Its hard to say. There's a lot of possibilities for failure. There could be pain, swelling, the tooth may break, it could get loose, etc.
Thank you so much..there are about 10 mm or more....i think that i may go for the crown but how long will it take to discover the failure or the successof it after putting the crown?
Its hard to detect a crack on a tooth even with an x-ray because an x-ray is a two dimensional picture of a three dimensional object so cracks can easily hide. It sounds like your two options are an implant or a root canal/crown type of treatment. If there's sufficient tooth structure and you don't mind taking a risk, the root canal/crown may be the better option. But there's no way to guarantee success with that treatment due to the inability to know how deep the crack is and whether or not it is completely removed.
An implant would be a better, more predictable option but would require a good dentist to perform it to maintain the gum/bone health after the implant is placed. An improperly placed implant can result in some gum/bone recession and since its a cosmetic area, I would opt for the crown/root canal. But again, there's no way to say that it would be successful.