Abstract
(1) Background: currently, the advantages of bulk-fill resin composite and high-viscosity glass ionomer materials have increased their use in dentistry; accordingly, their mechanical, surface, and optical properties have become more important. This study aimed to evaluate the mechanical, surface, and optical properties of three different restorative materials (a high-viscosity bulk-fill resin composite (TNC), a flowable bulk-fill resin composite (EBF), and a high-viscosity glass ionomer (FIX)) after application using different techniques (control, heat application, and ultrasonic activation). (2) Methods: specimens were prepared to assess the color stability and surface roughness (n = 12). The specimens were immersed in two different solutions for 14 days. For the compressive strength test, specimens were prepared using a Teflon mold (n = 12). (3) Results: among the specimens applied according to the manufacturer's instructions and immersed in distilled water, it was observed that the surface roughness values of FIX on the 7th day were statistically significantly higher than the other materials (p < 0.05). The compressive strength values of EBF applied using ultrasonic activation were significantly lower than those of EBF applied using the other techniques (p < 0.05). (4) Conclusions: coffee can negatively affect the color stability of restorative materials, but discoloration may vary depending on differences in the content of the material. All materials evaluated in this study exhibited clinically acceptable surface roughness values. It can be concluded that flowable bulk-fill resin composite is the most durable material in terms of compressive strength, so it can be used in the restoration of posterior teeth, especially those exposed to intensive stress.