Tongue Cleaning Habits and related Factors among Medical Students in 2024: A Cross-sectional Study

1. INTRODUCTION

Oral hygiene is a fundamental aspect of overall health and well-being, playing a crucial role in preventing dental diseases and their associated systemic health issues [1]. While tooth brushing and flossing are frequently emphasised in oral health education, tongue cleaning remains a relatively neglected component despite its significant contribution to maintaining oral microbial balance and reducing halitosis [2]. The dorsal surface of the tongue is covered with numerous filiform papillae that provide an ideal environment for bacterial accumulation, food debris, and desquamated epithelial cells [3]. This accumulation, commonly referred to as tongue coating, is a significant source of intraoral halitosis and has been linked to the development of periodontal disease [4]. Additionally, regular tongue cleaning has been linked to improved taste perception and enhanced subjective oral hygiene [5].

Despite these benefits, adherence to tongue-cleaning practices remains low in many populations. For instance, Kishi et al. (2012) reported that only 35.4% of healthy adults in Japan engaged in tongue cleaning [6]. Matsuda et al. (2019) found that only 18.4% of respondents in Fukui Prefecture practised daily tongue cleaning with a toothbrush, while Yadav et al. (2023) reported a higher rate of 53.8% among patients in Kathmandu, Nepal, although the practice remained inconsistent [7, 8]. These findings suggest that even where awareness may exist, sustained and technically adequate practice is often lacking. Globally, most studies on tongue hygiene remain limited in scope, usually focusing narrowly on prevalence rates [6]. More nuanced aspects, such as the frequency of cleaning, the type of tools used, the technique, and perceived barriers like the gag reflex, have not been fully explored. In particular, few studies have utilised health behaviour theories to analyse how individual attitudes, perceptions, and contextual influences shape tongue-cleaning habits.

In the Vietnamese context, tongue cleaning is rarely addressed as a standalone behaviour within oral hygiene practices. To date, no published study has systematically investigated tongue-cleaning habits or related behavioural factors in the Vietnamese population. This study is, therefore, the first to explore these behaviours among medical students, a group expected to exemplify healthy practices and serve as future providers of oral health education [9]. Furthermore, there is a critical need to understand how factors, such as gender, perceived cleanliness, knowledge-seeking behaviours, and physiological responses (e.g., the gag reflex), influence tongue-cleaning practices. Gaining such insights among healthcare students not only enriches the local evidence base but also supports the design of more comprehensive and behaviorally informed oral health education strategies. Accordingly, this study aims to investigate the tongue-cleaning habits among medical students and to identify the demographic and behavioural factors associated with these habits.

2. MATERIALS AND METHODS

2.1. Study Design and Participants

A descriptive cross-sectional study was conducted at Hanoi Medical University (HMU), Hanoi, Vietnam. The study population included undergraduate students currently enrolled at HMU at the time of data collection. Participants were recruited using a convenience sampling approach across all academic years. Students were eligible for inclusion if they were actively enrolled and had voluntarily consented to participate, and were between 18 and 24 years of age. Exclusion criteria included postgraduate students, individuals not enrolled at HMU, those who declined consent, and students with significant physical or mental health conditions that might interfere with participation.

Recruitment and data collection were conducted over two weeks in December 2024. Data were obtained using a self-administered structured questionnaire.

The sample size of 961 students was determined based on both statistical requirements and practical considerations. Using the standard formula for estimating a single population proportion in cross-sectional studies:

With:

• Z = 1.96

• p = 0.5

• d = 0.05

The minimum sample size required was estimated to be 385 students. However, to improve statistical power and account for potential issues, such as non-response, incomplete answers, and sampling variability across academic years and majors, the research team intentionally aimed to recruit a much larger sample. The final sample consisted of 961 respondents, surpassing the minimum required by nearly 2.5 times. This larger sample size enabled more accurate prevalence estimates, allowed for subgroup analyses, and supported the use of multivariate regression modelling with multiple predictors. Additionally, the expanded sample enhanced the generalisability of the findings within the university population. This approach reflects best practices in observational health research, where larger-than-minimum samples are generally used to increase the robustness and reliability of results.

