烧结次数对两种合金烤瓷颜色的影响

目的:探讨烧结次数对金铂合金烤瓷及镍铬合金烤瓷颜色的影响。方法:制作直径14mm,厚度0.35mm的金铂合金烤瓷及镍铬合金烤瓷2组标准试件各15个,每组再分为3小组,分别上遮色瓷(A2色)0.2mm和不同厚度的体瓷(A2色)0.3mm,0.6mm,0.9mm。用美能达CR-100色度计测量试件上遮色瓷、体瓷烧结1、3、5、7次后的L*a*b*均值,计算两种合金烤瓷颜色(A2色)烧结次数间的色差△E。结果:金铂合金烤瓷及镍铬合金烤瓷均为体瓷烧结3次时色差△E最小,烧结5次时色差△E增大,烧结增至7次色差△E稍有降低。结论:临床金属烤瓷修复时,虽然烧结次数达到7次时对色差的影响都较小,但还是适宜控制在7次内。随着烧结次数增加,金铂合金烤瓷的色泽稳定性较镍铬合金烤瓷更佳。     

金铂合金与镍铬合金烤瓷颜色和金瓷结合强度的比较研究

目的 探讨金铂合金烤瓷与镍铬合金烤瓷颜色和金瓷结合强度的差别,为临床选择修复材料 提供理论依据。方法 ①制作不同体瓷厚度的金铂、镍铬合金烤瓷圆盘试件各15件,用美能达CR-100色 度计测量试件上遮色瓷、体瓷后的L、a、b值,计算两种金属烤瓷颜色(A2)间的色差△E。②制作金铂、镍铬 合金烤瓷棒盘试件各5件,通过剪切实验测量金瓷结合强度。结果 ①金铂合金烤瓷颜色比镍铬合金烤瓷颜 色要偏黄、偏红,明度小,两种金属烤瓷颜色(A2)的色差△E在遮色瓷时最大,随体瓷增厚而减小。②金铂合 金烤瓷金瓷结合强度85.08±15.16MPa,镍铬合金烤瓷金瓷结合强度54.76±8.74MPa,统计学分析P<0.05。结论 金铂合金烤瓷不仅金瓷结合强度高,不易崩瓷,而且颜色更接近天然牙。     

嵌体修复体的微渗漏研究

目的：使用两种黏结剂黏结5种不同嵌体材料，观察其边缘微渗漏情况，为临床选择嵌体材料和黏结剂提供参考。方法：选择近期拔除的24个完整磨牙，制备成近中殆远中面洞，随机分为8组，每实验组3个牙。1～3组：为金合金、钛合金、镍铬合金嵌体，使用3M ESPE RELY X^TM ARC黏结；4～6组：为金合金、钛合金、镍铬合金嵌体，使用SHOFU CX-Plus Glass poly alkenoqte黏结；7～8组：为铸瓷、水晶瓷嵌体，使用SHOFU CX-Plus Glass poly alkenoqte黏结。经恒温保存，5g／L碱性品红染色24h，2次纵剖牙体后，体视显微镜观测微渗漏值。结果：在两种黏结剂黏结下，金合金嵌体的微渗漏值最小，镍铬合金嵌体的微渗漏值最大。在松风玻璃离子黏结下，瓷嵌体组的微渗漏值小于钛合金的微渗漏值。结论：金合金、钛合金、铸瓷、水晶瓷嵌体均能满足临床修复需要。临床应用镍铬合金嵌体时应选择合适的黏结剂。     

