King Dedede brags to Escargoon about eating all the junk food he wants without getting cavities. Back at the house, Tuff has a similar mindset as King Dedede, stating that it's not important to brush his teeth. His family, and Kirby, show him the right way to brush his teeth. Despite their example, he doesn't brush his teeth properly.
This representation of cavities and bacteria shows workers chipping away at King Dedede's teeth. Dedede's reaction shows how painful a cavity can be: it affects his sleep. Dedede and Tuff are both scared of going to the dentist and try to avoid it.