Background and Aim: Discoloration is among the most common problems of composite restorations. Color change over time compromises the main advantage of composite resins namely their high esthetics. In such cases, the restoration needs to be replaced. .The aim of this in-vitro study was to evaluate the effect of accelerated artificial aging (AAA) on the color stability of three composite resins (Filtek Z250, Filtek Z250XT, and Filtek Supreme). Materials and Methods: In this experimental study, 7 composite specimens with equal dimensions were fabricated of each composite resin. The initial color of specimens was measured using a spectroradiometer according to the CIE L*a*b* system. The specimens were then submitted to AAA for 384h and underwent color assessment again. Before and after aging, the surface roughness of one specimen from each group was determined by Atomic Force Microscopy (AFM). The obtained color parameters were analyzed by one-way ANOVA and Tukey’s test. Results: The color change of Filtek Z250 was significantly lower than that of Filtek Z250XT and Filtek Supreme (P≤0.05). No statistically significant differences were found between Z250XT and Supreme in this respect (P>0.05 ). Conclusion: All composite resins showed color change above the clinically acceptable threshold. Z250 microhybrid composite was more color stable than nano-composites (Z250XT and Supreme). AAA increased the surface roughness in all groups but it was within the clinically acceptable range.

Introduction: Discoloration is one of the most common reasons for replacement of resin composites. The purpose of this study was to compare the color stability of three Methacrylate-based Resin Composites (Filtek Z250, Filtek Z250x, Filtek Z350xt) with Silorane-based Resin Composites (Filtek P90) after Accelerated Artificial Aging (AAA).Materials & Methods: In this in vitro study 56 composite discs were prepared (N=14). CIE L*a*b* parameters of each specimen were measured by a reflectance spectrophotometer after 24h and 384 h of AAA. Then Color change (DE) of each composite was calculated. Data were analyzed by one way ANOVA, Tukey and paired t-test at the significance level of 0.05.Results: DE values of Filtek Z250, Filtek Z250x, Filtek Z350xt and Filtek P90 were 7.77, 5.86, 8.95 and 8, respectively. One way ANOVA demonstrated a significant difference between DE values of composites (P˂0.001). Tukey’s test revealed that DE value of Filtek Z250xt was significantly lower than those of other composites (P˂0.05).Conclusion: Silorane and methacrylate based composites showed a color change more than the clinically acceptable level (DE˃3.3) after AAA. Filtek Z250xt showed the lowest color change and other composites showed relatively similar color change.

The Artificial Bee Colony (ABC) Algorithm is a sophisticated optimization technique that is inspired by the intelligent behaviors of honey bee swarms. These behaviors, such as foraging and communication within complex social structures, serve as the foundation for the algorithm's effectiveness. In this paper, the ABC algorithm is utilized to optimize the design of reinforced cantilever concrete retaining walls, with the goal of minimizing both cost and weight. The results are compared to existing literature, demonstrating the success of the ABC algorithm in achieving the objectives. Furthermore, a comparison is conducted between the optimized design and a conventional manual design, revealing a significant reduction in cost and weight through optimization. Additionally, two types of reinforced concrete cantilever retaining walls-a T-shape wall with variable stem thickness and a standard T-shape wall-are presented and compared, considering their differing variables and constraints. These comparisons are made for two objective functions: the cost and weight of the wall. To further investigate the impact of initial parameters, such as the unit weight of soil and stem height, a sensitivity analysis is conducted. The robustness of the ABC algorithm in optimizing the cost and weight of reinforced concrete cantilever retaining walls is demonstrated by the results.