Conventional Methacrylate-based Composites Research Articles

Effect of water storage on flexural strength of silorane and methacrylate-based composite resins.

ObjectivesThis study assessed the effect of water storage on the flexural strength (FS) of low shrinkage composites.Materials and MethodsA total of 165 bar-shaped specimens (2 × 2 × 25 mm) were fabricated of 2 low shrinkage composites (Filtek P90 [3M ESPE], GC Kalore [GC International]) and a conventional methacrylate-based composite (Filtek Z250 [3M ESPE]). The specimens were subjected to 3-point bending test at 6 time intervals, namely: immediately after curing, at 24 hours, 1 week, 1 month, 6 months, and 1 year following storage in wet and dry conditions. The FS of the specimens were measured by applying compressive load at a crosshead speed of 1.0 mm/min. Data was analyzed using 3-way analysis of variance (ANOVA) and Tukey's test.ResultsThree-way ANOVA revealed significant interactions between time, type of composite, and storage condition (p = 0.001). Tukey's multiple comparison test revealed significant reductions in FS of all composites after 6 months and 1 year of storage in distilled water compared to dry condition.ConclusionsFiltek P90 showed the highest and GC Kalore showed the lowest FS after 1 year storage in distilled water. The immediate high strength of Filtek Z250 significantly decreased at 1 year and its final value was lower than that of Filtek P90.

Influence of the Compliance and Layering Method on the Wall Deflection of Simulated Cavities in Bulk-fill Composite Restoration.

The aim of this study was to investigate the effects of the layering method and compliance on the wall deflection of simulated cavities in bulk-fill and conventional composite restorations and to examine the relationships between the wall deflection and the polymerization shrinkage, flexural modulus, and polymerization shrinkage stress of composites. Six light-cured composites were used in this study. Two of these were conventional methacrylate-based composites (Filtek Z250 and Filtek Z350 XT Flowable [Z350F]), whereas four were bulk-fill composites (SonicFill, Tetric N-Ceram Bulk-Fill, SureFil SDR Flow [SDR], and Filtek Bulk-Fill). One hundred eighty aluminum molds simulating a mesio-occluso-distal cavity (6 W×8 L×4 D mm) were prepared and classified into three groups with mold wall thicknesses of 1, 2, and 3 mm. Each group was further subdivided according to the composite layering method (bulk or incremental layering). Linear variable differential transformer probes were used to measure the mold wall deflection of each composite (n=5) over a period of 2000 seconds (33.3 minutes). The polymerization shrinkage, flexural modulus, and polymerization shrinkage stress of the six composites were also measured. All groups with bulk filling exhibited significantly higher deflection compared with groups with incremental layering. The deflection decreased as mold wall thickness increased. The highest and lowest polymerization shrinkage stresses were recorded for Z350F (5.07 MPa) and SDR (1.70 MPa), respectively. The correlation between polymerization shrinkage and the mold wall deflection decreased with increasing wall thickness. On the other hand, the correlation between flexural modulus and the mold wall deflection increased with increasing wall thickness. For all groups, wall deflection correlated strongly with polymerization shrinkage stress.

Repairability of CAD/CAM high-density PMMA- and composite-based polymers.

