CO2激光配合根管充填治疗根端瘘管及根尖囊肿

慢性根尖周炎导致的经久不愈的牙龈根端瘘管及根尖囊肿,口腔科临床常见。单纯根管治疗需时长、困难大,如结合普通手术摘除,患者出血多、痛苦大、易复发。笔者自1990年4月以来,应用CO_2激光配合根管及牙周塞治治疗,取得疗程短、见效快的满意效果。     

口腔锥形束CT观察纳米羟基磷灰石诱导犬根尖闭合的研究

目的:口腔锥形束CT(cone beam CT,CBCT)评价纳米羟基磷灰石(hydroxyapatite,HA)诱导年轻恒牙根尖形成的效果.方法:选用2只56月龄犬的16颗恒切牙,术前拍摄CBCT片测量根尖面积,经去髓后,随机分为4组,A组为实验组,用HA糊剂充填根管;B、C组为阳性对照组,分别用氢氧化钙(calcium hydroxyde,CH)、Vitapex充填;D组为阴性对照组,用AH plus糊剂充填.术后4周通过CBCT片观察根尖形态并与数字化X线根尖片对比.利用CBCT系统软件测量根尖面积,每组数据与术前相比行配对t检验,各组根尖面积减少值行单因素方差分析(α=0.05).结果(1)CBCT显示:A、B、C组根尖矢状面呈内聚状,未完全闭合,D组根尖呈平行开放状.A、B、C、D组根尖横断面均呈颊舌径较大的椭圆形,未闭合.根尖片显示:A、B、C组根尖呈内聚闭合状,D组根尖呈平行开放状.(2)CBCT显示:A、B、C各组根尖面积测量数据术后与术前对比均有缩小(配对t检验P＜0.05),但3组间根尖面积缩小量差别不显著(方差分析(P＞0.05).D组术后与术前相比根尖无明显缩小(配对t检验P＞0.05)结论:(1)CBCT与根尖片相比,能更准确反映根尖形态,适于根尖诱导术后评价.(2)HA能诱导根尖闭合,影像学观察其短期效果与CH、Vitapex差别不显著.     

He-Ne激光辐照蚕豆根尖引起细胞染色体变异的研究

采用低功率He-Ne激光辐照蚕豆的根尖,控制辐照剂量.用光学显微摄影系统观察统计细胞有丝分裂活性和染色体变异.发现了受激光辐照样品根尖细胞有丝分裂活性增强,有染色体发生结构变异的现像.分析讨论了He-Ne激光辐照引起染色体变异情况及诱发基因突变的可能性.     

Nd:YAG激光和传统根尖外科手术治疗窦道型根尖周炎疗效的对比研究

目的:探讨Nd∶YAG激光和传统根尖外科手术治疗窦道型根尖周炎的疗效差异。方法:将54例窦道型根尖周炎的患牙随机分成Nd∶YAG激光治疗组和传统根尖外科手术治疗组,在Nd∶YAG激光治疗组中,将Nd∶YAG激光光纤头沿瘘管插入根尖,然后缓慢旋转后退照射瘘管避,重复照射3次,并配合生理盐水冲洗。传统根尖外科手术组采用手术治疗患牙。分别对两组患牙进行术后48h反应情况、术后10天情况和术后3个月情况进行复查。结果:术后48hNd∶YAG激光处理组的术后反应明显较常规手术组轻(P=0.000)。两组数据有显著差异性。术后10天Nd∶YAG激光处理组和常规手术组在术后10天的疗效相同(P=0.655)。术后3个月Nd∶YAG激光处理组和常规手术组的疗效相同(P=0.541)。结论:Nd∶YAG激光在治疗窦道型根尖周炎方面与传统根尖外科手术相比在治疗效果方面没有明显差异,且Nd∶YAG激光治疗后,患牙的术后不适反应更轻,因Nd∶YAG激光在治疗过程中的创伤更小,更加安全,所以其临床适用范围较传统根尖外科手术更广,值得推广。     

