How often should a dental bridge be replaced?

I have seen bridges last for 30 plus years and I have seen some last only a couple of years.  There are several factors that determine the longevity of a bridge all of which would take too long to discuss.  What I will tell you is that over the last several years dental implants are becoming the treatment of choice over dental bridges.  In my practice, the only time I recommend a bridge over an implant is when the patient does not have enough bone for an implant.  With the advancements in ridge augmentation (bone grafting) and implant design the lack of bone is not an issue very often anymore. Definitely look into dental implants before you replace that bridge.   

While mileage will vary from person to person, bridges can last from a few years to a few decades.  There really is no "should".

People that grind and clench their teeth will have more wear and tear compared to people that don't, so restorations won't last as long.  Young patients can expect to replace them a few times in their life, while people in their 60's or 70's may never need to replace them.

Material selection can influence as well, since porcelain CAN chip and all-metal will not.  Type of cement is a factor too.

If the bridge is fitting well and there are no breaks, leaks or cavities around it, then it could still last for years.

However, oftentimes there are "aging" changes in the mouth over the years.  The gums recede, the space under the false tooth (called "a pontic") enlarges and starts to trap food under it.  If the bridge is a porcelain bridge, oftentimes it will no longer match the color of the adjacent teeth.  Over time, if the patient hasn't done a great job with their oral hygiene around the bridge cavities can occur.  If the teeth have shifted or moved, the bridge may no longer support the bite properly.  So, for a number of different reasons your dentist may suggest replacing an old bridge.

There is no "average" life expectancy for a bridge.  I've seen some need replacement after only five years, and seen others that was still serving the patient well after thirty years.  Your dentist should be able to explain to you his reasons for recommending the old bridge be replaced with a new one.