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Objective: Clinicopathological characteristics of neuroendocrine neoplasms are highly heterogeneous based on variable origins.Our study aims to explore the clinical features of rectal neuroendocrine neoplasm (RNEN). Methods: Patients with histologically diagnosed rectal neuroendocrine neoplasms were retrospectively analyzed between January 2012 and December 2020. Epidemiological characteristics, clinical manifestations, complete blood count, endoscopy findings, and pathological features were recorded and analyzed. T-test was used for measurement data analysis, Chi-square test was performed for classification data analysis, and Binary logistic regression was applied for analyzing risk factors of metastasis. Results: Among 172 patients, the male to female ratio was 107 to 65 with an average age of (52±12) years (16-77 years). Altered bowel habit was the most common initial symptom (58/172, 33.7%), followed by abdominal pain (36/172, 20.9%) and loss of body weight (27/172, 15.7%). One hundred and sixty-one cases were neuroendocrine tumors, 9 were neuroendocrine carcinomas and 2 were mixed neuroendocrine-non-neuroendocrine neoplasms. Most endoscopic presentations were polypoid lesions (147/172, 85.5%), mainly limited to mucosa (48/172, 27.9%) and submucosa (96/172, 55.8%). Twenty-nine patients developed lymph node invasion or distant metastasis at diagnosis. There were statistical difference of neutrophil-to-lymphocyte ratios (NLR) among groups with different tumor size (<10 mm vs. 10-20 mm vs.>20 mm, mean NLR 1.79±0.55 vs. 2.27±1.23 vs. 2.95±0.66, P<0.01. Compared with non-metastatic group, the metastatic group presented higher NLR(2.61±0.81 vs. 1.89±0.80, P<0.01). Tumor size (<10 mm vs. 10-20 mm vs.>20 mm, OR 1.00 vs. 2.10 vs. 5.25×109, P =0.001), invasion to bowel wall (mucosa vs. submucosa vs. muscularis vs. serosa invasion,OR 1.00 vs. 3.26 vs. 14.11 vs. 39.42, P=0.008), and NLR (NLR<2.25 vs. NLR≥2.25, OR 1.00 vs. 5.19, P =0.024) were risk factors for metastasis. Conclusion: Metastasis of RNEN is related with tumor size, degree of bowel invasion and NLR. High NLR is a poor prognostic factor of RNEN.
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Tumores Neuroendocrinos , Neoplasias del Recto , Neoplasias Gástricas , Adulto , Femenino , Humanos , Masculino , Persona de Mediana Edad , Tumores Neuroendocrinos/epidemiología , Neutrófilos , Pronóstico , Estudios RetrospectivosRESUMEN
OBJECTIVE: To evaluate the surgical technique and clinical effect of less invasive intrame-dullary nail fixation combined with titanium cable cerclage in the treatment of subtrochanteric fractures. METHODS: A retrospective study was performed in 46 cases of subtrochanteric fractures in Peking University People's Hospital from January 2015 to December 2017. Among them, there were 14 males and 32 females, with an average age of (77.83±10.66) years (44-92 years); 17 cases on the left side and 29 cases on the right side. The causes of injury included crash from a height, traffic accident and accidental fall. According to Seinsheimer classification, there were 26 cases of type â ¡, 11 cases of type â ¢, 9 cases of type â £, and these cases were all closed injury. After admission, these patients underwent continuous tibial tuberosity bone traction to maintain the length and force line of the lower extremity, so as to reduce the difficulty of intraoperative fracture reduction. Anticoagulant therapy was given before operation to reduce perioperative thrombotic complications. All the patients were treated with less invasive intramedullary nail fixation combined with titanium cable cerclage. Operation time, blood loss during surgery, time of fracture healing were recorded, Harris and Sanders scoring system were used to assess hip function after operation at each follow-up time point. RESULTS: All the included patients underwent surgery successfully. Average operative time and intraoperative blood loss of these patients were (131.09 ± 20.06) min and (191.96±111.03) mL, respectively. All the patients were followed up satisfactorily, with an average follow-up time of 28 months. The fractures received bone healing within 3-6 months, average hospital stay was (10.61±2.85) days. The Sanders score was excellent in 3 cases, good in 37 cases and common in 6 cases, with an excellent and good rate of 86.96%. The Harris score was excellent in 6 cases, good in 36 cases, with an excellent and good rate of 91.30%. There were no cases of wound infection, loss of reduction, nonunion of fracture or internal fixation failure. Hip pain symptoms were effectively relieved in most patients. CONCLUSION: Less invasive intramedullary nail fixation combined with titanium cable cerclage can obtain good alignment and stability of fracture ends, which is an effective method for the treatment of subtrochanteric fractures.
