{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,24]],"date-time":"2026-10-24T01:46:47Z","timestamp":1792806407783,"version":"4.5.0"},"reference-count":75,"publisher":"MDPI AG","issue":"8","license":[{"start":{"date-parts":[[2023,4,14]],"date-time":"2023-04-14T00:00:00Z","timestamp":1681430400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100006360","name":"Federal Ministry for Economic Affairs and Climate Action (BMWK)","doi-asserted-by":"publisher","award":["20400 BG"],"award-info":[{"award-number":["20400 BG"]}],"id":[{"id":"10.13039\/501100006360","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Materials"],"abstract":"<jats:p>Aligner therapy for orthodontic tooth movement is gaining importance in orthodontics. The aim of this contribution is to introduce a thermo- and water-responsive shape memory polymer (SMP), which could lay the foundation for a new type of aligner therapy. The thermal, thermo-mechanical, and shape memory properties of thermoplastic polyurethane were studied by means of differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and various practical experiments. The glass transition temperature of the SMP relevant for later switching was determined to be 50 \u00b0C in the DSC, while the tan \u03b4 peak was detected at 60 \u00b0C in the DMA. A biological evaluation was carried out using mouse fibroblast cells, which showed that the SMP is not cytotoxic in vitro. On a digitally designed and additively manufactured dental model, four aligners were fabricated from an injection-molded foil using a thermoforming process. The aligners were then heated and placed on a second denture model which had a malocclusion. After cooling, the aligners were in a programmed shape. The movement of a loose, artificial tooth and thus the correction of the malocclusion could be realized by thermal triggering the shape memory effect, at which the aligner corrected a displacement with an arc length of approximately 3.5 mm. The developed maximum force was separately determined to be about 1 N. Moreover, shape recovery of another aligner was realized within 20 h in 37 \u00b0C water. In perspective, the present approach can help to reduce the number of orthodontic aligners in therapy and thus avoid excessive material waste.<\/jats:p>","DOI":"10.3390\/ma16083094","type":"journal-article","created":{"date-parts":[[2023,4,14]],"date-time":"2023-04-14T02:03:38Z","timestamp":1681437818000},"page":"3094","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":13,"title":["Dual Stimuli-Responsive Orthodontic Aligners: An In Vitro Study"],"prefix":"10.3390","volume":"16","author":[{"given":"Dennis","family":"Sch\u00f6nfeld","sequence":"first","affiliation":[{"name":"Fraunhofer Institute for Applied Polymer Research IAP, Geiselbergstr. 69, 14476 Potsdam, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Samantha","family":"Koss","sequence":"additional","affiliation":[{"name":"Department of Orthodontics, Universit\u00e4tsklinikum D\u00fcsseldorf, Moorenstr. 5, 40225 D\u00fcsseldorf, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Nils","family":"Vohl","sequence":"additional","affiliation":[{"name":"Department of Orthodontics, Universit\u00e4tsklinikum D\u00fcsseldorf, Moorenstr. 5, 40225 D\u00fcsseldorf, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Fabian","family":"Friess","sequence":"additional","affiliation":[{"name":"Fraunhofer Institute for Applied Polymer Research IAP, Geiselbergstr. 69, 14476 Potsdam, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Dieter","family":"Drescher","sequence":"additional","affiliation":[{"name":"Department of Orthodontics, Universit\u00e4tsklinikum D\u00fcsseldorf, Moorenstr. 5, 40225 D\u00fcsseldorf, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5591-7866","authenticated-orcid":false,"given":"Thorsten","family":"Pretsch","sequence":"additional","affiliation":[{"name":"Fraunhofer Institute for Applied Polymer Research IAP, Geiselbergstr. 69, 14476 Potsdam, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2023,4,14]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"202","DOI":"10.5152\/TurkJOrthod.2021.20116","article-title":"Staging Orthodontic Aligners for Complex Orthodontic Tooth Movement","volume":"34","author":"Mehta","year":"2021","journal-title":"Turk. J. Orthod."