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Buch FO, Stokbro K. Accuracy and stability of the condyle position after orthognathic surgery: A retrospective study. J Craniomaxillofac Surg 2024; 52:240-245. [PMID: 38172014 DOI: 10.1016/j.jcms.2023.12.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2022] [Revised: 06/21/2023] [Accepted: 12/20/2023] [Indexed: 01/05/2024] Open
Abstract
The purpose of this study was to evaluate the accuracy and stability of condylar positioning in patients treated with bimaxillary procedures compared with patients treated with maxillary procedures alone. All patients had undergone treatment at Odense University Hospital and were treated with inferior maxillary procedures. The primary outcome was changes in condyle position and the primary predictor variable was time: pre-operative (T0) measurements to 1-week post-operative (T1) and 1-year post-operative (T2) measurements. Condyle movement was measured using dual voxel-based alignment. Sixteen patients were included. Seven patients underwent solitary maxillary procedure and 9 patients bimaxillary procedure. Bimaxillary procedures overall showed a condyle positional change in pitch from T0 to T1 and T1 to T2 compared to maxillary procedures alone. Condylar translation was stable despite large differences in positioning. Compared to solitary maxillary procedures, bimaxillary procedures showed a statistically significant anterocranial rotation at 1-week follow-up movement (3.95° vs. -0.95°; SD 3,74 vs 1,05; P value = 0.000) and an additional statistically significant anterocranial movement at 1 year after surgery (4.89° vs 0.60°; SD 3,82 vs 0,92; P value = 0.000). In conclusion a need for greater anterocranial stability of the sagittal split osteotomy than that provided by 3 bicortically fixated screws alone might be indicated.
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Affiliation(s)
- Frederik Ohm Buch
- Department of Oral and Maxillofacial Surgery, Odense University Hospital, Denmark
| | - Kasper Stokbro
- Consultant Surgeon & Head of Research, Department of Oral and Maxillofacial Surgery, Odense University Hospital, Oral and Maxillofacial Research Department, Clinical Institute, University of Southern Denmark, Denmark.
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Larsen MM, Buch FO, Tour G, Azarmehr I, Stokbro K. Training arthrocentesis and arthroscopy: Using surgical navigation to bend the learning curve. Journal of Oral and Maxillofacial Surgery, Medicine, and Pathology 2023. [DOI: 10.1016/j.ajoms.2023.03.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/29/2023]
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Azarmehr I, Stokbro K, Bell RB, Thygesen T. Contemporary Techniques in Orbital Reconstruction: A Review of the Literature and Report of a Case Combining Surgical Navigation, Computer-Aided Surgical Simulation, and a Patient-Specific Implant. J Oral Maxillofac Surg 2020; 78:594-609. [DOI: 10.1016/j.joms.2019.11.005] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2019] [Revised: 11/03/2019] [Accepted: 11/04/2019] [Indexed: 11/15/2022]
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Stokbro K, Thygesen T, Marcussen L. Inferior Maxillary Repositioning Remains Stable 1 Year After Surgery but Entails a High Risk of Osteosynthesis Failure. J Oral Maxillofac Surg 2019; 78:118-126. [PMID: 31560868 DOI: 10.1016/j.joms.2019.08.014] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2019] [Revised: 08/12/2019] [Accepted: 08/14/2019] [Indexed: 11/18/2022]
Abstract
PURPOSE Inferior maxillary repositioning has continued to be among the most unstable orthognathic procedures. The overall purpose of the present study was to measure skeletal stability after inferior maxillary repositioning. MATERIALS AND METHODS We implemented a retrospective cohort study. The study cohort was derived from all orthognathic patients who had undergone treatment from January 2011 to December 2013 in Odense University Hospital. The inclusion criteria were orthognathic surgery with inferior maxillary repositioning in patients without maxillary segmentation or cleft lip/palate. The exclusion criteria were nonattendance at follow-up visits or requiring reoperation before the 1-year follow-up point. The primary predictor variable was the time from the 1-week follow-up examination to the 1-year follow-up examination. The primary outcome variable was maxillary skeletal movement. The other variables of interest were age, gender, preoperative occlusal relationship, maxillary movement obtained, and surgery type (mono- or bimaxillary procedure). Skeletal stability was measured at the centroid, anterior, and posterior nasal spines using the semiautomatic measurement technique. Skeletal stability was clinically defined as less than 2 mm of movement in any direction. The positive directions for the 3 axes were right, anterior, and superior. The data were analyzed using mixed model linear regression analysis and 1-sample t tests. RESULTS A total of 17 patients were included in the present study (mean age, 28 years; female gender, 35%; bimaxillary surgery, 59%). Inferior maxillary repositioning was stable with less than 0.3 mm mean skeletal movement in any direction. Only 1 patient had experienced a relapse of more than 1 mm in the posterior direction; no movement exceeded 2 mm. However, 3 patients were excluded from the present analysis, because they had required reoperation during the first year after surgery for osteosynthesis failure. CONCLUSIONS Inferior maxillary repositioning was stable during the first year after surgery; however, the complication rate was high (15%). Thus, this procedure might still benefit from the use of more rigid patient-specific printed plates to increase postoperative stability.
