Sliding wear of 19 commercially available composites and compomers.

OBJECTIVES: The aim of this study was to determine the influence of particle size, particle material and morphology on the sliding wear of 19 light curing, commercially available composites (Durafill VS, Metafil CX, Heliomolar RO, Solitaire, Arabesk, Artglass, Charisma F, Pertac II, Charisma, Degufill Ultra, TPH Spectrum, Z100, Tetric classic, Pertac Hybrid, Estilux Hybrid, Dyract AP, Compoglass F, Compoglass and Hytac). METHODS: The materials were applied to an aluminum sample holder (7.5 mm diameter, 2 mm depth) in one layer and polymerized in a Dentacolor XS light curing unit for 180 s. The surface was ground flat (#1000) to remove any matrix rich surface layer. Then samples were stored in Ringer's solution for 24 h at 37 degrees C. Occlusal contact wear was simulated in a sliding wear tester (Munich Artificial Mouth). Eight specimens of each material were tested in a pin-on-block design with oscillating sliding of a Degussit antagonist (5 mm diameter) at a vertical load of 50 N. The horizontal excursion of the antagonist was 8 mm. Wear was quantified by a replica technique every 6000, 10,000, 30,000 and 50,000 cycles using a 3D-laser scanner. The materials were compared by their mean wear after 50,000 cycles. Comparisons of different composites and compomers were performed using analysis of variance and t-tests including the Bonferroni correction. RESULTS: The microfiller composites (Durafill VS, Metafil CX, Heliomolar RO) revealed the lowest, and the compomers (Dyract AP, Compoglass F, Compoglass and Hytac) showed the highest contact wear (p < 0.05). The wear of the hybrid composite (Estilux Hybrid) and the micro hybrid composites (Solitaire, Arabesk, Artglass, Charisma F, Pertac II, Charisma, Degufill Ultra, TPH Spectrum, Z100, Tetric classic, Pertac Hybrid) was higher than that of the microfiller composites (p < 0.05). The results showed additional significant differences within the three groups of composites. The coefficient of determination between loss of height and maximum particle size was r2 = 0.41. SIGNIFICANCE: Both particle size and morphology have a high influence on the wear properties concerning the two-body wear in the occlusal contact area.     

In vitro contact wear of dental composites.

OBJECTIVE: The aim of this study is to determine the in vitro two-body contact wear mechanisms of three medium filled composites and compare these with a highly filled composite previously investigated. MATERIALS AND METHODS: Three commercial dental composites with filler mass fraction loading of 75-76% were evaluated. Two of the composites contained Ba-B-Al-silicate glass fillers and fumed silica with different particle sizes and distributions. One of these composites contained a fairly uniform distribution of filler particles ranging in size from 1 to 5 microm, whereas the particle size distribution in the second composite was bimodal consisting of small (less than 1 microm) and large (about 10 microm) particles. The third composite contained Ba-Al-silicate glass and silica with a filler particle size of approximately 1 microm. The composite disks were tested for wear against harder alumina counterfaces. Wear tests were conducted in distilled water using a pin-on-disk tribometer under conditions that represented typical oral conditions (sliding speed of 2.5 mm/s and contact loads ranging from 1 to 20 N). The wear tracks were analyzed by scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy to elucidate the wear mechanisms. The chemical composition of the water solution collected after the tests was determined using an inductively coupled plasma-mass spectrometer (ICP-MS) to detect possible chemical changes, e.g. dissolution of trace elements due to submersion or wear. The wear results were compared with those reported in an earlier study on a highly filled composite containing predominately alumino-silicate glass fillers and alumina at a filler loading of 92%. RESULTS: The differences in two-body wear rates between the three medium filled composites were not statistically significant (p<0.05) indicating that the variations in filler particle size and slight differences in chemical composition of the glass fillers do not affect the in vitro wear rates of these composites. Wear rates of these medium filled composites, however, were significantly lower than the highly filled composite (p<0.05). SEM, FTIR and ICP-MS analyses suggested that wear in the medium filled composites occurs by a complex set of processes involving tribochemical reactions between filler particles and water, formation of surface films containing a mixture of filler fragments and reaction products, and film delamination, as well as dissolution of the reaction products. SIGNIFICANCE: This study reveals that subtle changes in the filler particle size and small differences in filler composition do not significantly affect the two-body wear behavior of medium filled composites. However, the chemistry of filler particles plays an important role in altering the wear performance of composites when significant changes are made in the chemical composition of the fillers and when the filler loading is increased.     

