The current study aims at exploring OHB (toothbrushing; interdental cleaning) and HBM-based determinants (Figure 1) among adult and adolescent ASRs in North-Western Switzerland. The goal of the current observational study is to identify which specific HBM-based determinants may hold the greatest practical relevance for promoting OHBs, and thus need further more rigorous testing in intervention studies towards a better understanding of causality. Ultimately, the insight gained from the current observational and future intervention studies might guide dental professionals in asking focused questions to better support OHB among ASRs.

Eligible participants were: Adolescents aged between 14 and 17 years old, or adults aged 18 and older, who speak Arabic, have permission to stay in Switzerland as ASRs, and live in the states of Zürich, Basel-Stadt, or Basel-Landschaft.

Power calculations were based on 4,634 eligible participants in Zürich, Basel-Stadt, or Basel-Landschaft [34, 35], assuming a 30% response rate. A sample of 284 randomly selected participants was deemed sufficient, accounting for household clustering. This sample size allows detection of an odds ratio (OR) of 2.36 between HBM domains and OHB, with 95% confidence and 80% power.

In the absence of access to a database allowing for population-based recruitment, participants were initially recruited by distributing study flyers in integration centers and dental clinics and thereafter also by snowballing recruitment between September 2024 and March 2025. Interested individuals contacted the study staff by phone for a brief eligibility screening. Appointments were then arranged for eligible and interested participants. They received the informed consent form and a printed and verbal explanation of the study in-person. Following written informed consent, trained study personnel conducted face-to-face, verbally administered surveys with participants using visuals for each response option to aid understanding and accuracy. Responses were securely recorded and stored using the Open Data Kit platform. Questions were asked in Arabic language. Questions were independently translated from English to Arabic and back translated to English by two Arabic speaking members of study staff fluent in English. Available resources did not allow validating the questionnaire, albeit most questions were derived from previously validated and published questionnaires. The comprehensibility of the questions was pilot-tested.

Questions from which outcomes, predictors and covariates were derived are available as Supplementary Material.

Primary outcomes: OHB (oral hygiene behavior), previously defined, was assessed via two self-reported items:

Adequate toothbrushing (toothbrushing at least twice a day versus less frequent)

This cut-off of adequate interdental cleaning is not a gold-standard recommendation. It was informed by previous research suggesting that interdental cleaning several times a week may offer protective benefits, even if not performed daily [36], and by the distribution of responses in our dataset.

Primary explanatory variables: HBM-based determinants [10] of OHB included knowledge; perceived susceptibility of OH diseases; perceived severity of OH diseases; cues to actions; expected social outcomes; perceived benefits of OHB; perceived barriers to OHB and self-efficacy. The adolescents’ and adults’ HBM-based questions were adopted mainly from the oral health behavior questionnaire for adolescents [37] and from other previous research [11, 38–41]. Questions about perceptions of OH care (Swiss healthcare system cares about my wellbeing; Swiss dental care system cares about my wellbeing) and autonomy (I feel that I am in control of the decisions related to my dental health) were added according to findings of the qualitative phase of the Axs2OH project. These constructs have been proposed as relevant context-specific extensions to the HBM in contexts where trust in institutions and perceived control influence health behaviors, particularly among marginalized populations [42–44]. All primary explanatory variables were self-reported during the in-person interview.

Potential confounders: Self-reported socio-demographic characteristics of participants considered as confounders based on a priori evidence included sex, age, and highest achieved educational level. Additional socio-demographic characteristics exhibiting only weak differences in their distribution between adequate and inadequate OHB were unlikely confounding reported associations between HBM-based explanatory variables and OHB. They were therefore merely used for describing the study population: residency permit type and year of arrival in Switzerland.

The participants’ characteristics are presented, stratified by OHB outcome variables, as mean and range for the numerical continuous variables, and as number and percentage for the categorical variables. Participants’ OHB is described as number and percentage with adequate toothbrushing, adequate interdental cleaning, or both. Differences in participant characteristics by toothbrushing and interdental cleaning behavior were examined descriptively using the Wilcoxon rank-sum test for continuous variables and Pearson’s chi-square test for categorical variables, with p-values reported for descriptive purposes only.

