When I began to implement clear aligner treatment for patients in the mixed dentition, I realized the treatment design in Phase I treatment had to differ in several ways from adult and teen clear aligner treatment. A large difference was in the goals for final tooth positions. Unlike treatment in permanent dentition, early intervention requires we create space for permanent teeth that have not yet erupted, and in some cases, we have to handle the early loss of primary teeth. We cannot simply align the dentition and close all spaces. We need to manage arch length discrepancies. In Class II malocclusions, we address the molar position and often distalize the molars. To be successful in this treatment, we should set up proper force systems and follow some key principles for success.
Treating in the early mixed dentition can present some challenges due to shorter clinical crowns and control while opening spaces for erupting teeth. If we don’t select a proper attachment design, teeth can lose track. When we choose the appropriate attachments, these movements are more predictable, and we can alleviate common frustrations.
Opening anterior space
When there is early loss of a primary tooth, we will design the appliance to open space. For example, opening space for a lower right canine will need attachments on the first primary molar and lateral incisor. It is common for the lateral incisor to lag without these attachments and fall into the eruption compensation. The aligner can control both teeth during space opening by creating a mesial and distal point of the force application—place attachments on the mesial and distal of the space to achieve better results.
Class II correction
In many Class II cases, I find it effective to move upper molars distally. During Phase I treatment, we create a space mesial to the molar. This technique reduces the proclination of the anterior segment while achieving Class I molar position. It also creates sufficient space between the mesial of the molar and the distal of the lateral incisor to accommodate the premolars and canines. In these cases, it is helpful to have multiplane attachments on the second primary molar and the permanent molar to implement a proper force system. The two attachments leverage the active surfaces to deliver the distal movement and the desired space opening.
