Extrusion of lower second premolars with Nuvola® clear aligners: a time-dependent finite element framework for assessing displacement efficiency and contact force trends

Extrusion of lower second premolars with Nuvola® clear aligners: a time-dependent finite element framework for assessing displacement efficiency and contact force trends | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Extrusion of lower second premolars with Nuvola® clear aligners: a time-dependent finite element framework for assessing displacement efficiency and contact force trends Gianluigi Fiorillo, Stefan Leonard Mucenica, Alice Mandelli, Alessandro Artenisio Carducci, and 4 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7386790/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Context: Predicting a patient-specific clear aligner (CA) therapy outcome is challenging, especially when exploring the connection between aligner-to-tooth contact force transmission and tooth displacement. The periodontal ligament (PDL) response is fundamental in this interaction and, when simulated in a virtual environment, requires realistic approximations. This study evaluated extrusion efficiency and contact force trends in lower second premolars, using various attachment configurations. The PDL position was updated between multiple Nuvola® aligners during treatment. Simulations were run in FEBio. Methodology: In a finite element method (FEM) framework, three differently shaped attachments (horizontal rectangular, Nuvola®-drop and beveled) were applied on second premolars, with a retention group on adjacent teeth. Six aligners were designed to achieve a 0.15mm extrusion each (14 days of use) while the PDL was modeled as a coupled hyper-viscoelastic material and repositioned after each aligner use in an iterative scheme. Displacement efficiency was calculated by means of four metrics, and contact forces were another output. Results: Contact force trends in time showed highest initial peak and residual with the rectangular attachment, without significantly increasing efficiency as compared to the other attachments. They exhibited values in the range of 5 - 35 gf (∼= 0.05 - 0.35 N), in accordance with in vitro tests in literature. Angle-dependent efficiency metrics with penalty factors gave realistic results, with rough values in the range of 40-70%, depending on tooth, attachment and metric. Contact forces recorded a decrease during single aligner use, reflecting the PDL viscoelastic relaxation and progressive aligner adaptation. Conclusions: An appropriate PDL model was essential to predict teeth movement efficiency and contact force trends during CA therapy. Attachment designs strongly influenced force magnitudes, while it had a limited influence on the extrusion efficiency when compared to each other; however, all designs have shown a significant improvement in terms of efficiency with respect to no-attachment cases. Also, the retention group induced a more symmetric response of the two premolars. Future studies could implement patient-specific PDL properties calibration and integrate FEM tools to orthodontic setup software, increasing predictability of an actual treatment outcome and supporting aligner design optimization. Finite-element method Premolar extrusion Clear aligners Time-dependent orthodontic treatment simulation Multiple aligner use Hyper-viscoelasticity Periodontal Ligament Nuvola® FEBio Full Text Additional Declarations Competing interest reported. Financial interests: S.L.M. worked as an employee for Nuvola (G.E.O Srl) during part of the project, while for another part S.L.M. was a consultant to the same company (Nuvola, G.E.O. Srl), as a sole proprietorship (Enfebiome, a biomedical engineering initiative officially registered as Mucenica Stefan-Leonard, PFA). G.F., G.M., M.C., A.A.C., and V.F. have an ongoing (non-commercial) research and development contract with Nuvola (G.E.O. Srl) Funding: the research for the study received funding from Nuvola (G.E.O. Srl) Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-7386790","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":512693362,"identity":"dc3c697e-0221-41a0-b0b6-9fb059fbb43d","order_by":0,"name":"Gianluigi Fiorillo","email":"","orcid":"","institution":"Vita-Salute San Raffaele University","correspondingAuthor":false,"prefix":"","firstName":"Gianluigi","middleName":"","lastName":"Fiorillo","suffix":""},{"id":512693363,"identity":"b2d7ce9e-aa86-4347-8998-108460f9be8f","order_by":1,"name":"Stefan Leonard Mucenica","email":"data:image/png;base64,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","orcid":"","institution":"Nuvola (Gruppo Europeo di Ortodonzia)","correspondingAuthor":true,"prefix":"","firstName":"Stefan","middleName":"Leonard","lastName":"Mucenica","suffix":""},{"id":512693364,"identity":"b6cd4db8-bf8e-4848-95fa-f280f13b1c6d","order_by":2,"name":"Alice Mandelli","email":"","orcid":"","institution":"Vita-Salute San Raffaele University","correspondingAuthor":false,"prefix":"","firstName":"Alice","middleName":"","lastName":"Mandelli","suffix":""},{"id":512693365,"identity":"8853ad2f-f009-4671-ba6d-b75e48a1674b","order_by":3,"name":"Alessandro Artenisio Carducci","email":"","orcid":"","institution":"Nuvola (Gruppo Europeo di Ortodonzia)","correspondingAuthor":false,"prefix":"","firstName":"Alessandro","middleName":"Artenisio","lastName":"Carducci","suffix":""},{"id":512693366,"identity":"824735be-e51c-404b-9854-ea32921091ce","order_by":4,"name":"Matteo Colosimo","email":"","orcid":"","institution":"Nuvola (Gruppo Europeo di Ortodonzia)","correspondingAuthor":false,"prefix":"","firstName":"Matteo","middleName":"","lastName":"Colosimo","suffix":""},{"id":512693367,"identity":"fe7862eb-0e52-4ed9-8e30-e16d6a7f27fd","order_by":5,"name":"Valerio Fornari","email":"","orcid":"","institution":"Nuvola (Gruppo Europeo di Ortodonzia)","correspondingAuthor":false,"prefix":"","firstName":"Valerio","middleName":"","lastName":"Fornari","suffix":""},{"id":512693368,"identity":"c8c5ba7a-93f3-4509-bbbd-b5500f6816c3","order_by":6,"name":"Giorgio Gastaldi","email":"","orcid":"","institution":"Vita-Salute San Raffaele