白念珠菌生物被膜耐药株麦角甾醇检测的方法学研究

目的：分别采用高效液相色谱法和气相色谱质谱联用法测定白念珠菌麦角甾醇含量,并对这两种方法进行比较。方法：采用浓度梯度递增法诱导白念珠菌耐药株,采用KONT真菌显色MIC药敏系统鉴定耐药性。构建6、12、24h生物被膜,采用高效液相色谱法和气相色谱质谱联用法测定麦角甾醇含量。结果：高效液相色谱法检测出麦角甾醇含量,最低检出浓度为0.05mg/L,而气相色谱质谱联用法未检测出麦角甾醇含量。结论：高效液相色谱法能准确测定白念珠菌麦角甾醇含量。与气相色谱质谱联用法比较,高效液相色谱法简单、高效和可靠。     

新型电热聚合法对义齿基托残余单体含量的影响

目的研究一种新型电热聚合法对义齿基托残余单体含量的影响,并与传统水浴法在用水耗电上做比较。方法选择两种常用热凝义齿基托树脂材料,分别采用传统水浴法和电热聚合法制作样本,测量每次聚合过程中所需的用水量和耗电量。用气相色谱仪进行各样本残余甲基丙烯酸单体(MMA)的检测和比较。结果各样本残余MMA含量都满足国家医药行业YY0270-2003标准要求,传统水浴法的残余MMA含量略低,差别有统计学意义(P<0.05)。传统水浴法制作义齿每次每型盒用水1.25L,耗电(0.53±0.02)kwh,电热聚合法不需用水,耗电(0.09±0.02)kwh,差别有统计学意义。结论电热聚合法所制作样本残余MMA含量符合相关标准,是一种高效、节能的义齿基托聚合方法。     

Bis-GMA/TEGDMA树脂水解产物分析

目的检测Bis-GMA/TEGDMA树脂片经去离子水浸泡后的水解产物。方法 Bis-GMA/TEGDMA单体加入CQ/DMAEMA后光照聚合制备树脂片,将树脂片经37℃恒温去离子水浸泡24 h,其中在1h、3 h、6 h和24 h四个时间点各取1 mL浸泡液,用乙酸乙酯萃取、旋蒸,通过高效液相色谱质谱法(HPLC/MS)检测分析,确定树脂水解产物。结果树脂片的水解产物为双酚A-二甘油醚(Bis-GMA-2MA)、双酚A-二氧代丙基醚(Bis-GMA-2MA-2H2O)、单甲基丙烯酸二缩三乙二醇酯(TEGDMA-MA)和二缩三乙二醇(TEGDMA-2MA)。结论 Bis-GMA/TEGDMA树脂片经去离子水浸泡后树脂可发生水解,水解产物及残余Bis-GMA/TEGDMA树脂单体可析出并释放到去离子水中。     

牙本质粘结体系中单体水解和析出的机制及其影响因素

牙本质粘结剂的固化反应本质上是树脂单体发生聚合、交联反应形成聚合体的过程,单体的双键转化率反映了其聚合程度。一方面,树脂单体和聚合体内含有众多共价化学键,在口腔唾液、酶的催化作用下易发生水解断裂;另一方面,由于目前技术条件限制,单体无法达到理想的完全聚合,这些残余单体及其水解产物释放进入口腔环境,不仅对口腔局部和全身系统具有一定的潜在危害性,而且还对牙本质粘结的耐久性带来不利影响。单体的析出和水解受单体自身结构以及聚合反应条件、牙本质粘结界面因素、口腔环境等多重因素影响。本文就牙本质粘结体系中单体水解、析出机制及其影响因素作一综述。     

聚合方式对义齿基托树脂中残余甲基丙烯酸甲酯单体含量的影响

目的研究聚合方式对义齿基托树脂中残余甲基丙烯酸甲酯含量的影响。方法按照不同的聚合方式,将实验分为3组,每组制备3块试验样块.按照YY0270-2003规定的气相色谱法实验方法测试各组样品的甲基丙烯酸甲酯单体（MMA）含量。结果不同聚合方式得到的材料中MMA的百分含量明显不同,以微波聚合方式得到的基托材料残余单体含量最低。结论聚合方式对义齿基托材料残余单体含量具有显著影响。     

