Study design and ethics

This cross-sectional study incorporated both descriptive comparison of stakeholder attitudes and analytical modeling to examine associations between individual-level factors and SCCD attitudes. It was carried out in compliance with the Helsinki declaration and carried out in two phases with approval from the Tehran University of Medical Sciences Ethics Committee. In the first phase which took place between March 10th and June 30th 2019, dentists working in CHCs across Tehran Province were invited to participate (ethics code: IR.TUMS.DENTISTRY.REC.1397.174). Building on this, the second phase took place between July 1^st and August 30th 2020, when data were gathered from dental patients visiting CHCs in Tehran Province (ethics code: IR.TUMS.DENTISTRY.REC.1399.018). Written informed consent was obtained from both groups following the explanation of research objectives and putting emphasis on voluntary participation, participant anonymity, and data confidentiality. It was also pointed out that completing the questionnaire meant informed consent to participate. Consent for publication was also obtained.

Setting

Iran’s primary healthcare system is organized through a tiered network in which village-based Health Houses provide first-level services, while rural and urban Comprehensive Health Centers (CHCs) serve as key primary care facilities at higher levels of care. CHCs have a central role in delivering preventive, educational, family health, vaccination, and environmental health services, and provide broad urban and rural population coverage [19,20].

For the dentist sample, all CHCs in Tehran province served as the study setting. Tehran province was selected because of logistical feasibility, high population density, and the inclusion of Tehran city, the capital of Iran.

For the patient sample, three CHCs in Tehran province were randomly selected using a random number generator. The selected CHCs were Farmanfarmaian on Azarbayjan Street and Ayat and Imam Hassan Mojtaba in the Khaniabad neighborhood.

Sample

Eligible participants included dentists working in CHCs across Tehran Province during the study period, and dental patients aged 18 and over attending CHCs in Tehran City. Patients aged 18 years and older were included because 18 is the legal age of adulthood in Iran, permitting independent informed consent without parental or guardian involvement. In addition, inclusion of underage individuals would have introduced developmental and behavioral considerations specific to adolescent smoking and oral health that were beyond the scope of the present study. Therefore, restricting the sample to adults ensured ethical appropriateness and conceptual consistency.

For patients, the minimum required sample size was estimated to be 367 using the results of a pilot study (with a sample of 30) with a confidence interval of one proportion option in PASS 11 software, considering α = 0.05 (probability of type I error), p= 0.65 (estimated proportion of the desired trait), and d = 0.1 (acceptable error in estimating the desired ratio). Due to the selected centers’ comparable patient loads and patient demographic compositions, the research team decided that equal numbers of participants would be recruited from each center. To account for potential non-response and ensure adequate power, slightly more participants were recruited, resulting in 380 completed questionnaires.

For dentists, an estimate of the minimum required sample size for the multiple linear regression was conducted for 7 potential explanatory variables with a target power of 80%, a two-tailed alpha of 0.05, and the ability to detect a small-to-medium effect size (Cohen’s f² = 0.075, corresponding to an R² of 0.07), a minimum required sample size of 163 dentists was calculated to ensure adequate power. However, the total number of dentists working in CHCs in Tehran province at the time of the study was 188. Given this relatively small and finite target population, a census approach was adopted to enhance representativeness, minimize sampling bias, and maximize statistical power by inviting all eligible dentists to participate.

Procedure

After coordination with the CHC managers, one of the investigators personally visited the designated centers. The investigator explained research objectives and, as outlined previously, obtained written informed consent from the participants. The investigator then distributed the questionnaires and was available to clarify any ambiguities, and also to collect the completed questionnaires. The procedure was identical for dentists and patients.

