Comparative Analysis of Model Resin and Orthodontic Resins: Accuracy and Dimensional Stability of 3D Printed Models for Clear Aligners and Removable Appliances

Background: The accuracy and structural integrity of 3D-printed resin models are ultimate determinants of the quality and fit of orthodontic appliances, and therefore directly impact clinical treatment outcomes. Since there is a wide variety of photopolymer resins available in the market, each with different chemical composition, mechanical properties, and clinical indications, it is essential to evaluate their behavior for proper selection of the appropriate resin for each clinical application. (2) Objectives: The present study aimed at evaluating the initial printing accuracy directly after printing , thermo-mechanical dimensional stability after clear aligner thermoforming and PMMA cold-cure acrylic appliance fabrication of two commercially available 3D printing resins (KeyModel Ultra and KeyOrtho Model).(3) Methods: Forty standardized master dental models (N=40 ) were 3D printed and assigned to two main groups (n = 20) based on the resin material. Initial printing accuracy was quantified by calculating the Root Mean Square (RMS) deviation between the printed models against the master digital reference file, and each group was then further divided into two subgroups (n = 10), subjected to clear aligner thermoforming and to PMMA appliance fabrication. Post-procedure scans were superimposed onto the corresponding pre-procedure model scans to evaluate the dimensional stability after undergoing laboratory procedures. (4) Results: KeyModel Ultra showed RMS deviation of 0.209 ± 0.033 mm against the master digital reference file, while KeyOrtho Model showed a significantly lower mean RMS deviation of 0.161 ± 0.042 mm (p = 0.011). Following laboratory fabrication procedures, KeyOrtho Model demonstrated no statistically significant dimensional change after clear aligner thermoforming (p = 0.160) or PMMA cold-cure appliance fabrication (p = 0.780), whereas KeyModel Ultra showed statistically significant structural change under both conditions (p = 0.004). 5) Conclusion: KeyOrtho Model demonstrated better initial accuracy and greater dimensional stability than KeyModel Ultra under the tested laboratory conditions.