牙科用云母微晶玻璃的微观结构对其力学性能的影响

目的：研究牙科CAD／CAM加工用四硅氟云母微晶玻璃的微观结构对其力学性能的影响，方法：采用K2O－MgO-MgF2-SiO2系统来研制云母微晶玻璃，通过差热分析（DTA），X射线衍射分析（XRD），扫描电子显微镜观测（SEM）及力学性能测试，比较了三种不同晶化温度下，四硅氟云母微晶玻璃的微观结构对其力学性能影响，结果：随着晶化温度的逐步升高，四硅氟云母的晶粒大小和径厚比逐步增大，抗弯强度和断裂韧性亦逐渐增高，维氏硬度和脆性指数随温度升高而降低。结论：云母微晶玻璃的微观结构对其力学性能起决定作用，而微观结构与晶化温度密度相关。     

牙科用云母微晶玻璃的微观结构对其力学性能的影响

目的 :研究牙科CAD/CAM加工用四硅氟云母微晶玻璃的微观结构对其力学性能的影响。方法 :采用K2 O -MgO -MgF2 -SiO2 系统来研制云母微晶玻璃 ,通过差热分析 (DTA)、X射线衍射分析 (XRD)、扫描电子显微镜观测 (SEM )及力学性能测试 ,比较了三种不同晶化温度下 ,四硅氟云母微晶玻璃的微观结构对其力学性能影响。结果 :随着晶化温度的逐步升高 ,四硅氟云母的晶粒大小和径厚比逐步增大 ,抗弯强度和断裂韧性亦逐渐增高 ,维氏硬度和脆性指数随温度升高而降低。结论 :云母微晶玻璃的微观结构对其力学性能起决定作用 ,而微观结构与晶化温度密切相关     

熔融铸造法及烧结法氟云母玻璃陶瓷性能的比较

目的:研究不同制备工艺对齿科可切削氟云母玻璃陶瓷性能的影响.方法:采用熔融铸造工艺和烧结工艺制备K2O-MgO-MgF2-SiO2系统可切削氟云母玻璃陶瓷,采用XRD、SEM确定其晶相组成和微观结构,测试透射率、弯曲强度和脆性指数.结果: 2 种制备工艺制备的玻璃陶瓷主晶相均为四硅氟云母,晶相大小均为2～5 μm,径厚比6～7.烧结制备玻璃陶瓷晶相体积分数较高,透射率、脆性指数较低,弯曲强度较高.结论:针对氟云母玻璃陶瓷而言,烧结法制备工艺优于熔融铸造工艺.     

烧结温度对不同粒度氟硅云母玻璃陶瓷收缩率及微观形貌的影响

目的:探讨烧结温度对 2种颗粒粒度氟硅云母微晶玻璃烧结收缩率及微观形貌的影响。方法:选用颗粒平均粒度分别为 4. 5μm和 72. 8μm的氟硅云母玻璃粉,经冷等静压成型,分别在 600~1 000℃之间不同温度烧结,比较 2种颗粒尺寸微晶玻璃的收缩率变化及微观形貌的差别。结果:随着烧结温度的增加, 2种粒度玻璃烧结收缩率均增加,但二者收缩率曲线差别明显,粒度较小者收缩率高于粒度较大者,而且体现烧结机制变化的温度转折点亦有显著差别,其微观形貌表现出相同的变化趋势。结论:小粒度氟硅云母玻璃粉体获得的烧结致密度优于大粒度粉体;采用小粒度玻璃粉体中温段加强烧结工艺,可以获得良好的烧结致密度。     

牙科可切削云母微晶玻璃呈色的研究

目的 研制用于牙科计算机辅助设计与辅助制作磨牙冠、可提供多种颜色选择的可切削四硅酸氟云母微晶玻璃。方法 采用正交设计技术，对影响微晶玻璃颜色的基础配方、色料组成及热处理制度进行筛选。结果 从基础配方中选择出影响呈色的2个主要因素：晶核剂F含量、Mg^2 ／K^ 比例；从多种色料中选择出主要色料CeO2；从热处理制度中选择出成核制度：650℃保持1h和晶化制度：1000℃或1050℃保持3h～4h,，结论 所研制的云母微晶玻璃，可提供4～5种牙科颜色，其切削性能良好，完全可以满足计算机辅助设计．辅助制作(CAD／CAM)系统的要求。     

牙科用可切削云母基玻璃陶瓷析晶行为研究

目的:采用阶梯烧结法制备K2O-MgO-Al2O3-SiO2-F系列玻璃陶瓷,分析不同热处理工艺对所制玻璃陶瓷性能的影响。方法:通过X射线衍射(XRD)、扫描电子显微镜(SEM)、背散射(BSE)及抗弯强度测试,研究氟硅云母玻璃陶瓷的析晶行为特点。结果:680℃核化1 h后,若在1 000~1 120℃之间晶化,则析出主晶相为四氟硅云母,晶体形状由颗粒状逐渐变成立方状或扁平状。陶瓷在大于1 160℃晶化出现晶体熔化。结论:680℃核化1 h后,1 040℃析出的云母晶体符合材料的微观要求,过高的温度不利于云母晶体的析出;二次融入3%的四方氧化锆多晶体(Y-TZP)完全熔解于K2O-MgO-Al2O3-SiO2-F玻璃系统中。     

纳米二氧化硅对氟硅云母玻璃陶瓷强度的影响

目的:提高以云母为主晶相的牙科用可切削玻璃陶瓷氟硅云母玻璃陶瓷材料强度.方法:在氟硅云母玻璃原料粉中使用纳米二氧化硅(粒径7nm),制备氟硅云母玻璃陶瓷,用扫描电镜观察其显微结构,X线衍射确定物象组成及含量,测定样本的抗弯强度和断裂韧性,并与普通氟硅云母玻璃陶瓷材料进行比较.结果:使用纳米二氧化硅(纳米组)和普通氟硅云...     