},{"key":"ref_2","doi-asserted-by":"crossref","unstructured":"Ludovichetti, F.S., Zuccon, A., Lucchi, P., Cattaruzza, G., Zerman, N., Stellini, E., and Mazzoleni, S. (2022). Mothers\u2019 Awareness of the Correlation between Their Own and Their Children\u2019s Oral Health. Int. J. Environ. Res. Public Health, 19.","DOI":"10.3390\/ijerph192214967"},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"228","DOI":"10.1016\/j.ajodo.2006.03.034","article-title":"Force delivery properties of thermoplastic orthodontic materials","volume":"133","author":"Kwon","year":"2008","journal-title":"Am. J. Orthod. Dentofacial Orthop."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"728","DOI":"10.1016\/j.ajodo.2014.03.015","article-title":"Forces and moments generated by removable thermoplastic aligners: Incisor torque, premolar derotation, and molar distalization","volume":"145","author":"Simon","year":"2014","journal-title":"Am. J. Orthod. Dentofacial Orthop."},{"key":"ref_5","doi-asserted-by":"crossref","unstructured":"Simon, M., Keilig, L., Schwarze, J., Jung, B.A., and Bourauel, C. (2014). Treatment outcome and efficacy of an aligner technique\u2014Regarding incisor torque, premolar derotation and molar distalization. BMC Oral Health, 14.","DOI":"10.1186\/1472-6831-14-68"},{"key":"ref_6","doi-asserted-by":"crossref","unstructured":"Timm, L.H., Farrag, G., Baxmann, M., and Schwendicke, F. (2021). Factors Influencing Patient Compliance during Clear Aligner Therapy: A Retrospective Cohort Study. J. Clin. Med., 10.","DOI":"10.3390\/jcm10143103"},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"1001","DOI":"10.1016\/j.jds.2021.01.011","article-title":"Effects of different aligner materials and attachments on orthodontic behavior","volume":"16","author":"Ho","year":"2021","journal-title":"J. Dent. Sci."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"194","DOI":"10.1002\/jbm.b.35145","article-title":"Investigating the role of aligner material and tooth position on orthodontic aligner biomechanics","volume":"111","author":"Kaur","year":"2023","journal-title":"J. Biomed. Mater. Res. B Appl. Biomater."},{"key":"ref_9","unstructured":"Straumann (2023, January 02). ClearCorrect\u00ae: ClearQuartz\u00ae Material. Available online: https:\/\/www.straumann.com\/clearcorrect\/de\/de\/behandler\/clearquartz.html."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"54","DOI":"10.1016\/S1369-7021(10)70128-0","article-title":"Shape memory materials","volume":"13","author":"Huang","year":"2010","journal-title":"Mater. Today"},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"39","DOI":"10.1080\/14786440608563329","article-title":"VII. A description of a property of caoutchouc, or indian rubber; with some reflections on the cause of the elasticity of this substance. In a letter to Dr.Holme","volume":"24","author":"Holme","year":"1806","journal-title":"Philos. Mag."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"79","DOI":"10.1016\/j.progpolymsci.2015.04.001","article-title":"Recent progress in shape memory polymer: New behavior, enabling materials, and mechanistic understanding","volume":"49\u201350","author":"Zhao","year":"2015","journal-title":"Prog. Polym. Sci."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"425","DOI":"10.1595\/205651319X15754757916993","article-title":"A Mini-Review of Shape-Memory Polymer-Based Materials: Stimuli-responsive shape-memory polymers","volume":"64","author":"Haskew","year":"2020","journal-title":"Johns. Matthey Technol. Rev."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"e2000713","DOI":"10.1002\/adma.202000713","article-title":"A Review of Shape Memory Polymers and Composites: Mechanisms, Materials, and Applications","volume":"33","author":"Xia","year":"2021","journal-title":"Adv. Mater."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"3356","DOI":"10.1039\/b923717h","article-title":"Biomedical applications of thermally activated shape memory polymers","volume":"20","author":"Small","year":"2010","journal-title":"J. Mater. Chem."