Orthodontics & Craniofacial Research最新文献

{"title":"Does Current Evidence Support the Discussion Around the Guidance Theory? A Systematic Review and Meta-Analysis on the Association Between Maxillary Lateral Incisor Agenesis and Displacement or Impaction of the Permanent Canine.","authors":"Spyridon N Papageorgiou, Jadbinder Seehra, Martyn T Cobourne, Georgios Kanavakis","doi":"10.1111/ocr.12878","DOIUrl":"https://doi.org/10.1111/ocr.12878","url":null,"abstract":"<p><p>Palatal impaction of the maxillary canine is commonly considered as a genetic condition, while the lateral incisor root has been suggested to guide maxillary permanent canine eruption. This review assessed whether agenesis of the maxillary lateral incisor is associated with eruption disturbances of the maxillary canine (displacement or impaction). Unrestricted searches in six databases for observational case-control human studies until May 2024 assessing eruption disturbances of the permanent maxillary canine in conjunction with permanent maxillary lateral incisor agenesis were performed. Study selection, data extraction and risk-of-bias assessment with the Joanna Briggs Institute's tool were performed in duplicate. Random-effects meta-analyses of odds ratios (ORs) with their 95% confidence intervals (CIs) were performed, followed by meta-regressions and sensitivity analyses. Seventeen reports pertaining to 17 case-control studies were included covering 10,155 patients (11.6 year-old/46% male on average). Maxillary lateral incisor agenesis was associated with eruption disturbance of the maxillary canine (17 studies; OR = 3.88; 95% CI = 2.05-7.34; p < 0.001; I² = 58). Lateral incisor agenesis was more associated with canine displacement (7 studies; OR = 7.56; 95% CI = 2.10-27.18; p = 0.008; I² = 57) and to a lesser degree with canine impaction (10 studies; OR = 2.39; 95% CI = 1.28-4.48; p = 0.01). No significant effects of patient age or sex were seen, and the results were robust to study design and precision. The quality of evidence was low due to the inclusion of observational case-control studies with methodological issues and residual confounding. Evidence indicates that permanent maxillary lateral incisor agenesis is associated with eruption disturbances of the permanent maxillary canine, including mainly displacement, but also impaction. Trial Registration: PROSPERO database number: CRD42024549898.</p>","PeriodicalId":19652,"journal":{"name":"Orthodontics & Craniofacial Research","volume":" ","pages":""},"PeriodicalIF":2.4,"publicationDate":"2024-11-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142693343","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Radiographic Assessment of Root/Crown Ratio and Short Root Anomaly: A Retrospective Study in Chinese Population.","authors":"Yuer Ye, Yiqi Pan, Hui Zhang, Yani Chen, Guoli Yang, Zhiwei Jiang, Ying Wang","doi":"10.1111/ocr.12876","DOIUrl":"10.1111/ocr.12876","url":null,"abstract":"<p><strong>Objectives: </strong>Research suggested that racial and gender differences may exist in tooth root development and the prevalence of short root anomaly (SRA). However, data on Asian and specifically Chinese populations were limited. This retrospective study aimed to evaluate the prevalence of SRA and the characteristics of the root-to-crown ratio (R/C ratio) within the Chinese population.</p><p><strong>Materials and methods: </strong>Modified Lind's criteria were used to measure the crown and root lengths in permanent dentition. A total of 27 142 teeth from 1000 subjects were evaluated using panoramic radiographs. Fisher's exact test was employed to analyse gender differences in SRA. Paired-sample and independent-sample t tests were used to assess the characteristics of R/C ratios.</p><p><strong>Results: </strong>SRA was observed in 27 patients, with a prevalence of 2.7% and a tooth prevalence of 0.309%. Females had a significantly higher prevalence of SRA compared to males (p < 0.01). SRA was found exclusively in incisors (83.72%) and premolars (16.28%), with the maxillary central incisor being the most commonly affected tooth. Additionally, there were statistical differences in the R/C ratio based on gender and jaw position in the normal groups. The highest R/C ratios were observed in the mandibular second premolars, while the maxillary central incisors had the lowest ratios.</p><p><strong>Conclusions: </strong>SRA was relatively common in the Chinese population, and clinicians should be aware of its presence. It was more frequently observed in females and shows specificity in tooth position, with the maxillary central incisor being the most commonly affected tooth. Our study provides valuable insights for the early diagnosis and treatment of SRA in the Chinese population.