“When should a crown be replaced?”

Only if it or the tooth under the crown fails.

Crowns last a long time. Most important is to keep the tooth that the crown is placed on healthy, cavity-free and with healthy gum tissues and bone surrounding it. The crown has the potential to last the rest of your life, but it depends nearly completely, on the health of the tooth on which it is connected.

Crowns are replaced when portions of them chip or break in critical areas (somewhat rare), if cavities happen along the gum line or in between teeth and cannot be accessed for repair without removing the crown. Crowns can also be replaced if your teeth change color and no longer match the crowns (replacing the crown to get a better color is usually optional).

The crown should be replaced when it is no longer protecting the supporting tooth structure. Crowns have to endure an incredible amount of force and constant attack by bacteria normally found in the mouth. Depending on how you take care of it and its location a crown is expected to last 10-15 years. It is not uncommon for them to need to be replaced after 5 years though.

Crowns must be replaced if there is decay, or causing gum disease, or there is odor coming when flossing, at other times when cosmetics are issue, and you are not happy with the looks, that might require a redo of crown, for much more info on when to change crown click here: https://celebritydentist.com/porcelain-crowns/

When it fails