Help ladies

Long story short me and my SO got into an argument 3 days ago, in the middle of the argument he threw my toothbrush away , so I did the same to both of his. I go out later that day and buy us both new tooth brushes. Okay.now it's been 3 days today and his toothbrush is still in the package and has not been used . Its fucking disgusting , only means one thing, he isn't brushing his teeth. I haven't said anything yet because it literally just occured to me this morning. It's just sick and how do I go about telling him about this.