The vast majority of crowns and bridges endure at least five years and many laboratories provide such a guarantee. Many insurance companies will only reimburse dentists for a new crown  5 years after a crown was placed on a given tooth. However, the laboratory crown guarantee requires that a patient show proof of regular dental visits every 6 months. Even with regular dental cleanings and check-ups every 6 months, a  dentist cannot guarantee that tooth decay, periodontal disease or a fracture will not occur to destroy the tooth itself which then causes the crown or bridge to fail. Today's dental patients include many who are taking  one of the more than 500 medications known to decrease the flow of saliva which in turn increases the rate of tooth decay. After age 50, the mineral composition of teeth changes and makes  teeth more prone to fracture. Periodontal disease can also cause a major periodontal defect within a short period of time which then condemns the tooth to extraction. It is therefore not possible to guarantee anything for any period of time in dentistry. Durability of dental treatment varies with the condition of the tooth when treatment is rendered and  with the dietary  and oral hygiene habits of the patient. Requiring a 5 year guarantee for all crowns and bridges will foster the unnecessary extraction of slightly questionable teeth and their replacement with implants. This will  increase the cost of dentistry to the patient and to society.