The study aimed to analyse the shear bond strength of computer-aided design and computer-aided manufacturing (CAD/CAM) polymethyl methacrylate (PMMA)- and composite-based polymer materials repaired with a conventional methacrylate-based composite after different surface pretreatments. Each 48 specimens was prepared from six different CAD/CAM polymer materials (Ambarino high-class, artBloc Temp, CAD-Temp, Lava Ultimate, Telio CAD, Everest C-Temp) and a conventional dimethacrylate-based composite (Filtek Supreme XTE, control) and aged by thermal cycling (5000 cycles, 5-55 °C). The surfaces were left untreated or were pretreated by mechanical roughening, aluminium oxide air abrasion or silica coating/silanization (each subgroup n = 12). The surfaces were further conditioned with an etch&rinse adhesive (OptiBond FL) before the repair composite (Filtek Supreme XTE) was adhered to the surface. After further thermal cycling, shear bond strength was tested, and failure modes were assessed. Shear bond strength was statistically analysed by two- and one-way ANOVAs and Weibull statistics, failure mode by chi(2) test (p ≤ 0.05). Shear bond strength was highest for silica coating/silanization > aluminium oxide air abrasion = mechanical roughening > no surface pretreatment. Independently of the repair pretreatment, highest bond strength values were observed in the control group and for the composite-based Everest C-Temp and Ambarino high-class, while PMMA-based materials (artBloc Temp, CAD-Temp and Telio CAD) presented significantly lowest values. For all materials, repair without any surface pretreatment resulted in adhesive failures only, which mostly were reduced when surface pretreatment was performed. Repair of CAD/CAM high-density polymers requires surface pretreatment prior to adhesive and composite application. However, four out of six of the tested CAD/CAM materials did not achieve the repair bond strength of a conventional dimethacrylate-based composite. Repair of PMMA- and composite-based polymers can be achieved by surface pretreatment followed by application of an adhesive and a conventional methacrylate-based composite.

Mechanical and physical properties of silorane and methacrylate-based composites

ObjectivesThis study measured the degree of conversion (DC), sorption, solubility and microhardness of methacrylate (Filtek Z250 and Filtek Z350XT) and silorane-based composites (Filtek P90). MethodsDC was measured using near infrared spectroscopy immediately and 24h after the photoactivation. Sorption and solubility measurements were performed after 24h, 4 weeks and 12 weeks of storage in water. Knoop microhardness was measured after 24h and after thermal cycling. The data were statistically analyzed using ANOVA followed by Tukey's, Tamhane or paired t-tests (α=0.05). ResultsThe DC for P90 (37.22±1.46) was significantly lower than the Z250 (71.44±1.66) and Z350 (71.76±2.84). Water sorption was highest in the Z250 and lowest in the P90. All the tested composites exhibited similar values after 24h of immersion, and no significant differences were observed. No significant differences were observed between the solubilities of the P90 composite (12 weeks) and the Z250 or Z350 composites (4 weeks). KHN values were less elevated for the P90 composite and similar for the Z250 and Z350 composites. An effect of thermal cycling on KHN values was observed for all the composites (p<0.001). ConclusionsSilorane produced the lowest DC and KHN values and exhibited lower water sorption and solubility compared to methacrylate-based composites. These differences suggest that silorane composites exhibit better hydrolytic stability after 3 months of water immersion compared to conventional methacrylate-based composites. Clinical significanceSilorane had higher hydrolytic stability after 3 months of water immersion than the methacrylate-based resins, despite the lower values of DC and KHN recorded.

A new method to measure the polymerization shrinkage kinetics of composites using a particle tracking method with computer vision

Objectives The aim of this study was to develop a new method to measure the polymerization shrinkage of light cured composites and to evaluate the overall utility and significance of the technique. Methods An optical instrument to measure the linear polymerization shrinkage of composites without directly contacting the specimen was developed using a particle tracking method with computer vision. The measurement system consisted of a CCD color video camera, a lens, an image storage device, and image processing and analysis software. The shrinkage kinetics of a commercial silorane-based composite (P90) and two conventional methacrylate-based composites (Z250 and a flowable Z350) were investigated and compared with the data measured using the “bonded disc method”. Results The linear shrinkage of the composites was 0.33–1.41%. The shrinkage value was lowest for the silorane-based (P90) composite and highest for the flowable Z350 composite. The estimated volume shrinkages of the materials were comparable to the axial shrinkages measured with the bonded disc method. Significance The new instrument was able to measure the true linear shrinkage of composites without sensitivity to the specimen geometry and the viscosity of the material. Therefore, this instrument can be used to characterize the shrinkage kinetics for a wide range of commercial and experimental visible-light-cure materials in relation to the composition and chemistry.

