I keep giving Dr. Teeth's parents new lore, I just really like them
Teeth gets his musical talent and fun loving from his father, Gerald, who settled down when he met Tina
When they were young, Gerald didn't take anything seriously, he partied, played music, and traveled, but then he met Tina, who was the exact opposite.
Tina was serious and hardworking, and she focused all of her time and energy on her studies and work instead of letting herself have any fun.
I like to think they initially did not get along, at all. Gerald thought she was a buzz kill, and Tina thought he was ridiculous and a lost cause. Over time, however, Gerald got her to loosen up and enjoy herself, and Tina got him to settle down and take things seriously, and they balanced each other out.
Gerald was broke and living out of his van when they first met, often playing music for food or money, but when he locked in and went to school for dentistry with his girlfriend, his life became more stable and it was easier for him to afford nice things.
When they had Gerald Jr. (Dr Teeth), Tina already wanted him to be a dentist like the two of them, and Gerald agreed, but mostly because he had lived a poor van life, struggling for food and a roof over his head, and he didn't want his son to struggle like he did.
I think that's why it was Gerald in the end who told his son, 'No, you should play music, it's what you're good at,' because he saw a lot of himself in Teeth, and he saw that not only was he successful already, but it was what made him happy.