{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,8,18]],"date-time":"2026-08-18T05:03:50Z","timestamp":1787029430860,"version":"build-2736575974"},"reference-count":43,"publisher":"MDPI AG","issue":"8","license":[{"start":{"date-parts":[[2026,4,21]],"date-time":"2026-04-21T00:00:00Z","timestamp":1776729600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100000780","name":"European Union","doi-asserted-by":"crossref","id":[{"id":"10.13039\/501100000780","id-type":"DOI","asserted-by":"crossref"}]},{"name":"National Recovery and Resilience Plan","award":["SFZG-11-2025_NAT-DM"],"award-info":[{"award-number":["SFZG-11-2025_NAT-DM"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Polymers"],"abstract":"<jats:p>The clinical effectiveness of clear orthodontic aligners mainly depends on the thermomechanical stability of the polymers in this challenging hydrothermal environment. In this study, we compare the water-induced viscoelastic changes and glass transition temperature (Tg) stability of four polymers with different microarchitectures. Specifically, we examined directly printed photopolymer networks (Tera Harz TC-85 and LuxCreo 4D Aligner), a monolithic thermoplastic (Duran+), and a multilayer thermoplastic (ClearCorrect). Samples were immersed in physiological saline (0.9 wt.% NaCl) at 37 \u00b0C for 7 days, and Dynamic Mechanical Analysis (DMA) was performed in three conditions: dry, after immersion, and after a 2 h desorption step, mimicking a typical clinical 22:2 wear cycle. All polymers showed a decrease in Tg after immersion, with TC-85 exhibiting the greatest reduction relative to the dry baseline. Tg recovery after a 2 h ambient desorption step was incomplete and was significantly associated with the amount of water retained after 2 h drying (expressed as % of initial uptake; R2 = 0.419), whereas total water absorption after 7 days was not associated with short-term thermal recovery.<\/jats:p>","DOI":"10.3390\/polym18081008","type":"journal-article","created":{"date-parts":[[2026,4,21]],"date-time":"2026-04-21T16:10:44Z","timestamp":1776787844000},"page":"1008","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":1,"title":["Water Desorption Governs Glass Transition Recovery in Aligner Polymers"],"prefix":"10.3390","volume":"18","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-2848-6041","authenticated-orcid":false,"given":"Luka","family":"\u0160imunovi\u0107","sequence":"first","affiliation":[{"name":"Department of Orthodontics, School of Dental Medicine, University of Zagreb, 10000 Zagreb, Croatia"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0007-2685-6201","authenticated-orcid":false,"given":"Luka","family":"Brenko","sequence":"additional","affiliation":[{"name":"Department of Materials, Faculty of Mechanical Engineering and Naval Architecture, University of Zagreb, 10000 Zagreb, Croatia"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Ana Marija","family":"Mili\u010devi\u0107","sequence":"additional","affiliation":[{"name":"Department of Orthodontics, School of Dental Medicine, University of Zagreb, 10000 Zagreb, Croatia"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-5327-4329","authenticated-orcid":false,"given":"Tatjana","family":"Haramina","sequence":"additional","affiliation":[{"name":"Department of Materials, Faculty of Mechanical Engineering and Naval Architecture, University of Zagreb, 10000 Zagreb, Croatia"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-3224-3579","authenticated-orcid":false,"given":"Senka","family":"Me\u0161trovi\u0107","sequence":"additional","affiliation":[{"name":"Department of Orthodontics, School of Dental Medicine, University of Zagreb, 10000 Zagreb, Croatia"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2026,4,21]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","unstructured":"Narongdej, P., Hassanpour, M., Alterman, N., Rawlins-Buchanan, F., and Barjasteh, E. (2024). Advancements in Clear Aligner Fabrication: A Comprehensive Review of Direct-3D Printing Technologies. Polymers, 16.","DOI":"10.3390\/polym16030371"},{"key":"ref_2","doi-asserted-by":"crossref","unstructured":"Staderini, E., Chiusolo, G., Papi, M., Palone, M., Lombardo, L., and Cordaro, M. (2025). Chemical, Optical, and Morphological Properties of TPU and PET-G Samples after Aging in Artificial Saliva: An In Vitro Study. BMC Oral Health, 25.","DOI":"10.1186\/s12903-025-05863-0"},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"241","DOI":"10.5152\/TurkJOrthod.2019.18083","article-title":"Orthodontic Treatment with Clear Aligners and the Scientific Reality behind Their Marketing: A Literature Review","volume":"32","author":"Tamer","year":"2019","journal-title":"Turk. J. Orthod."