Explain SMBC — the wiki for Saturday Morning Breakfast Cereal

This comic shows a visit to the dentist. When told "How's my teeth?" the dentist responds that the patient's teeth are so bad that their condition cannot be conveyed in straightforward language -- it can only be communicated through "a list of elaborate metaphors." The patient then suggests the dentist could read some history in all the time they spend inventing metaphors, to which the dentist responds by offering to fill the patient's mouth with plastic so they "can go home." The patient accepts this. The humor plays on the stereotype that dentists lecture patients about oral hygiene, but inverts it: this dentist is so dramatic about the state of the patient's teeth that they resort to literary devices rather than clinical terms, and the patient would rather just get a quick fix than endure an elaborate poetic description of their dental decay. It also references the real practice of dental fillings in a reductive, absurd way.