{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,7]],"date-time":"2026-09-07T15:08:56Z","timestamp":1788793736926,"version":"build-2803163510"},"reference-count":48,"publisher":"MDPI AG","issue":"9","license":[{"start":{"date-parts":[[2026,9,7]],"date-time":"2026-09-07T00:00:00Z","timestamp":1788739200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Children"],"abstract":"<jats:p>Background\/Objectives: Class II malocclusion in growing patients may be associated with altered mandibular posture, occlusal instability, and adaptive changes in masticatory muscle function. This prospective, controlled, non-randomized longitudinal study evaluated changes in masseter and anterior temporalis muscle activity during Andresen functional appliance therapy and compared them with untreated Class I and Class II controls. Methods: Seventy children with skeletal and dental Class II malocclusion were treated with a customized Andresen appliance; 50 untreated Class II children and 30 untreated children with physiological Class I occlusion served as comparison groups. All participants were in mixed dentition and at cervical stage CS3 at baseline. Standardized bilateral sEMG recordings were obtained at T0, T1 (6 months), and T2 (12 months). Longitudinal sEMG outcomes were analyzed using mixed-design repeated-measures ANOVA, with time as the within-subject factor and group as the between-subject factor; prespecified T0-to-T2 contrasts were accompanied by Cohen\u2019s d effect sizes. Results: In the treated Class II cohort, IMPACT increased from 108.64 \u00b1 3.40 at T0 to 111.58 \u00b1 3.13 at T1 and 113.82 \u00b1 3.27 at T2 (within-group time effect p &lt; 0.001). ATTIV changed from \u22120.88 \u00b1 0.42 at T0 to +0.96 \u00b1 0.55 at T1 and +1.65 \u00b1 0.78 at T2 (p &lt; 0.001). In contrast, neither the untreated Class II nor the physiological Class I group showed statistically significant within-group time effects for IMPACT (p = 0.96 and p = 0.58, respectively) or ATTIV (p = 0.78 and p = 0.93, respectively). Significant T0-to-T2 differences between treated and untreated Class II groups were observed for ATTIV (p &lt; 0.001; d = +5.28) and IMPACT (p &lt; 0.001; d = +2.00). Conclusions: Andresen therapy was associated with statistically supported longitudinal differences in masticatory muscle recruitment compared with untreated Class II controls. The observed pattern may reflect treatment-associated neuromuscular adaptation; however, causal attribution remains limited by the non-randomized design, and the sEMG changes should be interpreted as modifications in muscle recruitment rather than as evidence of physiological normalization or clinical improvement.<\/jats:p>","DOI":"10.3390\/children13091209","type":"journal-article","created":{"date-parts":[[2026,9,7]],"date-time":"2026-09-07T13:53:28Z","timestamp":1788789208000},"page":"1209","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Changes in Masticatory Muscle Activity Following Interceptive Orthodontic Treatment in Children with Class II Malocclusion: A Multicenter Controlled Longitudinal Surface Electromyographic Study"],"prefix":"10.3390","volume":"13","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-3132-1750","authenticated-orcid":false,"given":"Lucia","family":"Giannini","sequence":"first","affiliation":[{"name":"Fondazione IRCCS C\u00e0 Granda Ospedale Maggiore Policlinico, 20122 Milan, Italy"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"conceptualization","vocabulary":"credit"},{"role":"writing-original-draft","vocabulary":"credit"},{"role":"writing-review-editing","vocabulary":"credit"},{"role":"formal-analysis","vocabulary":"credit"},{"role":"supervision","vocabulary":"credit"}]},{"ORCID":"https:\/\/orcid.org\/0009-0001-7757-4382","authenticated-orcid":false,"given":"Antonino","family":"Manti","sequence":"additional","affiliation":[{"name":"Department of Biomedical, Surgical and Dental Sciences, School of Dentistry, University of Milan, 20122 