This is the 4814th most frequent Russian word.
зубами
"Зубами" means "with (the) teeth" in English.
The word 'зубами' is used instrumentally to describe how the action of cleaning teeth is performed by using one's teeth, although in practical sense, it might imply biting or using teeth unconventionally.
Он чистит зубы зубами.
He cleans his teeth with his teeth.
Here, 'зубами' indicates the means — teeth — by which the child is holding the toy. It is in instrumental case showing the method or agent of the action.
Ребёнок играет с игрушкой, держа её зубами.
The child plays with a toy, holding it with his teeth.
In this sentence, 'зубами' means 'using teeth' and refers to the instrumental means by which the puppy pulls the rope, illustrating practical usage of the word in describing an action.