Effect of solvent type and content on monomer conversion of a model resin system as a thin film

OBJECTIVE: The purpose of this study was to examine the effect of solvent concentration on the degree of conversion of a model photo-activated resin formulation when placed as a thin film in ambient air. METHODS: A photo-activated co-monomer mixture (ethoxylated bis-GMA/TEGDMA) (Bisco Inc.) was diluted into six concentrations (from 1.0 to 13.0M) with either acetone or ethanol. A controlled volume of diluted, uncured resin was placed on the horizontal surface of an attenuated reflectance unit and the infrared (IR) spectrum obtained. A light emitting diode light-curing source (Bluephase, Ivoclar/Vivadent) then immediately irradiated the specimen for 10s (n=5). Five minutes after exposure, IR spectra of the cured material were obtained, and monomer conversions were calculated using standard methods that monitored changes in aliphatic-to-aromatic CC absorbance ratios in the uncured and cured states. RESULTS: In the acetone/model resin system, maximum conversion occurred with 2.5-5.0M solvent. In the ethanol/model resin system, conversion peaked at 2.5M solvent. Above 5.0M solvent, conversion values declined rapidly for both solvents. A 13.0-M solution resulted in near 0% conversion for both solvents. At 2.5 and 5.0M acetone, conversions exceeded those of equivalent concentrations of the ethanol-based system. CONCLUSIONS: For both an acetone- and ethanol-solvated model resin system, conversion did not immediately decrease with addition of solvent, but instead increased over that of the model resin alone. At higher solvent content (greater than 2.5M ethanol and 5.0M acetone), conversion rapidly declined, with ethanol causing less conversion at equal-molar solvent concentrations.     

Digital image correlation in dental materials and related research: A review

ObjectiveDigital image correlation (DIC) is a non-contact image processing technique for full-field strain measurement. Although DIC has been widely used in engineering and biomechanical fields, it is in the spotlight only recently in dental materials. Therefore, the purpose of this review paper is introducing the working principle of the DIC technique with some modifications and providing further potential applications in various dental materials and related fields.MethodsThe accuracy of the algorithm depending on the environmental characteristics of the DIC technique, as well as the advantages and disadvantages of strain measurement using optical measurements, have been elaborated in dental materials and related fields. Applications to those researches have been classified into the following categories: shrinkage behavior of light-cured resin composite, resin-tooth interface, mechanical properties of tooth structure, crack extension and elastic properties of dental materials, and deformation of dental restoration and prosthesis. This classification and discussion were performed using literature survey and review based on numerous papers in the international journals published over the past 20 years. The future directions for predicting the precise deformation of dental materials under various environments, as well as limitations of the DIC technique, was presented in this review.ResultsThe DIC technique was demonstrated as a more effective tool to measure full-field polymerization shrinkage of composite resin, even in a simulated clinical condition over the existing methods. Moreover, the DIC combined with other technologies can be useful to evaluate the mechanical behavior of material-tooth interface, dentine structure and restorative and prosthetic materials with high accuracy. Three-dimensional DIC using two cameras extended the measurement range in-plane to out-of-plane, enabling measure of the strain directly on the surface of dental restorations or prosthesis.SignificanceDIC technique is a potential tool for measuring and predicting the full-field deformation/strain of dental materials and actual prostheses in diverse clinical conditions. The versatility of DIC can replace the existing complex sensor devices in those studies.     

Minimization of the inevitable residual monomer in denture base acrylic

OBJECTIVES: Residual monomer ([MMA](R)) in denture base acrylic continues to be of concern. The response surface of concentration vs. time and temperature for the equilibration of methyl methacrylate (MMA) and its polymer (PMMA) allows a prediction of the time to the minimum at any temperature for a closed system. It was the purpose here to determine whether this prediction applies to normal denture base processing, and whether optimum conditions could be identified. METHODS: Denture bases were processed following normal laboratory procedures, including pre-cure for 3 h at 70 degrees C for all tests. Commercial powder and liquid were used at either 95 or 100 degrees C, or a plain PMMA powder and the same liquid at 95 degrees C, for times ranging from 5 to 192 h. Residual MMA was determined by gas chromatography. RESULTS: [MMA](R) decreased steadily from approximately 0.25% to as low as approximately 0.07% with increasing time at temperature, but did not approach equilibrium. The rate of diffusive loss of MMA appears to exceed the rate of depolymerization. SIGNIFICANCE: Residual monomer is inevitable for all PMMA-based products no matter what the curing conditions are. However, extended time at high temperature can allow low values to be attained, and the time allowed can compensate for processing temperatures somewhat lower than the ordinarily recommended 100 degrees C. It is suggested that overnight processing at 95 degrees C should be adopted to minimize [MMA](R) and save energy. This result is of importance for work at high altitude.     

