{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,3,26]],"date-time":"2026-03-26T02:51:29Z","timestamp":1774493489587,"version":"3.50.1"},"reference-count":54,"publisher":"MDPI AG","issue":"3","license":[{"start":{"date-parts":[[2025,2,24]],"date-time":"2025-02-24T00:00:00Z","timestamp":1740355200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Open-Access-Publication funds of the J. W. Goethe University in Frankfurt am Main"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Dentistry Journal"],"abstract":"<jats:p>Background: This retrospective study aimed to analyze the frequency and extent of apical root resorptions (EARR) during orthodontic treatment in the upper and lower incisors, as well as lower molars, using orthopantomograms (OPG). Potential influencing factors such as age, gender, root shape, type of orthodontic appliance, and treatment duration were examined as well. Methods: A total of 57 patients who completed their treatment at the orthodontic department of the Goethe University of Frankfurt between 2011 and 2018 were included in the study. These patients had a combined total of 570 teeth, which were divided into two groups. Group 1 consisted of 20 patients (average age at T0: 10.1 \u00b1 1.2 years old) received a one-phase fixed orthodontic treatment using passive self-ligating Damon bracket system (average duration of 2.1 years \u00b1 6 months), while group 2 consisted of 37 patients (average age at T0: 12.4 \u00b1 2.8 years old) underwent a two-phase therapy, which involved a phase-one functional therapy (average duration of 1.7 years \u00b1 6 months) prior to the phase-two fixed orthodontic treatment with the Damon system (average duration of 1.5 \u00b1 4 months) with a total treatment time of 3.2 years \u00b1 7 months. To determine the extent of post-treatment root resorption of the upper and lower incisors, as well as the first lower molars, crown\u2013root ratio was calculated for each tooth using the pre- and post-treatment OPGs. Additionally, each tooth was assigned a degree of resorption according to the Levander and Malmgren classification. The inter-group comparisons were conducted using the Wilcoxon Mann\u2013Whitney U test. Spearman\u2019s correlation analysis was used to assess the relationship between age, treatment duration, and EARR. The association between gender, root morphology, and EARR was evaluated using the Wilcoxon Mann\u2013Whitney U test. For nominally scaled variables, the Chi-square test was used. The statistical significance was set at p &lt; 0.05. Results: No statistically significant differences were seen between groups 1 and 2 regarding the degree of root resorption (p = 0.89). The study found that the average root resorption for all examined teeth was \u22125.14%, indicating a slight reduction in the length of the tooth roots after orthodontic treatment. However, no significant differences were observed concerning gender, age, type of orthodontic appliance or treatment duration. Comparisons between upper and lower jaws also did not yield statistically significant differences. The majority of teeth in the study exhibited a normal root shape. The short root length and a pipette formed roots were significantly associated with a higher risk of root resorption (p = 0.001). Conclusions: The study\u2019s findings suggest that the two-phase orthodontic treatment does not increase the risk of EARR compared to one-phase therapy significantly. Some degree of root resorption occurred as a result of orthodontic treatment in both groups. Notably, abnormal root forms were identified as influential factors that could help predict the likelihood of root resorption following orthodontic treatment.<\/jats:p>","DOI":"10.3390\/dj13030095","type":"journal-article","created":{"date-parts":[[2025,2,25]],"date-time":"2025-02-25T12:01:17Z","timestamp":1740484877000},"page":"95","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":2,"title":["Does the Phase-One Functional Therapy Increase the Risk of an External Apical Root Resorption Following the Phase-Two Fixed Orthodontic Treatment? A Pilot Study"],"prefix":"10.3390","volume":"13","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-5720-116X","authenticated-orcid":false,"given":"Sara","family":"Eslami","sequence":"first","affiliation":[{"name":"Department of Orthodontics, Johann-Wolfgang Goethe University, 60596 Frankfurt am