Risk factors for open gingival embrasures after clear aligners treatment: A retrospective study

Risk factors for open gingival embrasures after clear aligners treatment: A retrospective study | 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 Risk factors for open gingival embrasures after clear aligners treatment: A retrospective study Wenjie Cui, Yibai Liu, Yang Zhao, Lang Lei, Houxuan Li This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-5762697/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 11 Apr, 2025 Read the published version in BMC Oral Health → Version 1 posted 10 You are reading this latest preprint version Abstract Background To explore the incidence and risk factors of open gingival embrasures (OGEs) in the front region of adult none-extraction cases with clear aligner treatment (CAT). Methods Eighty-two adult patients with non-extraction and CAT were included in this retrospective study. A total of 820 tooth sites were assessed for OGEs in intraoral photographs. These sites were categorized into nonoccurrence group and occurrence group. The parameters – including crown shape, root angulation, distance between cementoenamel junction, and distance from interproximal contact point (ICP) to alveolar bone crest (ABC) – were compared between occurrence group and nonoccurrence group using independent t-test and were further analyzed based on the severity. Logistic regression analysis was used to determine the significant risk factors of OGEs. Results The overall incidence of OGEs was 13.4% in the maxilla and 30.7% in the mandible. The highest incidence was found between the mandibular central incisors, standing at 39.02%. Age, mandibular crowding, distance between adjacent maxillary teeth at the cementoenamel junction and distance from ICP to ABC in the maxilla and mandible have significant correlation with the occurrence of OGEs ( P <0.05). The tooth shape as well as the distance from ICP to ABC were correlated with the severity of OGEs between mandibular central incisors ( P <0.05). Conclusions OGE is a common complication after CAT, adversely affecting the smiling esthetics. Clinicians should be well aware of risk factors, such as age, degree of dental crowding, and the distance from the ICP to ABC. Open gingival embrasures black triangles Orthodontic treatment Clear aligners Figures Figure 1 Figure 2 Figure 3 Figure 4 Introduction Open gingival embrasures (OGEs), also called black triangles, are the gap below proximal contacts and not filled with the papilla. A high incidence of OGEs was observed in adult orthodontic patients, ranging from 38 to 43.7%[ 1 ]. The presence of the OGEs greatly impairs smiling esthetics, and it is the third most unpleasant aesthetic issue after dental caries and crown margins[ 2 ]. In addition, they may affect pronunciation, and bring periodontal problems, such as food retention and biofilm accumulation[ 1 ]. Multiple factors contribute to the occurrence of OGEs. Most notably, alveolar bone resorption and patient's thin-scalloped periodontal biotype are major risk factor of OGEs. OGE is one of the most complained issue in the adult orthodontics. Patient age, the degree of dentition crowding, the distance from the proximal contact point to the crest of the bone, tooth morphology, and the direction of gingival movement during orthodontic tooth movement with fixed appliances can also increase the likelihood of OGEs[ 1 , 3 , 4 ]. Despite its well acceptance of clear aligner therapy(CAT) in adult patients due to its less interference on facial esthetics, OGEs are commonly present after CAT. The incidence rate stands at 25.7% and 40.3% between the two central incisor of the maxilla and mandible, respectively[ 5 ]. Several modalities have been proposed to reduce the adverse effect of OGEs, such as adjustment of the tooth axial inclination, interproximal enamel reduction (IPR) to modify the crown shape, or restorative procedures using resin or veneers[ 6 ]. However, the potential risk factors for the occurrence of OGEs during CAT are less clear. Currently, researches on OGEs in the context of CAT are very limited. One study explored the impact of the number of attachments and IPR on the occurrence of OGE between central incisors, finding that the number of attachments affects the incidence of OGE, and IPR may influence the severity of OGE[ 5 ]. But the relationship between patient-related factors such as age, periodontal phenotype, tooth shape, and degree of dental crowding with OGEs remains unclear. Therefore, further research on the relationship between these factors and the occurrence of OGEs is essential. Therefore, the purposes of this study were (1) to determine the presence of OGEs between anterior teeth in adult none-extraction cases with CAT, and (2) to explore the potential factors that affect the occurrence of the OGEs. Methods Subjects This retrospective study was approved by the Ethical Committee of Nanjing Stomatological Hospital, Affiliated Hospital of Medical School, Institute of Stomatology, Nanjing University, Nanjing, China (NJSH-2023NL-036). All patients signed the informed consent. Eighty-two adult patients (13 males, 69 females; average age 25.82 ± 5.27 years old) were selected from the Orthodontics Department of XX Hospital from September 2017 to December 2021. Patients were selected based on the following criteria: (1) Age > 18 years old; (2) Patients underwent non-extraction clear aligners treatment; (3) Complete initial (T0) and final (T1) orthodontic records, including frontal intraoral photos, panoramic radiographs and study models; (4) Patients who do not have a long-term history of medication or have used medication that alters gingiva condition; (5) Patients without systemic diseases. The exclusion criteria were as follows: (1) Missing one or several anterior teeth; (2) History of periodontal disease; (3) Unclear or containing foreign objects such as saliva, food residue, etc. in the front photos; (4) Having a history of periodontal surgery in the upper and lower anterior teeth areas; (5) Women who are pregnant, breastfeeding, or planning to become pregnant during orthodontic treatment; (6) Smoking history. The average treatment time was 26.63 ± 6.70 months, and regular oral hygiene instruction was provided during the treatment period. Classification of the OGEs incidence and severity Based on frontal and lateral intraoral photos taken before and one week after orthodontic treatment, the incidence and severity of the OGEs in the upper and lower anterior teeth areas of patients were statistically analyzed. The incidence and severity were evaluated jointly by one orthodontist and two periodontists. Patients would only be included in the study if the evaluation results of at least two doctors were consistent. Based on the assessment results, the tooth sites were divided into occurrence and non-occurrence groups. Based on the Jemt index (Fig. 1 ), the occurrence group was categorized into three sub-groups: mild, moderate, and severe[ 4 , 7 ]. The patient's intraoral photographs were taken by a dedicated photographer from our orthodontic department using the same model of equipment. Measurement of root angle, distance between cementoenamel junctions (CEJs) and distance from proximal contact point (ICP) to alveolar bone crest (ABC) on panoramic radiographs All variables from panoramic radiographs were measured by using ImageJ software (Version 1.54g; National Institutes of Health, USA), including: (1) distance between the mesial cementoenamel junctions of the two adjacent teeth (Fig. 2 ); (2) distance between the interproximal contact point and alveolar bone crest before (T0), after (T1) and during treatment (△=T1-T0) (Fig. 3 ); (3) the angle between the long axes of adjacent anterior teeth at T1(Fig. 3 ). This angle was defined as root angulation, with parallel root recorded as zero and divergent root as positive. Measurements of Crowding and Crown Morphology on Digital Models Pre-treatment digital models provided by ClinCheck (Align Technology, California, USA) and Dolphin Imaging Software (Dolphin Imaging & Management Solutions, Chatsworth, USA) were captured according to tooth position and imported into ImageJ software (National Institute of Health, USA), respectively. The crown length (CL) and crown width (CW) of each front tooth were measured, and crown morphology was defined as CW/CL. The tooth crown was evenly divided into three parts, and CW was defined as the proximal and distal distance between middle 1/3 and cervical 1/3 junction; CL was defined as the distance from the apex of the gingival margin to the midpoint of the incisal margin or the cusp (Fig. 4 ). The crowding was measured by the difference between the total size of the crown of the front teeth and the existing arch length. Statistical Analysis IBM SPSS Statistics 26 (International Business Machines Corp., Chicago, IL, USA) software was used for statistical analysis, and kappa value was used to determine the consistency and repeatability among raters, with a significance level set at P < 0.05. All data were measured three times and averaged by an inspector. Independent t-test was used to analyze the crowding degree and crown morphology, treatment time, age, root angle after treatment, distance between cementoenamel junction and distance from ICP to ABC in both groups. Logistic regression analysis was performed to assess the correlation between multiple variables. Results The overall kappa statistic of 0.917 reflected an almost complete level of agreement. ( P < 0.001). After orthodontic treatment, 64 out of 82 non extraction patients had OGEs in their front teeth, with a prevalence rate of 73.17%. Among these sites, the incidence of mandibular central incisors was the highest, at 39.02%; this was followed by that between mandibular lateral incisors and central incisors (34.15% and 35.37% at sites 31–32 and 41–42, respectively) (Table 1 ). The incidence of maxillary central incisors was 25.61%. Moderate OGEs were mainly observed between the lower central incisors, with a incidence of 12.20%. No severe OGEs were found at 820 sites in the anterior maxilla and mandible. Table 1 Incidence and severity of open gingival embrasures. Tooth site Occurrence Nonoccurrence Mild Moderate Severe Maxilla 13 − 12 71 (86.6) 11 (13.4) 0 0 12 − 11 74 (90.2) 8 (9.8) 0 0 11–21 61 (76.3) 19 (23.2) 2 (2.4) 0 21–22 75 (91.5) 5 (6.1) 2 (2.4) 0 22–23 74 (90.2) 8 (9.8) 0 0 Total 355 (86.6) 51 (12.4) 4 (1.0) 0 Mandible 33 − 32 65 (79.3) 15 (18.3) 2 (2.4) 0 32 − 31 54 (65.9) 24 (29.3) 4 (4.9) 0 31–41 50 (61.0) 22 (26.8) 10 12.2) 0 41–42 53 (64.6) 26 (31.7) 3 (3.7) 0 42–43 62 (75.6) 20 (24.4) 0 0 Total 284 (69.3) 107 (26.1) 19 (4.6) 0 Data were presented as n (%). In the maxilla, the age, distance between enamel