不同烘烤温度下铸造镍铬合金对钛接圈内层污染的研究

目的：评价不同烘烤温度下铸造镍铬合金后，钛接圈内层污染及成分扩散程度。方法：选择临床骨融合种植义齿二期手术后典型病例石膏模型，在基托上固定纯钛接圈，常规制作桥架蜡型，使桥架接圈周围嵌体厚度为１ｍｍ，常规内外层包埋，放置２４ｈ后，分４组不同温度烘烤：ａ组升温至６００℃，ｂ组升温至６５０℃，ｃ组升温至７００℃，ｄ组升温至８００℃。每组试件１０个，共４０个试件。用远红外温度测试仪控制合金浇注温度为１３０６℃，自然冷却，喷砂打磨将有钛接圈部位制作金相试件，进行电镜、能谱分析。结果：不同烘烤钛接圈温度熔合镍铬合金均存在钛接圈内表面污染，有包埋料成份，也有镍铬合金成份，范围达０．６ｍｍ。结论：烘烤温度在６５０℃－７００℃时，钛接圈内层包埋料污染程度相对较小。     

烘烤温度对钛接圈与Ni—Cr合金结合界面性能的影响

目的：找出适宜烘烤温度使钛接圈与Ｎｉ－Ｃｒ合金形成最理想的界面结合。方法：选定６００℃、６５０℃、７００℃、８００℃钛接圈烘烤温度，浇注Ｎｉ－Ｃｒ合金的结合体。显微硬度计、扫描电镜、能谱分析仪，对钛接圈、结合界面、Ｎｉ－Ｃｒ合金部进行分析。结果：（１）钛接圈烘烤６００℃、８００℃，铸入Ｎｉ－Ｃｒ合金，扫描电镜发现有明显的界面反应区。（２）６５０℃、７００℃时铸入Ｎｉ－Ｃｒ合金，两金属间出现金属－金属接合形成区，该部Ｖｉｃｋｅｒ硬度与Ｎｉ－Ｃｒ合金、钛接圈硬度差异不大，但也有部分界面反应。（３）能谱分析显示在Ｎｉ－Ｃｒ合金部、接合部、钛接圈部均有Ｎｉ、Ｃｒ、Ｔｉ、Ｍｏ、Ｓｉ等元素，且Ｔｉ元素检出较少。结论：选用钛接圈烘烤温度为６５０℃～７００℃条件下，浇注Ｎｉ－Ｃｒ合金较好，益于种植瓷修复体质量。     

种植义齿桥架接圈铸造失败的能谱及电镜分析

纯钛接圈与钴铬合金熔合质量是可摘式杆附着全口种植覆盖义齿桥架成功的关键。通过对铸造失败的桥架接圈进行临床观察、扫描电镜（ＳＥＭ）和能谱分析（ＥＤＡ），发现桥架接圈铸造成功与温度合理控制密切相关。在目前工作条件下，以纯钛桥架接圈浇注钴铬合金完成桥架，存在温度过高，纯钛接圈有熔解，造成部分桥架失败。     

衔铁与不同金属铸接前后金相结构的比较

目的:用铸接法制作磁性覆盖义齿根面结构,分别采用不同合金进行常规铸造,观察不同合金铸造温度对衔铁金属显微结构的影响。方法:分别采用金合金、镍铬合金、纯钛与Magdisc500成品衔铁包埋铸造、抛光、平整、清洁并制作金相试件。用金相显微镜对铸接前后的衔铁进行金相分析,以成品衔铁作为对照。结果:与铸造前相比,金合金组衔铁晶粒无明显变化。镍铬合金组、纯钛组衔铁晶粒变大、变粗,纯钛组更为粗大。结论:用不同合金铸接衔铁,会对衔铁的金相产生影响;合金铸造温度越高,晶粒越粗大。金合金组影响最小。     

