INTRODUCTION: One of the main causes of composite replacement is its discoloration after prolonged exposure to the oral environment. In an effort to fulfill the patient esthetic desire, harmonize composite material have been introduced with limited studies regarding its esthetic properties and color stability. OBJECTIVES: To study the effect of coffee on the color stability of two nanohybrid composites with different monomers. MATERIALS AND METHODS: The resin composites tested were Venus diamond and Harmonize. A custom made disk-shaped mold (4mm thickness x 8 mm diameter) used to prepare 12 composite specimens. They were divided into 2 groups (n=6) according to the resin based composite that was used as follow: Group A restored with Urethane dimethacrylate based composite (Venus diamond, Heraeus Kulzer) and Group B restored with Bisphenol A diglycidil dimethacrylate based composite (Harmonize, Kerr). The specimens were finished using (Multi fluted tungsten carbide finishing bur for fifteen seconds) followed by polishing using (HiLuster, Kerr) polishing system. After that, the specimens were immersed in coffee solution for 7 days. Color difference ∆E was calculated before and after immersion of specimens for 48 hours and after 7 days using spectrophotometer (VITA easy shade). RESULTS: Mann Whitney U test showed significant difference in ∆E among composite restorative materials (p < 0.05). Venus diamond composite resin was found to be more stain-resistant than Harmonize composite resin after both 48 hours and 7 days. CONCLUSION: Different monomer compositions, immersion time and solution may have direct effect on the color stability of nanohybrid restorative materials.

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Background: The most frequently used monomer in commercial composite resins is bisphenol A glycidyl dimethacrylate. Bisphenol A glycidyl dimethacrylate free monomer and the long chain dimer acid based monomer were considered as an alternative method to improve mechanical and physical properties of composite resins. Objective: To study the surface roughness of different nanohybrid composites with different monomer compositions after finishing and polishing with different polishing systems. Materials and Methods: 72 composite disk specimens were prepared and divided into 3 groups (n=24) according to the resin composite that were used (harmonizekerr, venus diamondheraeuskulzer and n'duranceseptodont). Each group was subdivided into 4 subgroups (n=6) according to the polishing technique that was used (Jiffy natural universal wheelsultradent, sof-lex spiral wheels 3m espe, hilusterkerr or enhance system dentsply). Atomic force microscope was used to measure surface roughness. Results: There was statistical significant difference in surface roughness measuring among different n'durance, venus diamond and harmonize groups (Kruskal Wallis Test p<0.05). Post hock pairwise comparison revealed that venus diamond showed statistically significant higher surface roughness when compared with either n'durance and harmonize. Among the polishing systems, jiffy natural universal wheels produce the least surface roughness. Conclusion: Different monomer compositions may have direct effect on the final surface polish of the restorative materials. Clinical significance: The use of jiffy natural universal wheels may be found to result in the smoothest surface finish with the least clinical steps.