In vitro attrition wear resistance of four types of paste-like bulk-fill composite resins.

BACKGROUND: Recently, the application of bulk-fill composite resins has increased significantly. Attrition wear and the consequently increased surface roughness of composite resins are among the causes of restoration failure in the posterior teeth. This study aimed to compare the attrition wear and surface roughness of four types of bulk-fill composite resins compared to a conventional composite resin. METHODS: EverX-Posterior, X-tra fil, SonicFill 2, and Filtek Bulk-Fill composites (bulk-fill) and Z250 composite (conventional resin composite) were evaluated. Thirty cylindrical specimens (n = 6) were weighed and monitored for 24 h until their weight was stabilized. The primary surface roughness of the specimens was measured by a profilometer. The specimens were then subjected to attrition wear in a chewing simulator. Next, the specimens were weighed, and the surface roughness was measured again. Data were analyzed by one-way ANOVA and Tukey's post-hoc test at P < 0.05 significance level. RESULTS: According to one-way ANOVA, the difference in weight loss was significant among the groups (P = 0.004) but the difference in surface roughness of the groups was not significant after the attrition wear (P > 0.05). Tukey's post-hoc test showed that the weight loss of bulk-fill composites was not significantly different from that of Z250 conventional composite after the attrition wear (P > 0.05). CONCLUSION: Within the limitations of this study, it appears that the tested bulk-fill composite resins are comparable to the conventional composite regarding their attrition wear, increased surface roughness, and weight loss.

Evaluation of Wear Properties of Four Bulk-Fill Composites: Attrition, Erosion, and Abrasion.

PURPOSE: Wear and increased surface roughness are among the reasons for failure of posterior composite restorations. Considering the widespread use of bulk-fill composites in the posterior region, information about their wear resistance is imperative. The aim of this study was to compare the wear and surface roughness of four bulk-fill composite resins with a conventional composite. METHODS: Thirty composite discs (4 mm × 10 mm) were fabricated from EverX Posterior (GC), X-tra fil (Voco), Filtek Bulk-Fill Posterior (3M, USA), SonicFill 2 (Kerr), and Z250 (3M) composites. The baseline weight and surface roughness of specimens were measured. For the assessment of the attrition wear, the specimens were placed in a chewing simulator (Mechatronik). pH cycling was performed to erode the composite discs. They were then placed in a tooth brushing simulator machine (Dorsa) for abrasion wear. Finally, the weight and surface roughness of the specimens were measured. Data were compared using one-way ANOVA (alpha ≤ 0.05). RESULTS: One-way ANOVA showed that the mean weight changes were significant after attrition, abrasion, and erosion (P = 0.019), but changes in surface roughness were not significant (P ≥ 0.05). The results of Tukey's test showed no significant difference between the bulk-fill composites and Z250 regarding weight loss (P ≥ 0.05), but the weight loss of X-tra fil was significantly greater than that of EverX (P = 0.007) and Filtek Bulk-Fill (P = 0.005). CONCLUSIONS: Considering the limitations of this study, it appears that the wear and surface roughness of bulk-fill composites are within the acceptable range and are not different from those of a conventional composite.

Cytotoxic Effect of Addition of Different Concentrations of Nanohydroxyapatite to Resin Modified and Conventional Glass Ionomer Cements on L929 Murine Fibroblasts.

Objectives: In this study we assessed the cytotoxic effect of nanohydroxyapatite (NHA) incorporated into resin modified and conventional glass ionomer cements (RMGICs and CGICs) on L929 murine fibroblasts. Materials and Methods: In this in vitro study, 0wt%, 1wt%, 2wt%, 5wt%, 7wt% and 10wt% concentrations of NHA were added to Fuji II LC RMGIC and Fuji IX CGIC powders. Eighteen samples (5×3mm) were fabricated from each type of glass ionomer, in six experimental groups (n=3): CG0, CG1, CG2, CG5, CG7, CG10, RMG0, RMG1, RMG2, RMG5, RMG7, and RMG10. Samples were incubated for 72h. The overlaying solution was removed and added to L929 fibroblasts. The methyl thiazolyl tetrazolium bromide (MTT) assay was performed at 24, 48 and 72h. The wavelength was read by a spectrophotometer. Data were analyzed by ANOVA and Tukey's test. Results: There was no significant difference in cytotoxicity of the two types of glass ionomers, with and without NHA, except for CG0 and RMG0 groups after 72h. RMG0 group was significantly more cytotoxic than the CG0 group (P<0.05). In CG groups during the first 24h, the cytotoxicity of CG5 and CG7 groups was significantly higher than that of CG1; while, there was no significant difference between the RMG groups. Cytotoxicity significantly decreased in all groups after 24h (P<0.05). Conclusion: Incorporation of NHA into Fuji II LC RMGIC and Fuji IX CGIC did not affect their biocompatibility and therefore its addition to these materials can provide favorable biological properties, especially considering its beneficial effects on the other properties of GICs.