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How dirty are your dental retainers? Featured science projectScience project video


Our hypothesis was that there will be greater amounts of bacteria on dental retainers if they are worn without being regularly brushed with toothpaste. The hypothesis has been proven to be true.

Regular  teeth brushing with toothpaste is important for maintaining our oral hygiene, such as helping to prevent tooth decay and reducing the amount of bacteria growth in our mouth cavities. Users of dental retainers will need to brush and clean their retainers regularly to remove the food particles that are stuck onto the surface.

Also consider

This science fair project can be repeated by varying the time allowed for the bacteria to grow  - eg. 8, 12, 24 hours. It would be interesting to see how long we should or should not wait before brushing our teeth.

Try testing with different brands of mouthwash and toothpaste to see which of these are more effective.


How does toothpaste clean your teeth? -

What are dental retainers? -

Retainers – what is a retainer? -

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Complexity level:
Project cost ($):
Time required:
1 hour for preparation, 8 days for experiment
Material availability:
Access to laboratory equipment (eg. petri dishes)
Safety concerns:

Always follow laboratory safety guidelines and always practice sterile technique when handling microbes. Never have any food or drink at your workstation and always thoroughly wash your hands with disinfectant soap or alcohol before leaving your workstation. Always dispose of used material in a biohazard bag. If none are available, the bacteria should be destroyed with bleach before being disposed of