Association between Decayed, Missing, Filled Teeth (DMFT) index and diabetes mellitus among adults in Central Sudan: a community-based cross-sectional study

Abstract

The association between diabetes mellitus (DM) and the Decayed, Missing, Filled Teeth (DMFT) index is not yet settled. This study aimed to assess associations between DM and the DMFT index among adults in Central Sudan. A community-based cross-sectional study was conducted among adults (aged ≥ 18 years) in Central Sudan using a multistage stratified random sampling design. Dental morbidity was assessed using the DMFT index as a continuous dependent variable. Modified multivariate Poisson regression was used to calculate Adjusted Relative Risks (ARR) for associated factors. Seven hundred and seventy-three adults were enrolled. The median (interquartile range, IQR) DMFT index was 5 (2–10), and 14.6% of participants had DM. After adjustment, older age, lower education, and unemployment were significantly associated with the DMFT index. DM was associated with the DMFT index (ARR = 1.18, 95% CI = 1.10–1.26). Glycated (HbA1c) levels were also independently associated with increased DMFT index (ARR = 1.03, 95% CI = 1.02–1.04). DM is associated with DMFT index among adults in Central Sudan. There is a need to integrate oral and systemic health initiatives in Sudan.

1. Introduction

Dental caries, or tooth decay, is the most prevalent chronic non-communicable disease globally, affecting billions of people across all socioeconomic strata and age groups [1–4]. Although largely preventable through public health measures and individual oral hygiene practices, the accumulated burden of dental disease poses a significant challenge to public health systems worldwide. Untreated dental caries and missing teeth lead to profound consequences, including chronic pain, infection, loss of function, aesthetic compromise, and, in severe cases, reduced quality of life and even potentially increased risk of mortality [2–5]. In epidemiological research, the lifetime cumulative experience of dental decay is robustly quantified using the Decayed, Missing, Filled Teeth (DMFT) index [6]. This internationally recognized index serves as a comprehensive surveillance tool for dental caries, summarizing the severity and extent of past and current disease.

Critically, the interpretation of the DMFT index depends heavily on the healthcare context. In high-income settings with established restorative dental services, the ‘Filled’ (F) component often dominates the index, reflecting successful clinical intervention [7]. Conversely, in resource-limited and underserved areas, such as those found across Sub-Saharan Africa (SSA), the index is often overwhelmingly driven by the untreated decayed (‘D’) and missing teeth (‘M’) components [8–11]. Therefore, in these African settings, a high DMFT index primarily signals a crisis of access to timely and effective restorative dental care [11,12].

Simultaneously, the International Diabetes Federation (IDF) estimates that the prevalence of diabetes mellitus (DM) is escalating rapidly, placing immense strain on healthcare infrastructures globally, particularly in developing economies, including Sudan [13]. SSA, in particular, is predicted to see some of the most dramatic increases in DM prevalence over the next few decades [10,14].

The confluence of high rates of dental caries and rising DM prevalence is a critical public health concern in Sudan. DM is a complex condition characterized by chronic hyperglycemia resulting from defects in insulin secretion, insulin action, or both [15]. The risk factors for both dental caries and DM overlap significantly, suggesting shared social, behavioral, and biological determinants. Several factors, such as increasing age [16,17], sex [17–20], low education [16–18], unemployment [21], high body mass index (BMI) [17,18], higher fasting blood glucose level [18], were found to be associated with dental caries and missing teeth. Moreover, a study in Sudan found that dental caries was more prevalent among T2DM patients, particularly those with uncontrolled disease, compared with their non-diabetic controls [22]. A study in Sudan revealed a high prevalence of tooth loss (78%); 66.9% was due to caries, and 11.2% to other causes [8]. Studies in Sudan have previously identified common associations between the two conditions. For instance, in Sudan, DM and its poor control were found to be associated with increasing age [23], higher BMI [24], and low socio-economic status [25]. These shared determinants may interact synergistically, potentially amplifying the risk for both conditions within vulnerable community settings.

Despite the compelling biological rationale, the epidemiological evidence linking the full burden of oral infectious diseases, quantified explicitly by the DMFT index, to DM remains surprisingly sparse, particularly within SSA populations [10]. Much of the established literature focuses narrowly on the association between DM and periodontitis, often using clinical measures like attachment loss or probing depth [26]. While vital, this focus overlooks the cumulative dental destruction captured by the DMFT index.

