 1999 Periodontal Disease (PD) was thought to be the sixth complication of Diabetes Mellitus (DM) because this latter group of patients has a 3 – 4 times greater risk of developing PD when compared with non-diabetics. This rises to 10 times for smokers. More recent research has concluded that DM and PD are inter-related, one disease affecting the other and vice versa. The exact mechanism is probably related to inflammation as similar blood markers are raised in both diseases, the dental origin of which is from micro-organisms in mature dental plaque. From the medical point of view there are five complications of DM namely cardiac, vascular, renal, ophthalmic and neurological that can be visualised as a simple hub called DM with spokes for the above complications. However, the evidence has shown that the severity of all these five complications is worse when patients have active, uncontrolled PD. When PD is treated, there is an improvement in glycaemic control. Good oral hygiene is a critical component of glycaemic control. These results have led to the conclusion that PD is not a separate complication of DM but a co-morbidity factor acting by: modifying the severity of another disease and modulating the severity of diabetic complications in the manner of a volume switch. A new model is proposed together with a system for doctors and dentists to work together because when DM and PD are treated together there may be a synergistic effect.

Keywords

Diabetes mellitus; Periodontal Disease; Dental

Introduction

The concept that periodontal disease was the sixth complication of Diabetes Mellitus (DM) and the increased risk that people living with diabetes had of developing Periodontal Disease (PD) dates back to 1999 [1]. However, the first description of this was much earlier in 1928 and forgotten [2]. We now know that this risk is about 3-4 times greater than for non-diabetics, rising to 10 times for diabetics who smoke [3].

Pathophysiology

From the medical point of view there are five complications of diabetes mellitus namely, cardiac, vascular, renal, ophthalmic and neurological. We can visualise this simply as a hub called diabetes mellitus with spokes for the above complications (Figure 1). Where does periodontitis fit in? Is it another spoke? The evidence is overwhelming that diabetes and periodontitis are interrelated, one disease affecting the other and vice versa [4,5], so the model relationship has to have both diabetes and periodontitis at a much larger hub with an inter-relationship (Figure 2). More importantly, the research evidence has shown that the severity of all these five diabetic complications is worse when patients have active, uncontrolled periodontitis. Also, when periodontitis is treated, there is an improvement in glycaemic control [6]. Good oral hygiene is a critical component of glycaemic control in diabetic patients [7].

Figure 1: The Medical model of Diabetes Mellitus (DM).

Figure 2: The New Model of Diabetes Mellitus and Periodontitis.

The relationship between DM and PD is thought to be inflammatory in origin. There is a common pathogenesis involving an enhanced inflammatory response at both local and systemic levels [8]. This is caused by the chronic effects of hyperglycaemia and the formation of advanced glycation end-products that promote the inflammatory response [8]. Levels of C-reactive protein [4], tissue necrosis factor [7,8] and cytokines [9] are raised in both diseases. Polysaccharides in Gram negative bacteria in mature dental plaque are known to stimulate the production of cytokines. Toxic products from these organisms initiate tissue breakdown and increased osteoclastic bone resorption in the periodontium [10]. Osteoclastic activity also increases along with enhanced glycation levels and poor glycaemic control [11], thus stimulating further bone resorption and diminished bone formation in a vicious circle and contributing to the enhanced levels of periodontitis and alveolar bone loss seen in people living with diabetes. When dental plaque is left, after seven to ten days gingival inflammation ensues and this is the precursor of periodontitis [12]. PD may be thought of as an infection. However, it is not in the true medical sense of the word because it does not meet Koch’s postulates for a single recoverable infective agent. PD is a chronic hyper sensitivity reaction to antigens in mature dental plaque. Research has shown that when the severity of diabetic complications is compared to periodontal status that for:

Cardiac and Vascular: Poor oral health is associated with atherosclerotic cardiovascular disease. This interaction raises cardiac morbidity fourfold and is associated with chronic infection mediators which may lead to the initiation of endothelial dysfunction [13].

Nephropathy: People on dialysis are at greater risk of developing PD [14]. With severe Periodontitis there is a 2.6 times greater risk of macroglobinaemia and a 4.9 times risk of end stage renal disease [15]. Periodontal management may contribute to the prevention of renal disease [16]. Patients should be screened for periodontitis before acceptance onto dialysis programmes [17].

Neuropathy: Is a microvascular complication associated with xerostomia in 40 per cent of people living with diabetes mellitus [18]. The increased risk of caries goes without saying. There is an inverse relationship between salivary flow and glycated haemoglobin (HbA1c) levels that may be due o disturbances in glycaemic control [19].

