A recent article from the American Journal of Orthodontics and Dentofacial Orthopedics reported on a retrospective clinical study from two orthodontic practices which evaluated the following:
- The percentage of patients that switched from Invisalign to fixed braces to finish treatment,
- The number of refinement scans, and
- Estimated vs actual length of treatment.
The study involved 500 patients with the average age of 33.6 years. The results were as follows:
- 17.2% (one out of six patients) switched from Invisalign to fixed braces to finish treatment.
- An average of 2.5 refinement scans were required for the Invisalign cases.
- 6.0% of patients completed Invisalign treatment with no refinement scan.
- 22.8 months was the average length of Invisalign treatment.
- Actual Invisalign treatment was 5.1 months more than the estimated treatment time.
- 64.1 was the average number of aligners
- 80.6 was the average number of aligners for those that switched to fixed braces.
- 6.9 months was the average additional treatment for those that switched to fixed braces.
- The older age group had significantly greater number of refinement scans.
The authors concluded that the orthodontists are overestimating the efficiency of using Invisalign and underestimating the length of treatment. Patients need to be informed of the reasonable expectation that braces may be needed. 
