Invisalign Expansion Falls Short Of Digital Treatment Plans In New Study

Invisalign expansion accuracy fell short of the digital plan in a new study of 25 patients. Teeth reached 80% to 91% of the arch expansion their ClinCheck setups predicted. Tooth length and crown-to-root ratio did not explain the shortfall, which points to other causes.

TL;DR

• Invisalign patients achieved 80.03% to 91.08% of planned expansion in every measured region.

• Tooth length and crown-to-root ratio did not predict how much expansion was achieved.

• The study measured crowns, so root movement likely lagged further behind the plan.

What Did The New Invisalign Study Investigate?

Saniye Merve Cengiz of the Department of Orthodontics at Mersin University in Turkey ran the study. It appeared in Scientific Reports on November 12, 2026, with no external funding.

The research was a retrospective review of 25 patients treated with Invisalign. Every patient had transverse expansion planned in both arches. It compared planned with achieved movement and tested whether two features of posterior tooth shape explained the difference. It was observational and compared no other treatment.

How Much Of The Planned Invisalign Expansion Was Achieved?

Achieved expansion was significantly lower than planned in every dental region measured (P < 0.05). Expansion efficiency ranged from 80.03% to 91.08%.

What Does 80–91% Expansion Efficiency Mean?

Efficiency is the measured expansion divided by the planned expansion. As an illustration, a planned 2 mm widening at 80% efficiency would give 1.6 mm. That figure is an example, not a measurement from the study.

The 80–91% range describes crown positions only. Aligners mostly widen arches by tipping crowns outward. A systematic review of Invisalign expansion found lower predictability at the gumline than at the cusp tips. Roots likely moved even less than these crown-level figures suggest.

Does Lower Expansion Efficiency Mean Treatment Failed?

No. A tooth that stops short of the digital plan can still reach an acceptable bite. The study did not measure patient satisfaction, overall treatment goals, or Invisalign success rates. A shortfall of 10–20% is also not always a problem. Pushing posterior crowns to full planned width can tip them too far, especially in adults with thin bone.

How Did Researchers Compare ClinCheck Predictions With Actual Tooth Movement?

The study combined three data sources.

• Planned expansion came from each patient's ClinCheck digital setup

• Achieved expansion came from pre- and post-treatment digital models

• OrthoAnalyzer software measured arch width changes on those models

• Posterior tooth length and crown-to-root ratio came from panoramic radiographs analyzed in ImageJ

Digital models make planned and achieved positions easy to compare when scans are accurate. Our guide to Invisalign-compatible scanners covers that part of the workflow.

Did Tooth Length Or Crown-To-Root Ratio Affect Expansion Accuracy?

Neither measure showed a significant link with expansion efficiency (P > 0.05). Correlation tests and multivariable models gave the same answer.

Total tooth length covers crown and root together. Crown-to-root ratio compares the visible crown with the root in bone. Longer roots, in theory, might resist tipping.

The choice of image may explain part of the null result. Panoramic radiographs distort posterior teeth, stretching some and shortening others depending on head position. Small differences in root length can vanish in that noise, and cone-beam CT would measure them better. The result shows these two panoramic measures were poor predictors in this sample. It does not show that root anatomy is irrelevant to aligner treatment.

Why Might Invisalign Expansion Differ From The Digital Plan?

A ClinCheck setup shows where the teeth should end up. It does not model bone, gum tissue, or how much an aligner flexes under load.

Aligners push on crowns, so they tip teeth more readily than they move them bodily. Force also drops as the plastic relaxes. A tooth against a thin outer bone plate has less room than the software assumes. The study did not test which factor caused the shortfall. It also gave no evidence of poor aligner wear. Aligner fit is a separate issue, covered in our guide to Invisalign chewies.

How Do These Results Compare With Previous Invisalign Research?

The new figures sit at the upper end of earlier research. The systematic review pooled 23 studies and 1,391 patients. Predictability averaged 75.5% in the upper arch and 80.6% in the lower arch. Lower second premolars scored highest at 88%, while lower second molars were least reliable at 73%. Younger age and SmartTrack aligner material predicted better results. The reviewers rated the overall certainty of evidence as very low.

A 61-patient study found 86% predictability for expansion and only 29.5% for extrusion. Different populations and measurement methods prevent direct comparison between studies.

What Could The Findings Mean For Orthodontists?

A ClinCheck setup is a target, and the new data support treating it that way. Comparing a mid-treatment scan against the setup shows early whether expansion is tracking. Checking the gingival level as well as the cusp tips reveals how much of the change is tipping. A baseline assessment of buccal bone and gum thickness helps set a safe limit before planning large expansion. Excessive tipping can lead to gum recession, which is harder to fix than a refinement.

These checks belong in a structured dental treatment plan, along with expected refinements. The study offers no basis for a specific overcorrection percentage. Our coverage of Invisalign digital treatment planning explains new ClinCheck tools and the Palatal Expander, a separate appliance for skeletal expansion in growing patients.

“Patients see the ClinCheck animation and expect the teeth to follow it exactly,” says dentist Darius Kucinas. “It is closer to a forecast. Molars that fall a little short of planned width are often safer than molars tipped out of their bone.”

What Are The Study's Limitations?

Several features limit how widely the results apply.

• The sample included only 25 patients

• The design was retrospective

• Only Invisalign transverse dental expansion was assessed

• Measurements were at crown level, without three-dimensional root or skeletal assessment

• Panoramic radiographs distort posterior tooth dimensions

• Only two tooth morphology predictors were tested

• Results may not apply to other aligner systems or other movements

• The study did not test any method for improving expansion accuracy

Bottom Line

Invisalign achieved about 80–91% of planned transverse expansion in this 25-patient study. Posterior tooth length and crown-to-root ratio did not predict the shortfall. ClinCheck setups work best as targets that need monitoring. Because the study measured crowns, the real root movement was likely smaller still. Measuring progress at both cusp and gumline levels gives a truer picture than the animation.