</p>","PeriodicalId":19652,"journal":{"name":"Orthodontics & Craniofacial Research","volume":" ","pages":""},"PeriodicalIF":2.4,"publicationDate":"2024-11-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142648391","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Effects of Attachment Orientation and Designed Vertical Movement on Molar Distalisation With Clear Aligners: A Biomechanical Finite Element Study.","authors":"Jialun Li, Yi Yang, Xian He, Wenli Lai, Hu Long","doi":"10.1111/ocr.12875","DOIUrl":"10.1111/ocr.12875","url":null,"abstract":"<p><strong>Objective: </strong>This study aimed to evaluate the effects of molar attachment orientation and designed molar vertical movement on molar distalisation using clear aligners. Specifically, the study focused on the impact of vertical forces during upper second molar distalisation.</p><p><strong>Materials and methods: </strong>A three-dimensional finite element analysis was conducted to simulate upper molar distalisation using clear aligners. Four attachment orientations (0°, 45°, 90° and 135°) were designed. The study included three scenarios: distalisation alone; distalisation combined with intrusion; and distalisation combined with extrusion. The displacement tendencies and stress distribution on the second molar under various attachment orientations and vertical movements were analysed.</p><p><strong>Results: </strong>Molar distalisation resulted in buccal tipping, distal tipping and intrusion tendency in all models. The molar with 135° attachment orientation exhibited the most significant distal movement under intrusive force, while the one with 45° attachment showed the greatest distal movement under extrusive force. Additionally, greater distal movement was achieved with intrusive force compared to extrusive force, likely due to improved aligner grip on the attachments and teeth during intrusion.</p><p><strong>Conclusion: </strong>Attachment orientation significantly affects the effectiveness of molar distalisation and vertical movement with clear aligners. The 90° attachment group achieved the most effective molar distalisation. The 135° attachment is more effective under intrusive force, while the 45° attachment is preferable under extrusive force.</p>","PeriodicalId":19652,"journal":{"name":"Orthodontics & Craniofacial Research","volume":" ","pages":""},"PeriodicalIF":2.4,"publicationDate":"2024-11-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142648385","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Hyoid Bone Position and Upper Airway Morphology of Children With Obstructive Sleep Apnea: A Systematic Review and Meta-analysis.","authors":"Yaqi Li, Tingting Zhao, Peter Ngan, Susu Yi, Zeyu Wei, Fang Hua, Hong He","doi":"10.1111/ocr.12873","DOIUrl":"https://doi.org/10.1111/ocr.12873","url":null,"abstract":"<p><p>The objective of this systematic review was to summarise the existing evidence regarding hyoid bone position and upper airway morphology of children with obstructive sleep apnea (OSA). Electronic searches were carried out in PubMed, Embase, Web of Science, CINAHL and WorldCat databases without any restrictions on language from inception to March 2024. The studies which compared the hyoid bone position and upper airway morphology using lateral cephalograms between children with and without OSA will be included. The methodological quality of the included studies was assessed using Newcastle-Ottawa Scale, and the meta-analysis was conducted utilising random-effects model. Twelve cross-sectional studies and one case-control study were included. One study was rated as low quality, three as medium quality, five as high quality, and four as very high quality. Meta-analysis showed that compared to healthy children, children with OSA tended to have increased distance between hyoid bone and mandibular plane (Hy-MP, MD: 3.33, 95% CI: 1.90 to 4.77, p < 0.00001, I² = 72%), increased distance between hyoid bone and cervical vertebra (Hy-C3, MD: 1.54, 95% CI: 0.62 to 2.46, p = 0.001, I² = 68%), and a smaller airway space behind the soft palate (U-MPW, MD: -3.07, 95% CI: -4.76 to -1.38, p = 0.0004, I² = 68%). Whereas there was no significant difference in inferior posterior airway space between children with OSA and healthy controls (IPAS, MD: -1.51, 95% CI: -3.37 to 0.35, p = 0.11, I² = 71%). In children with OSA, the hyoid bone may exhibit a more anterior and inferior position and the airway posterior to the soft palate demonstrated a narrower dimension. Registration: PROSPERO (CRD42024528171).