Low-viscosity Bulk-fill Composites Research Articles

Comparison of the microhardness of lowviscosity bulk-fill composite resins

The aim of this study is to compare the microhardness of five different low-viscosity bulk-fill composites. The bulk-fill composites used in the study; Estelite Bulk-fill flow (EBF), Filtek Bulk-fill (FBF), SureFil SDR flow (SDR), Tetric EvoFlow Bulk fill (TEFBF), X-tra Base (XBF). Cylindrical molds with a diameter of 5 mm and a height of 4 mm were used for the Vicker's Micro Hardness (VMH) test. Bulk-fill composite resins were placed in these molds at once. The polymerization of the composites was achieved for 20 seconds with the LED light curing. A total of 50 composite discs were prepared (n=10). Then the microhardness of the top and bottom surfaces was measured using MVK-H1 Microhardness Tester (Akashi Co, Tokyo, Japan. Depth of polymerization of each sample was recorded. Data were analyzed by using the Kruskal Wallis H and Mann Whitney-U tests. The bottom and top surface hardness values of the XBF composite samples (43.82±0.95 MPa, 47.87±0.59 MPa) were statistically significantly higher than the other bulk-fill composite samples (p<0.001). The bottom and top surface hardness values of the FBF composite (27.85±0.56 MPa, 22.05±1.40 MPa) were found to be statistically lower than other bulk-fill composite samples (p<0.001). Among the low-viscosity bulk-fill composites used in the study, except for FBF, the VMH values of the others were found to be above 0.80, and it was observed that they reached sufficient microhardness.

Bulk-flow composites in paediatric dentistry: long term survival of posterior restorations. A retrospective study.

Dental decay is a prevalent bacterial disease affecting a significant percentage of children globally. In paediatric dentistry, various materials are available for restoring deciduous teeth, addressing both functional and aesthetic concerns. However, paediatric dentists encounter challenges related to patient compliance, limited working time, and material handling. This study aims to observe the survival rate of bulk-fill composite restorations in paediatric patients over a five-year follow-up. A total of 198 patients aged 0 to 12 years underwent 673 class II restorations on deciduous first molars (1M) and second molars (2M). All restorations were conducted performed by 1 Pediatric DDS resident students from the Paediatric Dentistry Department (Padova University), utilizing using different isolation techniques. Bulk-fill composite restorations were evaluated over a five-year follow-up, and data were collected by a single investigator. After five years, 177 patients and 611 restorations were assessed. The retention rate was higher in primary second molars than in first molars, with fewer marginal dyschromies and less formation of secondary caries. The overall failure rate was higher in primary first molars and primary lower second molars. Bulk-fill composites demonstrated significantly positive performance in terms of retention, maintenance, and marginal dyschromies. Bulk-fill composites are promising materials of choice in paediatric dentistry due to their easy handling and favorable properties. Further research is necessary to compare high and low viscosity bulk-fill composites and assess the impact of different variables on restoration success.

Effect of Rapid Polymerization on Water Sorption and Solubility of Bulk-fill Composites.

The aim of the study was to examine the impact of rapid high-intensity polymerization on water sorption and solubility of a new generation of bulk-fill composite materials. Five materials were tested: a conventional composite Filtek Z250 (3M, St. Paul, USA) and four bulk-fill composites, Filtek One Bulk Fill (3M), Tetric PowerFill (Ivoclar Vivadent, Schaan, Liechtenstein), Tetric PowerFlow (Ivoclar Vivadent), SDR Plus (Dentsply, Konstanz, Germany). Composite specimens with a 9-mm diameter and a 2-mm height (n = 6) were polymerized with a high-intensity curing unit (Bluephase® PowerCure, Ivoclar Vivadent). The control group was polymerized for a total of 40 s on both sides (1193 mW / cm2) and 3s group for 3 s on one side (3053 mW/cm2). Water sorption and solubility were measured by ISO 4049 method up to 30 days of immersion. The results were statistically analyzed using one-way ANOVA with Tukey post-hoc correction. Different polymerization protocols for the same material were compared by t-test (p <0.05). The 3s polymerization protocol increased the solubility of all materials. Filtek One Bulk Fill showed the highest water sorption and solubility values, and Tetric PowerFlow proved to be a stable material with low values of tested parameters. During immersion, a saturation of specimens was achieved in low-viscosity bulk-fill composites within two weeks, while in other materials it was not achieved within 30 days, or more, following the immersion. Rapid polymerization caused an increase in solubility, which could affect the biocompatibility of the investigated materials not intended for the 3s curing. SDR Plus and Filtek One Bulk Fill should not be polymerized with rapid high-intensity curing due to increased solubility that exceeds ISO 4049:2009 limits.