cementum after treatment, distance from ICP to ABC before and after treatment, and their differences in the non-occurrence group were all smaller than those in the occurrence group ( P < 0.05, Table 2 ). While in the mandible, the non-occurrence group had significantly smaller age, crowding, distance from ICP to ABC before and after treatment and its difference, and significantly larger mesial crown morphology and root angulation after treatment ( P < 0.05). The OGEs were evaluated according to the severity between the incisors in the mandible. The crown morphology of left mandibular central incisors in the mild group was larger than that in the moderate group. The distance from ICP to ABC after treatment and the difference during treatment were smaller than those of the moderate group ( P < 0.05, Table 3 ). Table 2 Comparison of OGEs between the nonoccurrence and occurrence groups in the maxilla and mandible. Measurements Maxilla Mandible Nonoccurrence Occurrence Nonoccurrence Occurrence (n = 355) (n = 55) P value (n = 284) (n = 126) P value Age, y 25.44 ± 4.872 28.24 ± 6.760 0.004* 25.21 ± 4.665 27.18 ± 6.160 0.002* Treatment duration, month 26.713 ± 6.832 26.082 ± 5.534 0.449 26.357 ± 7.088 27.238 ± 5.595 0.178 Crowding, mm 2.129 ± 1.498 2.369 ± 1.411 0.266 2.182 ± 1.651 2.811 ± 1.642 0.000* Mesial crown ratio 0.785 ± 0.133 0.763 ± 0.141 0.259 0.606 ± 0.124 0.573 ± 0.076 0.006* Distal crown ratio 0.759 ± 0.139 0.760 ± 0.150 0.987 0.631 ± 0.090 0.617 ± 0.162 0.365 Root angulation at T1, ° 0.072 ± 4.645 1.293 ± 4.046 0.066 3.040 ± 5.672 1.744 ± 5.954 0.036* Right CEJ-left CEJ distance at T1, mm 1.676 ± 0.446 1.970 ± 0.608 0.001* 1.492 ± 0.793 1.616 ± 0.435 0.101 Distance from ICP to ABC at T0, mm 3.713 ± 0.663 4.063 ± 0.874 0.006* 3.735 ± 0.833 4.000 ± 0.832 0.003* Distance from ICP to ABC at T1, mm 4.552 ± 0.613 5.349 ± 0.662 0.000* 4.248 ± 0.789 5.031 ± 0.827 0.000* △Distance from ICP to ABC, mm 0.839 ± 0.662 1.286 ± 1.065 0.004* 0.513 ± 0.779 1.030 ± 0.961 0.000* The independent t-test was used to compare the occurrence and non-occurrence groups. The negative value of root angulation indicated convergent roots. SD, standard deviation P value < 0.05 was considered significant (*) Table 3 Comparison of OGEs between the mild and moderate groups in the mandible. Measurement Mild (n = 22) Moderate (n = 10) P value Age, y 27.050 ± 6.528 29.400 ± 6.346 0.348 Treatment duration, month 26.091 ± 5.453 29.800 ± 4.809 0.075 Crowding, mm 2.712 ± 1.575 3.162 ± 1.549 0.457 Mesial crown ratio 0.563 ± 0.065 0.540 ± 0.061 0.339 Distal crown ratio 0.563 ± 0.067 0.510 ± 0.068 0.044* Root angulation at T1, ° -0.951 ± 3.636 0.590 ± 3.104 0.255 Right CEJ-left CEJ distance at T1, mm 1.336 ± 0.383 1.485 ± 0.248 0.199 Distance from ICP to ABC at T0, mm 4.340 ± 0.805 3.986 ± 1.060 0.305 Distance from ICP to ABC at T1, mm 5.027 ± 0.811 5.780 ± 0.820 0.022* △Distance from ICP to ABC, mm 0.687 ± 1.048 1.795 ± 1.194 0.013* The independent t-test was used to compare the mild and moderate groups in the mandible. The negative value of root angulation indicated convergent roots. SD, standard deviation P value < 0.05 was considered significant (*) In order to explore the relationship between the incidence of OGEs and each measurement index, Logistic regression analysis was carried out separately for the upper and lower jaw. In the maxilla, age, the distance between enamel cementum, and the distance from ICP to ABC after treatment were significant influencing factors. The age, crowding degree, and distance from ICP to ABC after treatment in the mandible were significantly correlated with the formation of the OGEs ( P < 0.05, Table 4 ). Table 4 The relationship between risk factors and OGE by multilevel logistic regression analysis. Measurements Maxilla Mandible OR 95% CI P value OR 95% CI P value Age, y 1.119 1.048–1.195 0.001* 1.068 1.018–1.121 0.007* Sex 1.180 0.480–2.899 0.719 1.093 0.577–2.070 0.786 Treatment duration, mon 0.968 0.913–1.026 0.276 0.993 0.956–1.031 0.700 Crowding, mm 0.961 0.745–1.241 0.763 0.846 0.729–0.981 0.027* Mesial crown ratio 0.275 0.010–7.240 0.439 0.343 0.018–6.467 0.475 Distal crown ratio 1.820 0.152–21.787 0.636 3.619 0.272–48.166 0.330 Root angulation at T1, ° 1.064 0.970–1.166 0.188 1.010 0.961–1.062 0.688 Right CEJ-left CEJ distance at T1, mm 2.400 1.146–5.027 0.020* 1.171 0.860–1.594 0.316 Distance from ICP to ABC at T0, mm 0.825 0.488–1.396 0.474 0.853 0.614–1.185 0.342 Distance from ICP to ABC at T1, mm 8.046 4.016–16.122 0.000* 3.475 2.390–5.052 0.000* 3 − 2 vs 1–1 0.358 0.143–0.896 0.028* 0.512 0.242–1.084 0.080 2 − 1 vs 1–1 0.321 0.122–0.842 0.021* 0.845 0.437–1.631 0.615 In multilevel logistic regression analysis, 11 and 41 were defined as mesial. The negative value of root angulation indicated convergent roots. SD, standard deviation P value < 0.05 was considered significant (*) Discussion Rather than assessing the incidence of OGEs between central incisors[ 5 , 8 ], we evaluated the overall OGEs incidence at 10 sites in the front region. We observed that the incidence of OGEs in the anterior region of non-extraction patients with CAT stands as hight as 73.17%, implicating the importance of notifying patients the risk of OGEs during CAT. In addition, we identified several patient-derived risk factors, such as patient’s age, severity of crowding, and the distance between ICP to ABC. Incidence of OGEs in CAT is higher than that of fixed appliances treatment, which may be partly due to the higher stress of clear aligners, adversely affecting periodontal tissues[ 9 , 10 ]. On the other hand, clear aligners cover all crown surface to improve retention, resulting in insufficient gingiva filling space[ 11 , 12 ]. Additionally, clear aligners may have slight cytotoxic effects on gingival fibroblasts and could also affect the expression of proteins related to inflammatory responses in oral epithelial cells, potentially affecting cell proliferation and OGEs incidence[ 13 , 14 ]. Currently, whether age is a risk factor for the development of OGEs are inconsistent[ 15 – 17 ]. In this study, age was identified as one of the influencing factors for OGEs. Ko-Kimura et al.[ 18 ] found that the probability of OGEs in patients over 20 years old was greater than that in young patients under 20. On the one hand, aging may contribute to thinning of the oral epithelium and widening of the interdental spaces, leading to a decrease in the gingiva thickness and a reduction in the papilla height[ 19 , 20 ]. On the other hand, aging is accompanied by long-term plaque accumulation and occlusal trauma, exacerbating periodontal status[ 16 ]. Simultaneously, the capacity for tissue healing diminishes with aging, compromising the intactness of periodontal structures[ 18 , 21 ]. In the present study, the distance from the ABC to (ICP) after treatment has a significant impact on the occurrence of OGEs. When the distance between ICP and ABC was less than 5 mm, the possibility of OGEs was relatively low. The result supported findings of Tarnow et al.[ 22 ], who reported that the incidence of OGEs was only 2% when the distance between ICP and ABC was 5 mm, but significantly increased to 44% when the distance reached 6 mm. In addition, Kurth & Kokich[ 1 ]and Chang[ 23 ] also reported an increase in the incidence of OGEs with the greater distance between the ICP and ABC. Orthodontic treatment can lead to an average absorption of approximately 0.29 mm of alveolar bone[ 24 ]. In addition, Artun et al. found that the support of alveolar bone in the anterior dental area decreased by about 2.24% in adults after orthodontic treatment[ 25 ]. Out of the 820 sites examined in this study, only a few sites exhibited increased alveolar bone level. The occurrence of OGEs was also influenced by the shape of teeth, particularly the morphology of the cervical one-third of the tooth. The probability of OGEs was higher when the crown shape was divergent or triangular. This was consistent with previous ideas proposed by Chow YC and Jacklyn R[ 1 , 26 ]. This phenomenon was attributed to the greater amount of dental tissue and longer proximal contact distances in square teeth compared to triangular ones. The increased distance between adjacent contact points in triangular teeth and the osseous crest led to a higher incidence of OGEs. Additionally, triangular crowns may also be associated with "scalloped-thin" gingiva. In contrast to thick periodontal biotypes, "scalloped-thin" gingiva has poorer vascularity and reduced biological capacity when exposed to external stimuli, making it more susceptible to gingiva recession and attachment loss[ 27 ]. Although no significant statistical differences were observed in the regression analysis, this may be due to several factors. Gingival status and tooth attrition may affect measurement of crown length, while the shape of the adjacent area and the width of the contact area may impact measurement of crown width. Initial crowding was also identified as a risk factor for OGEs. Regression analysis revealed that the degree of crowding only had a significant impact on the mandible ( P < 0.05), The odds ratio was 0.845, which meant that the risk of the OGEs increased by 0.845 times for every 1 mm decrease in the degree of crowding of the mandibular region. Unravelling the crowded teeth results in the root separation, stretching the interdental papilla and reducing gingival thickness, all of which increased the risk of the OGEs[ 12 , 28 ]. The reason for no statistical significance in the maxillary region may be that the patients included in this study were all non-extraction cases, and the crowding in the anterior tooth area was minimal, which weakened the influence of crowding on the OGEs. In addition, the occurrence of OGEs was also affected by the morphology of the embrasure. In the present study, the distance between adjacent enamel cementum after treatment had a significant effect on maxillary ( P < 0.05), This effect could be attributed to the greater bone loss in the long-wide and short-wide group compared to the long-narrow and short-narrow group at the same crest bone absorption height[ 17 ]. However, root angulation did not have a significant effect on the development of OGEs. This may be due to the fact that after the end of orthodontics, most of the roots were parallel, thus diminishing the impact of root angles[ 8 ]. However, there are some limitations to this study. Due to the characteristics of the retrospective study, the periodontal status of the patients, such as periodontal phenotype and probing depth, could not be completely recorded. Despite this, we had made efforts to minimize the influence of periodontal status on the statistical analysis of OGEs incidence, we excluded patients who had used medications affecting gingival