降低光固化收缩的研究进展

光固化是一种快速、高效且低能耗的固化手段,在诸多领域具有重要应用价值。光固化过程中易产生固化收缩,较快的交联速度导致收缩应力难以释放,显著影响材料的尺寸精度、力学性能及使用稳定性,这些不足引起了众多研究学者的关注。文中综述了光固化收缩产生的原因和主要影响因素,详细介绍了近年来有效降低收缩程度的技术手段和方法,具体实施效果及目前仍然存在的问题,为光固化进一步的研究提供参考。     

Temperature rises during tooth bleaching with different light-curing units

The aim of this study was to evaluate the influence of three different light-curing units on the temperature rise induced in the pulpal cavity, when bleached with 35% hydrogen peroxide (HP). Forty extracted maxillary central incisors were randomly divided into four groups according to photoactivation procedure (n = 10). Whiteness HP (WHP) bleaching agent which contains 35% HP bleach was placed on the facial tooth surface and no photoactivation device was used (control); an blue light-emitting diode (LED, 40 s), a diode laser (4 W, Continous mode, 20 s), and Nd:YAG laser (4 W, 60 Hz frequency, 20 s). Temperature rise in the pulpal chamber was measured with a J-type thermocouple wire that was connected to a data logger before and immediately after each 20–40 s application. One tooth of each group was selected for scanning electron microscope analysis. Data were analyzed using one-way ANOVA followed by the Games Howell post hoc test at a preset α of 0.05. One-way ANOVA revealed that there was a significant difference among the light-curing units (p < 0.05) and between control group and light-curing units (p < 0.05). The Nd:YAG induced significantly, which resulted in higher temperature increase than other light-curing units (10.7 °C). The LED unit produced the lowest temperature changes (3.2 °C) among the light-curing units. The presence of the bleaching gel did not cause a temperature increase in control group (0 °C). The results suggested that using light-curing units caused temperature changes in the intrapulpal cavity during tooth bleaching. The use of LED will be more safer for pulpal health when assisted with WHP bleaching gel.     

Properties of a new dental photocurable resin based on the expanding monomer and three-component photoinitiator system

The purpose of this study was to use. a three-component photoinitiation system comprising 1wt% CQ （camphorquinone）, 2wt% DMAEMA （2-（dimethylamino） ethyl meth acrylate） and 2wt% ph^2I^＋PF6^- （diphenyliodonium hexafluorophosphate） to initiate the copolymerization of the matrix resins which combine bisphenol-S-bis （3-methacrylate-2-hydroxy propyl） ether （BisS-GMA） with the expanding monomer unsaturated spiro orthoesters 2-methylene-l,4,6-tdspiro[4,4] nonane （MTOSN）, for minimizing the volumetric shrinkage that generally occurs during polymerization. It was hypothesized that MTOSN would expand volumetrically during polymerization under the three-component photoinitiator system and further reductions in volumetric shrinkage would be obtained. The performance study which consists of degree of conversion and condition of the ring-opening reactions of MTOSN, volumetric shrinkage and mechanical properties including tensile bond strength, compressive strength and Vicker＇s hardness were carried out respectively by Fourier transfer infrared, the dilatometer and the universal testing machine. The results supported that the dental composites based on the expanding monomer and three-component photoinitiator system engendered a greater decrease of volumetric shrinkage and better mechanieal properties.     

氟化聚氨酯弹性体光固化粘接性能的改性研究

分别以甲苯二异氰酸酯和异佛尔酮二异氰酸酯与含氟聚醚多元醇ZDOL-1000反应,并以不同比例的三羟甲基丙烷单烯丙基醚扩链剂与自制扩链剂进行改性,获得一系列改性氟化聚氨酯弹性体。对各弹性体样品的机械性能、热力学性能和表面能进行了表征,并测试了各弹性体的光固化粘接性能。结果表明,在光固化氟碳树脂作为胶粘剂的情况下,2种扩链剂可以克服氟化聚氨酯难以附着的缺点,起到改善粘接性能的作用;三羟甲基丙烷单烯丙基醚更利于提升附着力,而且在甲苯二异氰酸酯体系中表现更突出。     

A polymeric nanocomposite system for potential adhesive applications in restorative dentistry

This article presents and discusses the preliminary results obtained as a continuation of a work aiming to contribute to the effort of exploring the potential of certain types of polymer nanocomposites to be successful candidates in new fields such as dental restoration. An epoxy-functional silicate-/Zr-based polymeric nanocomposite material system containing phosphorus was obtained via a sol–gel method, and applied to bring about a bonding between bovine teeth and feldspathic ceramic discs with or without the use of visible light (VL)-curing process. Infrared spectroscopy was employed to show the presence of phosphorus within the structure. Mechanical tests were performed to determine the shear-bond strength of the nanocomposite adhesive system developed. An approximate shear-bond strength value of 0.4 MPa was obtained for both VL-cured and uncured systems. Though this value was lower than that of commercially available material systems, it was promisingly comparable to them. Another significant finding was that the material system developed within the study might potentially eliminate the use of curing process. Also, it was demonstrated that the general problem of ‘shrinkage-upon-polymerization’ could be overcome by use of a polymeric nanocomposite adhesive material system of this type. Overall results indicated that this polymeric nanocomposite system could indeed be potentially considered as an adhesive alternative in prospective dental restoration applications.     

