That was a joke. Let me tell you the reason why it is funny...
Q: What is the best time to go to the dentist?
Q: What is the best time to go to the dentist? A: Tooth-hurty
This is a pun. The words "tooth-hurty" sound both like two-thirty, and "tooth hurt". Two thirty is a time (and a reasonable time to go to the dentist) and since dentists help people whose teeth hurt, "tooth-hurty" is sort of like saying "when your teeth hurt".