Oral fluoride levels 1 h after use of a sodium fluoride rinse: effect of sodium lauryl sulfate.

Increasing the concentration of free fluoride in oral fluids is an important goal in the use of topical fluoride agents. Although sodium lauryl sulfate (SLS) is a common dentifrice ingredient, the influence of this ion on plaque fluid and salivary fluid fluoride has not been examined. The purpose of this study was to investigate the effect of SLS on these parameters and to examine the effect of this ion on total (or whole) plaque fluoride, an important source of plaque fluid fluoride after a sufficient interval following fluoride administration, and on total salivary fluoride, a parameter often used as a surrogate measure of salivary fluid fluoride. Ten subjects accumulated plaque for 48 h before rinsing with a 12 mmol/l NaF (228 µg/g F) rinse containing or not containing 0.5% (w/w) SLS. SLS had no statistically significant effect on total plaque and total saliva fluoride but significantly increased salivary fluid and plaque fluid fluoride (by 147 and 205%, respectively). These results suggest that the nonfluoride components of topical agents can be manipulated to improve the fluoride release characteristics from oral fluoride reservoirs and that statistically significant change may be observed in plaque fluid and salivary fluid fluoride concentrations that may not be observed in total plaque and total saliva fluoride concentrations.

Evaluation of three-dimensional biofilms on antibacterial bonding agents containing novel quaternary ammonium methacrylates.

Antibacterial adhesives are promising to inhibit biofilms and secondary caries. The objectives of this study were to synthesize and incorporate quaternary ammonium methacrylates into adhesives, and investigate the alkyl chain length effects on three-dimensional biofilms adherent on adhesives for the first time. Six quaternary ammonium methacrylates with chain lengths of 3, 6, 9, 12, 16 and 18 were synthesized and incorporated into Scotchbond Multi-Purpose. Streptococcus mutans bacteria were cultured on resin to form biofilms. Confocal laser scanning microscopy was used to measure biofilm thickness, live/dead volumes and live-bacteria percentage vs. distance from resin surface. Biofilm thickness was the greatest for Scotchbond control; it decreased with increasing chain length, reaching a minimum at chain length 16. Live-biofilm volume had a similar trend. Dead-biofilm volume increased with increasing chain length. The adhesive with chain length 9 had 37% live bacteria near resin surface, but close to 100% live bacteria in the biofilm top section. For chain length 16, there were nearly 0% live bacteria throughout the three-dimensional biofilm. In conclusion, strong antibacterial activity was achieved by adding quaternary ammonium into adhesive, with biofilm thickness and live-biofilm volume decreasing as chain length was increased from 3 to 16. Antibacterial adhesives typically only inhibited bacteria close to its surface; however, adhesive with chain length 16 had mostly dead bacteria in the entire three-dimensional biofilm. Antibacterial adhesive with chain length 16 is promising to inhibit biofilms at the margins and combat secondary caries.

Analyses of a cantilever-beam based instrument for evaluating the development of polymerization stresses.

OBJECTIVE: This investigation was to generate (1) guidelines for designing a tensometer that satisfies the necessary accuracy and sensitivity requirements for measuring polymerization stress (PS), and (2) a formula for calculating PS. Polymerization stress remains one of the most critical properties of polymeric dental materials, yet methods that can accurately quantify PS have been limited in part due to the complexity of polymerization, and in part due to the instrumentation itself. METHOD: In this study, we performed analytical and finite element analyses on a cantilever-beam based tensometer that is used to evaluate shrinkage stresses during the polymerization of dental restorative composites. RESULTS: The PS generated by a commercial dental composite determined using our new tensometer agrees with the predicted trend when the beam length and/or specimen height is varied. SIGNIFICANCE: This work demonstrates the importance of beam dimension and component relative rigidity to the accuracy of PS evaluation. An analytical solution is also derived for the vertical beam deflection, which can be used for any combination of bending and shearing to properly calculate the PS. In addition, an easy-to-conduct calibration procedure is provided that is desirable for periodic tensometer recalibration.

Improving performance of dental resins by adding titanium dioxide nanoparticles.

