User perception of fluoride mouthwashes for daily use: A randomized clinical trial

Abstract

Aim

To assess user perceptions of different commercially available fluoride mouthwashes (FL‐MWs).

Methods

A single‐blind, randomized clinical trial was conducted. Participants were randomly assigned to a sequence of six different FL‐MWs, one of which contained alcohol. For each visit, participants rinsed with one specific mouthwash (15 mL) for 30 s. After rinsing, participants completed a questionnaire with a visual analogue scale. Questions focused on overall taste, mild/pungent feeling, taste duration, foaming effect, burning sensation, sensitivity, numbness, dryness, rinsing time, smell, and colour of the mouthwashes. Descriptive analyses and statistical tests regarding differences among and between the mouthwashes were performed.

Results

Overall, 53 participants completed the study protocol, including nine who did, however, not rinse with the alcohol‐containing mouthwash due to religious reasons. Among the mouthwashes, significant differences were found for foaming effect, sensitivity, rinsing time, smell, and colour (p < 0.05). Pairwise comparison for smell did not reveal a difference, and foaming was within the acceptance range (low to medium foaming). Coloured mouthwashes were more appreciated than transparent solutions (p = 0.00). The mouthwash containing essential oils and alcohol produced significantly more sensitivity (p = 0.00) and, in general, participants experienced the rinsing time significantly longer (p < 0.05) compared to the non‐alcohol‐containing mouthwashes.

Conclusion

There is heterogeneity in user perceptions and preferences for FL‐MWs, with a significant difference in foaming effect, sensitivity, rinsing time, smell, and colour. Coloured mouthwashes are preferred. The mouthwash containing essential oils and alcohol was less acceptable in relation to sensitivity and rinsing time.

1. INTRODUCTION

Dental caries is a worldwide health problem affecting a majority of adults and children. ¹ , ² In 2019, caries was defined as the most common oral disease, and it was estimated that approximately 2 billion people suffer from caries of the permanent dentition. ³ Caries develops over time through a complex interaction between acid‐producing bacteria and fermentable carbohydrates. The risks for developing caries include physical, biological, environmental, behavioural, and lifestyle factors. ¹ , ² Important aspects related to the development of caries are high numbers of cariogenic bacteria, inadequate salivary flow, inadequate fluoride exposure, and poor oral hygiene. ¹ , ² Untreated caries can cause cavities, which ultimately can cause severe pain. ² Depending on the extent of the cariogenic destruction, various treatments can be applied to stop the progress of the disease and restore teeth to re‐establish proper function. ¹ , ⁴ This treatment of dental caries is costly in terms of time and money and depletes healthcare resources. ¹ Preventing caries is a priority for dental healthcare professionals (DCPs) and is considered to be more cost‐effective than the treatment of carious lesions. ¹ The general approach for caries prevention involves the practice of brushing teeth twice daily for a minimum duration of 2 min, utilizing a fluoride toothpaste. Additionally, it encompasses the reduction of the frequency of dietary intake and beverage consumption occasions throughout the day. ⁵ , ⁶ Along with this, an interdental cleaning device can complement toothbrushing, for the prevention and control of periodontal disease and dental caries. ⁷ In addition, DCPs may recommend the use of a fluoride mouthwash (FL‐MW) to prevent caries. ¹ , ⁸ Fluoride has an anti‐cariogenic effect and strengthens tooth enamel. ⁹ Mouthwashes with low concentrations of fluoride (200–300 ppm) are available for daily home use, ¹ and regular use of FL‐MW by children and adolescents is associated with a decrease in the frequency of caries. ¹ A variety of mouthwashes is available over the counter (OTC) in different colours, tastes, etc., and for different marketed purposes. ¹⁰ However, the variety and range of mouthwashes available can be confusing for patients. ⁸ User's perceptions of mouthwashes are driven mostly by taste, smell, and colour. ¹¹ , ¹² , ¹³ Perception is a complex process involving not only the senses but also cognitive strategies, such as expectation, memories, and environmental stimuli. ¹¹ , ¹³ , ¹⁴ , ¹⁵ , ¹⁶ Until now, studies focused mainly on the effectiveness and different ingredients of mouthwashes. Important aspects of the patient experience and acceptance have been neglected in research. Beyond the efficacy, user perceptions such as taste and rinsing experience may play an important role in patient compliance. ¹⁷ , ¹⁸ Therefore, patients' compliance is an important factor to achieve a successful daily use of mouthwash. ¹⁹ However, there are currently no evaluations of patient perceptions in the public nor in the scientific literature on FL‐MW. Consequently, an evidence‐based recommendation on user preferences of an FL‐MW is difficult, if not impossible, to provide. In order to enhance patient compliance and to offer personalized recommendations, it is important to gain a deeper understanding of patients' perceptions regarding use of an FL‐MW. Therefore, the objective of this study is to evaluate how first‐year students in the dental hygiene education program perceive and prefer various commercially available FL‐MWs.