铸接式衔铁吸附面性状的实验研究

目的:用铸接法制作磁性覆盖义齿根面结构,分别采用不同合金行常规铸造,观察不同合金铸造温度对衔铁吸附面性状的影响。方法:采用金合金、镍铬合金、纯钛,分别与Magdisc500成品衔铁包埋铸造,制作根面结构。用扫描电镜和电子探针对打磨抛光前衔铁表面附着物进行形貌观察和成分分析。结果:金合金组及镍铬合金组衔铁表面无氧化物生成,纯钛组衔铁表面有氧化物生成,3组试件衔铁表面的附着物均有包埋料残余。结论:不同铸造温度的合金会对衔铁吸附面产生不同的影响,提示临床上应采用金合金或镍铬合金铸接衔铁。     

甲基丙烯酰氧基丙基三甲氧基硅烷对3种不同金属与Filtek树脂粘接强度的影响

目的研究经甲基丙烯酰氧基丙基三甲氧基硅烷（γ-MPS）偶联剂处理的3种不同金属的粘接表面对FiltekZ350树脂粘接强度的影响。方法用失蜡铸造法制备镍铬合金、纯钛、金钯合金试件各12个,共36个。每种金属随机平分为实验组和对照组,每组6个。实验组用γ-MPS对粘接面进行处理后与Filtek Z350树脂粘接,对照组粘接面不用γ-MPS处理。测试每组试件断裂时的剪切力,并用扫描电子显微镜（SEM）观察试件断面的形貌。结果镍铬合金实验组、纯钛实验组较相应对照组的剪切强度高,差异有统计学意义（P<0.001）;金钯合金实验组与其对照组的剪切强度无明显差异（P>0.05）。实验组内比较：纯钛组剪切强度高于镍铬合金组,两者又均高于金钯合金组（P<0.01）。所有试件均为黏结断裂。与对照组相比,镍铬合金和纯钛实验组断裂面有较多的树脂突,而金钯合金实验组断裂面树脂突较少。结论γ-MPS可以提高金属和树脂的粘接力,但和金属成分有关。γ-MPS能增加纯钛、镍铬合金与树脂的粘接性能,但不能认为γ-MPS可以增加金钯合金与树脂的粘接性能。     

4种金属基底试件对烤塑修复表面颜色的影响

目的:将钛基底烤塑修复体试件与镍铬合金、Bio-GG金合金、captek金合金基底试件烤塑后进行色彩学对比分析,研究钛基底对烤塑修复体表面颜色的影响。方法:分别以纯钛、Bio-GG金合金c、aptek金合金、镍铬合金片为基底制作0.5 mm、0.7 mm、0.9 mm、1.1 mm、1.3 mm、1.5 mm树脂层厚度的烤塑试件。利用美能达CR-321型色差计对试件进行测色,计算色差值并进行统计分析。结果:钛基底组的试件,随树脂层厚度的增加,其色差值ΔE显著减小,当树脂厚度>1.1 mm,前后两组的ΔE已无统计学差异(P>0.05);线钛组色彩学特性与Bio-GG金合金组及captek金合金组之间无显著性差异,而与镍铬合金组有差异(P<0.05)。结论:钛基底烤塑修复体的树脂层厚度应大于1.1mm;随树脂层厚度的增加,修复体的亮度、彩度均减小,色相由红向绿转变。相同树脂层厚度时,钛基底组修复体色彩与Bio-GG金合金、captek金合金基底组无差别,优于镍铬合金基底组。     

五种烤瓷合金金瓷结合强度的比较

目的：比较镍铬合金、含钛的镍铬合金、钴铬合金、钯银合金和纯钛的金瓷结合强度。方法：执行ISO9693标准,采用三点弯曲试验分别测定镍铬合金、含钛的镍铬合金、钻铬合金、钯银合金、纯钛在常规热处理条件下的金瓷结合强度。结果：金瓷结合强度分别为：镍铬合金（37．82±2．72）Mpa;含钛的镍铬合金（39．23±2．45）Mpa;钴铬合金（39．06±3．41）Npa;钯银合金（47．98±3．74）Npa;纯钛（32．61±5．62）Mpa。镍铬合金、含钛的镍铬合金、钻铬合金组间差异无统计学意义（P〉0．05）,这3种合金与纯钛、钯银合金组间差异都有统计学意义（P〈0．05）,纯钛与钯银合金组间差异也有统计学意义（P〈0．05）。结论：①镍铬合金、含钛的镍铬合金、钴铬合金金瓷结合强度相近,都大于纯钛且小于钯银合金的金瓷结合强度。②镍铬合金、含钛的镍铬合金、钻铬合金、钯银合金和纯钛的金瓷结合强度都大于25Mpa,按ISO9693标准均可应用于临床。     