金铂合金烤瓷与镍铬合金烤瓷颜色差别的初步研究

目的　探讨金铂合金烤瓷与镍铬合金烤瓷颜色的差别。方法　制作不同体瓷厚度的金铂、镍铬合金烤瓷试件各 1 5件 ,用美能达CR1 0 0色度计测量试件上遮色瓷、体瓷烧结 1、3、5、7次后的L 、a 、b 值 ,计算两种金属烤瓷颜色 （A2 ）间的色差△E。结果　金铂合金烤瓷比镍铬合金烤瓷颜色要偏黄、偏红 ,明度小 ,两种金属烤瓷颜色 （A2 ）的色差△E在遮色瓷时最大 ,上体瓷后减小 ,体瓷烧结 3次时最小 ,后随着烧结次数的继续增多增大 ,除在体瓷烧结 3次时△E小于 1 5外 ,其余均大于 1 5 ;两种金属烤瓷颜色 （A2 ）的色差△E随体瓷增厚而减小 ,但均大于1 5。结论　临床修复应注意两种金属烤瓷颜色间的差别 ,以利于提高比色质量。     

两种金沉积基底冠熔结镍铬桥体烤瓷桥的三维有限元应力分析

目的 用三维有限元法对两种桥体设计的金沉积基底冠熔结镍铬桥体烤瓷桥进行应力分析,以期为烤瓷桥的临床修复设计提供参考.方法 建立两种金沉积基底冠熔结镍铬桥体烤瓷桥(桥体固位部分分别设计为半包型和环状型)的三维有限元模型,分别在桥体袷面中央窝轴向加载200 N垂直载荷和从桥体颊(牙合)边缘嵴中央指向舌侧、与(牙合)平面成30°角方向加载400 N侧方载荷,分析两种模型的应力分布.结果 两种烤瓷桥的应力分布基本相似,最大主应力集中区主要位于远中连接体.垂直加载时,半包型和环状型镍铬桥体的最大主应力分别为24.17 MPa和24.85 MPa;侧方加载时,两者最大主应力分别为42.83 MPa和42.69 MPa.垂直加载时和侧方加载时,金沉积基底冠的边缘区为最大主应力区.结论 金沉积基底冠熔结镍铬桥体烤瓷桥的应力集中于连接体,金沉积基底冠边缘是薄弱区.     

垫底厚度对全瓷嵌体修复应力分布影响的三维有限元分析

目的 通过对不同垫底厚度上颌前磨牙全瓷嵌体修复进行三维有限元分析,了解垫底厚度对全瓷嵌体修复应力分布的影响.方法 建立垫底厚度分别为0.5mm,1.0mm和1.5mm的上颌前磨牙邻(牙合)面缺损嵌体修复三维有限元模型,采用3种垫底材料,应用ANSYS10.0有限元分析软件,计算分析应用3种不同厚度垫底时,嵌体和剩余牙体组织的应力分布状况.结果 随着垫底厚度的变化,嵌体、牙釉质和牙本质的最大拉应力,以及粘结剂层的最大剪切力均发生变化.嵌体的最大拉应力、粘结剂层的最大剪切力随着垫底厚度的增加而逐渐增加,当垫底厚度为0.5mm时牙釉质中的最大拉应力最小,而牙本质中的最大拉应力最大.使用不同垫底材料时,随垫底厚度增加,嵌体中的最大拉应力上升的幅度有所不同,玻璃离子垫底组上升的幅度最大,复合体组次之,树脂垫底组上升幅度不明显.结论 弹性模量较低的垫底材料其厚度的变化对嵌体应力改变的影响明显,弹性模量高的垫底材料其厚度的变化对嵌体应力改变的影响不明显.     

不同材料嵌体与牙体间的边缘密合度研究

目的：比较三种不同材料嵌体与牙体间的边缘密合度。方法：在30颗离体牙上备洞，分别用水晶瓷、银钯合金、镍铬合金制作嵌体，在体现显微镜下测量嵌体与牙窝洞间的边缘密合度。结果：银钯合金嵌体、水晶瓷嵌体与牙窝洞边缘间的间隙较小，镍铬合金嵌体与牙间的间隙较大，且有统计学意义。结论：银钯合金嵌体、水晶瓷嵌体边缘密合度好，可满足临床牙体修复的需要。     

