牙科纳米氧化铝陶瓷粉体的制备

目的:探讨牙科纳米氧化铝陶瓷粉体的制备工艺。方法:应用溶胶-凝胶法,比较不同前驱物浓度、pH 值、热处理温度及时间等条件下所制备氧化铝粉体的物理性能。结果:Al (NO3 ) 3 ·9H2O 溶液浓度为011 molPL、pH = 9时,经1200 ℃煅烧10 min 后,可获得性能优良、粒径约为70 nm的氧化铝陶瓷粉体。结论:选择适当的反应条件可制得粒径小、团聚少的纳米氧化铝陶瓷粉体。     

三种方法预备后牙细弯根管的比较

目的探讨逐步后退法、逐步深入法、被动逐步后退法（超声波与手用器械联合应用、三种不同方法预备后牙细弯根管对根管壁的清理能力及操作时间的差别。方法应用逐步后退法、逐步深入法、被动逐步后退法（超声波与手用器械联合应用）对45个新鲜拔除的人恒磨牙近中颊侧根管进行预备．并记录操作时间，将牙根纵向劈开，分为根冠1／3、根中1／3及根尖1／3，扫描电镜下评价其根管内壁牙本质碎屑和玷污层的形成情况。结果三种方法对根管清理能力差异无统计学意义（P〉0．05）而无论使用何种预备方法，其对根中1／3及根冠1／3处的清理能力优于根尖1／3部．两者差异有统计学意义（P〈0．05）。3种方法根管预备时间分别为：逐步后退法（12．8±1．26）min．逐步深入法（9．02±0．74）min，被动逐步后退法（超声与手用器械联合应用法）（12．21±1．90）min．三组差异无统计学意义（P〉0．05）。结论三种根管预备方法均不能达到完全的根管清理，尤其是对于根尖1／3部，清洁效果很不理想：总体上看，根中及根冠1／3清洁度显著优于根尖1／3。被动逐步后退法（超声与手用器械联合应用）及逐步后退法操作均较费时、费力，而逐步后退法根管预备时间略短于另两种方法且较省力。     

不同超声冲洗液和不同时间对根管预备后清洁效果的扫描电镜观察

目的　比较不同超声冲洗液及不同超声冲洗时间对根管预备后清洁的效果。方法　80颗离体单根管上颌前牙应用机用镍钛Protaper根管预备至F3后随机分为8组,分别用不同冲洗液超声冲洗1 min和3 min,A、B组用复方氯己定含漱液,C、D组用3%H2O2溶液,E、F组用蒸馏水,G、H组用17%EDTA溶液。最后将牙体沿颊舌向纵劈,扫描电镜观察各组样本在根颈、中、尖1/3牙本质碎屑与玷污层的清除情况,根据评分统计分析比较各组根管清洁效果。结果　不同冲洗液超声冲洗1 min时,在根颈部和根中部,G组与其它各组之间比较有显著性差异（P＜0.05）。在根尖部,G组与C组差异有统计学意义（P＜0.05）,C组与A、E组比较差异有统计学意义（P＜0.05）。不同冲洗液超声冲洗3 min时,在根颈部和根中部,H组与其它各组之间比较有显著性差异（P＜0.05）。在根尖部,H组与D组比较无显著性差异（P＞0.05）,但与B、F组比较差异有统计学意义（P＜0.05）。相同冲洗液不同冲洗时间时, A、B组在根中及根尖部差异有统计学意义（P＜0.05）,C、D组在根尖部差异有统计学意义（P＜0.05）,E、F组之间和G、H组之间比较无显著性差异（P＞0.05）。结论　17%EDTA溶液超声冲洗1 min就可去除根管玷污层和碎屑。3%H2O2和复方氯己定含漱液超声冲洗1 min效果虽不及17%EDTA,但适当延长冲洗时间可增强根尖部清洁效果。     

超声波-化学沉淀法制备牙科纳米氧化铝陶瓷粉体

目的:制备分散性好,粒度均匀的纳米α-A l2O3粉体。方法:应用超声波-化学沉淀法,制备氢氧化铝前驱体,经900℃、1 000℃、1 100℃、1 200℃煅烧后测试粉体性能。结果:1 200℃煅烧得到的A l2O3粉体为α-A l2O3,其晶粒平均粒径为D202=31.44 nm。结论:以乙醇为反应溶剂,在低频超声波作用下可制备出分散性好、粒度均匀的纳米级α-A l2O3粉体。     

