两种表面改性方法对钴-铬合金耐腐蚀性能的影响

目的:研究表面镀氮化钛膜和镀金膜后对钴-铬合金电化学腐蚀行为的影响.方法:利用多弧离子镀和电镀方法分别在钴-铬合金表面沉积氮化钛和金薄膜,通过电化学综合测试系统测试2种镀膜及未镀膜钴-铬合金试件在人工唾液中的稳态自腐蚀电位,从微机系统输入动电位扫描参数后记录其极化曲线,用系统软件进行线性极化拟合得出各试件的腐蚀电流密度和极化电阻.结果:钴-铬合金的自腐蚀电位、腐蚀电流密度和极化电阻分别为-221.54 mV、155.43 nAcm-2、167.27 kΩ,镀金试件为-146.09 mV、86.86nAcm-2、299.32 kΩ,镀氮化钛试件为-122.79 mV、65.80×10-2nAcm-2、395.15×102kΩ,镀膜试件的自腐蚀电位、极化电阻高于未镀膜者,而腐蚀电流密度降低,其中,镀氮化钛试件的各项指数变化更明显.结论:在钴-铬合金表面镀膜可以改善其耐腐蚀性,氮化钛薄膜的性能更优于金薄膜.     

两种表面改性方法对钴-铬合金化学腐蚀行为的影响

目的研究钴-铬合金表面镀氮化钛薄膜和镀金薄膜后对其化学腐蚀行为的影响。方法利用多弧离子镀和电镀方法分别在钴-铬合金表面沉积氮化钛和金薄膜,将两种镀膜和未镀膜试件分别浸入人工唾液,在37℃恒温下浸泡,在第30、60、90天定量取浸泡的人工唾液10 ml,采用原子吸收光谱法测定唾液中的钴离子含量,浸泡结束后,检测试件的重量变化。结果在3个时间点,镀氮化钛试件释出的钴离子量都显著小于镀金和未镀膜组,镀氮化钛组和未镀膜组试件浸泡前后的失重量显著小于镀金组。结论在钴-铬合金表面镀氮化钛膜可显著减少金属离子释出,提高其耐腐蚀性能,效果可靠,优于镀金。     

氮化钛镀膜对钴铬合金机械及化学性能的影响

目的研究氮化钛镀膜对牙科铸造用钴铬合金机械及化学性能的影响,为氧化钛镀膜在可摘局部义齿钴铬合金铸造支架的临床应用提供依据。方法制作钴铬合金试件79个,随机分为未镀膜组（42个）和镀膜组（37个）,镀膜组的试件采用热阴极离子镀膜技术在其表面沉积氮化钛膜。扫描电镜观察试件表面形貌;X射线衍射仪对镀膜进行物相分析;X射线荧光镀层厚度测量仪测量镀膜的厚度;划痕法测量TiN镀膜与钴铬合金基材的结合力。维氏硬度计、摩擦磨损仪和人工唾液浸泡法测量所有试件硬度、摩擦系数、耐磨性、耐腐性以及金属离子析出量。所得数据进行t检验。结果氮化钛镀膜的钴铬合金试件,硬度有所提高,摩擦系数减小,同等磨损实验条件下,镀膜组试件的磨损失重量仅为未镀膜组的1/16。试件的腐蚀电位平均值,镀膜组为-0.2453V,未镀膜组为-0.1400V（P〈0.05）。随着浸泡时间的延长,镀膜组试件析出的金属离子总量及各类离子的浓度均较低,析出离子量轻微增加;未镀膜组试件析出的各类金属离子量（铬除外）明显增加（P〈0.001）。结论氮化钛镀膜能够明显改善牙科铸造用钴铬合金的机械、化学性能。     

变形链球菌对牙科合金耐蚀性的影响

目的：探讨变形链球菌对镍铬合金、钴铬合金和金合金腐蚀性能的影响。方法：将3种牙科合金与变形链球菌在液体培养基中共同培养,以单纯培养基和空白组作为对照,8周后,进行电化学实验和扫描电镜观察。结果：电化学实验结果显示,镍铬、钴铬合金的自腐蚀电位绝对值及自腐蚀电流密度值均为培养基对照组低于变形链球菌组及空白对照组,且在变形链球菌组的合金表面不规则破裂孔明显增多。金合金各组自腐蚀电位和电流密度无统计学差异,金合金表面形貌无明显变化。结论：变形链球菌能增加口腔镍铬、钴铬合金的腐蚀倾向与腐蚀速率,但对金合金的影响不明显。     