树脂基托浸出物及降低其浸出量的方法

在树脂聚合反应中,单体甲基丙烯酸甲酯转换并不完全,基托内仍有残余甲基丙烯酸甲酯存在。在浸泡基托的液体中,可检测到甲基丙烯酸、甲醛、苯甲酸、邻苯二甲酸、苯甲酸苯酯、双环己基邻苯二甲酸酯、酞酸丁二酯、水杨酸苯酯和过氧化苯甲酰等成分。甲基丙烯酸甲酯及其派生物不但对牙龈成纤维细胞、牙髓细胞和牙周膜细胞等原代细胞的细胞膜完整性和细胞功能有一定影响,还影响谷胱甘肽、细胞因子和生长因子的表达。甲基丙烯酸甲酯单体的聚合程度直接影响材料的表面硬度、光洁度、拉伸强度、挠曲强度、抗疲劳度以及耐磨性、尺寸和颜色稳定性,加速唾液中某些酶对聚合物的降解和细菌在基托表面的滋生。提高聚合物粉液比,水浸泡,适当延长聚合周期或升高加热温度,聚合树脂热处理,添加聚乙烯纤维,添加交联剂,表面抛光,紫外线活化的涂层材料,适宜的活化剂质量浓度,可降低残余甲基丙烯酸甲酯水平。     

快速自控热处理塑料残余单体的测试

快速自控热处理塑料残余单体的测试夏春明张素芳王军力本研究应用凝胶渗透色谱分析技术，测试了快速聚合基托塑料的残余单体含量及聚合物分子量分布的情况，与常规聚合方法进行了比较。１．材料与方法：（１）仪器：凝胶渗透色谱分析仪为ＧＰＣ－Ⅰ型，美国产。材料与试件...     

Shotgun法鉴定牙龈卟啉单胞菌Pg301外膜蛋白

目的采用Shotgun法对牙龈卟啉单胞菌Pg301外膜蛋白进行分析,为筛选牙周炎疫苗候选抗原奠定基础。方法培养Pg301,提取外膜蛋白,十二烷基硫酸钠-聚丙烯酰胺凝胶电泳分离蛋白,胶内酶解成多肽混合物,经高效液相色谱-串联质谱分析,结合美国国立生物技术信息中心蛋白质数据库进行蛋白鉴定,获得外膜蛋白成分。结果分析出586个唯一肽段,鉴定出93种蛋白,其中有50种是已确定的蛋白。结论 Shotgun法能够快速高效分析细菌外膜蛋白,为筛选保护性抗原、毒力相关候选蛋白等奠定基础。     

影响复合树脂聚合收缩应力的因素

随着人们对美观要求的日益提高和复合树脂性能的不断完善,复合树脂在口腔临床中的应用已变得日益广泛.目前对复合树脂性能上的改善主要集中在提高其机械性能,减少残余游离单体的释放以增强其生物安全性,减少聚合收缩的程度以防止微渗漏的形成和牙体变形等方面.而树脂发生聚合反应是其自身物理和化学特性所决定的,其收缩产生的应力对复合树脂性能有着重要影响.近年来,对影响树脂聚合收缩应力的因素已成为复合树脂研究的热点,本文就影响树脂聚合收缩应力的因素做一简要综述.     

填料含量对牙科光固化粘结剂残余单体量的影响

目的：探讨填料的加入对牙科光固化粘结剂聚合转化度的影响。方法：采用高效液相色谱仪测试了不同填料含量的光固化粘结剂固化后的残余单体量。结果：无填料粘接剂残余单体量最大，随填料含量增加而减少；照射６０ｓ，９．１％组显示最小。结论：填料含量５％（ｗｔ），照射６０ｓ较适宜     

Analysis of residual monomers in dendritic methacrylate copolymers and composites by HPLC and headspace-GC/MS.

OBJECTIVES: The aim of this study was to analyze the residual monomer content of photopolymerized dendritic methacrylate copolymers and particulate filler composites. Headspace-gas chromatography/mass spectrometry (HS-GC/MS) was compared with high performance liquid chromatography (HPLC). METHODS: The resin mixtures consisted of a dendritic methacrylate monomer, methyl methacrylate and acetoacetoxyethyl methacrylate in varied proportions. In addition, one of the composites contained 1,4-butanediol dimethacrylate. Camphorquinone and 2-(N,N-dimethylamino)ethyl methacrylate were used as the light-activated initiator system. The content of residual methyl methacrylate and acetoacetoxyethyl methacrylate after 40 s photopolymerization were analyzed with HPLC and HS-GC/MS. RESULTS: The content of residual methyl methacrylate decreased and residual acetoacetoxyethyl methacrylate increased with increasing concentration of acetoacetoxyethyl methacrylate in the resin mixture. The results with both methods had the same trend. SIGNIFICANCE: The addition of acetoacetoxyethyl methacrylate enhanced the copolymerization of methyl methacrylate, but did not decrease the total residual monomer content. The HS-GC/MS method was found to be a feasible method in the analysis of low-boiling residuals in dental polymers.     