A multiphase approach consisting of 3 sequential phases was applied to examine the association between HBM-based variables with the two OHB outcome variables (toothbrushing and interdental cleaning). This phased approach was necessary due to the high number of original HBM-based explanatory variables investigated (k = 40) and the fact that they were in part correlated, in some cases despite belonging to different HBM domains. The multiphase approach additionally allowed identifying high polarity in the responses to some variables, which necessitated reconsidering their utility as targets to improve OHB. In summary, the goal of the sequential process over 3 phases was to identify HBM-relevant constructs and within these constructs specific variables and therefore questions which likely could have the biggest potential impact on ASRs OHB if asked by a dental professional.

Table 1 presents the demographic characteristics of the study sample (300 participants from 151 households), stratified by adequacy of toothbrushing and interdental cleaning. 95% of the study participants were Syrians (data not shown).

53% of participants self-reported adequate toothbrushing behavior but the prevalence of adequate interdental cleaning was substantially lower (35%). Among participants with adequate toothbrushing, around 46% also practiced adequate interdental cleaning. Similarly, around 68% of participants with adequate interdental cleaning also brushed their teeth adequately.

Descriptively, adequate toothbrushing was more common among female and younger participants and participants with secondary or higher education levels, whereas adequate interdental cleaning was more common among participants with higher education and more years since arrival in Switzerland.

The distribution of single question answers by HBM domain is presented in Supplementary Figures S1–S12. In the knowledge domain, at least 93% of participants agreed or strongly agreed that smoking can affect OH and that sugary food and drinks negatively affect teeth. In the perception domain, only 19.7% strongly agreed that the dental system cares about their wellbeing, and over half disagreed or strongly disagreed with feeling in control of the decisions related to their dental health. In the susceptibility domain, at least 60% agreed or strongly agreed that they are susceptible to having dental caries or gum diseases. In the severity domain, 85% of participants considered being unable to eat their favorite foods due to oral diseases as serious or very serious, while 67% perceived being laughed at for OH issues as similarly serious. In the cues to action domain, the vast majority agree or strongly agree that parents (98%) and teachers (84%) have role model function in influencing OHB. In the expected social outcome domain, 69% of participants agreed or strongly agreed that people judge one another based on their teeth, while 96% emphasized the importance of fresh breath in socialization. In the benefits domain, 81.4% of participants agreed or strongly agreed that toothbrushing prevents oral diseases, compared to 59% for interdental cleaning. In the barriers domain, only 9% of participants agreed that they did not know how to brush their teeth, whereas 32% reported not knowing how to perform interdental cleaning. Additionally, 51% felt that their family did not encourage them to brush their teeth, and this figure rose to 68% for interdental cleaning. In the self-efficacy domain, self-efficacy under stress or time pressure was high for toothbrushing (more than 38% quite to very confident), but very low for interdental cleaning (70% not confident).

Self-efficacy (the confidence in one’s ability to successfully perform a specific behavior) is a central determinant of health behavior and a crucial factor in motivating individuals to take an active role in their health. It strongly influences the maintenance of self-management and the adoption of healthy practices [55], including OHB [56].

Self-efficacy in the current study was characterized by having the confidence in adequate toothbrushing and interdental cleaning even in the face of having time constraints or being stressed and anxious was by far most strongly and consistently associated with both OHBs.

These findings on self-efficacy with both OHBs are somewhat parallel to Jönsson et al. work on the effect of individually tailored OHB promotion programs, following a cognitive behavioral approaches (incorporating practical and theoretical knowledge, motivation, self-monitoring and maintenance of the behavior), on the amount of dental plaque that is accumulated on and between the teeth [57].

The final analyses suggested that perceived autonomy on own OH could play a significant role in shaping toothbrushing, but not interdental cleaning practices. Specifically, ASRs who felt more in control of their OH decisions had higher odds of toothbrushing adequately (at least twice a day). This aligns with previous evidence highlighting the role of autonomy in health-promoting behaviors [58].

Established health habits are determined by a profound belief in their benefits [10].

The perceived benefits domain only mattered for interdental cleaning, but not toothbrushing. In fact unexpectedly, this study’s results suggested that perceiving toothbrushing as making the mouth feel better, was associated with lower odds of adequate toothbrushing, reflecting a disconnection between belief/attitude and behavior (e.g., individuals agreeing with this statement but not translating it into action due to some barriers).