Instrument and measures

The research instruments for dentists and patients were self-administered Persian questionnaires consisting of two sections addressing individual-level factors and attitudes toward SCCD (English translations are provided in Supplementary Files 1 and 2). The attitude items for both of these questionnaires were adapted from a previously validated questionnaire developed for primary care dental settings [21]. In the original study [21], the questionnaire underwent a validation process prior to its use. Face validity was examined by a group of 10 dentists together with an expert panel consisting of six community oral health specialists and one epidemiologist, who evaluated the clarity, wording, response formats, and overall readability of the items. Content validity was subsequently assessed by the same panel through ratings of each item’s relevance, simplicity, clarity, and necessity using a four-point scale, resulting in a scale content validity index of 0.96. Reliability was evaluated using a test–retest approach in which the questionnaire was administered twice to a subset of participants with a two-week interval between administrations. Item-level agreement coefficients ranged from 60% to 97.5%.

Because the attitude items were adapted from an instrument that had previously undergone formal validation, the present study did not repeat the full validation process. Instead, the adapted questionnaires were piloted among 15 dentists and 15 patients from the target population to confirm their suitability for the study context and to ensure that the items were clear, relevant, and easily understood. Internal consistency was then recalculated for the adapted instruments using Cronbach’s alpha. The dentist questionnaire demonstrated good internal consistency (α = 0.874). For the patient questionnaire, internal consistency was excellent for the “SCCD effectiveness” domain (α = 0.940) and acceptable for the “oral symptoms as motivators” domain (α = 0.729), whereas the “dentist SCCD competence” domain showed limited internal consistency (α = 0.231). Therefore, findings related to this latter domain were interpreted cautiously.

The individual-level characteristics recorded for patients and dentists were treated as explanatory variables in the present study. For patients, these variables included age, gender, education, occupation, cigarette, hookah, and pipe smoking status, having a smoking family member, and willingness to quit using smoking cessation counseling delivered by dentists (SCCD). For dentists, the variables included age, gender, years since graduation, practice location, employment status at the community health center (CHC), cigarette, hookah, and pipe smoking status, and having a smoking family member (yes/no).

Questions exploring patients’ and dentists’ attitudes were used to construct the study outcome variables as described below.

Patient SCCD attitudes

This construct represented patients’ overall perceptions of receiving SCCD. It was measured using 12 items rated on a 5-point Likert scale ranging from “strongly disagree” (1) to “strongly agree” (5). By summing the responses, the total score ranged from 12 to 60, with higher scores indicating more positive attitudes toward SCCD. This variable is referred to as overall patient SCCD attitudes. The construct comprised three domains:

1. A. Dentist SCCD competence: This domain assessed patients’ perceptions of their dentist’s competence in providing smoking cessation counseling. It was measured using 7 Likert-scale items (items 1–7 of the main questionnaire in Supplementary File 1), each scored from 1 to 5, yielding a total score range of 7–35.
2. B. SCCD effectiveness: This domain evaluated patients’ beliefs regarding the effectiveness of SCCD in helping them quit smoking. It was measured using 3 items (items 8–10 of the main questionnaire in Supplementary File 1), each scored from 1 to 5, producing a total score range of 3–15.
3. C. Oral symptoms as motivators: This domain assessed the extent to which patients perceived oral symptoms such as yellowed teeth and bad breath as motivations for quitting smoking and engaging in cessation counseling. It was measured using 2 items (items 11–12 of the main questionnaire in Supplementary File 1), each scored from 1 to 5, with total scores ranging from 2 to 10.

Dentist SCCD attitudes: This construct represented dentists’ perceptions regarding the provision of SCCD, including perceived professional responsibilities, their role as health role models, perceived barriers to providing SCCD, the perceived importance of smoking cessation counseling, the need for further training, and confidence in delivering SCCD. The construct was measured using 16 items rated on 5-point Likert scales ranging from “strongly disagree” (1) to “strongly agree” (5). The summed score ranged from 16 to 80, with higher scores indicating more positive attitudes toward SCCD provision.

Statistical analyses

Data entry and analysis were performed using SPSS software (version 24 SPSS for Windows). Descriptive statistics were reported as means and standard deviations for continuous variables and frequencies and percentages for categorical variables.

