You know it's time to change your toothbrush when you look at it from the back and the bristles are sticking out from the sides.
It's time to get a new toothbrush when the bristles on the one you're using are not straight anymore.
ーYou know it's time to change your toothbrush when you look at it from the back and the bristles are sticking out from the sides.
「歯ブラシを後ろから見て、毛先がはみ出していたら、歯ブラシの替え時です。」
It's time to change your toothbrush で「歯ブラシを替える時です」
bristles で「（ブラシなどの）毛」
stick out で「はみ出す」
ーIt's time to get a new toothbrush when the bristles on the one you're using are not straight anymore.
「使っている歯ブラシの毛がまっすぐでなくなったら、歯ブラシの替え時です。」
It's time to get a new toothbrush で「新しい歯ブラシにする時です」＝「替え時」
ご参考まで！
カナダ 