Influence of filler loading on the two-body wear of a dental composite

The purpose of the study was to explore the fundamental wear behaviour of a dental composite with different filler loadings under two-body wear conditions. The parent resin and filler components were mixed according to different weight ratios to produce experimental composites with filler loadings ranging from 20 to 87.5% by weight. A two-body wear test was conducted on the experimental composites using a wear-testing machine. The machine was designed to simulate the impact of the direct cyclic masticatory loading that occurs in the occlusal contact area in vivo. The results showed that there was little increase in the rate of wear with filler loadings below 60 wt%, but a sharp increase between 80 and 87.5 wt% in filler loading. Wide striations and bulk loss of material were apparent on the wear surfaces at higher filler loadings. Coefficients of friction increased with filler loading and followed the increase in rate of wear loss closely. It was concluded that, under two-body wear conditions, addition of high levels of filler particles into the resin matrix could reduce the wear resistance of dental composites. This finding may help when designing future dental composites for use in particular clinical settings.     

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   

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.     

Chewing pressure vs. wear of composites and opposing enamel cusps.

The effects of various chewing pressures on the wear of composites and enamel were assessed in vitro. Standardized composite discs (8 mm in diameter, 2 mm in height) were made of a fine-particle hybrid (FPH), a coarse-particle hybrid (CPH), and a homogeneous microfilled composite (HMC). The composite specimens were chemically degraded by immersion in 75% ethanol for 24 h, brushed for 30 min, and then thermocycled 300 times (5-55-5 degrees C) while being occlusally loaded 120,000 times at 1.7 Hz, with chewing forces of 25, 50, 75, and 100 N. Standardized human enamel cusps with a uniform contact area of 0.384 mm2 served as antagonists in the chewing machine. Wear of the composites and enamel cusps, their combined wear, and the increase of the enamel contact surfaces were quantified. An increase in chewing pressure significantly enhanced the wear of both composite and enamel in all groups except for the antagonists opposing a HMC. The FPH was most wear-resistant to in vitro chewing pressures in the range of 6.58 to 19.74 MN/m2, the CPH at 26.32 MN/m2, while the HMC was the most enamel-friendly of the three composites tested. The FPH composite had the least disintegration in the occlusal contact area. The ranking of the composites generally varied at the different chewing pressures with respect to the three types of quantified wear--that is, composite wear, enamel wear, and total wear.     

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?μm. 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?μm filler diameter) wore the least and the coarsest composites (10?μm 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.     

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.     

Comparison of two-and three-body wear of glass-ionomers and composites

The two-body and three-body wear of glass-ionomers (GIC), visible light cured glass-ionomers (VLC-GIC), and composites were compared. The wear simulations were performed for the two-body wear in an artificial mouth and for the three-body wear with the so-called ACTA machine. The tested materials were different conventional glass-ionomers. light cured glass-ionomers. composites, and amalgam. The wear rates of 8 specimens of each material for the two-body and 16 for the three-body wear test were compared. After 10⁵ cycles with each testing device, the wear shapes were measured. All measurements were related to the wear rate of amalgam. For the two-body wear method, the worn materials were qualitatively judged by scanning electron microscopy. The two different wear testing methods lead to similar results with slight differences in ranking. Amalgam showed the lowest wear rates with both methods. Photac® Fil, a newly developed VLC-GIC. showed dramatically lower wear resistance than composites and conventional GIC with both methods. Further investigations are necessary to identify the material-specific parameters influencing the wear behaviour of a material in relation to different wear testing methods.     

Comparative wear ranking of dental restoratives with the BIOMAT wear simulator. Part II. An SEM evaluation

The qualitative wear of amalgam alloys and composite resins opposing cast chromium alloys after impact-sliding wear simulation with the BIOMAT wear simulator was assessed. An impact stress of 28 MPa was adopted to allow for stresses generated during parafunctional activities. The worn specimens were examined using SEM at both impact sites and region of sliding wear. For amalgam alloys, ranking from the smoothest to the roughest surface under SEM observation was as follows: unicompositional alloy>admixed alloy>gallium alloy. For composite resins the ranking was: microfilled composite>small particle composite>hybrid composite. The qualitative SEM assessment results were consistent with our earlier volumetric wear results and supports the hypothesis that surface microstructure affects wear. Composite selection for teeth opposing cast chrome prostheses should be done with caution and knowledge of the composition of the material as three-body wear may occur.     