OBJECTIVE: The objective of this study is to improve the performance of dental resins by adding a small amount of titanium dioxide nanoparticles (TiO2 NPs), which have outstanding mechanical properties and unique photoactivities. METHODS: Acrylic acid modified TiO2 NPs (AP25) were prepared and added to a mixture of bis-phenol-A-dimethacrylate and triethylene glycol dimethacrylate (mass ratio 1:1) at seven mass fractions. Disks made of these resins were subjected to FTIR microspectroscopy, nanoindentation, microindentation, and 3-point bending to determine the degree of vinyl conversion (DC) modulus and hardness. The shear bond strengths (SBS) of dentin adhesives containing various amount of AP25 were also examined. RESULTS: The DC increased as a function of mass fraction of AP25 and reached a plateau at 0.1%. The DC of the resin mixture was improved by ≈7% up to 91.7 ± 0.8%. The elastic modulus and hardness of the composites increased initially as more AP25 were added, and decreased after reached the maximum value at approximately 0.06% mass fraction of AP25. The maximum elastic modulus was ≈48% higher than that of the NP-free resin, and the maximum hardness was more than twice higher than that of the NP-free resin. Using these resin composites as dental adhesives, the mean SBS using resins with 0.1% mass fraction of AP25 was ≈30% higher than those using NP-free resin. SIGNIFICANCE: By adding a small amount of AP25 to the resin, the DC and the mechanical properties of resins were improved dramatically. These findings could lead to better performing dental adhesives.

Preclinical effectiveness of a novel pulp capping material.

INTRODUCTION: The purpose of this study was to evaluate the direct pulp capping response to a novel resin-based calcium phosphate cement (RCPC). METHODS: The RCPC was placed in contact with the exposed healthy pulps of dog teeth and in a follow-up study on the healthy or inflamed pulps of ferret teeth. The inflamed ferret teeth had reversible pulpitis induced with Salmonella typhimurium lipopolysaccharides. After direct pulp capping with RCPC or visible light-curing resin-modified calcium hydroxide material (VLCCH) as a control, the restorations were bonded using a composite resin. The pulp responses and dentin repair were evaluated histologically in dog teeth after 7, 28, or 90 days and in ferret teeth after 45 days. RESULTS: Most of the RCPC-treated healthy pulps and 75% of the RCPC-treated inflamed ferret teeth had dentin healing and repair, whereas those teeth treated with VLCCH had minimal healing and dentin repair. CONCLUSIONS: The direct pulp capping of ferret and dog teeth with RCPC was associated with superior healing in comparison to VLCCH.

Evaluation of dental composite shrinkage and leakage in extracted teeth using X-ray microcomputed tomography.

OBJECTIVE: Use X-ray microcomputed tomography (microCT), to test the hypothesis that composite shrinkage and sites of potential leakage in human teeth are non-uniformly distributed and depend on cavity geometry and C-factor. METHODS: Two holes of equal volume but different dimensions were drilled into the exposed dentin of extracted human molars. The cavities were filled with composite and teeth were scanned, before and after curing, using microCT. Three-dimensional (3D) reconstructions of the data were prepared and analyzed using image analysis software. RESULTS: 3D reconstructions showed that cavity geometry did not affect the polymerization shrinkage. The shrinkage for all restorations was 2.66+/-0.59%, and cavity dimensions did not affect the volume lost, either in quantity or location on the sample. Potential leakage sites were identified by gap formations and found to be non-uniformly distributed along the tooth-composite interface. Leakage in regions calculated by microCT was confirmed by visualization of sectioned samples with confocal laser scanning microscopy. SIGNIFICANCE: microCT evaluation will add tremendous value as part of a suite of tests to characterize various properties of dental materials. The non-uniform distribution of potential leakage sites about the cavities that was determined by microCT emphasizes the inadequacy of traditional methods of determining leakage, which are capable of analyzing only limited areas. Additionally, microCT evaluation can produce quantitative analyses of shrinkage and leakage, compared to the conventional methods, which are qualitative or semi-quantitative. Finally, experimentally determined shrinkage and leakage of composite in extracted teeth agrees with the results of similar experiments in model cavities, confirming the validity of those models.

Adhesion of amorphous calcium phosphate composites bonded to dentin: a study in failure modality.

