how to know my teeth crack?cause mostly dentist is difficult to diagnose and can not seen in x-ray?

Whenever biting pressure is placed on a cracked tooth, there will be pain. Some dental offices have a plastic gadget that is placed on the suspected tooth and when the patient bites down on it, the tooth will hurt if it's cracked. Cracks can sometimes radiate towards the pulp or nerve and if it does reach the pulp, a root canal will be necessary (or extraction). The usual treatment for a cracked tooth is to have a crown placed on it to stop the crack from getting worse.

There are different patterns of cavity growth. Sometimes the widest point is at the surface, and therefore easy to see, and sometimes the widest point is further down... The latter kind sometimes has such a small opening that you can't tell if it's a cavity or just a stain. So a tooth can be compromised as far as structural strength, but look fine. That matters because when you get a root canal, first they need to know if the tooth in question has enough strong healthy dentin left to handle the restoration they want to do, or if it will just break soon enough that an implant would be more sensible. Then they want to know if the tooth it touches when you bite has any cavities - so they know if that one is likely to end up broken... Crowns rarely end up exactly the same shape as the original tooth, they have minimum thickness rules to keep them from breaking, and the rules depend on the material. But if the dentist knows that, say, the canine he's crowning touches a canine that is weak/transparent on x-ray (whether or not it has cavities) he can put priority in keeping them from touching. Hard crown materials can be too tough for a weak tooth to bite on. Some dentist take too many x-rays, or charge for too many (dental school I go to only charges for x-rays that turn out clearly enough to be useful, but some dentists charge you if they have to re-take!), but dentists that take NO x-rays are crooks! They are getting people who are being frugal to part with their cash for a procedure without checking to see if the x-ray says the procedure will fail! The dentist can't tell if a crown would be a waste until they check x-rays. The symptoms you looked up, btw, are for acute problems, and not all symptoms present in all cases. I had a cavity progress to a broken tooth before I felt any pain, for instance. And sometimes pain is (unintentionally) ignored - I went a few weeks with my mouth so dry I kept coughing before I realized that #1 I wasn't drinking enough water, and #2 when I did even lukewarm water hurt if I didn't chug and get it out of my mouth asap. And for my root canal... the student that did it had always been told to remove weakened enamel around a cavity when making a filling, in order to clean it up. The instructor *looked at the x-ray* and told him to only take off a bit, because the weakened enamel went far enough around my tooth that he would just end up damaging my tooth more. A dentist not taking x-rays is like a general doctor not taking your pulse. Yeah, x-rays cost money and a pulse check doesn't, but that doesn't change the fact that without either, you are in the dark.

If you bite down with something (tooth pick) on the suspected cracked tooth, when you open if it hurts like hell it's cracked.