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Affiliation(s)
- Kasper Stokbro
- Consultant Surgeon, Department of Oral and Maxillofacial Surgery, Odense University Hospital, Odense, Denmark; and PhD Fellow, Department of Clinical Institute, Faculty of Health, University of Southern Denmark, Odense, Denmark.
| | - Torben Thygesen
- Consultant Surgeon, Department of Oral and Maxillofacial Surgery, Odense University Hospital, Odense, Denmark
| | - Lillian Marcussen
- Associate Professor, Department of Oral and Maxillofacial Surgery, Odense University Hospital, Odense, Denmark
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Stokbro K, Liebregts J, Baan F, Bell RB, Maal T, Thygesen T, Xi T. Does Mandible-First Sequencing Increase Maxillary Surgical Accuracy in Bimaxillary Procedures? J Oral Maxillofac Surg 2019; 77:1882-1893. [PMID: 31034793 DOI: 10.1016/j.joms.2019.03.023] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2018] [Revised: 03/19/2019] [Accepted: 03/19/2019] [Indexed: 11/29/2022]
Abstract
PURPOSE In bimaxillary procedures, it is important to know how the chosen sequence affects the surgical outcome. The purpose of this study was to explore whether the theoretical advantages of using the mandible-first procedure were supported by clinical data. MATERIALS AND METHODS The authors performed a retrospective investigation on a cohort compiled from 3 published retrospective studies. The sample was composed of patients treated at the Radboud University Nijmegen Medical Centre (Nijmegen, the Netherlands) from 2010 to 2014 and the Odense University Hospital (Odense, Denmark) from 2011 to 2015. The inclusion criterion was bimaxillary surgery without maxillary segmentation. The exclusion criterion was lack of a virtual surgical plan. The primary outcome variable was surgical accuracy, defined as the mean difference between the obtained outcome and the virtual surgical plan. The primary predictor variable was the comparison between mandible-first and maxilla-first sequencing. Secondary predictors were inferior maxillary repositioning and counterclockwise (CCW) rotation. The confounding variable was the virtually planned reposition. Results were analyzed by mixed-model regression encompassing all variables, followed by a detailed analysis of positive results using 2-sample t tests. RESULTS Overall, 145 patients were included for analysis (98 women; mean age, 28 years). Operating on the mandible first notably influenced maxillary positioning and placed the maxilla 1.5 mm posterior and with 1.4° of CCW rotation compared with virtual surgical planning. The interaction of surgical sequence with maxillary rotation showed similar surgical accuracy between maxilla-first surgery with clockwise rotation and mandible-first surgery with CCW rotation. Inferior maxillary repositioning resulted in the maxilla being placed 1.7 mm (maxilla-first sequence) and 2.0 mm (mandible-first sequence) posterior to the planned position. CONCLUSION Surgical accuracy was considerably influenced by sequencing in bimaxillary procedures. It remains important to know how the chosen sequence affects the surgical outcome so that the virtual surgical plan can be adjusted accordingly.
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Affiliation(s)
- Kasper Stokbro
- PhD Fellow and Oral and Maxillofacial Surgical Resident, Department of Oral and Maxillofacial Surgery, Odense University Hospital, Odense, Denmark.
