A cracked tooth can sometimes be cosmetic, and sometimes can be more problematic. When a tooth cracks and the crack goes out to the side it usually in not painful. Most the time the crack will miss the nerve. When this happens there are different ways that the cracked tooth can be restored.
Cracked tooth (back)
When back teeth crack they typically have pain when you bite something. More specifically, when you bite and release is when the pain is noted. This is classic "Cracked tooth syndrome"
The typical fix for this is to place a dental crown, or cap on the tooth. This splints the tooth together, acting like a cast. When the cusps are splinted together they can not move and the pain goes away. With today's zirconia crowns you will barely be able to tell an difference between your natural tooth and the new dental crown.
Sometimes when the crack has been growing for a long time, it will get close to the nerve. When this happens a crown may not fix the problem. When it is close to the nerve we may need to preform a root canal. This is where we take the nerve out of the tooth so that you wont experience any dental pain.
Cracked tooth (front)
Cracked front teeth typically do not show signs of dental pain. When a front tooth cracks or breaks it typically is a cosmetic issue. With this type of cracked tooth you can do a bonding or veneer to restore the missing part.
Bondings typically are the cheapest option. They are susceptible to stain and wear though. Another option would be a veneer. A veneer would accomplish the same as a crown but is made of porcelain. Porcelain is stronger than a bonding and will not stain.