UV-C Mouthguard Decontamination Project

ISEF Category: Translational Medical Science

Subcategory: Disease Prevention  ·  Difficulty: Intermediate  ·  Setup: Home Setup  ·  Time: 1 to 2 Months

The Hook

Shared mouthguards and retainers can act like tiny apartment buildings for microbes. That makes cleaning them a real health question, not just a hygiene habit. You can turn that question into a measurable project by testing how UV-C light changes a biofilm over time. The best part, you can do it with low-cost tools and careful imaging.

What Is It?

This project tests whether a small UV-C-LED chamber can reduce a surrogate biofilm on dental appliances. UV-C is a type of light that can damage genetic material in microbes, which makes it useful for disinfection. Your job is to see how the visible structure of the biofilm changes with exposure and to find a safe, practical exposure range.

Think of the biofilm like a sticky city wall. The bacteria and proteins are packed together, so a cleaner has to break through the whole structure, not just touch the surface. You will not be counting every microbe directly. Instead, you will use a safe stand-in, like kombucha SCOBY or yogurt, and track changes with photos and image analysis. That gives you a way to compare conditions without needing a professional microbiology lab.

The real research question is about balance. Too little UV-C may not change the biofilm much. Too much exposure may be unsafe for people or may damage the appliance. That makes this a good project for learning how engineers and health researchers think about dose, effect, and safety at the same time.

Why This Is a Good Topic

This is a strong science fair topic because you can test a clear variable, UV-C exposure, and measure the outcome with images and simple analysis. It connects to a real problem, since mouthguards and retainers can collect microbes and are often cleaned poorly. You can also make the project your own by comparing materials, chamber designs, or exposure patterns. A student can learn experimental design, image-based measurement, and safety thinking without needing advanced equipment.

Research Questions

• How does UV-C exposure time change the visible coverage of a kombucha-SCOBY biofilm on a curved surface?
• What is the effect of chamber distance from the UV-C-LED on surrogate biofilm reduction?
• Does reflective lining inside the chamber change the rate of biofilm change compared with a non-reflective box?
• To what extent does biofilm thickness affect how much visible change appears after the same UV-C exposure?
• Which surrogate, kombucha-SCOBY or yogurt, shows a clearer and more repeatable response to UV-C treatment?
• How does repeated short exposure compare with one longer exposure at the same total dose?

Basic Materials

• UV-C-LED module with documented wavelength and power output, from a reputable seller.
• Opaque enclosure or small lightproof box.
• UV-blocking goggles rated for the UV-C source.
• Nitrile gloves.
• USB microscope.
• Smartphone or digital camera with fixed exposure settings.
• White background or light tent.
• Metric ruler or calibration target.
• Kombucha SCOBY or plain grocery-store yogurt as a surrogate biofilm.
• Clean plastic coupons, petri dishes, or other flat test surfaces.
• Timer.
• Black tape or foil for light sealing.
• Lab notebook.
• Computer for image analysis.

Advanced Materials

• UV-C radiometer or dosimeter for verifying exposure.
• Spectrophotometer or plate reader for absorbance checks, if available.
• Incubator for controlled culture or drying conditions, if your school allows it.
• Agar plates and safe nonpathogenic environmental isolates, only if your lab supervisor approves.
• Autoclave or approved sterilization access for waste.
• Reflective chamber materials for controlled optical testing.
• Calibrated scale or thickness gauge for surrogate material preparation.
• Image calibration standard for quantitative microscopy.
• Spreadsheet software or statistical software for dose-response modeling.
• Safety shield or interlocked enclosure for UV work.

Software & Tools

• ImageJ: Measures biofilm area, contrast, and texture changes from microscope photos.
• GeoGebra: Helps you graph exposure curves and compare trends.
• Google Sheets: Organizes trial data and calculates averages, spreads, and percent change.
• R: Fits dose-response models and tests whether exposure differences are real.
• Python: Automates image processing and compares repeated trials consistently.

Experiment Steps

1. Define the one outcome you will measure, such as visible coverage, darkness, or texture change in the surrogate biofilm.
2. Choose the chamber design variable you will change first, such as distance, reflection, or exposure pattern.
3. Build a calibration plan so each photo uses the same lighting, magnification, and background.
4. Set up controls that separate UV-C effects from drying, handling, and normal time change.
5. Plan a dose-response framework that lets you compare short, medium, and long exposures on the same scale.
6. Decide how you will analyze images and report uncertainty, so your results turn into numbers instead of impressions.

Common Pitfalls

• Using changing room light during photography, which makes biofilm images look different even when the sample did not change.
• Treating the surrogate like a real sterilization test, which overclaims safety or antimicrobial effectiveness.
• Placing samples at slightly different distances from the UV-C source, which changes dose and breaks comparison.
• Forgetting that curved retainers and mouthguards create shadows, which can hide parts of the biofilm from the light.
• Skipping UV safety checks, which can expose your eyes or skin during setup and testing.

What Makes This Competitive

A stronger version of this project goes beyond, “Does UV-C work?” and asks how dose, geometry, and surface shape change the result. You can raise the level by building a real calibration curve, using blinded image scoring, and comparing at least one design change in the chamber. Careful controls matter a lot here, because shadows and distance can change the outcome. If you also connect your results to practical cleaning limits for dental appliances, the project feels useful, not just technical.

Project Variations

• Test the same UV-C chamber on clear aligners instead of mouthguards to see whether shape changes the cleaning pattern.
• Compare a reflective chamber interior with a matte black interior to measure how bouncing light changes surrogate biofilm reduction.
• Use a bacterial-safe dyed gel or food-based coating as the surrogate and analyze color change instead of microscope texture.

Learn More

• CDC Dental Health Resources: Search the CDC site for guidance on retainer, aligner, and mouthguard hygiene.
• NIH PubMed: Search for review articles on UV-C disinfection, biofilms, and dental appliance cleaning.
• NOAA UV Safety Basics: Find background on UV radiation and safe handling of UV sources.
• NIST Image Analysis Resources: Look for free guides on image calibration and measurement practices.
• Journal of Dental Research: Search the journal for studies on dental appliance biofilms and disinfection methods.