Crowns, bridges, partial dentures and dentures, etc. are services, not consumer products. Having to warranty not only the crown but all of the associated costs would greatly increase fees to patients.

Also, for those patients with low insurance  fee schedules and especially Medicaid patients, access to care would be severely restricted.

The regulations to address all of the possible scenarios involved with crown failures would be hundreds of pages long and in the end will still end up being an ethical decision as to the reason for a failure.

I personally use a lab that guarantees their crowns and bridges for five years against porcelain fracture, etc. providing the patient has been on a regular recall schedule. I have no problem with making crowns over when the problem was not caused by neglect or abuse.

It would be interesting to see how the orthopedic surgeons would feel about an all-inclusive warranty on hip and knee replacement.