比较MRI检查中不同口腔金属材料伪影的实验研究

目的 通过实验,在MRI不同序列中,比较并分析不同口腔金属材料模型所产生的伪影面积,以便为选择适宜MRI检查的金属修复材料和MRI检查序列提供参考依据.方法 选择6种常用口腔金属材料分别制成标准模型,并以丙烯酸树脂模型作为对照物.MRI检查设备场强为1.5T,每一模型均采用7种不同序列(GRE T1WI、GRE T2WI、SE T1WI、FSE T1WI、FSE T2WI、FLAIR T1WI和FLAIR T2WI)进行检查,分别测量各序列图像中每一模型所产生的伪影面积并进行分析比较,统计学处理采用协方差分析.结果 显示同一序列中不同种类的金属模型对伪影大小产生的影响各异,其间差异有统计学意义(F=15.776,P＜0.000),其中,金钯合金、银钯合金与对照物间无差异;而相同金属模型在不同序列中所产生的伪影大小亦各不相同,差异有统计学意义(F=10.960,P＜0.000),其中,GRE T2WI序列产生的伪影面积最大.结论 贵金属修复材料能减少MRI检查时金属伪影的产生;对于特定金属修复材料,MRI检查时应选择产生伪影小的序列,可减少对图像质量的影响.     

Evaluation of minipigs as an animal model for alveolar distraction

OBJECTIVE: Alveolar distraction osteogenesis is a relatively novel tissue regeneration technique that remains, in some respects, at an experimental stage. The selection of an experimental animal biomodel is not clearly defined, with reports in the reviewed literature on dogs, sheep, and monkeys. The present objective was to compare 2 experimental biomodels (dog and minipig) using an alveolar distraction protocol with a novel prototype distractor. STUDY DESIGN: Three beagle dogs and 3 G?ttingen minipigs were evaluated, placing the distractor at the right hemimandible alveolar ridge after previous extraction of premolars. The radiological examination was carried out immediately after the distraction and at 2 weeks of consolidation. RESULTS: Satisfactory clinical and radiological results were obtained in 2 of 3 beagle dogs after the previous unilateral extraction of mandibular and maxillary premolars. During the consolidation, a height gain of approximately 5 mm was observed, with the appearance of radiodense bone trabeculae in the distraction chamber. The distraction failed in all of the minipigs. CONCLUSION: The minipig was not an appropriate biomodel for the study of alveolar distraction because the investigators were not able to maintain the seal of the distraction chamber or the stability of the distractor.     

Dental attrition and associated factors in adolescents 14 to 19 years of age: a pilot study

PURPOSE: This cross-sectional study evaluated the relationship between attrition and diverse variables in 390 Mexican adolescents aged 14 to 19 years. MATERIALS AND METHODS: An ordinal scoring system was used to describe the severity of attrition. RESULTS: Attrition prevalence was 33.3% and was associated with older age, presence of defective restorations, Class II malocclusion, and perception of stress level. CONCLUSION: Our results suggest that attrition is present in 1 of every 3 adolescents.     

Oral lichen planus: a clinical and morphometric study of oral lesions in relation to clinical presentation

Oral lichen planus (OLP) is a chronic inflammatory disease with different clinical presentations that can be classified as reticular or atrophic-erosive. Sixty-two OLP patients were studied to evaluate the clinical-pathologic characteristics of their OLP lesions and to investigate possible differences in their biological behavior. The most common clinical presentation was the reticular type (62.9% vs 37.1%). Atrophic-erosive presentations showed significantly longer evolution (chi square=4.454; p=0.049), more extensive lesions (chi square=16.211; p=0.000) and more sites affected than reticular ones (chi square=10.048; p=0.002). Atrophic-erosive OLP was more frequently found on the tongue, gingiva and floor of the mouth. No statistically significant differences could be identified between reticular and atrophic-erosive clinical presentations in terms of age, sex, tobacco habit, plasma cortisol level and depth of inflammatory infiltrate. We concluded that the classification of OLP lesions as reticular vs atrophic-erosive is a simple, easy to use classification that can identify clinical presentations with different biological behavior.     

Protein free diet feeding: effects on sympathetic activity and salivary evoked secretion in the submandibular gland of the rat

Protein restriction impairs the salivary flow rate and composition in human and rats. The aim of the present work was to establish the effect of low protein (casein 5%) and protein free (casein 0%) isocaloric diets on sympathetic activity and salivary evoked secretion in the submandibular gland (SMG) of the rat. After 21 days, rats fed casein 0% presented: (a) a significant shift to the left of the dose-response curves (DRC) to the autonomic agonists-norepinephrine (NE), methoxamine, isoproterenol (ISO) and methacholine; (b) increased food consumption (p<0.001); (c) decreased body (p<0.001) and SMG (p<0.001) weights maintaining SMG/body (w/w) relation; (d) enhanced submandibular alpha1-adrenoceptor number without changes in the apparent dissociation constant (Kd); (e) increased submandibular NE content (p<0.05) and phosphoinositoside hydrolysis (p<0.001); (f) decreased submandibular tyrosine hydroxylase activity (TH) (p<0.01). Casein 5% feeding increased food consumption (p<0.01) and reduced body weight (p<0.05). This protein restriction increased metacholine-evoked salivation, but it altered neither submandibular sympathetic activity nor sympathetic-induced salivary secretion as compared to the Control group (C) fed a similar diet containing 25.5% protein. Present results suggest that in the adult rat, a protein free diet during 21 days lowers SMG sympathetic and cholinergic activity leading to supersensitivity as revealed by up-regulation of alpha1-adrenergic receptor number and increased autonomic-evoked salivation.     