AIMS: As a bioactive filler capable of remineralizing tooth structures, the main disadvantage of as-made amorphous calcium phosphate (am-ACP) are its large agglomerates. The objective of this study was to mill ACP, and compare the adhesive strength with dentin, work to fracture, and failure modes of both groups to glass-filled composites and one commercial compomer after 24 h, 1 week, 1, 3, and 6 months of exposure to simulated saliva solution (SLS). Flat dentin surfaces were acid-etched, primed, and photopolymerized. Composites were applied, photo-cured, and debonded in shear. The resin used in each composite was identical: ethoxylated bisphenol A dimethacrylate, triethylene glycol dimethacrylate, 2-hydroxyethyl methacrylate, and methacryloxyethyl phthalate. Fillers consisted of am-ACP and milled ACP (m-ACP), and a strontium-containing glass (Sr-glass) at respective mass fractions of (40, 60, and 75%). FINDINGS: Ninety percent of the fracture surfaces in this study showed adhesive failure, with most of these occurring at the dentin/primer interface. Fifty-two percent of failures after 24-h immersion occurred at the primer/composite interface. After 6 months of SLS exposure, 80% of specimens failed at the dentin/primer interface, with a 42% overall reduction in bond strength. CONCLUSIONS: Milled ACP composites showed initial mechanical advantages over am-ACP composites and the compomer, and produced a higher incidence of a failure mode consistent with stronger adhesion. Evidence is provided which suggests that milled ACP composites may offer enhanced potential in clinical bonding applications.

Structure-Composition-Property Relationships in Polymeric Amorphous Calcium Phosphate-Based Dental Composites.

Our studies of amorphous calcium phosphate (ACP)-based materials over the last decade have yielded bioactive polymeric composites capable of protecting teeth from demineralization or even regenerating lost tooth mineral. The anti-cariogenic/re-mineralizing potential of these ACP composites originates from their propensity, when exposed to the oral environment, to release in a sustained manner sufficient levels of mineral-forming calcium and phosphate ions to promote formation of stable apatitic tooth mineral. However, the less than optimal ACP filler/resin matrix cohesion, excessive polymerization shrinkage and water sorption of these experimental materials can adversely affect their physicochemical and mechanical properties, and, ultimately, limit their lifespan. This study demonstrates the effects of chemical structure and composition of the methacrylate monomers used to form the matrix phase of composites on degree of vinyl conversion (DVC) and water sorption of both copolymers and composites and the release of mineral ions from the composites. Modification of ACP surface via introducing cations and/or polymers ab initio during filler synthesis failed to yield mechanically improved composites. However, moderate improvement in composite's mechanical stability without compromising its remineralization potential was achieved by silanization and/or milling of ACP filler. Using ethoxylated bisphenol A dimethacrylate or urethane dimethacrylate as base monomers and adding moderate amounts of hydrophilic 2-hydroxyethyl methacrylate or its isomer ethyl-α-hydroxymethacrylate appears to be a promising route to maximize the remineralizing ability of the filler while maintaining high DVC. Exploration of the structure/composition/property relationships of ACP fillers and polymer matrices is complex but essential for achieving a better understanding of the fundamental mechanisms that govern dissolution/re-precipitation of bioactive ACP fillers, and, ultimately, the suitability of the composites for clinical evaluation.

Polymerization stress development in dental composites: Effect of cavity design factor.

The objective of the study was to assess the effect of the cavity design factor (C-factor) on polymerization stress development (PSD) in resin composites. An experimental resin (BT resin) was prepared, which contained 2,2-bis[p-(2'hydroxy-3'-methacryloxypropoxy)phenylene]propane (B) and triethylene glycol dimethacrylate (T) in 1:1 mass ratio, and an activator for visible light polymerization. Also an experimental composite with demonstrated remineralizing potential was formulated by inclusion into the BT resin of zirconia-hybridized amorphous calcium phosphate (ACP) filler at a mass fraction of 40 % (BT/ACP composite). A commercial glass-filled composite (TPH) was used as a control. To assess the effect of the test geometry on PSD, C-factor was systematically varied between 0.8 and 6.0 by varying the height of the cylindrical composite specimens. The measured PSD values obtained by cantilever beam tensometry for specimens with variable C-factors were normalized for mass to specimens with a C-factor of 1.33 (h=2.25 mm) as controls to give calculated PSD values. Degrees of vinyl conversions (DC) attained in the TPH control and in the experimental BT/ACP composites were measured by near-infrared spectroscopy. In both the TPH and BT/ACP composite series, PSDcalc increased with the increasing C-factor, confirming the hypothesis that the C-factor value influences PSD values. The higher PSDmeas and PSDcalc values for the experimental BT/ACP composite compared to the commercial TPH composite probably reflect differences in the type and mass of the resin and filler phases in the two types of composite. These differences also account for the observed variation (21 %) in DC attained in a BT/ACP composite 2 h after cure (69.5 %) and in the DC of the TPH composite (57.5 %) having the same C-factor. The cavity design factor seems to play a key role in influencing the PSD of bonded composites, but other factors such as composite mass and composition also must be considered for their effects on PSD.

