Biaxial Flexure Research Articles

The comparison of relative reliability on biaxial and three point flexural strength testing methods of light curing composite resin

The possibility of applying a hi-axial flexure strength test on composite resin was examined using three point and hi-axial flexure strength tests to measure the strength of the light-cured resin and to compare the relative reliability using the Weibull modulus. The materials used in this study were light-curing restorative materials, (Bisco, Schaumburg, USA). The hi-axial flexure strength measurements used the piston-on-3-ball test according to the regulations of the International Organization for Standardization (ISO) 6872 and were divided into 6 groups, where the radius of the specimens were 12mm (radius connecting the 3-balls: 3.75mm), 16 mm(radius connecting the 3-balls: 5mm), and the thickness were 0.5mm, 1mm, 2mn for each radius. The hi-axial flexure strength of the were higher than the three point flexure strength and the Weibull modulus value were also higher in all of the bi-axial flexure strength groups, indicating that the hi-axial strength test is relatively less affected by experimental error. In addition, the 2 mm thick specimens had the highest Weibull modulus values in the hi-axial flexure strength test, and the group showed no significant statistical difference (p>0.05). Besides the 2mm group, each group showed significant statistical differences (p

The in vitro failure of all-ceramic crowns and the connector area of fixed partial dentures using bilayered ceramic specimens: The influence of core to dentin thickness ratio

Aims To assess the effect of core to dentine thickness ratio on the bi-axial flexure strength and fracture mode and failure origin using bilayered ceramic specimens as an in vitro assessment for all-ceramic crowns and the connector area of fixed partial dentures (FPDs). Methods Sets of 30 bilayered composite discs, with a core layer thickness of 1 mm and with core to dentine thickness ratios of 2:1, 1:1 and 1:2, were tested in bi-axial flexure with both the reinforcing core and veneering dentine loaded in tension. Mean flexure strengths, standard deviations and associated Weibull moduli ( m) were determined. Optical microscopy was employed for identification of the fracture mode and failure origin for the failure all-ceramic crowns and the connector area of FPDs. Results For a core thickness of 1 mm the core to dentine thickness ratio failed to influence the bi-axial flexure strength data when both the reinforcing core and veneering dentine porcelain were tested in tension. The number of fracture fragments, frequency of occurrence of specimen delaminations, Hertzian cone formations and sub-critical radial cracking in the bilayered dental ceramic composite disc-shaped specimens were dependent on the core to dentine thickness ratio and the surface loaded in tension. Significance The fracture mode and failure origin in bilayered ceramics tested to represent the failure mode of all-ceramic crowns and FPDs was dependent upon the core to dentine thickness ratio employed. However, the conventional wisdom regarding bilayered ceramic specimens with core thicknesses greater than 1 mm are not followed when the core thickness was reduced to 1 mm since the fracture resistance was not dependent on the core to dentine thickness ratio.

Interphase structure–property relationships in thermoset dimethacrylate nanocomposites

Objectives The aim of this research was to better understand the relationships between interphase composition and the resultant mechanical properties of thermoset methacrylate nanocomposites, ultimately for the purpose of improving the properties of dental restorative materials through manipulation of the interphase. Methods Silica nanoparticles were silanized with three different silanes and blends of those silanes to generate six different interphase compositions. The silanes varied in their relative polarity, flexibility, and reactivity towards photo-polymerization. Composites containing 60% by mass of the silanized fillers were prepared and analyzed for uncured paste handling characteristics, vinyl conversion, biaxial flexure strength (BFS), modulus, and Knoop hardness. Results Dual silanization of the fillers improved the handling characteristics of the uncured composite pastes compared to those containing fillers silanized with 3-methacryloxypropyltrimethoxysilane. To obtain high BFS, functional groups reactive in free radical polymerization were needed in the composite interphase, but a high concentration of those groups was not necessary. Moduli were highest for composites with interphases that contained styrylethyltrimethoxysilane, a reactive aromatic silane. The hardness values of the composites with reactive interphases were all comparable. Methacrylate conversion was only modestly influenced by silane interphase composition. Significance This study suggests that dual silanization is a practical method for improving the handling characteristics of uncured dental restorative nanocomposites while maintaining or improving the mechanical properties of the cured composites.

