Study design

This was a descriptive-analytical, cross-sectional study conducted on HIV-positive patients in Tabriz, Iran. All methods were performed in accordance with the Dentistry School of Guilan University of Medical Sciences and Medicine Faculty of Tabriz University of Medical Sciences with the ethical code of (IR.GUMS.REC.1402.443) issued by the Guilan University of Medical Sciences. The sample size for this study was determined based on previous studies assessing oral health outcomes in HIV-positive patients. Considering an expected prevalence of oral health issues of approximately 70% among HIV-positive individuals, with a 95% confidence level and a margin of error of 8%, the minimum required sample size was calculated as 119 participants. The calculation was performed using the following formula for prevalence studies:

where n is the sample size, Z is the standard normal deviate (1.96 for a 95% confidence level), P is the expected prevalence (0.70), and d is the margin of error (0.08). To account for potential dropouts and missing data, a total of 134 participants were recruited. Participants were recruited between January 2024 – November 2024 at the Counseling, Care, and Treatment Center affiliated with Tabriz University of Medical Sciences.

Study population, sampling, and determination method

The study population included all HIV-positive patients with records at the Counseling, Care, and Treatment Center affiliated with Tabriz University of Medical Sciences. Patients selected for the study were those with documented, consistent follow-up visits at the center to receive services. All HIV-positive patients with documented and regular attendance at the center were included in the study, resulting in a final sample of 134 patients. The sample size was determined based on a power analysis to ensure statistical significance in detecting associations between DMFT index and independent variables such as smoking, drug use, education level, and CD4 count. To account for potential dropouts and incomplete data, we included 134 patients in the final analysis. A sample of 134 was chosen based on an expected oral disease prevalence of 70%, with 8% margin of error and 95% confidence level.

Participant characteristics and inclusion/exclusion criteria

HIV-positive adults (≥ 18 years) under continuous care at the center for at least three months were included. Patients unable to consent or complete the examination were excluded. Inclusion criteria for the study were as follows: adult HIV-positive patients (18 years or older) who were under continuous medical care at the center for at least three months. Exclusion criteria included patients under 18 years of age, individuals who declined participation or lacked the physical or cognitive ability to complete the questionnaire, and those who did not complete the examination or questionnaire. Exclusion criteria included patients under 18 years of age, individuals who declined participation or lacked the physical or cognitive ability to provide informed consent, and those with severe systemic conditions preventing oral examination. Participants who partially completed the questionnaire were not excluded but were analyzed separately for missing data.

Clarification on the origin of the variable table

The questionnaire used in this study was not directly adapted from previously published studies but was developed based on widely accepted frameworks and guidelines for health research in Iran. The design of the variables and their categorization was guided by resources such as:

• Zhivar Amoozan Educational Resources: A resource for completing research proposal components, including variable tables, with detailed explanations on scales and roles of variables​.

• Pajouheshyar Research System: A platform widely utilized in Iranian medical research for organizing and presenting variables in proposals​.

• Meditorha Resources on Research Variables: Provides detailed insights into the categorization and operationalization of variables in medical research​.

Although the questionnaire was designed specifically for this study, its structure is based on these foundational methodologies to ensure consistency and validity.

Data collection procedures and tools

Baseline information, including age, education level, occupation, HIV transmission route, ART initiation date, and type of antiretroviral medication, was gathered from the data management software and patient records at the counseling center. Examination sessions and questionnaire completion were organized in coordination with center administrators, with patients invited to participate. After explaining the study’s objectives and assuring participants that no personal identifiers were necessary, informed consent was obtained from each participant. Oral health assessments included the DMFT (Decayed, Missing, and Filled Teeth) index and periodontal disease evaluation using a periodontal probe. Oral lesions were identified through visual inspection of the oral cavity under lighting conditions similar to those used in a dental unit. Patients with dentures were excluded from DMFT and periodontal disease assessments. A structured questionnaire was used to collect data on demographic characteristics, oral health behaviors, and self-reported barriers to dental care. The questionnaire was adapted from previously validated instruments used in HIV-related oral health research and modified to align with the study’s objectives and the Iranian healthcare context. The questionnaire covered socioeconomic factors (education, income, insurance status), health behaviors (smoking, substance use, oral hygiene practices), and access to dental care. Additionally, it included self-reported oral health conditions, such as gingival bleeding, tooth loss, and mucosal lesions, which were later confirmed by clinical examination. Validation Process: The questionnaire underwent content validation by three oral health experts and two infectious disease specialists, ensuring relevance and clarity. A pilot study involving 15 HIV-positive patients was conducted to assess comprehensibility and response consistency. Minor modifications were made based on participant feedback before full-scale implementation.