Main, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0009-0006-7231-553X","authenticated-orcid":false,"given":"Jakob","family":"Stuhlfelder","sequence":"additional","affiliation":[{"name":"Department of Orthodontics, Johann-Wolfgang Goethe University, 60596 Frankfurt am Main, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Suh-In","family":"Rhie","sequence":"additional","affiliation":[{"name":"MIRKHYL DENTALWELT, Bad Vilbel Frankfurter Stra\u00dfe 47, Bad Vilbel, 61118 Frankfurt am Main, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Sarah","family":"B\u00fchling","sequence":"additional","affiliation":[{"name":"Department of Orthodontics, Johann-Wolfgang Goethe University, 60596 Frankfurt am Main, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Mauricio Gonzalez","family":"Balut","sequence":"additional","affiliation":[{"name":"Department of Orthodontics and Dentofacial Orthopedics, Loma Linda University, San Bernadino, CA 92408, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7174-7596","authenticated-orcid":false,"given":"Ludovica","family":"Nucci","sequence":"additional","affiliation":[{"name":"Multidisciplinary Department of Medical-Surgical and Dental Specialties, University of Campania Luigi Vanvitelli, 80131 Naples, Italy"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-8841-0447","authenticated-orcid":false,"given":"Abdolreza","family":"Jamilian","sequence":"additional","affiliation":[{"name":"Department of Orthodontics, Dental School, Tehran Islamic Azad University of Medical Sciences, Tehran 19395-1495, Iran"},{"name":"City of London Dental School, University of Greater Manchester, Bolton BL3 5AB, UK"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-8319-7261","authenticated-orcid":false,"given":"Babak","family":"Sayahpour","sequence":"additional","affiliation":[{"name":"Department of Orthodontics, Johann-Wolfgang Goethe University, 60596 Frankfurt am Main, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2025,2,24]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"183","DOI":"10.1053\/sodo.2000.8084","article-title":"Root resorption during orthodontic therapy","volume":"6","author":"Harris","year":"2000","journal-title":"Semin. Orthod."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1159\/000351894","article-title":"Periodontal Ligament and Alveolar Bone in Health and Adaptation: Tooth Movement","volume":"18","author":"Jiang","year":"2016","journal-title":"Front. Oral Biol."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"297","DOI":"10.11005\/jbm.2023.30.4.297","article-title":"Mechanisms of Osteoclastogenesis in Orthodontic Tooth Movement and Orthodontically Induced Tooth Root Resorption","volume":"30","author":"Nakai","year":"2023","journal-title":"J. Bone Metab."},{"key":"ref_4","first-page":"174","article-title":"Impact of Treatment with Full-Fixed Orthodontic Appliances on the Periodontium and the Composition of the Subgingival Microbiota","volume":"22","author":"Lemos","year":"2020","journal-title":"J. Int. Acad. Periodontol."},{"key":"ref_5","doi-asserted-by":"crossref","unstructured":"Yamaguchi, M., and Fukasawa, S. (2021). Is Inflammation a Friend or Foe for Orthodontic Treatment?: Inflammation in Orthodontically Induced Inflammatory Root Resorption and Accelerating Tooth Movement. Int. J. Mol. Sci., 22.","DOI":"10.3390\/ijms22052388"},{"key":"ref_6","first-page":"175","article-title":"Orthodontically induced inflammatory root resorption. Part I: The basic science aspects","volume":"72","author":"Brezniak","year":"2002","journal-title":"Angle Orthod."},{"key":"ref_7","first-page":"180","article-title":"Orthodontically induced inflammatory root resorption. Part II: The clinical aspects","volume":"72","author":"Brezniak","year":"2002","journal-title":"Angle Orthod."},{"key":"ref_8","first-page":"19","article-title":"Extreme root resorption associated with induced tooth movement: A protocol for clinical management","volume":"19","author":"Consolaro","year":"2014","journal-title":"Dent. Press J. Orthod."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"5","DOI":"10.1016\/j.ajodo.2017.11.005","article-title":"External apical root resorption","volume":"153","author":"Brezniak","year":"2018","journal-title":"Am. J. Orthod. Dentofac. Orthop."