Ethoxylated bisphenol dimethacrylate-based amorphous calcium phosphate composites

Improving the anti-demineralizing/remineralizing and mechanical properties of amorphous calcium phosphate (ACP) composites has been the focus of our recent research. In this study, an ethoxylated bisphenol A dimethacrylate (EBPADMA) was blended with triethylene glycol dimethacrylate (TEGDMA), 2-hydroxyethyl methacrylate (HEMA) and methacryloxyethyl phthalate (MEP) to form experimental resins with different EBPADMA/TEGDMA molar ratios (0.50, 0.85 and 1.35) and a constant HEMA/MEP molar ratio (8.26). Composites were prepared by admixture of either unmilled or milled zirconia-ACP filler (40% by mass) and photo-activated resin (60% by mass). One aim was to test if improved ion release can be achieved by elevating the EBPADMA/TEGDMA ratio while lowering the level of surface active methacryloxyethyl phthalate in the resin without adversely affecting the biaxial flexure strength (BFS), degree of vinyl conversion (DC) and water sorption (WS) of composites. A second aim was to assess the effect of using milled vs. unmilled ACP on these properties. Ion release of all composites was significantly above the theoretical minimum necessary for remineralization. Calcium ion release was not impeded by binding with the carboxylic acid groups of MEP. Increased supersaturation was attained with increasing EBPADMA/TEGDMA ratio in the resin. Variations in resin composition had no effect on BFS or DC of composites. The BFS of the milled ACP composites was higher than the BFS of unmilled ACP composites (56% and 79%, respectively for dry and wet specimens). DC of composites was only moderately reduced (13.6% and 7.3%, for unmilled and milled ACP, respectively) compared to unfilled resins. WS decreased in the following order: unmilled ACP composites > milled ACP composites > copolymers. Fine-tuning of the resin and utilizing milled ACP filler improved the remineralizing potential of ACP composites without impeding their DC, BFS or WS.

Indentation crack profiles of cordierite materials under mechanical and thermal biaxial stresses

The indentation crack profiles under mechanical and thermal stresses of cordierite materials obtained from a commercial powder were studied. Disks were prepared by slip casting and sintering, and they were indented (Vickers; 44.1 N; 15 s) at the center of one of their surfaces to be subjected to flexion in the mechanical test or to a sudden temperature change in the thermal shock test. Indented specimens were fractured in biaxial flexure (BF) or thermal shock (TS) tests. Some indented disks were thermally treated following two different schedules that involve exposures at high temperatures without ( T 1) and with a sudden cooling ( T 2). These specimens were fractured in biaxial flexure to observe the fracture surfaces. In all specimens (BF, TS, T 1 and T 2), the evolution of the indentation crack profiles was fractographically analyzed by SEM. In order to study the crack shape and the profile evolution, both the length and the depth of the indentation cracks were measured.

Modelling of bonded multilayered disks subjected to biaxial flexure tests

Biaxial flexure tests have been used extensively for the strength measurements of monolithic brittle materials. However, despite the increasing applications of multilayered structures, characterization of their strengths using biaxial flexure tests is unavailable. This is because the analytical description of the relation between the strength and the fracture load for multilayers subjected to biaxial flexure tests is nonexistent. To characterize the biaxial strength of multilayers, an analytical model is developed in the present study to derive the general closed-form solutions for the elastic stress distributions in thin multilayered disks subjected to biaxial flexure tests. To verify the analytical solutions, finite element analyses are performed on trilayered disks subjected to ring-on-ring tests. Good agreement is obtained between analytical and numerical results. The present closed-form solutions hence provide a basis for evaluating the biaxial strength of multilayered systems. Depending upon the strength of the individual layers and the stress distribution through the thickness of the multilayer during testing, cracking can initiate from any layer under tension.

The influence of simulated masticatory loading regimes on the bi-axial flexure strength and reliability of a Y-TZP dental ceramic

