Predictability of expansion with clear aligners

Morales-Burruezo et al. 2020 set out to answer:

• The efficacy of arch expansion with Invisalign(tm) system (how many mm can we expand?)

• How predictable is the outcome after the first set? (for the amount of expansion we want, how many mm do we actually achieve?)

114 Adult patients were selected between ages 18-75

Utilising grid tool, keynote and RulerSwift measurements were carried out:

T1: Start of treatment

T2: Clincheck's predicted movement

T3: Actual measurements at the start of second phase

What did they find?

Different locations = different amount of expansion produced

First and second premolars typically expanded the most (avg 3.14-3.45mm)

Canine expansion (avg 1.87mm)

First molar expansion (avg 2.57mm)

How predictable was the expansion?

eg. if the patient had 30 aligners, at completion of these 30 aligners how different was this in comparison to the final computer simulation?

See table on post 5.

What would be the recommendation?

Based on the predictability with these results the author recommends to overcorrect the expansion amount during virtual planning stage to achieve desired final outcomes. 

Further studies are needed to assess the use of intermaxillary elastics and presence/abscence of attachments

Other literature

Similar amount of predictability of premolars and molars, canine expansion 88.7% vs 74.8%

Similar amount of predictability except molars however mandibular arch was more predictable than maxillary arch expansion