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"30","DOI":"10.1093\/ejo\/10.1.30","article-title":"Evaluation of the risk of root resorption during orthodontic treatment: A study of upper incisors","volume":"10","author":"Levander","year":"1988","journal-title":"Eur. J. Orthod."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"48","DOI":"10.1016\/j.jds.2017.09.007","article-title":"External apical root resorption in non-extraction cases after clear aligner therapy or fixed orthodontic treatment","volume":"13","author":"Yi","year":"2018","journal-title":"J. Dent. Sci."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"35","DOI":"10.1016\/S0889-5406(05)81678-6","article-title":"Patient characteristics and treatment variables associated with apical root resorption during orthodontic treatment","volume":"199","author":"Linge","year":"1991","journal-title":"Am. J. Orthod. Dentofac. Orthop."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"93","DOI":"10.1093\/ejo\/17.2.93","article-title":"Prevalence and severity of apical root resorption of maxillary anterior teeth in adult orthodontic patients","volume":"17","author":"Mirabella","year":"1995","journal-title":"Eur. J. Orthod."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"505","DOI":"10.1067\/mod.2001.113409","article-title":"Predicting preventing root resorption: Part, I. Diagnostic factors","volume":"119","author":"Sameshima","year":"2001","journal-title":"Am. J. Orthod. Dentofac. Orthop."},{"key":"ref_15","first-page":"76","article-title":"Factors related to apical root resorption of maxillary incisors in orthodontic patients","volume":"8","author":"Nigul","year":"2006","journal-title":"Stomatologija"},{"key":"ref_16","first-page":"196","article-title":"Apical root resorption during orthodontic treatment","volume":"50","author":"Goz","year":"1989","journal-title":"J. Orofac. Orthop.\/Fortschritte Der Kieferorthop\u00e4die"},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"17","DOI":"10.5624\/isd.2011.41.1.17","article-title":"External root resorption after orthodontic treatment: A study of contributing factors","volume":"41","author":"Jung","year":"2011","journal-title":"Imaging Sci. Dent."},{"key":"ref_18","first-page":"227","article-title":"External apical root resorption following orthodontic treatment","volume":"70","author":"McNab","year":"2000","journal-title":"Angle Orthod."},{"key":"ref_19","first-page":"919","article-title":"Apical root resorption six and 12 months after initiation of fixed orthodontic appliance therapy","volume":"75","author":"Artun","year":"2005","journal-title":"Angle Orthod."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"48","DOI":"10.1016\/S0889-5406(95)70065-X","article-title":"Risk factors for apical root resorption of maxillary anterior teeth in adult orthodontic patients","volume":"108","author":"Mirabella","year":"1995","journal-title":"Am. J. Orthod. Dentofac. Orthop."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"462","DOI":"10.1016\/j.ajodo.2009.06.021","article-title":"Root resorption associated with orthodontic tooth movement: A systematic review","volume":"137","author":"Weltman","year":"2010","journal-title":"Am. J. Orthod. Dentofac. Orthop."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"252","DOI":"10.1016\/0889-5406(87)90455-0","article-title":"Orthodontic relapse, apical root resorption, and crestal alveolar bone levels","volume":"91","author":"Sharpe","year":"1987","journal-title":"Am. J. Orthod. Dentofac. Orthop."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"60","DOI":"10.1016\/j.ajodo.2021.08.025","article-title":"Three-dimensional analysis of root changes after orthodontic treatment for patients at different stages of root development","volume":"163","author":"Wan","year":"2023","journal-title":"Am. J. Orthod. Dentofac. Orthop."},{"key":"ref_24","first-page":"30","article-title":"Apical root resorption in patients treated with comprehensive orthodontics","volume":"81","author":"Harris","year":"2001","journal-title":"J. Tenn. Dent. Assoc."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"675","DOI":"10.1007\/s00592-021-01838-z","article-title":"Periodontitis, age-related diseases and diabetes in an endocrinological outpatient setting (PARADIES): A cross-sectional analysis on predictive factors for periodontitis in a German outpatient facility","volume":"59","author":"Kabisch","year":"2022","journal-title":"Acta Diabetol."