铸造钴铬合金含银抗菌涂层表面特性及抗菌性能研究

目的：观察钴铬合金含银抗菌涂层的表面特征和抗菌性能。方法：利用真空等离子喷涂方式在铸造钴铬合金表面制备含银抗菌涂层,通过扫描电镜、能谱分析和X射线衍射分析涂层的表面性能。以常规铸造的钴铬合金试件作为对照组,含银抗菌涂层铸造钴铬合金为实验组,选用贴膜法和荧光显微镜分析法比较2组试件对变形链球菌和白色念珠菌的抗菌性能和抗黏附性能。结果：涂层表面结构均匀致密,与基底材料间未见明显间隙,表层主要物相为Ag、Cr和少量Ag2 O、Cr2 O3。抗菌结果显示,实验组2种菌的菌落数明显少于对照组菌落数（P＜0．05）,细菌黏附性明显低于对照组。结论：涂银钴铬合金涂层性能稳定,具有较好的抗菌性能和抗黏附性能。     

钴铬合金表面粗糙度对口内常见细菌黏附的影响

目的:观察并分析口腔常见菌种在不同表面粗糙度的钴铬合金修复体表面黏附和定植的数量,为临床制作良好的修复体和尽可能减少细菌在修复体表面附着和定植提供参考.方法:所有钴铬合金样本按不同步骤打磨抛光后,应用表面粗糙度仪MAHR M1测试其表面粗糙度,按不同粗糙度分为6组.将6组试件放入含有变形链球菌(Ua)、内氏放线菌(An)和牙龈卟啉单胞菌(Pg)的混合培养基中作厌氧培养,24h后分别定量检测各组试件表面黏附的细菌数量以及液体培养基中的细菌数量,将结果采用SPSS6.0软件包进行方差分析.结果:各组试件的表面粗糙度有显著差异(P<0.05).各组试件表面及液体培养基中均检测不到Pg,24h后,Ua和An在钴铬合金各组表面黏附定植的数量均有显著差异(P<0.05),细菌定植总数也有显著差异(P<0.05).结论:3种细菌混合培养时,Pg受到强烈的抑制.钴铬合金不同的表面粗糙度导致细菌黏附定植数量显著差异,粗糙度越大,细菌黏附量越多.临床应采用高度抛光的钴铬合金修复体,以尽量减少修复体表面的细菌黏附.     

牙科钴铬合金表面镀氮化锆层后的耐磨性研究

目的：评价钴铬(Co-Cr)合金表面经镀氮化锆膜后的耐磨损性,为口腔临床要求的基底表面处理方式提供参考依据。方法运用磁控溅射镀膜技术,设定基体加热温度200℃恒定,分别在①功率为100w、氮气分压选择为25%、35%、45%以及②氮气分压35%,功率为50w、100w、200w的条件下,在Co-Cr合金表面沉积氮化锆涂层,采用磨损试验机测试并比较氮化锆涂层和未镀膜之间的耐磨性能。结果镀氮化锆试件的失重量显著小于未镀膜试件(P<0.05).其中当镀膜的功率和基体温度恒定条件下,氮气分压在35%时镀膜后磨损的失重量最少．而当镀膜的氮气分压和基体温度恒定时,功率在50W时镀膜后磨损的失重量最少。结论在合适的工艺条件下,用磁控溅射镀膜技术可以在牙科铸造支架Co-Cr合金表面制备耐磨性能更优的氮化锆薄膜。     