声波根管器械联合机用Mtwo镍钛锉在根管预备中的应用

目的 评价联合应用声波根管器械与机用Mtwo镍钛锉对磨牙进行根管预备的临床疗效。方法 选取符合纳入标准的患者100例（第一磨牙118颗,共428个根管）,按就诊顺序抽签随机分为2组,每组各50例。试验组联合应用声波根管器械与机用Mtwo镍钛锉进行根管预备,对照组采用传统不锈钢根管锉进行根管预备,2组均采用冷侧压法充填根管,观察2组根管预备时间、预备术后急症反应、根管充填质量及根充后1 a复查的治疗成功率。采用SPSS 11.0软件包进行统计学分析。结果 试验组根管预备时间平均为（5.3±0.6）min/根,对照组平均为（12.7±0.9）min/根,差异显著（t=100.89,P<0.001）;试验组根管预备术后急症反应发生率为8.20%,显著低于对照组的22.81%,差异显著（χ²=4.87,P<0.05）;试验组根管恰填率为92.86%,对照组为78.92%,差异显著（χ²=17.45,P<0.05）;根管充填后1 a的治疗成功率试验组为91.80%,对照组为78.95%,2组间差异显著（χ²=3.95,P<0.05）。结论 联合应用声波根管器械与机用Mtwo镍钛锉预备根管比传统不锈钢根管锉省时,术后疼痛反应减少,根充效果及治疗成功率提高。     

超声冲洗对感染根管内毒素的灭活及清除作用

目的探讨超声冲洗对感染根管内毒素的灭活及清除作用。方法选择因严重慢性根尖周炎拔除的具有双根管的离体上颌前磨牙10颗,常规开髓,用改良双敞法预备根管,将3％过氧化氢溶液30 μL注入根管,行超声振荡,每根管振荡2 min,分别于根管预备后和超声振荡后取样,测量内毒素活性。另外在临床患者中选择患有慢性根尖周炎的双根管上颌前磨牙10颗,采用相同的方法进行根管预备,预备后以无菌蒸馏水为介质进行超声冲洗,每根管均冲洗2 min,分别于根管预备前、根管预备后和超声冲洗2 min后根管取样,测量内毒素活性。内毒素活性的测定采用动态浊度法鲎试验,并对超声处理前后根管内毒素活性的差异进行分析。结果离体牙超声振荡前,根管内毒素的活性平均为4.069 EU·mL-1,超声振荡后为16.410 EU·mL-1,二者差异有统计学意义（P<0.01）,超声振荡后内毒素活性明显升高。临床样本中,根管预备前、根管预备后和超声冲洗后根管内毒素的平均活性分别为44.860、4.099、0.116 EU·mL-1,根管预备前与根管预备后内毒素活性的差异有统计学意义（P<0.01）,根管预备后内毒素活性明显下降;根管预备后与超声冲洗后内毒素活性的差异也有统计学意义（P<0.01）,超声冲洗后内毒素活性明显下降。结论在模拟临床操作的条件下,采用口腔科超声根管治疗仪进行超声冲洗可以明显增强根管冲洗液清除感染根管内毒素的作用,但不能增强根管冲洗液灭活感染根管内毒素的作用。     

Mtwo机用镍钛锉根管预备的临床效果观察

目的探讨Mtwo机用镍钛锉预备根管的临床效果。方法选取拟行根管治疗的患牙80颗,随机分为试验组和对照组,每组40颗,试验组采用Mtwo机用镍钛锉及改良逐步后退法进行根管预备,对照组采用手用不锈钢K锉和逐步后退法进行根管预备,2组均采用侧向加压法充填根管。比较2组的根管预备时间、根管预备术后疼痛反应和根管充填质量。结果试验组根管预备时间平均为（5.81±0.95）min/根,对照组平均为（13.45±1.08）min/根,试验组明显短于对照组,差异有统计学意义（t=17.15,P〈0.05）;试验组根管预备术后疼痛发生率明显低于对照组,且差异有统计学意义（χ2=4.45,P〈0.05）;试验组根管适充率96.6%,对照组根管适充率85.2%,2组差异有统计学意义（χ2=5.79,P〈0.05）。结论Mtwo机用镍钛锉预备根管快速有效,根管成形、根管充填效果好,并发症少,值得临床推广。     

