Effects of filler size, water, and alcohol on hardness and laboratory wear of dental composites

Three UEDMA/TEGDMA (50:50 by weight) based dental composites were made, each with filler loadings of 53 vol.%. The three composites contained silane-treated filler particles with average particle diameters of 1.5, 3.0, or 10.0 microm. Twelve specimens per composite were mounted on wear wheels and run through 200,000 cycles in an ACTA wear machine. Six of these specimens per material were worn in slurries consisting of 30 g ground Millet seed shells and 120 g ground rice mixed with 275 mL water. The remaining six specimens were worn in similar 25% ethanol-water slurries. The composite wear profiles were recorded with a profilometer and used to calculate the wear. Hardness values of the composites were also measured both before and after storage for 2 weeks in either water or in a 25% ethanol water solution. The wear and hardness values from the measurements were analyzed using ANOVA. The wear analysis showed that the finer composites (1.5 microm filler diameter) wore the least and the coarsest composites (10 microm filler diameter) the most. The wear was significantly higher in the ethanol water slurry than in the water slurry. The hardness value of the coarsest composite decreased more than the finest composite during storage in water or 25% ethanol water. The hardness decrease was most pronounced in the alcohol solution.     

Correlation of resin viscosity and monomer conversion to filler particle size in dental composites

Objective

The viscosity of dental resin composites is important in their formulation and clinical use; it depends on the filler particle size and loading. We intend to study the viscosity and conversion of composites made of low dispersity spherical silica fillers.

Effect of filler size on wear resistance of resin cement

The purpose of this study was to evaluate the effect of filler size on the wear of resin cements. Materials tested included four experimental dual-cure resin cements (Kuraray) consisting of different-sized filler particles. A rectangular box cavity was prepared on the flattened occlusal surface of extracted human molars. Ceramic inlays for the cavities were fabricated using the Cerec 2 system. The Cerec inlays were cemented with the respective cements and adhesive systems according to the manufacturer's directions. The restored surface was finished by wet-grinding with an 800-grit silicon carbide paper. Six specimens were prepared for each resin cement. Half of the specimens were subjected to a three-body wear test for 200 000 cycles, and the others were subjected to a toothbrush abrasion test for 30 000 cycles. The worn surface of each restoration was scanned by a profilometer (Surfcom 475 A) at eight different points for each restoration. The wear value was determined by measuring the vertical gap depth on the profilometric tracings. The data were statistically analyzed by one-way analysis of variance (ANOVA) and Scheffe's test. The results showed that, with increase of filler size, the wear value decreased in the toothbrush test and increased in the three-body wear test. The cement with 0.04-μm filler exhibited the lowest wear value among the materials in the three-body wear test, and the same wear value as the cement with 0.97-μm filler in the toothbrush test. Based upon the results of this study, it is concluded that the wear of resin cements was affected by the filler size as well as the mode of wear test. Received: September 27, 2000 / Accepted: June 12, 2001     

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.     

Scratch hardness and chipping of dental ceramics under different environments

OBJECTIVE: The goal of this program was to identify promising environments that could efficiently minimize machining-induced damage of dental materials. METHODS: Single point abrasion (SPA) scratch testing was used on five materials to determine the scratch hardness and amount of edge chipping as functions of chemical environment, including air, water, saline and glycerol solutions. Limited testing was also done under additional environments expected to promote chemomachining effects via crack growth promotion or debris removal. A conical diamond indenter and a conventional tungsten carbide machining tool were used in the scratch tests. One-way ANOVA analysis was used to determine statistical differences among the variables. RESULTS: There was a consistent trend across materials that the water and saline yielded the lowest values of scratch hardness, air the next lowest, and the tests performed in glycerol yielded the highest hardness values. The measured hardness values using the conical diamond tool in the glycerol environments were about twice the hardness values measured under water and saline solutions. Environmental effects on chipping were minimal, but a linear relationship between load and per cent chipping was determined for the WC tool within the 10-50 N test range. The choice of scratch tool strongly affected scratch hardness and chipping tendency. SIGNIFICANCE: The chemical environment had an effect on machining characteristics, but the effects were more dependent on tool interactions rather than material specific properties. As a result, it may not be possible to utilize a particular single environment to substantially improve the damage response of dental materials to machining operations. Improvements in damage resistance can be environmentally obtained, but only for shallow cuts (finishing operations).     

