If baby teeth are lost early then the permanent 1st molars may drift into their space. The critical tooth to consider is the deciduous 2nd molar which is the most posterior baby tooth in each arch. If an anterior tooth is lost early it may be an esthetic issue or may delay the eruption of a permanent tooth as the gum tissue has healed over, but it is usually not an orthodontic issue. If the permanent molar drifts into the position of the baby molar then the 2nd premolar will be impacted and there will be an overall loss of space for the permanent teeth. Failure to maintain this critical space may mean more complicated orthodontic space regaining later or even extraction of permanent teeth. A variety of removable or permanently cemented appliances may be used to maintain the space.
A related issue is the preserving of the excess space when the baby molars are lost. Orthodontists refer to this as “leeway” or “e” space. Children normally experience an “ugly duckling” phase as the larger permanent incisors replace the smaller baby incisors. The reverse situation happens in the posterior portion of the mouth as the permanent premolars are smaller than the deciduous molars. Preserving this space with a Lower Lingual Holding Arch can help avoid extractions and prevent aligning the incisors forward into thin gum tissue and causing recession.