Introduction

Chronic Kidney Disease (CKD) is defined by the National Kidney Foundation (NKF) Kidney Disease Outcomes Quality Initiative (KDOQI) guidelines as abnormalities in kidney structure or function persisting for more than three months, with implications for health1,2. According to a recent meta-analysis, approximately 697.5 million individuals are affected by CKD at all stages, representing a global prevalence of 9.1%. Among these, about 2% progress to End-Stage Kidney Disease (ESKD), with the risk of progression increasing two- to three-fold in patients presenting with proteinuria, hypertension, or diabetes3.

CKD represents an increasing public health burden in Saudi Arabia, driven by a high prevalence of diabetes, hypertension, obesity, and aging. A recent large population-based epidemiological study in Saudi Arabia reported an overall CKD prevalence of approximately 4.76%, with the majority of affected individuals classified as stage 3 disease. The prevalence was higher among males than females and increased markedly with age, reaching nearly 51% among the oldest age groups. These findings highlight a significant CKD burden within the Saudi population, comparable to national data from other high-income regions, and underscore the importance of assessing associated complications, including oral health conditions, among patients undergoing long-term hemodialysis4.

The insidious onset and asymptomatic progression of CKD often result in delayed diagnosis until the advanced stages, when systemic manifestations become evident. Common symptoms include pruritus, peripheral edema, fatigue, poor appetite, metallic taste, and body weight fluctuations, all of which negatively influence patients’ quality of life5,6. Gastrointestinal manifestations—particularly alterations in taste and oral dryness—are frequently observed during the late stages of CKD, especially in ESKD patients undergoing dialysis. Studies have reported that up to 38% of ESKD patients experience changes in taste perception. These taste alterations have been significantly associated with upper gastrointestinal symptoms such as oral dryness, vomiting, anorexia, and malnutrition7.

A systematic review by Ferrara et al. (2025)8 suggested a possible role of zinc deficiency in malnourished dialysis patients, where zinc supplementation produced variable improvements in taste perception. In addition to uremic toxin accumulation, micronutrient disturbances—particularly zinc deficiency—have been increasingly implicated in taste dysfunction among patients with chronic kidney disease. Zinc deficiency is highly prevalent in CKD and hemodialysis populations due to reduced dietary intake, impaired intestinal absorption, chronic inflammation, and increased losses during dialysis sessions. Zinc plays a critical role in taste perception through its involvement in gustin (carbonic anhydrase VI), a zinc-dependent salivary enzyme essential for the development, maintenance, and regeneration of taste buds. Zinc deficiency has been shown to result in taste bud atrophy, reduced taste receptor sensitivity, and impaired signal transduction, leading to dysgeusia or hypogeusia.

In patients undergoing hemodialysis, zinc depletion is further exacerbated by protein–energy wasting, gastrointestinal disturbances, and metabolic alterations, which collectively compromise oral sensory function. Taste impairment in this context has been associated with reduced appetite, altered food preferences—often toward highly seasoned or sugary foods—and subsequent nutritional imbalance. These mechanisms provide a biological explanation for the high prevalence of taste alterations and their close association with xerostomia, malnutrition, and oral disease observed in patients with advanced CKD. Understanding the role of zinc deficiency therefore adds important etiological insight into the pathogenesis of oral manifestations commonly encountered in hemodialysis patients9.

The review also highlighted a positive correlation between taste alterations, gastrointestinal symptoms, and malnutrition in CKD patients. Similarly, a systematic review involving 27 studies demonstrated a significant association between the duration of CKD and the severity of taste dysfunction10. Another investigation confirmed a direct correlation between the degree of taste alteration and the decline in renal function11.