</p>","PeriodicalId":19652,"journal":{"name":"Orthodontics & Craniofacial Research","volume":" ","pages":""},"PeriodicalIF":2.4,"publicationDate":"2024-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142625168","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Inhibition of Orthodontic Relapse by Local Application of Simvastatin-Loaded Gelatin Hydrogel in a Rabbit Model.","authors":"Niswati Fathmah Rosyida, Ika Dewi Ana, Pinandi Sri Pudyani, Akhmad Kharis Nugroho","doi":"10.1111/ocr.12877","DOIUrl":"https://doi.org/10.1111/ocr.12877","url":null,"abstract":"<p><strong>Objectives: </strong>This study aims to determine the effect of gelatin-simvastatin hydrogel application on bone remodelling during relapse.</p><p><strong>Materials and methods: </strong>Twenty-four rabbits (Oryctolagus cuniculus) were divided into a control group (n = 12) and a treatment group (n = 12). The lower incisors were subjected to orthodontic force and moved distally by an open coil spring. The force (50 cN) was extended for 1 week and retained in a new position for 2 weeks (stabilisation period). The treatment group received a local gelatin-simvastatin hydrogel administration during stabilisation, and the control group received only gelatin hydrogel. The springs were debonded after the stabilisation phase from both groups to facilitate a relapse. The percentage of relapse was measured in a model study using digital callipers. Levels of OPG and RANKL were analysed using ELISA.</p><p><strong>Results: </strong>The local application of gelatin-simvastatin hydrogel in the treatment group significantly decreases the relapse percentage and RANKL level. Additionally, the gelatin-simvastatin hydrogel significantly increases the level of OPG and ratio of OPG/RANKL.</p><p><strong>Conclusions: </strong>Applying gelatin-simvastatin hydrogel in the retention period can induce bone formation, inhibit orthodontic relapse and increase tooth stability (in vivo).</p>","PeriodicalId":19652,"journal":{"name":"Orthodontics & Craniofacial Research","volume":" ","pages":""},"PeriodicalIF":2.4,"publicationDate":"2024-11-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142625297","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Sustained Protraction Increases Lengthening of the Mandibular Condylar Process Whilst Changes Its Growth Direction in a Rat Model.","authors":"Yuan Li, Naiqi Liao, Ruyi Wang, Lingli Pang, Hengyi Fu, Shijia Li, Wei Zheng, Yu Li","doi":"10.1111/ocr.12869","DOIUrl":"https://doi.org/10.1111/ocr.12869","url":null,"abstract":"<p><strong>Objective: </strong>In Class II elastics treatment, the mandible is subject to sustained protraction. The study aimed to investigate the morphological and histological changes resulting from sustained mandibular protraction, through establishment of a novel model in rat.</p><p><strong>Materials and methods: </strong>Forty-eight 4-week-old male Sprague-Dawley rats were randomly divided into three groups, including the 50 and 100 cN protraction groups, and the control. In the two protraction groups, NiTi coil springs were fixed between the metal bands on the maxillary incisors and mandibular molars to pull the mandible forward. CBCT scans were taken immediately before (T0), 2 weeks (T1) and 4 weeks (T2) after the traction. Histological and immunohistochemical analyses were performed at T1 and T2.</p><p><strong>Results: </strong>Increase of the condylar process length and angular process length were significantly larger in the two protraction groups than that in the control; however, the condylar process angle (∠CPA) was significantly reduced by the protraction at T2, leading to decreased condylar height. The protraction decreased the condylar cartilage thickness at T1, which recovered to the control level at T2, with no significant changes detected in the expression of SRY-related high mobility group-box gene 9 (SOX9) and type II collagen (COL II), two chondrogenic markers.</p><p><strong>Conclusion: </strong>The established rat model is manoeuvrable and reliable, which exerts sustained and measurable mandibular protraction. The sustained protraction increases the lengthening of the mandibular condylar process, but alters its growth direction by causing it to turn downwards.</p>","PeriodicalId":19652,"journal":{"name":"Orthodontics & Craniofacial Research","volume":" ","pages":""},"PeriodicalIF":2.4,"publicationDate":"2024-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142605101","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Role of Nasopharyngeal Airway in Management of Craniofacial Syndrome-Associated Upper Airway Obstruction in Children.","authors":"Samara Thambar, Matthew D Wong, Sandra Schilling, Nitin Kapur","doi":"10.1111/ocr.12872","DOIUrl":"10.1111/ocr.12872","url":null,"abstract":"<p><strong>Introduction: </strong>Upper airway obstruction (UAO) management in children, particularly those with associated anatomical mid-face structural differences, poses a significant challenge. This study describes using a nasopharyngeal airway (NPA) in managing infants with severe upper airway obstruction.