Why do my cerec crowns keep cracking?

Cerec crowns are a fantastic option to have for a patient. They are typically made of lithium disilicate ceramic which is highly aesthetic/beautiful, and is very reliable in the proper situations. The other benefit of cerec crowns is that they can be finished in one day which saves the patient from having to wear a temporary crown for a few weeks. The unique thing with cerec crowns are they are very technique sensitive. They require the dentist to shape the tooth into very specific parameters underneath the cerec crown. The dentist has to be skilled and precise in making sure the tooth has a specific reduction shape and has no sharp edges, lines, or undercuts. The dentist must also evaluate if the patient's bite forces or grinding forces are too great to place a cerec crown on a molar or premolar.Where you have had two crowns fracture so recently, you may want to get a second opinion just to ensure that your crowns will predictably last in the future.

It sounds like you have a problem with your bite -- the way your teeth touch. In addition the dentist may not have allowed enough room for a thick enough cerec restoration. Overall I would suggest finding a new dentist who has experience with working with and possibly changing the bite.