Shrinkage stress and elastic modulus assessment of bulk-fill composites

Abstract

Bulk-fill composites were introduced in dentistry to accelerate clinical procedures while providing adequate outcomes. Concerns regarding the use of bigger composite increments rely on the polymerization shrinkage and shrinkage stress, which may generate gaps on the adhesive interface and result in a reduced success rate. Objective: To evaluate the polymerization shrinkage stress of different bulk-fill resin composites and their elastic modulus. Materials and Methods: Fourteen specimens were made for each of the nine different resin composites (seven with 12 mm3 and seven with 24 mm3): Surefill SDR flow (SDR), X-tra Base (XB), Filtek Bulk Fill Flowable (FBF), Filtek Z350XT Flow (Z3F); Tetric Evo Ceram Bulk Fill (TBF), X-tra Fil (XF), Filtek Bulk Fill (FBP), Admira Xtra Fusion (ADM) and Filtek Z350 XT (Z3XT). Linear shrinkage stress was evaluated for 300 s with the aid of a linear shrinkage device adapted to a Universal Testing Machine. For each composite group, seven additional specimens (2x2x25 mm) were made and Young's modulus was evaluated with a 3-point bending device adapted in a Universal Testing Machine with 0.5 mm/min crosshead speed and 50 KgF loading cell. Results: For 12 mm3 specimens, three-way ANOVA showed that only SDR and TBF generated lower stress after 20 s. Considering 300 s, TBF, SDR, and XF generated the lowest stress, followed by ADM, FBP, XB, and FBF, which were similar to Z3XT. Z3F generated the highest stress values for all time points. Considering 24 mm3 specimens after 20 s, all bulk fill composites generated lower stress than Z3XT, except XB. After 300 s, SDR, FBP, and ADM generated the lowest stress, followed by TBF and XF. For elastic modulus, one-way ANOVA showed that FBF, SDR, Z3F, and ADM presented the lowest values, followed by XB and TBF. FBP, Z3XT, and XF presented the highest elastic modulus among the evaluated composites. Conclusions: Bulk-fill resin composites presented equal to lower shrinkage stress generation when compared to conventional composites, especially when bigger increments were evaluated. Bulk-fill composites showed a wide range of elastic modulus values, but usually similar to “regular” composites.

Effects of curing modes on depth of cure and microtensile bond strength of bulk fill composites to dentin

“…However, most recent studies report data related to the former formulation, compatible with the bulk fill composites used in our study. 5 , 6 , 39 , 40 In addition, our study cannot expand on further discussion related to the potential interference of the two material composition, since they were not directly compared.…”

The Influence of Bulk and Sonic Placement Techniques on Microleakage of Class II Cavities Restored with Different Resin Composites

“…38 Orlowski et al, explained that the most favorable gap results were attained by applying the Bulk-fill material with activating sonic handpiece. 39 Bulk-fill resin based composites were related to lesser stress levels, regardless of the material type, 40 but they did not eliminate it to the extent that they prevent its harmful effect on stability and seal at marginal interfaces. Higher translucency and light transmission properties of bulk-fill resin were enhanced, and modified by adding prepolymer shrinkage stress relievers, polymerization modulators chemically embedded in the center of polymerizable resin backbone, high-molecular weight base monomer to optimize flexibility and network structure and highly light-reactive photoinitiator system, 25 benzoyl germanium (Ivocerin) to enable rapid polymerization and greater depth of cure.…”

Effect of cavosurface angle beveling on the exposure angle of enamel prisms in different cavity sizes

“…Furthermore, the bevel removes the enamel aprismatic layer, which regularizes the enamel superficial layer, removing fragile prisms and improving the adhesion (Coelho- De-Souza et al, 2012;Van Meerbeek et al, 2011;Wang et al, 2018). The removal of weakened prisms is fundamental because they can fracture during the insertion/condensation of restorative material, masticatory function, as well as due to polymerization shrinkage/stress generated during cure of resin composites (Coelho-De-Souza et al, 2012;Rizzante et al, 2018;Rizzante et al, 2019).…”

“…Marginal leakage consists in gaps at this interface, allowing fluid and bacteria penetration, which can lead to restoration's failure and secondary caries (Giorgi et al, 2014;Soliman et al, 2016;Veloso et al, 2018). An adequate adhesive interface must resist to all stresses generated during polymerization shrinkage and masticatory function (Giorgi et al, 2014;Rizzante et al, 2018;Wang et al, 2018). The adhesion is obtained through micromechanical adhesion of the composite with the enamel prisms after acid etching (Mahn, Rousson, & Heintze, 2015;Wang et al, 2018), mainly when such prisms are perpendicular to the external surface (Carvalho, Santiago, Fernandes, Suh, & Pashley, 2000;Mizuno et al, 2015;Veneziani, 2017;Wang et al, 2018), as well as through hybrid layer formation in dentin (Frassetto et al, 2016).…”