3. RESULTS

A total of approximately 3,000 undergraduate students were enrolled at Hanoi Medical University during the data collection period and were considered potentially eligible for the study. Of these, around 1,050 students were approached via convenience sampling. After applying inclusion and exclusion criteria, 961 students voluntarily consented to participate and completed the questionnaire thoroughly. No participants were lost to follow-up or excluded from analysis due to missing or incomplete data.

Figure 1 presents the demographic characteristics of the study participants. Among the 961 undergraduate students surveyed, 46.2% were male and 53.8% were female, indicating a slightly higher proportion of female participants. Regarding age distribution, the majority of respondents (81.3%) were between 18 and 20 years old, whereas 18.6% were above 20 years old.

Figure 2 illustrates that among the respondents, 65.76% reported practising tongue cleaning. Regarding the gag reflex, 70.42% of participants experienced a gag reflex during tongue cleaning. In terms of cleaning technique, 56.03% of participants reported cleaning the entire surface of the tongue.

Figure 3 illustrates the frequency of tongue cleaning per week among the participants who practised tongue cleaning. The most common frequency reported was daily cleaning, with 47.81% of participants cleaning their tongue every day. Additionally, 24.45% of participants cleaned their tongue one or two days per week, 17.08% cleaned three or four days per week, and 10.66% cleaned five or six days per week.

Figure 4 displays the types of tools used by participants for tongue cleaning. Among those who practiced tongue cleaning, the most commonly used tool was the toothbrush, reported by 51.8% of participants. This was followed by tongue scrapers, used by 30.0%, and tongue brushes, used by 18.2%.

Table 1 showed that female students were significantly more likely to practice tongue cleaning (p < 0.001), report gag reflex (p < 0.05), and clean the entire tongue (p < 0.05). Tongue-cleaning practice was also associated with a stronger desire for information (p < 0.001), better oral hygiene practices (p < 0.001), regular dental check-ups (p < 0.01), and a higher perceived level of oral cleanliness (p < 0.001). Gag reflex was further linked to beverage consumption (p < 0.05), while cleaning the entire tongue was also related to beverage consumption (p < 0.05) and dental check-ups (p < 0.05). Other variables, including age and breath perception, showed no significant associations.

Table 2 showed that tongue-cleaning frequency was not significantly associated with gender, age, desire for information, oral hygiene methods, beverage consumption, or gag reflex (all p > 0.05). However, students who attended regular dental check-ups cleaned their tongue more frequently (p < 0.05). Breath perception showed a strong association, with individuals who perceived no bad breath being more likely to clean their tongue more often (p < 0.001). Similarly, higher perceived oral cleanliness was associated with a greater frequency (p < 0.001). Cleaning the entire tongue was also strongly associated with a higher frequency of tongue cleaning (p < 0.001).

Table 3 illustrates the multivariate logistic regression model used to analyze the relation between tongue-cleaning practices, gag reflex percentage, tongue-cleaning methods, and the related factors. Under the same conditions for other variables, the following groups are more likely to have tongue-cleaning practice: “Females (95%CI:1.39-2.45)”, “Requiring information on tongue hygiene (95%CI: 1.27-2.33),” “Using tools other than a toothbrush for oral hygiene (95%CI: 1.71-4.09)” and “Having a clean oral cavity (95%CI: 1.21-2.15).”

The following groups have a higher tendency to experience gag reflex: “Females (95%CI: 1.16-2.37),” “Having consumed colored and alcoholic beverages in the past six months (95%CI: 1.11-3.22).”

Participants who used tools other than a toothbrush were significantly more likely to clean the entire tongue (OR = 2.07, 95% CI: 1.20–3.56, p < 0.01), as were those with higher cleaning frequency (OR = 1.52, 95% CI: 1.32–1.74, p < 0.001). Conversely, those using toothbrushes for tongue cleaning had a lower likelihood of complete tongue cleaning (OR = 0.42, 95% CI: 0.21–0.84, p < 0.05).

Table 4 illustrates that the multivariate linear regression model indicates that using tools other than a toothbrush for oral hygiene increases tongue-cleaning frequency by 0.47 units, having bad breath decreases it by 0.59 units, and perceiving a clean oral cavity increases it by 0.22 units. Using specialized tongue-cleaning tools decreases the frequency of tongue cleaning by 0.14 units, whereas cleaning the entire tongue increases it by 0.59 units.

