晶须-颗粒复合体对光固化复合树脂力学性能的影响

目的 研究硼酸铝晶须-二氧化硅颗粒(ABw-SiO2)复合体对光固化牙科复合树脂弯曲性能的影响.方法 以ABw和SiO2比例、正硅酸乙酯(TEOS)用量、硅烷偶联剂用量和填料复合体用量作为实验因素,设计L9(3)4正交试验,制作试件并测试其弯曲强度和弯曲弹性模量;利用扫描电镜观察熔附体形貌.并对弯曲性能最优组与最差组试件行断面扫描.以未加填料的基质组作为阴性对照,Z100(A2色)为阳性对照.结果 最优组弯曲强度达(123.14±17.37)MPa,与基质组差异有统计学意义.与Z100(A2)复合树脂间差异无统计学意义;弯曲弹性模量为(8.75±0.459)GPa.结论 正交试验因素对光固化牙科树脂的弯曲性能有显著影响;ABw-SiO2填料复合体可以显著提高光固化牙科树脂的弯曲性能.     

晶须熔附条件对晶须增强复合树脂性能的影响

目的：探讨不同熔附条件对新型牙科复合树脂弯曲性能的影响。方法：将自制的以硼酸铝晶须（ABw）和二氧化硅（SiO2）为主要成分的新型牙科复合树脂混合填料在不同熔附条件下制作试样并测试其弯曲强度和弯曲弹性模量;利用透射电镜（TEM）观察高温处理过程对晶须表面形态的影响。结果：ABw-SiO2熔附体复合填料可显著提高牙科复合树脂的弯曲性能;高温处理过程并未破坏ABw表面形态;熔附温度和时间为900℃、30 min时新型牙科复合树脂的弯曲强度达（151.90±8.89）MPa。结论：不同熔附条件改善了新型牙科复合树脂的弯曲性能。     

照射距离和时间对可见光固化复合树脂固化深度的影响

在不同的距离和时间内,用固化灯对可见光固化复合树脂进行照射,并测定其固化深度。照射距离在3mm以内,时间20s,色浅的复合树脂固化深度一般为4～5mm,色深者为3～4mm;随着距离延长,固化深度减少,至10mm时,固化深度约为3mm以内的7/10～9/10,延长光照时间,可加深固化深度,每延长1倍时间,固化深度增加1/10～2/10,光照时间至120s,已接近固化极限。混合填料复合树脂比超微填料复合树脂固化深度稍深。在单位面积内,同等照射时间,连续照射或间隔照射,固化深度无明显差异。不同的固化灯对复合树脂的固化深度不同,除导光索、滤光片等因素外,灯泡的质量影响最大,国产灯泡质量不稳定,使用时应注意选择。文章对测试中出现问题进行了讨论。     

电压与光固化时间对复合树脂固化深度的影响

本文测量了在不同电压下,不同的光固化时间时,光固化复合树脂的固化深度。发现：２２０Ｖ电压下,光固化时间从２０Ｓ延长到４０Ｓ时,光固化复合树脂的固化深度增加０．１５ｍｍ,延长到６０Ｓ时,增加０．２６ｍｍ。光固化时间延长,树脂的固化深度增加不多。２００Ｖ电压下,光固化时间从２０Ｓ延长到４０Ｓ时,固化深度增力００．４８ｍｍ,延长至６０Ｓ时,固化深度可增加０．８１ｍｍ。光固化时间延长,光固化复合树脂的固化深度明显增加。     

不同晶须及晶须用量对复合树脂力学性能的影响

目的：比较碳化硅晶须（SiCw）、硼酸铝晶须（ABw）、氧化锌晶须（ZnOw）增强复合树脂的弯曲性能,筛选最优配方。方法：测定复合树脂的弯曲强度和弯曲弹性模量：结果：β-SiCw熔附SiO2纳米粒子（β-SiCw／SiO2）、ABw熔附SiO2纳米粒子（ABw／SiO2）、ZnOw（四针状）均可以提高复合树脂的弯曲性能。本实验条件下复合树脂弯曲性能的最佳方案是：填料为ABw／SiO2,用量为60％时。结论：每一种晶须填料均可以提高复合树脂的弯曲强度和弯曲弹性模量,提高的程度与填料的用量相关。     