Shrinkage properties of a modified dental resin composites containing a novel spiro-orthocarbonate expanding monomer

Objectives This study investigated the photopolymerization-induced shrinkage properties of conventional methacrylate-based composites modified by a novel spiro-orthocarbonate (SOC) expanding monomer. Methods The epoxy monomer and SOC expanding monomer were added to a methacrylate-based resin matrix at five different ratios ranging from 20 wt.% (SOC + Epoxy) (group 1) to 60 wt.% (SOC + Epoxy) (group 5). Volumetric shrinkage and contraction stress developing after polymerization were measured using X-ray micro-computed tomography and a universal testing machine, respectively. Results The volumetric shrinkage of the resin composite samples ranged from 0.92% (group 5) to 3.85% (control group) 30 min after light curing. Group 5 had the lowest volumetric shrinkage ( p < 0.05), followed by groups 4, 3, 2 and 1. The contraction stress of the materials ranged from 1.86 MPa (group 5) to 3.56 MPa (control group). The lowest contraction stress was also observed in group 5, 30 min after curing ( p < 0.05). Conclusion Including SOC expanding monomer reduced volumetric shrinkage and contraction stress of composites in comparison with conventional methacrylate-based composites.

Evaluation of polymerization shrinkage stress in silorane-based composites

Objectives: The purpose of this study was to evaluate the polymerization shrinkage stress among conventional methacrylate-based composite resins and a silorane-based composite resin. Materials and Methods: The strain gauge method was used for the determination of polymerization shrinkage strain. Specimens were divided by 3 groups according to various composite materials. Filtek Z-250 (3M ESPE) and Filtek P-60 (3M ESPE) were used as a conventional methacrylate-based composites and Filtek P-90 (3M ESPE) was used as a silorane-based composites. Measurements were recorded at each 1 second for the total of 800 seconds including the periods of light application. The results of polymerization shrinkage stress were statistically analyzed using One way ANOVA and Tukey test (p = 0.05). Results: The polymerization shrinkage stress of a silorane-based composite resin was lower than those of conventional methacrylate-based composite resins (p 0.05). Conclusions: Within the limitation of this study, silorane-based composites showed lower polymerization shrinkage stress than methacrylate-based composites. We need to investigate more into polymerization shrinkage stress with regard to elastic modulus of silorane-based composites for the precise result.

Investigating filler morphology and mechanical properties of new low-shrinkage resin composite types

Three types of low-shrinkage composites are today commercially available: Ormocers, cationic ring-opening curing systems and highly filled methacrylate-based materials, which cure via free-radical polymerization mechanisms. The aim of this study was to characterize the inorganic fraction of materials belonging to each type and to compare their mechanical properties. Two Ormocers (Admira and an experimental Ormocer V35694), one ring-opening composite (Filtek Silorane) and five methacrylate-based composites [Filtek Supreme XT, Tetric EvoCeram, Grandio, Synergy D6 (Coltène-Whaledent, Langenau, Germany) and an experimental material, V34930] were tested. Inorganic fillers were quantified by thermogravimetric analysis and morphologically characterized by scanning electron microscopy. Dynamic modulus was determined by an impulse excitation technique, static elastic moduli and flexural strength by a three-point bending method. The results were analyzed using ANOVA tests (P < 0.05) and linear correlations. Grandio, V34930 and V35694 exhibited significantly higher filler mass fractions. Both dynamic and static moduli of Grandio and V34930 were significantly higher than the other materials (P < 0.05), although no significant difference in flexural strength was observed between material type (P > 0.05). From the present findings, it was suggested that V35694 and Filtek Silorane exhibit comparable properties to conventional methacrylate-based composites, although clinically the cavity type and location must guide material choice. Under high occlusal load, the use of Grandio and V34930 might be favoured. For small cavities, alternative technologies could be preferred as the need for mechanical resistance is lower and the potential for stress generation is greater.

