Could use expert help with why are human teeth so fragile?

Human teeth: Human teeth are actually not fragile. The enamel covering is one of the hardest natural structures known to mankind. Perhaps compared to a steel girder you might consider it fragile. Humans who bathe their teeth in sugars and acids, don't brush and floss properly, ; don't see their dentist for routine check-ups, cleanings and treatment, suffer the ravages of dental caries due to their own neglect.

Fragile ?: Far from it. Your teeth are extremely hard and durable compared to any other organic substance in your body. It is the lack of proper care that causes their breakdown. Modern medicine has allowed us to live well into our 80's and 90's, requiring teeth to last 70+ years! it is the bacteria in your mouth that is the culprit.

Fragile teeth?: They are definitely durable, it is things we do to them, the way we mistreat them, fail to properly clean them, that causes them to breakdown. The masseter muscle, one of the muscles that moves our jaw bone, is one of the most powerful muscles in our body so our teeth better be tough! you probably know people in their 80's who still have their own. I would call that durable.