In contrast, regarding adequate interdental cleaning (at least each other day), the domain of perceived benefits in general, and several perceived specific benefits were positively associated with adequate practice. Believing that interdental cleaning makes the mouth feel better (unlike toothbrushing) or reduces future dental treatment costs was associated with higher odds of adequate cleaning. Surprisingly on benefits, participants who agreed that interdental cleaning results in fresher breath were less likely to adopt it.

The finding that some perceived benefits of the two OHBs were negatively associated with adequately adopting the respective OHB could be explained by Brown et al.’s conclusion on health behaviors needing self-regulatory skills to be translated into actions [59]. However, this gap between belief/attitude and behavior may be further exacerbated by persistent barriers, which interfere with the ability to act on positive beliefs.

In summary, the evidence on benefits as particular target for promoting OHB was inconsistent and rather weak.

In contrast to perceived benefits, the perceived barrier domain was inversely associated with both OHBs, toothbrushing and interdental cleaning.

Barriers as perceiving toothbrushing being painful, lack of time, and forgetfulness were found associated with reduced odds of toothbrushing adequately. Among the reported barriers to interdental cleaning, not knowing how to clean between the teeth and fearing tooth breakage were both negatively associated with adequate interdental cleaning.

These barriers to OHBs among ASRs could occur due to OH care and OHB experienced in the home country [60, 61] or the accumulation of migration-related stressors. ASRs are subjected to trauma-related mental health issues, rooted in the hardships encountered before the decision of migration and along the migration route, including collective survival concerns, precarious living conditions, and prolonged uncertainty [19]. After migration, mental health challenges are often exacerbated by uncertainty surrounding legal status and social disruption, including loss of community bonds, financial worries, unfamiliar cultural norms and limited access to social support systems [20].

As a result, ASRs may experience reduced financial resources as well as motivation or energy to maintain regular OHBs, particularly in the absence of pre-established health habits, limited OH knowledge, or negative experiences with OH care in their country of origin [21, 22].

Interestingly on barriers to interdental cleaning, participants who reported that interdental cleaning tools are expensive or lacked family encouragement were more likely to clean adequately. It is likely that participants who conduct interdental cleaning, have already purchased the necessary tools, are therefore more aware of their cost than those who do not. At the same time, reporting insufficient family support might reflect a stronger personal conviction about the importance of the habit, which could in turn promote more consistent practice [62].

One of the strengths of this study lies in its multidimensional and theory-driven approach, additionally informed by an embedded qualitative study, as well as its focus on a highly under-researched population. However, its cross-sectional design hinders causal inference. This may have been particularly true for the susceptibility domain, which we therefore excluded in the final variable selection step. The high observed level of knowledge related to sugar and smoking being bad for teeth limited our ability to investigate its potential as target to improve OHB in populations less knowledgeable. Self-reported data harbors the risk of recall and social desirability biases.

Additionally, the sample may not be fully representative of all Arabic-speaking ASRs in Switzerland given that different regions have different health and OH care policies for ASRs. The use of snowball sampling, while necessary for recruitment, further limits generalizability and may introduce bias in both prevalence estimates and confidence intervals.

Finally, due to limited resources and the exploratory nature of the study, we were unable to formally validate the questionnaire in this specific population. Yet, many questions were derived from instruments validated in other populations. In addition, the comprehensibility of the questions was piloted beforehand in the target population. Finally, the large number of questions asked across different HBM-domains combined with the three-phased approach allowed prioritizing constructs and within the constructs variables for further testing.

The current observational study and its limitations point to the fact that the study is hypothesis generating. The priority domains and variables suggested as being relevant in determining OHB in ASRs need further testing in intervention studies that allow assessing causality.

The results suggest that the relevance of promoting OHB in ASRs, a health aspect with potentially broad and beneficial consequences, is high. Self-efficacy, autonomy in decision-making, and selected barriers and benefits might be critical intervention targets with a potential to positively influence OHB. If further confirmed in randomized trials, the results could encourage dental professionals to assess patients’ confidence (self-efficacy), perceived autonomy, and beliefs around benefits and barriers to oral hygiene. Policymakers could strengthen migrant health packages by including OH education and funding preventive services. School-based programs targeting migrant children and their families, as well as integration services offering dental hygiene education and screening, may support long-term improvements.