For each study group, the individual-level factors were categorized for analysis based on their frequency distributions and prior relevant literature [21,28]. For patients, age was grouped as <39 and ≥39 years; occupation as employed (including governmental, non-governmental, and self-employed) and unemployed (including housekeepers, retirees, and those without employment); education as non-academic (high school diploma or lower) and academic (bachelor’s degree or higher); and smoking status as non-smoker (never or former smoker) and smoker (current smoker in any form). For dentists, age was categorized as <35 and ≥35 years; years since graduation as <5 and ≥5 years; employment status at CHCs as governmental/contractual versus official/other; and smoking status as non-smoker versus smoker using the same definitions.

For patients, independent samples T-tests were used to compare mean attitude scores across individual-level factors. Multiple logistic regression (Enter method) was then used to examine associations between categorized attitude domains and individual-level variables. Attitude scores were dichotomized at their mean values to distinguish less favorable versus more favorable attitudes (below and above 41.3 for overall SCCD attitudes, below and above 24.8 for attitudes toward dentist SCCD competence, below and above 9.6 for attitudes toward SCCD effectiveness, and below and above 6.8 for attitudes toward oral symptoms as motivators). Willingness to quit using SCCD was analyzed among smoking patients only.

For dentists, simple linear regression analyses were first performed to identify variables associated with SCCD attitude scores. Variables with p < 0.20 were entered into a multiple linear regression model using the Forward method. Statistical significance was set at p < 0.05 for all tests.

Patient and dentist attitudes toward SCCD

To address the first study objective, descriptive analyses were conducted to compare overall and item-level SCCD attitudes between primary care dentists and patients.

On average, dentists scored 70.2% of their maximum possible SCCD attitude score (mean = 56.2, SD = 9.3), whereas patients scored 44% of their maximum SCCD attitude score (mean = 26.4, SD = 5.9).

Fig 1 illustrates both consensus and stark discrepancies in attitudes toward SCCD. Highest agreement was observed in the foundational step, with nearly all dentists (90.5%) and most patients (83.4%) expressing support for asking patients about smoking. However, the largest perceptual gap was exposed regarding the utility of providing information: only 5.6% of dentists agreed with explaining smoking risks, in sharp contrast to 77.6% of patients. This divide was further reflected in expectations, as two-thirds of dentists (63.0%) thought most smokers would not quit despite SCCD, compared with only one-third of patients (33.7%).

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Fig 1. Proportions of primary care patients (n = 380) and dentists (n = 180) expressing favorable attitudes toward SCCD in Tehran, Iran.

^a Smoking cessation counseling by dentists. ^b In this figure, which illustrates item-level differences in attitudes between Tehran primary care a) dentists and b) patients, responses of ‘Agree’ and ‘Strongly agree’ to the attitude items were combined and classified as “Favorable”, while ‘Neutral,’ ‘Disagree,’ and ‘Strongly disagree’ were combined and classified as “Unfavorable”. Legend: a) Blue bars represent the percentage of dentists with favorable attitudes toward each item. B) Yellow, orange, and red bars depict patients’ favorable attitudes across different domains: yellow reflects perceptions of dentists’ competence in providing SCCD, orange reflects perceptions of SCCD effectiveness, and red reflects perceptions of oral symptoms as motivators for quitting.

https://doi.org/10.1371/journal.pone.0354366.g001

Individual-level determinants of patients’ SCCD attitudes

To address the second study objective, regression analyses were conducted to identify individual-level determinants of SCCD attitudes among both stakeholder groups.

As demonstrated in Table 2, non-smoking patients were more likely to have positive attitudes toward SCCD effectiveness than smokers (OR = 1.52, p = 0.049) and patients without a smoking family member were more likely to have more negative views of SCCD effectiveness compared to those with a smoking family member (OR = 0.61, p = 0.021). Moreover, employed patients were more likely to consider symptoms as motivators for quitting (OR = 0.46, p = 0.001) than unemployed ones.