The DMFT index is a more holistic measure of lifetime dental caries experience because it integrates outcomes of dental caries (D), treatment history (F), and permanent tooth loss (M). In a low-resource environment like Sudan, where extraction is often the definitive endpoint of untreated decay, the number of Missing Teeth (the ‘M’ component) becomes a critical, tangible marker of advanced, neglected oral infection and severe cumulative health disadvantage. Studies that rely only on periodontitis may miss the significant burden of chronic, end-stage caries that necessitates extraction [26]. Given the shared associations between risk factors for dental caries and DM in Sudan [8,9], and the prevalence of DM with poor control among Sudanese adults [23]. This study is positioned to precisely quantify the integrated health burden and clarify the specific contributions of DM and related factors (such as glycated hemoglobin, HbA1c) to the overall DMFT index.

Given the significant and growing prevalence of dental caries and DM in Sudan, and the credible, biologically supported linkage between these chronic conditions, quantifying their combined effect is a necessary step toward effective public health interventions. In addition to the low and late dental service utilization [27], an underdiagnosed DM status [23]. There is a clear and urgent need for community-based epidemiological data to inform targeted screening and preventative protocols that integrate both oral and systemic health initiatives. Thus, the primary aim of this community-based cross-sectional study was to determine factors, including DM status (diagnosed via HbA1c levels) and other socio-demographic variables, associated with the DMFT index among adults aged 18 years and older in Central Sudan.

2. Methods

2.1. Study design and setting

This community-based cross-sectional study was conducted from April to June 2025 among adults in Central Sudan. This study was conducted in Elrikieb, East Gezira, in Central Sudan. Gezira State is located in east-central Sudan, lying between the Blue and White Nile rivers. Elrikieb was chosen because it comprises four sub-villages, and its inhabitants resemble those of the entire Gezira State. In this study, the authors strictly adhered to the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) guidelines [28].

2.2. Study population and sampling

In the present study, 773 adults were recruited. Participants were recruited from the community through a systematic approach. A multi-stage stratified random sampling approach was employed to select the potential participants. Within each selected sub-village, households were randomly selected using the lottery method. The number of selected households was proportional to the sub-village's population. From each eligible household, one adult was randomly selected (lottery method) and invited to participate in the study. When there was no adult in the selected household, or they were unwilling to participate, the next household was chosen instead.

2.3. Inclusion and exclusion criteria

Before data collection, informed consent was obtained from the participants. Therefore, all adults 18 years and older were included in the present study. Those who did not give their consent were excluded. Also, pregnant women, severely ill adults, those with thyroid disease, obvious deformity, and those below 18 years or on steroids were excluded from the study.

2.4. Sample size calculation

Based on previous guidelines [29], a sample size of 773 adults was calculated, assuming a minimum significant correlation (r = 0.10) between DMFT index and other independent factors (e.g. HbA1c). This sample size (773) was accurate and optimum for achieving a 95% confidence level with a 5% margin of error (precision) and 80% power.

2.5. Study variables and measures

Data were collected using a questionnaire that was developed for this study following a thorough literature review. The questionnaire collected information on socio-demographic factors, including age, sex, marital status, education, and occupation. Anthropometric measurements of weight and height were taken as previously mentioned in a previous study [30]. Then, BMI was computed as the weight in kg divided by the square of the height in meters (m) (kg/m²) [31]. In this study, HbA1c was measured to diagnose DM. Dental caries were assessed by trained dental doctors.

Diabetes mellitus Assessment: DM was diagnosed using HbA1c levels in accordance with standard clinical guidelines. According to the International Diabetes Federation guideline for non-pregnant adults, a participant was classified as DM based on HbA1c level (≥6.5%) or a current known diabetic, regardless of adherence to diabetic medications adherence [15]. Therefore, any adult who was known to be diabetic or newly diagnosed with DM was considered to have DM, and others with normal HbA1c or not known to have DM before were considered not diabetic.

Dental assessment: In this survey, the dental examination was conducted in-house by two dental doctors (male and female) with three years of practice. The dentists examined the adults sitting on an ordinary chair using mouth mirrors under natural lighting conditions. To reduce inter-examiner variability, the DMFT index was assessed by trained dental doctors. The dentists had received theoretical training (30-min presentations to explain and address participants' inquiries) and photographic (that met all DMFT index criteria) reviews. The dentists (examiners) were calibrated against the senior dentist (MM) to ensure diagnostic consistency, typically achieving a Kappa coefficient > 0.6. The DMFT index is a widely accepted epidemiological tool that provides a comprehensive measure of an individual's lifetime dental caries experience by summing the number of teeth that are decayed, missing due to caries, or filled because of decay, in accordance with the World Health Organization (WHO) recommendation [6]. The use of this standardized index enabled consistent and reliable evaluation of the caries burden across the study population. By quantifying the cumulative effects of past and present disease, the DMFT index enables robust comparisons with other regional and international studies, highlighting its importance for public health research and surveillance. In this study, the DMFT index was analyzed as a continuous variable.