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Fijación Intramedular de Fracturas , Fracturas de Cadera , Anciano , Anciano de 80 o más Años , Clavos Ortopédicos , Femenino , Curación de Fractura , Fracturas de Cadera/cirugía , Humanos , Masculino , Estudios Retrospectivos , Titanio , Resultado del TratamientoRESUMEN
OBJECTIVE: To investigate the clinical effect of a modified arthroscopic outside-in suture technique in the treatment of meniscus tear using a spinal needle. METHODS: From January 2015 to October 2017, 95 patients treated with this method were followed-up. Among these cases, there were 36 males and 59 females. The age of the patients ranged from 16 to 77 years, (46.79±18.07) years in average. Among them, there were 28 patieats aged 16-35, 53 patients aged 36-65, and 14 patients aged over 65 years old. 28 cases were diagnosed with medial meniscus tear, 43 cases with lateral meniscus tear and 24 cases with both medial and lateral meniscus tear. Causes of the injury included sports, sprain, etc. According to Barrett standard, the clinical healing of meniscus tear was judged. Lysholm score, knee range of motion, visual simulation score (VAS) and magnetic resonance imaging (MRI) were used to evaluate the postoperative knee function and recovery of the patients. RESULTS: The 95 patients were followed up for 22 to 36 months, with an average of (28.32±3.98) months. According to Barrett standard, 90 patients (94.7%) obtained meniscus clinical healing. Meniscal healing rates were 96.43%, 96.23% and 85.71% in the three age groups, respectively. The meniscal healing rate was lower in the elderly group, but there was no significant difference in statistical results (P=0.262). Five patients had deep tenderness in the joint space of the injured side, and the overstretch test was positive. The preoperative and postoperative VAS scores, Lysholm scores and knee motion were compared in each group, and the differences were statistically significant (P < 0.01). At the end of the last follow-up, there were no cases of knee joint effusion, swelling and interlocking, and the joint function was effectively improved in most patients. No surgical site infection, periarticular vascular/nerve injury or knotting reaction was found during the follow-up. CONCLUSION: This modified arthroscopic outside-in suture technique using a spinal needle has the characteristics of simple operation, small trauma and rapid recovery, and the mid-term follow-up results were satisfactory. Therefore, we consider this method to be a safe and efficient method for the treatment of meniscus anterior horn and body tear.