2. METHODS

2.1. Focused question

What are user perceptions and preferences of rinsing with different FL‐MWs among first‐year students in the dental hygiene education program?

2.2. Ethics

This study received ethical approval from the Research Ethics Committee of the HAN University of Applied Sciences (Ref.no:ECO391.09/22; see Appendix S1). This study was conducted according to the manual “Integer Research HAN University of Applied Sciences” based on Netherlands code of Conduct for Research Integrity, ²⁰ the Medical Research Involving Human Subjects Act (WMO), ²¹ the Medical Ethics Review Committee (METC), the General Data Protection Regulation (AVG), ²² and the Medical Treatment Agreement Act (WGBO), ²³ thereby meeting the criteria of the Declaration of Helsinki on Ethical Principles for Medical Research Involving Human Subjects. ²¹ For this paper, the general reporting guidelines of the Consolidated Standards of Reporting Trials (CONSORT) statement and the Template for Intervention Description and Replication (TIDieR) checklist, an evidence‐based set of recommendations for reporting randomized trials was used. ²⁴ , ²⁵

2.3. Design

This study was a single‐blind, randomized cross‐over clinical trial. In total, six different mouthwashes were randomly assigned for a single‐use rinsing episode per visit. Following the rinsing procedure, participants filled out a questionnaire using a visual analogue scale (VAS) to gather information about their perceptions and preferences. ²⁶

2.4. Sample

A convenience sample was used among first‐year dental hygiene students, a bachelor's program at the HAN University of Applied Sciences in the Netherlands. The study was performed from September 2022 until January 2023, during the first months of the academic year. The full cohort starting September 2022 consisted of 72 students, and the sample size was calculated using G*power 3.1 for a normally distributed sample. ²⁷ The ‘a priori’ power analysis and sample size calculation, considering α = 0.05, power (1‐β, error probability) = 0.80, and an effect size of 0.25, indicated that a minimum sample size of 19 participants would be required.

2.5. Participants

The first author (LSJT) sent a recruitment email to all students in the cohort, which included an information letter, an informed consent form, and the study's agenda planning, as part of the invitation to participate as potential participants. Data were collected face‐to‐face at the clinic for the dental hygiene education program. On the first assessment day, the participants were provided with the opportunity to review the information letter again and ask any questions they had before proceeding to sign the informed consent form. This ensured that they had a clear understanding of the study's details and could provide informed consent willingly. Then, a subject ID was assigned to each participant enrolled, and participants were instructed to use this specific subject ID throughout the study. The code/identifier to the IDs was kept concealed, and exclusive access to a decryption key for participant identification was granted to LSJT. The six different mouthwashes could be assigned to 720 unique order sequences where each mouthwash was used once. A set of 100 randomized sequences for a single use of the six different mouthwashes was established by LSTJ from https://www.randomizer.org/. Each subject ID was assigned a unique randomized sequence.

2.6. Eligibility criteria

Participants completed a medical and dental questionnaire and were assessed for inclusion and exclusion criteria (Appendix S2). To be included, a subject had to meet the following criteria: first‐year students of the dental hygiene education program at HAN, ≥18 years of age, and classified as systemically healthy as assessed by the medical questionnaire (ASA criteria, ²⁸ Appendix S2). Individuals were excluded from participation in this study based on the following criteria: taste and/or smell problems in the past 3 months, pregnancy, adverse medical history or long‐term medication (except birth‐control medication), allergies to any of the mouthwash components, having fixed and/or removable orthodontic appliances (retainers as lingual bars and night guards were allowed), and removable (partial) dentures. Pregnancy and orthodontic appliances were determined through self‐reporting. During the last rinsing episode, information on age and gender was obtained in a predefined administrative form.

2.7. Study products and procedures

The six evaluated mouthwashes were coded as A–F, and detailed product information can be found in Table 1. Commercially available mouthwashes were selected from international brands containing at least 226 ppm fluoride. ²⁹ Only mouthwash C contained the combination of essential oils and alcohol. Participants rinsed with a 15 mL mouthwash for 30 s. Rinsing instructions were based on general instructions by the Dutch Society of Periodontology ³⁰ (see Appendix S3). Participants were instructed not to drink coffee, chew gum, and/or smoke in the 30 min before the rinsing episodes. Supervised by the researchers, the participants rinsed with the FL‐MW at each weekly visit. Based on the subject's ID, the researchers provided a mouthwash that corresponded to the measurement day and the unique individual sequence. The products remained blinded to the participant throughout the intervention. All researchers involved in the study, including dental hygienists (BvS_DES_MS_TK) and last‐year dental hygiene students (IJ_ML), strictly followed the study protocol. They utilized a standardized case record form specifically tailored for this research. Before the commencement of the study and on each measurement day, the researchers underwent training to ensure proper adherence to the prescribed procedures and the correct utilization of the designated forms. Participants who a priori declared not to rinse with alcohol‐containing mouthwashes were discarded from the episode when mouthwash C via the randomization was assigned.