2.6. Statistical analysis

The data were entered into SPSS for Windows (version 22.0; SPSS Inc., New York, NY, USA) statistical software for analysis. The continuous data, such as age, BMI, and DMFT index, were tested for normality using the Kolmogorov–Smirnov test and were found to be non-normally distributed. Consequently, they are expressed as medians (interquartile ranges, IQRs). Categorical data were expressed as frequencies (percentages). Modified univariate Poisson regression was performed with DMFT index as dependent variable, and socio-demographic factors and diabetes status, including HbA1c, as independent variables. Furthermore, variables with p-values < 0.2 in the univariate analysis were included in a multivariate Poisson regression to model the DMFT index independently and estimate the adjusted relative risk (ARR) with a 95.0% confidence interval (CI). Because HbA1c contributed to the definition of DM, DM and HbA1c were entered separately in the models. Multicollinearity was assessed using the Variance Inflation Factor and was not present (VIF < 4). A two-sided p-value less than 0.05 was considered statistically significant.

3. Results

3.1. Study population characteristics

A total of 773 adults were recruited for this study (229 [29.6%] males and 544 [70.4%] females). The median (IQR) age was 39 (28–53) years. The median (IQR) BMI was 21.7 (18.7–26.1) kg/m². The majority of the participants were married 556, 71.9%). Regarding education, about one-quarter (184, 23.8%) of the participants had a secondary education level or higher. The majority of participants, 558 (72.2%), were unemployed, and the rest, 215 (27.8%), were employed (public or private). The median (IQR) HbA1c was 5.4% (5.1%–5.9%). Of the total 773 adults, 113 (14.6%) had DM (Table 1). The median (IQR) DMFT index and missing teeth index were 5 (2–10) and 2 (0‒4), respectively. The median (IQR) number of decayed teeth was 3(1‒5). Few adults had filled teeth; of the total 773, only 45 had at least one.

Table 1.

Socio-demographic and clinical characteristics of the studied adults in Central Sudan (n = 773), 2025.

Variable		Total (n = 773)
		Median	Interquartile range
Age, years		39.0	28.0‒53.0
Body mass index, kg/m2		21.7	18.7‒26.1
Decayed, Missing, Filled Teeth (DMFT) index		5	2‒10
Missing teeth score		2	0‒4
Decay teeth score		3	1‒5
Glycated hemoglobin, %		5.4	5.1‒5.9
		Frequency	Percentage
Sex	Male	229	29.6
	Female	544	70.4
Marital status	Married	556	71.9
	Unmarried	217	28.1
Education	≥Secondary	184	23.8
	<Secondary	589	76.2
occupation	Employed	215	27.8
	Unemployed	558	72.2
Diabetes mellitus	No	660	85.4
	Yes	113	14.6

3.2. Associated factors with DMFT index

The results of the univariate Poisson analysis showed that older age, higher HbA1c, female sex, lower education, unemployment, and DM were associated with DMFT index. In contrast, BMI and marital status were not associated with DMFT index (Table 2). After adjustment (multivariate Poisson analysis), older age (ARR = 1.024, 95% CI = 1.022‒1.025) and higher HbA1c (ARR = 1.03, 95% CI = 1.02‒1.04) were positively associated with DMFT index. Moreover, being female (ARR = 1.36, 95% CI = 1.24‒1.50), being less educated (ARR = 1.43, 95% CI = 1.31‒1.55), being unemployed (ARR = 1.10, 95% CI = 1.001‒1.21), and having DM (ARR = 1.18, 95% CI = 1.10‒1.26), were positively associated with DMFT index. As in the univariate analysis, marital status was not associated with the DMFT index (Table 3).

Table 2.

Unadjusted (univariate Poisson analysis) factors associated with Decayed, Missing, Filled Teeth (DMFT) among adults in Central Sudan (n = 773), 2025.

Variable		Unadjusted relative risk	95% confidence interval	p
Age, years		1.024	1.023‒1.025	<0.001
Body mass index, kg/m2		1.001	0.998‒1.004	0.539
Glycated hemoglobin, %		1.06	1.05‒1.08	<0.001
Sex	Male	Reference
	Female	1.08	1.02‒1.14	0.008
Marital status	Married	Reference
	Unmarried	0.95	0.90‒1.01	0.140
Education level	≥Secondary level	Reference
	<Secondary level	2.07	1.91‒2.24	<0.001
Occupation	Employed	Reference
	Unemployed	1.16	1.09‒1.23	<0.001
Diabetes mellitus	No	Reference
	Yes	1.52	1.43‒1.63	<0.001

Table 3.