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Traumatismos de la Rodilla , Lesiones de Menisco Tibial , Anciano , Artroscopía , Femenino , Estudios de Seguimiento , Humanos , Traumatismos de la Rodilla/cirugía , Masculino , Punciones , Técnicas de Sutura , Lesiones de Menisco Tibial/cirugíaAsunto(s)
Tumores Neuroendocrinos , Neoplasias Pancreáticas , Humanos , Tumores Neuroendocrinos/diagnóstico , Tumores Neuroendocrinos/terapia , Neoplasias Pancreáticas/diagnóstico , Neoplasias Pancreáticas/epidemiología , Neoplasias Pancreáticas/terapia , Neoplasias Intestinales , Neoplasias GástricasRESUMEN
OBJECTIVE: To investigate and analyze the complications of penile augmentation with acellular dermal matrix (ADM) and following management. METHODS: This was a retrospective review of all patients who received penile augmentation with ADM between June 2016 and January 2019. The patients were evaluated with outpatient physical examination. Related complications and following management were summarized and analyzed. RESULTS: Between June 2016 and January 2019, ADM was used as filling material on 78 patients (mean age: 31.14 years, range: 21-66 years), who were successfully received penile augmentation surgery. In the follow-up three months, the penile circumference was increased by 1.1 cm (0.5-2.1 cm) on average. The mean follow-up time was 12.20 months. In this study, there were 47 (60.26%, 47/78) patients with erectile discomfort, 91.49% (43/47) of whom manifested as erectile traction. There were 12 (15.38%, 12/78) patients with delayed healing, improved by daily regular dressing change. There were 10 (12.82%, 10/78) patients with unobvious augmentation effect. There were 9 (11.54%, 9/78) patients with stamp-like changes of ADM. There were 8 (10.26%, 8/78) patients with wound hematoma and 7 (8.97%, 7/78) patients with foreskin edema, relieved by compression with wrap. There were 4 (5.13%, 4/78) patients with wound infection and 3 (3.85%, 3/78) patients with skin necrosis of the dorsal side, which could be treated with ADM removal and repair surgery with bipedicle scrotal flap. And there were 2 (2.56%, 2/78) patients suffering psychological influence. Finally, most patients with various complications recovered successfully, however 7 patients (8.97%, 7/78) underwent ADM removal surgery. CONCLUSION: Using ADM as filling material could achieve positive effect in penile augmentation but the complications are common and cannot be neglected. Standardized surgical methods, rigorous postoperative care, and adequate notification with patients can effectively reduce the complications of penile augmentation with ADM. To treat properly and timely for complications can obtain satisfactory results.
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Dermis Acelular , Adulto , Anciano , Humanos , Masculino , Persona de Mediana Edad , Erección Peniana , Pene , Estudios Retrospectivos , Colgajos Quirúrgicos , Adulto JovenRESUMEN
OBJECTIVES: To assess the validity of using the calibration ruler for correcting magnification of linear measurements and to explore and compare the vertical and horizontal magnification of four digital cephalometric units. METHODS: An acrylic box was imaged at seven sagittal positions using four digital cephalometric units: Orthopantomograph OC100, Orthopantomograph OC200, Sirona Orthophos CD, and Sirona Orthophos DS. The true linear lengths of the phantom, corrected, and uncorrected linear lengths on the images were measured and compared. The validity of measurements using the calibration ruler was assessed. The magnification values and distortion indices were calculated and compared among the four cephalometric units. RESULTS: For linear measurements on the mid-sagittal plane and averaged linear measurements on bilateral symmetric sagittal planes, the bias 1.96 STD of the calibration ruler ranged from 1% to 2% for the four cephalometric testing units. For linear measurements on the single lateral sagittal plane, the bias 1.96 STD ranged from 3% to 6%. The vertical scanning charge-coupled device cephalometric unit produced the greatest distortion, ranging from 1.029 to 0.964. CONCLUSION: The metal millimeter calibration ruler is an accurate reference for linear measurement magnification correction. Because of unpredictability and machine specificity, the magnification and distortion of a cephalometric unit should be calibrated for the estimation of cephalometric measurement error.