TABLE 1.

Investigational products.

Code	Product	Company	Fluoride type and %	Dutch website of used product
A	Elmex Sensitive	Colgate‐Palmolive New York – USA	Olaflur and sodium fluoride (250 ppm)	https://www.elmex.nl/products/product‐range/sensitive/elmex‐sensitive‐mouthwash
B	Fluor aid 0.05	Dentaid Barcelona – Spain	Sodium fluoride (226 ppm)	https://dentaid.nl/nl/producten/fluoraid/fluoraid‐mondspoeling
C	Listerine Total Care	Johnson & Johnson New Jersey – USA	Sodium fluoride (300 ppm)	https://www.listerine.nl/nos‐products/6‐1‐werking/listerine‐total‐care
D	Meridol	Colgate‐Palmolive New York – USA	Olaflur and stannous fluoride (250 ppm)	https://www.meridol.nl/products/meridol/mondspoeling
E	O7 Active	Sunstar Etoy – Switzerland	Sodium fluoride (226 ppm)	https://www.o7active.com/project/o7‐active‐mondspoelmiddel/
F	Vitis Gingival	Dentaid Barcelona – Spain	Sodium fluoride (226 ppm)	https://dentaid.nl/nl/producten/vitis/vitis‐gezond‐tandvlees/vitis‐gezond‐tandvlees‐mondspoeling

2.8. Study data collection

Nine questions were extracted from previously published studies using a Dutch questionnaire on aspects of user perceptions and preferences of mouthwashes (for an overview, see Appendix S4). ³¹ , ³² , ³³ , ³⁴ , ³⁵ An 11‐item questionnaire (see Appendix S5a,b) was developed using face validity based on input from an expert panel of three dental hygienists, an implant dentist, a periodontist, and two dental hygiene students; two new questions were added addressing smell and the visual aspect. ³⁶ The main parameters of the study were taste aspects: overall taste, mild/pungent feeling, and taste duration; aspects of the rinsing experience: foaming effect, burning sensation, sensitivity of the mucosa and/or teeth, numbness, dryness, and rinsing time; smell; and colour. Immediately after rinsing, the participants completed the 11‐item VAS questionnaire, placing a vertical mark on a 100‐mm‐long line. ²⁶ The researchers measured the distance in mm along the line from the left extreme (being the lower extent of the item scored) to the mark made by the participant, ²⁶ and this distance was considered to be the score assigned by the participant for the specific mouthwash and VAS question.

2.9. Data analysis

The scores from the measurements were entered into a Microsoft Excel ³⁷ file, and these files were merged and converted into one SPSS file using IBM SPSS Statistics for Windows (version_27.0). ³⁸ This was supplemented with information on the participants' age, gender, and smoking habits. Descriptive statistics were performed concerning gender, age, and number of participants. Mean scores, standard deviation (SD), and 95% confidence interval (CI) were listed per mouthwash per question item. It was decided a priori that those participants who do not want to rinse with the alcohol‐contained mouthwash are not taken into account by evaluating mouthwash C. This implies that finally two datasets will be obtained. A full dataset with less participants in group C than in the other mouthwash groups due to the decline used for the intention to treat analysis. A smaller dataset where all participants used all mouthwashes without those who a priori declared not to rinse with an alcohol‐contained mouthwash for the per‐protocol analysis. For all statistical tests, a p‐value <0.05 was considered significant. The data obtained were first tested for normal distribution using the Kolmogorov–Smirnov test (p‐values were adjusted for the 66 questions). ³⁹ The difference in mean scores of the 11 items between the FL‐MWs was calculated with the parametric test repeated measures ANOVA. ⁴⁰ Repeated measures analyses are a powerful way to analyse for within‐subject differences between the various mouthwashes tested. As equal participant numbers for all mouthwashes are essential for applying repeated measures tests to each mouthwash variant, a per‐protocol analysis was employed. ⁴¹ , ⁴² To assess the potential impact of the measurement moment in the rinsing sequence on the outcome, a one‐way ANOVA between subjects was conducted. ⁴³ This analysis aimed to determine whether a difference existed between measurement moments per mouthwash, taking into account the possible influence of repeated rinses over time. When a significant difference was found in the ANOVA tests, a post‐hoc pairwise comparison with Bonferroni correction was conducted to determine the origin of the difference. ⁴⁴ Appendix S5c presents the interpretation of the questionnaire scores and the outcome extremes. Based on this interpretation, ranked scores for each question and mouthwash were made, and the overall ranking of the six mouthwashes was calculated.

