We aimed to evaluate the color stability of bulk-fill and conventional composite resin with respect to thickness and storage media. Twenty specimens of a conventional composite resin (6 mm diameter and 2 mm thick) and 40 specimens of the bulk-fill Tetric EvoCeram composite resin at two different thicknesses (6 mm diameter and 2 mm thick or 4 mm thick, n = 20) were prepared. The specimens were stored in distilled water during the study period (28 d). Half of the specimens were remained in distilled water and the other half were immersed in coffee solution 20 min/d and kept in distilled water between the cycles. Color changes (ΔE) were measured using the CIE L ⁎ a ⁎ b ⁎ color space and a digital imaging system at 1, 7, 14, and 28 days of storage. Data were analyzed using Two-way ANOVA and Tukey's HSD post hoc test (P < 0.05). Composite resins showed significant increase in color changes by time (bulk-fill > conventional; P < 0.001). Coffee exhibited significantly more staining susceptibility than that of distilled water (P < 0.001). There was greater color changes with increasing the increment thickness, which was significant at 14 (P < 0.001) and 28 d (P < 0.01). Color change of bulk-fill composite resin was greater than that of the conventional one after coffee staining and is also a function of increment thicknesses.
Aim and Background: Restoration of severely damaged primary anterior teeth are deemed as serious challenges for pediatric dentists. The aim of this study was to evaluate the fracture resistance of primary canines restored with flowable or packable composite resin posts. Material and Methods This study was conducted on a group of extracted primary canines. After cutting the coronal section, standard pulpectomy was performed and root canals were filled with ZOE paste leaving 3 mm coronal root space. A liner was placed above the root canal filling as a barrier. Samples were then randomly divided into two groups of fifteen. Both groups, received etch, bond, then in group I Core Flo Composite resin placement into canal, in group II, post shaping using designated packable composite resin and inserted into the canal. Followed by Core buildup and Crown reconstruction using Z250 composite resin. Samples were mounted at 148 ° angle on the acrylic blocks and stored in de-ionized water for 72 hours. Fracture resistance was measured using Universal Testing Machine. Data analysis were performed using independent t-test. Chi- square test were also employed to assess the type of fracture within groups. Results The mean fracture resistance in the group I was 830.31(+/-328.69N) and 803.09(+/-326.45N) in group II. Moreover, statistical analyses of the results showed no significant difference between the mean values of the fracture resistance (p-value=0.822) of groups as well as the type of fracture (p-value=0.79) between groups. Conclusion The ease of use and proper adhesion of the Core Flo composite resin, seems to help its use in the reconstruction of severely destructed anterior primary teeth.
<p>Polymer networks are considered to be largely affected by water and chemical absorption from environment. <strong>Objective: </strong>The aim of this study was to evaluate the hygroscopic expansion of bulk-fill composite. <strong>Material and Methods:</strong> Fifteen disks (5 in each group) with different thickness(4mm/2mm) of Tetric N-Ceram Bulk Fill composite(TB) and Tetric N-Ceram composite(TN) were made according to the manufacturer’s instruction and stored in deionized water. The length of each specimen was recorded using a digital micrometer at baseline and at the end of 24 h, 1, 2, 4, 12 weeks intervals. Repeated measure ANOVA and Tukey HSD were used to determine the effect of variables. At 12 weeks, the mean hygroscopic expansion after water immersion ranged between 0. 33±0.09mm for TN to 0.41±0.07mm for TB with 2mm thickness. Repeated measure ANOVA revealed a significant increase in hygroscopic expansion over time (P<0.05). <strong>Results: </strong>The results indicated that at 24hours and 2weeks there was a significant difference among TN and TBwith 4mm thickness (p=0.007 and p=0.023, respectively). The other differences were not significant.<strong> </strong>Hygroscopic expansion affected by the type of composite and the passing of time. <strong>Conclusion: </strong>The results showed that the time taken to reach stabilization in hygroscopic expansion was shorter for TN in comparison with TB. For 2mm thickness equilibrium was attained earlier.</p><p><strong> </strong></p><p><strong>Keywords</strong></p><p>Water; Expansion; Composites; Polymerization; Bulk-fill.</p>
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