| | - Jeroen Liebregts
- PhD Fellow and Oral and Maxillofacial Surgical Resident, Department of Oral and Maxillofacial Surgery, Radboud University Nijmegen Medical Centre, Nijmegen, the Netherlands
| | - Frank Baan
- PhD Fellow, Radboudumc 3D Lab and Department of Orthodontics and Craniofacial Biology, Radboud University Medical Centre, Nijmegen, the Netherlands
| | - R Bryan Bell
- Medical Director, Providence Oral, Head and Neck Cancer Program and Clinic, Providence Cancer Center, Portland, OR
| | - Thomas Maal
- Associate Professor, Radboudumc 3D Lab, Radboud University Nijmegen Medical Centre, Nijmegen, the Netherlands
| | - Torben Thygesen
- Associate Professor, Department of Oral and Maxillofacial Surgery, Odense University Hospital, Odense, Denmark
| | - Tong Xi
- Oral and Maxillofacial Surgeon, Department of Oral and Maxillofacial Surgery, Radboud University Nijmegen Medical Centre, Nijmegen, the Netherlands
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Maribo Y, Stokbro K, Aagaard E, Larsen SR, Thygesen T. Synovial Cysts in the Temporomandibular Joint: a Case Report and Critical Review of the Literature. J Oral Maxillofac Res 2019; 10:e4. [PMID: 31069041 PMCID: PMC6498815 DOI: 10.5037/jomr.2019.10104] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2018] [Accepted: 01/19/2019] [Indexed: 11/25/2022]
Abstract
Background Synovial cysts of the temporomandibular joint are rare and treatment is based on consensus from cases reporting unilateral successful outcomes. A patient with a synovial cyst is presented, treated with successful surgical excision of the cyst, but without remission of joint symptoms. Furthermore, the case is supplemented by a critical, literature review. Methods This case report deals with a patient with a synovial cyst that presented with temporomandibular joint (TMJ) pain and reduced mouth opening. Magnetic resonance imaging verified a TMJ cyst. Results Surgical excision removed the synovial cyst, and the patient was followed-up for 4 years, with no recurrence of the cyst. Despite successful excision of the cyst, the symptoms did not subside, and the patient is still in treatment. The critical, literature review found 23 case reports describing 24 synovial cysts. In addition, 4 cases were included as their synovial cysts were erroneously described as ganglion cysts. In 4 cases, histological diagnosis could not be confirmed, and they were excluded. All cases described treatment by surgical excision without recurrence. The reported median follow-up was 10 months and postoperative TMJ symptoms were rarely examined or described. Conclusions The temporomandibular joint symptoms may persist despite successful removal of the synovial cyst. Furthermore, the 4 identified synovial cysts, mislabelled as ganglion cysts, represents almost a quarter of the cases of the reported synovial cysts. Correct labelling and reporting of synovial cysts are still imperative to describe the diverse aspects of treatment outcomes following surgical excision.
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Affiliation(s)
- Ynn Maribo
- Department of Oral and Maxillofacial Surgery, Odense University HospitalDenmark
| | - Kasper Stokbro
- Department of Oral and Maxillofacial Surgery, Odense University HospitalDenmark.,Clinical institute, Faculty of Health, University of Southern DenmarkDenmark
| | - Esben Aagaard
- Department of Oral and Maxillofacial Surgery, Odense University HospitalDenmark
| | | | - Torben Thygesen
- Department of Oral and Maxillofacial Surgery, Odense University HospitalDenmark
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Stokbro K, Borg SW, Andersen MØ, Thygesen T. Patient-specific 3D printed plates improve stability of Le Fort 1 osteotomies in vitro. J Craniomaxillofac Surg 2019; 47:394-399. [DOI: 10.1016/j.jcms.2018.12.015] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2018] [Revised: 11/04/2018] [Accepted: 12/21/2018] [Indexed: 11/25/2022] Open
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Jakobsen C, Stokbro K, Kier-Swiatecka E, Ingerslev J, Thorn J. Autotransplantation of premolars: does surgeon experience matter? Int J Oral Maxillofac Surg 2018; 47:1604-1608. [DOI: 10.1016/j.ijom.2018.08.003] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2018] [Revised: 06/26/2018] [Accepted: 08/06/2018] [Indexed: 11/30/2022]
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Stokbro K, Bell RB, Thygesen T. Patient-Specific Printed Plates Improve Surgical Accuracy In Vitro. J Oral Maxillofac Surg 2018; 76:2647.e1-2647.e9. [PMID: 30196082 DOI: 10.1016/j.joms.2018.08.002] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2018] [Revised: 08/02/2018] [Accepted: 08/03/2018] [Indexed: 11/28/2022]
Abstract
