Oral health knowledge, attitudes and care practices of people with diabetes: a systematic review

In 2014, it was estimated that 422 million adults were living with diabetes mellitus (DM) worldwide [1]. The global prevalence of diabetes in the adult population has nearly doubled since 1980, rising from 4.7% to 8.5% [1]. Diabetes mellitus (DM) is a group of metabolic disorders that leads to hyperglycaemia and is classified into four general categories: type 1, type 2, gestational diabetes and other specific types of diabetes [2].

Hyperglycaemia can cause several complications related to different organ systems especially the eyes, kidneys, nerves, heart, and blood vessels [1]. Although not commonly discussed in diabetes care, people with uncontrolled diabetes are also at increased risk of developing oral health problems, particularly periodontal (gum) disease [3]. Periodontal disease, which includes both gingivitis and periodontitis, is a common inflammatory disorder caused by pathogenic microflora in the biofilm that forms adjacent to the teeth on a daily basis [4]. Gingivitis is the mildest form of periodontal disease in which inflammation is confined to the gingiva, and can be reversible with effective oral hygiene while periodontitis is the advanced stage where the inflammation extends deep into the tissues and causes loss of supporting connective tissue and alveolar bone [4]. Tissue destruction in periodontitis results in breakdown of collagen fibres of the periodontal ligament and leads to the formation of periodontal pockets between the gingiva and the tooth. Periodontitis is a slowly progressing disease but the tissue destruction is largely irreversible [4, 5]. Further, the bacteria located within the periodontal pockets are pathogenic and highly inflammatory with some having the ability to survive in the blood stream and infect other areas of the body [6, 7]. Moderate periodontitis affects approximately 40–60% of the adults worldwide [8].

It is well established that diabetes and periodontitis are directly related. Hyperglycaemia affects periodontal outcomes and periodontitis also adversely affects blood glucose levels and worsens diabetes complications. The mechanistic pathways that link diabetes and periodontitis is not clearly understood in the absence of experimental findings from clinical studies [9]. However, current information supports the potential complex interaction involving aspects of inflammation, immune functioning, neutrophil activity, and cytokine biology [9]. Hyperglycaemia is believed to enhance levels of several cytokines and mediators in saliva and gingival crevicular fluid (GCF), oxidative stress in periodontal tissues and formation of Advanced Glycation Endproducts (AGE). The AGE–RAGE (Receptor for AGE) interaction leads to the exaggerated inflammatory response and periodontal tissue destruction seen in diabetes [8]. Similarly, periodontitis promotes measures of systemic oxidative stress and raises serum levels of C-reactive protein and other acute-phase reactants and biomarkers of oxidative stress. Non-resolving chronic inflammation derived from periodontal disease also impacts on diabetes control (elevated HbA1C) and complications [8]. In light of this, current evidence from interventional studies suggests that periodontal treatment can improve blood glucose control [8, 10‐12], although this evidence is often considered low quality [12] due to the heterogeneity of the studies and small sample size [13, 14].

Considering the impact of periodontal disease on diabetes and benefits of good oral health practices to minimise the risk of periodontal disease, it is important to ensure that people with diabetes are motivated to engage in good oral hygiene behaviours and are provided risk assessment and dental referrals as a part of routine diabetes care [15‐17]. Several studies conducted worldwide have assessed the knowledge, attitude and practices of people with diabetes relating to oral health care, however, synthesis of these results has not yet been undertaken. Conducting such a review is important as adequate oral health knowledge or literacy is positively associated with good oral health behaviours such as, increased frequency of brushing and dental visits [18] and good periodontal health [19]. Further, oral health behaviours are influenced by the social determinants of health [20], Those who are disadvantaged or from lower socio economic groups often have unhealthy habits, poor knowledge and attitudes to oral health and uptake of dental services and therefore are more likely to suffer from the burden of oral disease [20]. Thus, the aim of this systematic review was to synthesize current evidence on the knowledge, attitudes and practices of people with diabetes in relation to their oral health care.

