Crown loose, broken or lost: what helps now
Usually it is not the crown that is the problem, but the tooth underneath.
A crown that comes loose has rarely just grown tired. In most cases decay has formed underneath, or the cement has given way because the margin was leaky.
The crown has come off
Keep the crown, do not put it back yourself and do not glue it. The tooth stump underneath is sensitive; an appointment within the next few days is usually enough. Until then chew carefully on that side.
The crown wobbles
That is a warning sign, not a cosmetic flaw: bacteria gather under a loose crown, and the tooth underneath can be destroyed within weeks to the point where it cannot be saved. Do not wait.
When a crown is replaced
With decay at the margin, with a fracture of the veneer, with a poor fit – and when the gum has receded and the margin becomes visible. An intact crown is not replaced just because it is old.