3种牙科铸造金属模拟唾液浸泡后粗糙度的变化

目的：通过考察钴铬合金、镍铬合金以及纯钛在不同pH值人工唾液中浸泡后表面粗糙度的变化，研究3种常用牙科金属的耐腐蚀能力。方法：将3种金属的标准铸造试件逐级打磨抛光后。浸泡于pH值分别为7．0和5．6的人工唾液中。3个月后检测试件表面粗糙度，并用金相显微镜观察试件表面。采用SPSS11．0软件包对数据进行单因素方差分析及t检验。结果：pH=5．6的人工唾液浸泡后，3种材料表面粗糙度有显著差异，镍铬合金〉钴铬合金〉纯钛金属（P〈0．01）。pH=7．0的人工唾液浸泡后，镍铬合金表面粗糙度大于钴铬合金和纯钛（P〈0．01），但钴铬合金和纯钛之间无统计学差异（p〉0．05）。pH=5．6人工唾液浸泡组的镍铬合金和钴铬合金表面粗糙度大于pH=7．0组的同种材料（P〈0．01）。各试验组表面粗糙度大小与显微镜观察到的材料表面腐蚀程度一致。结论：纯钛在酸性和中性环境下均有较强的耐腐蚀性，钴铬合金、镍铬合金在酸性介质中的耐腐蚀性较差。3种金属的耐腐蚀性由大到小排列为：纯钛金属〉钴铬合金〉镍铬合金。     

龈下优势菌在金合金、镍铬合金与纯钛表面黏附的实验观察

目的研究龈下优势菌在种植钛与冠修复材料表面的黏附特征。方法将烤瓷冠修复的两种基底冠材料（金铂合金、镍铬合金）分别粘接在种植纯钛板上，与四种龈下优势菌：伴放线放线杆菌（Aa），牙龈卟啉单胞菌（Pg），具核梭杆菌（Fn），中间普氏菌（Pi）共同厌氧孵育，采用菌落形成单位计数法（CFU）量化测定培养试件表面的细菌黏附量；扫描电镜（SME）观察试件表面细菌黏附的情况。结果四种龈下优势菌在金铂合金-钛试件表面细菌黏附量明显多余镍铬合金-钛试件。结论四种龈下优势菌单独附着能力有差异，Aa〉Fn〉Pg〉Pi。金铂合金的组织相容性优于镍铬合金。     

不同剂型玻璃离子水门汀溶解性比较研究

目的:研究、比较不同剂型玻璃离子水门汀的溶解性和表面微观形态改变,为临床使用提供依据.方法:将3M树脂加强型玻璃离子水门汀(水粉剂型)、GC玻璃离子水门汀(水粉剂型)及GC玻璃离子水门汀(双糊剂型)分别在人工唾液中浸泡30 d,冷热循环15000次,烘干测重,比较前后质量变化,计算溶解率,并用扫描电镜观察表面微观改变.结果:不同剂型的玻璃离子水门汀溶解率由高到低分别为3M树脂加强型玻璃离子水门汀(水粉剂型)、GC玻璃离子水门汀(水粉剂型)、GC玻璃离子水门汀(双糊剂型).3种玻璃离子水门汀经浸泡溶解后,SEM扫描表面微观形态可观察到GE玻璃离子水门汀(双糊剂型)表面形态改变较少,其他2组玻璃离子水门汀表面微观改变较多.结论:双糊剂型玻璃离子水门汀理化性能及溶解率均低于传统水粉剂型,是未来临床修复治疗的的良好选择.     

Evidence of the validity of a model of determinants of quality of restorative dental care

A model describing the relationship between self-reported quality of restorative dentistry and dentist characteristics for 119 Montana general dentists is presented. The best predictors formed a significant model explaining 22% of the variance of the quality measure. Results are contrasted with a previous estimation of the model for 102 Washington general practitioners. Evidence for the external validity of the model is presented.     