光固化复合树脂固化程度的影响因素

影响光固化复合树脂固化程度的因素很多,本文就不同类型的光固化灯、复合树脂及临床操作等因素对光固化复合树脂固化程度的影响作一综述。     

口腔材料学教学实验课设计:光照条件对光固化复合树脂性能的影响

光固化复合树脂经光固化灯照射后固化,其临床性能在很大程度上受所用的光固化灯的影响,特别是光照强度和光照时间对其影响更为显着。为了帮助学生了解光照条件对光固化复合树脂性能的影响,北京大学口腔医学院在口腔材料学实验课教学中设计了两个实验:光固化复合树脂的固化深度实验和光固化复合树脂的挠曲强度实验。通过实验使学生掌握光照射时间和光照强度对光固化复合树脂固化深度和挠曲强度的影响规律。实验设计完成后,在2008级的八年制学生中进行了实际使用,并根据实验内容设计了调查问卷。问卷结果显示,实验课效果良好。     

硫酸钙和硫酸镁晶须对复合树脂维氏硬度的影响

目的　探讨硫酸钙和硫酸镁晶须对复合树脂的维氏硬度的影响。方法　制备硫酸钙和硫酸镁晶须,以硬脂酸钠改性剂表面改性,随后分别按1%、10%、20%、30%的比例混合入复合树脂中,固化后测量各组试件表面维氏硬度。结果　两种晶须的添加比例为20%和30%时,树脂的表面维氏硬度均增加,硫酸镁晶须添加量多时树脂表面硬度相应增加。结论　添加适当比例的硫酸钙和硫酸镁镁晶须可以提高复合树脂的表面硬度。     

复合树脂的不同固化方法对抗压强度影响

目的 探讨不同固化方法处理后对复合树脂抗压强度的影响。方法 采用光固化、光固化＋光固化、光固化＋热固化,3种不同固化方法处理3M和贺利氏复合树脂,在万能验试机上测试抗压强度。结果 2次处理的复合树脂抗压强度均比1次处理的复合树脂有较大提高,范围在51.8%-91.6%之间。不同的2次固化方法相比,统计学无显著差异。结论 复合树脂经2次固化方法处理,其抗压强度高于1次光固化方法的处理。     

Selected curing characteristics of light-activated composite resins

The purpose of this study was to clarify some curing characteristics of light-activated composite resins. Three visible light-activated and 1 UV light-activated resin were cured with each generator recommended by the manufacturer. The relative degree of cure was determined using Knoop hardness measurements on the irradiated and longitudinally sectioned surfaces of cylindrical specimens. The maximum surface hardness numbers were obtained from the area just under the top of the specimen (0.5 to 1.0 mm below the irradiated surface) and the hardness gradually decreased with the depth. In the specimens cured in 100% N₂ gas environment, the degree of cure on the irradiated surface was improved. Coloring agents in composites have an effect on decreasing the degree of cure. Re-irradiation on the longitudinally sectioned surface of the specimen increased the degree of deep cure. The degree of cure at each depth was improved by prolonged irradiation time.     

Microfracture behaviour of composite resins containing irregular-shaped fillers

Microfracture behaviour of composite resins containing irregular-shaped fillers was understood by filler morphology observation, fracture toughness test and acoustic emission (AE) detecting method. The fracture toughness (KIC) was obtained by using single edge notched specimens. AE, the elastic wave due to the debonding of filler from the resin matrix or the fracture of filler itself, was detected during fracture toughness test. The reasons for the different fracture toughness values of composite resin, in spite of having almost the same morphology and filler content, were understood by the results of fracture surface finding and AE releasing behaviour during fracture toughness test.     

Colour changes on curing light-activated anterior restorative resins

With many composite resins operators may notice a change in colour after light curing the restoration. Three types of specimen--a disc, a simulated Class III and a veneer--were made using a series of composite resins. Generally, resins became lighter or more translucent on irradiation. This was not only true for a range of resins from a single company but also the extent of the change was brand dependent. For most resins the opacity decreased with curing and most of this change occurred with a 20 seconds cure. The reflectance was approximately 50 per cent greater for resins placed over a white background than on a dark background for the thin disc specimens.     