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"143","DOI":"10.1007\/s11705-017-1632-4","article-title":"A mini review: Shape memory polymers for biomedical applications","volume":"11","author":"Wang","year":"2017","journal-title":"Front. Chem. Sci. Eng."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"66","DOI":"10.3389\/fmats.2018.00066","article-title":"Softening Shape Memory Polymer Substrates for Bioelectronic Devices With Improved Hydrolytic Stability","volume":"5","author":"Hosseini","year":"2018","journal-title":"Front. Mater."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"12161","DOI":"10.1088\/1757-899X\/993\/1\/012161","article-title":"An Extensive Review of Shape Memory Polymers for Biomedical Applications","volume":"993","author":"Gayathri","year":"2020","journal-title":"IOP Conf. Ser. Mater. Sci. Eng."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"864","DOI":"10.1016\/j.msec.2018.12.054","article-title":"Shape memory polymers and their composites in biomedical applications","volume":"97","author":"Zhao","year":"2019","journal-title":"Mater. Sci. Eng. C Mater. Biol. Appl."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"1909047","DOI":"10.1002\/adfm.201909047","article-title":"Shape-Memory Polymers for Biomedical Applications","volume":"30","author":"Delaey","year":"2020","journal-title":"Adv. Funct. Mater."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"1597","DOI":"10.1039\/C8TB02579G","article-title":"Shape-changing polymers for biomedical applications","volume":"7","author":"Kirillova","year":"2019","journal-title":"J. Mater. Chem. B"},{"key":"ref_22","doi-asserted-by":"crossref","unstructured":"Sun, L., Wang, T.X., Chen, H.M., Salvekar, A.V., Naveen, B.S., Xu, Q., Weng, Y., Guo, X., Chen, Y., and Huang, W.M. (2019). A Brief Review of the Shape Memory Phenomena in Polymers and Their Typical Sensor Applications. Polymers, 11.","DOI":"10.3390\/polym11061049"},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"5952","DOI":"10.1021\/ma501171p","article-title":"Programming of Temperature-Memory Onsets in a Semicrystalline Polyurethane Elastomer","volume":"47","author":"Fritzsche","year":"2014","journal-title":"Macromolecules"},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"2287","DOI":"10.3390\/polym6082287","article-title":"Advanced Shape Memory Technology to Reshape Product Design, Manufacturing and Recycling","volume":"6","author":"Yang","year":"2014","journal-title":"Polymers"},{"key":"ref_25","doi-asserted-by":"crossref","unstructured":"Scalet, G. (2020). Two-Way and Multiple-Way Shape Memory Polymers for Soft Robotics: An Overview. Actuators, 9.","DOI":"10.3390\/act9010010"},{"key":"ref_26","unstructured":"Khan, T. (2023, January 02). Soft Robotics and Actuators Benefit from Shape Memory Polymers. Available online: https:\/\/www.azorobotics.com\/Article.aspx?ArticleID=515."},{"key":"ref_27","doi-asserted-by":"crossref","unstructured":"Sch\u00f6nfeld, D., Chalissery, D., Wenz, F., Specht, M., Eberl, C., and Pretsch, T. (2021). Actuating Shape Memory Polymer for Thermoresponsive Soft Robotic Gripper and Programmable Materials. Molecules, 26.","DOI":"10.3390\/molecules26030522"},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"1543","DOI":"10.1039\/b615954k","article-title":"Review of progress in shape-memory polymers","volume":"17","author":"Liu","year":"2007","journal-title":"J. Mater. Chem."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"120","DOI":"10.3390\/polym2030120","article-title":"Review on the Functional Determinants and Durability of Shape Memory Polymers","volume":"2","author":"Pretsch","year":"2010","journal-title":"Polymers"},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"268","DOI":"10.1016\/j.eurpolymj.2016.05.004","article-title":"Shape-memory polymers for multiple applications in the materials world","volume":"80","author":"Pilate","year":"2016","journal-title":"Eur. Polym. J."},{"key":"ref_31","doi-asserted-by":"crossref","unstructured":"Karger-Kocsis, J., and K\u00e9ki, S. (2017). Review of Progress in Shape Memory Epoxies and Their Composites. Polymers, 10.","DOI":"10.3390\/polym10010034"},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"1168","DOI":"10.1002\/marc.200600225","article-title":"Electromagnetic Activation of Shape Memory Polymer Networks Containing Magnetic Nanoparticles","volume":"27","author":"Schmidt","year":"2006","journal-title":"Macromol. Rapid Commun."