Mechanical properties of low and regular viscosity bulk fill composites in a 3D dentin cavity model

This study aimed to evaluate the depth of cure (DC), bond strength (BS), failure mode (FM) and nanoleakage (NL) of restorative systems containing low viscosity bulk fill, regular viscosity bulk fill and conventional composites in a 3 D dentin cavity model. Six restorative systems: [Adhesive: Ambar Universal/Composite resins: Opus Bulk Fill Flow – OBFF, Opus Bulk Fill – OBF and Liss (FGM)] and [Adhesive: Scotchbond Universal/Composite resins: Filtek Bulk Fill Flow – FBF, Filtek Bulk Fill – FB, and Filtek Z250 XT – XT (3 M ESPE)] were used. Conical cavities (n = 13) were prepared in bovine dentin and restored with composite. The DC (%) was analyzed calculating just the bottom-to-top microhardness ratio. The BS (MPa) was determined by push-out testing in the universal testing machine and the FM was analyzed using a stereomicroscope. The NL of silver nitrate was mapped using SEM images of the adhesive interface in additional specimens (n = 3). Data were analyzed using one-way ANOVA/Tukey tests (α = 0.05). There were no statistically significant differences for the DC of the restorative systems. OBFF (11 ± 0.42) presented the highest mean of BS (MPa), while FB (2.61 ± 0.80) showed the lowest mean. Adhesive failures (86%) were predominant. The NL expression was visually similar among the restorative systems. All restorative systems seem to be able to obtain proper cure in 3D dentin cavity model. However, low viscosity bulk fill composites might improve the quality of restorations and provide better clinical longevity.

Evaluation of low-viscosity bulk-fill composites regarding marginal and internal adaptation

This study aimed at evaluating the marginal and internal adaptation of low-viscosity bulk-fill composites to enamel and dentin using a self-etch or an etch-and-rinse adhesive without and with artificial ageing. Hundred and twenty-eight MOD cavities in extracted molars were assigned to eight groups (n = 16), restored with the adhesives OptiBond FL (OFL) or Xeno V+ (X) and two low-viscosity bulk-fill composites SDR or x-tra base, covered with Premise. Tetric EvoCeram Bulk Fill and Premise served as a control. n = 8 per group were subjected to prolonged water storage (180 days) and thermocycling (2500×). Scanning electron microscopy was used to determine marginal gaps (MG) and interfacial adhesive defects (IAD). There were no significant differences between composite types in 44 out of 48 (MG) or 43/48 (IAD) comparisons. More MG were observed with X than with OFL (14 out of 16 comparisons, two significant), while in 16 of 16 comparisons with X more IAD were observed (14 significant). After artificial ageing, MG generally increased (9/16 significant), compared to IAD (one significant). The performance of the investigated composite types concerning the integrity of the tooth-composites interface was comparable. Compared to the 1-step self-etch system, the bond with the 3-step etch-and-rinse adhesive was raised.

The use of a liner under different bulk-fill resin composites: 3D GAP formation analysis by x-ray microcomputed tomography.