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"37","DOI":"10.4103\/jos.jos_30_23","article-title":"Clear Aligner Therapy: Up to Date Review Article","volume":"12","author":"AlMogbel","year":"2023","journal-title":"J. Orthod. Sci."},{"key":"ref_5","doi-asserted-by":"crossref","unstructured":"Macr\u00ec, M., Murmura, G., Varvara, G., Traini, T., and Festa, F. (2022). Clinical Performances and Biological Features of Clear Aligners Materials in Orthodontics. Front. Mater., 9.","DOI":"10.3389\/fmats.2022.819121"},{"key":"ref_6","first-page":"381","article-title":"Comparison of Three Dental Resins for 3D Printing of Orthodontic Appliances: Comparison of Leaching, Biocompatibility, and Thermo-Mechanical Properties after Post-Curing and Aging","volume":"42","author":"Saunier","year":"2025","journal-title":"Dent. Mater."},{"key":"ref_7","first-page":"384","article-title":"Advances in Orthodontic Clear Aligner Materials","volume":"22","author":"Bichu","year":"2023","journal-title":"Bioact. Mater."},{"key":"ref_8","doi-asserted-by":"crossref","unstructured":"Shaukat, U., Rossegger, E., and Schl\u00f6gl, S. (2022). A Review of Multi-Material 3D Printing of Functional Materials via Vat Photopolymerization. Polymers, 14.","DOI":"10.3390\/polym14122449"},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"815","DOI":"10.1039\/D3PY01367G","article-title":"A Tutorial Review of Linear Rheology for Polymer Chemists: Basics and Best Practices for Covalent Adaptable Networks","volume":"15","author":"Ricarte","year":"2024","journal-title":"Polym. Chem."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"7244","DOI":"10.1038\/s41467-023-43073-w","article-title":"Polymer Architecture Dictates Multiple Relaxation Processes in Soft Networks with Two Orthogonal Dynamic Bonds","volume":"14","author":"Ge","year":"2023","journal-title":"Nat. Commun."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"640","DOI":"10.1016\/j.ajodo.2025.11.021","article-title":"Trueness and Precision of Direct-Printed and Thermoformed Clear Aligners after Artificial Saliva Exposure: A Comparative in Vitro Study","volume":"169","author":"Dantagnan","year":"2026","journal-title":"Am. J. Orthod. Dentofac. Orthop."},{"key":"ref_12","doi-asserted-by":"crossref","unstructured":"Delgado, J.I., Kehyaian, P., and Fern\u00e1ndez-Bl\u00e1zquez, J.P. (2025). Thermoplastics for Clear Aligners: A Review. Polymers, 17.","DOI":"10.3390\/polym17121681"},{"key":"ref_13","doi-asserted-by":"crossref","unstructured":"Iftekar, S.F., Aabid, A., Amir, A., and Baig, M. (2023). Advancements and Limitations in 3D Printing Materials and Technologies: A Critical Review. Polymers, 15.","DOI":"10.3390\/polym15112519"},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"380","DOI":"10.4041\/kjod25.094","article-title":"Comparative Mechanical Performance of Thermoplastic Materials for Clear Aligners under Simulated Oral Conditions","volume":"55","author":"Liu","year":"2025","journal-title":"Korean J. Orthod."},{"key":"ref_15","unstructured":"Lucia, P., Valentina, B., Beatrice, G., Jacopo, M., Tihana, Z.B., Gianluca, T., Davide, P., and Luca, C. (2025). Mechanical Properties of Thermoplastic Materials for Clear Orthodontic Aligners: A New Three-Dimensional Experimental Setting. Orthod. Craniofac. Res., early view."},{"key":"ref_16","doi-asserted-by":"crossref","unstructured":"Staderini, E., Chiusolo, G., Guglielmi, F., Papi, M., Perini, G., Tepedino, M., and Gallenzi, P. (2024). Effects of Thermoforming on the Mechanical, Optical, Chemical, and Morphological Properties of PET-G: In Vitro Study. Polymers, 16.","DOI":"10.3390\/polym16020203"},{"key":"ref_17","doi-asserted-by":"crossref","unstructured":"Cenzato, N., Di Iasio, G., Mart\u00ecn Carreras-Presas, C., Caprioglio, A., and Del Fabbro, M. (2024). Materials for Clear Aligners\u2014A Comprehensive Exploration of Characteristics and Innovations: A Scoping Review. Appl. Sci., 14.","DOI":"10.3390\/app14156533"},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"19022","DOI":"10.1038\/s41598-025-04096-z","article-title":"Impact of Various Cleaning Protocols on the Physical and Aesthetic Properties of 3D-Printed Orthodontic Aligners","volume":"15","author":"Haramina","year":"2025","journal-title":"Sci. Rep."