Certain oral symptoms may persist despite hemodialysis, leading to difficulties in chewing, speaking, and swallowing12. Hemodialysis has been shown to significantly influence the biochemical composition and flow rate of saliva. The concentrations of creatinine, urea, chloride, and potassium in whole saliva exhibit substantial fluctuations before and after dialysis sessions13. Xerostomia, or oral dryness, remains one of the most distressing symptoms in hemodialysis patients14. In a study involving 75 CKD patients, 45% exhibited hyposalivation11. Furthermore, a reduction in the number of fungiform papillae containing taste buds has been reported among patients with renal failure, suggesting a physiological basis for altered taste perception15.

Taste function plays a crucial role in maintaining nutritional intake and overall well-being. Thus, disturbances in taste and salivary flow can profoundly affect the quality of life of CKD patients, exacerbating malnutrition and systemic decline.

Despite global attention to the oral complications of CKD, data from Saudi Arabia remain scarce. Beyond taste disturbances and xerostomia, patients with chronic kidney disease—particularly those undergoing long-term hemodialysis—experience a substantial burden of other oral diseases that are frequently underrecognized. Dental caries has been consistently reported at higher prevalence in hemodialysis patients compared with the general population, largely due to reduced salivary flow, altered salivary composition, dietary modifications, and polypharmacy. Periodontal disease is also highly prevalent in this population and has been associated with systemic inflammation, impaired immune response, and poorer overall health outcomes. In addition, tooth wear and tooth loss are commonly observed, reflecting a combination of xerostomia, altered masticatory function, periodontal breakdown, and cumulative disease burden. Collectively, these oral conditions may compromise nutrition, quality of life, and systemic health, underscoring the need for comprehensive assessment of oral health status among hemodialysis patients16.

It was hypothesized that patients undergoing hemodialysis would exhibit a high burden of oral health problems, including xerostomia, taste alterations, dental caries, tooth wear, gingival inflammation, and tooth loss, and that these conditions would be significantly associated with demographic, behavioral, and clinical factors.

Therefore, the present study aimed to assess patient-reported oral health status and identify key predictors of oral pathologies among patients undergoing hemodialysis. Specifically, the study sought to evaluate the prevalence of xerostomia, taste alterations, dental caries, tooth wear, gingival inflammation, and tooth loss, while examining the influence of gender, age, smoking status, medication use, and xerostomia on these conditions.

Methods

Study design and setting

A cross-sectional survey was conducted among adult male and female patients diagnosed with CKD who were undergoing regular hemodialysis at several centers in the Ha’il province, Saudi Arabia. Ha’il is a North-central region of the country that serves as a regional healthcare hub with multiple hospitals and specialized dialysis centers, enabling recruitment of a diverse population of patients undergoing long-term hemodialysis.

The study was carried out over a two-month period (from 2nd August to 10th October), during which a total of 314 questionnaires were completed and included in the analysis. The study consisted of two components: a structured questionnaire followed by a clinical oral examination performed by trained dental professionals.

Ethical approval was obtained from the Research Ethics Committee at the University of Ha’il (IRB No. H-2025-814). All participants were provided with a detailed patient information sheet describing the study objectives and procedures. Participation was entirely voluntary, and written informed consent was obtained before data collection. Respondents were informed of their right to withdraw at any stage without justification and were assured that their data would remain confidential and used solely for research purposes.

Study population and sampling

A convenience sampling method was employed to recruit participants from different hospitals and hemodialysis centers in the Ha’il province. The inclusion criteria comprised adult patients (≥ 18 years) diagnosed with CKD and receiving hemodialysis for at least one year. Patients who agreed to participate and signed the consent form were included in the study.

Exclusion criteria included individuals under 18 years of age, patients who refused participation, those with psychiatric disorders, or individuals who had been on dialysis for less than one year.

Patients with common systemic comorbidities were not excluded, as multimorbidity is typical among hemodialysis patients. Excluding these conditions would reduce representativeness and external validity; therefore, systemic diseases were recorded and accounted for in the analysis.