</p><p><strong>Methods: </strong>Infants discharged home from Queensland Children's Hospital with an NPA in situ for the management of upper airway obstruction were retrospectively evaluated for clinical and demographic parameters, underlying diagnoses and respiratory support, including NPA insertion details and comorbidities.</p><p><strong>Results: </strong>Sixty-seven children (24 male) were included with a median age at NPA insertion of 24 (IQR 7-59) days and a median duration of NPA use of 229.1 (IQR 151.50-297.75) days. Fifty-two (77.6%) had Pierre Robin sequence. Other diagnoses included CHARGE syndrome, Treacher Collins syndrome, Stickler syndrome, Crouzon syndrome, Bohring-Opitz syndrome, isolated cleft palate, Beckwith-Wiedemann syndrome, Chromosome 3 deletion and VACTERL association. Four infants required tracheostomy, and no complications related to NPA use were reported. Those with oximetry and polysomnography data showed improving indices following NPA insertion [pre NPA median (IQR) SpO₂: 95.9% (94.73-97.73), AHI: 51.40 (44.50-69.45), OAHI 65.9 (56.45-73.35) and TcCO₂ (mmHg) 65.70 (61.95-67.30) vs. post-NPA median (IQR) SpO₂: 97.1% (96.19-97.9), AHI: 12.20 (11.25-24.35), OAHI 10.20 (6.12-5.62) and TcCO₂ (mmHg) 52.40 (47.90-58.40)].</p><p><strong>Conclusion: </strong>Our findings highlight the effectiveness and safety of NPA as a noninvasive management option for severe upper airway obstruction in children, particularly in those with anatomical midface structural differences. Further research and larger studies are warranted to confirm these findings and optimise management strategies for these patients.</p>","PeriodicalId":19652,"journal":{"name":"Orthodontics & Craniofacial Research","volume":" ","pages":""},"PeriodicalIF":2.4,"publicationDate":"2024-11-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142584002","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Effects of Active Presurgical Orthopaedics Appliances in Infants With Complete Unilateral Cleft Lip and 'T-Shaped' Alveolus: A Preliminary Study.","authors":"Trang Thi-Huyen Nguyen, Thuy-Trang Thi Ho, Dau Van Nguyen, Nam Cong-Nhat Huynh","doi":"10.1111/ocr.12870","DOIUrl":"https://doi.org/10.1111/ocr.12870","url":null,"abstract":"<p><strong>Objectives: </strong>This study aimed to assess the efficacy of active presurgical orthopaedics appliances in infants presenting with complete unilateral cleft lip and overlapped alveolus (T-shaped alveolus).</p><p><strong>Materials and methods: </strong>A retrospective and prospective longitudinal study was performed. Infants diagnosed with complete unilateral cleft lip and overlapped alveolus, received treatment with the active presurgical orthopaedics appliances from June 2020 to June 2023, at Children's Hospital 1, Ho Chi Minh City. The treatment duration averaged 3 months. Pre- and posttreatment casts of noses and alveolus were scanned using TRIOS3 Wireless intraoral scanner (3Shape, Denmark) and analysed with Slicer 5.2.2 software. There were 16 quantitative variables. A pair t-test and Wilcoxon signed ranks were used for analysis. The statistical significance was adopted as p < 0.05.</p><p><strong>Results: </strong>A total 40 patients (17 males, 23 females, mean age 23.85 ± 19.22 days) were evaluated. After treatment, the nostril height increased by 2.62 ± 0.22 mm and the deviation columella decreased by -23.45° ± 2.29°. There was a reduction in cleft gap (-3.77 ± 2.01 mm), and in the overlap of alveolus (-3.71 ± 1.83 mm), the growth of cleft segment increased by 2.27 ± 2.00 mm, while the rotation of the noncleft side alveolus decreased by -5.29° ± 5.31°. The changes were statistically significant (p < 0.001).</p><p><strong>Conclusions: </strong>Active presurgical orthopaedics appliances improved the nasal deformity and overlapped alveolus morphology in infants with complete unilateral cleft lip and T-shaped alveolus.</p>","PeriodicalId":19652,"journal":{"name":"Orthodontics & Craniofacial Research","volume":" ","pages":""},"PeriodicalIF":2.4,"publicationDate":"2024-10-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142546652","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Efficacy of Clear Aligner Therapy for the Treatment of Anterior Open Bite in Adults: A Systematic Review and Meta-Analysis.","authors":"Erika Correa, Dimitrios Michelogiannakis, Abdul Basir Barmak, Paul Emile Rossouw, Fawad Javed","doi":"10.1111/ocr.12868","DOIUrl":"https://doi.org/10.1111/ocr.12868","url":null,"abstract":"<p><p>The objective of the present systematic review and meta-analysis was to assess the effectiveness of clear aligner therapy (CAT) for the treatment of anterior open bite (AOB) in adults. The focused question was \"Is CAT effective for the management of AOB in adults?