Dental problem. teeth become fragile and crack, leaving a hole and sometime having inflammatory symptom causing toothache?

Dental treatment: Teeth do not become fragile and crack without some underlying dental problem, most often cavities. It sounds like you are in dire need of seeing a dentist who can tell you what the problem is and what needs to be done. If things are neglected, these broken, rotted teeth will become infected and may result in serious complications. Untreated dental infections have even caused deaths.

You may have decay: Teeth usually crack if there are large amounts of decay inside the tooth, which you can only see with an xray radiograph. See your dentist, and have a radiographic and clinical evaluation for any teeth that have decay. Have these teeth restored before they become a real big problem that will take lots of time and money to restore back to health. All the signs you have described a carious tooth.