Elution of monomers from two conventional dental composite materials

OBJECTIVE: The aim of this study was to determine the elution of monomers of two conventional resin composite materials after different polymerization and storage times. METHODS: Two resin composites (a hybrid and a flowable) were used. Four groups (n=10, diameter: 4.5mm, thickness: 2mm) of each material were fabricated, one for each polymerization time of: 0s, 20s, 40s, and 80s. The samples were stored in 1ml of 75% ethanol at room temperature, and the storage medium was renewed after 24h, 7 days, and 28 days. From the storage medium that was removed, samples were prepared and evaluated, with LC-MS/MS. RESULTS: Bisphenol A and UDMA were not detected in the samples. Regardless of the polymerization time, the material or the storage time, a higher amount of BisGMA was eluted compared to TEGDMA. The amount of monomer that was released from the polymerized samples of the hybrid resin composite (Tetric Ceram) was significantly higher (p<0.0001) compared to the flowable (Tetric Flow). No significant difference was found between samples polymerized for 20s compared to 40s concerning the elution of monomers. Only a polymerization time of 80s resulted in a decreased release of monomers. The release of TEGDMA decreased after 28 days; however, the elution of BisGMA remained at high levels. SIGNIFICANCE: The release of monomers remains at a high level for a long time (7-28 days) after polymerization. The 40s that are usually used for the polymerization of resin composites seems insufficient in order to prevent a high release of monomers.     

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     

Leachability of plasticizer and residual monomer from commercial temporary restorative resins

OBJECTIVES: This study was performed to determine the compositions of commercial temporary restorative resins and to evaluate the leachability of plasticizer and residual monomer from them. METHODS: The chemicals in four commercial temporary restorative resins (Dura Seal, Fit Seal, Plast Seal Quick, and Poly Seal) were detected by GCMS and HPLC. The amounts of plasticizers and residual monomers that leached from cured resin samples immersed in ethanol for 1 h to 14 d were determined by HPLC. RESULTS: Phthalate esters used as plasticizers contained 40-55 wt% either di-n-butyl phthalate (DBP) or butyl phthalyl butyl glycolate. The resin monomer included methyl methacrylate (MMA) or a mixture of MMA and 2-hydroxyethyl methacrylate (HEMA); 1,3-butanediol dimethacrylate was added as a cross-linking agent. Each resin contained 40-60 wt% monomer. The amounts of phthalate esters leached increased with immersion time up to 7 d, reaching 120-190 microg/mg, and did not change subsequently. The residual monomers leached gradually for up to 3d and did not change subsequently. The amount of leached residual monomer (MMA, HEMA) was 20-90 microg/mg after 3d storage. More than 50% of the leachable plasticizers and monomers were eluted from the cured resins within 24 and 3 h, respectively. CONCLUSIONS: The amounts of leached plasticizers and residual monomers were extremely large compared with the concentrations of endocrine disrupters and their potentially genotoxic effects. Therefore, it is very important to evaluate the leachability of these compounds from temporary restorative resins.     

Biological and physicochemical properties of carbon-graphite fibre-reinforced polymers intended for implant suprastructures

The aim of this study was to determine water sorption, water solubility, dimensional change caused by water storage, residual monomers, and possible cytotoxic effects of heat-polymerized carbon-graphite fibre-reinforced composites with different fibre loadings based on methyl methacrylate/poly(methyl methacrylate) (MMA/PMMA) and the copolymer poly (vinyl chloride-co-vinyl acetate). Two different resin systems were used. Resin A contained ethylene glycol dimethacrylate (EGDMA) and 1,4-butanediol dimethacrylate (1,4-BDMA); the cross-linker in Resin B was diethylene glycol dimethacrylate (DEGDMA). The resin mixtures were reinforced with 24, 36 and 47 wt% surface-treated carbon-graphite fibres. In addition, polymer B was reinforced with 58 wt% fibres. Water sorption was equal to or below 3.34±1.18 wt%, except for the 58 wt% fibre loading of polymer B (5.27±1.22 wt%). Water solubility was below 0.36±0.015 wt%, except for polymer B with 47 and 58 wt% fibres. For all composites, the volumetric increase was below 0.01±0.005 vol%. Residual MMA monomer was equal to or below 0.68±0.05 wt% for the fibre composites. The filter diffusion test and the (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) (MTT) assay demonstrated no cytotoxicity for the carbon-graphite fibre-reinforced composites, and residual cross-linking agents and vinyl chloride were not detectable by high-performance liquid chromatography (HPLC) analysis.     