The purpose of the current study was to examine the influence of simulated masticatory loading regimes, to which all-ceramic crown or bridge restorations will routinely be subjected during their service-life, on the performance of a yttria-stabilised tetragonal zirconia polycrystalline (Y-TZP) dental ceramic. Ten sets of 30 Y-TZP ceramic discs (13 mm diameter, 1.48-1.54 mm thickness) supplied by the manufacturer were randomly selected. Six groups were loaded for 2000 cycles at 500 N (383-420 MPa), 700N (536-588 MPa) and 800 N (613-672 MPa) with three groups maintained dry and the remaining three groups loaded while immersed in water at 37+/-1 degrees C. A further two groups underwent extended simulated masticatory loading regimes at 80 N (61-67 MPa) for 10(4) and 10(5)cycles under dry conditions. The mean bi-axial flexure strengths, standard deviations and associated Weibull moduli (m) were determined. The surface hardness was also determined using the Vickers hardness indentation technique. No significant difference (P>0.05) was identified in the bi-axial flexure strength of the simulated masticatory loading regimes and the control specimens loaded dry or wet. A significant increase in m was identified for the Y-TZP specimens following loading while immersed in water (8.6+/-1.6, 8.5+/-1.6 and 10.3+/-1.9) compared with the control (7.1+/-1.3). However, the extended loading regime to 10(5)cycles resulted in a significant reduction in the m of the Y-TZP specimens (5.3+/-1.0) compared with the control. Localised areas of increased surface hardness were identified to occur directly beneath the spherical indenter. The occurrence of localised areas of increased surface hardness could be the result of either a transformation toughening mechanism or crushing and densification of the material beneath the indentor manifested as the formation of a surface layer of compressive stresses that counteracted the tensile field generated at the tip of a propagating crack which increased the Weibull modulus of the Y-TZP specimens. The reduced reliability of the Y-TZP specimens loaded to 80 N for 10(5)cycles was associated with the accumulation of subcritical damage as a result of the extended nature of loading.

コンポジットレジンと低粘性コンポジットレジン積層の2軸曲げ強さ -コンポジット/低粘性コンポジットレジン厚み比の影響-_

コンポジットレジンと低粘性コンポジットレジン積層の2軸曲げ強さ -コンポジット/低粘性コンポジットレジン厚み比の影響-_

The influence of surface modification techniques on the performance of a Y-TZP dental ceramic

The purpose of the current study was to examine the influence of the pre-cementation surface modification techniques, namely alumina abrasion and surface grinding, routinely employed by dental practitioners prior to cementation and placement of crown and bridge restorations on the performance of a Y-TZP dental ceramic. Twelve sets of 30 Lava ceramic discs (13 mm diameter, 1.5mm thickness) supplied by the manufacturer were randomly selected. Six groups were abraded utilising 25, 50 and 110 microm alumina and stored dry or in a water bath at 37+/-1 degrees C for 24 h. Four groups were ground utilising a fine or a coarse grit diamond bur, specimens were ground dry or while using water as a coolant. The mean bi-axial flexure strengths, standard deviations and associated Weibull moduli (m) were determined. The surface roughness, hardness and phase composition were assessed utilising profilometry, the Vicker's hardness indentation and X-ray diffraction, respectively. No significant difference (P > 0.05) was identified in the bi-axial flexure strength of the 25, 50 and 110 microm alumina-abraded and the control specimens stored dry and wet for 24h. However, a significant increase in m was identified for the alumina-abraded specimens stored dry (10.7+/-1.9, 10.6+/-1.9 and 10.6+/-1.9) compared with the control (7.5+/-1.3) and the specimens stored in a water bath. In addition, the alumina abrasion regimes reduced the surface roughness compared with the controls. The coarse grinding regime significantly reduced both the bi-axial flexure strength and the associated m compared with the control whilst no significant difference was identified for the fine grinding regimes. The surface modification techniques initiated a phase transformation mechanism and resulted in the formation of a layer of compressive stresses on the surface of the disc-shaped specimens. The combination of the reduced surface roughness and the formation of a surface layer of compressive stress as a result of the alumina abrasion regimes investigated increased the reliability of the bi-axial flexure strength. The presence of water in the current study did not detrimentally influence the performance of the Y-TZP ceramic under investigation. Coarse grinding significantly reduced the bi-axial flexure strength and m due to the increased surface roughness. The Y-TZP specimens in the current investigation underwent a toughening mechanism as a result of a phase transformation mechanism which generated a transformation compressive stress that opposes the externally applied, crack-propagating tensile stress.

