Recommendations for clear aligner therapy using digital or plaster study casts

Clear aligner therapy has evolved considerably since its introduction 20 years ago. Clinicians have become more experienced with aligner therapy, but little is known about the types of malocclusions that clinicians currently treat with aligners. Similarly, it is not known if viewing digital vs plaster models has any impact on the treatment planning process for aligners. The aim of this study was to assess which types of malocclusions are recommended for treatment with clear aligners, and also to determine if recommendations for aligner treatment differed when using digital versus plaster models.

Sixteen orthodontists treatment planned 20 cases at two time points with either the same or different model formats (digital versus plaster). As part of the treatment planning process, they were asked whether each patient was a good candidate for Invisalign® treatment, and if not, why. Generalized estimating equations regression (GEE), the permutation test, and a logistic regression model with GEE were used to analyze the data.

No significant difference was found between the Invisalign® choices in the digital model group and those in the plaster model group at T1 (p = 0.59). There was no significant difference between the agreement rate of the different formats group and that of the same format group (p = 0.97). Cases with extractions had less Invisalign® recommendations (15%) compared to cases with no extractions (55%) (p = 0.0015). Cases with surgery had less Invisalign® recommendations (29%) compared to cases with no surgery (57%) (p = 0.035).

In this study, viewing orthodontic records with digital versus plaster models did not influence decisions about Invisalign® recommendations. Additionally, the orthodontists in this study tended to not recommend Invisalign® for extraction cases, surgical cases, or difficult cases.