手用Protaper镍钛根管锉在根管治疗中的应用研究

目的 了解手用镍钛根管器械ProTaper在根管治疗中的效果.方法 采用随机对照的方法比较手用ProTaper与传统不锈钢根管器械在根管预备时间、根充时间、根管充填的效果以及术后疼痛方面的差异.结果 根管预备时间分别为手用ProTaper组4.58±0.41(min)、不锈钢器械组6.66±0.43(min), 根管充填恰填率为手用ProTaper组80.96%、不锈钢器械组62.64%,术后疼痛的发生率手用ProTaper组3.66%、不锈钢器械组10.26%.结论 手用ProTaper能够保持根管初形、省时省力、术后反应少、安全,值得推广.     

机用ProTaper根管预备附加不同超声冲洗液对根管显微硬度的影响

]目的：探讨机用镍钛ProTaper根管预备附加不同超声冲洗液对根管壁牙本质显微硬度的影响。方法收集60颗离体单根管上颌前牙,随机分为6组,A组为对照组,B组应用机用镍钛ProTaper根管预备至F3,C组预备后附加3%过氧化氢溶液超声冲洗1 min,D组预备后附加口泰漱口液超声冲洗1 min,E组预备后附加17%EDTA溶液超声冲洗1 min,F组预备后附加蒸馏水超声冲洗1 min。将每个牙根平均横截为根上、根中和根尖 3 段,再纵向劈开,用显微硬度仪分别测量各组根管壁显微硬度。采用SPSS 17.0软件包对数据进行统计学分析。结果A组根管各处的显微硬度分别为（52.66±1.64）HV、（52.08±1.53）HV和（51.47±2.53）HV,差异无显著性（P>0.05）,其他各组的根尖1/3显微硬度均低于根颈和根中1/3,差异显著（P<0.05）。在根颈1/3和根中1/3,E组显微硬度分别为（44.65±1.33）HV和（42.55±1.12）HV,与其他各组相比,差异显著（P<0.05）。在根尖1/3,E组显微硬度为（37.82±1.60）HV,下降最为显著,其次为C组,显微硬度为（44.14±1.73）HV。B组、D和F组之间相比,无显著性差异（P>0.05）。结论机用镍钛ProTaper根管预备至F3可使根尖1/3显微硬度下降。17%EDTA溶液超声冲洗1 min可使根管各部显微硬度下降, 3%过氧化氢可使根尖1/3显微硬度下降,口泰漱口液和蒸馏水对根管各部牙本质显微硬度值无明显影响。     

黄芩苷降解细菌内毒素的定量分析测定

目的比较不同浓度黄芩苷降解内毒素的作用。方法采用连续倍比稀释的方法,依次选取6.250、3.125、1.562、0.781 μg/mL黄芩苷溶液,分别与1 EU/mL内毒素工作标准品混合,分别于（37±1）℃恒温水浴15、30、60 min,应用鲎实验检测反应液中内毒素含量。结果6.250 μg/mL黄芩苷对1 EU/mL的细菌内毒素的降解作用最强,15 min内完全降解。3.125、1.562 μg/mL黄芩苷分别在30 min和60 min内完全降解。在同一时间段内,4种不同浓度的黄芩苷降解内毒素的作用依次减弱。结论黄芩苷降解内毒素的作用有浓度依赖性和时间依赖性,随黄芩苷浓度升高,降解内毒素作用逐渐增强;随作用时间延长,黄芩苷降解内毒素作用增强。该结果提示黄芩苷有较好的降解细菌内毒素的作用。     

