Patients sometimes cannot understand how a crown that they paid $850 TWENTY FIVE YEARS AGO has worn out and needs to be replaced. People fully understand that their 15 year old $2500 refrigerator has 'died' but a crown should last forever. This photo is a picture of a tooth that had an old crown that had started to leak. This means that the metal in the crown had fatigued,became slightly bent and permitted saliva to get under the crown. You don't have to be a dentist to see the black part of the tooth near the bottom of the photo. That is what tooth decay looks like. Yes you could wait until the crown falls off when the decay becomes advanced but why would you? Patients usually understand when I ask them when was the last time that they had purchased only one set of tires in their lifetime? Everything a dentist does...including me...will fail. The definition of a 'good dentist' is a dentist that makes things fail at the slowest possible rate.