Table 5 illustrates the multivariate logistic regression model used to analyse the usage rates of different tongue-cleaning tools and related factors. Under the same conditions for other variables, participants who had these aspects: “applying various tools for oral hygiene (95%CI:0.10-0.47)”, “having visited a dentist in the past six months (95%CI:0.35-0.92)”, and “cleaning the entire tongue (95%CI:0.31-0.62)” were less likely to choose a toothbrush for tongue cleaning. Cleaning the whole tongue increases the possibility of selecting tongue scrapers (95%CI:1.20-2.94) and tongue brushes (95%CI:1.16-2.45). Individuals who experience a gag reflex tend to avoid choosing tongue brushes for tongue cleaning (95%CI:0.42-0.89). Lastly, students who clean their tongue more frequently tended to use toothbrushes (95%CI:1.05-1.39).

4. DISCUSSION

This study reveals a concerning gap in tongue-cleaning behaviour among medical students, despite their expected role in modelling and promoting oral health. Only 65.76% of participants reported practising tongue cleaning, and less than half (47.81%) did so daily. At the same time, this prevalence is higher than the 18.4% daily rate found in Japan (Matsuda et al., 2019) and above the 41% reported in Italy (Abati et al., 2023) [7, 10]. The discrepancy across countries likely reflects differences in cultural norms, exposure to health education, and public health messaging. The finding that even medical students demonstrate insufficient adherence suggests that tongue hygiene is less effective than tooth brushing and flossing.

Gender differences emerged as notable predictors of tongue-cleaning behaviour. Female students were more likely to clean their tongues (OR = 1.84), which may reflect a higher level of health consciousness and aesthetic motivation. This aligns with broader gender-based health behaviour research, where women tend to engage more in preventive health practices, possibly due to a greater internalisation of health norms, societal expectations about cleanliness and self-care, and heightened sensitivity to social cues, such as perceived breath odour [11]. Additionally, aesthetic concerns related to oral appearance and freshness may further motivate females to adopt more comprehensive oral hygiene routines, including tongue cleaning.

Students who expressed a desire for more information about tongue cleaning (OR = 1.72) and those who perceived their mouths as cleaner after cleaning were more likely to engage in the behaviour regularly. According to the Health Belief Model, information-seeking behaviour often reflects increased perceived susceptibility and awareness, which can motivate preventive practices [12]. Individuals actively seeking knowledge may view tongue cleaning as a preventive measure that enhances both their health and social confidence, thereby increasing their likelihood of engaging in the behaviour [13]. Similarly, the perception of oral cleanliness after cleaning acts as a reinforcing experience that enhances self-efficacy and perceived benefits, two key drivers of sustained health practices. Conversely, participants who reported halitosis were less likely to clean regularly, possibly reflecting low self-efficacy or frustration with perceived ineffectiveness [14]. These findings support the Health Belief Model’s emphasis on perceived benefits, self-efficacy, and cues to action as determinants of health behaviour [12].

Participants with comprehensive oral hygiene routines were more likely to clean their entire tongues since this technique has been shown to reduce tongue coating and volatile sulfur compound (VSC) levels more effectively than cleaning only the anterior region [2]. This clustering of health behaviours reflects the phenomenon of behavioural co-occurrence, where individuals who adopt one health-promoting behaviour are more likely to embrace others [15]. It also suggests possessing stronger perceived behavioral control and intention, as framed in the Theory of Planned Behavior, enabling individuals to translate health knowledge into sustained action [16]. Frequent engagement with multiple oral care practices may enhance exposure to dental professionals and educational resources, thereby reinforcing the importance of tongue cleaning, as well as the use of accurate tongue-cleaning techniques [17].