显微超声技术在钙化根管治疗中的临床研究

目的：评价根管显微镜联合超声技术在钙化根管治疗中的应用。方法：选取临床上常规方法根管预备失败的钙化根管患牙42颗,钙化根管91个,在根管显微镜下,采用超声根管锉疏通钙化根管上段,再用小号手用K锉（08#和10#）和15%EDTA疏通根管中下段,机用镍钛ProTaper完成根管预备,热牙胶完成根管充填,观察并评价疗效。结果：75个钙化根管疏通成功并完成根管充填,根管疏通率82.41%,治疗过程中有1例根管侧壁穿孔,2例出现根尖偏移,其余病例无根折、无根管台阶形成,无器械折断。结论：对于根管中上段钙化的根管,根管显微镜可提供良好的光源和清晰的术野,超声器械可有效地去除钙化组织,但对于根尖1/3的弯曲钙化根管则容易造成根管侧壁穿孔或台阶形成。     

Development of metal-resin composite restorative material. Part 3. Flexural properties and condensability of metal-resin composite using Ag-Sn irregular particles

Powder-liquid type metal-resin composites, using Ag-Sn irregular particles as the filler, 4-META as coupling agent and UDMA + TEGDMA as resin matrix, were experimentally prepared under 9 different conditions (three different particle sizes and three different filler contents). The flexural strength and flexural modulus were measured. Three different irregular particle size MRCs without redox-initiator at 94% filler content, as well as amalgam, conventional hybrid composite and Ag-Sn spherical particle MRC were evaluated for condensability. The flexural strength of the Ag-Sn irregular particle MRC was significantly influenced by both the filler particle size and filler contents (p < 0.01). It increased when either the filler content increased or the particles size decreased. The highest flexural strength (97.6 MPa) was obtained from the condition of particles size < 20 microns and 94% filler content. The flexural modulus was significantly influenced by filler content and it increased with increasing filler content. The condensability of the Ag-Sn irregular particle MRC was lower than that of amalgam but much higher than presently available conventional composites and spherical particle MRC.     

Dimethacrylate based on cycloaliphatic epoxide for dental composite.

OBJECTIVES: The aim of this study was to investigate the kinetics and mechanical properties of dimethacrylate monomer based on cycloaliphatic epoxide for dental restorative composite. METHODS: Dimethacrylate based on cycloaliphatic epoxide (EPCDMA) was copolymeirzed with TEGDMA by varying the curing conditions: monomer composition and light intensity. A real-time near FTIR technique was employed to monitor the double bond conversion and the rate of polymerization. Dynamic mechanical analysis was performed on a dynamic mechanical analyzer, and volume shrinkage of the cured samples was determined by pycnometric method. RESULTS: The results of kinetics showed that, two peaks of maximum rate of polymerization (Rpmax) occurred when the amount of TEGDMA was more than 30wt%. Increasing the amount of TEGDMA, the final double bond conversion and polymerization shrinkage both increased, while the glass transition temperature (Tg) decreased. All EPCDMA/TEGDMA mixtures had slightly higher storage modulus at body temperature (37 degrees C). When compared with Bis-GMA/TEGDMA (70/30), the EPCDMA/TEGDMA (70/30) system assumed similar reactivity and volume shrinkage but higher Tg. SIGNIFICANCE: EPCDMA had comparable mechanical properties to those of Bis-GMA.     

Elution parameters and HPLC-detection of single components from resin composite

The toxic effects of mercury derived from amalgam fillings have been a focus of controversy in Germany during the last 25 years. As alternatives to amalgam, composites are used widely to restore anterior and posterior permanent teeth. This study quantifies the amount of TEGDMA and methacrylic acid that can be derived from a polymerized commercial hybrid composite material. Different specimens were made with different curing methods with and without an oxygen inhibition layer. To simulate the removal of composite fillings, some samples were pulverized. The specimens were eluted in distilled water at 37^°C for different time intervals. To check the influence of acid conditions, pulverized material was incubated in 6 M HCl. The separation of the eluted chemical resin components was done by HPLC. A defined mixture of pure components was used as an external standard for the identification and quantification of the eluted components. The results focus on the release of triethylenglycoldimethacrylate (TEGDMA) and methacrylic acid. Concerning the different incubation methods, the results showed higher TEGDMA elution with oxygen inhibited surface layer and with the pulverized samples. Within acid conditions, the amount of TEGDMA found was low, but the amount of methacrylic acid increased. Small resin monomers like TEGDMA are primarily eluted from composite in aqueous solutions. Within acid conditions a hydrolytic disintegration of the ester bonding of the monomers could be observed. Methacrylic acid – a substance with allergenic potential – could be detected. Received: 27 May 1999 / Accepted: 23 August 1999     