缺钙对白菜根尖细胞超微结构和ATP酶活性的影响

钙是植物生长发育必需元素之一,缺乏时引起严重的生理病害,首先是根生长的抑制和伤害。已证明白菜“干心病”是由于体内钙不足引起的。本文应用溶液培养技术研究白菜“干心病”与钙素营养的关系,结合电镜研究缺钙对根尖细胞超微结构的影响,应用磷酸铅沉淀法对ATP酶活性进行超微结构定位,比较正常钙水平和缺钙培养下的活性反应。选用杨柳青小核桃纹白菜,以修改的岩田正利营养液培养。设正常钙水平组(含钙160ppm)和缺钙组。处理三天和十天后取根尖2—4mm,放入2％多聚甲醛加1％戊二醛固定液中常规圆定、温育、包埋     

缺铁水稻根细胞膜泡相关基因群的分析与电镜观察

在缺铁固体培养基中,可清楚地观察到水稻根表面的分泌物和根的形态变化以及侧根增多.为了从分子水平深入了解水稻受缺铁胁迫后的反应机理,对缺铁水稻根进行了10531个EST芯片的微点阵分析,发现膜泡相关的基因群相对转录表达率最高.利用超薄切片技术,在透射电镜下观察了缺铁胁迫下水稻根尖细胞的结构变化.结果显示：缺铁根尖细胞中,膜泡好似起源于质膜和囊泡的组装,然后在质膜上凸起,并且是双方向性的.膜泡表面有衣被.虽然正常供铁情况下也有膜泡出现,但与缺铁比较有很大区别.缺铁根尖细胞的膜泡明显大,膜泡和凹陷泡上有较清晰的衣被.同时还观察到在单层膜的膜泡内有管状和圆球形的内含物质.内含物的来源有可能,至少是部分通过内吞作用来源于细胞外基质.     

欧李染色体制片技术初探

采用欧李实生苗的幼根为材料,对欧李根尖的常规制片关键技术进行探索研究。研究结果表明,欧李根尖细胞分裂最旺盛的时期为上午8：00-10：00,可以明显观察到有丝分裂的问期、前期和中期;采用0．1％的秋水仙素溶液与0．002mol／L的8-羟基喹啉水溶液的等量混合液预处理3-4h,可以得到较多的分裂中期相;1mol／L盐酸酸解最佳时间为10-15min。     

手工网印常用的定位方法有6种

手工网印常用的定位方法有6种： 1．边角定位：适合于印件尺寸一致性好的情况下使用； 2．孔定位：适合印件材料较厚的使用，如电路板； 3．三点定位：送料要轻巧，合适后最好真空吸附；     

一种没有荫罩的彩色显象管

在彩色显象管靠近荧光屏的地方,安装了一块象“筛子”一样的金属孔板叫荫罩板,在板上整整齐齐地排列着许多小圆孔,孔的大小和荧光点相当(这是色点管的情况,如果是色条管,则荫罩上的孔变成一条条缝隙。),而且每个小孔都对准荧光屏上的一组红、绿、蓝荧光点(色点)。这样,当三个电子枪的位置安装合适时,三根电子束便在小孔上交叉,并且在穿过小孔之后,恰好分别     

锥形束CT和全颌曲面断层片在根尖区牙根外吸收诊断中的对比研究

目的:比较锥形束CT(cone-beam computed tom CT)和全颌曲面断层片(全景片)在根尖区牙根外吸收(根尖吸收)诊断中的差异.方法:选取80颗单根前磨牙,用以模拟4种不同程度的根尖吸收:无(完整的牙根)、轻度(根尖区表面1.0mm直径和深度的洞形)、中度(1.0mm牙根缩短)、重度(3.0mm牙根缩短).模拟完成后,对所有牙齿拍摄CBCT和全景片获取两组X线图像.两名正畸医师通过对图像资料的分析独立地评估所有根尖吸收的严重程度.结果:采用CBCT和全景片评估轻度根尖吸收的正确率分别为100％和27.5％,差异有统计学意义(P＜ 0.001);评估全部根尖吸收的正确率分别为81.9％和64.4％,差异有统计学意义(P＜0.001).结论:相比于全景片,CBCT对根尖吸收具有更高的敏感度.在正畸临床中,CBCT可用于对根尖吸收进行早期诊断,从而为继续或修正当前的正畸治疗提供必要的参考意见.     

