Progress in dimethacrylate-based dental composite technology and curing efficiency

The study aimed to assess the mechanical performance of seven bulk-fill RBCs (Venus Bulk Fill, Heraeus Kulzer; SureFil SDR flow, Dentsply Caulk; x-tra base and x-tra fil, VOCO; Filtek Bulk Fill, 3M ESPE; SonicFill, Kerr; Tetric EvoCeram Bulk Fill, Ivoclar Vivadent) by determining their flexural strength (σ), reliability (Weibull parameter, m), flexural modulus (Eflexural), indentation modulus (YHU), Vickers hardness (HV), and creep (Cr). The significant highest flexural strengths were measured for SonicFill, x-tra base, and x-tra fil, while x-tra base, SureFil SDR flow, and Venus Bulk Fill showed the best reliability. The differences among the materials became more evident in terms of Eflexural and YHU, with x-tra fil achieving the highest values, while Filtek Bulk Fill and Venus Bulk Fill achieved the lowest. The enlarged depth of cure in bulk-fill RBCs seems to have been realized by enhancing the materials' translucency through decreasing the filler amount and increasing the filler size. The manufacturer's recommendation to finish a bulk-fill RBC restoration by adding a capping layer made of regular RBCs is an imperative necessity, since the modulus of elasticity and hardness of certain materials (SureFil SDR flow, Venus Bulk Fill, and Filtek Bulk Fill) were considerably below the mean values measured in regular nanohybrid and microhybrid RBCs. The class of bulk-fill RBCs revealed similar flexural strength values as the class of nanohybrid and microhybrid RBCs, and significantly higher values when compared to flowable RBCs. The modulus of elasticity (Eflexural), the indentation modulus (YHU), and the Vickers hardness (HV) classify the bulk-fill RBCs as between the hybrid RBCs and the flowable RBCs; in terms of creep, bulk-fill and the flowable RBCs perform similarly, both showing a significantly lower creep resistance when compared to the nanohybrid and microhybrid RBCs.

Bulk-fill resin-based composites: an in vitro assessment of their mechanical performance.

The aim of this study was to quantify the blue light that passes through different incremental thicknesses of bulk fill in comparison to conventional resin-based composites (RBCs) and to relate it to the induced mechanical properties. Seven bulk fill, five nanohybrid and two flowable RBCs were analysed. Specimens (n = 5) of three incremental thicknesses (2, 4 and 6 mm) were cured from the top for 20 s, while at the bottom, a spectrometer monitored in real time the transmitted irradiance. Micro-mechanical properties (Vickers hardness, HV, and indentation modulus, E) were measured at the top and bottom after 24 h of storage in distilled water at 37 °C. Electron microscope images were taken for assessing the filler distribution and size. Bulk fill RBCs (except SonicFill) were more translucent than conventional RBCs. Low-viscosity bulk fill materials showed the lowest mechanical properties. HV depends highly on the following parameters: material (ηp
 2 = 0.952), incremental thickness (0.826), filler volume (0.747), filler weight (0.746) and transmitted irradiance (0.491). The bottom-to-top HV ratio (HVbt) was higher than 80 % in all materials in 2- and 4-mm increments (except for Premise), whereas in 6-mm increments, this is valid only in four bulk fill materials (Venus Bulk Fill, SDR, x-tra fil, Tetric EvoCeram Bulk Fill). The depth of cure is dependent on the RBC’s translucency. Low-viscosity bulk fill RBCs have lower mechanical properties than all other types of analysed materials. All bulk fill RBCs (except SonicFill) are more translucent for blue light than conventional RBCs. Although bulk fill RBCs are generally more translucent, the practitioner has to follow the manufacturer’s recommendations on curing technique and maximum incremental thickness.

Light transmittance and micro-mechanical properties of bulk fill vs. conventional resin based composites.

http://pure-oai.bham.ac.uk/ws/files/17851121/Palin_Physico_mechanical_characteristics_Journal_Dentistry_2014.pdf

Physico-mechanical characteristics of commercially available bulk-fill composites.

Clinical Relevance While achieving adequate curing at 4-mm thicknesses, not all bulk-fill composites are characterized by low-shrinkage stress. Clinicians should be cautious with these material selections for high C-factor applications.

Polymerization Shrinkage Stress Kinetics and Related Properties of Bulk-fill Resin Composites

Objectives
The aim of our study was to measure and compare degree of conversion (DC) as well as micro- (indentation modulus, E; Vickers hardness, HV) and macromechanical properties (flexural strength, σ; flexural modulus, Eflexural) of two recently launched bulk fill resin-based composites (RBCs): Surefil® SDR™ flow (SF) and Venus® bulk fill (VB).

In vitro comparison of mechanical properties and degree of cure of bulk fill composites

Purpose To compare a self-adhesive with two low-shrinkage and two regular flowable resin-based composites (RBCs) in terms of degree of conversion (DC) as well as micromechanical (indentation modulus [E]; Vickers hardness [HV]) and macromechanical properties (flexural strength [σ], modulus of elasticity [Eflexural]) Materials and methods DC was investigated by an ATR-FTIR spectrometer at clinically relevant filling depths (01 mm, 2 mm, 4 mm, 6 mm bulk, 6 mm incremental) and irradiation times (10 s, 20 s, 40 s) Micro- and macromechanical properties were measured with an automatic microhardness indenter and a three-point bending test device after curing the specimens for 20 s and storing them in distilled water for 24 h at 37°C Fillers were visualized using a field emission scanning electron microscope (FE-SEM) Results were evaluated using one-way ANOVA, Tukey's HSD post-hoc test, Pearson's correlation and a multivariate analysis (α = 005) A Weibull analysis was used to assess σ Results N'Durance Dimer flow (6566%) reached the highest DC (at 2 mm depth, 20 s irradiation) In terms of macromechanical properties, EcuSphere-Flow (12982 MPa) for σ and Synergy D6 Flow (374 GPa) for Eflexural reached the highest values The highest micromechanical properties were measured for the self-adhesive RBC (Vertise Flow; E = 1081 GPa, HV = 6020 N/mm2) Reliability was highly influenced by filler weight (η2 = 077) and volume (η2 = 099) proportion Conclusion In the present study, the self-adhesive RBC showed the highest reliability, highest DC (together with one of the low-shrinkage RBCs), and highest micromechanical properties as well as good macromechanical properties Moreover, a curing time of 40 s and an incremental thickness not exceeding 2 mm appeared to be necessary for such results

Pascal Czasch

Papers

In vitro comparison of mechanical properties and degree of cure of bulk fill composites

In vitro comparison of mechanical properties and degree of cure of a self-adhesive and four novel flowable composites