不同烧结温度对钛实验粘结瓷的力学性能的影响

目的：探讨烧结温度对钛实验粘结瓷的烧结性能和力学性能的影响,以确定较为成熟的制备工艺。方法：钛实验粘结瓷粉在100MPa冷等静压成型,分别在750℃、800℃、850℃烧结,对比测定钛实验粘结瓷体的体积密度、表观气孔率、真密度、总气孔率、三点弯曲强度、断裂韧性和维氏硬度。结果：钛试验粘结瓷的抗弯强度、维氏硬度在800℃时达到最大;断裂韧性在850℃时最高。800℃时钛试验粘结瓷的真密度和表观密度均达到最大,表观气孔率和总气孔率在800℃时降至最小。结论：综合各种因素,800℃为钛实验粘结瓷粉最佳烧结温度。     

Er：YAG激光预备及酸蚀处理对复合树脂充填体微渗漏的影响

目的 研究Er∶YAG激光备洞及酸蚀处理对复合树脂充填体微渗漏的影响.方法 将40颗离体前磨牙随机平均分为5组制备洞型：A组,高速牙钻预备加酸蚀;B组,Er∶YAG激光预备;C组,Er∶YAG激光预备加酸蚀;D组,高速牙钻预备加Er∶YAG激光蚀刻;E组,高速牙钻预备加Er∶YAG激光蚀刻后酸蚀.所有样本经复合树脂充填后交替放置于5℃与55℃水中各1 min,间隔45 s,共2000个周期进行冷热循环,然后用0.2％亚甲基蓝染色后颊舌向劈开,体视显微镜下观察剖面,记录其微渗漏情况,并进行统计学分析.另选6颗离体前磨牙,随机分为3组,按上述A、B、C三组方法制备,扫描电镜下观察其牙本质界面的结构.结果 在（牙合）壁与龈壁,B组染料渗入严重,到达洞底,微渗漏最大,与其他各组相比有统计学差异（P＜0.05）,A、C、D、E组染料渗入表浅,微渗漏程度之间没有统计学差异（P＞0.05）.扫描电镜下,A组牙本质表面较平整,无玷污层存在,牙本质小管口开放.B组牙本质表面不平整如鳞片状,无玷污层,牙本质小管口开放,直径小于酸蚀组.C组牙本质小管口开放,无玷污层存在,管周牙本质脱矿明显.结论 单纯Er∶YAG激光预备比传统牙钻制备结合酸蚀处理洞型更易发生微渗漏,若Er∶YAG激光预备结合酸蚀剂处理可以使微渗漏程度减小,Er∶YAG激光蚀刻可以达到和酸蚀剂类似的效果.     

Synthesis and study of properties of dental resin composites with different nanosilica particles size

Objectives

The aim of this work was the synthesis of light-cured resin nanocomposites using nanosilica particles with different particle size and the study of some physical-mechanical properties of the composites.

Methods

Various types of silica nanoparticles (Aerosil) with average particle size of 40, 20, 16, 14, and 7 nm, used as filler were silanized with the silane 3-methacryloxypropyl-trimethoxysilane (MPS). The total amount of silane used was kept constant at 10 wt% relative to the filler weight to ensure the complete silanization of nanoparticles. The silanizated silica nanoparticles were identified by FT-IR spectroscopy and thermogravimetric analysis (TGA). Then the silanized nanoparticles (55 wt%) were mixed with a photoactivated Bis-GMA/TEGDMA (50/50 wt/wt) matrix. Degree of conversion of composites was determined by FT-IR analysis. The static flexural strength and flexural modulus were measured using a three-point bending set up. The dynamic thermomechanical properties were determined by dynamic mechanical analyzer (DMA). Sorption, solubility and volumetric change were determined after storage of composites in water or ethanol/water solution 75 vol% for 30 days. The TGA for composites was performed in nitrogen atmosphere from 30 to 700 °C.

Results

As the average silica particle size decreases, the percentage amount of MPS attached on the silica surface increases. However, the number of MPS molecules attached on the silica surface area of 1 nm² is independent of filler particle size. As the average filler particles size decreases a progressive increase in the degree of conversion of composites and an increase in the amount of sorbed water is observed.

