Bulk-fill Resin-based Composites: An In Vitro Assessment of Their Mechanical Performance

Abstract

SUMMARY 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.

Influence of irradiation time on subsurface degree of conversion and microhardness of high-viscosity bulk-fill resin composites

“…KHN-values recorded in the present study were lower compared to those measured in other studies that analyzed microhardness of high-viscosity bulk-fill resin composites [6,13]. The lower hardness values might be due to the fact that, in order to avoid any heat production, the composite specimens were not ground or polished prior to hardness testing, so that measurements were performed on the specimens' resin-rich outer layer [54].…”

“…However, flowable bulk-fill resin composites require the placement of a final capping layer made of a regular composite material on top of the up to 4-mm-thick composite base, as a result of their low surface hardness and modulus of elasticity [13]. High-viscosity bulk-fill resin composites, in contrast, are indicated for use without veneering, and can thus be applied as true single-step bulk-fill materials.…”

“…High-viscosity bulk-fill resin composites, in contrast, are indicated for use without veneering, and can thus be applied as true single-step bulk-fill materials. Nevertheless, to date, very few studies concentrated on high-viscosity bulk-fill resin composites and examined their characteristics [6,[13][14][15], and only one study [16] used Fourier transform infrared spectroscopy (FTIR) to determine the DC of two representatives of nonflowable bulk-fill materials. To the knowledge of the authors, until now, there are no studies dealing with a systematic and thorough investigation on the influence of irradiation time and composite thickness on the DC of currently available high-viscosity bulk-fill resin composites.…”

Surface and bulk properties of dental resin- composites after solvent storage

“…These nano-hybrid materials showed a reduction of around 50% in 75% Ethanol/water and MEK after 90 days of storage except for TEC-BF that showed the least reduction in VHN among all the investigated materials after storage. TEC-BF besides having camphroquinone and amine photoinitiator system, it has an initiator booster (Ivocerin TM -a dibenzoyl germanium compound) that enables the material to polymerise in thicker increments (4 mm) [51,[63][64][65]. Having the initiator booster in their activation system could increase the cross linking density of the cured material leading to their high resistance to solvent degradation.…”

“…The deterioration of the interface between the matrix and the filler system together with the hydrophilicity of the monomer system could explain the reduced DTS values after solvents storage [15,57,60]. TEC-BF demonstrated more resistance to solvent degradation, which could be related to their enhanced photoinitiation system [51,63,66].…”