Automatic extraction of inferior alveolar nerve canal using feature-enhancing panoramic volume rendering

Dental implant surgery, which involves the surgical insertion of a dental implant into the jawbone as an artificial root, has become one of the most successful applications of computed tomography (CT) in dental implantology. For successful implant surgery, it is essential to identify vital anatomic structures such as the inferior alveolar nerve (IAN), which should be avoided during the surgical procedure. Due to the ambiguity of its structure, the IAN is very elusive to extract in dental CT images. As a result, the IAN canal is typically identified in most previous studies. This paper presents a novel method of automatically extracting the IAN canal. Mental and mandibular foramens, which are regarded as the ends of the IAN canal in the mandible, are detected automatically using 3-D panoramic volume rendering (VR) and texture analysis techniques. In the 3-D panoramic VR, novel color shading and compositing methods are proposed to emphasize the foramens and isolate them from other fine structures. Subsequently, the path of the IAN canal is computed using a line-tracking algorithm. Finally, the IAN canal is extracted by expanding the region of the path using a fast marching method with a new speed function exploiting the anatomical information about the canal radius. In experimental results using ten clinical datasets, the proposed method identified the IAN canal accurately, demonstrating that this approach assists dentists substantially during dental implant surgery.     

Numerical computation of impedances of a human tooth for estimation of the root canal length

Alternative current (ac) current conduction through a human tooth has been investigated through numerical simulation. Numerical calculation of impedance between the file (electrode) inserted in the root canal of the tooth and the outer electrode enables investigation of the impedance method used in dentistry for evaluation of the root canal length. Simulations confirm the improved sensitivity of the impedance method using the results of multiple frequency measurements.     

Studying the locator polynomials of minimum weight codewords of BCHcodes

Primitive binary cyclic codes of length n=2^m are considered. A BCH code with designed distance δ is denoted B(n,δ). A BCH code is always a narrow-sense BCH code. A codeword is identified with its locator polynomial, whose coefficients are the symmetric functions of the locators. The definition of the code by its zeros-set involves some properties for the power sums of the locators. Moreover, the symmetric functions and the power sums of the locators are related to Newton's identities. An algebraic point of view is presented in order to prove or disprove the existence of words of a given weight in a code. The principal result is the true minimum distance of some BCH codes of length 255 and 511. which were not known. The minimum weight codewords of the codes B(n2^h -1) are studied. It is proved that the set of the minimum weight codewords of the BCH code B(n,2^m-2-1) equals the set of the minimum weight codewords of the punctured Reed-Muller code of length n and order 2, for any m     

Analysis of calcitonin gene-related peptide (CGRP)-containing nerve fibres in the rat spinal cord using light and electron microscopy.

Calcitonin gene-related peptide (CGRP) content in areas surrounding the central canals of cervical, thoracic, lumbar and sacral spinal cords of rats were investigated by light microscopy, conventional transmission electron microscopy (CTEM) (100-200 kV) and high-voltage transmission electron microscopy (HVTEM) (1000 kV) using immunocytochemistry. Tissues were examined using either the peroxidase-antiperoxidase technique or an immuno-cryoultramicrotomy technique. Light microscopically, more intense CGRP localization was observed ventral to the central canals in the lumbar and sacral cord compared with the dorsal area in the same regions. HVTEM revealed that high levels of CGRP labelling were found adjacent to the basal side of ependymal cells ventral to the central canal. Analysis using CTEM operated at 200 kV demonstrated that the CGRP immunoreactivity was present within unmyelinated nerve fibres in the vicinity of the basal side of ependymal cells ventral to the central canal. Immuno-cryoultramicrotomy revealed that immuno-gold particles indicating CGRP labelling were localized on vesicle-like electron-dense bodies in unmyelinated and some fine caliber myelinated nerve fibres. Existence of CGRP as a primary afferent marker in the area surrounding the central canal suggest that there may be an intimate relationship between the modulation of nociceptive information and the area surrounding the central canal in rat spinal cord.     