镍铬和含钛镍铬烤瓷合金的耐腐蚀性能研究

目的 评价2种镍铬和1种含钛镍铬烤瓷合金试件在人工唾液中的耐腐蚀性能.方法 采用电化学极化曲线法测定2种镍铬和1种含钛镍铬烤瓷合金试件的自腐蚀电流密度(Icorr)、极化电阻(Rp)、自腐蚀电位(Ecorr),并得出3种合金的极化曲线.应用场发射扫描电子显微镜(FSEM)观察实验前后试件表面形貌变化,并对数据进行单因素方差分析.结果 Bellabond镍铬烤瓷合金的Icorr低于Neotitan含钛镍铬烤瓷合金(P<0.05)及粤海镍铬烤瓷合金(P>0.05):粤海镍铬烤瓷合金Icorr低于Neotitan含钛镍铬烤瓷合金(P>0.05).Bellabond镍铬烤瓷合金的Rp明显高于粤海镍铬烤瓷合金(P<0.05)及Neotitan含钛镍铬烤瓷合金(P<0.05);粤海镍铬烤瓷合金试件的Rp高于Neotitan含钛镍铬烤瓷合金(P>0.05).Bellabond镍铬烤瓷合金的Ecorr低于粤海镍铬烤瓷合金(P>0.05)及Neotitan含钛镍铬烤瓷合金(P>0.05):Neotitan含钛镍铬烤瓷合金的Ecorr高于粤海镍铬烤瓷合金(P>0.05).FSEM显示,Bellabond镍铬烤瓷合金表面腐蚀较粤海镍铬烤瓷合金和Neotitan含钛镍铬烤瓷合金轻微.结论 Bellabond镍铬烤瓷合金的耐腐蚀性较粤海镍铬烤瓷合金和Neotitan含钛镍铬烤瓷合金优良,Neotitan含钛镍铬烤瓷合金耐腐蚀性与粤海镍铬烤瓷合金无明显差异.     

两种金属内冠烤瓷桥桥体抗压强度的比较实验

目的：比较2种临床常用非贵金属-Bego钴铬合金及VB镍铬合金做内冠的金瓷三单位烤瓷桥桥体的抗压性能，为临床金瓷内冠材料的选择提供参考。方法：常规制作钴铬合金及镍铬合金内冠烤瓷桥各10组，置6mm直径钢球于桥体胎面，用万能试验机（Zwick／z100）以1mm／min的速度加压直至试样破坏，记录破坏时的载荷作t检验分析。结果：钴铬合金和镍铬合金内冠桥的平均破坏载荷值分别为2580．058N、1739．336N。结论：Bego钴铬合金内冠桥的抗压强度明显强于VB镍铬合金内冠桥的抗压强度。     

3种不同金属烤瓷冠适合性的对照研究

目的对镍铬合金烤瓷冠、贵金属合金烤瓷冠和金沉积烤瓷冠的边缘适合性进行研究,为临床应用提供一定的理论依据和指导。方法分别制作镍铬合金烤瓷冠、贵金属合金烤瓷冠和金沉积烤瓷冠各8个,将3种烤瓷冠在无水酒精中超声清洁5 min,用聚羧酸锌黏固剂按编号将全冠黏固于各自的塑料代型上,指压就位维持10 min。将黏有冠的塑料代型用自凝塑料包埋制成小方块,用金刚砂片切机沿代型底座唇舌向直径纵剖,抛光后备测。在扫描电镜下,放大120～200倍观察冠组织面与代型粘接面间的黏固剂厚度。结果金沉积烤瓷冠与贵金属合金烤瓷冠的整体黏固剂厚度无统计学差异（P>0.05）,但二者均与镍铬合金烤瓷冠的整体黏固剂厚度有统计学差异（P<0.05）。结论金沉积烤瓷冠与贵金属合金烤瓷冠的边缘适合性优于镍铬合金烤瓷冠。     

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.     

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.     

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.     

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.