University","correspondingAuthor":false,"prefix":"","firstName":"Giorgio","middleName":"","lastName":"Gastaldi","suffix":""},{"id":512693369,"identity":"6a731ecc-6ccd-4c65-9e85-0734fa81464b","order_by":7,"name":"Gualtiero Mandelli","email":"","orcid":"","institution":"Vita-Salute San Raffaele University","correspondingAuthor":false,"prefix":"","firstName":"Gualtiero","middleName":"","lastName":"Mandelli","suffix":""}],"badges":[],"createdAt":"2025-08-16 10:23:08","currentVersionCode":1,"declarations":{"humanSubjects":false,"vertebrateSubjects":false,"conflictsOfInterestStatement":true,"humanSubjectEthicalGuidelines":false,"humanSubjectConsent":false,"humanSubjectClinicalTrial":false,"humanSubjectCaseReport":false,"vertebrateSubjectEthicalGuidelines":false},"doi":"10.21203/rs.3.rs-7386790/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-7386790/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":99788626,"identity":"a037519e-50bb-4418-b991-724458f244f5","added_by":"auto","created_at":"2026-01-08 12:47:20","extension":"pdf","order_by":1,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1372756,"visible":true,"origin":"","legend":"","description":"","filename":"ArticleSubmittedVersionProgressinOrthodontics.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7386790/v1_covered_b52a32d2-605d-4f27-93c7-f8a1d2b490c6.pdf"}],"financialInterests":"Competing interest reported. Financial interests: S.L.M. worked as an employee for Nuvola (G.E.O Srl) during part of the project, while for another part S.L.M. was a consultant to the same company (Nuvola, G.E.O. Srl), as a sole proprietorship (Enfebiome, a biomedical engineering initiative officially registered as Mucenica Stefan-Leonard, PFA). \n\nG.F., G.M., M.C., A.A.C., and V.F. have an ongoing (non-commercial) research and development contract with Nuvola (G.E.O. Srl)\n\nFunding: the research for the study received funding from Nuvola (G.E.O. Srl)","formattedTitle":"\u003cp\u003eExtrusion of lower second premolars with Nuvola® clear aligners: a time-dependent finite element framework for assessing displacement efficiency and contact force trends\u003c/p\u003e","fulltext":[],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":false,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":true,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":true,"isPdf":true,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Finite-element method, Premolar extrusion, Clear aligners, Time-dependent orthodontic treatment simulation, Multiple aligner use, Hyper-viscoelasticity, Periodontal Ligament, Nuvola®, FEBio","lastPublishedDoi":"10.21203/rs.3.rs-7386790/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7386790/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eContext: Predicting a patient-specific clear aligner (CA) therapy outcome is challenging, especially when exploring the connection between aligner-to-tooth contact force transmission and tooth displacement. The periodontal ligament (PDL) response is fundamental in this interaction and, when simulated in a virtual environment, requires realistic approximations. This study evaluated extrusion efficiency and contact force trends in lower second premolars, using various attachment configurations. The PDL position was updated between multiple Nuvola® aligners during treatment. Simulations were run in FEBio.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eMethodology: In a finite element method (FEM) framework, three differently shaped attachments (horizontal rectangular, Nuvola®-drop and beveled) were applied on second premolars, with a retention group on adjacent teeth. Six aligners were designed to achieve a 0.15mm extrusion each (14 days of use) while the PDL was modeled as a coupled hyper-viscoelastic material and repositioned after each aligner use in an iterative scheme. Displacement efficiency was calculated by means of four metrics, and contact forces were another output.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eResults: Contact force trends in time showed highest initial peak and residual with the rectangular attachment, without significantly increasing efficiency as compared to the other attachments. They exhibited values in the range of 5 - 35 gf (∼= 0.05 - 0.35 N), in accordance with in vitro tests in literature. Angle-dependent efficiency metrics with penalty factors gave realistic results, with rough values in the range of 40-70%, depending on tooth, attachment and metric. Contact forces recorded a decrease during single aligner use, reflecting the PDL viscoelastic relaxation and progressive aligner adaptation.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eConclusions: An appropriate PDL model was essential to predict teeth movement efficiency and contact force trends during CA therapy. Attachment designs strongly influenced force magnitudes, while it had a limited influence on the extrusion efficiency when compared to each other; however, all designs have shown a significant improvement in terms of efficiency with respect to no-attachment cases. Also, the retention group induced a more symmetric response of the two premolars. Future studies could implement patient-specific PDL properties calibration and integrate FEM tools to orthodontic setup software, increasing predictability of an actual treatment outcome and supporting aligner design optimization.\u0026nbsp;\u003c/p\u003e","manuscriptTitle":"Extrusion of lower second premolars with Nuvola® clear aligners: a time-dependent finite element framework for assessing displacement efficiency and contact force trends","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-09-12 23:27:44","doi":"10.21203/rs.3.rs-7386790/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"cd332095-8241-4ad6-9957-5abdd3451206","owner":[],"postedDate":"September 12th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2025-12-31T20:08:33+00:00","versionOfRecord":[],"versionCreatedAt":"2025-09-12 23:27:44","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7386790","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7386790","identity":"rs-7386790","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}