ABSTRACT
Objective:
This study compares the antibacterial efficacy of alcohol-based and alcohol-free mouthwashes against primary oral pathogens to guide public health oral hygiene choices.
Methodology:
Four mouth rinses—Listerine (Alcohol-Based), Colgate Plax (Alcohol-Free), Mouthwash Essentials (Alcohol-Based), and HerbalGuard (Alcohol-Free)—were tested against Streptococcus mutans, Porphyromonas gingivalis, and Fusobacterium nucleatum using the agar well diffusion method. The zones of inhibition were measured to assess antibacterial activity.
Results:
Alcohol-based mouthwashes demonstrated significantly larger zones of inhibition (18–20 mm) compared to alcohol-free variants (8–13 mm). One-way ANOVA revealed statistically significant differences (P < 0.05), with alcohol-based products showing superior antibacterial activity. Linear regression analysis revealed a direct correlation between alcohol content and antibacterial effect. The odds ratio indicated that alcohol-based mouthwashes were 25 times more likely to be effective against oral pathogens than alcohol-free mouthwashes.
Conclusion:
Alcohol-based mouthwashes are significantly more effective at inhibiting oral pathogens, suggesting their potential for use in public health oral hygiene programs.
KEYWORDS: Agar well diffusion, alcohol-based mouthwashes, alcohol-free mouthwashes, antibacterial efficacy, Fusobacterium nucleatum, odds ratio, oral pathogens, Porphyromonas gingivalis, public health, regression analysis, Streptococcus mutans
INTRODUCTION
Good oral hygiene is important to avoid oral diseases caused by both local and systemic factors. Of all oral hygiene practices, mouth rinses are good adjuncts to brushing and flossing as they decrease bacterial load, inhibit plaque formation, and decrease the risk of dental caries and periodontal disease.[1] These diseases are mostly caused by biofilm-forming bacteria like Streptococcus mutans, Porphyromonas gingivalis, and Fusobacterium nucleatum.[2] Though alcohol-containing mouth rinses, with agents such as chlorhexidine or cetylpyridinium chloride, have broad-spectrum antibacterial activity, alcohol-related side effect concerns have resulted in an increase in alcohol-free products.[3] Although commonly used, there is very little comparative research exploring the antibacterial effectiveness of these products in practice. This research seeks to fill that void by measuring and comparing the in vitro antibacterial efficacy of certain alcohol-based and alcohol-free mouthwashes against primary oral pathogens. Results will inform product choice for public health oral hygiene programs.
METHODOLOGY
This study was designed to evaluate the antibacterial activity of four commercially available mouth rinses against common oral pathogens. The following mouth rinses were chosen: Listerine (Alcohol-Based), Colgate Plax (Alcohol-Free), Mouthwash Essentials (Alcohol-Based), and HerbalGuard (Alcohol-Free). They were chosen because they are widely available in the market and because they have distinct formulations that recognized both the alcohol-based and alcohol-free varieties. To test the antibacterial activity of the rinses, an agar well diffusion method was used. The bacterial species Streptococcus mutans, Porphyromonas gingivalis, and Fusobacterium nucleatum were cultivated on Mueller-Hinton agar plates. Wells were created in the agar using a sterile cork borer, and 50 μL of each mouth rinse was pipetted into the wells. Plates were incubated at 37°C for 24 hours, allowing the bacteria to grow and the mouth rinse to diffuse into the agar in the immediate surrounding areas of the wells. After incubation, the zone of inhibition was measured in millimeters, which is the area around the well where the growth of bacteria was inhibited, indicative of the antibacterial action of the mouth wash. The procedure was done three times for the sake of reliability and accuracy of the results.
