The cases we do at the office are usually completed in one and half years.  We rarely will put braces on till all the baby teeth are out.  The reason for this is because if you place braces on a child with baby teeth, then the will most likely need braces again when the baby teeth fall out.  This is when you hear the dentist say that they will do the case in stages.  We believe that a child should not have to go wearing braces for four to five years.  They easily get burnt out and at times become non compliant which only delays treatment and becomes frustrating to all involved.  

There are exceptions to this rule of thumb.  One of them is if a child has a crossbyte.  This needs to be corrected after the 6 year molars have erupted in.  Most posterior crossbytes are corrected by a palatal expander.  This is worn for roughly 6 to 9 months then removed.  Another exception is when the teeth are so misaligned that the child self esteem can suffer.  Then it is recommended to fix that misalignment so that the child's self esteem does not suffer.