Milan, Italy"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"investigation","vocabulary":"credit"},{"role":"formal-analysis","vocabulary":"credit"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5947-8987","authenticated-orcid":false,"given":"Gianna","family":"Dipalma","sequence":"additional","affiliation":[{"name":"Department of Biomedical, Surgical and Dental Sciences, School of Dentistry, University of Milan, 20122 Milan, Italy"},{"name":"Department of Interdisciplinary Medicine, University of Bari Aldo Moro, 70121 Bari, Italy"},{"name":"Department of Life Science, Health and Health Professions, Link Campus University, 00165 Rome, Italy"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"formal-analysis","vocabulary":"credit"}]},{"given":"Angelo Michele","family":"Inchingolo","sequence":"additional","affiliation":[{"name":"Department of Biomedical, Surgical and Dental Sciences, School of Dentistry, University of Milan, 20122 Milan, Italy"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"data-curation","vocabulary":"credit"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5930-1698","authenticated-orcid":false,"given":"Cinzia","family":"Maspero","sequence":"additional","affiliation":[{"name":"Fondazione IRCCS C\u00e0 Granda Ospedale Maggiore Policlinico, 20122 Milan, Italy"},{"name":"Department of Biomedical, Surgical and Dental Sciences, School of Dentistry, University of Milan, 20122 Milan, Italy"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"conceptualization","vocabulary":"credit"},{"role":"methodology","vocabulary":"credit"},{"role":"writing-review-editing","vocabulary":"credit"},{"role":"supervision","vocabulary":"credit"}]}],"member":"1968","published-online":{"date-parts":[[2026,9,7]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"9","DOI":"10.1111\/j.1752-7325.2008.00089.x","article-title":"Objective, Subjective, and Self-Assessment of Preadolescent Orthodontic Treatment Need: A Function of Age, Gender, and Ethnic\/Racial Background?","volume":"69","author":"Christopherson","year":"2009","journal-title":"J. Public Health Dent."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"237","DOI":"10.1093\/ejo\/26.3.237","article-title":"Prevalence of Malocclusions in the Early Mixed Dentition and Orthodontic Treatment Need","volume":"26","author":"Tausche","year":"2004","journal-title":"Eur. J. Orthod."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"145","DOI":"10.1179\/bjo.7.3.145","article-title":"The Dentoalveolar Compensatory Mechanism: Background and Clinical Implications","volume":"7","author":"Solow","year":"1980","journal-title":"Br. J. Orthod."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"100","DOI":"10.2174\/1874210600903010100","article-title":"The aponeurotic tension model of craniofacial growth in man","volume":"3","author":"Standerwick","year":"2009","journal-title":"Open Dent. J."},{"key":"ref_5","first-page":"295","article-title":"Class II Division 1 Malocclusions: Comparisons between One- and Two-Step Treatment","volume":"19","author":"Maspero","year":"2018","journal-title":"Eur. J. Paediatr. Dent."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"405","DOI":"10.1016\/S0889-5406(99)70225-8","article-title":"Muscle Response to the Twin-Block Appliance: An Electromyographic Study of the Masseter and Anterior Temporal Muscles","volume":"116","author":"Aggarwal","year":"1999","journal-title":"Am. J. Orthod. Dentofac. Orthop."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"301","DOI":"10.1016\/0889-5406(90)70102-I","article-title":"Changes in Power Spectrum of Electromyograms of Masseter and Anterior Temporal Muscles during Functional Appliance Therapy in Children","volume":"97","author":"Yuen","year":"1990","journal-title":"Am. J. Orthod. Dentofac. Orthop."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"317","DOI":"10.1007\/s00056-022-00443-1","article-title":"Dentoskeletal effects of clear aligner vs twin block-a short-term study of functional appliances","volume":"85","author":"Lombardo","year":"2024","journal-title":"J. Orofac. Orthop."