I do not believe placing a warrantee on dental work is a good idea.  The life expectancy of dental work is dependent on many factors, including a patients personal oral care, diet, alcohol consumption, smoking, hereditary and environmental factors, maintaining regular dental checkups, occlusal habits, to name a few.  Foods effect pH of the mouth, the potential for decay and the longevity of dental work.  Coffee, even without sugar, sodas with sugar and sugar-free, power drinks, all are very detremental to natural teeth and dental work.  A patient's lack of home dental care also effects the health of the teeth, dental work and periodontal health.  

   The location of a restoration can also be a factor in its longevity.  Patients who grind their teeth weaken and destroy fillings at a faster rate than those who do not.  Deeper restorations can have more potential for weakening teeth.  Teeth that have decay but are assymptomatic can become symptomatic when treated.  The number of restorations in the mouth, the presence of missing teeth, the presence of removable dentures all effect dental work longevity.

    In addition, treatments that are recommended by the dentist to preserve dental work and teeth are often not accepted by the patient, or are not done because the treatments are not covered by insurance companies.  At present, many dental treatments that are in the best interest of the patient are refused by insurance companies as unncecessary.  Were these treatments to be done, the overall health of the dentition and existing restorations would be improved.

   There are far too many factors associated with how well dental work will hold up in the oral environment to accurately ascertain the 'life expectancy' of dental work.  Trying to regulate such would only serve to create unrealisrtic expectations and reduced personal responsibility on the part of the patient.