Polymerization shrinkage kinetics of silorane-based composites

Dental composites have improved significantly in physical properties over the past few decades. However, polymerization shrinkage and stress is still the major drawback of composites, limiting its use to selected cases. Much effort has been made to make low shrinking composites to overcome this issue and silorane-based composites have recently been introduced into the market. The aim of this study was to measure the volumetric polymerization shrinkage kinetics of a silorane-based composite and compare it with conventional methacrylate-based composites in order to evaluate its effectiveness in reducing polymerization shrinkage. Five commercial methacrylate-based (Beautifil, Z100, Z250, Z350 and Gradia X) and a silorane-based (P90) composites were investigated. The volumetric change of the composites during light polymerization was detected continuously as buoyancy change in distilled water by means of Archemedes' principle, using a newly made volume shrinkage measurement instrument. The null hypothesis was that there were no differences in polymerization shrinkage, peak polymerization shrinkage rate and peak shrinkage time between the silorane-based composite and methacrylate-based composites. The results were as follows: 1. The shrinkage of silorane-based (P90) composites was the lowest (1.48%), and that of Beautifil composite was the highest (2.80%). There were also significant differences between brands among the methacrylate-based composites. 2. Peak polymerization shrinkage rate was the lowest in P90 (0.13%/s) and the highest in Z100 (0.34%/s). 3. The time to reach peak shrinkage rate of the silorane-based composite (P90) was longer (6.7 s) than those of the methacrylate-based composites (2.4-3.1 s). 4. Peak shrinkage rate showed a strong positive correlation with the product of polymerization shrinkage and the inverse of peak shrinkage time (R = 0.95).

A new method to measure the linear polymerization shrinkage of composites using a particle tracking method with computer vision

Since the introduction of restorative dental composites, their physical properties have been significantly improved. However, polymerization shrinkage is still a major drawback. Many efforts have been made to develop a low shrinking composite, and silorane-based composites have recently been introduced into the market. In addition, many different methods have been developed to measure the polymerization shrinkage. In this study, we developed a new method to measure the linear polymerization shrinkage of composites without direct contact to a specimen using a particle tracking method with computer vision. The shrinkage kinetics of a commercial silorane-based composite (P90) and two conventional methacrylate-based composites (Z250 and Z350) were investigated and compared. The results were as follows: 1. The linear shrinkage of composites was 0.33-1.41%. Shrinkage was lowest for the silorane-based (P90) composite, and highest for the flowable Z350 composite. 2. The new instrument was able to measure the true linear shrinkage of composites in real time without sensitivity to the specimen preparation and geometry. [J Kor Acad Cons Dent 35(3):180-187, 2010]

Does a low-shrinking composite induce less stress at the adhesive interface?

Objectives Polymerization shrinkage of a composite in a high configuration-factor (C-factor) cavity leads to polymerization shrinkage stress. In the prevention of high polymerization shrinkage stress, a low-shrinking silorane composite (Filtek Silorane, FS, 3M ESPE) was recently marketed. Therefore, we investigated the effect of C-factor (flat surface vs. class-I cavity) and different composite application protocols on the bonding effectiveness of a low-shrinking composite to human dentin. Methods A low-shrinking silorane-based composite (FS) and a conventional methacrylate-based composite (Filtek Z100, 3 M-ESPE) were bonded to standardized occlusal class-I cavities (4 mm × 4 mm × 2.5 mm) and to flat mid-coronal dentin surfaces using the two-step self-etch adhesive ‘Silorane System Adhesive’ (3 M-ESPE). Eight experimental groups were formed, according to the following treatment protocols: Z100 ‘flat’(1), Z100 ‘cavity’(2), FS ‘flat’(3), FS ‘flat/bulk-filled’(4), FS ‘cavity/bulk-filled’(5), FS ‘cavity/layered-filled’(6), FS ‘cavity/flowable cured’(7) and FS ‘cavity/flowable uncured’(8). For each group, at least 5 teeth were used. After 1 week of water storage, the teeth were sectioned to 1 mm × 1 mm (non-trimmed) sticks to measure the micro-tensile bond strength (μTBS). Results No statistical difference in μTBS was recorded between Z100 ‘flat’(1) and FS ‘flat’(3). Bonding to class-I cavity dentin lowered the μTBS in all groups, but this was only statistically significant for FS ‘cavity/bulk-filled’(5) and FS ‘cavity/flowable uncured’(8). Significance Using the two-step self-etch Silorane System Adhesive, the conventional composite Filtek Z100 and the low-shrinking composite Filtek Silorane bonded equally well to dentin. Bulk-filling with Filtek Silorane (FS ‘flat/bulk-filled’(4)) significantly decreased the μTBS, suggesting that factors other than polymerization shrinkage influenced the μTBS.