Data collection instruments

Data sources included the center’s data management software, patient files, structured interviews, completed questionnaires, and clinical examinations, all of which provided essential information for the study. Data collection was conducted by two trained and calibrated dental examiners with expertise in oral health assessment among immunocompromised patients. Prior to the study, the examiners underwent a training session to ensure standardization in data collection, including the assessment of DMFT index and periodontal diseases. Inter-examiner reliability was assessed. Additionally, periodic intra-examiner calibration was performed to maintain consistency throughout the study.

Oral health assessment and indices used

Examiners were trained and calibrated; periodic intra-examiner reliability was ensured. The Decayed, Missing, and Filled Teeth (DMFT) index was selected as the primary measure of oral health status in this study due to its widespread use in epidemiological studies assessing dental caries and treatment needs. The DMFT index is a well-validated and standardized tool endorsed by the World Health Organization (WHO) for evaluating caries experience in populations.

While the WHO Dentition Status Index (2013 Oral Health Assessment Form for HIV Oral Manifestations) provides a broader classification of oral health status, including lesion-specific evaluations, the DMFT index was chosen for this study because:

• It provides a quantitative measure of dental caries burden, which is a significant concern in HIV-positive individuals.

• It allows for comparability with prior epidemiological studies on oral health in HIV populations.

• It aligns with the study’s objective, which focuses on assessing the relationship between HIV infection, ART duration, and dental caries burden.

However, additional oral health parameters, such as periodontal disease prevalence and mucosal lesions (e.g., candidiasis, leukoplakia, and ulcers), were also documented to ensure a comprehensive assessment of oral health status among HIV-positive patients. Periodontal disease was evaluated using the World Health Organization’s Community Periodontal Index (CPI). This index assesses gingival health, periodontal pockets, and loss of attachment, allowing for standardized classification of periodontal status in epidemiological studies. The use of the CPI ensured that our findings are comparable with other studies in similar populations.

Study variables

Variables included demographic, clinical (CD4, ART duration), and behavioral (smoking, drug use) factors. The primary outcome was DMFT score. The primary variable of interest was the DMFT (Decayed, Missing, and Filled Teeth) index. Independent variables assessed for correlation with the DMFT index included smoking status, drug use, education level, and CD4 count. Additional demographic and clinical variables, such as age, gender, and duration of ART, were also evaluated. The main study variables are presented in the Table 1.

Validity and reliability

To assess the content validity index (CVI) of the questionnaire, the Waltz and Basel method was applied, involving a panel of six experts: two oral disease specialists, one endodontist, one social dentistry specialist, one infectious disease expert, and one epidemiologist. These specialists evaluated the relevance, simplicity, clarity, and transparency of each question on a Likert scale. Content validity was calculated as the ratio of experts who rated each question as 3 or 4 to the total number of experts; questions scoring below a CVI of 0.79 were excluded. Internal consistency was verified using Cronbach’s alpha, with support from a biostatistician, and was processed in SPSS software.

Data analysis

Data were analyzed using SPSS version 26. Descriptive statistics (mean, standard deviation, frequencies, and percentages) were used to summarize demographic and clinical characteristics. Bivariate analyses, including Pearson’s correlation and chi-square tests, were conducted to assess associations between the DMFT index and independent variables such as smoking, drug use, education level, and CD4 count. Multivariate linear regression was performed to identify independent predictors of DMFT scores, adjusting for potential confounders. Statistical significance was set at p < 0.05, and 95% confidence intervals (CIs) were reported. To minimize selection bias, all eligible patients with regular visits were included. Information bias was reduced by using validated tools and trained examiners. Recall bias was minimized by collecting most data from clinical records. Quantitative variables like DMFT, CD4 count, and age were analyzed as continuous data. Categorical variables (e.g., smoker/non-smoker) were grouped based on clinical relevance. Pearson’s correlation, chi-square, and multivariate linear regression were used to assess associations between DMFT and independent variables. Missing data were analyzed separately; cases with incomplete clinical records were excluded from regression. Significance was defined as p < 0.05. No sampling weights or sensitivity analyses were applied.