Design of clinical trials of traditional therapies of periodontitis

The present paper on the design of clinical trials of periodontal therapy first addresses the issue of the etiology of periodontal disease. It is suggested that most if not all forms of destructive periodontal disease are caused by microorganisms and that there are different forms of disease with different microbial etiologies. The progressive nature of destructive periodontal disease is subsequently discussed and it is emphasized that, in a given patient, periodontal sites which show signs of inflammation and attachment loss may not over a period of several months and years show further sign of attachment loss. The present methods of assessing periodontal disease do not allow us to discriminate between potentially active and inactive sites in untreated patients. The significance and variability of indicators of periodontal disease such as bleeding on probing, probing pocket depth and probing attachment level measurements are discussed. The errors inherent in the various measurements are analyzed and suggestions are presented describing how alterations in any of the above parameters could be identified and presented in a clinical trial. Of concern for the statistical analysis of clinical data of periodontal disease is the definition of the "experimental unit". For a number of years, the "experimental unit" in periodontal trials was the patient. It is clear, however, that different sites within the same individual show different patterns of disease progression and lesion morphology and often respond differently to periodontal therapy. Statistical analyses must consequently be designed which recognize differences in site-to-site infection and lesion morphology within a common host. Until such analyses are available, the investigator should be wary of pooling data within the same individual, since such pooling may obscure meaningful alternatives which may take place in individual periodontal sites. Some goals of periodontal therapy are subsequently identified. 4 goals are discussed more in detail, namely: to establish conditions which will allow the patient to maintain a dentition without further breakdown of the periodontium; to reduce pocket depth to establish an anatomy in the dentogingival region which with proper maintainance care will prevent the re-establishment of the subgingival infection; to gain attachment as a result of treatment; to assess the effect of a certain chemotherapeutic agent on periodontal disease.     

Experimental evidence of formation of imines in the course of reduction of hydrazones

The reduction of hydrazones is generally suggested to proceed through a reductive cleavage of the nitrogen–nitrogen bond followed by a reduction of the carbon–nitrogen bond. This sequence of reduction processes is here supported for fluorenone (V) and benzophenone (VI) hydrazones as well as by a comparison of the reduction of fluorenone and benzophenone hydrazonium ions (I,III) with corresponding imines (II,IV). Another proof of the presence of imines as intermediates is the splitting of four-electron waves of hydrazones V and VI and hydrazonium ions I and VIII into two waves at pH < 2. This has been interpreted as due to differences in slopes dE_1/2/dpH and pK_a-values of protonated hydrazine derivatives on one side and corresponding imines on the other. In this pH-range imines formed in reductions of VI and VIII are reduced in a single two-electron wave, those of I and V in two one-electron steps. Fluorenone imine (II) is sufficiently stable to allow recording of time-independent current–voltage curves between pH 6 and 11. In this pH-range the imine (II) is reduced in two one-electron steps. Benzophenone imine (IV) has been found stable between pH 4.6 and 12. At pH 4.6–8 the reduction of the imine IV takes place in a single two-electron step, at pH 8–12 in two one-electron steps. Final proof of the initial cleavage of the N–N bond is presented by comparison with the reduction of nitrones.     

Evaluation of efficacy of chemiluminescence for diagnosis of leukoplakia

ObjectiveLeukoplakia is the most common potentially malignant disorder preceding oral cancer. Chemiluminescence has been developed as an adjunct to conventional examination for the diagnosis of these potentially malignant disorders. This study was conducted to assess the efficacy of chemiluminescence in the diagnosis of leukoplakia and to compare the results with histopathological examination.Study designA total of 50 patients with leukoplakia were included from the outpatients attending the Department of Oral Medicine and Radiology, Dental Hospital, Bengaluru, Karnataka, India. These patients were subjected to conventional oral examination followed by chemiluminescent examination with Vizilite (Zila, Fort Collins, CO, USA) and biopsy for histopathological confirmation.ResultsThe sensitivity, specificity, positive predictive value, and negative predictive value of chemiluminescence were 93.75%, 55.56%, 78.95%, and 83.3%, respectively. The overall accuracy of chemiluminescence was 80%. A statistically significant association was observed between histopathology results and chemiluminescence results.ConclusionAlthough it is an easy, safe, minimal time consuming, and noninvasive technique, it has only adjunctive utility and it does not replace biopsy for the diagnosis of leukoplakia.     

