小孩子换牙齿的时候，要注意口腔卫生。

xiǎo háizi huàn yáchǐ de shíhou, yào zhùyì kǒuqiāng wèishēng.

When children are losing their baby teeth, they need to pay attention to oral hygiene.

他笑起来露出一排整齐的牙齿。

tā xiào qǐlái lòu chū yì pái zhěngqí de yáchǐ.

When he smiles, he shows a row of neat teeth.

医生建议每半年检查一次牙齿。

yīshēng jiànyì měi bàn nián jiǎnchá yí cì yáchǐ.

The doctor recommends having your teeth checked every six months.