3. RESULTS

3.1. Sample and characteristics

The study sample consists of 64 participants. After the eligibility criteria were met, 58 participants remained, as six subjects were excluded: five for being under 18 years of age and one because of fixed orthodontic appliances. Figure 1 presents a flowchart with the selection and study process. In total, five participants initiated the study but did not attend all six rinsing moments unrelated to the use of study products due to scheduling conflicts. These participants were considered lost to follow‐up. Consequently, 53 participants fulfilled all of the study protocol visits, including nine participants who did not rinse with the assigned alcohol‐containing mouthwash for religious reasons. The enrolled participants consisted of four men and 49 women. The mean (SD) age was 20, ⁴ with a minimum age of 18 and a maximum age of 43. In total, one was a smoker, smoking 15 cigarettes a day.

FIGURE 1.

Flowchart depicting subject enrolment, allocation, and measurements.

3.2. Outcome

Table 2 presents the mean scores and SDs for all mouthwashes related to each questionnaire item. The majority of the data demonstrated a normal distribution. Therefore, parametric testing was performed. Of the 53 participants, nine were rinsed with only five mouthwashes (A, B, D, E, and F), as mouthwash C contained alcohol. A repeated measures ANOVA and post‐hoc testing can only be performed, when the same participants are represented in each mouthwash measurement. Therefore, per‐protocol statistical testing was performed with 53 participants for comparisons between mouthwashes A, B, D, E, and F, and for the comparison between all the mouthwashes, including mouthwash C, 44 participants were taken into account, as shown in Table 2.

TABLE 2.

Outcome per question and mouthwash, presented as mean, standard deviation (SD), and 95% confidence interval (CI).

Mouthwash questions	A	B	C	D	E	F	Statistics among groups* N = 53**	Statistics among groups* N = 44***
	N = 53	N = 53	N = 44	N = 53	N = 53	N = 53
1. Colour	5.14 (2.19)◊,○,□ [4.54; 5.75]	5.35 (2.14)∞,#,҂ [4.77; 5.94]	7.32 (2.15)◊,∞,× [6.66; 7.97]	7.67(1.57)○,#,◄ [7.23; 8.10]	4.92 (2.50)×,◄,▼ [4.23; 5.61]	7.67 (1.81)□,҂,▼ [7.17; 8.17]	0.007*	0.001*
2. Taste overall	4.97 (2.55) [4.27; 5.68]	6.30 (2.03) [5.74; 6.86]	3.59 (2.25) [2.91; 4.28]	6.22 (2.26) [5.59; 6.84]	5.24 (2.28) [4.61; 5.86]	6.64 (1.92) [6.11; 7.17]	0.143	0.123
3. Foaming effect	3.94 (2.21) [3.33; 4.55]	3.49 (2.36)◊,○ [2.85; 4.14]	3.73 (2.11) [3.09; 4.37]	4.95 (2.36)◊,□ [4.30; 5.60]	4.78 (2.35)○,∞ [4.13; 5.43]	3.40 (2.21)□,∞ [2.79; 4.01]	0.048*	0.016*
4. Burning sensation	3.73 (2.34) [3.08; 4.37]	1.43 (1.59) [0.99; 1.87]	8.02 (1.84) [7.46; 8.58]	3.25 (2.50) [2.55; 3.93]	4.48 (2.59) [3.77; 5.20]	3.24 (2.36) [2.59; 3.89]	0.392	0.419
5. Mild or pungent feeling	5.41 (2.22) [4.80; 6.02]	2.53 (1.84) [2,02; 3.04]	8.21 (1.52) [7.75; 8.67]	4.77 (1.95) [4.24; 5.31]	5.42 (2.23) [4.81; 6.04]	3.99 (2.04) [3.43; 4.55]	0.510	0.179
6. Sensitivity	1.92 (1.97)◊,○ [1.38; 2.47]	1.17 (1.52)◊,□,∞ [0.75; 1.59]	5.56 (2.87)○,□,#,҂,× [4.69; 6.43]	2.04 (2.23)# [1.42; 2.65]	2.87 (2.61)∞,҂ [2.15; 3.59]	1.72 (1.82)× [1.22; 2.22]	0.039*	0.008*
7. Numbness	2.28 (2.08) [1.70; 2.85]	1.11 (1.36) [0.74; 1.49]	4.89 (2.51) [4.13; 5.66]	1.93 (2.02) [1.37; 2.49]	2.40 (2.22) [1.79; 3.01]	1.93 (1.92) [1.40; 2.46]	0.620	0.400
8. Dryness	1.61 (1.77) [1.12; 2.10]	1.48 (1.80) [0.98; 1.97]	2.55 (2.58) [1.77; 3.34]	3.45 (2.93) [2.64; 4.26]	1.77 (2.03) [1.21; 2.33]	2.17 (2.30) [1.54; 2.81]	0.203	0.482
9. Taste duration	6.79 (1.87) [6.28; 7.31]	5.13 (2.18) [4.53; 5.74]	6.99 (1.62) [6.50; 7.49]	6.12 (2.00) [5.57; 6.67]	6.22 (2.12) [5.64; 6.81]	4.95 (2.18) [4.35; 5.55]	0.644	0.138
10. Rinsing time	4.29 (1.72)◊ [3.82; 4.77]	4.06 (1.87)○ [3.54; 4.57]	5.51 (2.11)◊,○,□ [4.87; 6.15]	4.24 (1.90) [3.71; 4.76]	4.69 (1.92) [4.16; 5.22]	3.81 (1.88)□ [3.30; 4.33]	0.668	0.010*
11. Smell	5.68 (1.94) [5.15; 6.22]	5.92 (1.49) [5.51; 6.33]	5.74 (2.13) [5.09; 6.39]	6.01 (1.55) [5.58; 6.44]	5.62 (1.83) [5.12; 6.13]	6.32 (1.77) [5.83; 6.81]	0.007*	0.000*