In vitro vibrational wear under small displacements of dental materials opposed to annealed chromium-steel counterbodies

In vitro vibrational wear tests were performed on 17 composites and one amalgam with human enamel as a reference. The specimens were fixed on a computer-controlled X-Y translation table that generated an oscillatory movement under small displacements. The dental material specimens were in permanent contact with an annealed chromium-steel counterbody. The tests were performed in ambient air of normal humidity at room temperature under non-lubricated sliding conditions. The friction between the counterbody and each of the various materials was measured on-line. After completion of the tests, the wear volumes were determined by contactless profilometry, and the wear pattern was studied with SEM. The simple vibrational test used in this study allowed a fast classification of different dental materials in terms of the relative wear on either the specimen or the counterbody material. The ratio of the wear volume of the counterbody versus the wear volume of the dental material specimen was used to accurately classify the materials according to their in vitro wear behavior, especially when this ratio was related to the total wear volume of the dental material specimen and the counterbody. From an analysis of the wear behavior of the both contacting materials, it became obvious that neither the wear of the dental materials nor of the chromium-steel counterbody appears to correlate with either the inorganic filler hardness, the intrinsic surface roughness, the surface hardness or the Young's modulus of the dental materials.     

Wear model simulating clinical abrasion on composite filling materials

The aim of this study was to establish a wear model for testing composite filling materials with abrasion properties closer to a clinical situation. In addition, the model was used to evaluate the effect of filler volume and particle size on surface roughness and wear resistance. Each incisor tooth was prepared with nine identical standardized cavities with respect to depth, diameter, and angle. Generic composite of 3 different filler volumes and 3 different particle sizes held together with the same resin were randomly filled in respective cavities. A multidirectional wet-grinder with molar cusps as antagonist wore the surface of the incisors containing the composite fillings in a bath of human saliva at a constant temperature of 37°C. The present study suggests that the most wear resistant filling materials should consist of medium filling content (75%) and that particles size is not as critical as earlier reported.     

Attritional wear and abrasive surface alterations of composite resin materials in vitro

OBJECTIVES: A laboratory study was performed with 232 specimens and 72 human enamel, 24 gold, 24 ceramic and 12 composite antagonists in 22 groups to test attritional and abrasive wear behavior of composite materials compared to wear behavior of human enamel. METHODS: Belleglass HP, Concept Inlay/Onlay, Targis and Targis Upgrade 99 composite resin for lab-made restorations was tested as well as Tetric Ceram and FHC Merz light as resins for direct restorations. Natural human enamel specimens served as control. All specimens were subjected to long-term thermo-mechanical loading in a computer-controlled masticator, chemical degradation and toothbrush/toothpaste abrasion. Wear of specimen in occlusal contact area (OCA), contact-free occlusal area and wear of natural enamel cusps as well as antagonists made of gold, ceramic and composite in identical form was measured after 120,000, 240,000, 640,000 and 1200,000 load cycles. A qualitative SEM analysis was performed to support quantitative data. RESULTS: Belleglass HP and Targis Upgrade 99 restorative materials showed wear resistance comparable to human enamel when loaded with enamel cusps. Wear of Targis versus composite and gold antagonists was significantly higher (p<0.0001). Analysis of surface alterations showed hygroscopic expansion in all composite resins during the test. CONCLUSIONS: As a consequence of this study, necessity to further improve physical properties of composites for long lasting restorations was obvious. Beside of attritional wear in OCA, attention must be given to stable filler-matrix interfaces and prevention of water sorption.     

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.     

Development of metal-resin composite restorative material. Part 3. Flexural properties and condensability of metal-resin composite using Ag-Sn irregular particles

Powder-liquid type metal-resin composites, using Ag-Sn irregular particles as the filler, 4-META as coupling agent and UDMA + TEGDMA as resin matrix, were experimentally prepared under 9 different conditions (three different particle sizes and three different filler contents). The flexural strength and flexural modulus were measured. Three different irregular particle size MRCs without redox-initiator at 94% filler content, as well as amalgam, conventional hybrid composite and Ag-Sn spherical particle MRC were evaluated for condensability. The flexural strength of the Ag-Sn irregular particle MRC was significantly influenced by both the filler particle size and filler contents (p < 0.01). It increased when either the filler content increased or the particles size decreased. The highest flexural strength (97.6 MPa) was obtained from the condition of particles size < 20 microns and 94% filler content. The flexural modulus was significantly influenced by filler content and it increased with increasing filler content. The condensability of the Ag-Sn irregular particle MRC was lower than that of amalgam but much higher than presently available conventional composites and spherical particle MRC.     

Shear punch strength and flexural strength of model composites with varying filler volume fraction, particle size and silanation.

