Heavily decayed or repaired permanent  teeth have a poor chance of lasting a lifetime. Even though a filled tooth may initially feel as good as new,  even small repairs wear out and require replacement which often enlarges the amount of filling at the expense of the tooth. Eventually this can lead to loss of the tooth and the need for replacement. Dental implants can provide one solution to the problem but sometimes orthodontic space closure is a more biological  and sometimes cheaper solution.

Decayed and compromised teeth are not primarily an orthodontic problem but the extraction of such teeth and space closure can be a biological and financially sensible alternative to patching up poor teeth long term and eventual replacement.  Often the teeth involved are the first permanent molars because they enter the mouth from a very early age when diet preferences often orientated towards sweet things

When poor quality teeth dictate an extraction pattern the space created is not always in the ideal location for orthodontic tooth movements, so anchorage management using mini-implants or elastics between the dental arches may also be necessary.