Aligner therapy is increasing in popularity among patients and practitioners. Several systems now exist including Invisalign®, ClearCorrect®, and Simply 5®. Clear aligners provide patients the benefits of improved gingival health and oral hygiene,53 but many challenges exist when using aligners for orthodontic tooth movement. Moving teeth with plastic aligners often results in the need for re-assessments in the middle of treatment. The Invisalign® system has titled these re-assessments Mid-Course Corrections or Refinements. OTM using Invisalign® is planned using the ClinCheck™ software. This software and the technology for Invisalign® is constantly changing and evolving. The initial ClinCheck™ is designed by a technician, using the preferences and treatment plan provided by the practitioner. At present, this software allows practitioners to move individual teeth in almost any direction and apply attachments, precision cuts, or interproximal reduction where desired (Figure 3). It is important that general practitioners using this software and system understand the basics of orthodontics in order to provide patients the most optimal treatment. This includes an understanding of diagnosis, ideal occlusion, and the limits of tooth movement and aligner therapy.
Initial studies of Invisalign® reported OTM accuracy to be 41% of the ClinCheck™ predictions. The most predictable movements included lingual constriction, while least predictable movements were tooth extrusion and canine rotation.54 Changing aligners every 2 weeks versus every week doubled the likelihood that patients could complete their treatment without correction55 and with improved outcomes.53 A series of studies conducted at University of Florida College of Dentistry Department of Orthodontics found 42 to 62% of prescribed OTM achieved.56-58 These studies found that the majority of OTM occurs in the first week of wear when changing aligners every other week,58 that material fatigue was not a factor in OTM using Invisalign® aligners,56 and that gender and age might play a role in amount of OTM.59 From these studies it can be concluded that factors affecting the amount of OTM achieved using Invisalign® clear aligner orthodontic therapy may include sex, age, the amount of prescribed movement (0.25 to 0.5mm per aligner), frequency of changing the aligner, and the plastic material used to fabricate the trays.
General dentists using Invisalign® and other clear aligner systems should be sure to stay current with evolving technology and evidence based literature regarding the treatment they are providing patients. It is important to critically assess treatment that is initially generated by technicians as they are often based on generic algorithms. Every patient is unique, and their treatment needs and possibilities should also be considered as such. In addition, the limitations of aligner therapy should be understood and considered.