鄂托克前旗马场井村改水降氟15年病情防治效果分析

目的：了解改水降氟后地氟病的防治效果。方法：水氟，尿氟测定均为电极法，氟斑牙诊断为Dean‘s法。结果：该村自1985年改饮低氟水，水氟含量由改水前的6.05mg/L降至改水后的0.48mg/L。改水后未出现新的氟骨症患者，8-12岁儿童氟斑牙患病率呈逐年下降趋势，改水后7-15年间氟斑牙病率均已稳定，表明病情得到有效控制，且达到稳定控制状态，结论：坚持长年饮用低氟水，地方性氟中毒就能得到有效控制。     

固定桥桥体龈底形态对接触区黏膜微生态影响的研究

目的探讨烤瓷桥桥体龈端不同形态设计对牙槽嵴顶黏膜微生态的影响。方法对60例磨牙烤瓷修复的患者采用常规细菌培养和计算机鉴定的方法进行检测。结果桥体龈端接触区细菌附着量和种类与牙体预备前相比,均有增多。其中,改良鞍式和改良盖嵴式桥体龈端接触区细菌附着量和细菌种类变化的差异有统计学意义(P<0.05);而舟底式桥体龈端接触区细菌附着数量和种类的变化,均无统计学意义(P>0.05)。戴用3个月后,各组链球菌和奈瑟菌的组成比例变化与牙体预备前相比,差异有统计学意义(P<0.05);其余各类细菌组成比例的变化无统计学意义(P>0.05)。结论从对桥体底黏膜微生态的影响考虑,烤瓷桥舟底式桥体优于改良鞍式和改良盖嵴式桥体,是值得临床推广应用的磨牙桥体设计。     

FRACTURE OF ABUTMENT SCREW SUPPORTING A CEMENTED IMPLANT-RETAINED PROSTHESIS WITH EXTERNAL HEXAGON CONNECTION: A CASE REPORT WITH SEM EVALUATION

One of the causes of implant failures in cemented implant-retained prostheses is the fracture of abutment screw or UCLA abutment. This article reports a case of simultaneous fracture of two UCLA abutments screws occurring in an implant-supported prosthesis placed in the mandibular molar region. The fractured structures were examined under scanning electron microscopy to investigate the probable causes of the failure, which were not related to failures on materials or fabrication of the screws, but rather were due to shear forces. The misfit in cemented prostheses may be the most likely cause of shear force generation.     

安徽省学生近20年常见病患病情况分析

目的了解安徽省学生视力低下、龋齿、贫血的患病状况及变化趋势,为开展学生常见病防治工作提供参考。方法对1985,1995,2000,2005年4个不同时期安徽省学生体质健康调研资料7～22岁学生视力低下、龋齿、贫血等常见病的患病状况进行分析。结果20a间,学生贫血患病率明显下降,从1985年的55.5%下降到2005年的5.3%;龋患率1985年至2000年明显上升,从32.1%上升到42.6%,2000年以后呈下降趋势,达18.8%;近视率逐年上升并居高不下,从1985年的23.0%上升到2005年的55.2%,尤其是高中生和大学生,高达70%～80%。结论通过开展学生常见病防治工作,学生贫血患病率和龋患率明显下降,但学生近视率逐年上升并居高不下,应引起有关部门的重视。     

Dentition planning with image-based occlusion analysis

Purpose To develop an easy-to-use, dentition planning method which is based on three-dimensional (3D) computer planning technology to replace conventional plaster-cast occlusion planning techniques. Methods The optimal dental occlusion is defined according to the condition of centric occlusion, i.e. after bringing occlusal surfaces of mandibular and opposing maxillary arches into identical 3D position. This identical position of occlusal surfaces represents the common reference frame for the 3D manipulation of all graphical elements. The planning procedure involves the following steps: (1) the optimal occlusal surface is approximated as triangle and localized both on the maxilla and mandible; (2) the original volumetric model is resampled according to the occlusal orientations; (3) the program reads in the models of ideal upper and lower dental arches from files, reshapes those to the patient anatomy and visualizes the local alignment on separate panels for mesiodistal and faciolingual inclinations. The final goal of the proposed method is to combine the requirements of functional and aesthetic designs and create an input for orthodontics, implantology and maxillofacial surgery. Results In the present study the optimal dental occlusion is created by image resampling after bringing the occlusal surfaces of mandibular and opposing maxillary arches into identical 3D position. This identical position of occlusal surfaces represents the common reference frame for manipulation of all graphical elements. Conclusions The proposed graphical environment was able to fit the elements of the ideal dentition curve to patient computed tomography under predefined centric occlusion. Rotation and scaling transformations of teeth were possible in the reformatted volumetric views about any of the axes of the teeth’s own reference space.     

