As part of my professional life, I decided to keep a foot in the academic life dedicating this quality time to research. I am currently working in University of Geneva, with Prof. Kiliaridis, one day per week and running research projects with many Italian universities.
My research interest is 3D imaging & to check for effectiveness of treatment regimens. I would like to share into details a paper that was recently published into Progress in Orthodontics (online early) that was born from a collaboration with a young team of the University of Ferrara lead by the brilliant Dr Luca Lombardo.
Predictability of orthodontic movement with orthodontic aligners: a retrospective study.
Lombardo L, Arreghini A, Ramina F, Huanca Ghislanzoni LT, Siciliani G.
Prog Orthod. 2017 Nov 13;18(1):35. doi: 10.1186/s40510-017-0190-0.
What did we do?
The university of Ferrara developed a specific aligner product (F22 Aligners, changes every 2 weeks) and we tested for effectiveness of guiding teeth into the positions planned using digital orthodontic setup.
Quite a bunch of studies were performed in the past but each of them analyzed a special aspect (eg. expansion, extrusion, tipping of one tooth, space closure). In this study tip, torque and rotations were analyzed with digital coordinates system that give values like the ones that we are used to read on bracket prescriptions.
Example of torque measurements
16 patients and à total of 345 teeth were analyzed by having digital impression of the initial pretreatment, the real posttreatment and the ideal posttreatment (setup).
What did we find?
The overall accuracy or predictability of all the tooth movements was 74%
which is a higher value with regard to previous studies with Invisalign therapy with old materials (scores ranging 41-56%) and very similar with Invisalign with SmartTrack elastic material (73%, as reported by Prof. Wheeler* in a recent paper on the first edition of the brand-new Journal of Aligner Orthodontics).
Details of accuracy of single movements can be easily understood with this picture (taken from the article)
What do I think?
This study has many limitations, first of all the number of patients and the initial malocclusion (it can be referred to malocclusions having max 5mm of crowding per arch). It analyzed a sample very similar to what could have been an Invisalign Lite treated sample.
It’s very interesting that we cannot expect 100% of results with a combination of a good setup and a good set of aligners.
What explains that 25% of missing correction?
Is it biology? Wrong biomechanical choice? Difficult if not impossible to say.
It’s already good to be aware of this phenomenon and to know that to reach the ideal results it’s a matter of patience and multiple attempts. We can figure out that on each attempt, on average, we get rid of 75% of the malocclusion (with F22 aligners and with Invisalign with SmartTrack).
And what about the second set of aligners? Will it solve the remaining 25% of the malocclusion or it will solve a 18% (75% of the 25%) of it leaving the need of a third refinement. This can get easily into a mathematic delirium similar to the Zeno’s paradox of Achille and the tortoise =)
Maybe by starting from much closer to the final goal, the performance is better in the second set of aligners. But this has to be proven =)
Is it a drama? Not at all, as well as we spend some time into the finishing phase with braces, we should plan to spend quite a bunch of time into refinement with aligners.
We just clearly tell your patient that the first set of aligners will never be enough. Do not let them think that you’re not good orthodontists!
* Prof. Timothy Wheeler is a true Authority in the field of aligners studies. Stay tuned for the second part of this literature update as some spicy information is coming the next week!
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