Adjusted (multivariate Poisson regression analysis) factors associated with Decayed, Missing, Filled Teeth (DMFT) score among adults in Central Sudan (n = 773), 2025.

Variable		Adjusted relative risk	95% confidence interval	p
Age, years		1.024	1.022‒1.025	<0.001
Glycated hemoglobin, % a		1.03	1.02‒1.04	<0.001
Sex	Male	Reference
	Female	1.36	1.24‒1.50	<0.001
Marital status	Married	Reference
	Unmarried	1.003	0.94‒1.06	0.922
Education level	≥Secondary level	Reference
	<Secondary level	1.43	1.31‒1.55	<0.001
Occupation	Employed	Reference
	Unemployed	1.10	1.001‒1.21	0.049
Diabetes mellitus a	No	Reference
	Yes	1.18	1.10‒1.26	<0.001

^a Because HbA1c contributed to the definition of DM, DM and HbA1c were entered separately in the models.

4. Discussion

This community-based cross-sectional study, conducted among adults in Central Sudan, provides evidence of an association between DM and the cumulative burden of dental disease, assessed independently using the DMFT index. The principal findings confirm that both DM status and elevated HbA1c are associated with increased DMFT index. Moreover, this study showed that the socioeconomic determinants—such as older age, lower educational attainment, and unemployment—were associated with the DMFT index. Given the high prevalence of neglected dental needs and the substantial proportion of adults in the cohort with undiagnosed or established DM (14.6%), these findings call for integrated oral and systemic health strategies in Sudan.

The current study showed that having DM (ARR = 1.18) and having higher HbA1c levels (ARR = 1.03) were associated with a higher overall DMFT index. This supports existing literature from various settings, as reported by Vu et al., that DMFT index was associated with DM and its control [17]. The present results align with the consensus that the chronic hyperglycemic state inherent to DM creates a biologically hostile environment in the oral cavity. As mentioned in the introduction, hyperglycemia promotes the accumulation of AGEs and results in impaired host immune responses, accelerating both periodontitis and dental caries progression [32].

Beyond shared associated factors, robust scientific evidence suggests a direct, mechanistic, and bidirectional link between chronic oral infectious diseases and a spectrum of metabolic conditions, including DM [26,33,34]. The inflammatory response primarily mediates this connection. The core biological rationale connecting DM and poor oral health involves two primary pathways: first, chronic inflammation and insulin resistance; second, chronic oral infections, particularly severe periodontitis, act as a persistent source of bacterial antigens and pro-inflammatory mediators (cytokines), such as IL-6, into the systemic circulation [35]. This chronic, low-grade systemic inflammation directly contributes to insulin resistance in peripheral tissues, which is the foundational pathology of T2DM. Conversely, DM itself exacerbates oral infections: hyperglycemia leads to the formation of Advanced Glycation End-products (AGEs) that accumulate in periodontal tissues, impairing the immune response, hindering wound healing, and promoting excessive tissue destruction, creating a vicious cycle between the two diseases [36–38]. Second, impaired immunity and hyperglycemia: hyperglycemia, whether due to prediabetes or established DM, impairs host defense mechanisms. Individuals with poorly controlled DM exhibit dysfunctional neutrophil and macrophage activity, making them significantly more susceptible to bacterial and fungal infections [39]. This immunosuppression not only fuels the progression of periodontitis but also accelerates the microbial shift in the oral cavity that drives dental caries. Furthermore, elevated glucose levels in saliva create an environment highly conducive to the growth of cariogenic bacteria, thereby directly accelerating the demineralization process that leads to caries lesions. While periodontitis has historically received the most attention in the DM literature, the chronic inflammatory and immune dysregulation associated with DM can also promote the rapid progression of dental caries and consequent tooth loss.

The finding regarding sex presents an interesting nuance: being female was positively associated with a higher overall DMFT index (ARR = 1.36). The higher overall DMFT index among females is consistent with some global studies [10,18]. This vulnerability may be linked to several factors: hormonal fluctuations that can increase susceptibility to gingivitis and potentially caries, higher frequency of snacking, or even genetic predispositions, as suggested by some authors [40]. This may reflect, first, treatment-seeking: women in this community, despite higher decay incidence, may place greater value on retaining anterior teeth for aesthetic reasons or seek treatment for symptomatic decay slightly earlier than men, thereby preserving their teeth, even if only partially through basic restoration. Second, disease type: periodontitis is often cited as a major cause of tooth loss in older men, potentially masking the caries-related component of tooth loss [18].