Analyses of multilayered dental ceramics subjected to biaxial flexure tests

The purpose of this study was to formulate explicitly the equation to relate the biaxial strength of multilayered dental ceramics to the fracture load for multilayered discs subjected to biaxial flexure tests. Analytical modeling showed that the solutions for multilayered discs subjected to biaxial flexure tests could be obtained from the existing solutions for monolayered systems by replacing the neutral surface position and the flexural rigidity of monolayers with those of multilayers. Finite element analyses were performed on porcelain/zirconia bilayered discs subjected to piston-on-ring and ring-on-ring tests to verify the analytical results. Good agreement was obtained between (i) present analytical results and Roark's formulas for stresses at the top and the bottom surfaces of bimetallic discs subjected to bending, and (ii) present analytical and finite element results for porcelain/zirconia bilayered discs subjected to piston-on-ring and ring-on-ring tests. The present closed-form solutions provide a basis for evaluating the biaxial strength of multilayered dental ceramics. Depending upon the strength of the individual layers and the stress distribution through the thickness of the multilayer during tests, cracking can initiate from any layer under tension.

Fabrication of net shape reaction bonded oxide ceramics

Zero-shrinkage mullite-zirconia ceramics with Y 2 O 3 and MgO as sintering additives and siloxanes as low loss binders were fabricated by direct oxidation of ZrAl 3 / ZrSi 2 and ZrAl 3 / Zr 2 Si / 3 Y - ZrO 2 powder compacts. Depending on the starting composition the sintered ceramics contain either ZrO 2 and mullite or ZrO 2, alumina and mullite as crystalline phases. The reaction bonding process was studied by thermogravimetry, dilatometry and quantitative XRD-phase analysis. Due to their dense microstructure reaction-bonded 55/45 (vol.%) ZrO 2/mullite composites sintered at 1450 ° C exhibit biaxial flexure strengths up to 630 MPa. Reaction bonded ZrO 2 / Al 2 O 3 /mullite composites (30/25/45 vol.%) show biaxial flexure strengths of 635 MPa.

Buckling of centerline-stiffened plates subjected to uniaxial eccentric compression

A solution for the elastic buckling of flat rectangular plates with centerline boundary conditions subjected to non-uniform in-plane axial compression is presented. The loaded edges are simply supported, the non-loaded edges are free, and the centerline is simply supported with a variable rotational stiffness. The Galerkin method is used to establish an eigenvalue problem and a series solution for plate buckling coefficients is obtained by using combined trigonometric and polynomial functions that satisfy the boundary conditions. It is demonstrated that the formulation approaches the classical solution of a plate with a clamped edge as the variable rotational stiffness is increased. The variation of buckling coefficient with aspect ratio is presented for various stress gradient ratios. The coupling between plate aspect ratio, centerline rotational stiffness, and gradient of applied compressive stress is illustrated and discussed. The solution is applicable to stiffened plates and I-shaped beams that are subjected to biaxial bending or combined flexure and torsion, and is important to estimate the reduction in elastic buckling capacity due to stress gradient.

Effects of resin hydrophilicity on water sorption and changes in modulus of elasticity

As acidic monomers of self-etching adhesives are incorporated into dental adhesives at high concentrations, the adhesive becomes more hydrophilic. Water sorption by polymers causes plasticization and lowers mechanical properties. The purpose of this study was to compare the water sorption and modulus of elasticity ( E) of five experimental neat resins (EX) of increasing hydrophilicity, as ranked by their Hoy's solubility parameters and five commercial resins. Methods After measuring the initial modulus of all resin disks by biaxial flexure, half the specimens were stored in hexadecane and the rest were stored in water. Repeated measurements of stiffness were made for 3 days. Water sorption and solubility measurements were made in a parallel experiment. Results None of the specimens stored in oil showed any significant decrease in modulus. All resins stored in water exhibited a time-dependent decrease in modulus that was proportional to their degree of water sorption. Water sorption of EX was proportional to Hoy's solubility parameter for polar forces ( δ p ) with increasing polarity resulting in higher sorption. The least hydrophilic resin absorbed 0.55 wt% water and showed a 15% decrease in modulus after 3 days. The most hydrophilic experimental resin absorbed 12.8 wt% water and showed a 73% modulus decrease during the same period. The commercial resins absorbed between 5% and 12% water that was associated with a 19–42% reduction in modulus over 3 days.