Theoretical prediction of dental composites yield stress and flexural modulus based on filler volume ratio

ObjectiveA costly advantageous approach in composites development process is to limit experimental tests by predicting mechanical properties with respect to their filler ratio. Models exist for other fields than dentistry. They have been compared to 3-point bending test experimental results for yield stress, flexural modulus and flexural strength.MethodsFive formulations of the same experimental material were made. They were composed of an organic matrix and different ratios of silanated barium glass particles. The samples were stored in distilled water for 24 h at 37 °C prior to the 3-point bending test. The Turcsányi model for yield stress was notably investigated, and SEM was used to complete data analysis.ResultsThe yield stress showed reproducible results and a good fit with Turcsányi model with respect to filler ratio. The flexural modulus data are not scattered but did not fit with the existing models. No trend could emerge for flexural strength and strain because of scattering; these properties are more unpredictable. The SEM observations of fracture areas confirm a good matrix-filler interface quality.SignificanceSEM pictures validated the numerical parameter obtained from Turcsányi model. The latter therefore seems to be applicable to dental composites. Firstly, it enables to predict the evolution of the material yield stress without testing all filler ratios. Secondly, this model provides a good way to get micro-information on the matrix-filler interface from macroscopic tests. The discrepancy between flexural modulus results and theory highlighted the necessity to include an “interface quality” parameter in accurate predictive models.     

Effect of novel filler particles on the mechanical and wear properties of dental composites.

OBJECTIVES: The purpose of this study was to investigate the method of producing pre-polymerized fused-fiber filler modified composite (PP-FFMC) particles and the effectiveness of incorporating these novel filler particles into dental composites. METHODS: Fused-fiber filler (FFF) blocks were impregnated with composite by two different methods. Three-point flexure tests were utilized to determine which was more effective. In order to assess the effect of the addition of PP-FFMC particles, two Bis-GMA/TEGDMA based conventional composite compositions were utilized as baselines, to which the novel particles were added. Mechanical and wear tests were performed to determine the fracture toughness, biaxial flexure strength, and in vitro wear of the materials. RESULTS: Mechanical testing showed that the addition of PP-FFMC particles decreased the strength and toughness of the conventional composites. Wear tests indicated that addition of the same particles improved the wear behavior of the conventional composites. SEM analysis of the fracture surfaces indicated that the PP-FFMC particles were incorporated without creating porosity, and that fracture was transgranular through the reinforcing particles. Microscopic flaws observed in the novel particles are the likely explanation for the observed strength and toughness values. SIGNIFICANCE:The results indicate that PP-FFMC particles have the potential to improve the wear properties of dental composites, however, they adversely affect the fracture behavior. Existing processing techniques for these particles, which introduce imperfections, limit their current usefulness.     

填料含量和尺寸对复合树脂透明度的影响

目的: 研究填料大小和含量对复合树脂透明度的影响。方法: 每种颗粒大小的填料均以60%、70%、75%和80%的质量分数与基质混合,固化后制备成直径10 mm、厚度1 mm的试件,测定各组试件在标准白板(W)和金属色底板(B)上的色度值。测色系统使用CIELab系统,透明度（TP）根据公式TP=[(L*B-L*W)2+(a*B-a*W)2+(b*B-b*W)2]1/2计算。方差分析颗粒大小和含量对试件透明度的影响,采用SPSS 20.0软件包对均数进行单因素方差分析和HSD检验。结果: 不同直径填料间透明度无显著差异;当填料含量增加时,树脂试件透明度下降。结论: 当填料直径在0.7~1.5 μm范围内变化时,填料含量越高,复合树脂透明度越低。     

Influence of artificial saliva on abrasive wear and microhardness of dental composites filled with nanoparticles

OBJECTIVES: The aim of this study is to compare the wear resistance and hardness of two dental nanohybrid composites and to evaluate the influence of artificial saliva storage on those properties. METHODS: Specimens were made from two commercial nanohybrid dental composites (Esthet-X((R))-Dentsply and Filtek Supreme((R))-3M). Abrasion tests were carried out in a ball-cratering machine (three body abrasion) and microscopic analysis of the wear surfaces was made using optical and scanning electron microscopy; hardness was quantified by Vickers hardness test. Those tests were repeated on specimens stored in artificial saliva. RESULTS: Results show that the wear rate of the studied materials is within 10(-7)mm(3)/Nmm range, one of the composites presenting wear rate twice as large as the other. After storage in artificial saliva, the wear resistance increases for both materials. Microhardness of the composites is around 52 and 64HV, Esthet-X((R)) presents higher hardness values than Filtek Supreme((R)). After storage in artificial saliva, the microhardness of both materials decreases. Data were analyzed using ANOVA test, p相似文献   

The effect of a leucite-containing ceramic filler on the abrasive wear of dental composites.