Note: Mean and standard deviation (SD) per mouthwash per question. 1. How did you like the colour of the mouthwash? Range: unattractive–appealing. 2. How did you like the taste of the mouthwash? Range: very disgusting–very delicious. 3. This mouthwash foamed… Range: not at all–very much. 4. To what extent did you experience a burning sensation in the mouth as a result of the mouthwash? Range: not at all–very much. 5. How mild or pungent was the taste of the mouthwash? Range: very mild–very pungent mouth feel. 6. To what extent did you experience sensitivity of the mucosa membranes and/or teeth as a result of the mouthwash? Range: not at all–very much. 7. To what extent did you experience a numbing sensation as a result of, the mouthwash? Range: not at all–very much. 8. To what extent did you experience a dry mouth as a result of the mouthwash? Range: not at all–very much. 9. How long did the taste of the mouthwash linger? Range: very short–very long. 10. What was your experience regarding the rinsing time? Range: very short–very long. 11. How do you find the smell of the mouthwash? Range: very disgusting–very delicious. ◊, ○, □, ∞, #, ҂, ×, ◄, ▼ = Matching symbols per question represent statistical significance between group.

^*Statistically significant difference among groups (ANOVA) p < 0.05.

^**Comparison without Listerine Total Care (C), only Elmex Sensitive (A), Fluor aid 0.05 (B), Meridol (D), O7 Active (E), and Vitis Gingival (F).

^***Only for N = 44 with a full data set included Listerine Total Care (C).

No significant differences were found for overall taste, burning sensation, mild/pungent feeling, numbness, dryness, and taste duration (p > 0.05). However, the perception of foaming effect, sensitivity, smell, and colour significantly differed among the mouthwashes (p < 0.05; see Table 2). Rinsing time was significant (p = 0.010) when evaluated with the dataset including rinse C, without there was no difference (p = 0.668). In addition, post‐hoc testing showed only significant difference when C was compared to other mouthwashes. The analysis showed that there were no significant differences between subjects in terms of measurement moments and the rinsing sequence per mouthwash. This suggests that there was no influence of repeated rinsing episodes over time to be observed in the study.

3.3. Post‐hoc pairwise comparison

The pairwise comparisons for smell did not reveal a difference (p > 0.05; see Appendix S6.1). Concerning colour, the pairwise comparisons revealed significant differences (p = 0.00) in favour of the coloured mouthwashes (C‐purple, D‐blue, F‐pink), when compared to the transparent mouthwashes (A, B, E; see Appendix S6.2). On the other hand, among the three coloured or three transparent mouthwashes, no significant differences were found. In general, with 5 being considered neutral, foaming was within the acceptance range (3.40–4.95; see Table 2). According to the measurements, mouthwashes B and F had the least foaming effect and D and E had the most. Between these low‐ and most‐foaming mouthwashes in a pairwise comparison, a significant difference was found (see Appendix S6.3). Mouthwash C was associated with significantly more sensitivity (p = 0.00) compared to the five other mouthwashes (see Appendix S6.4). Mouthwash B had the best score regarding sensitivity; in addition to mouthwash C, mouthwash B was significantly more acceptable than A (p = 0.03) and E (p = 0.00). Mouthwash C provided the longest experience of rinsing time (Table 2). When C was compared to the three mouthwashes where the experienced rinsing time was the shortest (A, B, F), there was a significant difference (p < 0.03; see Appendix S6.5).

