Dexter told Delilah that it is very important that she keep her mouth clean. She also needs to take care of her teeth by chewing on things to remove that horrible plaque build-up. He warned her that if she doesn't follow his example, she could end up at the Vet's office for a cleaning.
A dental cleaning is terrible. He hasn't had one himself, but when he was in the pound before he was adopted, one of the other cats gave him this same advice. His experience had been so bad, that when he woke up, one of his fangs was missing.
Then Dexter showed Delilah his sparkling white teeth and his long, healthy-pink tongue. He encouraged her to follow his lead and keep her mouth clean.