High performance dental resin composites with hydrolytically stable monomers

Objective

The objectives of this project were to: 1) develop strong and durable dental resin composites by employing new monomers that are hydrolytically stable, and 2) demonstrate that resin composites based on these monomers perform superiorly to the traditional bisphenol A glycidyl dimethacrylate/triethylene glycol dimethacrylate (Bis-GMA/TEGDMA) composites under testing conditions relevant to clinical applications.

Advances in dental materials

The use of materials to rehabilitate tooth structures is constantly changing. Over the past decade, newer material processing techniques and technologies have significantly improved the dependability and predictability of dental material for clinicians. The greatest obstacle, however, is in choosing the right combination for continued success. Finding predictable approaches for successful restorative procedures has been the goal of clinical and material scientists. This article provides a broad perspective on the advances made in various classes of dental restorative materials in terms of their functionality with respect to pit and fissure sealants, glass ionomers, and dental composites.     

几种常用口腔材料细菌粘附性能比较

目的：探讨5种口腔常用材料的抗细菌粘附性能。方法将自凝甲基丙烯酸甲酯基托树脂、Z250复合树脂、氧化锆陶瓷、纯钛和镍铬合金5种牙科常用修复材料,分别制备成3．0cm ×2．0cm ×0．2cm的板片试件,每组各5片。各组试件表面进行抛光处理,使试件表面粗糙度( Ra)值无显著性差异。实验菌株选用变形链球菌,用细菌悬浮液置试件表面,37℃培养48h,对粘附在材料表面的细菌再进行洗脱、培养、菌落计数,使用SPSSl7．0软件对试验结果进行统计分析。结果纯钛表面变形链球菌粘附量最低,依次为氧化锆陶瓷、Z250复合树脂、镍铬合金、自凝甲基丙烯酸甲酯基托树脂。结论不同口腔材料在同样粗糙度的条件下,抗细菌粘附性能存在差异,钛具有较好的抗细菌粘附性能。     

Radiodensity of base, liner and luting dental materials

The aim of this study was to determine the radiodensity of base, liner and luting dental materials and to compare them with human enamel and dentin. Four classes of materials were examined: conventional glass ionomers (CG)—Vitro Cem, Ketac Bond, Vidrion F, Vidrion C; resin-modified glass ionomers (RMGI)—Fuji II LC, Vitrebond; resinous cement (RC)—Rely-X ARC; and zinc phosphate cement (ZP)—Cimento LS. Five 2-mm-thick standard samples of each material and five 2-mm-thick enamel and dentin samples were produced. An aluminum step wedge served as control. Samples were positioned over a phosphor plate of Digora digital system, exposed to X-ray, and the radiodensity obtained in the software Digora for Windows 2.0. Data were submitted to Kruskal–Wallis and Dunnett multiple comparisons test (α=0.05). According to statistical analysis, the following sequence in degree of radiodensity could be seen among the groups: Cimento LS (ZP) > Vitro Cem (CG) = Fuji II LC (RMGI) = Rely-X ARC (RC) = Vitrebond (RMGI) > Ketac Bond (CG) > enamel = Vidrion F (CG) > Vidrion C (CG) = dentin. The presence of radiopaque fillers such as zinc, strontium, zirconium, barium, and lanthanium rather than material type seems to be the most important factor when analyzing material radiodensity. Almost all investigated materials presented an accepted radiodensity.     