conditions, had a history of periodontitis, or had undergone periodontal surgery in the anterior region. Additionally, although OGEs are recognized as the third most undesirable aesthetic concern by patients, this study did not assess their acceptance and perceptions of the presence of OGEs following treatment. At present, there are limited articles about the occurrence of OGEs after clear aligner treatment, and most of them concentrate on the upper and lower central incisors. However, with the increasing popularity of clear aligners, further researches with larger sample sizes and investigations are needed to explore the potential influencing factors, so as to prevent or reduce the occurrence of OGEs and provide a theoretical basis for the prediction of the OGEs. Conclusions The incidence of OGEs in the anterior teeth area of the upper and lower jaw was 73.17%, with the highest incidence rate being the mandibular central incisor at 39.02%, followed by the site between mandibular central incisors and lateral incisors, with an incidence rate of 34.15% -35.37%. Age, mandibular crowding, the distance between maxillary enamel cementum and the distance between ICP and ABC increased the risk of the development of OGEs. The tooth shape and the distance of ICP to ABC before and after treatment influenced the severity of OGEs of the mandibular central incisors. Abbreviations OGEs open gingival embrasures CAT clear aligner treatment ICP interproximal contact point ABC alveolar bone crest IPR interproximal enamel reduction CEJ cementoenamel junction CL crown length CW crown width Declarations Acknowledgements Not applicable. Authors' contributions Wenjie Cui: Conceptualization; Data curation; Formal analysis; Investigation; Methodology; Project administration; Software; Supervision; Visualization; Roles/Writing - original draft; and Writing - review & editing. Yibai Liu: Project administration; Software; SupervisioBBMMCCBBn; and Visualization. Yang Zhao: Data curation; Formal analysis; Investigation; and Software. Lang Lei: Conceptualization; Funding acquisition; Investigation; Methodology; Resources; Supervision; Validation; and Writing - review & editing. Houxuan Li: Conceptualization; project administration; resources; supervision; critical revision of the manuscript. Funding This work was supported by Natural Science Foundation of China (82371007) Data availability The datasets used and analyzed during the current study are available from the corresponding author on reasonable request. Ethics approval and consent to participate All experiments in this study were conducted in accordance with the Helsinki Declaration. This retrospective study was approved by the Ethical Committee of Nanjing Stomatological Hospital, Affiliated Hospital of Medical School, Institute of Stomatology, Nanjing University, Nanjing, China (NJSH-2023NL-036). Informed consent for the anonymous use of patient data was obtained from all individual participants included in the study. Consent for publication All patients signed the informed consent. 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Am J Orthod Dentofac Orthop. 1994;105(5):506–11. Additional Declarations No competing interests reported. Cite Share Download PDF Status: Published Journal Publication published 11 Apr, 2025 Read the published version in BMC Oral Health → Version 1 posted Editorial decision: Revision requested 20 Feb, 2025 Reviews received at journal 18 Feb, 2025 Reviews received at journal 13 Feb, 2025 Reviewers agreed at journal 10 Feb, 2025 Reviewers agreed at journal 07 Feb, 2025 Reviewers invited by journal 02 Feb, 2025 Editor invited by journal 08 Jan, 2025 Editor assigned by journal 06 Jan, 2025 Submission checks completed at journal 06 Jan, 2025 First submitted to journal 04 Jan, 2025 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. 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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-5762697","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":398317365,"identity":"7577314e-b957-4624-a26e-6cf9306b8fd6","order_by":0,"name":"Wenjie Cui","email":"","orcid":"","institution":"Bachelor of Dental Science (B.D.S), Nanjing Stomatological Hospital, Nanjing University","correspondingAuthor":false,"prefix":"","firstName":"Wenjie","middleName":"","lastName":"Cui","suffix":""},{"id":398317367,"identity":"59b90720-ebe8-4596-8c75-174a8f587c59","order_by":1,"name":"Yibai Liu","email":"","orcid":"","institution":"Bachelor of Dental Science (B.D.S), Nanjing Stomatological Hospital, Nanjing University","correspondingAuthor":false,"prefix":"","firstName":"Yibai","middleName":"","lastName":"Liu","suffix":""},{"id":398317368,"identity":"a86cd1da-3cc4-4189-8c56-c1c6bfdb328d","order_by":2,"name":"Yang Zhao","email":"","orcid":"","institution":"Bachelor of Dental Science (B.D.S), Nanjing Stomatological Hospital, Nanjing University","correspondingAuthor":false,"prefix":"","firstName":"Yang","middleName":"","lastName":"Zhao","suffix":""},{"id":398317369,"identity":"f22b3633-1ba2-4a06-a07b-3271993322d3","order_by":3,"name":"Lang Lei","email":"","orcid":"","institution":"Nanjing Stomatological Hospital, Nanjing University","correspondingAuthor":false,"prefix":"","firstName":"Lang","middleName":"","lastName":"Lei","suffix":""},{"id":398317370,"identity":"068aee83-b36e-4874-9498-6830e72398f5","order_by":4,"name":"Houxuan Li","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA+UlEQVRIie3QMUvEMBTA8VcOekuuXQMV+xUaAjrciX6UVwrtJN7Y8URIFz/ADYefIZNw2ytZA66CS6HgJtzYSTzxFBwudnTIf0mG94O8APh8/7Bowg63eFX0A/DTcNqQk4Q/hNOrBFjIiFl0E/gmkHcJQJk/8KvMTaaztp8pk56DQbkEUykOCEP96HhYVEhmjdjeKezXYK5VckvBvX1x7XKWsNoEmixm7JOcEE4C9RfJzKWmmx3fkyrkmI0gtck1ISYMShxDpNjYqtDPVIo1LITaf3Lr2iWOreje1PxCP62Kbgc8TZum7Yb6OPld8P510sh5n8/n8x3pAy14UryeGT1EAAAAAElFTkSuQmCC","orcid":"","institution":"Nanjing Stomatological Hospital, Nanjing University","correspondingAuthor":true,"prefix":"","firstName":"Houxuan","middleName":"","lastName":"Li","suffix":""}],"badges":[],"createdAt":"2025-01-04 09:38:06","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-5762697/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-5762697/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1186/s12903-025-05915-5","type":"published","date":"2025-04-11T16:05:24+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":73339098,"identity":"438c9d58-faaf-4aa3-a410-4eaa8f20188a","added_by":"auto","created_at":"2025-01-09 05:00:10","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":140001,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eClassification of the OGEs incidence and severity. \u003c/strong\u003eOpen gingival embrasures were classified according to severity. Line a, a tangent line to the highest gingival curvature of the crown. Line b, a line that passed through the most cervical contact point and was parallel to line a. Line c, a line that bisected the distance between line a and line b. The severity of the open gingival embrasures (normal, mild, moderate, severe) was determined according to the position of the tip of each gingival papilla in the anterior dental region\u003c/p\u003e","description":"","filename":"Fig3.TIF.jpg","url":"https://assets-eu.researchsquare.com/files/rs-5762697/v1/686d84a2d892964de3a7407a.jpg"},{"id":73338061,"identity":"8f492339-0ddb-4baf-9d56-9b682b99dd54","added_by":"auto","created_at":"2025-01-09 04:52:10","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":96171,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eMeasurement of the distance between cementoenamel junction (CEJ)\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"Fig1.TIF.jpg","url":"https://assets-eu.researchsquare.com/files/rs-5762697/v1/2c7bd36ea03b04dd3fba3e5e.jpg"},{"id":73339099,"identity":"afa4f80c-9279-4a60-be36-d5081b4c3150","added_by":"auto","created_at":"2025-01-09 05:00:10","extension":"jpg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":105591,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eMeasurement of root angulation and distance from interproximal contact point to alveolar bone crest\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"Fig2.TIF.jpg","url":"https://assets-eu.researchsquare.com/files/rs-5762697/v1/0a6f48d978e28c653fcd5ed3.jpg"},{"id":73338063,"identity":"58c715f3-8e2e-48df-8700-42c782875e73","added_by":"auto","created_at":"2025-01-09 04:52:10","extension":"jpg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":105601,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eMeasurement of the crown ratio. \u003c/strong\u003eCW crown width, CL crown length\u003c/p\u003e","description":"","filename":"Fig4.TIF.jpg","url":"https://assets-eu.researchsquare.com/files/rs-5762697/v1/bbcb69a3bbd0ceb434a92a03.jpg"},{"id":80559101,"identity":"a61d15dc-d7b5-41ee-8c6d-4e99da7cd94a","added_by":"auto","created_at":"2025-04-14 16:17:47","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1513224,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-5762697/v1/9e5579d9-ddae-4b4c-8ac9-fd05a8e61e6a.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Risk factors for open gingival embrasures after clear aligners treatment: A retrospective study","fulltext":[{"header":"Introduction","content":"\u003cp\u003eOpen gingival embrasures (OGEs), also called black triangles, are the gap below proximal contacts and not filled with the papilla. A high incidence of OGEs was observed in adult orthodontic patients, ranging from 38 to 43.7%[\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. The presence of the OGEs greatly impairs smiling esthetics, and it is the third most unpleasant aesthetic issue after dental caries and crown margins[\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. In addition, they may affect pronunciation, and bring periodontal problems, such as food retention and biofilm accumulation[\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eMultiple factors contribute to the occurrence of OGEs. Most notably, alveolar bone resorption and patient's thin-scalloped periodontal biotype are major risk factor of OGEs. OGE is one of the most complained issue in the adult orthodontics. Patient age, the degree of dentition crowding, the distance from the proximal contact point to the crest of the bone, tooth morphology, and the direction of gingival movement during orthodontic tooth movement with fixed appliances can also increase the likelihood of OGEs[\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eDespite its well acceptance of clear aligner therapy(CAT) in adult patients due to its less interference on facial esthetics, OGEs are commonly present after CAT. The incidence rate stands at 25.7% and 40.3% between the two central incisor of the maxilla and mandible, respectively[\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. Several modalities have been proposed to reduce the adverse effect of OGEs, such as adjustment of the tooth axial inclination, interproximal enamel reduction (IPR) to modify the crown shape, or restorative procedures using resin or veneers[\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. However, the potential risk factors for the occurrence of OGEs during CAT are less clear.