Part of it is genetics too - I've been cursed with deeply-pitted chewing surfaces that are prone to cavities. A sibling with the same diet was not, and has never needed a filling.
One of my biggest regrets in life is getting amalgam fillings as a kid. Not that I would have known any better, or been able to protest it (they were the cheap and affordable option, after all). But knowing that a mercury compound is in my mouth 24/7 is not comforting.
I am reassured by studies indicating there are no toxic effects[0], but it's still one of those backburner things that one thinks about every once in a while. This fear alone has done more to motivate me to floss and brush properly than anything else. Luckily, I haven't needed a filling in almost a decade - but if I do, it will not be an amalgam one.
Amalgam also requires larger fillings, meaning they remove more healthy tooth to fit it in. And the tooth has to be undercut a bit, since it doesn't bond like composite does. So amalgam also increases the chances of a tooth cracking later on and having to be replaced with a crown.
But! Composite also contains BPA or similar. So there's that.
Mercury (or rather, Thiomersal) hasn't been used in the vast majority of vaccines since the 90s. It was completely safe as far as we know, but was removed as a precautionary measure during a push to remove all sources of mercury from food and drugs.
One of my biggest regrets in life is getting amalgam fillings as a kid. Not that I would have known any better, or been able to protest it (they were the cheap and affordable option, after all). But knowing that a mercury compound is in my mouth 24/7 is not comforting.
I am reassured by studies indicating there are no toxic effects[0], but it's still one of those backburner things that one thinks about every once in a while. This fear alone has done more to motivate me to floss and brush properly than anything else. Luckily, I haven't needed a filling in almost a decade - but if I do, it will not be an amalgam one.
[0]: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3388771/