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Calibración/normas , Cefalometría/métodos , Radiografía Dental Digital/instrumentación , Algoritmos , Cefalometría/normas , Humanos , Ortodoncia/instrumentación , Fantasmas de Imagen , Magnificación Radiográfica , Radiografía Dental Digital/métodos , Radiografía Panorámica , Pantallas Intensificadoras de Rayos XRESUMEN
OBJECTIVE: To explore a cone beam computed tomography (CBCT)-independent method for mandibular digital dental cast superimposition to evaluate three-dimensional (3D) mandibular tooth movement after orthodontic treatment in adults, and to evaluate the accuracy of this method. METHODS: Fifteen post-extraction orthodontic treatment adults from the Department of Orthodontics, Peking University School and Hospital of Stomatology were included. All the patients had four first premolars extracted, and were treated with straight wire appliance. The pre- and post-treatment plaster dental casts and craniofacial CBCT scans were obtained. The plaster dental casts were transferred to digital dental casts by 3D laser scanning, and lateral cephalograms were created from the craniofacial CBCT scans by orthogonal projection. The lateral cephalogram-based mandibular digital dental cast superimposition was achieved by sequential maxillary dental cast superimposition registered on the palatal stable region, occlusal transfer, and adjustment of mandibular rotation and translation obtained from lateral cephalogram superimposition. The accuracy of the lateral cephalogram-based mandibular digital dental cast superimposition method was evaluated with the CBCT-based mandibular digital dental cast superimposition method as the standard reference. After mandibular digital dental cast superimposition using both methods, 3D coordinate system was established, and 3D displacements of the lower bilateral first molars, canines and central incisors were measured. Differences between the two superimposition methods in tooth displacement measurements were assessed using the paired t-test with the level of statistical significance set at P<0.05. RESULTS: No significant differences were found between the lateral cephalogram-based and CBCT-based mandibular digital dental cast superimposition methods in 3D displacements of the lower first molars, and sagittal and vertical displacements of the canines and central incisors; transverse displacements of the canines and central incisors differed by (0.3±0.5) mm with statistical significance. CONCLUSION: The lateral cephalogram-based mandibular digital dental cast superimposition method has the similar accuracy as the CBCT-based mandibular digital dental cast superimposition method in 3D evaluation of mandibular orthodontic tooth displacement, except for minor differences for the transverse displacements of anterior teeth. This method is applicable to adult patients with conventional orthodontic treatment records, especially the previous precious orthodontic data in the absence of CBCT scans.
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Imagenología Tridimensional , Mandíbula/diagnóstico por imagen , Modelos Dentales , Técnicas de Movimiento Dental , Adulto , Diente Premolar , Cefalometría , Tomografía Computarizada de Haz Cónico , Técnica de Colado Dental , Humanos , Maloclusión , Maxilar , Diente Molar , Hueso PaladarRESUMEN
Objective: To study the correlation between the level of serum Chitinase-3-like protein 1 (CHI3L1) and the significant liver fibrosis and liver cirrhosis in patients with chronic liver disease, and to evaluate its diagnostic value. Methods: 165 patients with chronic liver disease were selected, liver histopathological examination was performed to detect serum CHI3L1 concentration. Four indexes of hepatic fibrosis (type III procollagen, collagen IV, laminin, hyaluronic acid), aspartate aminotransferase/platelet ratio index (APRI) and FIB-4 (fibrosis- 4) scores were based on the pathological findings of liver biopsy and compared the advantages and disadvantages of serum CHI3L1 with other methods for the diagnosis of hepatic fibrosis and liver cirrhosis. A multivariate regression analysis model was created, and receiver operating characteristic curve was analyzed. Results: The level of serum CHI3L1 increased with increase of fibrosis stage and was highest in liver cirrhosis stage. In the period of S0 to 1, the levels of S2 to 3 and S4 were 62.82 (41.40 ~ 87.20), 70.94 (48.47 to 122.60) and 141.06 (78.18 ~ 197.40), and there were statistically significant differences between the groups (P < 0.001). The area under the curve for the diagnosis of significant liver fibrosis was 0.68 (0.60 to 0.77), and 0.74 (0.65 to 0.83) for cirrhosis in CHI3L1. Multivariate regression analysis showed that CHI3L1 was an independent predictor of significant fibrosis and cirrhosis. The combined diagnostic model based on CHI3L1, collagen IV and FIB-4 scores further improved the diagnostic value. The area under the curve for the diagnosis of significant fibrosis and cirrhosis was 0.79 (0.72 to 0.86) and 0.80 (0.73 to 0.87), respectively. Conclusion: CHI3L1 has a good diagnostic value in patients with chronic liver disease with significant fibrosis and liver cirrhosis. The diagnostic model in combination with other markers like Collagen IV and FIB-4 scores could further improve the diagnostic value and is worthy of further study.