Gap formation of composite resin restorations is a serious shortcoming in clinical practice. Polymerization shrinkage stress exceeds the tooth-restoration bond strength, and it causes bacterial infiltration within gaps between cavity walls and the restorative material. Thus, an intermediate liner application with a low elastic modulus has been advised to minimize polymerization shrinkage as well as gap formation.Objective:The purpose of this in vitro study was to assess gap formation volume in premolars restored with different bulk-fill composites, with and without a resin-modified glass-ionomer cement (RMGIC) liner, using x-ray micro-computed tomography (micro-CT).Methodology:Sixty extracted human maxillary premolars were divided into six groups according to bucco-palatal dimensions (n=10). Standardized Class II mesio-occluso-distal cavities were prepared. G-Premio Bond (GC Corp., Japan) was applied in the selective-etch mode. Teeth were restored with high-viscosity (Filtek Bulk Fill, 3M ESPE, USA)-FB, sonic-activated (SonicFill 2, Kerr, USA)-SF and low viscosity (Estelite Bulk Fill Flow, Tokuyama, Japan)-EB bulk-fill composites, with and without a liner (Ionoseal, Voco GmbH, Germany)-L. The specimens were subjected to 10,000 thermocycles (5-55°C) and 50,000 simulated chewing cycles (100 N). Gap formation based on the volume of black spaces at the tooth-restoration interface was quantified in mm3 using micro-computed tomography (SkyScan, Belgium), and analyses were performed. Data were analyzed using repeated-measures ANOVA and the Bonferroni correction test (p < 0.05).Results:The gap volume of all tested bulk-fill composites demonstrated that Group SF (1.581±0.773) had significantly higher values than Group EB (0.717±0.679). Regarding the use of a liner, a significant reduction in gap formation volume was observed only in Group SFL (0.927±0.630) compared with Group SF (1.581±0.773).Conclusion:It can be concluded that different types of bulk-fill composite resins affected gap formation volume. Low-viscosity bulk-fill composites exhibited better adaptation to cavity walls and less gap formation than did sonic-activated bulk-fill composites. The use of an RMGIC liner produced a significant reduction in gap formation volume for sonic-activated bulk-fill composites.

Influence of Bulk-Fill Composites, Polimerization Modes, and Remaining Dentin Thickness on Intrapulpal Temperature Rise

Objectives The aim of this study was to compare the effects of different bulk-fill resin composites, polimerization modes, and the thickness of remaining dentin on the increase of intrapulpal temperature. Methods Human-extracted upper premolar teeth (n = 10) were used to design a single-tooth model with remaining dentin thicknesses of 1 mm and 0.5 mm. Estelite Bulk-fill Flow (Tokuyama, Japan), Surefil SDR™ Flow (Dentsply Caulk, Brazil), Filtek Bulk-Fill Posterior (3M, USA), and SonicFill™ 2 Bulk-fill (Kerr, USA) composites were applied according to the manufacturer's instructions. The standard and high modes of a light emitted diode (LED) light curing unit (LCU) (VALO™ Utradent, USA), were used for polymerization. In order to mimic the in vivo conditions of pulpal circulation, digital flowmetry (SK-600II, SK Medical, China) was used. Intrapulpal temperature rise was measured using K type thermocoupling (CEM DT 610B, Robosem Engineering, China). Data were analyzed using three-way variance analysis (ANOVA) and the independent t-test. Results No significant statistical differences in intrapulpal temperature rise between low viscosity bulk-fill composites (SDR and Estelite) were found. The lowest intrapulpal temperature rise was found in groups which used the Filtek Bulk-fill composite. Decreases in the remaining dentin thickness increased the intrapulpal temperature rise. Significance This study demonstrated that remaining dentin thickness, filler ratio of bulk-fill composites, and power and application time of the LED-LCU may affect intrapulpal temperature rise.

Mechanical properties of bulk-fill versus nanohybrid composites: effect of layer thickness and application protocols