Adhesive Bonding to Dentin Improved by Polymerizable Cyclodextrin Derivatives.

The objective of this work was to determine bonding characteristics of a hydrophilic monomer formulation containing polymerizable cyclodextrin derivatives. The hypothesis was that a formulation containing hydrophilic cross-linking diluent comonomers and cyclodextrins with functional groups attached by hydrolytically stable ether linkages could form strong adhesive bonds to dentin. The previously synthesized polymerizable cyclodextrin derivatives were formulated with sorbitol dimethacrylate, methacrylic acid and phenylbis(2,4,6-trimethylbenzoyl) phosphine oxide photoinitiator. The same formulation without the polymerizable cyclodextrin derivatives isolated the effects of the polymerizable cyclodextrin derivatives. A commercial self-etching bonding system was tested as a comparative control. Ground mid-coronal dentin was etched with 37 % phosphoric acid (H3PO4) for 15 s and rinsed with distilled water for 10 s. Formulations were applied to the moist dentin and light-cured 10 s. A packable composite was then applied through irises and light-cured 60 s. Teeth were stored in water for 24 h before bonds were tested in a shearing orientation. One-way ANOVA was performed on the data. The average values of shear bond strengths were defined as loads at fracture divided by the 4 mm diameter iris areas. The average value of shear bond strength for the formulation containing the polymerizable cyclodextrin derivatives was higher (p < 0.05), where p is a fraction of the probability distribution) than that of the same monomeric formulation except that the polymerizable cyclodextrin derivatives were not included. This was supporting evidence that the polymerizable cyclodextrin derivatives contributed to improved bonding. The average value of shear bond strength for the formulation containing the polymerizable cyclodextrin derivatives was also higher (p < 0.05) than that of the commercial self-etching bonding system. These preliminary results are in accordance with the hypothesis that formulations containing polymerizable cyclodextrin derivatives can form strong adhesive bonds to hydrated dentin surfaces. Further improvements in bonding to hydrated biological tissues by use of advanced formulations are anticipated.

X-ray imaging optimization of 3D tissue engineering scaffolds via combinatorial fabrication methods.

We have developed a combinatorial method for determining optimum tissue scaffold composition for several X-ray imaging techniques. X-ray radiography and X-ray microcomputed tomography enable non-invasive imaging of implants in vivo and in vitro. However, highly porous polymeric scaffolds do not always possess sufficient X-ray contrast and are therefore difficult to image with X-ray-based techniques. Incorporation of high radiocontrast atoms, such as iodine, into the polymer structure improves X-ray radiopacity but also affects physicochemical properties and material performance. Thus, we have developed a combinatorial library approach to efficiently determine the minimum amount of contrast agent necessary for X-ray-based imaging. The combinatorial approach is demonstrated in a polymer blend scaffold system where X-ray imaging of poly(desaminotyrosyl-tyrosine ethyl ester carbonate) (pDTEc) scaffolds is improved through a controlled composition variation with an iodinated-pDTEc analog (pI(2)DTEc). The results show that pDTEc scaffolds must include at least 9%, 16%, 38% or 46% pI(2)DTEc (by mass) to enable effective imaging by microradiography, dental radiography, dental radiography through 0.75cm of muscle tissue or microcomputed tomography, respectively. Only two scaffold libraries were required to determine these minimum pI(2)DTEc percentages required for X-ray imaging, which demonstrates the efficiency of this new combinatorial approach for optimizing scaffold formulations.

The use of amorphous calcium phosphate composites as bioactive basing materials: their effect on the strength of the composite/adhesive/dentin bond.