3.4. Overall ranking scores of the mouthwashes

Using the interpretation of the questionnaire scores (Appendix S5c), a ranking per mouthwash per question was made (see Appendix S7 for details). Based on the sum, an overall score per mouthwash was calculated, and the mouthwashes were ranked as follows: 1:B, 2:F, 3:D, 4:A, 5:F, 6:C. Consequently, mouthwash B can be considered the best appreciated.

4. DISCUSSION

4.1. Summary of findings

This study assessed user preferences and experiences when rising with different FL‐MWs. A single‐blind, randomized cross‐over clinical trial was conducted among first‐year students of the dental hygiene bachelor's program, at the beginning of the academic year. Six FL‐MWs were used, and questions focused on overall taste, mild/pungent feeling, taste duration, foaming effect, burning sensation, sensitivity, numbness, dryness, rinsing time, smell, and colour. No significant differences were found for overall taste, burning sensation, mild/pungent feeling, numbness, dryness, or taste duration. However, the perceptions of foaming effect, sensitivity, rinsing time, smell, and colour differed significantly among the mouthwashes. Coloured mouthwashes were better appreciated than transparent solutions. The mouthwash that contained essential oils and alcohol produced significantly more sensitivity and, in general, a longer rinsing time compared to the other mouthwashes.

4.2. Compliance

Compliance is a commonly used term in (oral) healthcare that describes patients' willingness to follow advice. ¹⁹ Patients' compliance is also important to achieve a successful daily use of mouthwash ¹⁹ ; if such compliance is lacking, a daily rinsing regimen will be suboptimal. ¹⁹ Patients sometimes struggle with following oral self‐care instructions. DCPs need to effectively convey the significance of adhering to advice and being compliant with recommendations. ¹⁸ Also in evidence‐based dentistry (EBD) (oral)healthcare decision‐making requires not only the integration of the systematic assessment of clinically relevant scientific evidence combined with clinical expertise but also the patient's needs and preferences. ⁴⁵ , ⁴⁶ Patient values play a significant role. It is important to consider and incorporate the distinct preferences, concerns, and expectations of individuals into a treatment plan. ⁴⁵ , ⁴⁷ , ⁴⁸ This enhances the success rate for both the patient and the DCP. To motivate patients to adhere to oral hygiene self‐care advice and instructions, including the daily use of an FL‐MW, DCPs need to understand the factors that lead to compliance and non‐compliance. ¹⁹ The present study contributes to a better understanding of the factors leading to compliance with daily use of an FL‐MW.

4.3. Perception

The basic aspects that govern humans' perceptions of food are gustatory (taste), olfactory (smell), and somatosensory system (touch/texture). ¹⁴ The perception of food is driven mostly by taste and smell as well as a variety of other factors such as colour, expectation, and cognitive strategy. ¹¹ , ¹² , ¹³ , ¹⁵ , ¹⁶ Thus, it is a complex process involving not only the senses but also the brain and mind based on already‐known information and lived experiences. ¹¹ , ¹³ , ¹⁴ , ¹⁵ From a practical perspective, a negative perception can negatively influence perception scores. Therefore, in the present study, only one rinsing episode per visit was executed. Moreover, the perception of flavour can be present for an extended period of time. This confirms the decision to apply only one mouthwash per assessment day. A recent study outlines the possible link between taste perception and preferences in eating habits and oral hygiene patterns, ⁴⁹ Where respondents who most regularly used oral hygiene products experienced bitter and sweet more intensely and appreciated a bitter taste more. ⁴⁹ According to this study, variation in taste may contribute to the possible liking or disliking of mouthwash and suggests the importance of further research into taste‐related barriers or drivers of good oral hygiene patterns. ⁴⁹ The present study contribute to information with regard to mouthwashes considers possible drivers and barriers in foaming effect, sensitivity, rinsing time, smell, and colour. The perception of pain or sensitivity during rinsing with a mouthwash can be discouraging and may have a negative impact on patient compliance. ¹⁷ Moreover, direct factors such as unpleasant taste or indirect factors such as tooth staining may affect compliance. ¹⁸ For DCPs, it is important to reflect on the process of individual perception—for instance, asking which aspects of perception contribute to compliance—to provide tailored and individualized advice. Therefore, taking into account perception also contributes to the concept of shared decision‐making.