Sample size estimation

The sample size for this cross-sectional study was determined based on:

$$\:N=\:\frac{Z\alpha\:\:\times\:P\:(1-P)}{{D}^{2}}$$

The following are the variables under consideration: Zα indicates the critical value of the Normal distribution at α/2 (for example, in the case of a 95% confidence level), N is the minimum sample size, α is set at 0.05 with a corresponding critical value of 1.96, P is the prevalence of the outcome of interest (specifically, the prevalence of oral health status among hemodialysis patients rate of 78% based on a previous study (18), and D is the degree of precision. There were 264 participants in the recommended sample size. To account for any non-replies or partial responses, the sample size was increased. 314 people made up the final sample size.

Data collection instrument

Data were collected using a structured, self-administered questionnaire adapted from previously validated instruments assessing oral health conditions, xerostomia, taste alterations, and oral manifestations among patients with chronic kidney disease and those undergoing hemodialysis (Supplementary 1)17,18,19,20. The questionnaire was originally developed in English and translated into Arabic to ensure accessibility for the study population. Although a formal back-translation was not performed, the Arabic version was reviewed by was bilingual Dental faculty members (HAA, AAM, JA, AFA) with over 20 years of expertise in oral medicine and dental public health to ensure conceptual equivalence, content accuracy, and cultural appropriateness. A pilot study involving 25 participants was conducted to assess clarity and response consistency. The reliability demonstrated high agreement (Cohen’s κ > 0.85). Based on pilot feedback and reliability analysis, minor linguistic and structural revisions were made prior to final data collection. Content validity and alignment with the study objectives were confirmed through expert review.

The finalized questionnaire consisted of 14 domains covering demographic, clinical, and oral health-related information. These domains included: (1) demographic characteristics (age and gender); (2) duration of hemodialysis; (3) presence of systemic diseases (hypertension, diabetes, cardiac, hepatic, or gastrointestinal conditions); (4) smoking status; (5) presence of xerostomia (mouth dryness); (6) presence of taste perception problems; (7) type of taste alteration (metallic taste, change in taste, or loss of taste); (8) difficulty in detecting specific tastes (sour, salty, sweet, or bitter); (9) timing of taste disturbance (before dialysis, after dialysis, continuous, or unspecified); (10) presence of burning-mouth sensation; (11) current medication use; (12) self-reported presence of dental caries; (13) self-reported tooth wear; and (14) self-reported gingival inflammation and missing teeth, including the affected area and perceived cause.

While the questionnaire captured patient-reported symptoms and oral health perceptions, clinical oral conditions were confirmed through a subsequent clinical examination.

Data collection procedure

Following institutional approval, the research team formally contacted the target hospitals and dialysis units to obtain administrative permission. Eligible patients were identified through clinical records and approached during their scheduled hemodialysis sessions. The study’s purpose and procedures were clearly explained to each participant, and written informed consent was obtained prior to participation.

Data were collected from participants attending their regular hemodialysis sessions. Each participant received an Arabic version of the questionnaire, accompanied by a concise explanation of the questions. Assistance was available upon request to clarify any ambiguities. The questionnaires were completed in a supervised setting to ensure consistency and completeness, and only fully completed questionnaires were included in the final analysis. To ensure uniformity, all data collection procedures were supervised by a single trained researcher.

Clinical oral examination

Following completion of the questionnaire, all participants underwent a standardized clinical oral examination performed by trained dental professionals. The examinations were conducted by HAA, a PhD holder with over 20 years of expertise, assisted by trained dental students (TSA and NMA). Prior to evaluation, a calibration training program was implemented to ensure accuracy, consistency, and strict adherence to the predefined assessment criteria. This program was closely supervised by three senior specialists (HAA, AAM, and AFA), each with more than 20 years of specialized experience in clinical practice and radiological interpretation. In addition to supervising the training, the senior specialists provided continuous guidance throughout the assessment process. Any disagreements or discrepancies among examiners were addressed through collaborative discussions, ensuring consensus for all challenging cases. The reliability was assessed using Cohen’s kappa statistic, which demonstrated excellent agreement across all evaluated parameters (κ = 0.91). The examination was conducted under appropriate lighting using disposable mouth mirrors and periodontal probes, in accordance with routine clinical assessment procedures.

