Can sterilization methods influence surface properties of resin composites? A purpose for previewing bias in laboratory bacterial adhesion tests

This study aimed to evaluate the influence of sterilization methods on conventional and bulk-fill resin composites' (BFRCs) surface properties in an attempt to preview bias in laboratory bacterial adhesion tests. Two regular viscosity conventional resin composites [Filtek Z350 XT™ (Z350) and IPS Empress Direct™ (ED)] and two regular viscosity BFRCs [Filtek Bulk Fill™ (FILT) and Tetric N-Ceram Bulk Fill IVA™ (TBF)] were used. The materials were characterized by Scanning Electron Microscopy (SEM), surface roughness (SR), and wettability (W) after sterilization with hydrogen peroxide gas plasma (HPGP) and steam sterilization (SS). Nonsterilized samples served as a control group (n = 5). Statistical analysis was performed using two-way analysis of variance (ANOVA) and Tukey post hoc test (p <  0.05). For SR, there were no statistically significant differences among the groups (p > .05). SS method decreased the contact angle for FILT and Z350 (p < .01). The SS promoted more exposition of filler particles, while the HPGP method did not alter the tested materials' morphology. Therefore, sterilization methods affected the resin composites tested selectively. HPGP seems to be the most recommended method to sterilize the tested resin composites before laboratory bacterial adhesion tests.

Bonding performance and mechanical properties of flowable bulk-fill and traditional composites in high c-factor cavity models

Objectives:

The aim of this study is to evaluate bond strength (BS), shrinkage stress (SS), flexural strength (FS), and elastic modulus (E) of three flowable bulk fill in comparison with conventional composites.

Materials and Methods:

Three bulk fill (Filtek Bulk Fill Flow, Surefil SDR, X-tra Base) and three conventional composites (Filtek Z250 XT, Grandioso, Dentsply TPH3) were used. For BS, conical cavities (n = 10) were prepared in bovine dentine and restored with materials and were analyzed through push-out test in a universal testing machine (UTM). For FS/EM, 60 (n = 10) bar specimens (7 mm × 2 mm × 1 mm) were prepared and evaluated with a UTM. SS was measured in UTM coupled to an extensometer (n = 5). The data were statistically evaluated using one-way ANOVA/Tukey tests (P < 0.05).

Results:

Conventional composites showed higher E when compared to bulk-fill composites. Regarding FS, they showed similar results, except for (XBF) Xtra Bulk Fill that was inferior. SS and BS of bulk-fill composites were significantly lower and higher than conventional composites, respectively, except for XBF, which showed similar BS to conventional ones.

Conclusions:

Flowable bulk-fill composites, except XBF, showed higher BS, lower SS, similar FS, and lower E when compared to conventional ones.

Effects of ZnO/TiO2 nanoparticle and TiO2 nanotube additions to dense polycrystalline hydroxyapatite bioceramic from bovine bones

OBJECTIVES

A bovine dense hydroxyapatite ceramic (HA) was produced as new biomaterial, however, the production of a material with consistently high flexural strength remains challenging. The objective of this study was to evaluate the effects of ZnO nanoparticles, TiO₂ nanoparticles, and TiO₂ nanotubes (1%, 2%, and 5% by weight) on the microstructure and flexural strength of a bovine dense hydroxyapatite ceramic (HA).

METHODS

Discs (Ø=12.5mm; thickness=1.3mm) were prepared and subjected to X-ray diffraction (XRD), and observation with a field emission scanning electron microscope (FE-SEM), biaxial flexural strength (BFS) testing, and Vickers hardness (VH) testing. The BFS and VH data were subjected to ANOVA and Tukey post-hoc tests (α=0.05) and Weibull analysis.

RESULTS

The XRD showed that the addition of nanomaterials caused the formation of a secondary phase when 5% of the ZnO nanoparticles was used, or when all percentages of the TiO₂ nanoparticles/nanotubes were used, and the HA crystallographic planes were maintained. Differences were not observed between the higher BFS values obtained with pure HA and those obtained with the 5% addition of TiO₂ nanoparticles. However, the results were different compared with the other groups (α=0.05). The results obtained by Weibull analysis revealed that the 1%, 2%, and 5% addition of TiO₂ nanotubes, and the 1% and 2% addition of TiO₂ nanoparticles decreased the HA characteristic strength (σ₀), while the Weibull modulus (m) increased when 5% of TiO₂ nanoparticles, 1% and 2% of ZnO nanoparticles, and 2% of TiO₂ nanoparticles were added, but with no statistical difference from the pure HA. The 5% addition of ZnO₂ nanoparticles decreased the σ₀ without changing m. Moreover, the 5% addition of TiO₂ nanoparticles resulted in an m closest to that of pure HA. Regarding the VH results, the blend of HA with 1% and 2% addition of TiO₂ nanoparticles exhibited the higher values, which were similar between the different addition ratios (p=0.102). Moreover, the addition of 5% TiO₂ nanoparticles resulted in higher value compared with pure HA.

SIGNIFICANCE

This study demonstrated that the HA blend with 5% of TiO₂ nanoparticles has the greatest potential as a bovine HA dense bioceramic reinforcement.