全瓷冠熔附纯钛小基台种植修复体的临床应用

目的采用全瓷冠熔附纯钛小基台的方法制作种植体支持的修复体，并进行临床修复效果评价。方法机械加工制作颈环及轴壁薄的纯钛小基台，计算机辅助制作（computer aided manufacture，CAM）与基台匹配的全瓷冠，通过烧结遮色瓷将全瓷冠熔附于小基台上，获得修复体。对5例患者的6颗缺失牙进行修复，并对修复体进行临床效果评价。结果成功制作全瓷冠熔附纯钛小基台修复体6个。经临床评价，修复体在表面、外形、边缘及色泽等方面在修复时和修复1年后均获得满意的效果。结论全瓷冠熔附纯钛小基台修复体可作为种植义齿美学修复的新选择。     

Deflection fatigue of Ti-6Al-7Nb, Co-Cr, and gold alloy cast clasps

STATEMENT OF PROBLEM: There is little information about the deflection fatigue of clasps in relation to stress distribution. PURPOSE: The aim of this study was to investigate the fatigue resistance and permanent deformation of cast clasps made of titanium and other dental alloys and to relate the fatigue resistance with the calculated stress values. MATERIAL AND METHODS: Twenty-five Ti-6Al-7Nb, 25 Co-Cr, and 15 Type IV gold alloy clasps were subjected to cyclic deflection of preset values of 0.25 mm, 0.50 mm, or 0.75 mm, for 10 6 cycles (n = 14). Finite element models were created to calculate principal stresses within the specimens. Fatigue life, retentive force, and permanent deformation were recorded, and the fracture locations were determined microscopically. The results were characterized in relation to the stress within the clasps. One-way analysis of variance and Tamhane's post-hoc tests were used to compare the results of the 9 material-deflection groups (alpha=.05). RESULTS: Ti-6Al-7Nb clasps exhibited significantly less permanent deformation than the other clasps under relatively greater deflections, indicating better adaptation to the tooth surface. However, the fatigue life of the Ti-6Al-7Nb clasps under 0.75-mm deflection, with the stress above the alloy's 0.2% yield strength, was significantly shorter than those under smaller deflections. The gold clasps showed significantly longer fatigue life than the other clasps under the 0.50-mm deflection. High-stress areas within the fatigue clasp specimens coincided with the fracture locations. The probabilities of fatigue fracture and permanent deformation were closely related to the material strengths and the preset deflections. CONCLUSION: To minimize fatigue failures, the cast clasp should be designed with consideration of the stresses distributions within the clasps.     

暂时性固定修复体在牙种植体颈部的覆盖形式与愈合期疗效的关系

目的了解牙种植术后戴用的暂时性固定修复体的颈部采用何种覆盖形式效果最好。方法通过对42件暂时性固定修复体的复查，采用多指征方法评价分析修复体在种植体颈部的覆盖形式与其在愈合期疗效的关系。结果修复体在牙种植体颈部为半暴露或全暴露形式较全覆盖形式容易引起病员不适感和食嵌感，但有利于牙龈健康。结论如果为了愈合期的牙龈健康及种植体的早期稳固。应该设计为半暴露或全暴露形式。如果间距离小，种植基桩短，或者为了满足病员舒适感的要求，不得不将颈缘设计为全覆盖形式。     

质粒介导变形链球菌转化的研究

本研究建立了变形链球菌ＭＴ８１４８转化系统。在本组转化培养条件下，变形链球菌ＭＴ８１４８在对数生长早期出现感受态但维持时间很短，供体ＤＮＡ最适浓度为２５μｇ／ｍｌ，超螺旋闭环质粒与线性质粒均可转化变链ＭＴ８１４８。与变链ＧＳ５相比，变链ＭＴ８１４８的转化率约低１００倍     

Compliance with infection control programs in private dental clinics in Jordan

The aim of this study was to assess the compliance of general dental practitioners (GDPs) in the private sector in North Jordan with infection control measures. A pilot-tested questionnaire about infection control measures was distributed in March 2004 to 120 private practices. The response rate was 91.66 percent. About 77 percent of dentists usually ask their patients about medical history, 36 percent were vaccinated against hepatitis B, 81.8 percent wear and change gloves during treatment and between patients, and 54.5 percent wear and change masks during treatment and between patients. Most dental practitioners (95.4 percent) reported that they changed extraction instruments and burs between patients. All dental practitioners reported that they changed saliva ejectors between patients, but only 41.8 percent changed handpieces between patients. Approximately 63 percent (69/110) used autoclaves for sterilization, 47.3 percent (52/110) used plastic bags to wrap sterilized instruments, and only 18 percent (20/110) disinfected impressions before sending them to dental labs. Fourteen percent used rubber dams in their clinics, and only 31.8 percent had special containers for sharps disposal. Based on these responses, approximately 14 percent of general dentists in this sample were considered to be compliant with an inventory of recommended infection control measures. In Jordan, there is a great need to provide formal and obligatory infection control courses and guidelines for private dentists by the Ministry of Health and the dental association in addition to distribution of standard infection control manuals that incorporate current infection control recommendations.     