Resin composites in dentistry: the monomer systems

The present review outlines the history of monomers, used in resin composites, motivates further development, and highlights recent and ongoing research reported in the field of dental monomer systems. The monomer systems of most present-day resin composites are based on BisGMA, developed some 40 years ago, or derivatives of BisGMA. In the remaining resin composites, urethane monomers or oligorners are used as the basis of the monomer system. The main deficiencies of current resin composites are polymerization shrinkage and insufficient wear resistance under high masticatory forces. Both factors are highly influenced by the mooonier system, and considerable efforts are being made around the world to reduce or eliminate these undesirable properties. The use of fluoride-releasing monomer systems, some of which are under investigation, has been suggested to mitigate the negative effects of marginal gaps formed in consequence of polymerization shrinkage. The very crux of the problem has also been approached with the synthesis of potentially low-shrinking/non-shrinking resin composites involving ring opening or cyclopolymerizable monomers. By the use of additives with a supposed chain transfer agent function, monomer systems have been formulated that improve the degree of conversion of methacrylate double bonds and mechanical properties. Many promising monomer systems have been devised, the implementation of which may be expected to improve the longevity of resin composite fillings and expand the indications for resin composites.     

Analysis of eluate extracted from dental filling resin by high performance liquid chromatography (author's transl)]

Since the residual monomer of cured filling resin has been implicated in toxicological effects, a high performance liquid chromatography (HPLC) was used to analyze the eluate of bisphenol A diglycidylmethacrylate (Bis-GMA) and methyl methacrylate (MMA) type resins presently used. The main chemicals of the eluate from resin into three kinds of solution, water, 85% methanol water solution and 100% methanol were the residual monomers which formely were Bis-GMA, triethylenglycol dimethacrylate and latterly MMA. Residual initiators, benzoyl peroxide and hydroquinone were also determined. This investigation has shown that HPLC is rapid, reliable and an acurate method to analyze the residual monomers of cured dental filling resins.     

Antibacterial properties of resin composites and dentin bonding systems.

This paper reviews the research conducted on the evaluation of antibacterial properties of commercial composites and adhesive systems, in addition to the discussion on many attempts to achieve antibacterial composites or adhesives. With regard to composites, commercially available products including fluoride-releasing materials have no antibacterial effect after being cured, which may explain why composites accumulate more plaque than other filling materials. The attempts to provide composites with antibacterial properties involve alterations to the resin components and filler components, and the trials can be subsequently classified into two groups based on the release profile of antibacterial components; agent-releasing or non-agent-releasing materials. Each type of antibacterial composite has advantages and disadvantages, and further modifications are needed to achieve clinically useful materials. Among proprietary dentin bonding systems (DBS), the products which contain glutaraldehyde or have an acidic property exhibit some antibacterial effects. However, the antibacterial properties shown by these products are only side-effects which are derived from the constituents included to produce superior bonding characteristics, and appear to be unreliable. Inclusion of antibacterial components into DBS has also been attempted using several methods, and the results of in vitro tests indicate that some of the trials seem promising. It is worthy of continuing the attempts to develop DBS which can inhibit invading bacteria after the placement of restoration as well as residual bacteria in the cavity. Achievement of bio-functional composites or DBS with therapeutic effects would contribute to prevent secondary caries.     

Salivary esterase activity and its association with the biodegradation of dental composites

Pseudocholinesterase (PCE) and cholesterol esterase (CE) can hydrolyze bisphenylglycidyl dimethacrylate (bisGMA) and triethylene glycol dimethacrylate (TEGDMA) monomers. This study will test the hypothesis that enzyme activities showing CE and PCE character are found in human saliva at levels sufficient to hydrolyze ester-containing composites important to restorative denstistry. The study also seeks to ask if the active sites of CE and PCE with respect to composite could be inhibited. Photo-polymerized model composite resin was incubated in PCE and CE solutions, in the presence and absence of a specific esterase inhibitor, phenylmethylsulfonyl fluoride (PMSF). Incubation solutions were analyzed for resin degradation products by high-performance liquid chromatography (HPLC), UV spectroscopy, and mass spectrometry. Saliva was found to contain both hydrolase activities at levels that could degrade composite resins. PMSF inhibited the composite degradation, indicating a material hydrolysis mechanism similar to the enzymes' common function.