Related Experiment Video
Updated: Feb 8, 2026

Accuracy in Dental Medicine, A New Way to Measure Trueness and Precision
Published on: April 29, 2014
Trueness and precision of direct-printed and thermoformed clear aligners after artificial saliva exposure: A
Claire-Adeline Dantagnan1, Clara Salem2, Carole Charavet3
1UMR 1333 Oral Health Laboratory, National Institute of Health and Medical Research (Institut national de la santé et de la recherche médicale), Paris City University, Sorbonne University Paris North, Montrouge, France; Orthodontic Department, Paris City University, Montrouge, France; Pitié-Salpêtrière Hospital, boulevard de l'Hôpital, Paris, France.
Introduction:
This study aimed to compare the effect of artificial saliva (AS) aging on the trueness and precision of direct-printed aligners vs thermoformed aligners.
Methods:
Four types of aligners were manufactured from the same reference standard tessellation language (STL) file: using Duran Plus (n = 12) for thermoformed ones, and TC-85DAC (n = 12), Clear A (n = 12), or OD Clear TF (OC, n = 12) resins for direct-printed ones. A printed model was used for thermoformed aligners, whereas digital design models were generated for direct-printed aligners from the reference STL file. The samples were sprayed and scanned (Trios 3; 3 Shape, Copenhagen, Denmark) before and after aging in AS at 37°C for 24 hours, 7 days, and 14 days. STL files were imported into CloudCompare software (CloudCompare, 2.13.2 version, Paris, France) and superimposed on the design or digital model (trueness) or to each other within each group (precision) using a 7 reference-point algorithm. Two-way analysis of variance was performed to evaluate the influence of saliva aging and material type.
Results:
A significant effect of the material type was observed with a lower trueness and precision for Duran Plus aligners compared with the 3 groups of direct-printed aligners. A significant effect of AS aging, with a decrease of trueness and precision, was also noted for both thermoformed and printed aligners.
Conclusions:
This in vitro study demonstrated that direct-printed aligners provided higher trueness and precision than thermoformed ones. Exposure to AS decreased the trueness and precision for both types. However, further studies are needed to validate the behaviors of direct-printed aligners clinically.
Related Concept Videos
Salivary Glands and Saliva
Uncertainty in Measurement: Accuracy and Precision
Comparative Excretory Systems
Design Example: Alignment of a Road Line Using GIS
Comparing Copy Number Variations and SNPs
Copy number variations or CNVs are the structural variations that cover more than 1kb of DNA sequence. The single nucleotide polymorphism (SNP), on the other hand, is a single nucleotide change or a point mutation that is found in more than 1%...
Accuracy and Precision