This study used the PRISMA statement as a basis for reporting the systematic review findings [21, 22]. The protocol for this systematic review was not registered.

All studies (n = 28) used a cross sectional design (including a intervention study) to capture the information on the knowledge, attitude and practices of patients in relation to oral health care. Of these, 4 studies used existing data or followed up participants previously included in state and national surveys [25‐28]. The studies originated from 14 countries namely, United States of America (USA; n = 8), India (n = 5), Saudi Arabia (n = 2), Malaysia (n = 2), Pakistan (n = 2), United Kingdom (UK; n = 1), Sweden (n = 1), Ireland (n = 1), Finland (n = 1), Brazil (n = 1), United Arab Emirates (UAE; n = 1), Jordon (1) South Korea (n = 1) and Iran (n = 1). The sample size of the studies ranged from 50 to 12,405 participants with a total of 27,894 people with diabetes. Three studies surveyed the participants with type 1 DM [29‐31], 6 involved participants with type 2 DM [32‐37] and the remaining included both types of DM as well as people with unknown type of DM (Table 1). A variety of questionaries were used to assess oral health knowledge, attitude, and care practices of people with diabetes. Only 9 studies used a validated questionnaire or items, while remaining did not provide any clear information in this area. The questionnaires included in the studies contained items ranging from 4 to 40. Of the total studies, 4 were rated as good quality (score ≥ 80), 23 fair (score 50–79%) and the remaining as low quality (score <  50%) (see Additional file 2).

The focus of this review was to provide a synthesis of current evidence on knowledge, attitudes and practices of people with diabetes in relation to their oral health care. The questionnaire and methods used to conduct surveys in this area were largely varied and hence the reliability of the studies included in this review may be compromised. More than half of the studies also failed to provide information about the validity of the tools used to measure knowledge, attitude and practices. Furthermore, almost all of the studies used convenience sampling and most did not report the response rate or any comparison between the respondents and non-respondents. Of the total studies included in this review only four were rated as of good quality.

Overall, the results of this review show that a majority of people with diabetes are unaware of the bidirectional link between diabetes and periodontal disease and they have limited knowledge of their risks for oral health problems [18, 29‐32, 34, 36‐45]. As could be expected, knowledge of oral health risks was found to be significantly associated with better oral health care and practices [18, 44]. However, a majority of people with diabetes did not receive information on oral health risks in relation to their diabetes or advice on oral health care from diabetes care providers [29‐33, 42, 46, 49]. This finding is similar to the results from a recent scoping review which explored the knowledge and practices of diabetes care providers in oral health care and found that they generally do not provide any information on oral health care to their patients in the diabetes care settings [17]. According to the review the main barriers facing diabetes care providers in this area include inadequate knowledge about the oral health-diabetes bidirectional relationship, unavailability of oral health assessment tools/guidelines and referral pathways for promoting oral health [17].

In spite of being at high risk for developing oral health problems, the perceived need and importance for oral health care among people with diabetes is found to be very poor [39, 42], as it appears oral health is not as important as general health for these patients [29, 36]. People with diabetes rated their overall oral health lower [35, 38] than that those without diabetes [30]. The cost of dental care, lack of dental care need, unpleasant dental visits, and difficulty in scheduling appointments were found to discourage people from seeking dental care [30, 31, 36, 37, 42, 50]. Despite these barriers, this review also found that people with diabetes are more likely to engage in positive health behaviours if they are informed about the risks and consequences of poor oral health. Patients were also found to be interested in receiving oral health information from diabetes care providers [50].