Dental caries was recorded based on the presence of visible cavitation or frank carious lesions detected during visual–tactile examination. Periodontal involvement was assessed clinically through observation of gingival inflammation, bleeding on gentle probing, and visible periodontal tissue changes. Tooth wear and missing teeth were also recorded clinically. No radiographic assessment was performed.

The clinical examination findings were used to determine the presence of dental caries, tooth wear, gingival inflammation, and missing teeth, thereby minimizing reliance on patient self-awareness or subjective reporting.

Data analysis

All statistical analyses were performed using the Statistical Package for the Social Sciences (SPSS) software, version 21.0. Descriptive statistics, including frequencies, percentages, were used to summarize demographic characteristics, systemic conditions, and oral health findings of the study population. Comparisons between categorical variables were carried out using the Chi-square test to assess differences in oral and systemic health parameters according to gender and age groups. To determine the independent predictors of oral health outcomes—including dental caries, tooth wear, gingival inflammation, and missing teeth—binary logistic regression analyses were conducted. Statistical significance was set at p < 0.05.

Results

The study comprised 314 patients receiving maintenance hemodialysis; Table 1 summarizes the demographic, systemic, and oral health features. The majority of participants were male (58.3%) and either over 60 (41.4%) or between the ages of 41 and 60 (41.1%). 34.1% of patients had hemodialysis for one to two years, whereas 29.9% received it for more than five years. 54.1% of people reported having several systemic comorbidities, with the most prevalent illnesses being diabetes (2.9%) and hypertension (29.3%). Of the group, 11.1% were current smokers and 11.8% were past smokers. Oral symptoms were common, with 46.2% reporting xerostomia, 16.2% reporting taste problems, and 15.9% reporting burning in the mouth. 60.5% of patients had polypharmacy. A significant prevalence of oral illness, including dental caries (74.8%), gingival inflammation (66.6%), tooth wear (54.8%), and missing teeth (82.8%), primarily from periodontal disease (22.0%) and caries (36.6%), was found during a clinical examination.

Table 1 Demographic and oral health characteristics of hemodialysis patients with chronic kidney disease.
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Sex-based differences are presented in Table 2. The duration of hemodialysis was substantially longer in male patients than in female patients (p < 0.001). Males reported xerostomia more commonly than females (23.6% vs. 22.6%, p = 0.016). Males had considerably higher rates of dental caries (49.2%) and tooth wear (37.3% vs. 18.0%, p < 0.001) than females (26.4%, p < 0.001). Males had more anterior involvement than females (26.9% vs. 17.6%, p < 0.001) in gingival inflammation, which also varied considerably by sex. Systemic comorbidities (p = 0.078) and burning-mouth sensation (p = 0.174) did not show any significant gender differences.

Table 2 Comparison of demographic and oral health characteristics between male and female hemodialysis patients.
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Table 3 summarizes age-related differences. Patients over 60 had lengthier hemodialysis stays and the greatest frequency of multiple comorbidities (27.7%, p < 0.001). While xerostomia did not substantially differ across age groups (p = 0.922), taste perception problems were considerably more prevalent in elderly individuals (p = 0.013). The proportion of missing teeth rose significantly with age, affecting 38.1% of patients over 60 and 10.9% of those in the youngest group (p = 0.001). Dental caries and periodontal disease were the most common causes of tooth loss in all age groups (p = 0.001).

