The Tooth Fairy and the Teeth Takers by Samuel Langley-Swain

Having lost a few teeth before, Ollie and Grace know the routine of leaving their teeth out for the tooth fairies to collect and swap for coins, but one morning they wake up to find nothing! Grandpa suspects those sneaky Teeth Takers are at play, creeping around in their fluffy slippers. When they take a trip to The Royal Mint to investigate further, they see the rotten Teeth Takers sneak in! But this time, the dragon keeping watch has other ideas.