For clear understanding of thermoformed aligner orthodontics, two fundamental differences between bracket-based and aligner-based biomechanics must be recognized:

In conventional orthodontic tooth movement, a force is applied to the bracket, which transmits this force to tooth structures, generating the mechanical-biological chain of events that results in displacement of the tooth.
In aligner-based tooth movement, an intentional, predetermined “mismatch” between the aligner and the tooth is programmed in each treatment stage, using a cast or virtual model set-up (alignment). The aligner, which corresponds to the new desired tooth position, is fitted on the dental arch, producing in each mismatch a force system that is directly transmitted to the tooth, generating a similar chain of events that results in a new position of the teeth.
Although aligner-based rotation and torque movement have been explored, neither the mechanics of bodily tooth movement nor the role of the biomechanically enhancing composite attachments has been considered.

http://www.angle.org/doi/full/10.2319/050714-330.1?code=angf...

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Note added at 27 mins (2018-06-18 11:17:33 GMT)
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Apt => Adaptation???

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Note added at 28 mins (2018-06-18 11:19:15 GMT)
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QUINTESSENCE catalogue 2018 - Quintessence Publishing
www.quintpub.co.uk/index.php?modules=default&op=sendpdf&fil...
Diagnosis and Communication • Tooth Preparation • Composite Resins • Ceramic ...... Digital Radiology • Virtual Diagnosis and Treatment Planning • Computer-Assisted ...... Clear aligners are the future of orthodontics, ...... sitivity; enhancing internal adaptation; immediate dentin sealing;

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Note added at 31 mins (2018-06-18 11:21:56 GMT)
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Finite element method analysis of the... (PDF Download Available)
https://www.researchgate.net/.../281541111_Finite_element_me...
Sep 9, 2015 - 1 Finite element model of mandibular tissue, Aligner (a), Dentition (b), periodontal ligament (c), mandible .... adapt to the tooth deformation and the surrounding struc- .... shows the ability to adapt to a change in external loads,.


I am tentative but adaptation seem ok because in initial phase Apt (Up to 7 Aligners) seems reasonable

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Note added at 35 mins (2018-06-18 11:25:56 GMT)
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Apt | Define Apt at Dictionary.com
www.dictionary.com/browse/apt
Apt definition, inclined; disposed; given; prone: too apt to slander others. ... abbreviation for plural apts. ... mid-14c., "inclined, disposed;" late 14c., "suited, fitted, adapted," from Old French ate (13c., Modern French apte), or directly from Latin ...

apt - WordReference.com Dictionary of English
www.wordreference.com/definition/apt
apt - WordReference English dictionary, questions, discussion and forums. All Free. ... This meaning is found in such words as: adapt, apt, aptitude, inept.

конфигурация дефекта позволяет использовать небольшое число итераций
http://www.clearbraceprovider.co.uk/service/invisalign-i7/
The Invisalign i7 is limited to only 7 aligners that can be manufactured to make the planned corrections. The Invisalign i7 can only move the anterior teeth. For these reasons it is used to treat mild cases.
https://ortodont-msk.ru/vidy-elajnerov-dlya-ispravleniya-pri...
В зависимости от степени сложности ортодонтического лечения возможно использовать четыре варианта лечения элайнерами INVISALIGN:
1) INVISALIGN Full (полный метод более 14 элайнеров)
2) INVISALIGN Lite (экспресс метод менее 14 элайнеров)
3) INVISALIGN Teen (элайнеры имеют специальную маркировку, показывающую, сколько времени носит капы пациент, преимущественно используется для подростков)
4) INVISALIGN 7 (Краткий метод до 7 элайнеров, для исправления положения отдельных зубов)