Sometimes we brushing our teeth too hard and it cause to damage our teeth, but dentists using sharp metal points to scrape our enamel off but why it don’t?
Brushing too hard, or with a hard bristle toothbrush, won’t damage enamel (the outer, protective layer of the teeth). It’s simply too hard of a material. It CAN however, damage the gum tissues and/or the cementum (a much softer layer that covers the root surface) of a tooth.
Brush too hard => damaged gums => recession => exposed cementum => damage or removal of cementum => sensitivity, root surface cavities (BAD!!)
For healthy individuals during a cleaning, yes the hygienist or dentist is carefully removing calculus/tartar (not scraping off enamel as op suggested) from the teeth. Even with these instruments, it is very difficult to damage the enamel.
For individuals with periodontal or gum disease, they often already have recession and exposed cementum (from the bone loss, recession associated with periodontal disease) and yes, we can do damage. In these situations, we will use an ultrasonic scaler to remove the calculus rather than scraping the teeth to avoid damaging these tissues.
TL: DR – just use a soft-bristle toothbrush, or even better, use an electric toothbrush that tells you if you are brushing too hard
Gum erosion is what you are trying to avoid with a soft brush and moderate pressure. The tooth under the gums doesn’t have the same protective coating and is super sensitive.
The enamel is super hard, actually harder than the metal equipment. The dentist / hygienist is carefully scraping around the gum line to ensure they don’t damage the gums.
Source: I suffer from gum erosion, my cousins are dentists, they explained a lot of this to me in detail.
So, if anything more than a soft brush is gonna risk damaging gums, etc., then why do they make, and every pharmacy ever carries, medium and hard bristle toothbrushes?
Who actually needs, or should use, a hard toothbrush — and what for?