Date: 2nd. May,2017

Despite the advances in medical technology, dental caries remains one of the most prevalent diseases around the world. Dental caries is caused due to damage to the outer tooth structure. The acids released as by-products of carbohydrate metabolism by the microbes, weaken the enamel and result in caries.

To improve oral hygiene, the use of mouthwashes has increased  is on the rise. In a study published in the Jundishapur Journal of Microbiology, Hexidine Mouthwash was found to be the most effective mouthwash against caries causing microbes.

This study was authored by Kamal Rai Aneja, Radhika Joshi, and Chetan Sharma from Department of Microbiology, Kurukshetra University. The aim of this study was to test the efficacy of ten of the most commonly available mouthwashes. The four pathogens these mouthwashes were tested against were:

• Streptococcus mutans (bacteria)
• Staphylococcus aureus (bacteria)
• Candida albicans (fungi)
• Saccharomyces cerevisiae (fungi)

Methodology

For the study, the following mouthwashes were obtained from drug stores:

To evaluate the antimicrobial potential of the mouthwashes, the following two techniques were employed:

1. Turbidity Measurement

In this technique, a one-percent nutrient broth was prepared containing 10% concentration of mouthwashes. Once the broth and mouthwashes were autoclaved, they were inoculated with 100µl of microbial inoculums, which were adjusted to 106cfu/ml. The inoculums were aerobically incubated at 37°C for 24 hours.

To check the microbial growth, the inoculated broths were suspended and optical density was measured at 490nm using a spectrophotometer. These experiments were performed in sets of three for each mouthwash and the mean for all four microbes was calculated.

2. Agar Well Diffusion Method

In this method, using sterile distilled water for dilution, different mouthwashes were tested at four concentrations:

• 1:4 (25%)
• 1:1 (50%)
• 3:4 (75%)
• Full strength (100%)

On the recommended media for each microbe, a pure isolate was subcultured for 24 hours at 37^oC. At least four colonies of microbes were touched with a sterile loop and transferred to a saline (0.85%) tube. Then, the density of each suspension was set to 10⁶ cfu/ml (standardized by 0.5McFarland standard), which was used as the inoculum.

100µl of mouthwash at all four concentrations was propelled directly into the wells for each microbe. After allowing the media agar plates to stand for 10 minutes for diffusion, they were incubated at 37^oC for 24, 48, and 72 hours.

The experiments were performed in sets of three and the mean values of inhibition zones’ diameter with standard deviation were calculated.

Nutrient broth and sterile distilled water were used as negative control in technique one and two, respectively.

Results

Hexidine Mouthwash by ICPA Health Products Ltd. delivered the best results, showing no turbidity at all. This indicates its effectiveness against caries causing microbes. Chlohex and Triguard also showed good results, however with slightly less effectiveness.

ConclusionZytee and Chlohex plus were found to be weaker still, while Hexnor, Chlorhexidine and Listerine only showed average results. Toss-K and Senquel-AD were completely ineffective against the microbes. Below are two graphs that show the action of mouthwashes on various microbes:

Mean diameter and standard deviation of zones of inhibition for ten mouthwashes after 24 hours at full strength against 4 caries causing microorganisms.

Microbial growth of S. mutans in nutrient broth with different mouthwash substitutes: summary of optical density data (three sets of experiments)

Conclusion

Out of the 10 mouthwashes used for the study, the 6 that proved to be the most effective against microbes contained chlorhexidine gluconate as their basic constituent. Hexidine Mouthwash (ICPA Health Products Ltd.) showed the excellent results against all four microbes.

To read the full study, click here.