Narrated Abu Musa (may Allah be pleased with him): I came to the Prophet (peace and blessings of Allah be upon him) and saw that he was using a miswak in his hand and cleaning his teeth, and he was saying "Aa, Aa," and the miswak was in his mouth as if he was about to vomit.

Narrated Hudhaifa (may Allah be pleased with him): When the Prophet (peace and blessings of Allah be upon him) would get up at night, he would rub (clean) his mouth (teeth) with a miswak.