2种接连方式种植体的骨界面应力分析

目的建立2种包含实体种植体的下颌骨三维有限元模型,研究2种接连方式种植体（Replace和Replace Select）的骨界面应力状态。方法测量2种种植体各部件的数据和利用螺旋CT扫描下颌骨截面形态,分别建立2种种植体的三维骨内模型,对模型采用轴向加载200 N、30°侧向加载100 N载荷,分析2种种植体的骨界面的应力分布趋势。结果2种种植体骨界面应力分布特点均为从种植体颈部至根尖部逐渐减小,应力主要集中在皮质骨区和种植体颈部狭窄处的骨界面;侧向加载时骨界面的应力值均高于轴向加载。无论轴向加载还是侧向加载,ReplaceSelect种植体骨界面的应力值均高于Replace种植体。结论临床修复时应避免种植体受到过大的力,尤其是侧向力,以防出现颈部骨吸收,Replace Select种植体更应注意。     

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种植义齿的生理特殊性决定了种植义齿应有特殊的学。种植体骨界面是由力产生的微创伤和修复动态平衡来维持的。在种植义齿受到与种植体长轴方向一致的正常力时,对种植体基本没有危害。种植修复的基本建原则是:采用合理的咬合设计,使力沿种植体长轴传导,最大程度减少种植体承受的侧向力和应力。磨牙症患者可以种植,只是此类患者的种植义齿修复,要有加强固位的设计。     

种植体与天然牙联冠修复应力分布的三维有限元分析Ⅱ.水平集中载荷对种植体、天然牙骨界面应力的影响

目的 :探讨种植体与天然牙联冠在水平集中载荷作用下 ,种植体、天然牙骨界面应力分布情况及受力的相互影响 ,为临床优化设计提供生物力学的理论依据。方法 :采用三维有限元法。结果 :种植体与天然牙联冠修复时 ,种植体、天然牙骨界面颈部应力集中明显 ;种植体与稳定的天然牙联合修复时种植体 -骨界面应力分布较均匀。结论 :种植体与天然牙可共同承担载荷 ;但侧向力对种植体影响较大 ,在修复设计上应采取相应减小侧向力的措施。     

种植体长度对骨界面应力分布影响的三维有限元分析

目的：研究种植体长度对种植体骨界面应力的影响。进一步探讨种植体长度对种植体骨界面应力的影响。方法：采用三维有限元的方法对三种不同长度的种植体,在受到垂直力和侧向力时对骨界面上的应力分布进行分析。结果：垂直加载时,随着种植体长度的增加,种植体骨界面的应力值改变不明显。水平加载时,随着种植体长度的增加,种植体骨界面的应力值下降。结论：增加种植体的长度可以提高种植牙随侧向力的能力,临床上在选择种植体时,应尽量地选择较长的种植体。     

倾斜角度对种植体骨界面生物力学影响的三维有限元分析

目的 :分析不同倾斜种植对种植体界面应力、应变及位移分布状况的影响。方法 :在第一磨牙区分别垂直及向舌侧倾斜10°、20°、30°植入种植体 ,建立下颌骨三维有限元模型。模拟咀嚼肌力加载 ,分析在正中咬合情况下种植体骨界面应力、应变及位移分布情况。结果 :随着倾斜角度的增大 ,种植体骨界面应力、应变及位移均增加。倾斜30°种植时 ,种植体骨界面应力显著性增大(P<0.01)。结论 :种植体倾斜角度应小于30°。     

种植体直径对骨界面应力分布影响的三维有限元分析

目的：种植直径对种植体骨界面应力的影响,引起了许多学者的关注,国内外研究报告的观点不一。本研究是为了进一步探讨种植体直径对种植体骨界面应力的影响。方法：采用三维有限元的方法对6种不同直径的种植体在受垂直和侧向力时骨界面的应力进行分析。结果：种植体受垂直和水平加载时,随着种植体直径的增加,种植体骨界面的应力值和应和集中值下降,应力趋向均布。结论：增加种植体的直径可以提高种植牙的轴向和侧向的承受力,临床上在选择种植体时,应昼地选择粗直径的种植体。     

种植牙即刻负载与延期负载的生物力学三维有限元分析

目的比较即刻负载和延期负载对种植体骨界面生物力学分布的影响。方法采用CT扫描和自主开发的USIS软件建模,用有限元法计算分析即刻负载和延期负载时种植体骨界面的应力、应变及种植体的位移。结果即刻负载时种植体骨界面的VonMises应力稍小于延期负载,均集中于种植体颈部骨皮质,底部骨松质次之;但VonMises应变有较明显的增加,均集中于种植体底部骨松质和螺纹部位;种植体的位移较延期负载略有增大。即刻负载种植体和延期负载种植体在受到颊舌向力时,VonMises应力、应变及位移均有不同程度的增加。结论即刻负载时种植体骨界面的生物力学分布规律与延期负载时相似,受到侧向力时应力、应变增大。种植牙即刻负载技术是可行的。     