\u003c/p\u003e \u003cp\u003eCurrently, researches on OGEs in the context of CAT are very limited. One study explored the impact of the number of attachments and IPR on the occurrence of OGE between central incisors, finding that the number of attachments affects the incidence of OGE, and IPR may influence the severity of OGE[\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. But the relationship between patient-related factors such as age, periodontal phenotype, tooth shape, and degree of dental crowding with OGEs remains unclear. Therefore, further research on the relationship between these factors and the occurrence of OGEs is essential.\u003c/p\u003e \u003cp\u003eTherefore, the purposes of this study were (1) to determine the presence of OGEs between anterior teeth in adult none-extraction cases with CAT, and (2) to explore the potential factors that affect the occurrence of the OGEs.\u003c/p\u003e"},{"header":"Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eSubjects\u003c/h2\u003e \u003cp\u003e This retrospective study was approved by the Ethical Committee of Nanjing Stomatological Hospital, Affiliated Hospital of Medical School, Institute of Stomatology, Nanjing University, Nanjing, China (NJSH-2023NL-036). All patients signed the informed consent.\u003c/p\u003e \u003cp\u003eEighty-two adult patients (13 males, 69 females; average age 25.82\u0026thinsp;\u0026plusmn;\u0026thinsp;5.27 years old) were selected from the Orthodontics Department of XX Hospital from September 2017 to December 2021.\u003c/p\u003e \u003cp\u003ePatients were selected based on the following criteria: (1) Age\u0026thinsp;\u0026gt;\u0026thinsp;18 years old; (2) Patients underwent non-extraction clear aligners treatment; (3) Complete initial (T0) and final (T1) orthodontic records, including frontal intraoral photos, panoramic radiographs and study models; (4) Patients who do not have a long-term history of medication or have used medication that alters gingiva condition; (5) Patients without systemic diseases. The exclusion criteria were as follows: (1) Missing one or several anterior teeth; (2) History of periodontal disease; (3) Unclear or containing foreign objects such as saliva, food residue, etc. in the front photos; (4) Having a history of periodontal surgery in the upper and lower anterior teeth areas; (5) Women who are pregnant, breastfeeding, or planning to become pregnant during orthodontic treatment; (6) Smoking history. The average treatment time was 26.63\u0026thinsp;\u0026plusmn;\u0026thinsp;6.70 months, and regular oral hygiene instruction was provided during the treatment period.\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eClassification of the OGEs incidence and severity\u003c/h3\u003e\n\u003cp\u003eBased on frontal and lateral intraoral photos taken before and one week after orthodontic treatment, the incidence and severity of the OGEs in the upper and lower anterior teeth areas of patients were statistically analyzed. The incidence and severity were evaluated jointly by one orthodontist and two periodontists. Patients would only be included in the study if the evaluation results of at least two doctors were consistent. Based on the assessment results, the tooth sites were divided into occurrence and non-occurrence groups. Based on the Jemt index (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e), the occurrence group was categorized into three sub-groups: mild, moderate, and severe[\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. The patient's intraoral photographs were taken by a dedicated photographer from our orthodontic department using the same model of equipment.\u003c/p\u003e \u003cp\u003e \u003cb\u003eMeasurement of root angle, distance between cementoenamel junctions (CEJs) and distance from proximal contact point (ICP) to alveolar bone crest (ABC) on panoramic radiographs\u003c/b\u003e \u003c/p\u003e \u003cp\u003eAll variables from panoramic radiographs were measured by using ImageJ software (Version 1.54g; National Institutes of Health, USA), including: (1) distance between the mesial cementoenamel junctions of the two adjacent teeth (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e); (2) distance between the interproximal contact point and alveolar bone crest before (T0), after (T1) and during treatment (△=T1-T0) (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e); (3) the angle between the long axes of adjacent anterior teeth at T1(Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). This angle was defined as root angulation, with parallel root recorded as zero and divergent root as positive.\u003c/p\u003e \n\u003ch3\u003eMeasurements of Crowding and Crown Morphology on Digital Models\u003c/h3\u003e\n\u003cp\u003ePre-treatment digital models provided by ClinCheck (Align Technology, California, USA) and Dolphin Imaging Software (Dolphin Imaging \u0026amp; Management Solutions, Chatsworth, USA) were captured according to tooth position and imported into ImageJ software (National Institute of Health, USA), respectively. The crown length (CL) and crown width (CW) of each front tooth were measured, and crown morphology was defined as CW/CL. The tooth crown was evenly divided into three parts, and CW was defined as the proximal and distal distance between middle 1/3 and cervical 1/3 junction; CL was defined as the distance from the apex of the gingival margin to the midpoint of the incisal margin or the cusp (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e). The crowding was measured by the difference between the total size of the crown of the front teeth and the existing arch length.\u003c/p\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003eStatistical Analysis\u003c/h2\u003e \u003cp\u003eIBM SPSS Statistics 26 (International Business Machines Corp., Chicago, IL, USA) software was used for statistical analysis, and kappa value was used to determine the consistency and repeatability among raters, with a significance level set at \u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05.\u003c/p\u003e \u003cp\u003eAll data were measured three times and averaged by an inspector. Independent t-test was used to analyze the crowding degree and crown morphology, treatment time, age, root angle after treatment, distance between cementoenamel junction and distance from ICP to ABC in both groups. Logistic regression analysis was performed to assess the correlation between multiple variables.\u003c/p\u003e \u003c/div\u003e"},{"header":"Results","content":"\u003cp\u003eThe overall kappa statistic of 0.917 reflected an almost complete level of agreement. (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001). After orthodontic treatment, 64 out of 82 non extraction patients had OGEs in their front teeth, with a prevalence rate of 73.17%. Among these sites, the incidence of mandibular central incisors was the highest, at 39.02%; this was followed by that between mandibular lateral incisors and central incisors (34.15% and 35.37% at sites 31\u0026ndash;32 and 41\u0026ndash;42, respectively) (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). The incidence of maxillary central incisors was 25.61%. Moderate OGEs were mainly observed between the lower central incisors, with a incidence of 12.20%. No severe OGEs were found at 820 sites in the anterior maxilla and mandible.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eIncidence and severity of open gingival embrasures.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eTooth site\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eOccurrence\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eNonoccurrence\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eMild\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eModerate\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eSevere\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMaxilla\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e13\u0026thinsp;\u0026minus;\u0026thinsp;12\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e71 (86.6)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e11 (13.4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e12\u0026thinsp;\u0026minus;\u0026thinsp;11\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e74 (90.2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e8 (9.8)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e11\u0026ndash;21\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e61 (76.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e19 (23.2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2 (2.4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e21\u0026ndash;22\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e75 (91.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e5 (6.1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2 (2.4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e22\u0026ndash;23\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e74 (90.2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e8 (9.8)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eTotal\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e355 (86.6)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e51 (12.4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e4 (1.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eMandible\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e33\u0026thinsp;\u0026minus;\u0026thinsp;32\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e65 (79.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e15 (18.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2 (2.4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e32\u0026thinsp;\u0026minus;\u0026thinsp;31\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e54 (65.9)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e24 (29.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e4 (4.9)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e31\u0026ndash;41\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e50 (61.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e22 (26.8)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e10 12.2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e41\u0026ndash;42\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e53 (64.6)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e26 (31.7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e3 (3.7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e42\u0026ndash;43\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e62 (75.6)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e20 (24.4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eTotal\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e284 (69.