Related Experiment Video
Updated: Dec 8, 2025
Author Spotlight: 3D Movement Assessment of Maxillary Posterior Teeth in Clear Aligner Treatment
Published on: February 23, 2024
Evaluation of effectiveness and stability of aligner treatments using the Peer Assessment Rating Index
Isabelle Graf1, Carolin Puppe2, Jörg Schwarze3
1Department of Orthodontics, Faculty of Medicine and University Hospital of Cologne, University of Cologne, Kerpener Str. 32, 50931, Cologne, Germany. isabelle.graf@uk-koeln.de.
Aims:
The aims of this study were to measure treatment effects of aligner treatments in adult patients directly after treatment and the stability of these effects after a short-term retention period using the Peer Assessment Rating (PAR) Index.
Methods:
This double-center trial consecutively screened 98 adult patients of whom 33 patients were treated according to predefined inclusion and exclusion criteria. The study sample was shown to be representative for adult orthodontic reality with regard to gender, age, and distribution of malocclusion type. Malocclusion severity was rated by using the PAR Index measured at baseline (T0), after finishing orthodontic treatment with Invisalign® (T1; Align Technology Inc., Santa Clara, CA, USA) and after a mean retention period of 10 months (T2). Furthermore, to better understand the observed treatment modality, specific treatment characteristics were recorded and analyzed.
Results:
The average PAR score at T0 was 22.18 (standard deviation [SD] ± 8.68). Posttreatment PAR score was 4.64 (SD ± 4.23) at T1 and was stable after a retention period of 10.07 months at T2 (SD ± 126.80 days; PAR 4.36, SD ± 3.93). All of the study cases showed a significant reduction of the total PAR score between T0 and T1 (p < 0.001), but no further difference between T1 and T2 (PAR 4.64 vs. 4.36). Cases were either classified 'improved' (n = 23) or 'greatly improved' (n = 10); no case was classified into the third PAR Index category 'worse or no different'. On average, 72 aligners (SD ± 22) with 12 attachments per treatment (SD ± 4) were used to align teeth. Six patients needed a case refinement with a mean of 23 (SD ± 8) further aligners. The maximum number of needed ClinCheck® (Align Technology Inc., Santa Clara, CA, USA) treatment plan revisions was 18 (mean 7, SD ± 4).
Conclusion:
The detected improvement rate indicated a good standard of orthodontic treatment using aligners. Treatment effects were stable throughout a short-term retention period using a specific retention protocol. Effectiveness and stability were equally achieved in mild, moderate, and rather severe cases within this consecutive sample. A critical focus should be placed on accurate treatment planning in order to make tooth movements predictable, realistic, and stable.