Most notably, people with diabetes were found to have poor compliance with oral hygiene behaviours and dental visits as less than half of the patients (49.3%) reported brushing twice a day. In addition, flossing of teeth appeared to be least important for patients with diabetes with only a quarter (25.1%) of the participants reported flossing their teeth everyday to clean interdental surfaces. Similarly, just over half (54%) of the people visited a dentist in the 12 months. Large national studies have also reported a lower frequency of dental visits among people with diabetes compared to those without diabetes [43, 49]. These figures are lower than the general population of some high income countries such as in England where a higher proportion of adults (aged 15 and over) brushed twice a day (75%) and visited dentist (73%) in the last 12 months [53]. Similarly, nearly two third of American (64% aged 18–64) [54] and Australian (60.3% aged 15 and over) [55] visited dentist in the past year [54]. This delay to seek dental care among people with diabetes is a significant concern considering periodontal disease can negatively impact on diabetes control and worsen diabetes complications [8].

This review has also identified various factors that could contribute to the poor oral health knowledge, attitudes, and behaviours among people with diabetes. One of the key factors is the limited oral health education and motivation being provided to these patients during diabetes care. It is apparent that oral health education can improve knowledge, attitudes, and practices regarding oral health [56] and therefore it is very important to include it in diabetes patient education, which is a vital and integral component of successful diabetes care [57]. Such education should include aspects of good oral hygiene practices as these are important to prevent gingivitis (earlier stage of gum disease) and control of advanced periodontal lesions [58].

Another major barrier identified in this review is the cost of dental care, which is often cited as an issue among people with chronic conditions [59]. Treatment of oral health problems is often costly and has been a significant economic burden for many high income countries [60]. Similarly, accessible dental care services is also important considering the fact that a study from Sweden reported more than one third of people with diabetes did not visit the dentist despite being entitled for subsidised dental care. Similar results are also found in the general population in Australia where a national oral health survey reported that there were no significant differences in dental visit between adults eligible for public dental services and those who were not eligible (both 62%) [55]. Although it is not specified in the study from Sweden, it is possible that the lengthy waiting time to access in public/subsidised dental care services [59, 61] may deter people with diabetes from visiting a dentist. Therefore, the feasibility of setting up affordable and accessible dental referral pathways for people with diabetes also needs to be explored as such preventative initiatives could ultimately be more cost effective [62] than delaying dental treatment until severe oral complications have developed. Most importantly, the identification and treatment of periodontal disease is particularly relevant for this at risk population as it could potentially improve their diabetes control [11‐16]. However, strategies to improve the oral health of people with diabetes may need to be tailored to high and low income countries particularly since oral health is not a priority for patients in low income countries and dental problems are often left untreated [63]. Furthermore, there is insufficient emphasis on primary prevention of oral diseases and limited access to oral health care [63] in developing countries. In this context, population based preventive oral health programs could be more effective.

It is also important to consider that while diabetes care involves a multidisciplinary team including general practitioners, endocrinologists, diabetes educators, dietitians, podiatrist and physiotherapists, dentists are usually not included as part of this care team, despite the impact of poor oral health on diabetes control. Considering the findings of this review, both diabetes care providers and dentists have an excellent opportunity to collaborate and increase awareness among patients with diabetes of their increased risk of oral health problems and motivate them to have good oral hygiene behaviours and regular dental visits. The involvement of dentists in multidisciplinary teams has shown to have a positive impact in other clinical areas like antenatal care. For example, the Midwifery Initiated Oral Health (MIOH) program in Australia where dentists and midwives work in partnership has demonstrated a significant improvement in the oral health knowledge and confidence of midwives to promote oral health as well as the oral health knowledge, quality of life, uptake of dental services and oral health status of pregnant women [64, 65].

This systematic review confirms that people with diabetes have inadequate oral health knowledge, poor oral health attitude, and lower compliance of recommended oral hygiene behaviours and dental visits. They are also not receiving adequate oral health information and care advice from diabetes care providers. It is important that people with diabetes are educated about their increased risk of oral health complications and encouraged to seek regular dental checkups. A multidisciplinary approach involving oral health professionals is needed to capacity build diabetes care providers to promote oral health and encourage their patients to seek dental care along with the establishment of appropriate and affordable dental referral pathways.