4.4. Active ingredients

The focus of this study is on FL‐MWs, as fluoride is an important active ingredient for preventing caries. ¹ It is an inexpensive and easily accessible product, available OTC for daily use. However, an FL‐MW may contain multiple other ingredients that could affect the user's perception. Cetylpyridinium chloride (CPC) is often present in mouthwashes, and research has found evidence that CPC provides a small but significant additional benefit in reducing plaque and gingival inflammation. ⁵⁰ In the present study, mouthwash F contains CPC. Previous research found that patients rate CPC positively regarding sensitivity, a burning sensation, and dry mouth, ³⁴ which is consistent with it the findings of the present study. However, a systematic review shows that a small number of studies, maximal being 7 out of 20, do report a burning sensation for CPC mouthwashes. ⁵¹ The participants in the current study reported the most sensitivity when rinsing with mouthwash C, the only one that contained essential oils and alcohol. Participants also rated the rinsing time of mouthwash C as the longest and significantly longer than three other mouthwashes (A, B, F). This is consistent with previous research in which burning or irritation in the mouth was reported after using an alcohol‐containing mouthwash. ¹⁹ Mouthwash C also contains essential oil of eucalyptol, which is associated with pungent, cooling, and spicy tastes and may have contributed to sensitivity. ⁵² It is even recommended to dilute a mouthwash with the combination of essential oils and alcohol with water for the first few days of use, which often leads to acceptance. ⁵³ The combination of essential oils and alcohol is in general rather unique for the brand used as mouthwash C. The manufacturer of mouthwash C recommends on its website that users gradually become accustomed to the strength of the mouthwash by rinsing for 10 s on days 1–2, for 20 s on days 3–4, and for 30 s thereafter. Such a stepwise approach to acceptance was not addressed in the current study, but, hypothetically, it could have led to more positive ratings by the participants. Alcohol‐based mouthwashes are often associated with oral malignancy, ⁵⁴ but a systematic literature review revealed no association between the use of mouthwashes with alcohol and the risk of oral cancer. ⁵⁴ But the alcohol base of mouthrinse C is a contraindication for recovering alcoholics or those who observe religious restrictions. ⁵⁵ , ⁵⁶ This may also be relevant for pregnant women, although there is no medical contraindication. Nevertheless, pregnant women often find their perceptions of taste to change, which was the reason for not including this group as study participants. ⁵⁷

4.5. Strengths and limitations

The pre‐calculated sample size of 19 participants was achieved with 53 participants completing the full study protocol. Another strength of this study was the fact that there were no significant differences in terms of measurement moments and the rising sequence. This suggests that the chosen design, including randomization approach, was successful.

Considering that a convenience sample was used for this study, the sample may not be representative of the general population. In potential, assumptions arriving from this study can be biased and inconsistent when generalized for a universal population. ⁵⁸ , ⁵⁹ Particularly in dental hygiene, students may have had prior knowledge of mouthwashes from previous education or work experience as a dental nurse. Nevertheless, from the present sample of students, fewer than 3% are certificated dental nurses, and the majority have only a general high school education. To minimize a potential bias that could have been introduced by the education program of the participating students, the current study was performed blinded in the first weeks of the academic year. ⁵⁹ Another potential limitation for generalizability is the age of the sample: The mean age was 21, which is representative of young adults. Fortunately, research indicates that age has little to no effect on taste perception of flavourings. ⁶⁰ However, impaired perception of smell is known to increase with age. ⁶¹ Not only do elderly people perceive odours as less intense but they also experience more difficulty identifying odours. ⁶¹ Consequently, odour perception may be overrepresented in this study. The present sample also consists mainly of female participants. According to previous research, there is evidence of genetic differences in the perception of taste, smell, and colour, but genetically determined individual differences are not clearly distinguishable between males and females. ⁶² As a result, the difference is too small to justify adjusting the study outcome for gender. ⁶² The present sample contains one smoker, smoking habits by itself results in a decreased taste sensitivity, irrespective of the subjects' age. ⁶³ Moreover, current smoking, but not former smoking, is associated with significantly increased smell dysfunction. ⁶⁴ The results are not adjusted for smoking although as part of the research protocol smoking 30 min before the rinsing episodes was avoided.