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"e1906657","DOI":"10.1002\/adma.201906657","article-title":"Magnetic Shape Memory Polymers with Integrated Multifunctional Shape Manipulation","volume":"32","author":"Ze","year":"2020","journal-title":"Adv. Mater."},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"2201022","DOI":"10.1002\/adem.202201022","article-title":"Controlling Malleability of Metamaterials through Programmable Memory","volume":"25","author":"Wenz","year":"2022","journal-title":"Adv. Eng. Mater."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"412","DOI":"10.1002\/marc.200400492","article-title":"Electroactive Shape-Memory Polyurethane Composites Incorporating Carbon Nanotubes","volume":"26","author":"Cho","year":"2005","journal-title":"Macromol. Rapid Commun."},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"74003","DOI":"10.1088\/0964-1726\/18\/7\/074003","article-title":"Electroactive thermoset shape memory polymer nanocomposite filled with nanocarbon powders","volume":"18","author":"Leng","year":"2009","journal-title":"Smart Mater. Struct."},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"170","DOI":"10.1016\/j.compositesb.2014.08.043","article-title":"Electroactive shape memory polymer based on optimized multi-walled carbon nanotubes\/polyvinyl alcohol nanocomposites","volume":"68","author":"Du","year":"2015","journal-title":"Compos. Part B Eng."},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"5535","DOI":"10.1038\/s41598-017-05968-9","article-title":"Fabricating fast triggered electro-active shape memory graphite\/silver nanowires\/epoxy resin composite from polymer template","volume":"7","author":"Zhou","year":"2017","journal-title":"Sci. Rep."},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"1700149","DOI":"10.1002\/marc.201700149","article-title":"Semi-IPNs with Moisture-Triggered Shape Memory and Self-Healing Properties","volume":"38","author":"Jiang","year":"2017","journal-title":"Macromol. Rapid Commun."},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"114105","DOI":"10.1063\/1.1880448","article-title":"Water-driven programmable polyurethane shape memory polymer: Demonstration and mechanism","volume":"86","author":"Huang","year":"2005","journal-title":"Appl. Phys. Lett."},{"key":"ref_41","doi-asserted-by":"crossref","first-page":"5168","DOI":"10.1039\/C4PY00474D","article-title":"Highly pH-sensitive polyurethane exhibiting shape memory and drug release","volume":"5","author":"Chen","year":"2014","journal-title":"Polym. Chem."},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"409","DOI":"10.3144\/expresspolymlett.2011.40","article-title":"Water-responsive shape memory hybrid: Design concept and demonstration","volume":"5","author":"Fan","year":"2011","journal-title":"Express Polym. Lett."},{"key":"ref_43","doi-asserted-by":"crossref","first-page":"1055","DOI":"10.1002\/marc.201200153","article-title":"pH-induced shape-memory polymers","volume":"33","author":"Han","year":"2012","journal-title":"Macromol. Rapid Commun."},{"key":"ref_44","doi-asserted-by":"crossref","first-page":"12988","DOI":"10.1021\/acsami.5b02940","article-title":"pH-Responsive Shape Memory Poly(ethylene glycol)-Poly(\u03b5-caprolactone)-based Polyurethane\/Cellulose Nanocrystals Nanocomposite","volume":"7","author":"Li","year":"2015","journal-title":"ACS Appl. Mater. Interfaces"},{"key":"ref_45","doi-asserted-by":"crossref","first-page":"767","DOI":"10.1039\/C6QM00243A","article-title":"Dual-responsive hybrid thermoplastic shape memory polyurethane","volume":"1","author":"Chan","year":"2017","journal-title":"Mater. Chem. Front."