Retinopathy: There are few studies of this complication together with PD using different criteria [20,21]. However, an increase in the severity of diabetic retinopathy is associated with the components of periodontal disease [22].

From this evidence it is clear that periodontitis is influencing of diabetic’s individual responses and medical complications. It is both:

Modifying the severity of another disease
And modulating the severity of diabetic complications in the manner of a rheostat, the greater the level of periodontal disease, the worse the complications at one end of the spectrum, while when PD is successfully treated glycaemic control improves at the other.

This is a new concept and means that PD should not be regarded as a complication of DM but a co-morbidity factor. Therefore, for optimum treatment of people living with diabetes there has to be both medical and dental contemporaneous input into their care. When both are treated together there may be a synergistic effect [23]. In summary, the new model shows dentists can support doctors and their diabetic patients and improve outcomes. There is a need for a paradigm shift in thinking and better interprofessional co-operation in care [24,25]. One method may be a traffic light risk assessment form for both diseases that people living with diabetes can share with their professional advisors [26,27].

Defining Risk Factors for Doctors

The medical gold standard for diabetic monitoring is the serum level of glycated haemoglobin, the HbA1c. This may be recorded as percentage levels that should be maintained below 6.5%, green on the traffic light method above [26,27]. There is an amber band for 6.5 to 8.5% and a red band for greater than 8.5%. Other values are either mmol/mol or mmol/litre (Table 1). However, previously determined individual targets could be more appropriate for some people with diabetes, particularly those who are frail or lack awareness of hypoglycaemia [28].

Table 1: HbA1c levels and medical risks.

Percentage	<6.5	6.5-8.5	8.5>
mmol/mol	<48	48-69	69>
mmol/L	<7.8	7.8-10.9	10.9>
Risk factor	Low, green	Moderate, amber	High, red

Defining Risk Factors for Dentists

Various indices of periodontal health have been described. The measure of choice is the World Health Organisation’s Community Periodontal Index of Treatment Need (CPITN) [29]. The mouth is divided into sextants with scores given for pocket depth measurement, bleeding on probing or calculus and the maximum score recorded which gives a periodontal risk factor using the traffic light system,0,1,or 2, green, 2* or 3, amber, and 4 0r 4* as red (Table 2).

Table 2: Periodontal risk factor.

Highest sextant score	0 or 1 or 2	2* or 3	4 or 4*
Risk factor	Low, green	Moderate, amber	High, red

A pro forma has been developed for people living with diabetes to record their results and share them with their respective professional advisors (Table 3) [26]. This form is freely downloadable at www.chooseabrush.com.

Table 3: MY DIABETES RESULTS FOR 20……..

Discussion

Doctors need to understand basic facts about periodontitis and record which of their patients is receiving dental care and advise those who are not that they are at greater risk of developing PD and that when PD is treated their blood sugar levels can be better controlled [30,31]. Dentists need to understand the importance of HbA1c scores and add these to their patient’s medical histories [32]. In our recent study, asking this question in general dental practice these are the results [33], 40 per cent were in the green zone, 20 per cent amber, 12 per cent red and 28 per cent did not know. The importance here is that as the HbA1c increases, bringing PD under control becomes harder. Fortunately, periodontitis is both a treatable and preventable disease with good clinical outcomes when detected at an early stage. Prevention depends on daily efficient and effective plaque control by patients [7,34]. When plaque is left in situ for 7 to 10 days inflammation results [12]. Where these is bone loss between teeth and gingivae the most efficient way to remove plaque is by using interdental brushes. These are made in a variety of diameters by different manufacturers some of whom have a limited size range [35]. For ideal results in individual prescription for the correct diameter brush for each space is essential as in one study every pattern of bone loss and therefore brush diameter requirement was individual [34]. When few sizes are suggested, common sense says that plaque will always be left behind contributing to the bacteriological load, periodontal disease will continue and diabetic complications are less likely to be limited. This means that the critical component in glycaemic control, good oral hygiene, will not be achievable [7].

Conclusion

PD is not the sixth complication of DM. It modifies and modulates the severity of diabetic complications. This means that both diseases should be treated concurrently and that dentists and their teams have a very important role to play together with doctors. The glycated haemoglobin results, HbA1c are essential for dentists. The higher the score the more difficult it is to control periodontal disease. Risk results need to be shared between doctors and dentists. A form has been developed for patients themselves to show their respective professional advisors. This can be downloaded at www.chooseabrush.com.

Dentists need to be more proactive, teach and work with doctors who may not know about the increased risk that their patients living with DM have for PD.

Declaration of Interest

The author is the inventor of the Chooseabrush® method of interdental plaque control.

International Journal of Endocrinology and Diabetes