Oxygen inhibition and incremental layer bond strengths of resin composites

Objectives When dentists light cure resin composite restorations in increments or after contouring the surface layer to shape with a hand instrument the surface layer is exposed to air during polymerization. The presence of an oxygen inhibited resin surface layer may impact on clinical performance. Conflicting data has been produced in vitro regarding this topic. Methods To shed further light on this subject the current investigation assessed the thickness of the oxygen inhibited layer (OIL) and subsequent interfacial bond strength at various times post-cure of an “initial increment” for a range of experimental and commercial resin composites. The latter included conventional methacrylate-based composites and a novel low shrink Silorane resin chemistry product. Results A decrease in composite viscosity brought about by an increase in diluent monomer content in the matrix for the experimental composite formulations led to increase in OIL thickness. The OIL surface layer thickness for the commercial methacrylate-based RBC specimens cured in air were 19.2 ± 6.3 and 13.8 ± 5.3 μm, respectively and 9.0 ± 6.6 μm for Silorane. No test material exhibited a measurable OIL thickness polymerized in the nitrogen atmosphere. Significance From the current findings it may be concluded that incremental bond strength is not wholly reliant on surface inhibition since no differences in bond strength following immediate placement were observed between air and nitrogen atmosphere for any experimental or commercial material. For large restorations requiring multiple increments which are placed on fresh material, the bond strength between successive layers of Silorane should be no different to conventional methacrylate materials. Repair and bonding to aged Silorane restorations may be more problematic as inferior incremental bond strengths ensued when addition was delayed.

5527130 Environmentally safe underground piping system: Webb Michael C, Chester Springs, PA, United States assigned to Environ Products Inc

Polymerization shrinkage of a composite in a high configuration-factor (C-factor) cavity leads to polymerization shrinkage stress. In the prevention of high polymerization shrinkage stress, a low-shrinking silorane composite (Filtek Silorane, FS, 3M ESPE) was recently marketed. Therefore, we investigated the effect of C-factor (flat surface vs. class-I cavity) and different composite application protocols on the bonding effectiveness of a low-shrinking composite to human dentin.A low-shrinking silorane-based composite (FS) and a conventional methacrylate-based composite (Filtek Z100, 3 M-ESPE) were bonded to standardized occlusal class-I cavities (4 mm × 4 mm × 2.5 mm) and to flat mid-coronal dentin surfaces using the two-step self-etch adhesive ‘Silorane System Adhesive’ (3 M-ESPE). Eight experimental groups were formed, according to the following treatment protocols: Z100 ‘flat’(1), Z100 ‘cavity’(2), FS ‘flat’(3), FS ‘flat/bulk-filled’(4), FS ‘cavity/bulk-filled’(5), FS ‘cavity/layered-filled’(6), FS ‘cavity/flowable cured’(7) and FS ‘cavity/flowable uncured’(8). For each group, at least 5 teeth were used. After 1 week of water storage, the teeth were sectioned to 1 mm × 1 mm (non-trimmed) sticks to measure the micro-tensile bond strength (μTBS).No statistical difference in μTBS was recorded between Z100 ‘flat’(1) and FS ‘flat’(3). Bonding to class-I cavity dentin lowered the μTBS in all groups, but this was only statistically significant for FS ‘cavity/bulk-filled’(5) and FS ‘cavity/flowable uncured’(8).Using the two-step self-etch Silorane System Adhesive, the conventional composite Filtek Z100 and the low-shrinking composite Filtek Silorane bonded equally well to dentin. Bulk-filling with Filtek Silorane (FS ‘flat/bulk-filled’(4)) significantly decreased the μTBS, suggesting that factors other than polymerization shrinkage influenced the μTBS.