Crowns No Longer Match Natural Teeth
When your dentist placed your dental implants, they probably matched your natural teeth perfectly. Dental implants are an attractive tooth replacement solution, and often indistinguishable from natural teeth.
However, over time, they might not match as well. Usually, this is because natural teeth stain, while dental implants resist staining. For a while, teeth whitening might be able to keep the match good, but eventually the two will diverge. Especially once natural teeth start losing their enamel, which can make them look permanently yellow.
On the other hand, some materials used for crowns in the past might now have either stained or changed color with age.
In either case, you might want to replace the crowns or bridges on your implants to match your natural teeth.