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"101","DOI":"10.21278\/TOF.482043222","article-title":"Design and Production of the Splint Using Reverse Engineering and Additive Manufacturing","volume":"48","author":"Grabar","year":"2024","journal-title":"Trans. FAMENA"},{"key":"ref_20","doi-asserted-by":"crossref","unstructured":"Hassanpour, M., Narongdej, P., Alterman, N., Moghtadernejad, S., and Barjasteh, E. (2024). Effects of Post-Processing Parameters on 3D-Printed Dental Appliances: A Review. Polymers, 16.","DOI":"10.3390\/polym16192795"},{"key":"ref_21","doi-asserted-by":"crossref","unstructured":"\u0160imunovi\u0107, L., Brenko, L., Mari\u0107, A.J., Me\u0161trovi\u0107, S., and Haramina, T. (2025). Rheology of Dental Photopolymers for SLA\/DLP\/MSLA 3D Printing. Polymers, 17.","DOI":"10.3390\/polym17192706"},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"25","DOI":"10.21278\/TOF.491054023","article-title":"Post-Processing Tehniques of Additevely Manufactured Parts: A Review","volume":"49","author":"Dabwan","year":"2025","journal-title":"Trans. FAMENA"},{"key":"ref_23","doi-asserted-by":"crossref","unstructured":"\u0160imunovi\u0107, L., \u010cimi\u0107, S., and Me\u0161trovi\u0107, S. (2025). Three-Dimensionally Printed Splints in Dentistry: A Comprehensive Review. Dent. J., 13.","DOI":"10.3390\/dj13070312"},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"6246","DOI":"10.1038\/s41598-022-09831-4","article-title":"Thermo-Mechanical Properties of 3D Printed Photocurable Shape Memory Resin for Clear Aligners","volume":"12","author":"Lee","year":"2022","journal-title":"Sci. Rep."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"466","DOI":"10.1016\/j.ajodo.2025.04.022","article-title":"Absorption and Desorption Dynamics of Thermoformed and 3-Dimensional-Printed Orthodontic Aligners","volume":"168","author":"Brenko","year":"2025","journal-title":"Am. J. Orthod. Dentofac. Orthop."},{"key":"ref_26","doi-asserted-by":"crossref","unstructured":"Karoyo, A.H., and Wilson, L.D. (2021). A Review on the Design and Hydration Properties of Natural Polymer-Based Hydrogels. Materials, 14.","DOI":"10.3390\/ma14051095"},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"15","DOI":"10.1186\/s40510-021-00362-8","article-title":"Dynamic Mechanical and Thermal Properties of Clear Aligners after Thermoforming and Aging","volume":"22","author":"Dalaie","year":"2021","journal-title":"Prog. Orthod."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"3811","DOI":"10.1021\/acs.nanolett.4c00556","article-title":"Viscoelastic Response in Hydrous Polymers: The Role of Hydrogen Bonds and Microstructure","volume":"24","author":"Chen","year":"2024","journal-title":"Nano Lett."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"23530","DOI":"10.1038\/s41598-025-93026-0","article-title":"Mechanical and Viscoelastic Properties of a Temperature-Responsive Photocurable Resin for 3D Printed Orthodontic Clear Aligners","volume":"15","author":"Choi","year":"2025","journal-title":"Sci. Rep."},{"key":"ref_30","doi-asserted-by":"crossref","unstructured":"Cintora-L\u00f3pez, P., Arrieta-Blanco, P., Martin-Vacas, A., Paz-Cort\u00e9s, M.M., Gil, J., and Aragoneses, J.M. (2023). In Vitro Analysis of the Influence of the Thermocycling and the Applied Force on Orthodontic Clear Aligners. Front. Bioeng. Biotechnol., 11.","DOI":"10.3389\/fbioe.2023.1321495"},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"53","DOI":"10.1186\/s40510-025-00600-3","article-title":"Advances in Clear Aligner Therapy: Comparative Evaluation of the Optical Properties and Bacterial Adhesion of 3D Direct-Printed and Thermoformed Aligners","volume":"26","author":"Chen","year":"2025","journal-title":"Prog. Orthod."