\". Databases were searched without time and language barriers up to and including August 2024 based on pre-specified eligibility criteria. Risk of Bias (RoB) assessment was performed using the Risk-of-Bias-In-Non-randomised-Studies-of-Intervention (ROBINS-I) tool. Meta-analyses were conducted using a random effects model (REM) for change in AOB and cephalometric measurements with an evaluation of the mean difference (MD) and/or standardised mean difference (SMD). The Grades of Recommendation, Assessment, Development and Evaluation (GRADE) tool was used to assess the quality of evidence. Publication bias was assessed using Funnel plots and Egger's regression test. There were 14 studies included in the qualitative assessment and 12 in the meta-analysis. The RoB was moderate in 13 studies and low in one. The meta-analysis showed significant AOB correction with CAT [(MD) = 2.76 mm, 95% confidence interval (CI): 2.23-3.28] due to maxillary and mandibular incisor extrusion (MD = 0.85 mm, CI: 0.43-1.26 and MD = 0.86 mm, CI: 0.29-1.44, respectively). There were no significant changes identified for maxillary and mandibular molar intrusion or changes in the mandibular plane angle (MPA). The level of confidence was high for AOB correction, incisor extrusion, and molar intrusion and low for MPA. CAT leads to a significant correction of AOB of approximately 2.76 mm, which can be mainly attributed to incisor extrusion.</p>","PeriodicalId":19652,"journal":{"name":"Orthodontics & Craniofacial Research","volume":" ","pages":""},"PeriodicalIF":2.4,"publicationDate":"2024-10-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142505335","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The Mechanical Properties of Orthodontic Aligners of Clear Aligner After Intraoral Use in Different Time Periods.","authors":"Kalliopi Siotou, Theofanis Chountalas, Athanasios Katsavrias, Charalampos Siotos, Konstantinos Mpalias, Dionysios Semitekolos, Constantinos Charitidis, Apostolos I Tsolakis","doi":"10.1111/ocr.12867","DOIUrl":"https://doi.org/10.1111/ocr.12867","url":null,"abstract":"<p><strong>Objective: </strong>Although the technique of orthodontic aligners has risen in popularity, their mechanical properties have not been thoroughly investigated. The aim of this study was to evaluate the mechanical properties of the orthodontic aligners Clear Aligner after intraoral use for 7, 10 and 14 days, and to compare them with as-received aligners (0 days). It was also sought to examine the properties of the unprocessed raw material (polyethylene glycol terephthalate) used to manufacture these aligners.</p><p><strong>Materials/methods: </strong>Thirty-two aligners by four patients were evaluated and studied at 0, 7, 10, 14 days of use. Each aligner was divided into three segments (two posterior and one anterior), which resulted in 96 samples. Also, 16 samples of unprocessed material were studied. For all samples, elastic modulus, ultimate tensile stress (UTS) and yield stress were calculated by conducting tensile testing. Additionally, material hardness was tested. The two-tailed Mann-Whitney test was performed, having set the level of significance at p = 0.05.</p><p><strong>Results: </strong>Analysis of the measurements indicated a statistically significant decrease in elastic modulus between days 0 and 14 of use, of UTS between days 0 and 7, 7 and 10, and of yield stress between days 0 and 7. For hardness, in every period, posterior segments demonstrated significantly higher values than anterior segments. All properties of the unprocessed material were statistically significantly higher than the processed samples.</p><p><strong>Conclusions: </strong>The unprocessed material presented significant differences in every property tested in comparison to the processed aligners. The processed material showed further deterioration over time during use. The present study provides evidence that thermoforming and ageing affect the mechanical properties of the aligners.</p>","PeriodicalId":19652,"journal":{"name":"Orthodontics & Craniofacial Research","volume":" ","pages":""},"PeriodicalIF":2.4,"publicationDate":"2024-10-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142505336","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}