基于光固化的液芯光纤及其性能

研究了液芯光纤及其芯液的性能,以及液芯光纤包层裂纹损伤的修复效果和修复原理。结果表明：该液芯光纤具有数值孔径大,传光性好等特点;芯液的光固化速度快,能够修复光纤包层裂纹,延长了光纤的使用寿命。该液芯光纤不仅可用于传感,而且由于芯液的特殊性使其能够用于光纤智能复合材料的自诊断和自修复。     

煤矸石中高岭石的结晶度研究

煤矸石中的主要矿物质是高岭石等黏土。高岭石结晶度的好坏对于煤矸石的应用起着极其重要的作用。通过XRD、FTIR、SEM等测试手段分析发现,大同煤矿集团塔山矿区开采出来的煤矸石中的高岭石含量高且结晶度较好,属于有序至高度有序范围内,可以通过插层等手段生产纳米级煤系高岭土等深加工产品。     

3D打印用长波紫外光固化树脂的制备

通过优化引发剂的种类和用量,得到一系列阳离子和自由基混杂体系光固化树脂,并用旋转流变仪和SLA型3D打印机进行长波紫外光固化和3D打印成型。结果表明:与芳基鎓盐类阳离子光引发剂PAG202相比,芳茂铁盐类阳离子光引发剂261具有长波紫外光固化的适应性,而光敏增感剂PAS-50对光引发剂261敏化显著,在长波紫外光下光引发剂261/PAS-50体系能快速引发树脂固化。最佳配方时,固化树脂的弯曲模量高于国内外同类树脂的,且具有较低的固化收缩率。     

改性环氧树脂光固化速粘胶的粘接应用研究

采用玻璃纤维布/光固化胶粘剂复合材料补片,实现对铝合金片的快速粘接与固化。考察了国产UV胶粘剂预聚物和进口UV胶的粘接性能、耐温性能以及粘接强度随胶粘剂相对分子质量及其分布的变化规律。结果表明:进口光固化胶/玻璃纤维布复合材料补片与铝合金片的剪切强度在14.5～23.1MPa之间,国产光固化胶体系剪切强度在11.3～16.6MPa之间,两者均高于铆接强度(10.3MPa);作为胶粘剂基体树脂,相对分子质量分布越宽越有利于粘接强度的提高;此外,-40℃低温与100℃高温对体系粘接强度的影响很小(不超过10%)。     

Influence of ceramic thickness and light-curing time on the long-term µTBS of silica-based ceramic to human dentin

To evaluate the influence of ceramic thickness, light-curing time and thermal cycling (TC) on the μTBS of a glass ceramic cemented to human dentin. Ninety-six human molars were embedded in acrylic resin and the occlusal surface was sectioned to exposure dentin. Blocks of feldspathic ceramic (Vita PM9) with different thickness (6 × 6 × 1 mm/2 mm/3 mm) were fabricated with wax pattern and sprue. The blocks and teeth were randomly distributed into 12 groups (n = 8) according to the ceramic thickness (V1: 1 mm, V2: 2 mm and V3: 3 mm), light-curing time (40s; 80s), and TC (yes; no). Dentin was etched, washed and dried. The adhesive (Excite, Ivoclar) was applied onto the dentin surface and light-cured (20s), and the ceramic surface was etched with 10% HF, washed, dried and silanized. The ceramic blocks were cemented to dentin (Variolink II, Ivoclar). The assembly ceramic/dentin was stored in distilled water (37 °C; 24 h) and sectioned in X and Y axes to get the sticks. Half of the samples were submitted to TC while the other half underwent micro-tensile bond testing. The data (MPa) were analyzed by 3-way ANOVA and Tukey test (5%). ANOVA revealed significant interaction among the factors (p = 0.0001). Tukey test showed significant higher bond strength for the 2 mm group (V280s = 17.0 ± 9.1 MPa) in comparison to the other groups. V340s TC (2.7 ± 6.3 MPa) presented lower bond strength, which was similar to the groups V180s TC (4.6 ± 4.9 MPa) and V240s TC (5.9 ± 4.4 MPa). Light-curing for 80s promoted significant higher bond strength of thicker ceramic (3 mm) than light-curing for 40s.