Which Method of Disinfecting Toothbrushes Kills the Most Bacteria?

- Abigail Fuscaldo

Question:

What is the best method of cleaning toothbrushes?

Hypothesis:

How many times have you brushed your teeth and tried to clean your toothbrush, not knowing what to use? Well I have tested 5 different methods on cleaning toothbrushes. The 5 methods were: boiling water, salt water, hydrogen peroxide, a UV toothbrush cleanser, and Anti-Bacterial Soap. My hypothesis is that cleaning a toothbrush would be easy because all disinfectants are similar.My prediction was that all of the solutions would do equally fine. I chose this because they all either clean or heal. I chose this because last year I did “What Drink Damages Teeth the Most?”. I felt I was finishing it by also telling how to clean and properly brush your teeth.

Procedure:

Since I was going to attempt to grow bacteria, I made a simple incubator out of a cardboard box and two desk lamps.I was able to cover the box and reach a temperature of 99 degrees. The next step was to collect bacteria. I brushed my teeth with ten toothbrushes and allowed them to sit in the bathroom in an uncovered container for four days. Each agar plate had a sterile swab. Each toothbrush was also numbered. While wearing gloves,the sterile swab was placed and turned on a toothbrush. The swab then was rubbed across the correspondingly numbered agar plate in a zigzag motion, trying not to touch a spot twice. Plates one thru ten were placed in the incubator box. These were the 10 control plates.

Five methods were used to disinfect bacteria on ten toothbrushes. Toothbrushes 1 and 2 were soaked in a solution of salt water for 2 minutes. Wearing gloves, I placed and turned a sterile swab on each toothbrush. Each agar plate that corresponded to the numbered toothbrush was swabbed in the same matter as the controls, and placed in the same incubator.the toothbrushes 3 and 4 were placed in the boiling water for two minutes. The toothbrushes were swabbed and transferred to labeled agar plates in the same manner, then placed in the incubator.Toothbrushes 5 and 6 were placed in a solution of 3 percent hydrogen peroxide for two minutes. In the same manner, the brushed were also swabbed and transferred to agar plates and the incubator. Toothbrushes 7 and 8 were also placed in a solution of antibacterial soap and water. Like before, the toothbrush was put in the solution for two minutes, swabbed and rubbed on an agar plate in a zigzag motion.Toothbrushes 9 and 10 were finally, placed in a UV toothbrush sanitizer for two minutes. They were then taken out, swabbed, and rubbed on two other agar plates.

Conclusion:

The data collected was measured by counting the number of bacterial colonies grown on each plate, recorded in 12 hour intervals. The five methods of disinfection varied from no growth to growth that resembled control agar plates uninfected. The hot water showed no bacterial growth thru 84 hours, while the antibacterial soap showed very little growth. The UV sanitizer showed a moderate amount of growth. The 3 percent hydrogen peroxide and salt water solution showed the least amount of disinfection.

There was a difference in the amount of bacteria that grew from toothbrushes after they were cleaned. Hot water and antibacterial soap were the most effective.The UV sanitizer did not do as well as it was advertised. The kit promised to kill 99.99 percent of germs, but this was actually only moderately better than salt water. While hydrogen peroxide is often used to disinfect it did not seem to be effective in killing the germs on a toothbrush.The project could still be improved by increasing the sample sizes. Since only one person was used for source of bacteria the experiment may not have not have had all types of bacteria that appear on toothbrushes. Another topic upon improving is, I could have done more agar plates for each solution to decrease experimental error in culturing bacteria. Because all of my control plates showed some growth and some solution plates had little or no growth it seems the experiment was somewhat successful in starting to see how to clean a toothbrush.