},{"key":"ref_9","first-page":"116","article-title":"Changes in Soft Tissue Profile and Electromyographic Activity after Activator Treatment","volume":"25","author":"Erdem","year":"2009","journal-title":"Aust. Orthod. J."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"620","DOI":"10.1016\/j.jelekin.2012.01.002","article-title":"Longitudinal evaluation of sEMG of masticatory muscles and kinematics of mandible changes in children treated for unilateral cross-bite","volume":"22","author":"Palma","year":"2012","journal-title":"J. Electromyogr. Kinesiol."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"451","DOI":"10.1016\/j.jdent.2004.02.009","article-title":"Maximal bite forces in healthy young adults as predicted by surface electromyography","volume":"32","author":"Ferrario","year":"2004","journal-title":"J. Dent."},{"key":"ref_12","first-page":"511","article-title":"Coordinated Electromyographic Activity of the Human Masseter and Temporalis Muscles","volume":"23","author":"Ferrario","year":"1996","journal-title":"J. Oral Rehabil."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"271","DOI":"10.1111\/j.1365-2842.1993.tb01609.x","article-title":"Electromyographic Activity of Human Masticatory Muscle in Normal Young People. Statistical Evaluation of Reference Values for Clinical Applications","volume":"20","author":"Ferrario","year":"1993","journal-title":"J. Oral Rehabil."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"96","DOI":"10.1093\/ejo\/cjq169","article-title":"Influence of Pre-Orthodontic Trainer Treatment on the Perioral and Masticatory Muscles in Patients with Class II Division 1 Malocclusion","volume":"34","author":"Uysal","year":"2012","journal-title":"Eur. J. Orthod."},{"key":"ref_15","doi-asserted-by":"crossref","unstructured":"Szyszka-Sommerfeld, L., Syci\u0144ska-Dziarnowska, M., Cernera, M., Esposito, L., Wo\u017aniak, K., and Spagnuolo, G. (2024). Electromyographic Assessment of Muscle Activity in Children Undergoing Orthodontic Treatment-A Systematic Review. J. Clin. Med., 13.","DOI":"10.3390\/jcm13072051"},{"key":"ref_16","first-page":"124","article-title":"Upper airway obstuction in class II patients. Effects of Andresen activator on the anatomy of pharingeal airway passage. Cone beam evalution","volume":"17","author":"Maspero","year":"2015","journal-title":"Stomatologija"},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"172","DOI":"10.1093\/ejo\/8.3.172","article-title":"Function of Masticatory Muscles during the Initial Phase of Activator Treatment","volume":"8","author":"Ingervall","year":"1986","journal-title":"Eur. J. Orthod."},{"key":"ref_18","first-page":"327","article-title":"Effects of an Activator on the Masseter and Anterior Temporal Muscle Activities in Class II Malocclusions","volume":"23","author":"Uner","year":"1999","journal-title":"J. Clin. Pediatr. Dent."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"241","DOI":"10.3109\/00016356609026128","article-title":"Muscle Activity Related to Activator and Intermaxillary Traction in Angle Class II, Division 1 Malocclusions. An Electromyographic Study of the Temporal, Masseter and Suprahyoid Muscles","volume":"24","author":"Thilander","year":"1966","journal-title":"Acta Odontol. Scand."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"222","DOI":"10.1016\/S0889-5406(05)81599-9","article-title":"Effect of Functional Appliances on Jaw Muscle Activity","volume":"98","author":"Sessle","year":"1990","journal-title":"Am. J. Orthod. Dentofac. Orthop."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"88","DOI":"10.1016\/0002-9416(78)90048-9","article-title":"Early and Late Electromyographic Response to Treatment with Activators","volume":"74","author":"Ahlgren","year":"1978","journal-title":"Am. J. Orthod."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"169","DOI":"10.1016\/S0889-5406(94)70113-X","article-title":"Orthodontic Forces Exerted by Activators with Varying Construction Bite Heights","volume":"105","author":"Noro","year":"1994","journal-title":"Am. J. Orthod. Dentofac. Orthop."