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Class II nonextraction treatment, which commonly includes distal movement of the maxillary molars to correct the molar relationship, most often can be successful when treatment is started in the late-mixed dentition stage of development. At least two factors contribute to this success. One is that the molars can be distalized routinely at this age. The second is that the "E" space is available and can be used either to help correct the molar relationship or to resolve any crowding that may exist. This article describes and illustrates the treatment of a late mixed-dentition patient with this type of Class II nonextraction treatment that includes distal movement of the maxillary molars with a 100 g NiTi coil system and the maintenance of the "E" space with a lip bumper.

The leeway space provides adequate space to resolve crowding that is present in the mixed dentition in the majority of individuals. This space can be maintained by preserving arch length with a lingual arch as the primary teeth begin to exfoliate, unless conditions such as the premature loss of a primary canine require earlier intervention. A lip bumper can also be inserted after the eruption of the first premolars to preserve arch length.