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e107 (26.1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e19 (4.6)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"5\"\u003eData were presented as n (%).\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eIn the maxilla, the age, distance between enamel cementum after treatment, distance from ICP to ABC before and after treatment, and their differences in the non-occurrence group were all smaller than those in the occurrence group (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05, Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). While in the mandible, the non-occurrence group had significantly smaller age, crowding, distance from ICP to ABC before and after treatment and its difference, and significantly larger mesial crown morphology and root angulation after treatment (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05). The OGEs were evaluated according to the severity between the incisors in the mandible. The crown morphology of left mandibular central incisors in the mild group was larger than that in the moderate group. The distance from ICP to ABC after treatment and the difference during treatment were smaller than those of the moderate group (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05, Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eComparison of OGEs between the nonoccurrence and occurrence groups in the maxilla and mandible.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"8\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\" morerows=\"2\" rowspan=\"3\"\u003e \u003cp\u003eMeasurements\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"3\" nameend=\"c4\" namest=\"c2\"\u003e \u003cp\u003eMaxilla\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colspan=\"3\" nameend=\"c8\" namest=\"c6\"\u003e \u003cp\u003eMandible\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eNonoccurrence\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eOccurrence\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eNonoccurrence\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003eOccurrence\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c8\"\u003e\u0026nbsp;\u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003e(n\u0026thinsp;=\u0026thinsp;355)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003e(n\u0026thinsp;=\u0026thinsp;55)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003eP\u003c/em\u003e value\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003e(n\u0026thinsp;=\u0026thinsp;284)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003e(n\u0026thinsp;=\u0026thinsp;126)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c8\"\u003e \u003cp\u003e\u003cem\u003eP\u003c/em\u003e value\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAge, y\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e25.44\u0026thinsp;\u0026plusmn;\u0026thinsp;4.872\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e28.24\u0026thinsp;\u0026plusmn;\u0026thinsp;6.760\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e0.004*\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c6\"\u003e \u003cp\u003e25.21\u0026thinsp;\u0026plusmn;\u0026thinsp;4.665\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c7\"\u003e \u003cp\u003e27.18\u0026thinsp;\u0026plusmn;\u0026thinsp;6.160\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e\u003cb\u003e0.002*\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTreatment duration, month\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e26.713\u0026thinsp;\u0026plusmn;\u0026thinsp;6.832\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e26.082\u0026thinsp;\u0026plusmn;\u0026thinsp;5.534\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.449\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c6\"\u003e \u003cp\u003e26.357\u0026thinsp;\u0026plusmn;\u0026thinsp;7.088\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c7\"\u003e \u003cp\u003e27.238\u0026thinsp;\u0026plusmn;\u0026thinsp;5.595\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e0.178\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCrowding, mm\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e2.129\u0026thinsp;\u0026plusmn;\u0026thinsp;1.498\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e2.369\u0026thinsp;\u0026plusmn;\u0026thinsp;1.411\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.266\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c6\"\u003e \u003cp\u003e2.182\u0026thinsp;\u0026plusmn;\u0026thinsp;1.651\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c7\"\u003e \u003cp\u003e2.811\u0026thinsp;\u0026plusmn;\u0026thinsp;1.642\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e\u003cb\u003e0.000*\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMesial crown ratio\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e0.785\u0026thinsp;\u0026plusmn;\u0026thinsp;0.133\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e0.763\u0026thinsp;\u0026plusmn;\u0026thinsp;0.141\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.259\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c6\"\u003e \u003cp\u003e0.606\u0026thinsp;\u0026plusmn;\u0026thinsp;0.124\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c7\"\u003e \u003cp\u003e0.573\u0026thinsp;\u0026plusmn;\u0026thinsp;0.076\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e\u003cb\u003e0.006*\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDistal crown ratio\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e0.759\u0026thinsp;\u0026plusmn;\u0026thinsp;0.139\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e0.760\u0026thinsp;\u0026plusmn;\u0026thinsp;0.150\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.987\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c6\"\u003e \u003cp\u003e0.631\u0026thinsp;\u0026plusmn;\u0026thinsp;0.090\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c7\"\u003e \u003cp\u003e0.617\u0026thinsp;\u0026plusmn;\u0026thinsp;0.162\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e0.365\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eRoot angulation at T1, \u0026deg;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e0.072\u0026thinsp;\u0026plusmn;\u0026thinsp;4.645\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e1.293\u0026thinsp;\u0026plusmn;\u0026thinsp;4.046\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.066\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c6\"\u003e \u003cp\u003e3.040\u0026thinsp;\u0026plusmn;\u0026thinsp;5.672\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c7\"\u003e \u003cp\u003e1.744\u0026thinsp;\u0026plusmn;\u0026thinsp;5.954\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e\u003cb\u003e0.036*\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eRight CEJ-left CEJ distance at T1, mm\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e1.676\u0026thinsp;\u0026plusmn;\u0026thinsp;0.446\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e1.970\u0026thinsp;\u0026plusmn;\u0026thinsp;0.608\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e0.001*\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c6\"\u003e \u003cp\u003e1.492\u0026thinsp;\u0026plusmn;\u0026thinsp;0.793\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c7\"\u003e \u003cp\u003e1.616\u0026thinsp;\u0026plusmn;\u0026thinsp;0.435\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e0.101\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDistance from ICP to ABC at T0, mm\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e3.713\u0026thinsp;\u0026plusmn;\u0026thinsp;0.663\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e4.063\u0026thinsp;\u0026plusmn;\u0026thinsp;0.874\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e0.006*\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c6\"\u003e \u003cp\u003e3.735\u0026thinsp;\u0026plusmn;\u0026thinsp;0.833\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c7\"\u003e \u003cp\u003e4.000\u0026thinsp;\u0026plusmn;\u0026thinsp;0.832\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e\u003cb\u003e0.003*\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDistance from ICP to ABC at T1, mm\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e4.552\u0026thinsp;\u0026plusmn;\u0026thinsp;0.613\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e5.349\u0026thinsp;\u0026plusmn;\u0026thinsp;0.662\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e0.000*\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c6\"\u003e \u003cp\u003e4.248\u0026thinsp;\u0026plusmn;\u0026thinsp;0.789\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c7\"\u003e \u003cp\u003e5.031\u0026thinsp;\u0026plusmn;\u0026thinsp;0.827\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e\u003cb\u003e0.000*\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e△Distance from ICP to ABC, mm\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e0.839\u0026thinsp;\u0026plusmn;\u0026thinsp;0.662\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e1.286\u0026thinsp;\u0026plusmn;\u0026thinsp;1.065\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e0.004*\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c6\"\u003e \u003cp\u003e0.513\u0026thinsp;\u0026plusmn;\u0026thinsp;0.779\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c7\"\u003e \u003cp\u003e1.030\u0026thinsp;\u0026plusmn;\u0026thinsp;0.961\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e\u003cb\u003e0.000*\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"8\"\u003eThe independent t-test was used to compare the occurrence and non-occurrence groups.\u003c/td\u003e\u003c/tr\u003e \u003ctr\u003e\u003ctd colspan=\"8\"\u003eThe negative value of root angulation indicated convergent roots.\u003c/td\u003e\u003c/tr\u003e \u003ctr\u003e\u003ctd colspan=\"8\"\u003eSD, standard deviation\u003c/td\u003e\u003c/tr\u003e \u003ctr\u003e\u003ctd colspan=\"8\"\u003e\u003cem\u003eP\u003c/em\u003e value\u0026thinsp;\u0026lt;\u0026thinsp;0.05 was considered significant (*)\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eComparison of OGEs between the mild and moderate groups in the mandible.