The ideal frequency and duration for effective tongue cleaning remain uncertain, therefore, further studies should focus on this topic [18]. However, the results demonstrate that employing a whole-tongue cleaning technique significantly increases the frequency of cleaning (β = 0.59, p < 0.001). From a behavioral science perspective, this effect likely results from enhanced perceived competence, which reinforces motivation and habit formation [19]. According to Cognitive Evaluation Theory, when individuals perceive themselves as skilled in a task, their intrinsic motivation increases, making repetition more likely [19]. Similarly, participants who practiced multiple oral hygiene behaviors reported a higher frequency of tongue cleaning (β = 0.48, p < 0.05). This corresponds with the concept of behavioral clustering, where engagement in one health-promoting activity increases the likelihood of others [20]. A positive perception of oral cleanliness after tongue cleaning was also a significant predictor (β=0.22, p<0.05), reinforcing the idea that self-efficacy and immediate feedback are crucial for maintaining healthy behaviors. Conversely, participants who reported halitosis cleaned significantly less frequently (β = –0.59, p < 0.001), likely due to discouragement stemming from perceived ineffectiveness. Lastly, the use of specialized tongue-cleaning tools was unexpectedly associated with a slight decrease in frequency (β=–0.14, p<0.05), suggesting that practical discomfort or unfamiliarity may deter regular use of these evidence-based instruments.

Despite the demonstrated effectiveness of tongue scrapers and specialized brushes, most students (51.8%) used regular toothbrushes for cleaning their tongues. This preference likely reflects accessibility, familiarity, and lack of formal instruction [21]. Prior research has shown that toothbrushes are less effective than scrapers in removing tongue coating and reducing volatile sulfur compounds [22]. The choice of tool was further associated with technique and prior experience. Those with good technique were less likely to use toothbrushes (OR = 0.21) and more likely to adopt specialized tools. Dental consultations appeared to influence behavior as well, since students who had visited a dentist recently were less reliant on toothbrushes (OR = 0.57), suggesting professional advice may shape tool selection by increasing awareness, providing hands-on instruction, and reinforcing behavioral control through trusted guidance [6]. The presence of a gag reflex (OR = 0.61, p < 0.05) was associated with lower use of tongue brushes, indicating a physiological barrier. Implementing stepwise desensitisation techniques, such as gradual posterior progression, can help students overcome this obstacle. Finally, participants who maintained comprehensive oral hygiene habits were over five times more likely to use scrapers (OR = 5.12, p. <0.01) and significantly less likely to use toothbrushes (OR = 0.21, p < 0.001). This suggests that oral health literacy and confidence are crucial in informing the selection of evidence-based tools.

The gag reflex, reported by 70.42% of participants, emerged as a substantial barrier. It was associated with lower use of tongue brushes (OR = 0.61) and a reduction in overall cleaning frequency. Factors associated with heightened gag reflex included female gender and recent consumption of sweetened or alcoholic beverages, which may increase oral mucosal sensitivity [23]. This barrier can discourage deep cleaning or lead to abandonment of the practice. These findings are consistent with previous research, which has shown heightened oral sensitivity in females (Lipsky et al., 2021), supporting the promotion of gender-specific oral health education [11].

Overall, a multifactorial interplay of demographic factors, perceived benefits, physiological barriers, and familiarity with cleaning tools shapes tongue-cleaning behaviour. Educational interventions should address these domains by integrating tongue hygiene into oral health training curricula, emphasizing proper technique, reducing gag reflex sensitivity, and promoting the use of evidence-based tools [24]. Such initiatives can improve adherence and strengthen the role of medical students as advocates for comprehensive oral hygiene.

5. LIMITATION

This study presents several limitations. Firstly, the cross-sectional design prevents the establishment of causal relationships between behavioural factors and tongue-cleaning practices. Secondly, data were obtained through self-reporting, which may introduce recall bias or social desirability bias, particularly among medical students who are expected to demonstrate ideal health behaviours. Thirdly, the study was conducted at a single medical university, which limits the generalizability of the findings to other institutions or populations. Students from a single university, particularly one with a strong medical curriculum, may not represent the broader population of university students or young adults in Vietnam or other countries. Differences in educational background, cultural norms, socioeconomic status, and access to oral health education may influence tongue-cleaning behaviours in various settings. Lastly, although health behaviour models were applied, some relevant constructs, such as peer influence and wider social norms, were not fully captured and should be addressed in future research.

CONCLUSION

The prevalence of tongue cleaning among medical students remains low, with suboptimal techniques and inappropriate tool usage. Factors, such as gender, overall oral hygiene practices, gag reflex, perceived oral cleanliness, and information-seeking behaviour, were significantly associated with tongue-cleaning habits. These findings underscore the importance of integrating tongue hygiene education into medical training, informed by health behaviour models, to enhance effectiveness and promote long-term practice.

REFERENCES