The influence of short and medium-term water immersion on the hydrolytic stability of novel low-shrink dental composites

Differences in mechanical and physical properties exhibited by novel low-shrink resin-based composite (RBC) formulations compared with conventional methacrylate RBCs may contribute to the clinical success of the candidate material. The aim of the current study was to investigate the effect of water uptake characteristics and water solubility on the mechanical properties of two methacrylate (Z100 and Filtek Z250), an experimental oxirane (OXI) and silorane (SIL) RBC following short- and medium-term immersion. The water sorption/solubility and associated diffusion coefficients of each material (n=5) were measured using gravimetric analysis following short- (0.1, 0.5, 1, 4, 24 and 48 h) and medium-term (1, 4, 12 and 26w) immersion. The bi-axial flexure strength, associated Weibull moduli (n=20) and fracture analysis using scanning electron microscopy (SEM) of each material for similar immersion periods was also investigated. Following 0.5h and each subsequent short- and medium-term immersion period the water sorption of Z100 and Filtek Z250 was decreased compared with OXI. A significant decrease in bi-axial flexure strength and associated increase in filler particle exfoliation identified through SEM was identified for OXI compared with Z100, Filtek Z250 and SIL following 26w immersion. SIL exhibited the significantly lowest water sorption, solubility and associated diffusion coefficient following each immersion period. The increase in water sorption, solubility and the associated diffusion coefficient of the experimental oxirane RBC, OXI was manifested as a significant decrease in bi-axial flexure strength and attributed to the decrease in synergy between the filler particles and resin matrix. The decreased water sorption, solubility and associated diffusion coefficient of the experimental silorane RBC, SIL may potentially improve hydrolytic stability of RBC restorations demonstrated by the non-significant decrease in bi-axial flexure strength following medium-term immersion.

The reliability of standardized flexure strength testing procedures for a light-activated resin-based composite

To investigate the differences in the reliability of three-point flexure strength (TFS) and bi-axial flexure strength (BFS) data of a dental resin-based composite (RBC) irradiated by a hand-held or an oven light-curing unit (LCU). Three-point bar-shaped (25 x 2 x 2 mm3) and bi-axial disc-shaped (12 mm diameter, 2 mm thick) specimens of Filtek Z250 were polymerized utilizing either a hand-held (n = 20) or an oven-LCU (n = 20). The mean TFS and BFS, associated Weibull moduli and degree of conversion (DC) for each curing regime were obtained following 24 h immersion in a light-proof water bath maintained at 37 +/-1 degrees C. A significant decrease in TFS (129 +/- 15 and 127 +/- 13 MPa) compared with BFS (140 +/- 12 and 148 +/- 13 MPa) was identified for specimens irradiated with both LCU types (P < 0.001). The Weibull moduli of TFS data associated with the hand-held--was significantly decreased compared with the oven-LCU since confidence intervals did not overlap (7.5-9.4 and 9.5-10.6, respectively). In contrast, the Weibull moduli of the BFS data associated with either LCU were not significant (11.3-12.4 and 11.3-13.5). A significant decrease in the DC of three-point and bi-axial flexure specimens irradiated with the hand-held compared with the oven-LCU was reported (P = 0.031). The improved experimental reliability combined with the increased clinical relevance in specimen geometry of disc-compared with bar-shaped specimens may advocate bi-axial flexure testing methodology as the standard to assess the strength of light-activated dental RBCs. The differences in extent of polymerization of RBC specimens cured with either LCU were not consistent with an equivalent dose of light energy density. This phenomenon may be attributed to differences in polymerization efficiency associated with the quantity of useful light energy emitted from the hand-held--compared with the oven-LCU.

Strength and Fracture Toughness of Ceramic Materials for Metal-Ceramic Prosthetic Dentistry

The strength in biaxial flexure and the fracture toughness on indentation of the specimens of ceramic materials for the coverage of metal-ceramic prostheses were studied. The strength was established to be mainly determined by their microstructure and sintering conditions. Comparative studies demonstrated that Ultropaline and VITA OMEGA 900 ceramic compositions exhibited more uniform distribution of leucite microcrystals and higher strength and fracture toughness than Duceram Plus and IPS Classic materials.