Objective: The objective of this study was to evaluate the compressive strength, flexural strength and flexural modulus of high-viscosity, low-viscosity bulk-fill, and conventional nano-hybrid resin composite materials alone and when covered with nano-hybrid resin composite at different incremental thicknesses on the bulk-fill composites. Materials and Methods: Specimens (N=60) were fabricated from the following materials or their combinations (n=10 per group): a) conventional nano-hybrid composite Z550 (FK), b) high-viscosity bulk-fill composite (Tetric N Ceram-TBF), c) low-viscosity bulk-fill composite SDR (SDR), d) Sonicfill (SF), e) SDR (2 mm)+FK (2 mm), f) SDR (4 mm)+FK (4 mm). After 24 h water storage, compressive strength was measured in a universal testing machine (1 mm/min). Additional specimens (N=40) (25x2x2 mm3) were made from FK, TBF, SDR and SF in order to determine the flexural strength and the flexural modulus, (n=10) and subjected to three-point bending test (0.5 mm/min). Data were analyzed using one-way ANOVA and Tamhane’s T2 post-hoc tests (p&lt;0.05). Results: The mean compressive strength (MPa) of the nano-hybrid composite (FK) was significantly higher (223.8±41.3) than those of the other groups (123±27 - 170±24) (p&lt;0.001). SDR (4 mm)+FK (2 mm) showed significantly higher compressive strength than when covered with 4 mm (143±30) or when used alone (146±11) (p&lt;0.05). The mean flexural strength (159±31) and the flexural modulus of FK (34±7) was significantly higher than that of the high- or low-viscosity bulk-fill composites (p&lt;0.001). The mean flexural strength of SF (132±20) was significantly higher compared to TBF (95±25) (p&lt;0.05). Conclusion: Bulk-fill resin composites demonstrated poorer mechanical properties compared to nano-hybrid composite but similar to that of SF. Increasing the thickness of low-viscosity bulk-fill composite (SDR) from 2 to 4 mm underneath the nano-hybrid composite (FK) can improve the mechanical properties of the bulk-fill composites. KeywordsBulk-fill composites; Compressive strength; Flexural modulus; Flexural strength; Mechanical properties.

The comparative evaluation of depth of cure of bulk-fill composites - An in vitro study.

Introduction:Resin-based composites (RBCs), as restorative dental materials, have given a new dimension to conservative and esthetic dentistry. The objective of the present study is to evaluate and compare the depth of cure of RBC's for posterior use: Sculptable bulk-fill composite – Tetric N-Ceram bulk fill (TNCBF), Flowable bulk-fill composites-TetricEvoflow bulk fill (TEFBF), Surefil SDR bulk fill (SDRBF), Dual cure bulk fill-Fill-Up (FDCBF) with conventional RBC-Esthet-X flow (EXF) and Filtex Z250 (FZ).Materials and Methods:A standardized polyacrylic mold was bulk filled with each of the six composites and light-cured for 20 s, followed by 24 h storage in water. The surface hardness was measured on the top and the bottom by recording Vickers hardness number by Vickers hardness indenter.Results:The mean bottom surface hardness value (HV) of SDR and TEFBF exceeded 80% of the top surface HV (HV-80%). Low viscosity bulk-fill composites (SDR and Tetric Evoflow) were properly cured in 4-mm increments. The TNCBF, high-viscosity composite, and Fill-Up, dual-cure bulk fill were not sufficiently cured in 4-mm increments.Conclusion:With increase in incremental thickness, HV decreased for the conventional resin composite but generally remained constant for the bulk-fill resin composites.

Shrinkage stress of high and low viscosity bulk-fill composites with incremental and bulk fill techniques

Purpose Evaluate shrinkage stress of incremental and bulk filling techniques of high and low viscosity bulk fill nanohybrid resin-based composites (RBCs) by assessing cuspal deflection, microleakage, and gap formation. Flexural modulus of different RBCs was also studied. Patients and methods Eighty molars were divided into four groups according to the type of RBCs. Each group subdivided into two subgroups (n = 10) depending on application techniques; A: bulk fill and B: incremental filling. Buccal and palatal cuspal deflection was measured by strain gauge. All teeth were subjected to several steps to evaluate cervical microleakage% by Stereomicroscope. Scanning electron microscope was used to estimate gap formation%. Flexural modulus was measured by three-point bending test. Kruskal–Wallis's test was used for comparison of quantitative variables and post hoc test was used for multiple comparisons. χ2 test was used to test the qualitative data. P value less than or equal to 0.05 was considered statistically significant. Results Cuspal deflection: bulk filled teeth of low viscosity SDR flow (group III) and incremental filled teeth of the four groups were not significantly different from each other and were significantly lower than bulk filled teeth of high viscosity materials. Cervical microleakage%: the lowest scores were recorded in group II and group III which were not significantly different between both application techniques. Gap formation%: the two lowest means % were recorded for bulk filled teeth of group III and incremental filled teeth of group IV. There was a positive correlation between cuspal deflection, cervical microleakage% and gap formation%. Flexural modulus of group III was significantly lower than other groups which were not significantly different from each other. Conclusion Incremental filling technique was the best technique to decrease contraction stress and its complications. Bulk filling technique of low viscosity SDR achieved comparable results to incremental filling technique.

