Interfacial Properties and Bottom/Top Hardness Ratio Produced by Bulk Fill Composites in Dentin Cavities

Abstract

The aim of this study was to evaluate the bond strength, bottom/top hardness ratio, marginal adaptation, and interfacial nanoleakage of regular viscosity bulk fill composites (RVBFC) and regular viscosity traditional composites (RVTC). Two RVBFC (Filtek Bulk Fill and Aura Bulk Fill) and two RVTC (Filtek Z250XT and Aura) were assessed. Forty conical cavities (4.8×2.8×4.0) were prepared in bovine dentin and restored with composites (n=10). After 24h in water, marginal adaptation was evaluated by staining with a caries detector. The top and bottom surfaces of the conical restorations were stained for five seconds and the gap percentage in the composite/dentin interface was determined using digital images on a measurement program (ImageTool). The Vickers microhardness was measured and the bottom/top microhardness ratio (B/T) was determined. Push-out bond strength test was performed in a universal testing machine (0.5mm/min) and failure modes were evaluated in a stereomicroscope (20×). Other specimens (n=3) were produced for interfacial nanoleakage evaluation. Data were analyzed using one and two-way ANOVA and Tukey’s test (α=0.05). The gap percentage was higher in the bottom compared to the top. The B/T ratio of the Aura Bulk Fill was statistically lower than other composites. Push-out bond strength were similar among composites. The RVBFC presented lower nanoleakage than the RVTC in the bottom of the conical restoration and there was no difference among the materials in the top surfaces. In conclusion, Filtek Bulk Fill performed better than Aura Bulk Fill regarding the analyzed properties.

Physico-mechanical properties of aesthetic resin composites

“…Additionally, the current review of the published literature has shown that a bottom/top ratio ≥ 0.8 was considered as clinically acceptable [40]. In the present study, HM showed signi cantly the highest VHN properties, whereas signi cantly the lowest hardness ratio (bottom/top ratio = 0.87, p < 0.05), which indicated its relatively weaker degree of polymerization, nevertheless, it is acceptable in clinical situations.…”

Dual-cured adhesive system improves adhesive properties of dentin cavities restored with a bulk-fill resin composite

“…Figure 1 shows a schematic representation of the specimens' preparation and analyses performed. Sixty-eight bovine incisors without enamel cracks or structural defects were selected for dental preparations according to a previously described method 10,11 .…”

“…BS was evaluated by the push-out method in a universal testing machine (EMIC DL 2000, São José dos Pinhais, PR, Brazil) as previously reported 10,11 . An acrylic device with a central hole was adapted on the machine base where specimens were placed with its larger surface facing down.…”

“…The smaller surface was pushed by a cylindrical plunger (1-mm diameter) with a compressive force (0.5 mm/min) until failure. Data were obtained in N and transformed in MPa using the following equation (II), in which "N" is the bond strength in Newton, "R" is the larger surface radius, and "r" is the smaller surface radius and "h" is the sample height 10,11 .…”

Bottom/top hardness ratio and dentin bonding stability of conventional and bulk-fill resin composites

“…Mechanical properties such as the depth of cure are related to resin composites' dentin bonding performance [3][4][5] . An insufficient monomer conversion in the bottom of resin composite restorations can compromise their strength and durability due to the material's hydrolytic degradation 6,7 .Thus, regardless of the resin composite type used, a well-polymerized material is required, which can be accessed using the bottom/top hardness ratio [3][4][5] .…”