system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do the skeletons of people that died hundreds of years ago have perfect white teeth but mine will yellow within days without brushing?

I always thought it was strange that photos of ancient corpses or skeletons from (literally) ages ago are dug up by archaeologists and seem to have great teeth! And yet i have to brush twice a day and mouthwash to maintain "kinda" white teeth..
gpt
You are alive. You are constantly exposing your teeth to food and other habits that can stain them, and you are providing a nice, warm, wet environment perfect for bacteria growth which can lead to plaque and cavities.

Skeletons are, well, dead. They are not constantly eating. Their mouth is not a nice warm wet environment. Bacteria cannot really survive long in that environment.