Polymerization shrinkage, modulus, and shrinkage stress related to tooth-restoration interfacial debonding in bulk-fill composites

ObjectivesThe aim of the present study was to measure the polymerization shrinkage, modulus, and shrinkage stress of bulk-fill and conventional composites during polymerization and to investigate the relationship between tooth-composite interfacial debonding and shrinkage stress of the composites. MethodsPolymerization shrinkage, dynamic modulus, and shrinkage stress of two high-viscosity bulk-fill (SonicFill (SF)/Tetric N-Ceram Bulk-Fill (TNB)) and two low-viscosity bulk-fill composites (Filtek Bulk-Fill (FB)/SureFil SDR Flow (SDR)) as well as one high-viscosity conventional (Filtek Z250 (Z250)) and one low-viscosity conventional composite (Filtek Z350 XT Flowable (Z350F)) were measured using custom-made instruments. Acoustic emission (AE) analysis was performed to evaluate the tooth-composite interfacial debonding during polymerization of the composites in Class 1 cavities on extracted third molars. ResultsThe low-viscosity composites exhibited higher shrinkage and lower modulus than the high-viscosity composites. Polymerization shrinkage at 10min ranged between 2.05% (SF) and 3.53% (Z350F). Polymerization shrinkage stress values at 10min ranged between 1.68MPa (SDR) and 3.51MPa (Z350F). The number of AE events was highest in Z350F and lowest in SDR. ConclusionsComposites that exhibited greater polymerization shrinkage stress generated more tooth-composite interfacial debonding. In contrast to similar outcomes among the high-viscosity composites (conventional: Z250, bulk-fill: TNB and SF), the low-viscosity bulk-fill composites (FB and SDR) demonstrated better results in terms of polymerization shrinkage stress and tooth-composite interfacial debonding than did the low-viscosity conventional composite (Z350F). Clinical significanceDespite the better performance by some of the bulk-fill composites, clinicians should be aware that the bulk-fill composites are not perfect substitutes for conventional composites.

Effect of different curing protocols on the mechanical properties of low-viscosity bulk-fill composites.

This study aimed to assess the impact of curing conditions-exposure time, mode, energy density and exposure distance-on the efficiency of curing flowable bulk-fill resin-based composites (RBCs) at simulated clinical relevant filling depths. Four flowable bulk-fill RBCs were investigated by assessing in 200 μm steps the variation in micro-mechanical properties (Vickers hardness (HV) and indentation modulus (E)) within simulated 6-mm-deep fillings (n = 5), considering 16 different curing modes/conditions. The exposure duration was 5, 20 and 40 s in the standard power mode; 3, 4 and 8 s in the high power mode; and 3 and 6 s in the plasma mode. Besides, the curing unit was placed at 0 and 7 mm distance away from the specimen's surface. Measurements were performed after 24 h of storage in distilled water at 37 °C. The depth of cure (DOC) was calculated as the 80 % hardness drop-off. The curing unit's irradiance at exposure distances up to 10 mm was monitored for all irradiation modes in 1 mm steps by means of a laboratory-grade spectrometer. Results were compared using one- and multiple way ANOVA and Tukey's honest significant difference (HSD) post hoc test (α = 0.05). A multivariate analysis (general linear model) assessed the effect strength of the parameters material, energy density reaching the specimen's surface (2.63 to 47.03 J/cm(2)), exposure distance and curing mode on HV, E and DOC. The effect of the parameter material was significant and strong on all measured properties (p < 0.05, partial eta-squared (η P (2)) = 0.683 for E, 0.724 for HV and 0.199 for DOC). Energy density exerted in all materials the strongest influence on the measured properties, while the influence of distance was strong on DOC and low or even not significant on HV and E. The susceptibility to variation in irradiance under the simulated clinical conditions was material dependent, while lower and upper energy density limits for curing the materials were defined. Materials react differently to the supplied irradiance. An exposure time of 20 s at moderate irradiance is recommended for all materials. The highest mechanical properties were reached not at the specimens' surface, but in deeper layers (0.4 to 3.1 mm).

Energy density limits for adequate curing in low-viscosity bulk-fill composites

Energy density limits for adequate curing in low-viscosity bulk-fill composites