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"179","DOI":"10.1067\/mod.2000.104809","article-title":"Effects of Spring-Loaded Posterior Bite-Block Appliance on Masticatory Muscles","volume":"118","author":"Akkaya","year":"2000","journal-title":"Am. J. Orthod. Dentofac. Orthop."},{"key":"ref_24","first-page":"608","article-title":"An Adolescent Case of Anterior Open Bite with Masticatory Muscle Dysfunction","volume":"73","author":"Tanaka","year":"2003","journal-title":"Angle Orthod."},{"key":"ref_25","first-page":"E85","article-title":"Muscular Response to Functional Treatment of Skeletal Open-Bite and Deep-Bite Cases: An Electromyographic Study","volume":"11","author":"Uslu","year":"2010","journal-title":"World J. Orthod."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"355","DOI":"10.1016\/j.ajodo.2007.08.027","article-title":"Electromyographic Evaluation in Children Having Rapid Maxillary Expansion","volume":"136","author":"Hallak","year":"2009","journal-title":"Am. J. Orthod. Dentofac. Orthop."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"815","DOI":"10.1016\/j.ajodo.2006.07.028","article-title":"Muscular and Condylar Response to Rapid Maxillary Expansion. Part 1: Electromyographic Study of Anterior Temporal and Superficial Masseter Muscles","volume":"133","author":"Arat","year":"2008","journal-title":"Am. J. Orthod. Dentofac. Orthop."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"717","DOI":"10.3390\/clockssleep5040047","article-title":"Diagnostic Accuracy of a Portable Electromyography and Electrocardiography Device to Measure Sleep Bruxism in a Sleep Apnea Population: A Comparative Study","volume":"5","year":"2023","journal-title":"Clocks Sleep"},{"key":"ref_29","doi-asserted-by":"crossref","unstructured":"Giannini, L., Gigante, L., Di Iasio, G., Cattaneo, G., and Maspero, C. (2026). Neuromuscular Evaluation in Orthodontic-Surgical Treatment: A Comparison Between Monomaxillary and Bimaxillary Surgery. Bioengineering, 13.","DOI":"10.3390\/bioengineering13010123"},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"226","DOI":"10.1016\/j.pio.2012.04.003","article-title":"Orthodontic-Surgical Treatment: Neuromuscular Evaluation in Skeletal Class II and Class III Patients","volume":"13","author":"Farronato","year":"2012","journal-title":"Prog. Orthod."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"41","DOI":"10.1186\/2196-1042-14-41","article-title":"Orthodontic-Surgical Treatment: Neuromuscular Evaluation in Open and Deep Skeletal Bite Patients","volume":"14","author":"Farronato","year":"2013","journal-title":"Prog. Orthod."},{"key":"ref_32","first-page":"284","article-title":"Occlusal Control of Mandibular Elevator Muscles","volume":"100","author":"Bakke","year":"1992","journal-title":"Scand. J. Dent. Res."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"718","DOI":"10.1016\/0022-3913(84)90149-5","article-title":"Relationship between Occlusal Contacts and Jaw-Closing Muscle Activity during Tooth Clenching: Part 1","volume":"52","author":"MacDonald","year":"1984","journal-title":"J. Prosthet. Dent."},{"key":"ref_34","first-page":"125","article-title":"Evaluation of the Use of Surface Electromyography in the Diagnosis, Documentation, and Treatment of Dental Patients","volume":"3","author":"Lund","year":"1989","journal-title":"J. Craniomandib. Disord."},{"key":"ref_35","first-page":"187","article-title":"The Effect of Occlusal Splints on the Treatment of Temporomandibular Disorders: A Computerized Electromyographic Study of Masseter and Anterior Temporalis Muscles","volume":"42","author":"Landulpho","year":"2002","journal-title":"Electromyogr. Clin. Neurophysiol."},{"key":"ref_36","first-page":"262","article-title":"Comparative Electromyographic Study of Bite Plates and Stabilization Splints","volume":"93","author":"Haraldson","year":"1985","journal-title":"Scand. J. Dent. Res."