OBJECTIVE: The effect of filler volume fraction, particle size and silanation on shear punch strength, flexural strength and flexural modulus of model composites has been evaluated. METHODS: Hybrid type glass filled (0-65.2 vol%), composites some without filler silanation (30.7-51.0 vol%) and microfilled type (0-13.0 vol%) resin matrix (UDMA and EGDMA) composites (Shofu Inc., Japan) were used in the study. For the shear punch test, 10 disc specimens, 0.5mm thick and 9 mm diameter, were prepared for each composite and tested with a 3.2mm dia punch at 1.0mm/min. Flexural strength (n=10) was measured by the method outlined in ISO 4049. Data were analyzed using ANOVA and Fisher's multiple-range test. RESULTS: Shear punch strength and flexural strength increased with increasing filler content up to 52.2% for hybrid composites and between 0 and 9.1% for microfilled composites. Shear punch strength and flexural strength decreased with increasing filler volume fraction for un-silanated composites. Flexural modulus for all materials increased with increasing filler volume fraction. Hybrid composites with silanated fillers have significantly higher values of flexural strength, flexural modulus and shear punch strength than equivalent materials with un-silanated fillers. SIGNIFICANCE: The results showed that filler silanation is an important factor for determining material strength. Additions of small quantities of microfillers appeared to have a greater effect on shear strength than equivalent amounts of hybrid filler. The shear punch test may prove beneficial for routine testing of composites as specimen preparation was simple, specimen quality was easy to maintain and the results are meaningful.     

Wear and mechanical properties of composite resins consisting of different filler particles

To investigate the effects of different fillers and their contents on the wear of composite resins, four composites (CS: non-porous spherical silica, AS: porous spherical silica, AZ: porous spherical zirconium silicate, and IS: non-porous irregular-shaped silica) were experimentally prepared using different fillers (CS, AZ, AS and IS). Simulated occlusal wear and toothbrush wear were evaluated for these composites and their worn surfaces were observed. The mechanical properties (flexural strength, elastic modulus and hardness) of these composites were determined to examine the relationships between wear and these mechanical properties. CS showed the highest occlusal wear, but the lowest toothbrush wear among four composites. AS and AZ had lower occlusal wear than CS and IS, while their toothbrush wear was higher than CS and close to that of IS. All composites showed increase in the occlusal wear as filler content increased. CS and IS showed decrease in the toothbrush wear as the filler content increased, whereas AS and AZ did not. The occlusal wear surfaces of CS and IS had concavities, while those of AZ and AS were relatively smooth with flattened filler. The toothbrush wear surfaces of CS and IS revealed the extrusion of filler from resin matrix, whereas those of AZ and AS were smooth with flattened filler. The toothbrush wear of CS and IS decreased as the mechanical properties increased, whereas those of AS and AZ did not. The occlusal wear of all composites increased as the mechanical properties increased, which would not reflect effects of these mechanical properties.     

Respirability, microstructure and filler content of composite dusts

Dusts were generated from five composites, with two different shades each. Between 54 and 70 mass percent of the dust (60 to 92% of the particles) collected was respirable. The average particle size collected was 3.97 microns by mass (0.9 microns by number of particles). Between 14 and 22% of the dust generated was respirable. Filler content of the respirable dust particles was within 3 mass percent of the amount of filler in each cured composite. Powder x-ray diffraction revealed that respirable dust particles collected from composites reported to contain crystalline silica fillers contain the same crystalline silica. The results indicate that improperly protected dental personnel who are regularly exposed to composite dusts generated during high-speed finishing of composites containing quartz filler may be at risk for developing silicosis. Dental personnel should wear masks specifically designed to filter respirable silica when finishing composite restorations with high-speed instrumentation.     

Effects of particle size of silica filler on polymerization conversion in a light-curing resin composite

Objectives

The effect of visible light passing through a resin composite with different particle sizes of spherical silica filler on the curing depth and Knoop hardness of the resin composite was examined. The null hypotheses tested were that the particle size of silica filler has no effect on (1) the transmitted amount of visible light passing through the resin composite, (2) the curing depth of the resin composite, and (3) the ratio of the Knoop hardness of the hardened resin composite.

Methods

A series of different experimental resin composite pastes with different particle sizes of silica filler were prepared. The amount of visible light passing through each of the experimental resin pastes during the hardening process was determined. The curing depth and Knoop hardness of the resin composites were measured. Further, to characterize the polymerization conversion, the ratio of the Knoop hardness of the bottom surface against the irradiated surface of the hardened resin composites was determined.

Results

Increases in the particle size of the silica filler resulted in decreases in the transmitted amount of visible light, curing depth, and ratio of the Knoop hardness of the resin composite. The rate of polymerization conversion of the resin composite occurring deep within the cavity was found to be less than the rate of polymerization conversion occurring at the upper surface.

Significance

To increase the rate of polymerization conversion deep within the resin composite, it is important to reduce the particle size of the silica filler.