October 13, 2025

Expert Consensus on Clear Aligners Efficacy: A Delphi Study Review

A few weeks ago, I posted about an interesting study in which a team reached a consensus on the usefulness of clear aligners. They used a Delphi process to achieve this agreement. Their most important finding was that clear aligners served as an effective alternative to traditional fixed appliances in class I patients with mild to moderate crowding. 

This study method is novel in orthodontic research and has provided us with valuable information about aligner treatment; however, it is based on a low level of evidence. I then discovered another research team conducting a nearly identical project. I have decided to review this paper so that we can see whether the team reached a similar consensus.

A team from Ferrara, Italy, led this research. The AJO-DDO published their paper.

What did they ask?

They wanted to 

“reach a consensus on specific controversial concerning clear aligner treatment and secondly to verify whether the clinical experience of the experts coincided with the available scientific evidence”.

What did they do?

They conducted a Delphi study led by a team of expert researchers from several Italian Universities.  The team employed a standard Delphi methodology, comprising the following stages.

  • Establishment of a study steering committee.
  • This group then identified the current evidence concerning a treatment from systematic reviews.
  • Then they defined important topics.
  • Constructed a series of statements on these topics.
  • Next, they identified a larger group of experts to form a study panel.
  • They then circulated the statements to the panel and asked them to rate their level of agreement or disagreement with each statement.
  • If there was no “agreement”, they circulated the statements to the panel again with the overall scores that were given. The panel then rescored. They continued this process for another session until they reached an agreement/or didn’t agree on the statements.

To be a member of the study panel, members had to meet at least one of the following inclusion criteria.

  • Be a member of the ABO, EBO, Italian Board of Orthodontics, Italian Board of Orthodontics Aligner or European Board of Aligner Orthodontic Boards. (I didn’t realise there were so many Boards…)
  • Have published more than five research papers on aligners in accredited journals.
  • More than fifteen years of internationally recognised expertise in the field of aligners.
What did they find?

The team enrolled 36 experts on the panel. Six dropped out during the study, leaving a final sample of 30. They needed three rounds to develop a total of 47 consensus statements.

They presented these in a clear table. The publication is open access so that you can view this table. I do not have enough space in this post to discuss all the statements. However, these were the most interesting and clinically relevant.

  • Aligners can achieve tipping movement.
  • We are not able to distalise maxillary or mandibular molars by more than 2.75mm.
  • Aligners are unable to achieve bodily mesialisation of the ore than 2.75mm.
  • Aligners are not effective for bodily intrusion movements exceeding 1.5 mm.
  • We can obtain less than 10 degrees of rotation with aligners.
  • The use of attachments is moderate or very effective.
  • Only 50% of the experts considered aligners to be highly effective in resolving transverse discrepancies.
  • A consensus of 70% was reached that aligners are minimally effective in 4 premolar extraction cases.
  • In the mixed dentition, skeletal expansion should be achieved using more effective conventional appliances.
  • 38% of the panel used aligners for class II correction

These findings are very similar to the other Delphi study.

Their overall conclusion was unclear. However, in the final part of their discussion, they stated 

“Most dentoalveolar malocclusions are resolved thanks to uncontrolled tipping movements in which the effectiveness of the aligners remains consistently high”.

What did I think?

This study closely resembles the previous aligner, Delphi, that I discussed. As a result, my comments are similar! The team followed a standard process and reached consensus in three stages. This is typical of other studies of this nature.  

It should come as no surprise to anyone reading this post to find that I identified similar concerns in this study. The first of these is the identification of the expert panel. However, they provided more detail on the criteria they used to select the experts. I was also interested to see that there was limited overlap between the membership of the two panels. Aside from any issues with the panel selection, the two studies gathered opinions from 54 aligner experts. This is a considerable body of opinion. 

I was concerned that the panel in the most recent paper did include some KOLs who did not declare a conflict.

Furthermore, upon examining the studies that underpinned the research, I discovered that most systematic reviews included retrospective studies. As a result, they were based on a low level of evidence.

Final comments.

Again, I do not want to be too critical because this was a complex study to conduct. The authors conducted this study effectively.

However, we must remember that the consensus represents the best evidence available when high-quality research is lacking. Importantly, panel opinion based on retrospective studies and clinical experience is regarded as of low value. However, we now have “expert” opinion from a panel of 54.

Finally, I am concerned that the Delphi consensus study will become the systematic review of the past 15 years. I really do not want to read any more publications that suggest “more randomised trials are needed”……I want someone to do the trial….

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