正常青年Monson球面半径的测量研究

目的测量正常青年Monson球面半径。方法选择60名(男30名,女30名)正常青年制取全口印模,应用立体摄影成像的原理与方法对Monson球面半径进行测量和统计学处理。结果Monson球面的半径平均为10.173 cm,大于理论值10.160 cm,差异有显著性(P<0.01);男、女性球面半径差异无显著性。结论本实验所得到的数据可作为全口义齿修复中记录颌位关系的一个参量。     

正畸患者切牙影像失真发生情况分析

目的研究正畸患者曲面体层片上的切牙影像失真发生情况，并分析其原因。 方法从中山大学附属口腔医院放射科影像数据库中选取500例正畸患者的曲面体层片和头影测量侧位片，所有曲面体层片均采用咬合杆投照，分别从切牙牙体影像放大、缩小、牙根变短、根尖模糊等评价指标分析上下颌切牙影像失真的发生情况，在头影测量侧位片上测量中切牙根尖-对颌切牙切缘的距离，探讨切牙影像失真发生的原因。采用SPSS 19.0统计软件对所得数据进行统计学检验。 结果500例患者中，切牙牙体影像正常者共417例，切牙牙体影像失真者共83例，影像失真发生率16.6%，其中切牙牙体影像放大17例、牙体影像缩小0例、牙根变短30例，牙根影像变短伴模糊36例。影像失真患者的根尖-切缘距离大于影像正常的患者，差异有统计学意义（F = 5 187.18，P = 0）；影像失真患者的覆盖值大于影像正常的患者，差异有统计学意义（F>477，P = 0）。 结论严重牙颌面畸形如反 、深覆盖是导致曲面体层片的切牙影像失真的主要原因之一。     

颌骨动静脉畸形的栓塞治疗

目的：总结直接穿刺结合经血管内介入栓塞治疗颌骨动静脉静脉畸形的经验。方法：收治凳骨动静脉畸形患者6例,均进行了介入栓塞治疗。采用的栓塞材料为附凝血棉纤毛的螺圈,聚乙烯醇泡沫微粒和二氰基丙烯酸对丁酯。数字减影颈动脉造影在PHILIPSV300下完成。结果6例颌骨动静脉畸形患者中4,例急性出血得到了快速、有效控制,1例慢性渗血的右下 骨动静脉畸形患者,介入栓塞治疗,拔除松动的右下凳第一磨牙,有效地控制了出血,另1例伴局部软组织搏动性膨隆的上凳骨动静脉畸形患者,介入治疗后膨隆的搏动性得到明显改善,栓塞治疗后分别随访3－24个月,均未发现有口腔内渗血或出血。随访的X线片上,病灶区可见新骨形成。结论：局部穿刺结合经血管内介入栓塞治疗颌骨动静畸形是一种安全、有效的治疗方法。     

Electrodeposition of bilayers of dithiols

We report an electrochemical method to form a bilayer of dithiol. The cyclic voltammogram of the oxidative deposition of an aromatic dithiol on gold from an alkaline aqueous solution reveals two current peaks separated by more than 400 mV. The integrated charge of the oxidative current peak (B) at the most positive potential is twice that of the other oxidative current peak (A). These two oxidative current peaks were characterized by differential capacitance and electrochemical quartz crystal microbalance (EQCM) measurements. A decrease of the capacity by a factor of two, and an increase of the EQCM frequency change by a factor of two were observed when the potential was scanned from a value where only the first oxidative peak (A) is obtained, to a potential where both oxidative current peaks (A and B) are obtained. Infrared spectra show that the aromatic dithiols adsorb vertically at potentials corresponding to the current peak A and they become tilted for potentials corresponding to the current peak B. The simple relationships between the properties of the two oxidative current peaks are found to be compatible with a step-wise oxidative deposition of a bilayer of dithiol.