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"4\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMeasurement\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eMild (n\u0026thinsp;=\u0026thinsp;22)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eModerate (n\u0026thinsp;=\u0026thinsp;10)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003eP\u003c/em\u003e value\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAge, y\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e27.050\u0026thinsp;\u0026plusmn;\u0026thinsp;6.528\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e29.400\u0026thinsp;\u0026plusmn;\u0026thinsp;6.346\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.348\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTreatment duration, month\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e26.091\u0026thinsp;\u0026plusmn;\u0026thinsp;5.453\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e29.800\u0026thinsp;\u0026plusmn;\u0026thinsp;4.809\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.075\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCrowding, mm\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e2.712\u0026thinsp;\u0026plusmn;\u0026thinsp;1.575\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e3.162\u0026thinsp;\u0026plusmn;\u0026thinsp;1.549\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.457\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMesial crown ratio\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e0.563\u0026thinsp;\u0026plusmn;\u0026thinsp;0.065\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e0.540\u0026thinsp;\u0026plusmn;\u0026thinsp;0.061\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.339\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDistal crown ratio\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e0.563\u0026thinsp;\u0026plusmn;\u0026thinsp;0.067\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e0.510\u0026thinsp;\u0026plusmn;\u0026thinsp;0.068\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e0.044*\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eRoot angulation at T1, \u0026deg;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e-0.951\u0026thinsp;\u0026plusmn;\u0026thinsp;3.636\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e0.590\u0026thinsp;\u0026plusmn;\u0026thinsp;3.104\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.255\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eRight CEJ-left CEJ distance at T1, mm\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e1.336\u0026thinsp;\u0026plusmn;\u0026thinsp;0.383\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e1.485\u0026thinsp;\u0026plusmn;\u0026thinsp;0.248\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.199\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDistance from ICP to ABC at T0, mm\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e4.340\u0026thinsp;\u0026plusmn;\u0026thinsp;0.805\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e3.986\u0026thinsp;\u0026plusmn;\u0026thinsp;1.060\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.305\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDistance from ICP to ABC at T1, mm\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e5.027\u0026thinsp;\u0026plusmn;\u0026thinsp;0.811\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e5.780\u0026thinsp;\u0026plusmn;\u0026thinsp;0.820\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e0.022*\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e△Distance from ICP to ABC, mm\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e0.687\u0026thinsp;\u0026plusmn;\u0026thinsp;1.048\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e1.795\u0026thinsp;\u0026plusmn;\u0026thinsp;1.194\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e0.013*\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"4\"\u003eThe independent t-test was used to compare the mild and moderate groups in the mandible.\u003c/td\u003e\u003c/tr\u003e \u003ctr\u003e\u003ctd colspan=\"4\"\u003eThe negative value of root angulation indicated convergent roots.\u003c/td\u003e\u003c/tr\u003e \u003ctr\u003e\u003ctd colspan=\"4\"\u003eSD, standard deviation\u003c/td\u003e\u003c/tr\u003e \u003ctr\u003e\u003ctd colspan=\"4\"\u003e\u003cem\u003eP\u003c/em\u003e value\u0026thinsp;\u0026lt;\u0026thinsp;0.05 was considered significant (*)\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eIn order to explore the relationship between the incidence of OGEs and each measurement index, Logistic regression analysis was carried out separately for the upper and lower jaw. In the maxilla, age, the distance between enamel cementum, and the distance from ICP to ABC after treatment were significant influencing factors. The age, crowding degree, and distance from ICP to ABC after treatment in the mandible were significantly correlated with the formation of the OGEs (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05, Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab4\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eThe relationship between risk factors and OGE by multilevel logistic regression analysis.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"8\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eMeasurements\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"3\" nameend=\"c4\" namest=\"c2\"\u003e \u003cp\u003eMaxilla\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colspan=\"3\" nameend=\"c8\" namest=\"c6\"\u003e \u003cp\u003eMandible\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eOR\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003e95% CI\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003eP\u003c/em\u003e value\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eOR\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003e95% CI\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c8\"\u003e \u003cp\u003e\u003cem\u003eP\u003c/em\u003e value\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAge, y\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1.119\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e1.048\u0026ndash;1.195\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e0.001*\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e1.068\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e1.018\u0026ndash;1.121\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e\u003cb\u003e0.007*\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSex\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1.180\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.480\u0026ndash;2.899\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.719\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e1.093\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e0.577\u0026ndash;2.070\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e0.786\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTreatment duration, mon\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.968\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.913\u0026ndash;1.026\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.276\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.993\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e0.956\u0026ndash;1.031\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e0.700\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCrowding, mm\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.961\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.745\u0026ndash;1.241\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.763\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.846\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e0.729\u0026ndash;0.981\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e\u003cb\u003e0.027*\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMesial crown ratio\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.275\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.010\u0026ndash;7.240\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.439\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.343\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e0.018\u0026ndash;6.467\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e0.475\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDistal crown ratio\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1.820\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.152\u0026ndash;21.787\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.636\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e3.619\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e0.272\u0026ndash;48.166\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e0.330\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eRoot angulation at T1, \u0026deg;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1.064\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.970\u0026ndash;1.166\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.188\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e1.010\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e0.961\u0026ndash;1.062\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e0.688\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eRight CEJ-left CEJ distance at T1, mm\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e2.400\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e1.146\u0026ndash;5.027\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e0.020*\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e1.171\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e0.860\u0026ndash;1.594\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e0.316\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDistance from ICP to ABC at T0, mm\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.825\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.488\u0026ndash;1.396\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.474\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.853\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e0.614\u0026ndash;1.185\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e0.342\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDistance from ICP to ABC at T1, mm\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e8.046\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e4.016\u0026ndash;16.122\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e0.000*\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e3.475\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e2.390\u0026ndash;5.052\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e\u003cb\u003e0.000*\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e3\u0026thinsp;\u0026minus;\u0026thinsp;2 vs 1\u0026ndash;1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.358\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.143\u0026ndash;0.896\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e0.028*\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.512\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e0.242\u0026ndash;1.084\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e0.080\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2\u0026thinsp;\u0026minus;\u0026thinsp;1 vs 1\u0026ndash;1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.321\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.122\u0026ndash;0.842\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e0.021*\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.845\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e0.437\u0026ndash;1.631\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e0.615\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"8\"\u003eIn multilevel logistic regression analysis, 11 and 41 were defined as mesial.