常用口腔修复材料表面细菌黏附的实验研究

目的:分析冠修复初期口腔常见菌种在修复体表面黏附和定植的数量,为临床选择合适的修复体和尽可能减少细菌在修复体表面附着和定植提供参考.方法:将烤瓷、钻铬合金逐级打磨抛光后,与釉质一起放入分别含有变形链球菌(Ua)、内氏放线菌(An)和牙龈卟啉单胞菌(Pg)的混合培养基中作厌氧培养,在6h、12h和24h 3个时间段,分别定量检测试件表面黏附的细菌数量以及液体培养基中的细菌数量,采用SPSS6.0软件包对结果进行F检验.结果:3种试件表面及液体培养基中均检测不到Pg,烤瓷组和釉质组黏附的细菌少于钴铬合金组.前6h,Ua/An在3组试件表面的附着相同;12h后,An在钻铬合金表面增加最快,烤瓷次之,釉质最慢;24h后,Ua在钴铬合金组表面最多,在烤瓷和釉质组表面的黏附情况相似,An在钴铬合金组表面增加最快,烤瓷组和釉质组的Ua/An几乎没有变化.结论:3种细菌混合培养时,段受到强烈的抑制.如要抑制Ua的附着和定植,对于钴铬合金修复体,前6h是关键期.而对于烤瓷修复体,前12h是关键期.如要抑制An的附着与定植,对于钴铬合金修复体,前24h是关键期,对于烤瓷修复体,前12h是关键期.烤瓷修复体优于钴铬合金修复体.     

C-SiO2复合薄膜对口腔钴铬合金耐腐蚀性能的影响

目的:在模拟口腔环境中,研究碳-二氧化硅(C-SiO2)复合薄膜对钴铬合金耐腐蚀性能的影响,为临床应用提供依据.方法:使用真空旋转涂布法在单晶硅片基底表面均匀旋涂C-SiO2复合薄膜,用于了解C-SiO2复合薄膜的参数.选用钴铬合金,制成20 mm×20mm×0.5 mm试件,运用真空旋转涂层布法在钴铬合金表面均匀旋涂一层C-SiO2复合薄膜.通过电感耦合等离子体发射光谱仪测量并比较涂层前、后试件浸泡液中Co、Cr、Mo的离子浓度;采用电化学工作站进行塔菲尔极化曲线测试电化学耐腐蚀性能.采用SAS8.0软件包对数据进行统计学分析.结果:电感耦合等离子体发射光谱仪测量结果显示,涂层后,试件浸泡液中Co、Cr、Mo的离子浓度显著小于钴铬合金.塔菲尔极化曲线可见钴铬合金涂层后自腐蚀电位向正方向移动,从-0.261 V上升至-0.13 V;自腐蚀电流密度呈下降趋势,从-5.0017 μA/cm2下降至-5.3006 μA/cm2.结论:C-SiO2复合薄膜(SiO2=61.71 wt％)能显著减少金属离子的释放,有效提高钴铬合金的耐腐蚀性能,具有良好的临床应用前景.     

铸造钴铬合金含银抗菌涂层对L929细胞周期及凋亡的影响

目的:检测钴铬合金含银抗菌涂层对L929细胞周期及凋亡的影响.方法:应用等离子喷涂技术制备含银抗菌涂层钴铬合金试件作为实验对象,制备浸提液用于培养L929细胞.利用流式细胞术测试细胞周期及凋亡并与常规铸造的钴铬合金试件进行比较.结果:浸提液培养48 h后,G2期细胞周期比例涂层组为(8.23±0.39)％,钴铬对照组为(8.70±0.46)％(P＞0.05);细胞早期凋亡率涂银组为(2.10±0.07)％,钴铬对照组为(2.08±0.13)％(P＞0.05).结论:涂银钴铬合金与钴铬合金比较对L929细胞周期及凋亡无显著差异,细胞相容性良好.     

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。     

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.     

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。     

5种着色氧化锆陶瓷的细胞毒性评价

目的：对掺杂5种微量着色剂的氧化锆陶瓷的生物安全性进行初步评价.方法：采用四氮唑盐比色法（MTT）细胞毒性评价方法,用5种着色氧化锆陶瓷材料的浸提液体外培养L929小鼠成纤维细胞2 d、4 d、7 d,于倒置相差显微镜下观察细胞形态;用MTT检测各实验组和对照组的吸光度值（OD值）,计算各组细胞的相对增殖率,并按照6级毒性分类法对各实验组进行评级.结果：培养期细胞贴壁生长,细胞形态正常.随着培养天数增加细胞大量增殖,各实验组的毒性评级为0-1级.结论：添加5种微量着色剂的氧化锆陶瓷无细胞毒性,具备体内应用的生物安全基础.