Our results showed that older age was associated with the MFT index (ARR = 1.024). This is consistent with studies across SSA [10,16,19]. As expected, given that the DMFT index measures cumulative lifetime disease exposure [41]. Moreover, the results of the current study showed that lower education was associated with a higher DMFT index. This massive disparity highlights that lack of education is a significant barrier, likely through multiple pathways: reduced health literacy (understanding the need for early intervention), lower perceived value of oral health, and limited financial means to afford available dental services [42]. Unemployment was also significantly associated with both poor DMFT index (ARR = 1.10). This aligns with earlier findings that showed unemployment was associated with poor oral health [21].

4.1. Study implications and recommendations

The results of this study carry profound implications for public health policy in Central Sudan. Firstly, the robust association between DM/HbA1c and advanced dental disease strongly supports integrating oral health screening into DM management protocols. Every adult presenting with established DM or high HbA1c should be routinely referred for a comprehensive dental examination. Conversely, dental practitioners in resource-limited settings should be trained to screen for DM risk (e.g. using a short questionnaire or HbA1c measurement) in patients presenting with advanced dental caries or excessive tooth loss. Secondly, the extreme risk associated with low education and unemployment demands interventions beyond the clinical setting. Public health efforts must target health literacy, subsidize or provide free restorative dental services for low-income groups, and implement preventive education programs that emphasize the crucial link between diet, oral hygiene, and systemic health. Given the dominance of the ‘D’ and ‘M’ components, a priority must be placed on accessible, affordable restorative and preventive services to shift the current paradigm away from tooth extraction as the default treatment [43].

4.2. Study strengths and limitations

This study has significant strengths, including its community-based design and a large sample size (n = 773) selected through a multi-stage stratified random sampling approach, which enhances the representativeness of the findings for the adult population of Central Sudan. The use of HbA1c is a gold standard for assessing long-term glycemic control and DM status [15], providing a more objective measure than self-reported DM diagnosis.

The study, however, is subject to limitations inherent to its cross-sectional design, which precludes any determination of causality or directionality. While the biological plausibility suggests DM drives caries progression, it is also possible that chronic oral infection contributes to poor glycemic control (HbA1c) [36]. Future longitudinal studies are recommended to clarify this bidirectional relationship over time. The reliance on DMFT does not provide data on the specific contribution of periodontitis to tooth loss, requiring further clinical assessment to disentangle these effects. The sample was predominantly female (70.4%), which may affect generalizability. Important variables such as sugar intake, dietary habits, smoking, oral hygiene practices, dental attendance, fluoride exposure, duration of DM, and socioeconomic measures were not included in the analyses. WHO criteria used for caries underestimate the caries level compared with the more sensitive International Caries Detection and Assessment System (ICDAS) criteria. Unadjusted clustering analysis is a study weakness, as its potential effect on the confidence intervals and statistical significance.

5. Conclusion

DM is associated with the DMFT index among adults in Central Sudan. There is a need to integrate oral and systemic health initiatives in Sudan. The comorbidity in this study is compounded by socioeconomic disadvantages, particularly low educational attainment, and this needs more attention too.

Author contributions

AOB, MM, and IA: conception, design, acquisition of data, analysis, interpretation of data, and drafting the article. AA and SMO: conception, design, acquisition of data, analysis, interpretation of data, and revising the manuscript critically for important intellectual content. All authors have approved the final version of this manuscript.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Funding

This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.

Data availability statement

The data of this study will be available from the corresponding author upon reasonable request.

The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.

Ethics approval and consent to participate

This study was conducted in accordance with the principles outlined in the Declaration of Helsinki and good clinical research practices. Ethical approval was granted by the Research Ethics Committee of the Faculty of Medicine and Health Sciences at the University of Gadarif in Gadarif, eastern Sudan (Ref. #2025, 07). Institutional permission to conduct the study was obtained from the Ministry of Health, Gezira State (Letter # 50/B/1; May 18, 2025). Written informed consent was obtained from all participants.

Consent for publication

Not applicable.

Clinical trial registration

Not applicable.

Abbreviations

BMI

Body mass index

CI

confidence interval

DMFT

Decayed, Missing, Filled Teeth

DM

diabetes mellitus

IQR

interquartile range

WHO

World Health Organization