Significance

The prepared composites containing different amount of silica filler, with different particle size, but with the same amount of silanized silica and organic matrix showed similar flexural strength and flexural modulus, except composite with the lowest filler particle size, which showed lower flexural modulus.     

The effect of cure rate on the mechanical properties of dental resins

OBJECTIVE: This study investigates the effect of cure rate on the mechanical properties of a common dimethacrylate dental resin formulation (75/25 wt% bis-GMA/TEGDMA). METHODS: The polymerization rate and final conversion of the exact specimens subsequently used for mechanical testing were monitored by near-infrared (near-IR) spectroscopy. The glass transition temperature (T(g)) and modulus, as a function of temperature, were determined by dynamic mechanical analysis (DMA). Iniferter initiating systems were used to create partially cured networks that did not contain any trapped radicals. By the elimination of trapped radicals from the system, the formed networks can be characterized as a function of both temperature and double bond conversion without inducing additional thermal cure during testing. RESULTS: Copolymer specimens were cured with UV and visible light initiating systems, UV light intensities that varied by over four orders of magnitude, and cure temperatures that differed by 60 degrees C. Even though the polymerization rates for these resins were vastly different, similar T(g) and modulus were measured for specimens cured to the same final double bond conversion. SIGNIFICANCE: This study shows that highly cross-linked dimethacrylate systems, such as bis-GMA/TEGDMA, exhibit similar network structure and properties as a function of double bond conversion, regardless of the method or rate of cure.     

Synthesis and characterization of triethylene glycol dimethacrylate nanocapsules used in a self-healing bonding resin

Objectives

To date, the production of highly durable dentine bonding is still a challenge. Self-healing bonding resins may provide a new direction for the improvement of the bonding durability. The objective of the current study was to synthesize polyurethane nanocapsules encapsulated with the core material triethylene glycol dimethacrylate (TEGDMA) for use as a major component in a self-healing bonding resin.

Methods

TEGDMA nanocapsules were synthesized via interfacial polycondensation in a miniemulsion, and the TEGDMA nanocapsules were then characterized via Fourier-transform infrared (FTIR) spectrometer, field emission scanning electron microscopy (FESEM), and high-performance liquid chromatography (HPLC) to investigate the morphology, the average TEGDMA loading (DL%), and encapsulation efficiency (EE%). The mechanical property of dental adhesive with different concentrations (0, 3, 6, 9, and 12 wt%) of the TEGDMA nanocapsules were also measured, and the cytotoxicity was investigated using an MTT assay.

Results

FTIR confirmed that the TEGDMA nanocapsules were successfully synthesized. These nanocapsules showed a high drug load. The bond strength of the dental adhesive incorporated with 9 wt% TEGDMA nanocapsules was significantly higher compared with those of the other groups (P < 0.001). Moreover, the biocompatibility of the dental adhesive was not affected by the incorporation of the TEGDMA nanocapsules.

Conclusions

The current study demonstrated the successful synthesis of TEGDMA nanocapsules, and the overall properties of the dental adhesive were not compromised.     

The effect of comonomer composition, silane heating, and filler type on aqueous TEGDMA leachability in model resin composites

Experimental composites using either bisGMA/TEGDMA or UEDMA/ TEGDMA matrices, quartz or barium glass fillers, and 2 different filler silanization methods were evaluated regarding monomer leachability in distilled water. The leached amount was detected and quantified using gas chromatography. The results showed that twice as much TEGDMA is leached from a bisGMA/TEGDMA based composite than from an UEDMA/ TEGDMA based composite, when both contain 50 wt% TEGDMA. The hypothesis suggested that the higher degree of cure of UEDMA/TEGDMA based composites would be reflected in a lower monomer leaching value, and this hypothesis was supported by the findings. Whether such a correlation exists within groups of UEDMA/TEGDMA based matrices having different degrees of cure was not determined and needs to be investigated in future studies. Variables such as filler composition and silane treatment did not affect the leaching values of TEGDMA in water. That finding suggests that future studies should target differences in matrices, and that the need for considering effects of filler composition and silane treatment methods should not receive the same priority.