OBJECTIVES: The aim of this study was to evaluate abrasive wear of a dental composite based on a leucite-containing (KAlSi2O2 ceramic filler, and to compare it with the wear of a composite based on commonly used aluminum barium silicate glass filler. METHODS: IPS Empress (Ivoclar-Vivadent) ingots were ball milled, passed through an 800 mesh (ASTM) sieve, and used as the leucite ceramic filler. Experimental composites were prepared by mixing the silane-treated fillers with the resin monomers. The resin consisted of 70 wt% Bis-GMA and 30 wt% TEGDMA containing camphorquinone and DMAEMA as the photoinitiator system. Glass-based composites were also prepared using silane-treated aluminum barium silicate glass fillers and the same resin system. TetricCeram, a commercially available dental composite, was used as control. Spherical specimens of the composites were then prepared and kept in water for 2 weeks to reach equilibrium with water. An abrasive wear test was performed using a device designed in our laboratory and weight loss of the specimens was measured as an abrasion parameter after each 50 h. SEMs were taken from worn and fractured surfaces. Degree-of-conversion of the composites was measured using FTIR spectroscopy. Vickers surface microhardness, flexural strength, and flexural modulus of the composites were also measured. The data were analyzed and compared using ANOVA and Tukey HSD tests (significance level=0.05). RESULTS: The results showed that there were significant differences among the abrasive wear of the composites (p<0.05). The ranking from least to most was as: leucite-based composite相似文献   

SiO2粒径分布对牙科复合树脂性能影响

目的研究SiO2粒径分布对牙科复合树脂无机填料的填充量和物理机械性能的影响。方法采用经硅烷表面修饰的气相法纳米SiO2(NS)和微米SiO2(MS),通过调整两者相对质量比,与双酚A双甲氧基缩水甘油酯牙科树脂单体共混,制备了一系列牙科复合树脂M50N20,M55N15,M58N12,M60N10,M63N07,研究了不同SiO2粒径分布对无机填料的填充量,以及复合树脂维氏硬度、三点弯曲强度和断面形貌的影响。结果复合树脂中填料的填充量取决于无机填料的分布及比表面大小,当MS/NS=58/12时,复合树脂的无机填料填充量达到84wt%。M58N12表现出最高的三点弯曲强度(153.2MPa)以及维氏硬度(102.3MPa)。复合树脂断面的SEM形貌分析表明,纳米SiO2与复合树脂基体有较好的粘合作用。结论复合树脂中SiO2粒径分布对物理机械性能以及无机填料的填充量有较显著的影响。     

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.     

Effect of filler fraction and filler surface treatment on wear of microfilled composites.

OBJECTIVES: The aim of this study was to determine the effect of filler content and surface treatment on the wear of microfilled composites. METHODS: Four microfilled composites with different filler contents (A=20, B=25, C=30, and D=35 vol.%) were made with a light-cured resin (Bis-GMA/UDMA/TEGDMA). The surface treatment of the colloidal silica in each varied: F=functional silane, NF=non-functional silane, U=untreated. Silux Plus served as a control. Specimens were made in steel molds and cured in a light curing unit Triad II (40s/side). Abrasion and attrition wear were evaluated in vitro in a wear tester (OHSU oral wear simulator) with an abrasive slurry (poppy seeds + PMMA) and a human enamel antagonist. The average of five specimens was computed and compared using a ANOVA/Tukey's test at P < or = 0.05. The surface of the wear patterns and the distribution of filler particles were examined using a scanning electron microscope and digital imaging. RESULTS: As filler volume increased, wear was reduced regardless of filler treatment. Amounts of wear for specimens C and D were significantly lower than specimens A and B. Composites with functional silane treated microfiller (Group F) produced significantly less wear than those with non-functional microfiller (Group NF) at 30 and 35 vol.%, and less than the untreated microfiller (Group U) at 30 vol.%. Scanning electron microscopy of specimens of group NF showed large filler agglomerates (size > 1 microm) in the resin matrix, while specimens of group F and U showed fewer agglomerates. Digital imaging analysis revealed small filler clusters (size < or = 1 microm) in the resin matrix of all specimens. SIGNIFICANCE: Wear resistance of microfilled composites is enhanced by higher filler volumes irrespective of surface treatment, but good filler/matrix adhesion is needed to minimize wear.     

Long-term elution of monomers from resin-based dental composites

Objective

To bridge the gap between the current alarming literature on resin-based dental materials and the limited clinical observations, more precise knowledge on the actual quantity of released compounds should be acquired. The objective of this study was to quantify the long-term elution of various compounds from resin-based dental composites during one year.

A new method for predicting the maximum filler loading of dental resin composites based on DEM simulations and experiments

ObjectiveThe inorganic fillers in dental resin composites can enhance their mechanical properties and reduce polymerization shrinkage. When the usage amount of inorganic fillers is closed to maximum filler loading (MFL), the composites will usually achieve optimal performances. This study aims to develop a method that can predict the MFL of dental resin composites for the optimization of filler formulations.MethodsA method based on discrete element method (DEM) simulations and experiments was firstly developed to predict the MFL of spherical silica particles for single-level and multi-level filling.ResultsThe results indicate that the presence of modifier can increase the MFL, and the MFL increment can be exponentially changed with the content of the modifier. Compared with the single-level filling, the addition of secondary fillers is beneficial to increase the MFL, and the increment can be affected by the particle size and size ratio. The prediction results show a good agreement with the experiment results.SignificanceThe accuracy of prediction results indicates a great potential of DEM simulations as a numerical experimental method in studying the MFL, and provides an effective method for the optimization of filler formulations.     

