Color Stability and Flexural Strength of Temporary Prosthetic Materials under the Influence of Staining Substances

Aim: To evaluate the color stability and flexural strength of temporary resins under the influence of staining substances.Materials and methods: A total of 300 round specimens (10 mm diameter × 2 mm thickness) in A2 color were prepared and divided into five groups: Acrylic Resin: Group I (Refine Bright® Kota); bis-acryl Resin: Group II (Protemp®); group III (Structur®); group IV (Systemp®); and group V composite resin (Z350®).After standardized polishing, each group was divided into four subgroups (n = 15), which were immersed in coffee, cola-like soft drink, black tea, or distilled water for 7 days.Then, each resin was evaluated for staining (Vita Easyshade) compared to distilled water.Surface roughness (Ra, Sa) was measured by optical profilometry (CCI MP) to evaluate the correlation between smoothness and staining.The samples were cut into bars of 10 × 2 × 2 mm for flexural strength (Instron 3365) evaluation.The results were subjected to statistical analysis (two-way ANOVA and Tukey post-test; p < 0.05).Results: Group I showed the least staining, followed by bis-acryl resins and group V. Coffee was the strongest staining substance, followed by black tea.Bis-acryl resins showed higher surface roughness (group III, group IV, and group II in decreasing sequence), and no direct correlation with staining was found.Flexural strength testing revealed significant differences between materials (group III > group II = group IV > group V = group I), but staining had no effect. Conclusion:The study shows that among the tested temporary materials, acrylic resin has the highest color stability, while bis-acryl resin has the highest resistance.Group III showed better balance results between color stability and resistance.Clinical significance: These findings highlight materials that should balance esthetic stability and mechanical performance in provisional restorations.