PURPOSE It remains unclear to what extent patient-specific printed plates can improve surgical outcomes in orthognathic procedures. This study aimed to quantify the surgical accuracy of patient-specific printed plates in vitro and to compare the results with patients' actual surgical outcomes. PATIENTS AND METHODS This in vitro study enrolled 20 postoperative orthognathic surgical patients, all treated with inferior maxillary repositioning. The preoperative midfaces were re-created in a 3-dimensionally printed model. The osteotomy and screw holes were placed at prespecified positions using a 3-dimensional guide. The dental segment was repositioned by means of the patient-specific plates. The primary outcome was the mean reposition at 3 dental reference points. The primary predictor variable was the obtained surgical reposition in vitro compared with the virtual surgical plan. Confounding variables were gender, age, occlusion, and bimaxillary surgery. The secondary outcome was surgical accuracy, and the secondary predictor was the in vitro outcomes versus the patients' surgical outcomes. Surgical accuracy was defined as the difference between the obtained reposition and the virtual surgical plan on a continuous scale. The differences were recorded in 3 dimensions according to the positive value of the 3 axes: right, anterior, and posterior. The results were analyzed using mixed-model regression and 1-sample t tests. RESULTS In the 20 patients (age, 18 to 64 years; 40% of patients were women), the mean planned reposition was 2.9 mm anterior and 1.8 mm inferior. In all models, the osteotomy edge was rounded off to position the plate in the predetermined position. Overall, the maxilla was positioned 0.5 mm anterior and 0.3 mm inferior to the planned position using patient-specific plates. CONCLUSIONS The patient-specific plates positioned the maxilla in close approximation to the planned position without surgically relevant differences. The osteotomy edge must be carefully inspected for interference with the patient-specific plates to avoid displacement of the planned maxillary repositioning.
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Affiliation(s)
- Kasper Stokbro
- PhD Fellow and Oral and Maxillofacial Surgical Resident, Department of Oral and Maxillofacial Surgery, Odense University Hospital, Odense, Denmark.
| | - R Bryan Bell
- Medical Director, Providence Oral, Head and Neck Cancer Program and Clinic, Providence Cancer Center, Portland, OR
| | - Torben Thygesen
- Head of Department, Department of Oral and Maxillofacial Surgery, Odense University Hospital, Odense, Denmark
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Stokbro K, Thygesen T. A 3-Dimensional Approach for Analysis in Orthognathic Surgery—Using Free Software for Voxel-Based Alignment and Semiautomatic Measurement. J Oral Maxillofac Surg 2018; 76:1316-1326. [DOI: 10.1016/j.joms.2017.11.010] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2017] [Revised: 10/04/2017] [Accepted: 11/04/2017] [Indexed: 10/18/2022]
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Stokbro K, Aagaard E, Torkov P, Marcussen L, Bell RB, Thygesen T. Surgical Splint Design Influences Transverse Expansion in Segmental Maxillary Osteotomies. J Oral Maxillofac Surg 2017; 75:1249-1256. [DOI: 10.1016/j.joms.2016.12.042] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2016] [Revised: 12/28/2016] [Accepted: 12/28/2016] [Indexed: 11/26/2022]
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Azarmehr I, Stokbro K, Bell RB, Thygesen T. Surgical Navigation: A Systematic Review of Indications, Treatments, and Outcomes in Oral and Maxillofacial Surgery. J Oral Maxillofac Surg 2017; 75:1987-2005. [PMID: 28193444 DOI: 10.1016/j.joms.2017.01.004] [Citation(s) in RCA: 87] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2016] [Revised: 12/26/2016] [Accepted: 01/09/2017] [Indexed: 12/20/2022]
Abstract
PURPOSE This systematic review investigates the most common indications, treatments, and outcomes of surgical navigation (SN) published from 2010 to 2015. The evolution of SN and its application in oral and maxillofacial surgery have rapidly developed over recent years, and therapeutic indications are discussed. MATERIALS AND METHODS A systematic search in relevant electronic databases, journals, and bibliographies of the included articles was carried out. Clinical studies with 5 or more patients published between 2010 and 2015 were included. Traumatology, orthognathic surgery, cancer and reconstruction surgery, skull-base surgery, and foreign body removal were the areas of interests. RESULTS The search generated 13 articles dealing with traumatology; 5, 6, 2, and 0 studies were found that dealt with the topics of orthognathic surgery, cancer and reconstruction surgery, skull-base surgery, and foreign body removal, respectively. The average technical system accuracy and intraoperative precision reported were less than 1 mm and 1 to 2 mm, respectively. In general, SN is reported to be a useful tool for surgical planning, execution, evaluation, and research. The largest numbers of studies and patients were identified in the field of traumatology. Treatment of complex orbital fractures was considerably improved by the use of SN compared with traditionally treated control groups. CONCLUSIONS SN seems to be a very promising addition to the surgical toolkit. Planning details of the surgical procedure in a 3-dimensional virtual environment and execution with real-time guidance can significantly improve precision. Among factors to be considered are the financial investments necessary and the learning curve.
