In science, years 3 and 4 have been learning about teeth. 

Since eggs are made of a similar substance they used boiled eggs to conduct their experiment. 

An egg was placed into a jar containing either water, milk, orange juice, Coca-Cola or vinegar. Each day for a week, the eggs were observed to see if any changes had happened to the shells. 

Results: After 5 days, the water and milk did not damage the egg shells but the egg in the cola turned a dark brown. The shell of the egg in the orange juice was partially dissolved and the egg shell in the vinegar was completely dissolved away. This was interpreted as milk and water being the healthiest for your teeth.