Decayed teeth when not restored is undermined from inside and get broken at lightest forces

Get your teeth checked by a dentist. On examination, it's possible to come to a diagnosis followed by treatment. Cause of teeth breakage need to be evaluated.

It may be a fluorosis case...In case of severe fluorosis you can undergo veneering or capping of the required teeth followed by Root Canal Treatment.

If you have decayed teeth you should visit a dentist. The only solution to decay is removal of the affected part of the tooth and filling it with a material which restores your tooth. The more the tooth breaks and creates sensitivity issues the more probable the tooth will go into a root canal and crown which will make your tooth healthy again.