Resorption isa normal and natural process in which teeth “dissolve” away under pressure from adjacent teeth e.g. baby teeth roots disappear under pressure from the second teeth coming through.
Occasionally Mother Nature makes a mistake and a permanent tooth damages another adjacent permanent tooth.
A damaged tooth will become loose like a baby tooth.
If seen early on x-rays, the tooth causing trouble can be moved away with braces or even extracted. If the problem is not seen until later in the process the damaged tooth will usually be lost.
Each resorption case must be assessed individually as they are very complicated situations. Your Orthodontist will give you a guide estimate based on their examination.
Unfortunately the tooth or teeth with the damaged root(s) will usually be lost.
Any damaged teeth that are extracted will need to be replaced with a denture, bridge or implant.