Activation time and material stiffness of sequential removable orthodontic appliances. Part 3: Premolar extraction patients

Introduction: The purpose of this study was to describe the movement of teeth adjacent to premolar extraction spaces during space closure with aligner appliances and then fixed appliances. Methods: The sample included 24 subjects from a larger study investigating an aligner system. All subjects had at least 1 premolar extracted as part of treatment. Dental casts and panoramic radiographs were measured for tooth tipping adjacent to extraction spaces at 3 treatment points: T0, initial; T2, end of aligners; and T3, end of fixed appliances. Chart records were reviewed for information about time in treatment. Results: Treatment with aligners resulted in significant tipping of the teeth adjacent to premolar extraction sites. When followed by fixed appliances, these teeth were significantly uprighted. Aligner treatment followed by treatment with fixed appliances took an average of 40 months. Conclusions: In premolar extraction patients treated with aligners, dental tipping occurs but can be corrected with fixed appliances. This dual modality treatment might require more time than treatment with fixed appliances alone.