},{"key":"ref_32","doi-asserted-by":"crossref","unstructured":"Arabpour, F., Aghili, H.A., Javaheri Mahd, M., Arabpour, Z., and Yasaei, S. (2025). Evaluation of Aging Effects on the Physical, Chemical, and Mechanical Properties of Thermoplastic Materials for Orthodontic Clear Aligners: An in Vivo Study. BMC Oral Health, 25.","DOI":"10.1186\/s12903-025-06966-4"},{"key":"ref_33","unstructured":"(2013). Dentistry\u2014Base Polymers\u2014Part 2: Orthodontic Base Polymers (Standard No. ISO 20795-2)."},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"2135","DOI":"10.1016\/j.dental.2024.10.003","article-title":"Chemical Analysis and Performance Evaluation of ClearCorrect\u00ae Aligners as Received and after Intraoral Use: Implications for Durability, Aesthetics, and Patient Safety","volume":"40","author":"Bouchema","year":"2024","journal-title":"Dent. Mater."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"1085540","DOI":"10.1016\/j.polymertesting.2024.108554","article-title":"Water Transport Mechanism and Performance Evaluation in Polyurethane Materials: A State-of-the-Art Review","volume":"138","author":"Wang","year":"2024","journal-title":"Polym. Test."},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"127060","DOI":"10.1016\/j.polymer.2024.127060","article-title":"Water-Polymer Interactions and Mechanisms of Water-Driven Glass Transition Decrease in Non-Isocyanate Polyhydroxyurethanes with Varying Hydration Sites","volume":"302","author":"Bukowczan","year":"2024","journal-title":"Polymer"},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"337","DOI":"10.1007\/s00056-024-00527-0","article-title":"Effect of Thermomechanical Aging on Force System of Orthodontic Aligners Made of Different Thermoformed Materials: An In Vitro Study","volume":"86","author":"Elshazly","year":"2025","journal-title":"J. Orofac. Orthop."},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"42","DOI":"10.1186\/s40510-024-00540-4","article-title":"Polymerization Kinetics of 3D-Printed Orthodontic Aligners under Different UV Post-Curing Conditions","volume":"25","author":"Manoukakis","year":"2024","journal-title":"Prog. Orthod."},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"5864","DOI":"10.1038\/s41598-026-36723-8","article-title":"Mechanical Properties of Thermoformed and Direct-Printed Aligner Materials after Immersion in 37 \u00b0C Water: A 14-Day in Vitro Study","volume":"16","author":"Oyonarte","year":"2026","journal-title":"Sci. Rep."},{"key":"ref_40","doi-asserted-by":"crossref","unstructured":"Puchert, K., Ritzert, P., Wille, S., Naim, J., and \u015een, S. (2025). Influence of Water Storage on the Mechanical Properties of 3D-Printed Aligners: An In Vitro Study. Bioengineering, 13.","DOI":"10.3390\/bioengineering13010021"},{"key":"ref_41","doi-asserted-by":"crossref","first-page":"299","DOI":"10.25259\/APOS_61_2025","article-title":"Assessment of Active Memory of Photo-Curable Resins for LuxCreo DCA Direct-Printed 3D Aligners","volume":"15","author":"Retrouvey","year":"2025","journal-title":"APOS Trends Orthod."},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"44","DOI":"10.1186\/s40510-025-00591-1","article-title":"Force Comparison between Perfitalign 4D Aligners and Thermoformed Aligners for Mandibular Incisor Retraction: An in Vitro Study","volume":"26","author":"Xu","year":"2025","journal-title":"Prog. Orthod."},{"key":"ref_43","doi-asserted-by":"crossref","unstructured":"\u0160imunovi\u0107, L., Jurela, A., Sudarevi\u0107, K., Ba\u010di\u0107, I., Haramina, T., and Me\u0161trovi\u0107, S. (2024). Influence of Post-Processing on the Degree of Conversion and Mechanical Properties of 3D-Printed Polyurethane Aligners. Polymers, 16.","DOI":"10.3390\/polym16010017"}],"container-title":["Polymers"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2073-4360\/18\/8\/1008\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,4,25]],"date-time":"2026-04-25T04:12:23Z","timestamp":1777090343000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2073-4360\/18\/8\/1008"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,4,21]]},"references-count":43,"journal-issue":{"issue":"8","published-online":{"date-parts":[[2026,4]]}},"alternative-id":["polym18081008"],"URL":"https:\/\/doi.org\/10.3390\/polym18081008","relation":{},"ISSN":["2073-4360"],"issn-type":[{"value":"2073-4360","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,4,21]]}}}