},{"key":"ref_37","first-page":"1","article-title":"Conservative Treatment of Mandibular Dysfunction. Clinical, Experimental and Electromyographic Studies of Biofeedback and Occlusal Appliances","volume":"24","year":"1984","journal-title":"Swed. Dent. J. Suppl."},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"345","DOI":"10.1177\/10454411980090030701","article-title":"Oral Splints: The Crutches for Temporomandibular Disorders and Bruxism?","volume":"9","author":"Dao","year":"1998","journal-title":"Crit. Rev. Oral Biol. Med."},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"206","DOI":"10.1179\/crn.2007.032","article-title":"The orthodontic treatment of TMD patients: EMG effects of a functional appliance","volume":"25","author":"Castroflorio","year":"2007","journal-title":"CRANIO\u00ae"},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"631","DOI":"10.1111\/j.1365-2842.2007.01769.x","article-title":"Review of Clinical EMG Studies Related to Muscle and Occlusal Factors in Healthy and TMD Subjects","volume":"34","author":"Suvinenm","year":"2007","journal-title":"J. Oral Rehabil."},{"key":"ref_41","first-page":"131","article-title":"Juvenile Idiopathic Arthritis with temporomandibular joint involvement: Functional treatment","volume":"12","author":"Farronato","year":"2011","journal-title":"Eur. J. Paediatr. Dent."},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"380","DOI":"10.17796\/jcpd.38.4.2vh1603n62878673","article-title":"Electromyographic Muscular Activity Improvement in Class II Patients Treated with the Pre-Orthodontic Trainer","volume":"38","author":"Satygo","year":"2014","journal-title":"J. Clin. Pediatr. Dent."},{"key":"ref_43","doi-asserted-by":"crossref","first-page":"246","DOI":"10.12659\/MSM.893111","article-title":"Impact of Functional Appliances on Muscle Activity: A Surface Electromyography Study in Children","volume":"21","year":"2015","journal-title":"Med. Sci. Monit."},{"key":"ref_44","doi-asserted-by":"crossref","first-page":"665","DOI":"10.1016\/j.jelekin.2011.03.005","article-title":"Effects of Interceptive Orthodontics on Orbicular Muscle Activity: A Surface Electromyographic Study in Children","volume":"21","author":"Saccucci","year":"2011","journal-title":"J. Electromyogr. Kinesiol."},{"key":"ref_45","doi-asserted-by":"crossref","first-page":"1116","DOI":"10.2298\/VSP130901058P","article-title":"Examination of the Bioelectrical Activity of the Masticatory Muscles during Angle\u2019s Class II Division 2 Therapy with an Activator","volume":"71","author":"Vujkov","year":"2014","journal-title":"Vojnosanit. Pregl."},{"key":"ref_46","first-page":"177","article-title":"An Electromyographic Investigation of the First Six Months of Progressive Mandibular Advancement of the Herbst Appliance in Adolescents","volume":"71","author":"Leung","year":"2001","journal-title":"Angle Orthod."},{"key":"ref_47","doi-asserted-by":"crossref","first-page":"18","DOI":"10.5357\/koubyou.63.18","article-title":"An Electromyographic Study on Functional Adaptations Associated with Herbst Appliance","volume":"63","author":"Hiyama","year":"1996","journal-title":"Kokubyo Gakkai Zasshi"},{"key":"ref_48","doi-asserted-by":"crossref","first-page":"331","DOI":"10.17796\/jcpd.35.3.5v86511u4h1mw144","article-title":"Muscle Response during Treatment of Class II Division 1 Malocclusion with Forsus Fatigue Resistant Device","volume":"35","author":"Sood","year":"2011","journal-title":"J. Clin. Pediatr. Dent."}],"container-title":["Children"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2227-9067\/13\/9\/1209\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,9,7]],"date-time":"2026-09-07T14:19:02Z","timestamp":1788790742000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2227-9067\/13\/9\/1209"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,9,7]]},"references-count":48,"journal-issue":{"issue":"9","published-online":{"date-parts":[[2026,9]]}},"alternative-id":["children13091209"],"URL":"https:\/\/doi.org\/10.3390\/children13091209","relation":{},"ISSN":["2227-9067"],"issn-type":[{"value":"2227-9067","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,9,7]]}}}