BACKGROUND: Amorphous calcium phosphate (ACP) composites release calcium and phosphate ions in aqueous environments, which may lead to deposition of apatitic mineral in tooth structure. The authors evaluate the strength of the composite/adhesive/dentin bond shear bond strength (SBS) for ACP basing-composites after various periods of water aging. METHODS: The authors made the experimental composites by using two resin matrices with various ACPs or a commercial strontium ion-leachable glass. They applied successive coats of a dentin adhesive and basing composite to an acid-etched dentin surface and photopolymerized them. They added a commercial resin-based composite and light cured it. They determined the specimens' SBS after they were aged in water for various periods at 37 degrees C. RESULTS: The SBS of the ACP composites was 18.3 +/- 3.5 megapascals, independent of filler type, resin composition and water-aging interval. After 24 hours of water aging, 92.6 percent of surfaces showed the adhesive failure. After two weeks of water aging, adhesive/cohesive failures were predominant in unmilled and milled ACP composites. CONCLUSIONS: The SBS of ACP composites appears to be unaffected by filler type or immersion time for up to six months. The type of adhesive failure occurring with prolonged aqueous exposure is affected by filler type. CLINICAL IMPLICATIONS: These materials may be effective remineralizing/antidemineralizing agents and may be clinically applicable as adhesives, protective liners and bases, orthodontic cements and pit-and-fissure sealants.

Three-body wear of dental resin composites reinforced with silica-fused whiskers.

OBJECTIVE: Recent studies used silica-fused whiskers to increase the strength and toughness of resin composites. This study investigated the three-body wear of whisker composites. It was hypothesized that the whisker composites would be more wear resistant than composites reinforced with fine glass particles, and the whisker-to-silica filler ratio would significantly affect wear. METHODS: Silica particles were mixed with silicon nitride whiskers at seven different whisker/(whisker + silica) mass fractions (%): 0, 16.7, 33.3, 50, 66.7, 83.3, and 100. Each mixture was heated at 800 degrees C to fuse the silica particles onto the whiskers. Each powder was then silanized and incorporated into a dental resin to make the wear specimens. A four-station wear machine was used with specimens immersed in a slurry containing polymethyl methacrylate beads, and a steel pin was loaded and rotated against the specimen at a maximum load of 76 N. RESULTS: Whisker-to-silica ratio had significant effects (one-way ANOVA; p < 0.001) on wear. After 4 x 10(5) wear cycles, the whisker composite at whisker/(whisker + silica) of 16.7% had a wear scar diameter (mean +/- sd; n = 6) of (643 +/- 39) microm and a wear depth of (82 +/- 19) microm, significantly less than a wear scar diameter of (1184 +/- 34) microm and a wear depth of (173 +/- 15) microm of a commercial prosthetic composite reinforced with fine glass particles (Tukey's multiple comparison). SEM examination revealed that, instead of whiskers protruding from the worn surface, the whiskers were worn with the composite surface, resulting in relatively smooth wear surfaces. SIGNIFICANCE: Silica-fused whisker reinforcement produced dental resin composites that exhibited high resistance to wear with smooth wear surfaces. These properties, together with the strength and fracture toughness being twice those of current glass particle-reinforced composites, may help extend the use of resin composite to large stress-bearing posterior restorations.

[Studies on bonding interfaces of two dentin adhesives by scanning electron microscopy].

OBJECTIVE: To purpose of this study was to investigate the microstructure and bonding mechanism of bonding interfaces of two current one-bottle dentin bond systems(Prime & Bond NT, PBNT; Prime one Mirage, P-One). METHODS: Fifteen extracted, caries-free human molars were prepared according to a modified method used for microtensile bond strength measurement. Each crown was divided into nearly equal halves with a 5 mm deep slot for accepting treatment of the two dentin bond systems, respectively. After 24 h storage in distilled water at 37 degrees C, the bonded teeth were subjected to two treatments: 5 teeth were observed by and tested for microtensile bond strengths without further treatment and 10 teeth were thermocycled(2400 cycles, between 5 degrees C and 55 degrees C) prior to SEM observation and bond strength testing. Hour-glass shaped microspecimens with a thickness of approximately 0.5 mm were cut from each tooth and used for SEM observation and microtensile bond strength measurement. RESULTS: A typical resin-infiltrated zone (hybrid layer) with a thickness of 3-5 microns and well-formed cone shaped resin tags that penetrated the dentinal tubules were clearly observed at the resin-dentin interfaces in the two bond systems. There were multiple lateral branches of tubular resin tags that interconnected to form a micro-network of resin. No evident differences in SEM images between the two bond systems as well as between thermocycling and without thermocycling in each bond system were found. CONCLUSION: PBNT and P-One provided good resin infiltration, producing a three-dimensional interlocking micro-network of resin tags in the dentin tubules with multiple lateral branches that penetrate the intertubular dentin, which positively influenced the adhesion between dentin and the two bond systems.

A microshear test to measure bond strengths of dentin-polymer interfaces.

