Our company deals directly with this issue on a daily basis.  In my opinion, the dentist should not shoulder the full burden for things outside their control as many have stated here. 

I do believe, however, that the patient's basic desire behind this rule change request is for better communication and peace-of-mind when faced with the cost of a crown or bridge.  Perhaps they had a bad experience with a failed treatment? 

At any rate, if patients are demanding a higher level of assurance against life events (which are outside of the dentist's control), an alternative to a state mandated warranty is a third-party warranty or protection plan.  For example, our 5 yr protection plan covers the cost of all of the items listed by Dr. Hutchinson above, including trauma or accidents, bruxism, root canal therapy after a crown has been placed, recurrent decay, and others, and also gives the patient nationwide protection if they move. In this way, the dentist doesn't have to take on the added risk and cost of a mandated 5 year warranty, but the patient still has the extra assurance available.

I don't say this to promote our product, but just to point out that there are other ways of solving the issue then adding a regulation.