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Cirrosis Hepática , Aspartato Aminotransferasas , Biomarcadores , Biopsia , Plaquetas , Proteína 1 Similar a Quitinasa-3 , Enfermedad Crónica , Colágeno Tipo III , Colágeno Tipo IV , Humanos , Ácido Hialurónico , Laminina , Recuento de Plaquetas , Curva ROC , Suero , Índice de Severidad de la EnfermedadRESUMEN
This case report presents the treatment and long-term follow-up of a patient with severe skeletal hyperdivergent open bite, Class II malocclusion, and a severely retruded chin. After failure of early treatment using high-pull headgear with a bite block during the early permanent dentition stage due to an unfavorable growth pattern, orthognathic surgery was proposed but rejected by the patient. Then, temporary anchorage devices were used to correct the occlusion and establish an acceptable overbite and overjet. The overall observation time was 8.5 years; the treatment time using fixed appliances was 3 years and 4 months. The achieved tooth position and occlusal relationship remained stable 2.5 years later without recurrence of the open bite.
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Maloclusión Clase II de Angle/terapia , Mordida Abierta/terapia , Métodos de Anclaje en Ortodoncia/métodos , Aparatos Ortodóncicos , Procedimientos Quirúrgicos Ortognáticos/métodos , Cefalometría , Femenino , Estudios de Seguimiento , Humanos , Métodos de Anclaje en Ortodoncia/instrumentación , Resultado del TratamientoRESUMEN
OBJECTIVES: To evaluate the positional stability of miniscrews during orthodontic treatment change in cone-beam computed tomography (CBCT). SETTING AND SAMPLE POPULATION: Twenty adult volunteers were enrolled. METHODS: In all participants, at least two maxillary first premolars were extracted because of protrusion. Each volunteer received six miniscrews in the maxilla, including two loaded miniscrews to retract anterior teeth and four unloaded miniscrews. CBCT scans were obtained at the beginning of space closure (T1) and approximately 11.8 months later (T2). Three-dimensional miniscrew models were constructed at T1 and T2, and the central axes were calculated using a principal component analysis (PCA) technique. Finally, we measured and compared the angle change of all the miniscrews from T1 to T2. RESULTS: The angle change values of the unloaded and loaded miniscrews were 1.64 ± 1.25° and 1.67 ± 1.15°, respectively. No significant differences in the angle change were observed. CONCLUSION: Cone-beam computed tomography images revealed both the unloaded and loaded miniscrews to be positionally stable during en-masse retraction in this study.
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Tornillos Óseos , Tomografía Computarizada de Haz Cónico/métodos , Métodos de Anclaje en Ortodoncia/instrumentación , Diseño de Aparato Ortodóncico , Cierre del Espacio Ortodóncico/instrumentación , Adulto , Diente Premolar/cirugía , Femenino , Estudios de Seguimiento , Humanos , Procesamiento de Imagen Asistido por Computador/métodos , Imagenología Tridimensional/métodos , Masculino , Maloclusión Clase I de Angle/terapia , Maloclusión Clase II de Angle/terapia , Maxilar/cirugía , Miniaturización , Análisis de Componente Principal , Estrés Mecánico , Extracción Dental/métodos , Adulto JovenRESUMEN
OBJECTIVES: To identify a stable and reproducible reference region to superimpose serial maxillary dental models in adult extraction cases. SETTING AND SAMPLE POPULATION: Fifteen adult volunteers were enrolled. METHODS: To reduce protrusion, bilateral maxillary first premolars were extracted in all volunteers. Each volunteer received six miniscrews, including two loaded miniscrews used to retract anterior teeth and four unloaded miniscrews. Impressions for maxillary models were taken at T1 (1 week after miniscrew placement) and T2 (17 months later). Dental models were created and then scanned using a laser scanner. Stability of the miniscrews was evaluated, and dental models were registered using stationary miniscrews. The palatal region, where deviation was within 0.5 mm in all subjects, was determined to be the stable region. Reproducibility of the new palatal region for 3D digital model superimposition was evaluated. RESULTS: Deviation of the medial 2/3 of the palatal region between the third rugae and the line in contact with the distal surface of the bilateral maxillary first molars was within 0.5 mm. Tooth movement of 15 subjects was measured to evaluate the validity of the new 3D superimposition method. Displacements were 8.18 ± 2.94 mm (central incisor) and 2.25 ± 0.73 mm (first molar) measured by miniscrew superimposition, while values of 7.81 ± 2.53 mm (central incisor) and 2.29 ± 1.03 mm (first molar) were measured using the 3D palatal vault regional superimposition method; no significant difference was observed. CONCLUSION: The medial 2/3 of the third rugae and the regional palatal vault dorsal to it is a stable region to register 3D digital models for evaluation of orthodontic tooth movement in adult patients.