\u003c/td\u003e\u003c/tr\u003e \u003ctr\u003e\u003ctd colspan=\"8\"\u003eThe negative value of root angulation indicated convergent roots.\u003c/td\u003e\u003c/tr\u003e \u003ctr\u003e\u003ctd colspan=\"8\"\u003eSD, standard deviation\u003c/td\u003e\u003c/tr\u003e \u003ctr\u003e\u003ctd colspan=\"8\"\u003e\u003cem\u003eP\u003c/em\u003e value\u0026thinsp;\u0026lt;\u0026thinsp;0.05 was considered significant (*)\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eRather than assessing the incidence of OGEs between central incisors[\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e, \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e], we evaluated the overall OGEs incidence at 10 sites in the front region. We observed that the incidence of OGEs in the anterior region of non-extraction patients with CAT stands as hight as 73.17%, implicating the importance of notifying patients the risk of OGEs during CAT. In addition, we identified several patient-derived risk factors, such as patient\u0026rsquo;s age, severity of crowding, and the distance between ICP to ABC.\u003c/p\u003e \u003cp\u003eIncidence of OGEs in CAT is higher than that of fixed appliances treatment, which may be partly due to the higher stress of clear aligners, adversely affecting periodontal tissues[\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e, \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. On the other hand, clear aligners cover all crown surface to improve retention, resulting in insufficient gingiva filling space[\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e, \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. Additionally, clear aligners may have slight cytotoxic effects on gingival fibroblasts and could also affect the expression of proteins related to inflammatory responses in oral epithelial cells, potentially affecting cell proliferation and OGEs incidence[\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e, \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eCurrently, whether age is a risk factor for the development of OGEs are inconsistent[\u003cspan additionalcitationids=\"CR16\" citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. In this study, age was identified as one of the influencing factors for OGEs. Ko-Kimura et al.[\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e] found that the probability of OGEs in patients over 20 years old was greater than that in young patients under 20. On the one hand, aging may contribute to thinning of the oral epithelium and widening of the interdental spaces, leading to a decrease in the gingiva thickness and a reduction in the papilla height[\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e, \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]. On the other hand, aging is accompanied by long-term plaque accumulation and occlusal trauma, exacerbating periodontal status[\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. Simultaneously, the capacity for tissue healing diminishes with aging, compromising the intactness of periodontal structures[\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e, \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eIn the present study, the distance from the ABC to (ICP) after treatment has a significant impact on the occurrence of OGEs. When the distance between ICP and ABC was less than 5 mm, the possibility of OGEs was relatively low. The result supported findings of Tarnow et al.[\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e], who reported that the incidence of OGEs was only 2% when the distance between ICP and ABC was 5 mm, but significantly increased to 44% when the distance reached 6 mm. In addition, Kurth \u0026amp; Kokich[\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]and Chang[\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e] also reported an increase in the incidence of OGEs with the greater distance between the ICP and ABC. Orthodontic treatment can lead to an average absorption of approximately 0.29 mm of alveolar bone[\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e]. In addition, Artun et al. found that the support of alveolar bone in the anterior dental area decreased by about 2.24% in adults after orthodontic treatment[\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]. Out of the 820 sites examined in this study, only a few sites exhibited increased alveolar bone level.\u003c/p\u003e \u003cp\u003eThe occurrence of OGEs was also influenced by the shape of teeth, particularly the morphology of the cervical one-third of the tooth. The probability of OGEs was higher when the crown shape was divergent or triangular. This was consistent with previous ideas proposed by Chow YC and Jacklyn R[\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]. This phenomenon was attributed to the greater amount of dental tissue and longer proximal contact distances in square teeth compared to triangular ones. The increased distance between adjacent contact points in triangular teeth and the osseous crest led to a higher incidence of OGEs. Additionally, triangular crowns may also be associated with \"scalloped-thin\" gingiva. In contrast to thick periodontal biotypes, \"scalloped-thin\" gingiva has poorer vascularity and reduced biological capacity when exposed to external stimuli, making it more susceptible to gingiva recession and attachment loss[\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e]. Although no significant statistical differences were observed in the regression analysis, this may be due to several factors. Gingival status and tooth attrition may affect measurement of crown length, while the shape of the adjacent area and the width of the contact area may impact measurement of crown width.\u003c/p\u003e \u003cp\u003eInitial crowding was also identified as a risk factor for OGEs. Regression analysis revealed that the degree of crowding only had a significant impact on the mandible (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05), The odds ratio was 0.845, which meant that the risk of the OGEs increased by 0.845 times for every 1 mm decrease in the degree of crowding of the mandibular region. Unravelling the crowded teeth results in the root separation, stretching the interdental papilla and reducing gingival thickness, all of which increased the risk of the OGEs[\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e, \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e]. The reason for no statistical significance in the maxillary region may be that the patients included in this study were all non-extraction cases, and the crowding in the anterior tooth area was minimal, which weakened the influence of crowding on the OGEs.\u003c/p\u003e \u003cp\u003eIn addition, the occurrence of OGEs was also affected by the morphology of the embrasure. In the present study, the distance between adjacent enamel cementum after treatment had a significant effect on maxillary (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05), This effect could be attributed to the greater bone loss in the long-wide and short-wide group compared to the long-narrow and short-narrow group at the same crest bone absorption height[\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. However, root angulation did not have a significant effect on the development of OGEs. This may be due to the fact that after the end of orthodontics, most of the roots were parallel, thus diminishing the impact of root angles[\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eHowever, there are some limitations to this study. Due to the characteristics of the retrospective study, the periodontal status of the patients, such as periodontal phenotype and probing depth, could not be completely recorded. Despite this, we had made efforts to minimize the influence of periodontal status on the statistical analysis of OGEs incidence, we excluded patients who had used medications affecting gingival conditions, had a history of periodontitis, or had undergone periodontal surgery in the anterior region. Additionally, although OGEs are recognized as the third most undesirable aesthetic concern by patients, this study did not assess their acceptance and perceptions of the presence of OGEs following treatment.\u003c/p\u003e \u003cp\u003eAt present, there are limited articles about the occurrence of OGEs after clear aligner treatment, and most of them concentrate on the upper and lower central incisors. However, with the increasing popularity of clear aligners, further researches with larger sample sizes and investigations are needed to explore the potential influencing factors, so as to prevent or reduce the occurrence of OGEs and provide a theoretical basis for the prediction of the OGEs.\u003c/p\u003e"},{"header":"Conclusions","content":"\u003cp\u003e \u003col\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eThe incidence of OGEs in the anterior teeth area of the upper and lower jaw was 73.17%, with the highest incidence rate being the mandibular central incisor at 39.02%, followed by the site between mandibular central incisors and lateral incisors, with an incidence rate of 34.15% -35.37%.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eAge, mandibular crowding, the distance between maxillary enamel cementum and the distance between ICP and ABC increased the risk of the development of OGEs.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eThe tooth shape and the distance of ICP to ABC before and after treatment influenced the severity of OGEs of the mandibular central incisors.