晶化热处理对牙用玻璃陶瓷力学性能的影响

目的：探讨晶化热处理对牙用玻璃陶瓷力学性能的影响。方法：按不同晶化温度条件分组,利用Ｘ线衍射技术鉴定晶相,计算晶体含量,并采用三点弯曲法测定各组的抗弯强度和弹性模型,结果该材料主晶相为四硅酸氟云母晶体（ＫＭｇ２．５Ｓｉ４Ｏ１０Ｆ２）,玻璃晶化后力学性能大大提高（Ｐ〈０．０５）。在８３０℃－９５０℃的晶化温度范围内,随晶化温度升高,结晶率和力学参数均不断增大,力学性能与结晶率存在相关关系。结论晶化热处理能直接影响玻璃陶瓷的显微结构及其力学性能的发挥。     

二次熔融烧结法制备牙科用可切削云母基玻璃陶瓷

目的:通过二次熔融烧结法制备以云母为主晶相的牙科用可切削玻璃陶瓷。方法:在1500℃下熔融K2O-MgO-Al2O3-SiO2-F系统基础玻璃,其玻璃粉经过冷等静压成型后无压烧结获得牙科用可切削玻璃陶瓷。采用DTA-TGA确定基础玻璃的核化和晶化温度,采用XRD和SEM分析烧结体的物相组成和微观形貌,以及采用三点弯曲法和压痕法测定烧结体的力学性能。结果:K2O-MgO-Al2O3-SiO2-F系统的核化温度和晶化温度分别选择680℃和1020℃。烧结体的整体析晶比较缓慢,结晶度约为35.48%,主晶相为氟硅云母,晶体呈立方或扁平状,交错排列。烧结体的弯曲强度和断裂韧性分别为(144.50±9.75)MPa和(1.25±0.26)MPa.m1/2。结论:二次熔融烧结法制备的云母基玻璃陶瓷能够满足临床牙体缺损修复的要求。     

预烧结温度及升温速率对氧化铝玻璃复合体性能的影响

目的探讨预烧结温度及升温速率对氧化铝玻璃复合体性能的影响.方法微米α-氧化铝粉经250MPa冷等静压成型,分别经高速率升温至1400℃、1450℃及低速率升温至1400℃、1450℃烧结,制备成的预烧结氧化铝块再通过1250℃ 4h的镧硼硅玻璃渗透,获得氧化铝玻璃复合体,测试不同烧结条件下氧化铝玻璃复合体的各种物理及力学性能,并观察它们的微观结构差异.结果高速率升温至1400℃、1450℃以及低速率升温至1450℃烧结的氧化铝较低速率升温至1400℃烧结的氧化铝制备的复合体的抗弯强度和断裂韧性有明湿增加,抗弯强度值分别为380±32.67MPa,420±25.79 MPa,411±27.73 MPa,337±23.46 MPa.低速率升温至1400℃的氧化铝玻璃复合体以沿晶断裂为主,而高速率升温至1400℃、1450℃及低速率升温至1450℃的氧化铝玻璃复合体断口,沿晶断裂和穿晶断裂同时存在.结论复合材料最佳的力学性能、基体材料的可切削性能以及工艺等方面,以高速率升温至1450℃的预烧结氧化铝基体最为理想.     

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.     

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.     

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。     

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。     

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。     

《口腔医学》杂志2007年度有关信息的分析

目的通过对《口腔医学》2007年全年文献的回顾和分析,了解我国口腔临床医学的研究现状。方法阅读2007年《口腔医学》全年的文献,对各种信息进行了分类汇总,根据设计类型对临床一次性文献进行了分类,并对其中的试验性研究文章进行质量分析。结果《口腔医学》2007年全年的一次性文献274篇,基础和临床文献分别为108和166篇,以临床文献为主(60.58%)。在临床研究文献中,属于观察性、分析性和试验性的文献分别为97、9和60篇,观察性文献所占比例为36.14%,高于以往的报道。60篇观察性文献中,全都设有对照;统计方法应用得当者44篇;真正做到随机、盲法的分别只有4和2篇。结论我国口腔临床方面的研究水平近年来提高明显,但设计的科学性方面有待提高。     

鼻测量法的进展

唇裂术后继发畸形是指唇裂修复术后,仍遗留或继发于手术操作和生长发育变化而表现出来的一类畸形[1]。包括唇畸形、鼻畸形和颌骨畸形。其修复较原发性唇裂修复更复杂,更灵活多变。而导致其修复复杂性的一个重要原因即是局部组织结构复杂变异和缺乏可靠的三维测量手段[2],鼻畸形