If you detect the crack early, a simple reinforcement could be to do a plastic filling over the crack. If the crack is bigger and more extensive, it could involve a dental crown, a porcelain crown or cap, or you could even have a porcelain inlay or onlay which is slightly smaller and not as aggressive as compared to a dental crown.
Another option is if the patient prefers to have a wait-and-see approach -- some patients might be willing to go through a procedure, especially if the tooth is not giving any pain, a simple way to prevent further damage to the tooth is to make a mouthguard that the patient can wear at night. A mouthguard can also be worn to protect teeth, to slow down the rate of deterioration of the tooth.