小型猪一侧失牙及义齿修复后TMJ关节液中IL-1β、TNF-α、TGF—β1含量的变化

目的：检测小型猪一侧失牙及义齿修复后颞下颌关节（temporomandibularjoint，TMJ）关节液中IL-1β、TNF-α、TGF-β1含量，探讨其在颞下颌关节紊乱病中的作用及相互关系。方法：11头小型猪随机分为空白组2头、拔牙组4头和修复组5头，拔牙组和修复组左侧后牙全部拔除，修复组于拔牙后3个月义齿修复；每月采集双侧TMJ关节液，ELISA法测定IL-1β、TNF-α、TGF-β1含量（共6个月）。结果：拔牙组和修复组关节液中IL-1p浓度于第1个月达到最大值，拔牙组于第3个月、修复组于第5个月IL-1β浓度达到最小值；拔牙组于第4个月、修复组于第3个月TNF-α达到最大值；拔牙组和修复组于第3个月TGF-β1浓度达到最大值。结论：IL-1β启动并与TNF—α协同破坏TMJ；TGF-β1在TMJ损伤的修复中发挥重要作用。     

Fixed rehabilitation of a patient with hypohidrotic ectodermal dysplasia using zygomatic implants

We found few references in the dental literature on implant rehabilitation of patients with hypohidrotic ectodermal dysplasia and only 1 case on zygomatic fixations and maxillary prosthesis in a patient with hypohidrotic ectodermal dysplasia. Two zygomatic fixations were placed according to the sinus slot technique, together with 3 implants in the anterior maxillary region. After 6 months, an upper complete prosthesis was screwed onto the implants, and lower overdentures were placed over the remnant canines. After 18 months of follow-up the patient reported important improvement in oral function and self-esteem.     

Analysis of cyclic voltammograms of electrochromic a-WO3 films from voltage-dependent equilibrium capacitance measurements

The main features of cyclic voltammograms (CVs) of thin electrochromic films based on a-WO₃ were investigated. First, the chemical capacitance is defined in terms of the electrochemical potential variation with the insertion level, x, and is measured under galvanostatic (chronopotentiometry) quasi-equilibrium conditions. An equilibrium capacitance increasing rapidly with respect to insertion level or negative potential is observed, respectively C_ch∝x^a at x>10^?3(a≈0.74) and C_ch∝V^α(α≈3). Simulation methods used to generate the observed CVs are described in detail. Major CV peaks can be simply understood as charging and discharging of the variable capacitor, in conjunction with a distortion of the voltage scale due to a series transport process. Therefore a simple RC equivalent circuit allows us to explain the principal CVs characteristics of lithium intercalation and deintercalation in amorphous films.     

Conversion from cyclosporin A to tacrolimus as a non-surgical alternative to reduce gingival enlargement: a preliminary case series

BACKGROUND: Gingival enlargement (GE) is a frequent side effect that occurs in organ transplant recipients (OTR) after the administration of cyclosporin A (CsA). The availability of new drugs used to suppress graft rejection in OTR offers an opportunity to manage GE non-surgically. This preliminary case series aimed to analyze the effect of CsA withdrawal and its substitution by another immunosuppressant in OTR with severe GE. METHODS: Four organ transplant recipients who had received a liver or renal allograft were recruited for this study. All OTR had developed clinically severe CsA-induced GE. GE scores were assessed for each patient at baseline and at weeks 2, 4, 8, 12, 16, and 54 following conversion to tacrolimus. Scaling and root planing were initially performed and repeated monthly during the first 6 months. Careful polishing of the teeth was carried out once every 2 weeks until month 6 and then monthly until month 12. Hygiene instructions and reinforcement to optimize oral hygiene were maintained throughout the study. RESULTS: The four patients showed a rapid decrease in their gingival symptoms and in the size of the gingivae. This change was clinically evident 8 weeks after conversion to tacrolimus. One year later, all the patients experienced GE regression, although some anatomic irregularities persisted in the interdental papillae of one of the patients. No adverse effects from tacrolimus were observed during the study except in one patient who presented headaches. CONCLUSION: It seems that CsA withdrawal and its conversion to tacrolimus in organ transplant recipients who develop severe gingival enlargement, together with an extensive plaque control program, provide an effective means to control/eliminate gingival hyperplasia, with minimal risk of graft dysfunction.     

Solitary fibrous tumor of the orbit

Painless unilateral proptosis is a frequent manifestation of numerous orbital neoplastic and non-neoplastic processes. Various mesenchymal tumors of both fibrohistiocytic and vascular origin are well-described causes. Solitary fibrous tumors (SFTs) are rare spindle-cell neoplasms usually found associated with serosal surfaces, especially the pleura, but they have recently been described in a number of extrapleural sites including the orbit. The authors describe the case of an 18-year-old man who presented with a 6-month history of painless proptosis in the right eye. A visible nontender mass in the right supermedial orbit producing ptosis of the upper lid was present. Magnetic resonance imaging (MRI) showed a well-circumscribed soft tissue mass located above the right globe with no obvious invasion of adjacent orbital structures. Uneventful surgical excision through a right frontal-orbitotomy approach was performed. Histological evaluation showed a solid, highly vascular tumor mass composed of spindle cells arranged in short ill-defined fascicles. Intense immunohistochemistry staining for CD34 and B-cell lymphoma 2 (BCL-2) differentiated the lesion from the more common hemangiopericytoma. Though considered benign, local recurrence and extraorbital extension of orbital SFTs have been described. Malignant behavior, including distant metastases, has been documented in as many as 20% of pleural cases with mortality rates as high as 50%. The natural history of this tumor in the orbit is unclear. The authors report the 35th case of orbital solitary fibrous tumor and discuss the differential diagnosis, histopathology, radiological features, and clinical course.