If a baby first molar is lost early due to advanced decay, chances are that its replacement permanent tooth (the first bicuspid or premolar) may not be ready to grow in yet. Some thought must be given to the space resulting from the lost tooth. If the first permanent molar has already grown in, the missing-baby-tooth space can be left alone because the second baby molar will not usually drift forward. However, if the first permanent molar has not yet grown in, it may, as it erupts, push the second baby molar into the space of the missing baby first molar, thereby blocking the eruption path and creating crowding of the first bicuspid (the permanent tooth that should replace the missing baby first molar.)
In such a case, a space maintainer attached to the baby second molar is excellent until the first permanent molar erupts.