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Tornillos Óseos , Cefalometría/métodos , Marcadores Fiduciales , Maloclusión/terapia , Maxilar/patología , Métodos de Anclaje en Ortodoncia/instrumentación , Adulto , Diente Premolar/cirugía , Cefalometría/instrumentación , Femenino , Humanos , Procesamiento de Imagen Asistido por Computador/métodos , Imagenología Tridimensional , Incisivo/patología , Rayos Láser , Masculino , Modelos Dentales , Diente Molar/patología , Hueso Paladar/patología , Reproducibilidad de los Resultados , Extracción Seriada , Técnicas de Movimiento Dental/instrumentación , Adulto JovenRESUMEN
The determination of trace mercury in water samples by electrolytic deposition and electrothermal atomic-absorption spectrophotometry is described. Traces of mercury in water are preconcentrated by electrolytic reduction and deposition on a platinum wire cathode, which is then put into a graphite cup for direct atomization and measurement. The method is sensitive and simple, with a detection limit of 0.04 ng/ml. Almost all the metal ions commonly found in water samples can be tolerated, because of the selective deposition at controlled potential.
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KIE: This is the first of a set of three articles concerned with "bioethics on the Pacific Rim." The author, vice president of Beijing Medical University and vice chairman of the Beijing Academic Association for Morality, identifies population control, euthanasia, and the allocation of health care resources as bioethical issues of current interest in his country. Population policy in China is grounded in public welfare arguments. The idea of a right to choose one's death is found in Chinese philosophy, although Chinese legal experts believe that euthanasia is not compatible with present criminal, civil, or family law. Allocation of health resources remains a problem in China, even throughout the free medical service that serves a small portion, largely composed of government employees, of the country's population of 1.08 billion.^ieng
PIP: The systematic study of modern medical ethics and bioethics in China began in the early 80s, although medical moral theory dates back to 475 B.C. In October l988 the 1st Chinese bioethics association was founded. The most popular topics for their symposia include: population control, euthanasia, and the allocation of health care resources. Birth control and population policy in China are both attempting to slow the 15 million annual increase in population. Family planning services are available for all married couples that seek it including sterilization and abortion. The current policy is that families should have only 1 child; ethnic minorities and rural residents are exempt. All policies on population control, abortion, and contraceptives are grounded in public welfare arguments. What they oppose is a long tradition in Chinese culture of large families. Euthanasia in China is an old topic with traditional wisdom stating that each person should have the right to chose their means of death. However for medical personnel it provides 2 dilemmas. 1st, the deontological position that doctors have a duty to both saving a patient's life and relieving pain. The doctor can not forsake one for the other. 2nd, the patient's personal benefits may conflict with the family's or society's overall benefits. Legal experts in China feel that euthanasia is incompatible with Chinese marriage law which prohibits the mistreatment or abandonment of family members. Allocation of medical resources is another issue because 800 million Chinese are not covered under the state's free medical care. Of those who are, there is limited capacity and the issue of who gets care is currently being debated.^ieng
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Discusiones Bioéticas , Bioética , Política de Salud , China , Eutanasia , Eutanasia Activa , Servicios de Planificación Familiar , Asignación de Recursos para la Atención de Salud , Humanos , Selección de Paciente , Regulación de la Población , Asignación de Recursos , Derecho a MorirRESUMEN