Influence of silanization and filler fraction on aged dental composites

The effect of silanization and filler fraction on the mechanical properties of aged dental composites was investigated. Experimental composites (75/25 Bis-GMA/TEGDMA resin reinforced with 0, 12.6, 30.0, and 56.5 vol% 8 microm silanized/unsilanized BaSiO6) were fabricated into 4.7 mm diameter x 2.2 mm thick discs and 3.5 mm diameter x 7.3 mm thick discs for diametral tensile and compressive tests, respectively. The effect of immersion in 75% ethanol at 37 degrees C for 0-30 days on the diametral tensile strength (DTS) and compressive strength (CS) of the samples was evaluated and analysed by ANOVA and Tukey LSD test. The fracture interface between filler and resin matrix was then examined by scanning electron microscope. Results and subsequent statistical evidence from DTS (18.6+/-7.6 MPa, silanized versus 11.7+/-2.6 MPa, unsilanized) and CS (85.1+/-29.7 MPa, silanized versus 56.0+/-11.3 MPa, unsilanized) strongly implies that silanization may greatly enhance the mechanical properties of the resin composites. Furthermore, it also shows that both DTS and CS increased proportionally as the filler fraction of the composites increased. However, in the unsilanized groups, DTS decreased (up to 40%) as the filler fraction increased, and CS showed no relevance to the filler fraction at all. As for the influence of aging, it was found that both DTS and CS showed a significant decrease after immersion in 75% ethanol, and silanization heavily correlated with the filler fraction of aged-resin composites. Microscopic examination of the fractured samples showed that failure primarily occurred within the resin matrix per se for silanized composites and adjacent to the filler particles for unsilanized composites. All the evidence points to the conclusion that mechanical properties of aged-resin composites can be greatly influenced by silanization and the filler fraction.     

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.     

Effects of bolus size and hardness on within-subject variability of chewing cycle kinematics

This study analysed how bolus hardness and size affect within-subject variability of chewing cycle kinematics. Two independent prospective studies were performed; both tracked chin movements using an optoelectronic recording system. Computer programs identified each subject's ten most representative cycles, and multilevel modelling procedures were used to estimate variances. One study evaluated 38 subjects who chewed 1, 2, 4 or 8 g of gum presented in random order. The second study evaluated 26 subjects who chewed approximately 2.5 g of harder (670 g) or softer (440 g) gum, also presented in random order. In terms of bolus size, the 2g and 1g boluses produced the least and greatest relative within-subject variability, respectively; the largest differences were found for cycle duration and excursions. Within-subject variability when chewing the harder gum was consistently greater than when chewing the softer gum, except for lateral movement towards the balancing side. Because bolus hardness and bolus size influence within-subject variability differently, they must be taken into consideration when designing experiments to study masticatory kinematics. We conclude that a 2g bolus of soft gum should be used in studies of chewing cycle kinematics in order to reduce within-subject variability and increase statistical power.     

Effect of filler content and size on properties of composites

Two series of dental composites, along with the unfilled resin matrix, were examined to determine the effects of filler level and size on selected properties. Both series were prepared by incorporating a silanated barium borosilicate filler into a visible-light-activated polyphenylene polymethacrylate resin matrix. One series had a filler particle size of 2 microns, with filler levels of 20, 40, 45, 50, and 53% (vol). The second series contained a 15-microns filler in amounts of 20, 40, 50, 60, and 65% (vol). Tests conducted included: depth of cure as evaluated by hardness, water sorption, compressive strength, stress-strain behavior under slow compression, toothbrush abrasion, and wear by hydroxyapatite. Analysis of the data indicated that increased filler levels resulted in increased hardness, compressive strength and stiffness, and decreased water sorption. Also, there was a slight trend toward improved depth of cure. Incorporation of the 2-microns filler decreased the abrasion resistance of the resins to toothbrushing as compared with the unfilled resin, while addition of the 15-microns filler improved resistance. All filled resins exhibited a significant improvement in resistance to wear by hydroxyapatite as compared with the unfilled resin. There was a trend for increased wear with increased filler level. The particle size of the filler appeared to have a moderate influence on the properties. When compared with 15-microns filled resins of the same filler levels, the 2-micron filled series appeared to have inferior properties in terms of depth of cure, compressive strength, water sorption, and resistance to toothbrush abrasion. Properties which were less affected by particle size were hardness, stiffness, and wear resistance to hydroxyapatite.