why are my crowns breaking so soon?

They could be breaking for four different reasons:  1) your bite (are you a grinder or clencher?)  2) the actual defect may be a result of the way the dental lab made your crown 3) the type of material and crown that your dentist and you chose to have it made out of  4) how good your dentist is?  Did he prepare enough of the tooth so that you have enough crown thickness for strength?  Was your bite adjusted so that you are not putting undue forces on the crown that could weaken it?If it is a gold crown, then you should have no problem with breaking.There is a very esthetic all porcelain crown out right now that is made of EMax porcelain and is very strong.There is also a type of tooth colored crown call zirconia that is EXTREMELY STRONG AND DURABLE, however it is often not as lifelike as other types of porcelain crowns for teeth in the front of the mouth.