域间路由系统级联失效下的目标失效链路定位方法研究

协同跨平面会话中断攻击(CXPST)通过反复对多条目标关键链路实施低速率拒绝服务攻击(LDoS)造成域间路由系统的级联失效,从而导致互联网的崩溃。在攻击发生的初期,准确定位受攻击的关键链路并进行针对性防御可遏制级联失效的发生。现有定位方法研究主要基于单源假设,没有考虑多条目标链路同时失效对路径撤回的影响,定位准确度受限。针对上述问题,该文提出一种基于加权统计匹配得分的多失效链路定位方法(WSFS),以级联失效攻击目标链路选择策略作为推断基础,将撤销路径长度的倒数作为权重对评分进行加权。基于实际网络拓扑和有利点位置的级联失效攻击仿真实验结果表明,WSFS比目前最优方法平均准确率可提升5.45%。实验结果证明WSFS相比于其他定位方法更适合应对域间路由系统级联失效下的目标失效链路定位问题。     

IC芯片的高速高精度视觉检测定位算法及实现

多引脚小间距IC器件是电子产品生产过程中视觉检测与定位的难点.针对高速高精度贴片机生产中IC芯片的图像识别对中问题,介绍了IC的视觉检测任务,提出一种自主研发的识别与定位算法及其实现技术.现场实际运行结果表明,该算法的速度和精度能满足实际生产的需要,并具有较强的鲁棒性.     

双机协同定位误差分析的研究

测向交叉定位技术是协同定位常用方法,针对双机协同测向交叉定位算法及其定位精度进行理论研究和仿真分析。首先给出了交叉定位造成的模糊区的计算方法,并进行仿真;而后重点对测向定位精度进行分析,给出定位算法和误差计算公式,并针对不同载机间距和间距误差、测角误差下的目标GDOP的分布进行了仿真分析。仿真结果表明,定位误差随着间距误差、测角误差的增大而增大,随着双机间距的增大先减小而后增大。     

激光在根管治疗中的研究和应用进展

激光在根管治疗中的研究和应用正不断深入。本文对激光根管预备、激光杀菌作用、激光根管充填、激光去除根管充填材料和折断器械的作用及激光对根尖周炎愈合的影响作一综述，最后介绍了减轻激光对牙根周围组织不利影响的方法。     

A comparison of measured and calculated intracavitary potentialsfor electrical stimuli in the exposed dog heart

The objective of this paper is to test the feasibility of using a multielectrode, intracavitary probe to solve a forward problem in which measured intracavitary potentials are compared to those calculated from subendocardial potentials and left ventricular (LV) cavity geometry. Intracavitary potentials and subendocardial potentials are measured simultaneously during electrical pacing stimuli from the LV apex, LV anterior base, LV posterior base, and right ventricular (RV) outflow tract of three exposed dog hearts. The LV cavity geometry is measured from postmortem magnetic resonance microscopy images of fixed hearts. Boundary integrals are approximated using a boundary element method and solved for intracavitary potentials. Correlation coefficients for LV apical pacing episodes are 0.989 +/- 0.002 while those for nonapical pacing episodes are 0.873 +/- 0.092. These results indicate that for electrical pacing from the apex, intracavitary stimulus potentials can be calculated with a high degree of accuracy. For nonapical pacing locations, the accuracy decreases since the calculations are more sensitive to errors in measuring probe position and LV cavity geometry near the septum. These results show that accurate geometric measurements of the intracavitary probe position and subendocardial surface are the primary concerns in solving future forward and inverse problems using an intracavitary probe.