体外人牙髓细胞的矿化特性

为探讨体外人牙髓细胞的生物学特性，采用体外细胞连续培养、钙质染色、Ｘ射线能谱分析与透射电镜观察等方法，对体外人恒牙牙髓细胞的矿化特性进行了研究并与人牙龈成纤维细胞（ｈｕｍａｎｇｉｎｇｉｖａｆｉｂｒｏｂｌａｓｔｓ，ＨＧＦｓ）进行了比较。结果表明，人牙髓细胞在体外可以复层生长并形成细胞结节，ＨＧＦｓ则无此能力，牙髓细胞的碱性磷酸酶活性亦较ＨＧＦｓ者高；细胞结节钙质染色呈阳性，结节内钙磷含量明显增高；人牙髓细胞有许多与成牙本质细胞相似的超微结构特征，胞间基质中可见致密晶状小体。结果提示，体外连续培养的人牙髓细胞有向成牙本质细胞分化的可能，这可为研究人牙髓细胞的分化和矿化提供有价值的思路。     

Induction of Sca-1 in the duct cells of the mouse submandibular gland by obstruction of the main excretory duct

The effect of ligation of the main excretory duct (MED) of the mouse submandibular gland (SMG) on the expression of Sca-1, a stem cell antigen, was examined by Western blotting and immunohistochemistry. By Western blotting, the expression of Sca-1 with a molecular weight of 18 kDa was identified in the normal gland. At 1 day post-ligation, the expression level of Sca-1 was strongly increased in the experimental gland and weakly in the contralateral gland, and such expression in both glands decreased at 6 days. By immunohistochemistry, Sca-1 was detected weakly in the apical membrane of excretory duct (ED) cells of the SMG under the normal condition. By duct ligation, Sca-1 became expressed strongly in most cells of the two major duct systems, i.e., the striated duct (SD) and granular convoluted tubules (GCT), but was not detected in the acinar (Ac) cells. By fluorescence-activated cell sorter (FACS) analysis, the number of side population (SP) cells in this gland was found to be increased by ligation. These results imply that Sca-1-positive cells may have a role in the duct cell proliferation in the regeneration step elicited by MED ligation-induced injury.     

The fatigue life of a cobalt-chromium alloy after laser welding

The aim of this study was to investigate the fatigue life of laser welded joints in a commercially available cast cobalt-chromium alloy. Twenty rod shaped specimens (40 mm x 1.5 mm) were cast and sand blasted. Ten specimens were used as controls and the remaining ten were sectioned and repaired using a pulsed Nd: YAG laser welder. All specimens were subjected to fatigue testing (30N - 2Hz) in a controlled environment. A statistically significant difference in median fatigue life was found between as-cast and laser welded specimens (p < 0.001). Consequently, the technique may not be appropriate for repairing cobalt chromium clasps on removable partial dentures. Scanning electron microscopy indicated the presence of cracks, pores and constriction of the outer surface in the welded specimens despite 70% penetration of the weld.     

新型重组人血小板衍化生长因子B腺病毒载体的构建与转染牙周干细胞的研究

目的 构建人血小板衍化生长因子B(platelet-derived growth factor-B,PDGF-B)重组复制缺陷型腺病毒载体,使其感染牙周韧带干细胞(periodontal ligament stem cells,PDLSC)并检测其相关生物学变化.方法 采用常规分子生物学方法,构建重组穿梭载体PAdTraekCMV-PDGF-B,用Pine I酶线性化后,线性化质粒在细菌BJ5183内与腺病毒骨架载体质粒AdEasy I同源重组,构建重组腺病毒质粒pAd-PDGF-B,在HEK293细胞中包装成重组腺病毒Ad-PDGF-B.Western blotting法检测其在HEK293中的表达情况,同时利用包装好的病毒感染PDLSC,用免疫组化的方法鉴定PDGF-B在细胞中的表达;采用甲基噻唑基四唑(MTr)法检测感染病毒后PDLSC的增殖变化,用反转录聚合酶链反应(RT-PCR)检测感染后细胞分泌I型胶原的变化.结果 重组缺陷型腺病毒载体经限制性内切酶酶切分析鉴定,与预期结果一致.重组质粒转染HEK293细胞3 d后即可观察到绿色荧光蛋白(green fluorescence protein,GFP)明显表达,Western blotting检测证实PDGF-B表达.重组病毒能够感染PDLSC并表达蛋白,MTT结果显示感染Ad-PDGF-B后的PDLSC增殖能力明显加强.在感染后第4天,感染Ad-PDGF-B后的PDLSC组吸光度值为(0.68±0.02),与对照组相比差异有统计学意义(P＜0.01).同时I型胶原表达量增高.结论 利用新型腺病毒载体AdEasy系统可快速构建同时表达EGFP和PDGF-B的重组复制缺陷型腺病毒Ad-PDGF-B,此病毒能够感染PDLSC并促进其增殖,同时增强I型胶原的表达,为牙周病患者牙周组织再生和种植体周韧带重建的基因治疗奠定基础.     

儿童口腔科医师实施行为管理相关问题调查分析

目的 对儿童口腔科医师在门诊工作中与行为管理有关的工作内容及医生的工作压力进行调查，并就相关因素进行分析。方法 对参加第五届全国儿童口腔医学会议的139名医生进行问卷调查，并对有关因素进行分析。结果 在大学附属医院工作的医生更倾向于进行母子分离、过去一个月内44．6％的医生接诊过有行为问题的儿童。获得了具体各种行为管理方法应用情况的资料。另外51．5％的医生感觉门诊工作有比较大的压力。结论 目前儿童口腔医生在镇静全麻等特定方法的应用上还有待加强，工作压力所可能导致的对健康的影响不容忽视。