超声洁治和局部用甲硝唑治疗轻、中度种植体周围炎

目的：评价用碳纤维工作头的超声洁牙机和25％甲硝唑凝胶治疗种植体周围炎的疗效。方法：将27颗患轻中度种植体周围炎的种植牙随机分为洁牙机治疗组和甲硝唑治疗组，在基线、1、2、6和12周时检查种植体的临床和生物学指标。结果： 两种治疗方法均可使菌斑指数、龈沟出血指数、龋下微生物的酶活性检查等指标改善。治疗期间未发现任何不良反应。结论；碳纤维头超声洁治和局部用25％甲硝唑凝胶是治疗牙种植体周围炎的安全有效的方法。     

HZ818树脂在紫杉醇初分离工艺中的应用

采用HZ818大孔吸附树脂对红豆杉浸膏中的紫杉醇成分进行吸附和洗脱试验，同时利用液质联用进行分析检测，确定了其最佳工艺参数。结果表明，HZ818树脂对紫杉醇有良好的吸附分离效果。优化工艺条件为：样品溶于体积分数40％甲醇，以1．5mL／min过柱，体积分数75％甲醇淋洗，体积分数85％甲醇以0．5mL／min洗脱，紫杉醇的质量分数从原浸膏中的1．02％提高到8．1％，回收率达98．6％。     

多官能度活性橡胶增韧环氧树脂的研究：Ⅲ.三元共混增韧环氧树脂

本文研究了双酚A对多官能度环氧基和羧基聚丙烯酸正丁酯橡胶增韧环氧树脂的影响。结果表明,加入双酚A,拉伸断裂能有大幅度提高,同时不降低弹性模量。这可能是由椽胶提高断裂伸长与双酚A提高屈服应力产生协同效应的结果。对羧基橡胶增韧的三元共混体系,拉伸断裂能随羧基官能度上升而增加。断裂面的形态研究表明,由于羧基橡胶与双酚A的酯化反应,大大减少了羧基橡胶聚集对增韧的不利影响。     

Pixel value modification using RVG-4 automatic exposure compensation for instant high-contrast images

The RVG-4 permits automatic exposure compensation (AEC). The purpose of this investigation was to determine the effects of AEC on image contrast. Images were made either with or without a dental QA jaw phantom using a fixed image projection geometry. Exposures were 6.3 through 27.3 μC/kg using an X-ray generator operated at 70 kVp. Region of interest pixel value distributions were measured at tissue thicknesses in this phantom, and the average pixel values and signal-to-noise ratios (SNR) were calculated. The use of AEC without an object in place resulted in a disproportionate relationship between pixel value and exposure with a marked reduction in SNR. The use of AEC on under- and over-exposed images of the phantom simultaneously enhanced image contrast and reduced SNR. Thus, AEC provides a convenient and quick method for achieving high-contrast images with sub-optimal exposures, however, this could lead to inappropriate patient dosages if the function is used for over-exposed images. AEC reduces the SNR and produces disproportionate pixel values relative to exposure.     

橡胶活性官能团对增韧环氧树脂动态力学性能的影响

用动态扭摆法测试聚丙烯酸丁酯橡胶增韧环氧树脂的动态力学行为,研究在环氧树脂低固化度和高固化度时,橡胶活性官能团种类(环氧基官能团与羧基官能团)和数量(官能度)对其影响。研究体系中橡胶玻璃化转变温度(Tg)的移动大小,与橡胶和基体树脂健合程度之间的关系。