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003c/ol\u003e \u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cp\u003eOGEs \u0026nbsp;open gingival embrasures\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eCAT \u0026nbsp;clear aligner treatment\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eICP \u0026nbsp;interproximal contact point\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eABC \u0026nbsp;alveolar bone crest\u003c/p\u003e\n\u003cp\u003eIPR \u0026nbsp;interproximal enamel reduction\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eCEJ \u0026nbsp;cementoenamel junction\u003c/p\u003e\n\u003cp\u003eCL \u0026nbsp;crown length\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eCW \u0026nbsp;crown width\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgements\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthors\u0026apos; contributions\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eWenjie Cui:\u003c/strong\u003e Conceptualization; Data curation; Formal analysis; Investigation; Methodology; Project administration; Software; Supervision; Visualization; Roles/Writing - original draft; and Writing - review \u0026amp; editing. \u003cstrong\u003eYibai Liu:\u003c/strong\u003e Project administration; Software; SupervisioBBMMCCBBn; and Visualization. \u003cstrong\u003eYang Zhao:\u003c/strong\u003e Data curation; Formal analysis; Investigation; and Software. \u003cstrong\u003eLang Lei:\u003c/strong\u003e Conceptualization; Funding acquisition; Investigation; Methodology; Resources; Supervision; Validation; and Writing - review \u0026amp; editing. \u003cstrong\u003eHouxuan Li:\u003c/strong\u003e Conceptualization; project administration; resources; supervision; critical revision of the manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis work was supported by Natural Science Foundation of China (82371007)\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData availability\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe datasets used and analyzed during the current study are available from the corresponding author on reasonable request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthics approval and consent to participate\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll experiments in this study were conducted in accordance with the Helsinki Declaration. This retrospective study was approved by the Ethical Committee of Nanjing Stomatological Hospital, Affiliated Hospital of Medical School, Institute of Stomatology, Nanjing University, Nanjing, China (NJSH-2023NL-036). Informed consent for the anonymous use of patient data was obtained from all individual participants included in the study.\u003c/p\u003e\n\u003ch4\u003eConsent for publication\u003c/h4\u003e\n\u003cp\u003eAll patients signed the informed consent.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interest \u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eDisclosure statement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors report there are no competing interests to declare.\u0026nbsp;\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eKurth JR, Kokich VG. Open gingival embrasures after orthodontic treatment in adults: prevalence and etiology. Am J Orthod Dentofac Orthop. 2001;120(2):116\u0026ndash;23.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eCunliffe J, Pretty I. Patients' ranking of interdental black triangles against other common aesthetic problems. Eur J Prosthodont Restor Dent. 2009;17(4):177\u0026ndash;81.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eZiahosseini P, Hussain F, Millar BJ. Management of gingival black triangles. Br Dent J. 2014;217(10):559\u0026ndash;63.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAn SS, Choi YJ, Kim JY, Chung CJ, Kim KH. Risk factors associated with open gingival embrasures after orthodontic treatment. Angle Orthod. 2018;88(3):267\u0026ndash;74.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eZhang Y, Wang X, Wang J, et al. IPR treatment and attachments design in clear aligner therapy and risk of open gingival embrasures in adults. 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Angle Orthod. 2019;89(6):942\u0026ndash;5.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eNemec M, Bartholomaeus HM, Bertl H. Behaviour of Human Oral Epithelial Cells Grown on Invisalign(\u0026reg;) SmartTrack(\u0026reg;) Material. Mater (Basel). 2020;13(23):5311.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHugoson A, Norderyd O. Has the prevalence of periodontitis changed during the last 30 years. J Clin Periodontol. 2008;35(8 Suppl):338\u0026ndash;45.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eUribe F, Holliday B, Nanda R. Incidence of open gingival embrasures after mandibular incisor extractions: a clinical photographic evaluation. Am J Orthod Dentofac Orthop. 2011;139(1):49\u0026ndash;54.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eChang LC. The association between embrasure morphology and central papilla recession: a noninvasive assessment method. 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The effect of the distance from the contact point to the crest of bone on the presence or absence of the interproximal dental papilla. J Periodontol. 1992;63(12):995\u0026ndash;6.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eChang LC. Assessment of parameters affecting the presence of the central papilla using a non-invasive radiographic method. J Periodontol. 2008;79(4):603\u0026ndash;9.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHamp SE, Lundstr\u0026ouml;m F, Nyman S. Periodontal conditions in adolescents subjected to multiband orthodontic treatment with controlled oral hygiene. Eur J Orthod. 1982;4(2):77\u0026ndash;86.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eArtun J, Urbye KS. The effect of orthodontic treatment on periodontal bone support in patients with advanced loss of marginal periodontium. Am J Orthod Dentofac Orthop. 1988;93(2):143\u0026ndash;8.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eChow YC, Eber RM, Tsao YP, Shotwell JL, Wang HL. Factors associated with the appearance of gingival papillae. J Clin Periodontol. 2010;37(8):719\u0026ndash;27.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMalhotra R, Grover V, Bhardwaj A, Mohindra K. Analysis of the gingival biotype based on the measurement of the dentopapillary complex. J Indian Soc Periodontol. 2014;18(1):43\u0026ndash;7.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBurke S, Burch JG, Tetz JA. Incidence and size of pretreatment overlap and posttreatment gingival embrasure space between maxillary central incisors. Am J Orthod Dentofac Orthop. 1994;105(5):506\u0026ndash;11.\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"bmc-oral-health","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"ohea","sideBox":"Learn more about [BMC Oral Health](http://bmcoralhealth.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/ohea/default.aspx","title":"BMC Oral Health","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"Open gingival embrasures, black triangles, Orthodontic treatment, Clear aligners","lastPublishedDoi":"10.21203/rs.3.rs-5762697/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-5762697/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eBackground\u003c/h2\u003e \u003cp\u003eTo explore the incidence and risk factors of open gingival embrasures (OGEs) in the front region of adult none-extraction cases with clear aligner treatment (CAT).\u003c/p\u003e\u003ch2\u003eMethods\u003c/h2\u003e \u003cp\u003eEighty-two adult patients with non-extraction and CAT were included in this retrospective study. A total of 820 tooth sites were assessed for OGEs in intraoral photographs. These sites were categorized into nonoccurrence group and occurrence group. The parameters \u0026ndash; including crown shape, root angulation, distance between cementoenamel junction, and distance from interproximal contact point (ICP) to alveolar bone crest (ABC) \u0026ndash; were compared between occurrence group and nonoccurrence group using independent t-test and were further analyzed based on the severity. Logistic regression analysis was used to determine the significant risk factors of OGEs.\u003c/p\u003e\u003ch2\u003eResults\u003c/h2\u003e \u003cp\u003eThe overall incidence of OGEs was 13.4% in the maxilla and 30.7% in the mandible. The highest incidence was found between the mandibular central incisors, standing at 39.02%. Age, mandibular crowding, distance between adjacent maxillary teeth at the cementoenamel junction and distance from ICP to ABC in the maxilla and mandible have significant correlation with the occurrence of OGEs (\u003cem\u003eP\u003c/em\u003e\u0026lt;0.05). The tooth shape as well as the distance from ICP to ABC were correlated with the severity of OGEs between mandibular central incisors (\u003cem\u003eP\u003c/em\u003e\u0026lt;0.05).\u003c/p\u003e\u003ch2\u003eConclusions\u003c/h2\u003e \u003cp\u003eOGE is a common complication after CAT, adversely affecting the smiling esthetics. Clinicians should be well aware of risk factors, such as age, degree of dental crowding, and the distance from the ICP to ABC.\u003c/p\u003e","manuscriptTitle":"Risk factors for open gingival embrasures after clear aligners treatment: A retrospective study","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-01-09 04:52:05","doi":"10.21203/rs.3.rs-5762697/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-02-20T05:11:37+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-02-18T22:31:35+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-02-13T19:41:55+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"336216401175166093012990633921439022319","date":"2025-02-10T20:13:59+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"193361143619174870616234743033926757653","date":"2025-02-07T17:50:57+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-02-02T20:26:31+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2025-01-08T07:01:49+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-01-06T13:32:15+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-01-06T13:29:27+00:00","index":"","fulltext":""},{"type":"submitted","content":"BMC Oral Health","date":"2025-01-04T09:25:02+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"bmc-oral-health","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"ohea","sideBox":"Learn more about [BMC Oral Health](http://bmcoralhealth.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/ohea/default.aspx","title":"BMC Oral Health","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"f9af0b5a-0226-486c-9c4c-2007985884a2","owner":[],"postedDate":"January 9th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2025-04-14T16:15:34+00:00","versionOfRecord":{"articleIdentity":"rs-5762697","link":"https://doi.org/10.1186/s12903-025-05915-5","journal":{"identity":"bmc-oral-health","isVorOnly":false,"title":"BMC Oral Health"},"publishedOn":"2025-04-11 16:05:24","publishedOnDateReadable":"April 11th, 2025"},"versionCreatedAt":"2025-01-09 04:52:05","video":"","vorDoi":"10.1186/s12903-025-05915-5","vorDoiUrl":"https://doi.org/10.1186/s12903-025-05915-5","workflowStages":[]},"version":"v1","identity":"rs-5762697","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-5762697","identity":"rs-5762697","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}