Answer: 4.

The first one was stuffed into his pants pocket, then broken cleanly in two when he flopped from the sofa onto the floor. Just messing around.

Number two is somewhere at the Seattle-Tacoma International Airport.

He removed the third one at school before lunch, put it in his pocket (again!) and got up without replacing it in his mouth where it belonged.

So the fourth will be ready on Thursday, and the dentist informs us Turbo has set a new record.