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Affiliation(s)
- Iman Azarmehr
- Resident, Department of Oral and Maxillofacial Surgery, Odense University Hospital, Odense, Denmark.
| | - Kasper Stokbro
- Resident, Department of Oral and Maxillofacial Surgery, Odense University Hospital, Odense, Denmark
| | - R Bryan Bell
- Director, Providence Oral, Head and Neck Cancer Program and Clinic, Providence Cancer Center; Attending Surgeon, Trauma Service, Legacy Emanuel Medical Center; and Consultant, Head and Neck Institute, Portland, OR
| | - Torben Thygesen
- Head of Department, Department of Oral and Maxillofacial Surgery, Odense University Hospital, Odense, Denmark
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Abstract
Reduced volume of the internal skeletal dimensions of the face is 1 of the main causes of obstructive sleep apnea, and attention to patients' airways is necessary when planning orthognathic treatment. This study aims to describe changes in upper airway volume following virtually planned orthognathic surgery.A retrospective pilot study was designed with 30 randomly selected patients (10 men and 20 women, aged 23.1 ± 6.8 years, molar-relations: 15 neutral, 8 distal, and 7 mesial). Cone-beam computed tomography scans were performed before surgery and 1 week following surgery. The authors did total upper airway volume measurements and obtained 1-mm slices at vertical levels in the velo-, oro-, and hypopharynx and at the smallest visible cross-section.Measurements before and after surgery were compared using Student t test.After orthognathic surgery, the minimum cross-sectional area at the vertical level increased from 83 mm ± 33 before surgery to 102 mm ± 36 after surgery (P = 0.019). In patients with neutral and distal occlusions, the minimum cross-sectional slice volume increased in 87% but in only 57% with mesial occlusion.The present findings suggest that orthognathic surgery increases upper airway volume parameters, but a few patients have continued impairment of the airways following orthognathic surgery. Further studies are needed to confirm an individual surgical planning approach that potentially could bring the minimum cross sectional area out of the risk zone.
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Affiliation(s)
- Lillian Marcussen
- Department of Oral and Maxillofacial Surgery, Odense University Hospital, Odense, Denmark
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Stokbro K, Aagaard E, Torkov P, Bell R, Thygesen T. Surgical accuracy of three-dimensional virtual planning: a pilot study of bimaxillary orthognathic procedures including maxillary segmentation. Int J Oral Maxillofac Surg 2016; 45:8-18. [DOI: 10.1016/j.ijom.2015.07.010] [Citation(s) in RCA: 59] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2014] [Revised: 05/31/2015] [Accepted: 07/16/2015] [Indexed: 11/29/2022]
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Stokbro K, Aagaard E, Torkov P, Bell R, Thygesen T. Virtual planning in orthognathic surgery. Int J Oral Maxillofac Surg 2014; 43:957-65. [DOI: 10.1016/j.ijom.2014.03.011] [Citation(s) in RCA: 123] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2013] [Revised: 03/14/2014] [Accepted: 03/19/2014] [Indexed: 10/25/2022]
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Affiliation(s)
- M. Stilling
- Nano-Science Center, Copenhagen University, Universitetsparken 5D, DK-2100, Copenhagen, Denmark
| | - K. Stokbro
- Nano-Science Center, Copenhagen University, Universitetsparken 5D, DK-2100, Copenhagen, Denmark
| | - K. Flensberg
- Nano-Science Center, Copenhagen University, Universitetsparken 5D, DK-2100, Copenhagen, Denmark
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Abstract
The dimensions of electronic devices are rapidly decreasing and there is a need for a new generation of modeling tools that can accurately calculate the electrical properties of devices where atomic scale details and quantum effects are important. A promising framework for such calculations is density functional theory within the non-equilibrium Green's function formalism (NEGF-DFT). In this paper we present the basic framework and applications of the formalism. The applications include the calculation of the I-V characteristics of a single molecule connected with gold electrodes and the spin-dependent electron transport through a magneto-tunnel junction consisting of MgO layers sandwiched between Fe electrodes. For the formalism to be applied in semiconductor device modeling it needs to be able to handle many thousands of atoms. We discuss new developments and future aspects of the method important for semiconductor device modeling; in particular we show that for important classes of systems the approach scales linearly with the system size.