Table 3 Comparison of demographic and oral health characteristics among hemodialysis patients across different age groups.
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Multivariable logistic regression analyses identified significant predictors of oral conditions as shown in Table 4. Male gender (OR = 6.00, p < 0.001), present smoking (OR = 35.35, p = 0.007), past smoking (OR = 3.09, p = 0.033), xerostomia (OR = 3.27, p = 0.002), particular timing of taste abnormalities (p < 0.05), and medication usage (OR = 4.70, p = 0.011) were all independently linked with dental caries. Male gender (OR = 3.13, p = 0.001) and xerostomia (OR = 2.45, p = 0.003) were substantially correlated with tooth wear. Gingival inflammation was substantially correlated with xerostomia (p = 0.014), smoking (p = 0.002), and male gender (p < 0.001). Older age (p < 0.001) and xerostomia (OR = 3.67, p = 0.006) were the main risk factors for tooth loss; gender, smoking, and medication usage were not significant predictors (p > 0.05).

Table 4 Logistic regression results for predictors of oral health outcomes.
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Discussion

This study investigated the prevalence and predictors of oral health problems among hemodialysis patients, revealing high rates of xerostomia, dental caries, tooth wear, gingival inflammation, and missing teeth. These results emphasize the need for targeted, multidisciplinary hemodialysis patient care, particularly for high-risk groups including men, the elderly, and those with long-term xerostomia. These results highlight the significant oral health burden experienced by hemodialysis patients with end-stage renal disease (ESRD). The found incidence patterns are consistent with previous research, highlighting the multifaceted effects of CKD and its treatment on the oral cavity, such as impaired taste perception, increased susceptibility to oral infections, and malfunction of the salivary glands. [15, 20].

Xerostomia was reported by over half of the patients in our research (46.2%), which is comparable to rates of 40% to 60% found in previous hemodialysis patient cohorts21,22. Reduced salivary flow due to fluid restriction, the use of phosphate-binding or antihypertensive drugs, and uremic toxicity that impairs salivary gland function are common causes of xerostomia in CKD23. Additionally, Honarmand et al.24 showed that hemodialysis patients’ salivary flow and buffering capacity were significantly lower than those of healthy controls. Xerostomia increases the risk of caries, tooth wear, and gingival irritation in addition to causing oral pain and dry mucosa25,26. In the present study, although xerostomia showed an inverse association in the regression model, this reflects the use of the absence of gingival inflammation as the modeled outcome. Accordingly, individuals reporting xerostomia had lower odds of being inflammation-free, indicating a higher likelihood of gingival inflammation, which is in agreement with previous literature.

16.2% of individuals reported having changed their taste, which is similar to the results of Yu et al.26, who found prevalence rates ranging from 10% to 20%. Changes in zinc and electrolyte balance, as well as the buildup of uremic toxins in saliva, have been associated with hemodialysis and taste changes27. Interestingly, our research revealed that taste problems “all the time” or “soon after dialysis” substantially predicted caries, indicating a behavioral connection wherein altered taste perception may motivate frequent snacking or compensatory sugar consumption. Mucosal dryness and metabolic abnormalities are probably the secondary causes of burning-mouth sensation, which is reported in 15.9% of patients28.

The current study’s dental caries prevalence of 74.8% was very high and consistent with many studies that found caries prevalence rates in hemodialysis populations ranging from 60% to 80%15,29,30,31,32. Male gender, smoking, xerostomia, taste disturbance, and medication usage were found to be independent predictors of caries using logistic regression analysis. Male gender was an independent predictor of dental caries in this study. This association may reflect differences in oral health behaviors and healthcare utilization, including tobacco use, oral hygiene practices, and preventive dental attendance. Biological factors may also contribute, as sex hormones can influence salivary function, immune responses, and the oral microbiome, potentially affecting caries susceptibility. These explanations likely act in combination with broader social and clinical determinants in the hemodialysis population31. The results of Wu et al.32, who found that smoking worsens oral dryness and modifies the oral microbiota in ESRD patients, are consistent with the considerable increase in the likelihood of caries.