RESULTS
The four mouth rinses’ antibacterial activities against Streptococcus mutans, Porphyromonas gingivalis, and Fusobacterium nucleatum were assessed by agar well diffusion and are presented below in the table. The highest zones of inhibition for all the strains tested were produced by Mouth Rinse A (Alcohol-Based) with inhibition diameters of 18 mm for S. mutans, 15 mm for P. gingivalis, and 20 mm for F. nucleatum. Mouth Rinse C (Alcohol-Based) was also trending closely, with zones of 16 mm, 14 mm, and 19 mm, respectively. The alcohol-free mouth rinses, Mouth Rinse B and D, produced smaller zones of 8 mm to 13 mm in all strains [Table 1]. One-way ANOVA analysis of the data revealed a statistically significant difference (P < 0.05) between the antibacterial activity of the four mouth rinses. Particularly, the alcohol-based products exhibited far stronger antibacterial activity than the alcohol-free mouth rinses. Linear regression analysis was conducted to further investigate the strength of association between alcohol-containing mouth rinse versus alcohol-free mouth rinse and antibacterial effect. The regression equation demonstrated a direct relationship between alcohol content and zone of inhibition, which supported ANOVA results [Figure 1]. The odds ratio indicates that alcohol-based mouth rinses are 25 times more likely to be effective against oral pathogens compared to alcohol-free mouth rinses. These results emphasize the superior effectiveness of alcohol-containing mouth rinses in preventing prevalent oral pathogens and thus their potential application in public health preventive programs.
Table 1.
Comparative antibacterial efficacy of mouth rinses against oral pathogens
| Mouth Rinse | Streptococcus mutans | Porphyromonas gingivalis | Fusobacterium nucleatum | Mean Zone (mm) | Std Dev | Effectiveness Level |
|---|---|---|---|---|---|---|
| Listerine (Alcohol-Based) | 18 mm | 15 mm | 20 mm | 17.67 | 2.52 | High |
| Colgate Plax (Alcohol-Free) | 12 mm | 10 mm | 13 mm | 11.67 | 1.53 | Moderate |
| Mouthwash Essentials (Alcohol-Based) | 16 mm | 14 mm | 19 mm | 16.33 | 2.52 | High |
| HerbalGuard (Alcohol-Free) | 10 mm | 8 mm | 11 mm | 9.67 | 1.53 | Low |
*Mean Zone indicates average antibacterial activity; Std Dev reflects consistency across bacteria; Effectiveness Level is categorized as High (>15 mm), Moderate (12–15 mm), or Low (<12 mm)
Figure 1.
The scatter plot with a regression line showing the relationship between alcohol presence in mouth rinses (0 = alcohol-free, 1 = alcohol-based) and the mean zone of inhibition against oral pathogens. The trend suggests that alcohol-based mouth rinses tend to have greater antibacterial activity compared to alcohol-free ones
DISCUSSION
The findings of this research underscore the greater antibacterial activity of alcohol-containing mouthwashes over their alcohol-free counterparts. Alcohol-containing products, like Listerine and Mouthwash Essentials, produced significantly greater zones of inhibition in all oral pathogens tested, namely, Streptococcus mutans, Porphyromonas gingivalis, and Fusobacterium nucleatum. This observation concurs with existing literature, which indicates that the solvent action of alcohol increases the antimicrobial effect of mouthwashes by promoting the penetration of active ingredients into bacterial cell walls (Löe).[1]
The statistically significant difference in alcohol-based compared to alcohol-free mouthwashes is corroborated by linear regression analysis, revealing a positive relationship between alcohol level and antibacterial efficacy. The odds ratio of 25 also suggests alcohol-containing mouthwashes are considerably more effective in preventing the increase in oral microorganisms, providing justification for their use in clinical and public health practice (Gupta et al.).[3]
However, consideration of the potential side effects of alcoholic mouthwashes, such as irritation or dryness in some patients (Yano et al.),[4] should be taken. Less effective nonalcoholic substitutes may be better suited to patients who are sensitive, indicating patient profile-dependent oral hygiene recommendations.
CONCLUSION
This research concludes that antibacterial activity of alcohol-containing mouth rinses is higher than alcohol-free ones in the in vitro environment. Nevertheless, selection of the mouth rinse should take into account individual patient parameters like safety profile and individual choice. Clinical trials would be necessary to validate these findings and measure the actual success of mouth rinses in a real-life public health environment.
Ethical statement
We hereby transfer, assign, or otherwise convey all copyright ownership, including any and all rights incidental thereto, exclusively to the journal, in the event that such work is published by the journal.
Conflicts of interest
There are no conflicts of interest.
Funding Statement
Nil.
REFERENCES
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