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Affiliation(s)
- K Stokbro
- Department of Computer Science, University of Copenhagen, Universitetsparken 1, DK-2100 Copenhagen, Denmark
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Nielsen SK, Brandbyge M, Hansen K, Stokbro K, Van Ruitenbeek JM, Besenbacher F. Current-voltage curves of atomic-sized transition metal contacts: an explanation of why Au is Ohmic and Pt is not. Phys Rev Lett 2002; 89:066804. [PMID: 12190601 DOI: 10.1103/physrevlett.89.066804] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/07/2002] [Indexed: 05/23/2023]
Abstract
We present an experimental study of current-voltage (I-V) curves on atomic-sized Au and Pt contacts formed under cryogenic vacuum (4.2 K). Whereas I-V curves for Au are almost Ohmic, the conductance G=I/V for Pt decreases with increasing voltage, resulting in distinct nonlinear I-V behavior. The experimental results are compared with first principles density functional theory calculations for Au and Pt, and good agreement is found. The difference in conductance properties for Pt vs Au can be explained by the underlying electron valence structure: Pt has an open d shell while Au has not.
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Affiliation(s)
- S K Nielsen
- Interdisciplinary Nanoscience Center (iNano), CAMP and Department of Physics and Astronomy, University of Aarhus, DK-8000 Aarhus, Denmark
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Lin R, Galili M, Quaade UJ, Brandbyge M, Bjørnholm T, Esposti AD, Biscarini F, Stokbro K. Spontaneous dissociation of a conjugated molecule on the Si(100) surface. J Chem Phys 2002. [DOI: 10.1063/1.1480857] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Stokbro K, Quaade UJ, Lin R, Thirstrup C, Grey F. Electronic mechanism of STM-induced diffusion of hydrogen on Si(100). Faraday Discuss 2001:231-40; discussion 257-75. [PMID: 11271994 DOI: 10.1039/b003179h] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We have observed a scanning tunneling microscopy (STM) induced lateral transfer of a single hydrogen atom on the Si(100) surface. The transfer rate of the hydrogen atom is proportional to the electron dose, indicating an electron-assisted transfer mechanism. Measurements of the relations between the transfer rate and the sample bias and temperature give further support for an electronic mechanism. The bias dependence of the transfer rate shows a peak, and from a first principles electronic structure calculation we show that the position of the peak is related to the energy of a localized surface resonance. We propose that the hydrogen transfer is related to inelastic hole scattering with this surface resonance. We develop a microscopic model for the hydrogen transfer, and using the experimental data we extract information on the resonance lifetime and the transfer yield per resonant electron. The transfer takes place by tunneling through a small excited state transfer barrier. The transfer rate is increased if the hydrogen atom before the resonant excitation is vibrationally excited, and this gives rise to an increasing transfer rate with increasing sample temperature.
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Affiliation(s)
- K Stokbro
- Mikroelektronik Centret (MIC), Technical University of Denmark, Bldg. 345E, DK-2800 Lyngby, Denmark
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Laegsgaard J, Stokbro K. Hole trapping at Al impurities in silica: a challenge for density functional theories. Phys Rev Lett 2001; 86:2834-2837. [PMID: 11290051 DOI: 10.1103/physrevlett.86.2834] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/01/2000] [Indexed: 05/23/2023]
Abstract
The atomic geometry and electronic structure around a neutral substitutional Al impurity in silica is investigated using either the unrestricted Hartree-Fock (UHF) approximation, or Beckes three-parameter hybrid functional (B3LYP). It is found that the B3LYP functional fails to describe the structural distortions around the Al impurity, while the UHF results are consistent with experimental information. We argue that the failure of the B3LYP functional is caused by the incomplete self-interaction cancellation usually present in density functional theories.
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Affiliation(s)
- J Laegsgaard
- Research Center COM, Technical University of Denmark, Building 349, DK-2800 Kgs. Lyngby, Denmark
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Stokbro K, Chetty N, Jacobsen KW, Norskov JK. Effective-medium tight-binding model for silicon. Phys Rev B Condens Matter 1994; 50:10727-10741. [PMID: 9975173 DOI: 10.1103/physrevb.50.10727] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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