Open wide, please. Keeping a safe distance, this man is brushing the teeth of a hippopotamus at a wildlife reserve in Guangzhou, in Guangdong province, China. Hippos have 40 teeth, and with the only recorded bite measuring a colossal 8100 newtons, he can't be blamed for taking precautions.
The visible canines grow throughout the hippo's life, some reaching 50 centimetres in length. As the teeth don't yellow over time, such hippo ivory is popular with poachers, and used to be made into dentures – most famously for US president George Washington.
These ferocious fangs are used for fighting and for shearing off plants close to the ground. Hippo back teeth are often not seen, but these unsung heroes munch up the 40 kilograms or so of grass the animals can consume every night.
Hippopotamuses usually let eager fish and birds clean their teeth for them, but this one doesn't seem to be complaining about the human touch.
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