The effect of a layer of resin luting agent on the biaxial flexure strength of two all-ceramic systems

The influence of a layer of resin luting agent on the longevity of glass-ceramic crowns has been demonstrated in some laboratory and clinical studies. The mechanisms of glass-ceramic crown failure and the influence of the resin luting agent layer are still not clearly understood. The objectives of this study were to examine the difference in biaxial flexure strength between 2 glass-ceramic dental materials and to examine the influence of a layer of resin luting agent on the characteristic strength of these materials. Thirty-seven disks, 15 mm x 1.5 mm, each of IPS Empress and IPS Empress2, were fabricated according to the manufacturer's recommendations. The surface of each disk underwent acid etching and silanation. The disks from each group were arbitrarily divided into 2 subgroups. One subgroup of each material type was selected to receive a thin (approximately 0.1 mm) layer of resin luting agent (Nexus 2), whereas the other subgroups remained unaltered. Each disk was loaded, with the treated surface down, using a ball-on-ring biaxial configuration in a universal testing machine. The failure loads (N) were recorded, and the biaxial flexure strength for each disk was calculated. Characteristic Weibull parameters and a +/-95% confidence interval were determined. A 2-way analysis of variance (alpha=.05) on transformed fracture strength data was used to determine significant differences between groups. The Weibull characteristic strength of IPS Empress2 (213 MPa) was 75% higher than IPS Empress (122 MPa). The results also show that the application of a thin layer of resin luting agent significantly increased (P <.001) the characteristic strength of both IPS Empress and IPS Empress2 by 45.6% and 47.6%, respectively. The higher strength of the resin-coated specimens cannot be explained in terms of standard fracture mechanics alone. Results suggested that IPS Empress had significantly lower characteristic strength than IPS Empress2. A relatively thin layer of resin luting agent bonded to both IPS Empress and IPS Empress2 significantly increased the characteristic strength of the ceramics.

Improved Form of a Fracture Mechanics Based Failure Probability Model for Brittle Materials

Improved Form of a Fracture Mechanics Based Failure Probability Model for Brittle Materials

Amorphous Calcium Phosphate Based Polymeric Composites: Effects of Polymer Composition and Filler's Particle Size on Composite Properties

This study explores how a) the resin grafting potential for amorphous calcium phosphate (ACP) and b) particle size of ACP affects physicochemical properties of composites. Copolymers and composites were evaluated for biaxial flexure strength (BFS), degree of vinyl conversion (DC), mineral ion release and water sorption (WS). Milled ACP composites were superior to unmilled ACP composites and exhibited 62 % and 77 % higher BFS values (dry and wet state, respectively). The average DC of copolymers 24 h after curing was 80 %. DC of composites decreased 10.3 % for unmilled Zr-ACP and 4.6 % for milled Zr-ACP when compared to the corresponding copolymers. The WS increased as follows: copolymers &lt; milled Zr-ACP composites &lt; unmilled Zr-ACP composites. The levels of Ca and PO4 released from both types of composites increased with the increasing EBPADMA/TEGDMA ratio in the matrix. They were significantly above the minimum necessary for the redeposition of HAP to occur. No significant consumption of released calcium by the carboxylic groups of methacryloxyethyl phtahalate (MEP) occurred at a mass fraction of 2.6 % of MEP in the resin. Improvements in ACP composite’s physicochemical properties are achieved by fine tuning of the resin and improved ACP’s dispersion within the polymer matrix after ball-milling.

Systematic variation of interfacial phase reactivity in dental nanocomposites

This study was designed to determine the effect of varying the chemistry of the interfacial phase on critical composite properties in dental nanocomposite materials. Silica nanoparticles were silanized with varying ratios of 3-methacryloxypropyltrimethoxysilane (MPTMS) and octyltrimethoxysilane (OTMS) while keeping the total amount of silane constant at 10% by mass fraction relative to the mass of filler. The silanized nanoparticles were mixed into a dimethacrylate resin (60% filler by mass fraction). The mechanical properties of the uncured pastes were assessed by compression testing between parallel plates. The composites were photo-cured and tested by biaxial flexure and three-point bend flexure testing. Fracture surfaces were analyzed by field-emission scanning electron microscopy (FE-SEM). At maximized filler mass fractions, the workabilities of the uncured pastes were better maintained as the fraction of OTMS in the interphase increased relative to MPTMS. The flexure strengths and moduli of the MPTMS silanized and dual silanized composites were similar but decreased as OTMS mass fractions in the silane mixture increased to 7.5% and 10%. FE-SEM images revealed evidence for phase separation in the composites containing silica silanized with high fractions of OTMS. Among the potential practical benefits of dual silanized nanoparticles are the improved workability of composite pastes with higher filler loadings that should lead to higher modulus composites with lower polymerization shrinkage.