4.6. VAS scores

The VAS technique is widely used to assess clinical symptoms and has been shown to provide a valid and reliable solution to challenging measurement problems. ²⁶ , ³² No validated questionnaires for measuring the perceptions of mouthwashes exist, so the researchers chose to extract questions from studies with already‐existing VAS‐score questionnaires in the Dutch language to explore the perceptions and preferences of mouthwashes. ³¹ , ³² , ³³ , ³⁴ , ³⁵ Additionally, two questions, on smell and visual aspects, were added through face validity by seeking advice from a panel of experts ³⁶ with the intention to generate a comprehensive portrayal of perception. ¹² , ¹³ In retrospect, a question exploring the participants' general perceptions could have been added.

4.7. Implications for clinical practice and future research

This clinical trial reveals heterogeneity in user perception. DCPs commonly provide advice based on studies that report on the effectiveness of ingredients or products. The recommendation of this study is that DCPs should incorporate patients' perceptions into their advice because awareness of the differences in perception could increase daily oral homecare compliance. DCPs can contribute to this process by providing mouthwash samples so that their patient can select their preferred product based on their own experience. Future research can be performed on the perceptions of mouthwashes for specific problems such as gingivitis, periodontitis, dentine hypersensitivity, and dry‐mouth problems. The potential influence of colour and flavour on compliance highlights the need for further research in this area. These results could contribute to creating an overview of mouthwashes and perceptions according to the area of indication. Further development and validation of a questionnaire on the perception of mouthwashes would be an ideal complement for this purpose.

5. CONCLUSION

There is heterogeneity in user perception and preferences for FL‐MWs, with significant differences in foaming effect, sensitivity, rinsing time, smell, and colour. Coloured mouthwashes are preferred. The mouthwash containing essential oils and alcohol was less acceptable in relation to sensitivity and rinsing time.

6. CLINICAL RELEVANCE

6.1. Scientific Rationale

No evaluation of patient perceptions of fluoride mouthwash (FL‐MW) is available. Understanding patients' perceptions will be necessary to increase the compliance and contribute to more individualized recommendations.

6.2. Principal Findings

Heterogeneity in user perception and preferences for FL‐MWs, with significant differences in foaming effect, sensitivity, rinsing time, smell, and colour. Coloured mouthwashes are preferred. The mouthwash containing essential oils and alcohol was less acceptable in regard to sensitivity and rinsing time.

6.3. Practical Implications

Differences in preferences and experiences could play an important role in patient values, which contribute to compliance. Therefore, dental care professionals should tailor their advice not only to effectiveness but also to patients' perceptions.

AUTHOR CONTRIBUTIONS

LSJT: contribution to the conception, design, acquisition, analysis, and interpretation of data for the work, and drafting of the manuscript. BVS: contribution to the conception, design, and acquisition of the work, and critically revising it for important intellectual content. MFT: contribution to the analysis and interpretation of data for the work, and critically revising it for important intellectual content. GAW: contributed to interpretation and critically revising it for important intellectual content. DES: contribution to the conception, design, acquisition, analysis, and interpretation of data for the work, and critically revising it for important intellectual content. All authors gave their final approval of the version to be published and agreed to be accountable for all aspects of the work, ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.

FUNDING INFORMATION

This research received no specific grant from any funding agency in the public, commercial, or not‐for‐profit sectors. The work for this paper was funded by Dienst Uitvoering Onderwijs (DUO), which paid for the tuition fee and study leave by providing the first author (LJST) a teacher's scholarship to obtain a master's degree. Dentaid Netherlands (Fluor aid and Vitis Gingival) and Tandzorg Tilburg (O7) provided the mouthwash products free of charge. Other mouthwashes were bought at the first author's own expense. Utrecht University's Master Clinical Sciences for Health Professionals Program in Clinical Health Sciences is funded by the statistical support of Studiemeesters. The work was also funded by the regular academic appointments of Timmerman at Radboud University, Slot and van der Weijden at the Academic Centre for Dentistry Amsterdam (ACTA), and van Swaaij and Toonen at Hogeschool Arnhem Nijmegen (HAN), University of Applied Sciences.

CONFLICT OF INTEREST STATEMENT

The authors declare that they have no conflicts of interest. Slot, Timmerman and van der Weijden have previously received either external advisor fees, lecturer fees, or research grants from oral hygiene product manufacturers including Colgate, Dentaid, GABA, Lactona, Oral‐B, Procter & Gamble, Philips, Sara Lee, Sunstar, Tepe, Waterpik, and Unilever.

Supporting information

Appendix S1‐S7.

Toonen LSJ, van Swaaij BWM, Timmerman MF, Van der Weijden FG., Slot DE. User perception of fluoride mouthwashes for daily use: A randomized clinical trial. Int J Dent Hygiene. 2025;23:153‐163. doi: 10.1111/idh.12842

DATA AVAILABILITY STATEMENT

The data that support the findings of this study are available from the corresponding author upon reasonable request.