The succes vs. failure of a medical procedure is governed by many factors, this also holds true for dental procedures.  The patient's biology plays a key role in the success or failure of dental procedure just as it does when a medical procedure is undertaken.   As with medical procedures there are rates of success and failure associated with dental procedures and therefore there can be no waranty associated any dental procedure.  Certainly if a patient believes he or she has been misdiagnosed, mistreated or malpracticed, he or she could and should pursue this.