},{"key":"ref_46","doi-asserted-by":"crossref","unstructured":"Wang, C., Wang, H., Zou, F., Chen, S., and Wang, Y. (2019). Development of Polyhydroxyalkanoate-Based Polyurethane with Water-Thermal Response Shape-Memory Behavior as New 3D Elastomers Scaffolds. Polymers, 11.","DOI":"10.3390\/polym11061030"},{"key":"ref_47","doi-asserted-by":"crossref","first-page":"148","DOI":"10.1007\/s10856-018-6157-y","article-title":"Thermo-Mechanical Properties of Glass Fiber Reinforced Shape Memory Polyurethane for Orthodontic Application","volume":"29","author":"Liu","year":"2018","journal-title":"J. Mater. Sci. Mater. Med."},{"key":"ref_48","doi-asserted-by":"crossref","first-page":"666","DOI":"10.1007\/s40846-017-0263-z","article-title":"Feasible Evaluation of the Thermo-mechanical Properties of Shape Memory Polyurethane for Orthodontic Archwire","volume":"37","author":"Liu","year":"2017","journal-title":"J. Med. Biol. Eng."},{"key":"ref_49","doi-asserted-by":"crossref","first-page":"2881","DOI":"10.1007\/s10856-008-3538-7","article-title":"Application of shape memory polyurethane in orthodontic","volume":"21","author":"Jung","year":"2010","journal-title":"J. Mater. Sci. Mater. Med."},{"key":"ref_50","doi-asserted-by":"crossref","first-page":"179","DOI":"10.1093\/ejo\/13.3.179","article-title":"Potential application of shape memory plastic as elastic material in clinical orthodontics","volume":"13","author":"Nakasima","year":"1991","journal-title":"Eur. J. Orthod."},{"key":"ref_51","doi-asserted-by":"crossref","unstructured":"Elshazly, T.M., Keilig, L., Alkabani, Y., Ghoneima, A., Abuzayda, M., Talaat, S., and Bourauel, C.P. (2021). Primary Evaluation of Shape Recovery of Orthodontic Aligners Fabricated from Shape Memory Polymer (A Typodont Study). Dent. J., 9.","DOI":"10.3390\/dj9030031"},{"key":"ref_52","doi-asserted-by":"crossref","first-page":"794536","DOI":"10.3389\/fmats.2021.794536","article-title":"Potential Application of 4D Technology in Fabrication of Orthodontic Aligners","volume":"8","author":"Elshazly","year":"2022","journal-title":"Front. Mater."},{"key":"ref_53","unstructured":"Covestro Deutschland AG (2023, January 02). Desmophen\u00ae 1262 BD. Technical Data Sheet. Available online: https:\/\/solutions.covestro.com\/-\/media\/covestro\/solution-center\/products\/datasheets\/imported\/desmophen\/desmophen-1262-bd_en_05629268-00010114-00034060.pdf."},{"key":"ref_54","doi-asserted-by":"crossref","first-page":"2100619","DOI":"10.1002\/mame.202100619","article-title":"Highly Shrinkable Objects as Obtained from 4D Printing","volume":"307","author":"Chalissery","year":"2022","journal-title":"Macro Mater. Eng."},{"key":"ref_55","unstructured":"(1996). Plastics\u2014Determination of Tensile Properties\u2014Part 2: Test Conditions for Moulding and Extrusion Plastics (Standard No. DIN EN ISO 527-2-1996-07). Available online: https:\/\/www.beuth.de\/en\/standard\/din-en-iso-527-2\/2808009."},{"key":"ref_56","unstructured":"(2022, November 17). Ultimaker Cura: Powerful, Easy-to-Use 3D Printing Software. Available online: https:\/\/ultimaker.com\/software\/ultimaker-cura."},{"key":"ref_57","unstructured":"(2009). Biological Evaluation of Medical Devices\u2014Part 5: Tests for In Vitro Cytotoxicity (Standard No. DIN EN ISO 10993-5:2009-10). Available online: https:\/\/www.beuth.de\/de\/norm\/din-en-iso-10993-5\/113571989."},{"key":"ref_58","unstructured":"(2022, November 17). ArchForm. Available online: https:\/\/www.archform.com\/."},{"key":"ref_59","unstructured":"(2022, November 17). Blender. Available online: https:\/\/www.blender.org."},{"key":"ref_60","unstructured":"CorelDRAW (2022, November 17). Graphics Suite. Available online: https:\/\/www.coreldraw.com\/de."},{"key":"ref_61","doi-asserted-by":"crossref","first-page":"540","DOI":"10.1002\/app.26593","article-title":"Shape memory polymers based on uniform aliphatic urethane networks","volume":"106","author":"Wilson","year":"2007","journal-title":"J. Appl. Polym. Sci."},{"key":"ref_62","first-page":"296","article-title":"Mechanical Properties of Shape Memory Polymer of Polyurethane Series: Basic Characteristics of Stress-Strain-Temperature Relationship","volume":"35","author":"Tobushi","year":"1992","journal-title":"JSME Int. J. Ser. 1 Solid Mech. Strength Mater."