A comparative life cycle assessment of dental restorative materials

ObjectivesDifferent types of direct-placement dental materials are used for the restoration of structure, function and aesthetics of teeth. The aim of this research investigation is to determine, through a comparative cradle-to-gate life cycle assessment, the environmental impacts of three direct-placement dental restorative materials (DRMs) and their associated packaging.MethodsThree direct-placement dental materials; dental amalgam, resin-based composite (RBC) and glass polyalkenoate cements (GIC) are assessed using primary data from a manufacturer (SDI Limited, Australia). The functional unit consisted of ‘one dental restoration’ of each restorative system under investigation: 1.14 g of dental amalgam; 0.25 g of RBC (plus the adhesive = 0.10 g); and 0.54 g of GIC. The system boundary per restoration included the raw materials and their associated packaging materials for each DRM together with the processing steps for both the materials and packaging. The environmental impacts were assessed using an Egalitarian approach under the ReCiPe method using Umberto software and the Ecoinvent database. Nine different impact categories were used to compare the environmental performance of these materials.ResultsDental amalgam had the highest impact across most of the categories, but RBC had the highest Global Warming Potential. The highest sources of the environmental impacts for each restorative material were: Amalgam, derived from material use; RBC, derived from energy use in processing material and packaging material; GIC, derived from material and energy use for packaging.SignificanceLess intensive energy sources or more sustainable packaging materials can potentially reduce the impacts associated with RBC and GIC thus making them suitable alternatives to dental amalgam.     

两种新材料修复楔状缺损的临床效果评估

目的 应用改良的ＵＳＰＨＳ系统评估两种新材料－－光凝单组份复体和光固化玻璃离子水六汀修复楔状缺损牙齿的临床疗效。方法 门依用Ｄｙｒａｃｔ修复楔缺 ３１７颗,用３Ｍ－Ｖｉｔｒｅｍｅｒ修复楔缺牙１９２颗,用改良ＵＳＰＨＳ系统对１年３主２年的随访结果进行评估。结果 Ｄｙｒａｃｔ组１年成功率９１．１７％,２年成功率８８．６４％;３Ｍ＿Ｖｉｔｒｅｍｅｒ组１年成功率８１．７７％,２年成功率８０．２１％。两组成     

六种常用冠修复材料的摩擦磨耗性能比较

目的 探讨6种常用冠修复材料与滑石瓷对磨时的摩擦磨耗性能,为口腔常用冠修复材料的摩擦磨耗性能与牙釉质的匹配性提供依据.方法 使用MMJ-5G微机控制高温端面磨损实验机,以滑石瓷为对磨物,以15颗因正畸拔除的上颌第一前磨牙制作的10个试件为对照组,对纯钛(A组)、钴铬合金(B组)、Superporcelain Ti-22体瓷(C组)、喜美乐体瓷(D组)、松风饰瓷(E组)、e.max饰瓷(F组)(每组均为10个试件)与滑石瓷组成的摩擦副在37℃人工唾液润滑工况下进行摩擦磨耗实验.记录动态摩擦系数曲线、计算体积磨损百分比,扫描电镜观察表面磨损形貌.结果 试件体积磨损百分比由大至小为:对照组[(90.17×10-4)％]、A组[(79.23×10-4)％]、C组[(23.31 ×10-4)％]、D组[(20.41×10-4)％]、F组[(19.22 × 10-4)％]、E组[(8.53 × 10-4)％]、B组[(2.54×10-4)％].滑动摩擦系数由大到小依次是:D组(0.65)、C组(0.45)、E组(0.40)、A组(0.35)、B组和F组(0.30).扫描电镜观察显示,E组表面最光滑,以下依次是F组、D组、C组.结论 纯钛与天然牙磨耗性能相近,是理想的修复金属材料.4种瓷粉中Surperporcelain Ti-22体瓷磨损滑石瓷最少.     

多媒体技术在口腔材料性能教学中的应用

为进一步优化教育管理和教学过程,适应教育改革的潮流和趋势,教育部于1999年就已提出,在高校普及和运用以多媒体计算机技术为核心的教育技术应用模式是推进教育信息化进程的关键一步.按照这一思路,北京大学口腔医学院尝试对口腔材料学材料性能的教学方式进行改革,引入多媒体技术.通过对教学内容进行深入分析,将课程讲授重点分别采用动画短片和录像方式进行详尽的讲解,其他概念多配以图片进行讲解.课件制作完成后,在2006级和2007级的八年制学生中进行了实际使用,并根据课件内容设计了调查问卷,调查问卷结果显示,课件教学效果良好.     