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"173","DOI":"10.1093\/ejo\/5.3.173","article-title":"Apical root resorption in upper anterior teeth","volume":"5","author":"Linge","year":"1983","journal-title":"Eur. J. Orthod."},{"key":"ref_27","first-page":"68","article-title":"Initial tissue behavior during apical root resorption","volume":"44","author":"Reitan","year":"1974","journal-title":"Angle Orthod."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"66","DOI":"10.14219\/jada.archive.2011.0030","article-title":"Apical root resorption is associated with comprehensive orthodontic treatment but not clearly dependent on prior tooth characteristics or orthodontic techniques","volume":"142","author":"Zahrowski","year":"2011","journal-title":"J. Am. Dent. Assoc."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"321","DOI":"10.1016\/S0889-5406(96)80017-5","article-title":"Levels of root resorption associated with continuous arch and sectional arch mechanics","volume":"110","author":"Alexander","year":"1996","journal-title":"Am. J. Orthod. Dentofac. Orthop."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"14A","DOI":"10.1016\/S0889-5406(00)70129-6","article-title":"Revisiting root resorption","volume":"118","author":"Artun","year":"2000","journal-title":"Am. J. Orthod. Dentofac. Orthop."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"91","DOI":"10.14712\/18059694.2017.117","article-title":"Root resorption in relation to orthodontic tooth movement","volume":"49","author":"Ramanathan","year":"2006","journal-title":"Acta Medica (Hradec Kral.)"},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"408","DOI":"10.1093\/ejo\/cjm016","article-title":"Apical root resorption after orthodontic treatment\u2014A retrospective study","volume":"29","author":"Apajalahti","year":"2007","journal-title":"Eur. J. Orthod."},{"key":"ref_33","first-page":"31","article-title":"Root resorption and orthodontic treatment. Review of the literature","volume":"56","author":"Pizzo","year":"2007","journal-title":"Minerva Stomatol."},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"e279","DOI":"10.1016\/j.ajodo.2010.07.021","article-title":"Physical properties of root cementum: Part 16. Comparisons of root resorption and resorption craters after the application of light and heavy continuous and controlled orthodontic forces for 4, 8, and 12 weeks","volume":"139","author":"Paetyangkul","year":"2011","journal-title":"Am. J. Orthod. Dentofac. Orthop."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"427","DOI":"10.1093\/ejo\/20.4.427","article-title":"Apical root resorption during orthodontic treatment of patients with multiple aplasia: A study of maxillary incisors","volume":"20","author":"Levander","year":"1998","journal-title":"Eur. J. Orthod."},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"480","DOI":"10.2319\/061311-390.1","article-title":"Apical root resorption during orthodontic treatment. A prospective study using cone beam CT","volume":"82","author":"Lund","year":"2012","journal-title":"Angle Orthod."},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"434","DOI":"10.1007\/s00056-003-0243-5","article-title":"Apical root resorption after lingual orthodontic therapy","volume":"64","author":"Fritz","year":"2003","journal-title":"J. Orofac. Orthop."},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"350","DOI":"10.1016\/S0889-5406(94)70129-6","article-title":"Apical root resorption in orthodontically treated subjects: Analysis of edgewise and light wire mechanics","volume":"105","author":"Beck","year":"1994","journal-title":"Am. J. Orthod. Dentofac. Orthop."},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"345","DOI":"10.1016\/S0889-5406(94)70128-8","article-title":"A radiographic study of posterior apical root resorption in orthodontic patients","volume":"105","author":"Hendrix","year":"1994","journal-title":"Am. J. Orthod. Dentofac. Orthop."},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"262","DOI":"10.1067\/mod.2000.99136","article-title":"A radiographic comparison of apical root resorption after orthodontic treatment with 3 different fixed appliance techniques","volume":"118","author":"Janson","year":"2000","journal-title":"Am. J. Orthod. Dentofac. Orthop."