Effect of human saliva on surface degradation of composite resins

Abstract – The amount of methacrylic acid produced by incubation of the dimethacrylate ester TEGDMA in human whole saliva was measured. The conversion rate of TEGDMA was determined in stimulated saliva from dental students and in unstimulated saliva from both dental students and patients. The differences in mean conversion rate measured in the three groups were not statistically significant ( P= 0.346). The mean conversion rate ± SD for all saliva samples was 4.54 ± 3.24 μmol MAA/L. h. The surface of BISGMA/TEGDMA-polymer specimens treated with porcine liver esterase in activities equivalent to those found in human saliva exhibited a lower Wallace microhardness than the surface of untreated specimens. Polymer specimens incubated in human saliva exhibited a similar reduction in the microhardness. The results demonstrated that enzymes in human saliva are capable of softening the surface of dimethaerylate polymers presumably by inducing a hydrolysis of methacrylate ester bonds. The mechanical removal of a surface layer softened by hydrolases will expose a new surface layer to enzymatic attack. The enzymatic softening may thus contribute to the in vivo wear of composite restorations.     

Color comparisons of composite resins of various shade designations

The purpose of this investigation was to compare the measured color of commercial composite resins of various shade designations (L, LG, LY, Y, U). Three samples of 11 composite resins were prepared according to manufacturers instructions. Diffuse reflectance measurements were made on a Pye Unicam dual-beam spectrophotometer equipped with an integrating sphere to provide CIE 1976 L^* a^* b^* values using both black and white backgrounds. Differences within shade designations were as follows: ΔL^* varied from 19.45 for Y to 4.75 for LG; Δa^* ranged from 7.46 for U to 3.26 for LG: and Δb^* ranged from 16.23 for Y to 4.73 for LY. Total color difference was greatest within the Y shade designation and least for the LY shade. Contrast ratios ranged from 0.811 for Command (LG) to 0.961 for Spectrafil (Y) and varied considerably within shade designations. Color differences between brands of identical shade designations were visually perceptiable in all groups. The results of this study indicate the need for improved standardization of shade designations for composite resins.     

Porosity in posterior composite resins

Abstract – The percent pore area and the mean pore size were measured in specimens made of nine brands of composite resin restorative materials. The overall percent porosity ranged from 0.01 to 4.5%. The specimens for the study were prepared in two ways; by condensation or by pressure. Most of the materials, including all those chemically activated, showed more porosity in the condensed than in the pressure specimens. Reversed results emerged for two of the materials, and for another two, the specimens were similar in this respect. The mean pore sizes were smaller in the condensed than in the pressure specimens. Neither mean pore size nor total amount of porosities could be correlated to the curing method of the materials.     

Colour stability of composite resins: A clinical comparison

Ninety three Class III cavities were prepared in 66 patients, and restored with one of three resin-based restorative materials; a hybrid self-cure material, a microfine self-cure material, or a microfine light-cure material. Standard sets of clinical colour transparencies were used to evaluate colour match with the surrounding tooth and marginal discoloration over five years. After five years, all materials had become slightly darker, the microfine self-cure material significantly more so than the light-cure material. There was no significant development of marginal discoloration.     

软启动照射模式对复合树脂聚合收缩的影响

目的:测定不同光照强度的软启动照射模式下同一种复合树脂的聚合收缩率.方法:采用粘接片(bonded discs)法测定卡瑞斯玛光固化复合树脂(体积38.5 mm3,C值0.47)在不同照射模式(高普40s、高普20 s、高渐进、高脉冲、中普、中渐进、中脉冲、台阶1、台阶2、台阶3)照射3min的聚合收缩率.结果:3种台阶照射模式的聚合体积收缩率均显著大于其他照射模式(P＜0.05);高普20 s模式的聚合体积收缩率显著大于高渐进、高脉冲模式(P＜0.05),但与高普40s相比无显著差异(P＞0.05);中普、中渐、中脉冲照射模式间体积收缩率两两相比均无显著差异(P＞0.05);台阶1照射模式的体积收缩率显著大于台阶2和台阶3(P＜0.05),而后两者无显著差异(P＞0.05).结论:光固化机固有的软启动和脉冲照射模式不能增加树脂的表面流动补偿收缩能力,应用光强更低的前期台阶照射模式则可显著增加树脂的表面流动补偿收缩能力.     

Correlation between fracture properties and clinical performance of composite resins in Class IV cavities

One hundred and two Class IV cavities were restored randomly with four composite resins. The restorations were assessed at six months, one year, two years and three years for surface chipping, bulk fracture and incisal wear. The data were correlated with various mechanical properties of the materials. A significant correlation was found between surface chipping/bulk fracture and fracture toughness (P = 0.002), elastic modulus (P = 0.006) and tensile strength (P = 0.045). There was a trend towards an association between incisal wear and both elastic modulus and inherent flaw size. Fracture toughness may be a useful indicator of the clinical performance of composites in Class IV cavities.