The aim of this in vitro study is to investigate the effects of acidic beverages on the discoloration of bulk-fill composites with different viscosities. 144 disc-shaped specimens (8mm diameter × 2mm thick) were prepared from four different composite resins including a nanohybrid (Filtek Ultimate), two packable bulk-fill (Filtek Bulk Fill, Tetric N Ceram Bulk Fill), and a flowable bulk-fill composite (Tetric N Flow Bulk Fill). The specimens of each group were divided into 3 subgroups and submerged in distilled water, orange juice and coke (n=12). Color difference (∆E) were measured using CIELab color space and a compact spectrophotometer (VITA Easyshade) at baseline and after 30 days of immersion. Data were analyzed using two-way ANOVA and Tukey's HSD post-hoc tests (P<0.05). Two-way ANOVA revealed that both material type and staining solution significantly influenced ∆E values (P<0.001). Immersion in orange juice resulted in greater and significant discoloration over time in comparison to distilled water and coke (P<0.05). Tetric N Ceram (∆E=7.0) and Tetric N Flow (∆E=7.7) bulk-fill restoratives showed highest color change values after 30 days of immersion in orange juice. This study suggests that a discoloration above the clinically acceptable threshold (∆E>2.7) was observed for all bulk-fill composites tested. It can be speculated that orange juice has a more negative effect on the color stability compared to coke. Additionally, flowable bulk-fill composite was more prone to discoloration than condensable bulk-fill composites.
This study aimed to evaluate cytotoxic effects of various irrigation solutions used in regenerative endodontic treatments (RETs) on mesenchymal stem cells, and further examine the long-term effect of hypochlorous acid (HOCl) on the cell viability and alkaline phosphatase (ALP) activity. Stem cells were exposed to various concentrations of NaOCl, EDTA, chlorhexidine (CHX), etidronic acid (HEDP)/NaOCl combination and HOCl. HOCl was tested for its effects on ALP activity up to 21 days. Additionally, cell viability was measured fluorescently using calcein AM. The most cytotoxic irrigant was CHX even with the lowest concentration. NaOCl and HEDP/NaOCl with 1:100 dilution decreased viability to around 40%. HOCl showed the lowest cytotoxicity among all tested irrigants. HOCl also showed no significant reduction in ALP activity compared with the controls. The cytotoxicity of endodontic irrigants was time and concentration dependent. HOCl demonstrated promising results regarding viability and ALP activity, since RETs require host stem cell survival.
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