},{"key":"ref_63","doi-asserted-by":"crossref","first-page":"5781","DOI":"10.1016\/S0032-3861(96)00442-9","article-title":"Polyurethanes having shape memory effects","volume":"37","author":"Kim","year":"1996","journal-title":"Polymer"},{"key":"ref_64","doi-asserted-by":"crossref","first-page":"61","DOI":"10.1016\/j.polymdegradstab.2008.10.012","article-title":"Hydrolytic degradation and functional stability of a segmented shape memory poly(ester urethane)","volume":"94","author":"Pretsch","year":"2009","journal-title":"Polym. Degrad. Stab."},{"key":"ref_65","doi-asserted-by":"crossref","first-page":"2034","DOI":"10.1002\/1521-3773(20020617)41:12<2034::AID-ANIE2034>3.0.CO;2-M","article-title":"Shape-Memory Polymers","volume":"41","author":"Lendlein","year":"2002","journal-title":"Angew. Chem. Int. Ed."},{"key":"ref_66","doi-asserted-by":"crossref","unstructured":"Possart, W., and Zimmer, B. (2022). Water in polyurethane networks: Physical and chemical ageing effects and mechanical parameters. Continuum Mech. Thermodyn., 1\u201327.","DOI":"10.1007\/s00161-022-01082-y"},{"key":"ref_67","doi-asserted-by":"crossref","first-page":"191","DOI":"10.1088\/0964-1726\/13\/1\/022","article-title":"On the effects of moisture in a polyurethane shape memory polymer","volume":"13","author":"Yang","year":"2004","journal-title":"Smart Mater. Struct."},{"key":"ref_68","doi-asserted-by":"crossref","first-page":"1348","DOI":"10.1016\/j.polymer.2005.12.051","article-title":"Effects of moisture on the thermomechanical properties of a polyurethane shape memory polymer","volume":"47","author":"Yang","year":"2006","journal-title":"Polymer"},{"key":"ref_69","unstructured":"Bioserv Analytik- und Medizinprodukte GmbH (2021, February 09). DIN-Certified Test Report: Synthesized TPU\u2014Fraunhofer IAP. Available online: https:\/\/www.bioserv.de\/de\/start.html."},{"key":"ref_70","doi-asserted-by":"crossref","first-page":"607","DOI":"10.1093\/ejo\/cjq007","article-title":"Torquing an upper central incisor with aligners\u2014Acting forces and biomechanical principles","volume":"32","author":"Hahn","year":"2010","journal-title":"Eur. J. Orthod."},{"key":"ref_71","doi-asserted-by":"crossref","first-page":"69094","DOI":"10.1039\/C6RA13492K","article-title":"Methylene diphenyl diisocyanate (MDI) and toluene diisocyanate (TDI) based polyurethanes: Thermal, shape-memory and mechanical behavior","volume":"6","author":"Lizundia","year":"2016","journal-title":"RSC Adv."},{"key":"ref_72","doi-asserted-by":"crossref","first-page":"49997","DOI":"10.1002\/app.49997","article-title":"Synthesis and characterization of polypropylene glycol-based novel organogels as effective materials for the recovery of organic solvents","volume":"138","author":"Erdem","year":"2021","journal-title":"J. Appl. Polym. Sci."},{"key":"ref_73","doi-asserted-by":"crossref","unstructured":"Tan, C., Tirri, T., and Wilen, C.-E. (2017). Investigation on the Influence of Chain Extenders on the Performance of One-Component Moisture-Curable Polyurethane Adhesives. Polymers, 9.","DOI":"10.3390\/polym9050184"},{"key":"ref_74","doi-asserted-by":"crossref","first-page":"94","DOI":"10.1007\/s10965-015-0744-0","article-title":"The influence of 2,4-toluene diisocyanate content on the intrinsic self-healing performance of polyurethane at room-temperature","volume":"22","author":"Zhang","year":"2015","journal-title":"J. Polym. Res."},{"key":"ref_75","doi-asserted-by":"crossref","first-page":"4614","DOI":"10.1016\/j.polymer.2012.08.020","article-title":"Effect of soft segment molecular weight on tensile properties of poly(propylene oxide) based polyurethaneureas","volume":"53","author":"Yilgor","year":"2012","journal-title":"Polymer"}],"container-title":["Materials"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1996-1944\/16\/8\/3094\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,10]],"date-time":"2025-10-10T19:15:34Z","timestamp":1760123734000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1996-1944\/16\/8\/3094"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2023,4,14]]},"references-count":75,"journal-issue":{"issue":"8","published-online":{"date-parts":[[2023,4]]}},"alternative-id":["ma16083094"],"URL":"https:\/\/doi.org\/10.3390\/ma16083094","relation":{},"ISSN":["1996-1944"],"issn-type":[{"value":"1996-1944","type":"electronic"}],"subject":[],"published":{"date-parts":[[2023,4,14]]}}}