},{"key":"ref_41","first-page":"332","article-title":"Clinic study of root resorption caused by edgewise appliance combined with flat bite plate treatment","volume":"24","author":"Yuan","year":"2006","journal-title":"Hua Xi Kou Qiang Yi Xue Za Zhi"},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"151","DOI":"10.1016\/S0889-5406(03)00166-5","article-title":"External apical root resorption in Class II malocclusion: A retrospective review of 1- versus 2-phase treatment","volume":"124","author":"Brin","year":"2003","journal-title":"Am. J. Orthod. Dentofac. Orthop."},{"key":"ref_43","doi-asserted-by":"crossref","first-page":"1027","DOI":"10.1902\/jop.2004.75.7.1027","article-title":"Root resorption in chronic periodontitis: A morphometrical study","volume":"75","year":"2004","journal-title":"J. Periodontol."},{"key":"ref_44","first-page":"257","article-title":"Orthodontically induced root resorption correlated with morphological characteristics","volume":"50","author":"Preoteasa","year":"2009","journal-title":"Rom. J. Morphol. Embryol."},{"key":"ref_45","doi-asserted-by":"crossref","first-page":"646","DOI":"10.1016\/j.ajodo.2007.01.032","article-title":"External apical root resorption in patients treated with conventional and self-ligating brackets","volume":"134","author":"Pandis","year":"2008","journal-title":"Am. J. Orthod. Dentofac. Orthop."},{"key":"ref_46","first-page":"231","article-title":"A study of root resorption in treated Class II, Division I malocclusions","volume":"39","author":"DeShields","year":"1969","journal-title":"Angle Orthod."},{"key":"ref_47","doi-asserted-by":"crossref","first-page":"208","DOI":"10.1016\/0889-5406(89)90051-6","article-title":"Labial root torque: Effect on the maxilla and incisor root apex","volume":"95","author":"Goldin","year":"1989","journal-title":"Am. J. Orthod. Dentofac. Orthop."},{"key":"ref_48","doi-asserted-by":"crossref","first-page":"83","DOI":"10.1016\/S0002-9416(68)90292-3","article-title":"The effect of mechanical forces upon the mandibular buccal segments during orthodontic treatment","volume":"54","author":"Dougherty","year":"1968","journal-title":"Am. J. Orthod."},{"key":"ref_49","doi-asserted-by":"crossref","first-page":"522","DOI":"10.1016\/0002-9416(75)90298-5","article-title":"Possible etiologic factors in external root resorption","volume":"67","author":"Newman","year":"1975","journal-title":"Am. J. Orthod."},{"key":"ref_50","doi-asserted-by":"crossref","first-page":"311","DOI":"10.1016\/S0889-5406(96)80016-3","article-title":"Apical root resorption in orthodontically treated adults","volume":"110","author":"Baumrind","year":"1996","journal-title":"Am. J. Orthod. Dentofac. Orthop."},{"key":"ref_51","doi-asserted-by":"crossref","first-page":"25","DOI":"10.1093\/ejo\/17.1.25","article-title":"Morphological characteristics of dentitions developing excessive root resorption during orthodontic treatment","volume":"17","author":"Kjaer","year":"1995","journal-title":"Eur. J. Orthod."},{"key":"ref_52","doi-asserted-by":"crossref","first-page":"187","DOI":"10.1016\/S0889-5406(99)70217-9","article-title":"Are dental anomalies risk factors for apical root resorption in orthodontic patients?","volume":"116","author":"Lee","year":"1999","journal-title":"Am. J. Orthod. Dentofac. Orthop."},{"key":"ref_53","doi-asserted-by":"crossref","first-page":"571","DOI":"10.1093\/ejo\/cjr056","article-title":"Relationship between dental anomalies and orthodontic root resorption of upper incisors","volume":"34","author":"Aartman","year":"2012","journal-title":"Eur. J. Orthod."},{"key":"ref_54","first-page":"e31219","article-title":"Comparative Evaluation of Orthodontically-Induced Root Resorption Using Cone Beam Computed Tomography (CBCT) and Orthopantomogram (OPG) During En-Masse Retraction of Maxillary Anterior Teeth","volume":"14","author":"Alassiry","year":"2022","journal-title":"Cureus"}],"container-title":["Dentistry Journal"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2304-6767\/13\/3\/95\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,9]],"date-time":"2025-10-09T16:41:19Z","timestamp":1760028079000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2304-6767\/13\/3\/95"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2025,2,24]]},"references-count":54,"journal-issue":{"issue":"3","published-online":{"date-parts":[[2025,3]]}},"alternative-id":["dj13030095"],"URL":"https:\/\/doi.org\/10.3390\/dj13030095","relation":{},"ISSN":["2304-6767"],"issn-type":[{"value":"2304-6767","type":"electronic"}],"subject":[],"published":{"date-parts":[[2025,2,24]]}}}