Body & wellness activity
Teeth and Smile Science
Meet your teeth! Count them, feel their different shapes, and practice the right way to brush.
Materials and setup
- mirror
- kid-safe toothbrush and fluoride toothpaste
- 2-minute timer or song
- hard-boiled eggs (3 for Upper Elem; 1 for Kinder)
- clear cups
- cola and orange juice (Upper Elem)
- plaque-disclosing tablets or rinse (Early Elem; available at pharmacy)
- paper and pencils
- kitchen scale and pH strips (Upper Elem, optional)
Parent note
Disclosing tablets are safe to swallow but can temporarily stain lips and counters — use over a sink. Enamel-erosion experiment uses hard-boiled egg shells as an analog; mention to the child that real enamel is even harder than eggshell, but the chemistry is similar.
How this changes by age
Pre-K (ages 3–4)
Meet your teeth! Count them, feel their different shapes, and practice the right way to brush.
Steps
- Look in a mirror together. Open wide and count top teeth, then bottom teeth. A young child usually has 20 baby teeth.
- Feel three tooth shapes with a clean finger: in the front (flat, sharp for biting), on the corners (pointy for tearing), in the back (wide, bumpy for grinding).
- Name the three jobs: cutters (incisors), tearers (canines), grinders (molars). Say the kid words first; the big words can come later.
- Brushing practice: use a kid-safe toothbrush and a rice-grain-sized smear of fluoride toothpaste. Brush for 2 minutes using a timer or a 2-minute song. Small circles on every tooth — outside, inside, and tops.
- Finish with a 'tooth inspection': child shows their smile and parent cheers: 'Clean top teeth! Clean bottom teeth!'
Learning objectives
- Count own teeth and recognize that baby teeth are a complete set
- Identify three tooth shapes and their jobs
- Brush independently for a full 2 minutes with parent supervision
Kindergarten (ages 5–6)
Start a 24-hour 'egg tooth' experiment to see what soda and juice do to tooth enamel. Learn the story of baby teeth versus adult teeth.
Steps
- Introduce the 2-tooth story: kids start with 20 baby teeth and eventually grow 32 adult teeth (including wisdom teeth). The first adult tooth usually arrives around age 6.
- Set up the experiment: place a hard-boiled egg in a clear cup. Eggshell is mostly calcium carbonate — similar to tooth enamel. Cover the egg completely with cola (or another dark soda).
- Predict together: what will the egg look like tomorrow? Write the prediction down.
- Brush teeth properly right now — 2 minutes, small circles, every surface, then spit but don't rinse (lets fluoride work). Celebrate a thorough brush.
- Revisit the egg after 24 hours. The shell will be stained and softened. Explain: 'Soda sugar feeds mouth bacteria that make acid, and soda itself is acidic. That's what happens to teeth without good brushing.'
- Draw a before/after picture of the egg and write one sentence about what you learned.
Learning objectives
- Explain the difference between baby teeth and adult teeth
- Observe enamel-like material reacting to an acidic/sugary liquid
- Connect experiment observations to real-world tooth care
Early elementary (ages 6–8)
Use a plaque-disclosing tablet to find where your brushing misses. Map your personal cavity-risk zones and fix them.
Steps
- Brush your teeth normally for 2 minutes as a baseline.
- Chew a plaque-disclosing tablet (available at pharmacies) or swish with a plaque-disclosing rinse. Spit out and rinse with water. Any remaining plaque turns bright pink or blue.
- Look in a mirror. Draw a mouth diagram on paper with 32 tooth positions. Shade in every spot that turned pink — these are your missed areas.
- Identify patterns: which areas did you miss? Common ones are the gum line, back molars, inside surfaces of bottom front teeth, and where teeth touch.
- Re-brush carefully, targeting only the missed areas. Try small circles at the gum line, angle the brush at 45° into the gums, and brush behind front teeth with the toothbrush tip.
- Use the tablet again 3 days later. How many fewer pink spots? Track it weekly for a month.
- Research: what exactly IS plaque? (A sticky film of bacteria plus leftover food. Over time, it hardens into tartar, which only a dentist can remove.) Write 3 sentences.
- Extension: compare to flossing. Use floss once and see if the disclosing tablet reveals less plaque between teeth than before.
Learning objectives
- Use a disclosing agent to identify brushing blind spots
- Map personal cavity-risk areas onto a tooth diagram
- Describe what plaque is and how brushing + flossing remove it
Upper elementary (ages 8–10)
Run a 3-liquid enamel-erosion study over 3 days. Quantify the damage, research fluoride, and write a science-fair-quality lab report.
Steps
- Set up three identical containers. In each, place a hard-boiled egg fully submerged in: (A) cola, (B) orange juice, (C) water (control). Label and photograph each at hour 0.
- Record observations at 24, 48, and 72 hours: color change, shell texture (use a fingernail to test softness on a small area — do not damage the whole shell until day 3), smell.
- At 72 hours, remove each egg. Attempt to gently scrape one shell with a plastic spoon — measure approximately how much shell comes off by weight (use a kitchen scale). Record mass of shell removed.
- Build a data table: liquid, pH (look up or test with pH strips if available; cola ≈ 2.5, OJ ≈ 3.5, water ≈ 7), color change score 1-5, softness score 1-5, shell mass removed (g).
- Graph the results. Cola should show the most erosion, OJ second (acid without sugar still erodes), water minimal.
- Research fluoride: how does fluoride strengthen enamel at the molecular level? (It replaces hydroxyl groups in hydroxyapatite to form fluorapatite, which is more acid-resistant.) Write a paragraph.
- Full lab report (2 pages): hypothesis, materials, method, data table, graph, conclusion, error discussion (e.g., hard-boiled egg shell is not identical to live enamel; boiling affects the shell), and one real-world recommendation based on your data.
- Extension: research 'acid attack window' — saliva takes ~30-60 minutes to neutralize mouth acid after a sugary/acidic food. What does that imply about when to brush? (Answer: wait 30 min after acidic food, or brushing scrubs softened enamel away.)
Learning objectives
- Design and run a multi-condition enamel-erosion experiment with a control
- Collect quantitative data (mass, pH) and present it in tables and graphs
- Explain fluoride's protective mechanism at a basic chemistry level
Safety and evidence note
Read the full activity before beginning. An adult should supervise tools, heat, food, outdoor work, movement, and experiments as appropriate. Completion records that the activity was done; the child’s explanation, work sample, photo, or demonstration is stronger evidence of learning than a completion check alone.
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