四种热压膜正畸材料力学性能的比较

目的比较临床常用的4种热压膜材料在不同条件下的力学性能,为临床制作隐形矫治器选择材料提供依据。方法A、B、C和D4种热压膜材料厚度均为1.0 mm。测试在3种处理方式下进行：未处理、热成形后和恒温水浴浸泡两周后,比较材料在以上处理后的拉伸屈服应力和断裂伸长率,并比较材料在室温条件下,1h内的应力松弛速率。结果经热成形后,4种材料拉伸屈服应力均低于未处理组,断裂伸长率均大于未处理组;经浸泡两周后,4种材料拉伸屈服应力均高于热成形组,而断裂伸长率均小于热成形组。除材料A外,不同处理方式对其他3种材料力学性能的影响具有统计学意义(P＜0.05)。在室温条件下,A材料1h内的应力松弛速率为0.01 N/s,显著低于C和D(p ＜0.05),与B相比,差异无统计学意义(P＞0.05)。结论热压膜材料的力学性能受到使用环境的影响,A材料的力学性能在不同测试条件下表现最佳,与其他3种材料相比,适宜制作隐形矫治器。     

不同牙科金属材料致敏性的比较

目的: 比较分析牙科金属材料的致敏性, 为今后科学选择牙科金属材料提供指导。方法: 对92例口腔内含金属修复体的受试者进行斑贴试验。采用SPSS 17.0软件包对相关数据进行Pearsonχ2检验、校正的χ2检验和Fisher确切概率检验。结果: ①不同金属材料的过敏率不同, 镍(Ni)的过敏率最高22.8%, 铝(Al)的过敏率为0。②对钯(Pd)和镍(Ni)过敏者中, 女性多于男性, 差异具有显著性(P<0.05)。③女性中, 穿耳者镍(Ni)的阳性率较高, 但穿耳与镍(Ni)过敏无相关关系(P>0.05)。④钯(Pd)和镍(Ni)之间存在交叉过敏, 对钯(Pd)过敏者中, 83.3%对镍(Ni)过敏;对镍(Ni)过敏者中, 47.6%对钯(Pd)过敏。⑤斑贴试验可出现迟发反应。结论: 牙科金属材料具有一定的过敏率, 女性对钯(Pd)和镍(Ni)的过敏率显著高于男性。斑贴试验可出现迟发反应, 必要时可观察96 h、7 d甚至更长时间的结果, 以排除假阴性。     

Concepts in biocompatibility testing of dental restorative materials

Due to the diversity of adverse biological effects which might be caused by dental restorative materials, biocompatibility assessment cannot rely on a single test but has to be based on a planned and structured approach (concept). First, the possible harm evoked by the material, the known data, and suitable biological and other test methods available must be taken into consideration. Modern regulatory concepts require for this purpose the services of experts to propose the appropriate set of required tests for a given material. The use of standards is generally emphasized because of better comparability of the data. Other tests may be chosen if more appropriate. Modern scientific concepts of biocompatibility testing are based on the need for rapid and cost-effective test methods, avoiding animal tests whenever possible. While formerly in vitro experiments did not take into account the special clinical situation in which the material would be used, modern concepts try to simulate important parameters of the in vivo situation as closely as possible. This may be achieved, for example, by including suitable barriers between the material and the target cells, by constructing appropriate target cells, and by choosing clinically relevant markers for measuring the biological effects caused by the material. There are indications so far that through this approach the number of animal tests can be reduced. The use of these methods may also lead to a better understanding of the mechanisms behind the biological reactions (mechanistic approach) in describing the biocompatibility of dental restorative materials. Received: 22 September 1997 / Accepted: 28 October 1997     

Translucency thresholds for dental materials

Objective

To determine the translucency acceptability and perceptibility thresholds for dental resin composites using CIEDE2000 and CIELAB color difference formulas.

金属修复体表面粗糙度对其磨耗性能的影响

目的：采用标准化牙釉质试件与金属材料试件对磨的方式,评价常用的几种口腔修复材料在不同表面粗糙度下的磨耗性能。方法：以镍基铸造合金、镍基合金、钴铬钼合金和钛合金4种合金材料作为对磨材料样本,牙釉质为磨耗样本,进行磨耗实验,定量检测牙釉质样本的磨耗量,采用SAS14.0软件包对数据进行统计学分析。结果：与镍基铸造合金180目组和400目组对磨的牙釉质平均磨耗量无显著差异,而与400目组与1200目组对磨的牙釉质试件平均磨耗量差异显著。与3种不同粗糙度的钴铬钼合金、镍铬合金及不同处理组钛合金对磨的牙釉质试件平均磨耗量之间均有显著差异。结论：镍铬合金、钴铬钼合金、钛合金的表面粗糙度对牙釉质的磨耗量会产生影响,粗糙程度大的金属,会显著增加牙釉质的磨耗量。     