INTRODUCTION: Our knowledge of facial muscles is based primarily on atlases and cadaveric studies. This study describes a non-invasive in vivo method (3D MRI) for segmenting and reconstructing facial muscles in a three-dimensional fashion. METHODS: Three-dimensional (3D), T1-weighted, 3 Tesla, isotropic MRI was applied to a subject. One observer performed semi-automatic segmentation using the Editor module from the 3D Slicer software (Harvard Medical School, Boston, MA, USA), version 3.2. RESULTS: We were able to successfully outline and three-dimensionally reconstruct the following facial muscles: pars labialis orbicularis oris, m. levatro labii superioris alaeque nasi, m. levator labii superioris, m. zygomaticus major and minor, m. depressor anguli oris, m. depressor labii inferioris, m. mentalis, m. buccinator, and m. orbicularis oculi. CONCLUSIONS: 3D reconstruction of the lip muscles should be taken into consideration in order to improve the accuracy and individualization of existing 3D facial soft tissue models. More studies are needed to further develop efficient methods for segmentation in this field.
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Músculos Faciales/anatomía & histología , Imagenología Tridimensional/métodos , Labio/anatomía & histología , Imagen por Resonancia Magnética/métodos , Cadáver , Humanos , Reproducibilidad de los ResultadosRESUMEN
The authors made a thorough and careful study on the Begg Stage I appliance and established a model of mechanics in accordance with the actual situation of arch wire being activated and derived a mathematical formula based on the elastic small deflection theory. This study provides not only the basis of choosing intrusive-force value for individual arches, but also the possibility of analysing dynamically the changes of intrusive- force value in the process of bite opening.
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Oclusión Dental , Aparatos Ortodóncicos , Ortodoncia Correctiva/métodos , Fenómenos Biomecánicos , Fuerza de la Mordida , Humanos , Matemática , Alambres para OrtodonciaRESUMEN
In the Begg Technique, factors controlling the anterior intrusive force provided by the archwire have yet to be fully clarified. The rationale for bite opening with very light forces, the effect of Class II elastics on intrusive force magnitude and the intrinsic quality of 'Australian' wire in bite opening are examined in this paper. A formula is presented which allows the intrusive force that archwires exert in different individuals to be predicted. The values derived from the formula were compared with case model measurements. It was found that the intrusive force of the archwire was affected by the length of the individual dental arch. The magnitude of this intrusive force was seen to increase gradually during the period of bite opening and appeared to be related to the use of Class II elastics. The study revealed factors which affected the magnitude of the intrusive force.
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Maloclusión/terapia , Aparatos Ortodóncicos , Alambres para Ortodoncia , Técnicas de Movimiento Dental/métodos , Arco Dental/patología , Elasticidad , Humanos , Maloclusión/patología , Modelos Teóricos , Soportes Ortodóncicos , Acero/química , Estrés Mecánico , Propiedades de Superficie , Técnicas de Movimiento Dental/instrumentaciónRESUMEN
Class II elastics are usually employed in the treatment of excessive overbite and overjet with the Begg technique. The effect of Class II elastics on bite opening and the extent of such an effect is uncertain. This article, based on measurements of 30 cases, illustrates that the effect of the vertical component of force from Class II elastics in reducing the intrusive force generated by the anchor bands in the upper archwire is less than previously believed. The position of the circles in the archwire for intermaxillary elastics has the greatest influence on the anterior intrusive force of the upper archwire. The direction of the Class II elastics and the length of the dental arch (a negative correlation) came second, while the force actually exerted by the elastics had the smallest influence. It is, therefore, suggested that the position of the intermaxillary elastic circles should be located according to the differing clinical objectives.