More than half of the patients (54.8%) had tooth wear, which was strongly linked to xerostomia and male gender. This is in line with research by Rius-Bonet et al.33, who noted that attrition and abrasion are caused by decreased salivary lubrication and longer masticatory stress. Gingival inflammation was common (66.6%) and more common in smokers and men, indicating weakened host immune responses and poor periodontal health in hemodialysis patients34. Serum inflammatory markers and the degree of periodontal disease have been shown to be closely interrelated, with several studies demonstrating elevated systemic inflammatory biomarkers in individuals with moderate to severe periodontal inflammation. Increased levels of C-reactive protein, interleukin-6, and tumor necrosis factor-α have been reported in association with periodontal tissue breakdown, reflecting the bidirectional relationship between local oral inflammation and systemic inflammatory burden35,36.

This systemic inflammatory response may partly explain the broader health implications of periodontal disease and supports the biological plausibility of the associations observed in the present study. Age and xerostomia emerged as important indicators, and the majority of subjects (82.8%) were missing teeth, mostly from periodontal disease and caries. Missing teeth were more common in older individuals37. In this population, prolonged dialysis, xerostomia, and chronic systemic inflammation could accelerate periodontal disease and tooth loss37.

Despite general agreement between the present findings and several previous studies, inconsistencies in the literature regarding the prevalence and predictors of oral health conditions among hemodialysis patients have also been reported. Some studies have described lower rates of dental caries, periodontal disease, or xerostomia than those observed in the current study, while others have failed to identify significant associations with demographic or clinical variables. These discrepancies may be attributed to differences in study design, sample size, population characteristics, and healthcare settings, as well as variations in oral health assessment methods, including the use of clinical indices versus self-reported measures. Additionally, differences in dialysis duration, comorbidity profiles, medication regimens, dietary habits, and access to preventive dental care across regions may further contribute to variability in reported outcomes. Recognizing these sources of heterogeneity is essential for interpreting existing evidence and underscores the need for standardized assessment approaches in future multicenter studies.

This study has some limitations that should be considered when interpreting the findings. First, the cross-sectional design precludes causal inference between oral health conditions and their associated predictors. Second, although dental caries, gingival and periodontal involvement, and tooth wear were assessed clinically, the assessment focused on identifying the presence of these conditions rather than detailed severity scoring. In addition, objective salivary flow measurements were not performed, and xerostomia was assessed using patient self-report, which may be subject to reporting bias. Third, as the study was conducted in a single province, the generalizability of the findings to other regions or healthcare settings may be limited, and some degree of selection bias cannot be excluded.

Despite these limitations, the study has several strengths, including a relatively large sample of patients undergoing long-term hemodialysis, the use of standardized clinical oral examinations combined with patient-reported data, face-to-face data collection ensuring high response completeness and data quality, and multivariable analysis of a broad range of oral health conditions and demographic, behavioral, and clinical predictors.

Conclusions

This study demonstrates a substantial burden of oral health conditions among patients undergoing hemodialysis, including xerostomia, taste alterations, dental caries, tooth wear, gingival inflammation, and tooth loss. Several demographic, behavioral, and clinical factors—such as male gender, older age, smoking, xerostomia, taste disturbances, and medication use—were identified as significant predictors of these conditions. These findings underscore the complex and multifactorial nature of oral disease in patients with end-stage kidney disease and highlight the importance of comprehensive assessment of oral health status within this population.

Clinical implications

The findings of this study highlight the need for greater integration of oral health assessment into the routine care of patients undergoing hemodialysis. Early identification and management of xerostomia, taste alterations, dental caries, and periodontal conditions may help reduce oral discomfort, improve nutritional intake, and enhance quality of life in this vulnerable population. Collaboration between nephrology and dental care providers is essential to promote preventive oral healthcare, patient education, and timely referral, particularly for individuals with identified risk factors such as smoking, xerostomia, and advanced age.