It’s Dental Health Week in Japan.

To learn how to stop cavities, kids at a zoo in western Japan practiced on some of the largest teeth in the animal kingdom.

They used a meter-long toothbrush to keep a safe distance from the hippo.

Whales got into the action at a nearby marine park.

Staff got them to open wide by tempting them with some tasty mackerel.

Dental Health Week continues through the 10th of June.