The microbond test. a single fiber shear test, has been adapted to be a microshear test for the measurement of the adhesion of resin-based dental materials to dentin and enamel. The objective of this study is to improve the design of this microshear test so that it can provide accurate and reliable shear bond strength data. In the current design of the microshear test apparatus, the bonding diameters of the specimens have been as small as 0.70 mm. The smaller diameters give researchers the ability to test several bonded specimens on one flat dentin or enamel surface, thus allowing both for the regional mapping of the mineralized surface and the conservation of extracted teeth needed to provide the necessary substrates. The test corfiguration used in earlier studies has been modified through finite element analysis to address concerns in the test methodology. The results of this study show that the microshear bond test can be a useful tool in helping to understand the complex interactions that occur at the interface between dental composites and dentin and/or enamel surfaces, especially at interfacial sites not amenable to macroshear testing.

Dental resin composites containing silica-fused whiskers--effects of whisker-to-silica ratio on fracture toughness and indentation properties.

Dental resin composites need to be strengthened in order to improve their performance in large stress-bearing applications such as crowns and multiple-unit restorations. Recently, silica-fused ceramic whiskers were used to reinforce dental composites, and the whisker-to-silica ratio was found to be a key microstructural parameter that determined the composite strength. The aim of this study was to further investigate the effects of whisker-to-silica ratio on the fracture toughness, elastic modulus, hardness and brittleness of the composite. Silica particles and silicon carbide whiskers were mixed at whisker:silica mass ratios of 0:1, 1:5. 1:2, 1:1, 2:1, 5:1, and 1:0. Each mixture was thermally fused, silanized and combined with a dental resin at a filler mass percentage of 60%. Fracture toughness was measured with a single-edge notched beam method. Elastic modulus and hardness were measured with a nano-indentation system. Whisker:silica ratio had significant effects on composite properties. The composite toughness (mean+/-SD; n = 9) at whisker:silica = 2:1 was (2.47+/-0.28) MPa m(1/2), significantly higher than (1.02+/-0.23) at whisker:silica = 0:1, (1.13+/-0.19) of a prosthetic composite control, and (0.95+/-0.11) of an inlay/onlay composite control (Tukey's at family confidence coefficient = 0.95). Elastic modulus increased monotonically and hardness plateaued with increasing the whisker:silica ratio. Increasing the whisker:silica ratio also decreased the composite brittleness, which became about 1/3 of that of the inlay:onlay control. Electron microscopy revealed relatively flat fracture surfaces for the controls, but much rougher ones for the whisker composites, with fracture steps and whisker pullout contributing to toughness. The whiskers appeared to be well-bonded with the matrix, probably due to the fused silica producing rough whisker surfaces. Reinforcement with silica-fused whiskers resulted in novel dental composites that possessed fracture toughness two times higher than, and brittleness less than half of current dental composites.

Effect of thermal cycling on whisker-reinforced dental resin composites.

The mechanical properties of dental resin composites need to be improved in order to extend their use to high stress-bearing applications such as crown and bridge restorations. Recent studies used single crystal ceramic whiskers to reinforce dental composites. The aim of this study was to investigate the effects of thermal cycling on whisker-reinforced composites. It was hypothesized that the whisker composites would not show a reduction in mechanical properties or the breakdown of whisker-resin interface after thermal cycling. Silicon carbide whiskers were mixed with silica particles, thermally fused, then silanized and incorporated into resin to make flexural specimens. The filler mass fraction ranged from 0% to 70%. The specimens were thermal cycled in 5 degrees C and 60 degrees C water baths, and then fractured in three-point bending to measure strength. Nano-indentation was used to measure modulus and hardness. No significant loss in composite strength, modulus and hardness was found after 10(5) thermal cycles (family confidence coefficient=0.95; Tukey's multiple comparison test). The strength of whisker composite increased with filler level up to 60%, then plateaued when filler level was further increased to 70%; the modulus and hardness increased monotonically with filler level. The strength and modulus of whisker composite at 70% filler level were significantly higher than the non-whisker controls both before and after thermal cycling. SEM revealed no separation at the whisker-matrix interfaces, and observed resin remnants on the pulled-out whiskers, indicating strong whisker-resin bonding even after 10(5) thermal cycles. In conclusion, novel dental resin composites containing silica-fused whiskers possessed superior strength and modulus compared to non-whisker composites both before and after thermal cycling. The whisker-resin bonding appeared to be resistant to thermal cycling in water, so that no loss in composite strength or stiffness occurred after prolonged thermal cycling.