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Table 2. Associations between SCCD^† attitudes and individual-level factors among primary care patients in Tehran, Iran (n = 380).

https://doi.org/10.1371/journal.pone.0354366.t002

As shown in Table 3, among smoking patients, employed patients demonstrated more willingness to quit using SCCD (OR = 0.43, p = 0.010) compared to unemployed ones.

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Table 3. Willingness to quit using SCCD† by individual-level factors among smoking primary care patients in Tehran, Iran (n=186).

https://doi.org/10.1371/journal.pone.0354366.t003

Individual-level determinants of dentists’ SCCD attitudes

Bivariate associations between individual-level factors and dentists’ SCCD attitude scores are presented in the S1 Table. According to this, dentists who had graduated more than five years prior (MD = −3.0, p = 0.049), those working in Tehran city (MD = 3.6, p = 0.013), and non-smoking dentists (MD = −6.2, p = 0.003) demonstrated significantly more positive attitudes toward SCCD.

Next, multiple linear regression tests were conducted to continue addressing the second study objective. These tests demonstrated that non-smoking dentists were more likely to demonstrate positive SCCD attitudes than smoking dentists (B = 5.99, 95% CI: 1.84 to 10.13, p = 0.005) and dentists practicing in bordering towns were more likely to demonstrate negative SCCD attitudes than dentists in Tehran city (B = −3.24, 95% CI: −6.04 to −0.43, p = 0.024).

Strengths and limitations

The present study has several limitations that should be considered when interpreting the findings. Its cross-sectional design precludes causal inference, and self-reported measures may introduce social desirability bias. Dentists were recruited by census and were predominantly female recent graduates, reflecting Iran’s Ministry of Health workforce allocation to urban primary care centers; as this group may be more health-conscious, their overrepresentation may limit generalizability and inflate positive SCCD attitudes. A temporal gap between dentist (2019) and patient (2020) data collection, due to COVID-19-related constraints and reduced dental attendance, may have influenced patients’ SCCD attitudes. Additionally, the dentist SCCD competence domain showed low internal consistency in the present sample, suggesting that the items grouped under this domain may not have captured a single homogeneous construct, possibly reflecting different aspects of perceived dentist role and competence. Considering the conceptual breadth of the domain and given the theoretical relevance of its aspects to SCCD counseling, we ultimately retained its items to preserve content validity. Nonetheless, findings related to this specific domain should be interpreted cautiously. Despite these limitations, the study makes a meaningful contribution by addressing an evidence gap in an understudied LMIC primary care context, parallel assessment of dentists and patients’ attitudes, and the inclusion of patient attitude domains.

Building on the present study’s findings, targeted strategies can be developed for improving SCCD attitudes in Iranian primary care settings and, with caution, comparable LMIC contexts. Among dentists, given that positive attitudes did not translate into implementation readiness, smokers may benefit from reflective, peer-based attitude-building approaches, while those in rural settings may require remote continuing education, virtual mentorship, and stronger organizational support to enhance confidence and delivery capacity. Among patients, the generally cautious and sometimes skeptical receptivity toward SCCD underscores the need to strengthen its perceived effectiveness and relevance; in this regard, the greater receptivity observed among employed individuals supports integrating workplace-based cessation initiatives that emphasize visible oral health consequences. Additionally, engaging non-smoking patients and family members as SCCD advocates may help reinforce more favorable attitudes toward SCCD among smokers and increase confidence in its effectiveness.

Future studies should examine how workplace contexts influence patient engagement or the viewing of oral symptoms as quitting motivators, how family smoking exposure shapes perceived SCCD effectiveness, and the mechanisms driving rural–urban differences in dentists’ attitudes. Future studies should further evaluate and refine the dentist competence subscale of the patient questionnaire before using it as a standalone measure. Finally, this research should be extended to other regions and populations to improve generalizability.