She had the dentist look at her teeth during the checkup.

look 是动词，意思是"看、检查"，这里用原形是因为在使役动词 have 后面接动词原形。 at 是介词，表示动作的方向或对象，这里指"对...进行检查"。 have sb look at sth 是一个固定搭配，表示"让某人检查某物"。