That is a question that has a lot of different aspects to the answer.
Let me start by addressing the word “permanent”. When we place a filling or a crown or a partial denture or a denture, or any of the numerous services we provide, most are considered permanent. However “permanent” does not mean “for life”. If means for the lifespan of the particular service and material used. An example would be a silver amalgam filling. One of my textbooks back in school told us that the expected lifespan of a silver filling is 10-12 years. In real life, I see some silver amalgam fillings that are 35 or 40 years old. They are still there, and still providing a good service. But they are not as strong or well-sealed as they once were, and quite probably should be replaced.
Likewise, I have seen silver amalgam fillings that need to be replaced after just a few years. What is the difference?
There are many factors involved: How well you take care of your teeth; What and how you eat; unconscious habits like grinding or clenching; Conscious habits like chewing fingernails or pens or toothpicks; How well were the original fillings done; There are also traumatic injuries, and cracked teeth.
Think of your car, or your refrigerator, or your favorite pair of shoes. If you get 10 years and 200,000 miles out of your car, you will quite probably buy the same make again. If your refrigerator lasts 15 years, you will think it is a great ‘fridge. And if you wear those comfy shoes until they fall apart, you’ll go buy another pair, and wear those out too!
But if a crown or a filling only lasts 21 years, you will likely think that is a bad thing, and wonder why it didn’t last longer. Yet it actually provided you YEARS of quality service.
Crowns are made from several different materials in today’s dentistry, for several different reasons. We can make all-ceramic crowns for your front teeth, and all-ceramic crowns for your back teeth. They are beautiful, but may not be as strong as some other materials. We can make all-metal crowns, with varying percentages of high-noble metals (like gold) depending on the location and need. These are MUCH stronger crowns, but obviously not tooth-colored. We can make crowns that are porcelain on the outer surface, and metal or zirconium on the inner surface. Again, stronger than all-ceramic, and more beautiful than all-metal. And remember, porcelain is glass, so you must consider what you chew and do with porcelain much more than you have to with all-metal.
As far as the lifespan of these crowns is concerned, it varies just like the lifespan of a filling. It will depend on many different factors, and those factors will vary from person to person.
So are they “forever” permanent? Probably not. But can they last for a long, long time? Absolutely! And we can help you be certain you are caring for them properly to increase their lifespan.