The January 2009 American Journal of Orthodontics features a study relating to the efficiency of Invisalign therapy by Kravitz and his colleagues at the University of Illinois Dental School . The study compares actual achieved results on 37 Invisalign patients with expected results as extrapolated from the final aligner. The mean accuracy was 41% overall. The best accuracy for rotational corrections was 54% dropping to about 30% for cuspids with greater than 15 degrees rotation. Related parameters of tooth movement such as extrusion, intrusion and tipping are similarly unimpressive. This technique has been used on some 300,000 patients over the last ten years. Align Technology itself reports that 20-30% of patients require “midcourse correction” to achieve pretreatment goals while in two other studies orthodontists report 70-80% of patients require such “midcourse correction”, case refinement or conversion to fixed appliances in order to satisfactorily complete cases.
These results raise several issues relating to intelligent and evidence based adaptation and integration of new technology into our practices. From any perspective, its troubling when a technique of this type with issues widely known to many of us for years is pushed to the public and the profession without the accompanying research foundation necessary, in my opinion, to validate its widespread use.
At Ziman Orthodontics, we view one of our responsibilities as being able to sort out new technology for our patients based on our almost 26 years of clinical experience and knowledge of the research. In many instances, the public is not equipped to make such an evaluation and looks to the profession for guidance. That its taken this long for a study of this type to be published does not in my opinion speak well of my specialty. Ziman Orthodontics has NOT been a proponent of this technique in the past and its fair to say that defending a 41% accuracy rate would not be our preference in any circumstance.
The measuring stick we use when integrating new technology/ materials into our practice is straightforward: Research needs to demonstrate that the new technique/ material is objectively superior to what we are currently doing/ using AND that it represents a better value for our patients. ( as distinct from a lower cost which may or may not correlate with value) We’ve integrated many new materials and techniques into our practice over the past 26 years ranging from better adhesives to headgear alternatives and advanced wire alloys. We are open to new ideas when they bring something better to the table that we can validate.