平台转换结构中肩台变化对种植体-骨界面应力分布的影响

目的:探究平台转换结构中肩台变化对种植体-骨界面应力分布的影响,以明确最优化的肩台形态,为指导临床应用及开发新产品提供理论依据.方法:采用三维有限元分析方法,建立不同肩台形态的种植体模型,对模型施以100N的轴向及侧向载荷,计算和分析肩台宽度及角度变化时种植体-骨界面的应力,并与传统两段式种植体进行比较.结果:轴向和侧向栽荷时,实验组与对照组的最大等效应力均位于种植体颈部周围的皮质骨中,松质骨中的应力较小;在同一模型上侧向载荷所产生的应力水平远大于轴向载荷所产生的应力;在平台转换结构中,肩台的变化将对种植体-骨界面应力产生较大的影响,相比对照组,肩台的角度越小、宽度越大,种植体-骨界面的应力分布就越好,应力峰值也越小,过大的肩台角度反而会造成比传统两段式种植体更大的骨界面应力;同时结果还表明随着种植体直径的增加,皮质骨界面的应力值有所下降.结论:在平台转换结构中,肩台的角度越小、宽度越大,种植体颈周皮质骨内的应力分布就越好,应力峰值也越小,随着种植体直径的增加,种植体-骨界面的应力值有所下降.从生物力学角度考虑,建议临床上尽量选择直径较大、肩台较宽、角度为0.的平台转换结构种植体.     

种植牙即刻负重的生物力学的三维有限元分析

目的 用三维有限元的方法分析牙种植体不同角度即刻负重的骨界面应力分布规律.方法 选成人无牙下颌骨进行薄层螺旋CT扫描,将扫描图像导入通用外科手术集成系统,建立下颌骨三维网格模型.模拟标准的螺纹实心种植体,建立种植体一下颌骨即刻负重的三维有限元模型.以150 N的力轴向加载和分别10.、20.、30.侧向加载,应用ANS...     

种植体-骨界面的生物力学研究进展

种植体-骨界面的生物力学反应是影响种植义齿远期成功率的重要因素之一。过大或过小的应力都会引起种植体周围的骨发生吸收或是萎缩从而导致种植失败。种植体周的应力分布受颌骨骨质、种植体形态、上部结构设计、力和材料等多方面的影响。下面就上述几方面对种植体-骨界面的生物力学特性作一综述。     

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.     

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.     

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.     

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.     

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。     

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.     

比色板标准与非标准色标识别差异的初探

目的 测试口腔修复学专业研究生对比色板标准色标与非标准色标颜色识别的差异,评价、分析口腔修复学专业研究生临床实际比色能力,为探讨临床比色教学方法提供客观的基础数据.方法 选择具有1～5年临床工作经验、排除色觉识别障碍、经过色彩学知识培训的口腔修复学专业研究生62名.从比色板A(Lineargnide)的29个标准色标中通过随机数字表抽取7个色标作为标准色标,以比色板B(Vita Bleachadgnide 3D-Master)中的7个色标作为非标准色标,在D55标准光源下,以比色板C(Vita 3D-Master)作为比色工具,对标准色标和非标准色标进行比色测试.计算受试者对两种色标比色的总体准确率;统计比色正确的人数分布,并进行Monte Carlo确切概率法检验;统计比色结果在明度、饱和度、色相上的等级偏差,并进行Wilcoxin符号秩和检验.结果 受试者对标准色标比色的总体正确率为45.9%(199/434),对非标准色标比色的总体正确率为9.0%(39/434);对两种色标比色正确的人数分布的差异有统计学意义(P<0.001);对两种色标比色结果的明度等级偏差[分别为0.2(0.1～0.3)、0.4(0.4～0.5)]、饱和度等级偏差[分别为0.2(0.1～0.4)、0.5(0.4～0.6)]的差异均有统计学意义(P<0.01),色相等级偏差[分别为0.3(0.1～0.4)、0.3(0.1～0.4)]的差异无统计学意义(P=0.079>0.01).结论 口腔修复学专业研究生对比色板非标准色标颜色的识别能力明显低于对标准色标颜色的识别能力.     

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.