口腔常用修复材料的 CBCT 影像灰度值差异的探索

目的：探索口腔常用修复材料在 CBCT 影像中的灰度值的差异规律。方法：采用 CBCT 扫描36种口腔常用修复材料立方体,Mimics 软件读取断层影像灰度值的方法。结果：探索到了36种口腔常用修复材料在 CBCT 影像中灰度值间的差异规律,即灰度值不仅在不同类材料间有大的差异,在同类不同品型材料间亦有较大的差别。结论：口腔常用修复材料在 CBCT 影像中的灰度值差异规律,提供了建立三维数字模型时选取材料和材料组合的客观依据。     

比较PBL与传统教学在口腔材料学教学中的效果

目的有关口腔材料学的PBL教学模式目前在国内尚处于探索阶段,本文比较PBL教学和传统教学这两种教学模式在口腔材料学中的教学效果,旨在提高口腔材料学的教学水平。方法选择口腔材料学教材中的"复合树脂"章节为授课内容,一组按PBL教学模式授课,另一组按传统教学模式同班授课,通过口腔材料学考试成绩和调查问卷两项指标对教学效果进行评价,在理论教学中开展两种教学模式的对比分析。结果与传统教学模式相比,接受PBL教学的学生在复合树脂章节的考试成绩明显得到提高(P<0.01)。在意见调查中,80%以上的受试学生认为PBL教学模式在能力培养上优于传统教学模式。结论PBL教学模式在口腔材料学教学中不仅可行,而且可能更有助于学生对口腔材料知识的理解和掌握。     

应用新型体外实验系统对牙科修复材料抗磨损性的研究

目的：评价牙科复合树脂材料的抗磨损性。方法：应用程控多功能口腔模拟机和三维图像激光测试仪对４种牙科复合树脂进行抗磨损性的实验研究。结果：材料磨损坑体积大小的顺序为：牙釉质〈Ｔａｒｇｉｓ Ｄｅｎｔｉｎ〈Ｄｅｎｔａｃｏｌｏｒ〈Ａｒｔｇｌａｓｓ〈Ｖｉｔａ Ｚｅｔａ。磨损坑最深点大小的顺序为：牙釉质〈Ｔａｒｇｉｓ Ｄｅｎｔｉｎ〈Ａｒｔｇｌａｓｓ〈Ｄｅｎｔａｃｏｌｏｒ〈Ｖｉｔａ Ｚｅｔａ。结论：Ｔａｒｇｉｓ     

Methods to evaluate and strategies to improve the biocompatibility of dental materials and operative techniques

Objective

The general aim of this article is to describe the state-of-the-art of biocompatibility testing for dental materials, and present new strategies for improving operative dentistry techniques and the biocompatibility of dental materials as they relate to their interaction with the dentin–pulp complex.

Methods

The literature was reviewed focusing on articles related to biocompatibilty testing, the dentin–pulp complex and new strategies and materials for operative dentistry. For this purpose, the PubMed database as well as 118 articles published in English from 1939 to 2014 were searched. Data concerning types of biological tests and standardization of in vitro and in vivo protocols employed to evaluate the cytotoxicity and biocompatibility of dental materials were also searched from the US Food and Drug Administration (FDA), International Standards Organization (ISO) and American National Standards Institute (ANSI).

Results

While there is an ongoing search for feasible strategies in the molecular approach to direct the repair or regeneration of structures that form the oral tissues, it is necessary for professionals to master the clinical therapies available at present. In turn, these techniques must be applied based on knowledge of the morphological and physiological characteristics of the tissues involved, as well as the physical, mechanical and biologic properties of the biomaterials recommended for each specific situation. Thus, particularly within modern esthetic restorative dentistry, the use of minimally invasive operative techniques associated with the use of dental materials with excellent properties and scientifically proved by means of clinical and laboratory studies must be a routine for dentists. This professional and responsible attitude will certainly result in greater possibility of achieving clinical success, benefiting patients and dentists themselves.

Significance

This article provides a general and critical view of the relations that permeate the interaction between dental materials and the dentin–pulp complex, and establish real possibilities and strategies that favor biocompatibility of the present and new products used in Dentistry, which will certainly benefit clinicians and their patients.