Hello. You did not enter the poem this question refers to. This makes it impossible for your question to be answered. However, I will try to help you as best I can.
It is only possible to know the reason that left the toothbrush toothless if the poem is read. As you have not informed the poem, it is you who should read it. You will be able to identify why you left the toothbrush toothless, when you read an activity the speaker did with the toothbrush that ended up damaging it, or something that acted on the toothbrush, damaging it.
